Patent Application
20130301252
Light emitting diode (LED) lighting systems are becoming more prevalent as replacements for older lighting systems. LED systems are an example of solid state lighting (SSL) and have advantages over traditional lighting solutions such as incandescent and fluorescent lighting because they use less energy, are more durable, operate longer, can be combined in multi-color arrays that can be controlled to deliver virtually any color light, and generally contain no lead or mercury. A solid-state lighting system may take the form of a lighting unit, light fixture, light bulb, or a “lamp.”
An LED lighting system may include, for example, a packaged light emitting device including one or more light emitting diodes (LEDs), which may include inorganic LEDs, which may include semiconductor layers forming p-n junctions and/or organic LEDs (OLEDs), which may include organic light emission layers. Light perceived as white or near-white may be generated by a combination of red, green, and blue (“RGB”) LEDs. Output color of such a device may be altered by separately adjusting supply of current to the red, green, and blue LEDs. Another method for generating white or near-white light is by using a lumiphor such as a phosphor. Still another approach for producing white light is to stimulate phosphors or dyes of multiple colors with an LED source. Many other approaches can be taken.
An LED lamp may be made with a form factor that allows it to replace a standard incandescent bulb, or any of various types of fluorescent lamps. LED lamps often include some type of optical element or elements to allow for localized mixing of colors, collimate light, or provide a particular light pattern. Sometimes the optical element also serves as an envelope or enclosure for the electronics and or the LEDs in the lamp.
Since, ideally, an LED lamp designed as a replacement for a traditional incandescent or fluorescent light source needs to be self-contained; a power supply is included in the lamp structure along with the LEDs or LED packages and the optical components. A heatsink is also often needed to cool the LEDs and/or power supply in order to maintain appropriate operating temperature. The power supply and especially the heatsink can often hinder some of the light coming from the LEDs or limit LED placement. Depending on the type of traditional bulb for which the solid-state lamp is intended as a replacement, this limitation can cause the solid-state lamp to emit light in a pattern that is substantially different than the light pattern produced by the traditional light bulb that it is intended to replace.
Traditional incandescent bulbs typically comprise a filament supported on support wires where the support wires are mounted on a glass stem that is fused to the bulb. Wires are run through the stem to provide electric current from the bulb's base to the filament. The stem is fused to the enclosure using heat to melt the glass. In traditional incandescent bulbs fusing the stem to the enclosure does not present a particular problem because the heat generated during the fusing operation does not adversely affect the bulb components. However, such an arrangement has been considered to be unsuitable for LED lamp designs because the heat generated during the manufacturing process is known to have an adverse impact on the LEDs. Heat such as applied during the fusing operation can degrade the performance of the LEDs in use such as by substantially shortening LED life. The heat may also affect the solder connection between the LEDs and the PCB, base or other submount where the LEDs may loosen or become dislodged from the PCB, base or other submount. Thus, traditional manufacturing processes and structures have been considered wholly unsuitable for LED based lighting technologies.
In one embodiment a lamp comprises an enclosure being at least partially optically transmissive. A board supports a power supply for the lamp and is located in the enclosure. An LED array is disposed in the optically transmissive enclosure and is mounted to the board and is operable to emit light when energized through an electrical connection. A gas is contained in the enclosure to provide thermal coupling to the LED array. The LED array comprises a plurality of LEDs mounted on a submount formed to have a three dimensional shape. The board is electrically coupled to the LED array and the submount is thermally coupled to the gas for dissipating heat from the plurality of LEDs.
In some embodiments, the submount may be bendable. The board may be supported in the enclosure by conductors that form part of the electrical connection. The submount may be formed with a first connector and the board may be formed with a second connector where the first connector engages the second connector to secure the submount to the board. The first connector may comprise one of a female connector and a male connector and the second connector may comprise another one of a male connector and a female connector. The first connector may comprise one of a slot and a tab and the second connector may comprise another one of a tab and a slot. The first connector may comprise a slot and a resilient tab adjacent the slot and the second connector may comprise a tab where the resilient tab is deformed by the tab to create a pressure force on the tab. A first electrical contact may be formed on the board that is electrically coupled to a second electrical contact on the submount. The first electrical contact may be electrically coupled to the second electrical contact at a soldered joint. The submount may comprise heat conducting portions that provide suitable surface area and allow air circulation such that heat generated by the plurality of LEDs is transferred to the gas. The heat conducting portions may comprise electrically inactive areas. The submount may comprise a circuitized submount and the plurality of LEDs may be mounted directly to the circuitized submount. The submount may comprise a flex circuit comprised of a thermally conductive material. The flex circuit may be a single sided flex circuit. The flex circuit may be formed into a three-dimensional shape providing a surface for supporting the plurality of LEDs. The plurality of LEDs may comprise surface mount LEDs. The flex circuit may be formed into a generally cylindrical shape having vertical surfaces that support the plurality of LEDs. The flex circuit may constitute at least approximately 90% thermally conductive material. The flex circuit may constitute approximately 99% thermally conductive material. The flex circuit may be flooded with copper to provide enough heat conductive material that heat generated by the plurality of LEDs is dissipated to the gas in the enclosure such that the performance of the LEDs is not degraded. Portions of the flex circuit may form heat conducting elements that provide suitable surface area and allow air circulation such that heat generated by the LEDs is transferred to the gas. An aluminum stiffener may be attached to the back of the flex circuit. The submount may comprise a lead frame where the lead frame supports the plurality of LEDs and forms part of the electrical connection between the board and the plurality of LEDs. The lead frame may be made of a thermally and electrically conductive material. The lead frame may be formed into an electrical circuit. The plurality of LEDs may be populated on the lead frame and reflow soldered to the electrical pads on the lead frame at LED solder joints where the LED solder joints mechanically hold the lead frame circuit together. The lead frame may comprise portions that are provided to increase heat transfer between the lead frame and the gas, the portions being electrically isolated from one another. The submount may not include electrical circuitry such that the submount only physically supports the plurality of LEDs and provides a heat sink for dissipating heat to the gas. The plurality of LEDs may comprise top side contact pads that are electrically coupled by wire bonds. The wire bonds may be of sufficient length that the wire bonds accommodate bending of the submount without breaking. The gas may comprise helium and/or hydrogen.
a-56d show additional embodiments of portions of the lamp of the invention.
a-58b show additional embodiments of portions of the lamp of the invention.
a is a perspective view of the embodiment of the lamp of
b is a partial exploded view of the embodiment of the lamp of
a is a perspective view of the embodiment of the lamp of
c, 60d and 60e are top side and bottom views of the embodiment of the lamp of
Embodiments of the present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout.
It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
It will be understood that when an element such as a layer, region or substrate is referred to as being “on” or extending “onto” another element, it can be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or extending “directly onto” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present.
Relative terms such as “below” or “above” or “upper” or “lower” or “horizontal” or “vertical” may be used herein to describe a relationship of one element, layer or region to another element, layer or region as illustrated in the figures. It will be understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” “comprising,” “includes” and/or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Unless otherwise expressly stated, comparative, quantitative terms such as “less” and “greater”, are intended to encompass the concept of equality. As an example, “less” can mean not only “less” in the strictest mathematical sense, but also, “less than or equal to.”
The terms “LED” and “LED device” as used herein may refer to any solid-state light emitter. The terms “solid state light emitter” or “solid state emitter” may include a light emitting diode, laser diode, organic light emitting diode, and/or other semiconductor device which includes one or more semiconductor layers, which may include silicon, silicon carbide, gallium nitride and/or other semiconductor materials, a substrate which may include sapphire, silicon, silicon carbide and/or other microelectronic substrates, and one or more contact layers which may include metal and/or other conductive materials. A solid-state lighting device produces light (ultraviolet, visible, or infrared) by exciting electrons across the band gap between a conduction band and a valence band of a semiconductor active (light-emitting) layer, with the electron transition generating light at a wavelength that depends on the band gap. Thus, the color (wavelength) of the light emitted by a solid-state emitter depends on the materials of the active layers thereof. In various embodiments, solid-state light emitters may have peak wavelengths in the visible range and/or be used in combination with lumiphoric materials having peak wavelengths in the visible range. Multiple solid state light emitters and/or multiple lumiphoric materials (i.e., in combination with at least one solid state light emitter) may be used in a single device, such as to produce light perceived as white or near white in character. In certain embodiments, the aggregated output of multiple solid-state light emitters and/or lumiphoric materials may generate warm white light output having a color temperature range of from about 2200K to about 6000K.
Solid state light emitters may be used individually or in combination with one or more lumiphoric materials (e.g., phosphors, scintillators, lumiphoric inks) and/or optical elements to generate light at a peak wavelength, or of at least one desired perceived color (including combinations of colors that may be perceived as white). Inclusion of lumiphoric (also called ‘luminescent’) materials in lighting devices as described herein may be accomplished by direct coating on solid state light emitter, adding such materials to encapsulants, adding such materials to lenses, by embedding or dispersing such materials within lumiphor support elements, and/or coating such materials on lumiphor support elements. Other materials, such as light scattering elements (e.g., particles) and/or index matching materials, may be associated with a lumiphor, a lumiphor binding medium, or a lumiphor support element that may be spatially segregated from a solid state emitter.
Embodiments of the present invention provide a solid-state lamp with centralized light emitters, more specifically, LEDs. Multiple LEDs can be used together, forming an LED array. The LEDs can be mounted on or fixed within the lamp in various ways. In at least some example embodiments, a submount is used. In some embodiments, the submount is light transmissive. A light transmissive submount can be translucent, diffusive, transparent or semi-transparent. The submount can have two or more sides, and LEDs can be included on both or all sides. The centralized nature and minimal and/or light transmissive mechanical support of the LEDs allows the LEDs to be configured near the central portion of the structural envelope of the lamp. In some example embodiments, a gas provides thermal coupling to the LED array in order to cool the LEDs. However, the light transmissive submount can be used with a liquid, a heatsink, or another thermic constituent. Since the LED array can be configured in some embodiments to reside centrally within the structural envelope of the lamp, a lamp can be constructed so that the light pattern is not adversely affected by the presence of a heat sink and/or mounting hardware, or by having to locate the LEDs close to the base of the lamp. If an optically transmissive submount is used, light can pass through the submount making for a more even light distribution pattern in some embodiments. It should also be noted that the term “lamp” is meant to encompass not only a solid-state replacement for a traditional incandescent bulb as illustrated herein, but also replacements for fluorescent bulbs, replacements for complete fixtures, and any type of light fixture that may be custom designed as a solid state fixture for mounting on walls, in or on ceilings, on posts, and/or on vehicles.
Still referring to
Still referring to
It should be noted that if a lamp like lamp 200 in
Any of various gasses can be used to provide an embodiment of the invention in which an LED lamp includes gas as a thermic constituent. A combination of gasses can be used. Examples include all those that have been discussed thus far, helium, hydrogen, and additional component gasses, including a chlorofluorocarbon, a hydrochlorofluorocarbon, difluoromethane and pentafluoroethane. Gasses with a thermal conductivity in milliwatts per meter Kelvin (mW/m-K) of from about 45 to about 180 can be made to work well. For purposes of this disclosure, thermal conductivities are given at standard temperature and pressure (STP). Air, Nitrogen and Oxygen have a thermal conductivity of about 26, Helium gas has a thermal conductivity of about 156, and hydrogen gas has a thermal conductivity of about 186, and neon gas has a thermal conductivity of about 49 at 300K. It is to be understood that thermal conductivity values of gasses may change at different pressures and temperatures. Gasses can be used with an embodiment of the invention where the gas has a thermal conductivity of at least about 45 mW/m-K, least about 60 mW/m-K, at least about 70 mW/m-K, least about 100 mW/m-K, at least about 150 mW/m-K, from about 60 to about 180 mW/m-K, or from about 70 to about 150 mW/m-K.
A gas used for cooling in example embodiments of the invention can be pressurized, either negatively or positively. In fact, a gas inserted in the enclosure or internal optical envelope at atmospheric pressure during manufacturing may end up at a slight negative pressure once the lamp is sealed. Under pressure, the thermal resistance of the gas may drop, enhancing cooling properties. The gas inside a lamp according to example embodiments of the invention may be at any pressure from about 0.5 to about 10 atmospheres. It may be at a pressure from about 0.8 to about 1.2 atmospheres, at a pressure of about 2 atmospheres, or at a pressure of about 3 atmospheres. The gas pressure may also range from about 0.8 to about 4 atmospheres.
It should also be noted that a gas used for cooling a lamp need not be a gas at all times. Materials which change phase can be used and the phase change can provide additional cooling. For example, at appropriate pressures, alcohol or water could be used in place of or in addition to other gasses. Porous substrates, envelopes, or enclosure can be used that act as a wick. The diffuser on the lamp can also act as the wick.
The inventors of the present invention have determined that in a sealed environment such as described herein, in some embodiments operating an LED in an oxygen depleted environment may cause degradation of the LED. One result of such degradation is the browning of the silicone that may be used as an encapsulant for the LED chip. It is believed that the browning of the silicone may be caused by a combination of the environment in which the LED is operated (oxygen depleted), contaminants such as organics in the LED assembly or other components in the enclosure, the flux density of the optical energy from the LEDs and/or the thermal energy generated by the LEDs. While the exact cause of the degradation is not known, it has been discovered that the adverse effects may be prevented or reversed by lowering or eliminating the contaminants and/or by operating the LED in an oxygen containing environment. An LED that is operated in an oxygen containing environment does not exhibit the degradation, and the degradation of an LED that occurs due to the lack of oxygen may be reversed by operating the LED in an oxygen containing environment.
The amount of oxygen used in the enclosure may be related to the presence or absence of the contaminants such that in an environment containing few contaminants less oxygen is required and in an environment containing higher levels of contaminants higher levels of oxygen may be required. In some embodiments, no oxygen is required such that the gas may contain only highly efficient thermal gas such as H and/or He. In environments having low levels of contaminants the oxygen may comprise approximately 5%, 4% or less by volume of the total gas in the enclosure such as approximately 1%. The oxygen may comprise less than approximately 50% by volume of the total gas in the enclosure. In some embodiments, the oxygen may comprise less than approximately 40% or less than approximately 25% by volume of the total gas in the enclosure.
In one embodiment, for a 40 watt equivalent bulb having 20 LEDs the gas may comprise at least approximately 50% by volume of oxygen with the remaining gas being a higher thermally conductive gas such as helium or a combination of other more thermally conductive gases such as helium and hydrogen. At a mixture of 50% oxygen and 50% helium the gas has a thermal conductivity of about 87.5 mW/m-K. The greater the volume of oxygen in the enclosure, the better the environment is for preventing the degradation of the LED; however, the greater the volume of a high thermally conductive gas in the enclosure, the better the dissipation of heat from the LED assembly. Because the degradation of the LED may be related to contaminants in the LED assembly, the specific amount of oxygen needed in the enclosure may be determined for a specific application based on the construction of the LED assembly or other components in the enclosure. In some embodiments the gas may comprise at least approximately 40% oxygen by volume with the remaining gas being a higher thermal conductivity gas or a combination of other gases. In some embodiments the gas may comprise approximately 40-60% oxygen by volume with the remaining gas being a higher thermal conductivity gas or a combination of other gases.
In another example embodiment, for a 60 watt equivalent bulb having 20 LEDs the gas may comprise approximately 100% by volume oxygen as the gas in the enclosure. However, because oxygen is not a particularly good thermal conductor the use of about 100% oxygen in the enclosure may not provide sufficient heat transfer from the LED assembly. To increase the heat transfer from the LED assembly a gas movement device may be used such as described herein to circulate the oxygen over the LED assembly to increase the heat transfer from the LED assembly to the gas. As described with respect to
In some embodiments, the degradation of the LED may be prevented by the construction of the LED. For example, a silicon nitride layer may be included on the light emitting surface and a sealed environment may surround the light emitting surface. In some embodiments, the silicon nitride layer is directly on and covers the light emitting surface. The sealed environment may comprise a sealed gaseous environment as described herein.
The silicon nitride layer may provide an embodiment of a substance blocking or impermeable layer that can prevent substances such as moisture, carbon, and/or Volatile Organic Compounds (VOCs) that contain carbon, from reaching the light emitting surface. The substance blocking layer is directly on, and completely covers, the light emitting surface and in some embodiments, the substance blocking layer may comprise a plurality of sublayers. Moreover, materials other than silicon nitride, such as boron nitride and/or other inorganic/organic materials, may also be used. One such example is described U.S. patent application Ser. No. 13/758,565 filed on Feb. 4, 2013, titled “Lighting Emitting Diodes Including Light Emitting Surface Barrier Layers, and Methods of Fabricating Same,” the disclosure of which is incorporated by reference herein in its entirety.
Referring to
A glass stem 1120 is fused to the glass enclosure 1112 in the area of neck 1115. The glass stem 1120 may comprise a generally hollow outer dome 1121 having a first end that extends into the body 1114 and a second end that is fused to the enclosure 1112 such that the interior of the enclosure 1112 is sealed from the external environment. A tube 1126 having an internal passageway 1123 extends through the interior of dome 1121. An annular cavity 1125 is created between the tube 1126 and dome 1121. Wires 1150 may extend between the LED assembly 1130 and base 1102 through the annular cavity 1125. The LED assembly may be implemented using a printed circuit board (“PCB”) and may be referred by in some cases as an LED PCB.
The lamp 1000 comprises a solid-state lamp comprising a LED assembly 1130 with light emitting LEDs 1127. Multiple LEDs 1127 can be used together, forming an LED array 1128. The LEDs 1127 can be mounted on or fixed within the lamp in various ways. In at least some example embodiments, a submount 1129 is used. The LEDs 1127 in the LED array 1128 include LEDs which may comprise an LED die disposed in an encapsulant such as silicone, and LEDs which may be encapsulated with a phosphor to provide local wavelength conversion, as will be described later when various options for creating white light are discussed. A wide variety of LEDs and combinations of LEDs may be used in the LED assembly 1130 as described herein. The LEDs 1127 of the LED array 1128 of lamp 1000 may be mounted on multiple sides of submount 1129 and are operable to emit light when energized through an electrical connection. Wires 1150 run between the submount 1129 and the lamp base 1102 to carry both sides of the supply to provide critical current to the LEDs 1127. The wires 1150 may be used to both supply current to the LEDs and to physically support the LEDs on the stem 1120.
In some embodiments, a driver 1110 and/or power supply 1111 are included with the LED array on the submount 1129 as shown in
The AC to DC conversion may be provided by a boost topology to minimize losses and therefore maximize conversion efficiency. The boost supply is connected to high voltage LEDs operating at greater than 200V. Other embodiments are possible using different driver configurations, or a boost supply at lower voltages.
The LED assembly 1130 also may be physically supported by the stem 1120. In certain embodiments, a tube 1133 extends beyond the end of the hollow stem 1120. In one embodiment the tube 1133 and stem 1120 are formed of glass and may be formed as a one-piece member. In some embodiments, there is no tube 1133. The tube 1133 comprises a passageway 1135 that receives a post or base 1137 formed on a support 1143. Support 1143 further comprises retention features 1139, such as a plurality of radially extending arms 1139 that are supported by the post 1137. The arms 1139 may extend from the post 1137 in a star pattern where, for example, about six arms are provided. The exact number of arms 1139 may be dictated by the amount of support required for a particular LED assembly. In one embodiment the post 1137 and arms 1139 may be formed as one-piece from molded plastic. The arms 1139 engage the LED assembly 1130 to support the LED assembly on stem 1120. In one embodiment the arms 1139 are inserted between fins 1141 formed on LED assembly 1130 such that the LED assembly is constrained from movement. The wires 1150 may be used to maintain the LED assembly 1130 in position on the support 1143 and to maintain the support 1143 in tube 1133. In some embodiments, the support 1143 rests on the stem 1120 or tube 1133. The LED assembly 1130 may also be supported by separate support wires 1117 that are fused into the glass stem 1120 and are connected to the LED assembly as shown in
The use of a glass stem 1120 to support the LED assembly 1130 is counter to LED lamp design because glass is thermally insulating. Typically, the LEDs in a lamp are supported on a metal support that thermally connects the LEDs to the base 1102 and/or to an associated heat sink such that heat generated by the LEDs may be conducted away from the LEDs and dissipated from the lamp via the metal support, the base and/or the heat sink. Because glass stem 1120 is not thermally conductive it will not efficiently conduct heat away from the LEDs 1127. Because thermal management is critical for the operation of LEDs such an arrangement has not been considered suitable for an LED lamp.
The inventors of the present invention have discovered that the centralized LED array 1128 and any co-located power supply and/or drivers for lamp 1000 may be adequately cooled by helium gas, hydrogen gas, and/or another thermal material which fills the optically transmissive enclosure 1112 and provides thermal coupling to the LEDs 1127. The thermal material may comprise a combination of gasses such as helium and oxygen, or helium and air, or helium and hydrogen, or helium and neon or other combination of gases. In a preferred embodiment the thermal conductivity of the combined gases is at least about 60 mW/m-K. The helium, hydrogen or other gas may be under pressure, for example the pressure of the helium or other gas may be greater than 0.5 atmosphere. The pressure of the helium or other gas may be greater than 1 atmosphere. The helium or other gas may be about 2 atmospheres, about 3 atmospheres, or even higher pressures. In some embodiments the gas pressure may be in a range from about 0.5 to 1 atmosphere, about 0.5 to 2 atmospheres, about 0.5 to 3 atmospheres, or about 0.5 to 10 atmospheres. Because the gas adequately cools the LEDs, the lamp 1000 may use a traditional glass stem 1120 to support the LED assembly 1130.
To facilitate the cooling of the LEDs 1127, the LEDs may be mounted on a thermally conductive submount 1129 that improves and increases the heat transfer between the thermal gas contained in enclosure 1112 and the LEDs 1127. The submount 1129 may comprise heat sink structure 1149 comprising a plurality of fins or other similar structure 1141 that increases the surface area of contact between the heat sink and the thermal gas in enclosure 1112.
In some embodiments a gas movement device 1116 may be provided to move the thermal gas within the enclosure 1112 to increase the heat transfer between the LEDs 1127, LED array 1128, submount 1129, and/or heat sink 1149 of LED assembly 1130 and the thermal gas contained in enclosure 1112 as shown in
In the embodiment of
The LED array 1128 is mounted on a first portion of the LED assembly and the heat sink structure 1149 forms a second part of the LED assembly that is thermally coupled to, and extends from, the first portion of the LED assembly. “Thermally coupled” is meant to be a thermal path that provides sufficient heat dissipation to enable acceptable LED performance and longevity but is not meant to cover any path where heat may travel in a very inefficient manner, such as through a thermally insulating material. As described herein the first portion and second portion may be formed of single or multiple components of single or multiple layers and/or materials. The first portion is dimensioned to support the LED array while the second portion is dimensioned to dissipate heat from the LEDs. The second portion may be significantly larger than the first portion to increase the surface area of the heat sink portion to more effectively transfer heat to the gas. The heat sink structure 1149 may comprise fins 1141. Because the heat sink structure 1149 transfers heat from the LED assembly to the gas in the enclosure 1114 the heat sink structure is completely contained in the sealed enclosure such that a significant thermal path from the LED assembly 1130 is through the fins, the gas and the enclosure. As a result, the heat sink structure 1149 need not be directly connected to the base 1102 via a thermal coupling such as a metal connection. In certain embodiments, the only metal connection between the heat sink structure and the base is through the electrically conductive wires 1150 that form part of the electrical path to the LED array and the primary thermal path from the LED assembly 1130 is through the fins, the gas and the enclosure.
The LED assembly 1130 may be supported on the glass stem 1120 such as by support 1143. In certain embodiments the glass stem and support are thermal insulators, or at least are poor thermal conductors, such that the thermal paths from the LED assembly 1130 is through the gas and enclosure and a secondary thermal path is through wires 1150. In
Depending on the embodiment, different types of supports and multiple supports 1143 are possible to provide support for the LED assembly. In certain embodiments the support is built integral with the stem 1120 or integral with the LED assembly 1130. In other embodiments, a separate support 1143 is used. In certain embodiments, supporting surfaces 1139 engage the LED assembly 1130, and a base 1137 retains the position of the support 1143 relative to the LED assembly 1130. In some embodiments, the base 1137 engages a tube 1133 that is integral to the stem 1120. In some embodiments the base 1137 simply rests on the stem 1120. In some embodiments, the base 1137 is integral with the supporting surfaces 1139. The arms or support members 1139 may engage the LED assembly 1130 through grooves, channels or holes in the support 1143. The supporting surfaces 1139 engage the LED assembly 1130 between the fins 1141. In other embodiments, other supporting arrangements are possible which engage the LED assembly using holes, grooves, notches, friction fit and/or other engagement structures.
In certain embodiments, because heat is primarily dissipated from the LED assembly 1130 through the gas and enclosure, rather than though a physical heat path to the base, a significantly larger thermal path is created through the heat sink structure, gas and enclosure than through the wires 1150. The heat transfer through the wires 1150 is less than the heat transfer through the heat sink structure, gas and enclosure, and in some embodiments significantly less. Accordingly, in some embodiments the LED assembly 1130 is arranged in the enclosure such that the heat sink structure extends into the volume of gas. The ends of the heat sink structure terminate in the enclosure. The heat sink structure is surrounded by or substantially surrounded by the gas in the enclosure. In other words the heat sink structure and LED assembly are disposed in the gas such that the gas substantially surrounds and contacts the external surfaces of the heat sink structure and LED array. It is to be understood that the gas surrounding or substantially surrounding the heat sink structure distinguishes from arrangements where the heat sink structure extends into and/or is directly connected to the base or other external structure by a physical thermal coupler where the primary thermal path follows the physical connection. The term surrounding or substantially surrounding the heat sink structure includes heat sink structures that may comprise multiple layers where the gas may contact some of the layers or portions of some of the layers but not contact all of the layers. In some embodiments, the ends of the heat sink structure may be described as terminating in the gas inside of the sealed enclosure rather than extending to the base or to a metal thermal conductor. In some embodiments, the heat sink structure is not directly connected to the base other than by the electrical wires 1150 such that the primary thermal transfer path from the LEDs is through the gas to the enclosure. In some embodiments, the heat sink structure and LED assembly are physically separated from the base.
Because heat is conducted away from the LEDs by the heat sink structure and the gas, the effectiveness of the heat transfer may be affected by the surface area of the heat sink structure and the proximity of the heat sink structure to the enclosure. Making the heat sink structure of a suitable surface area increases heat transfer from the LED assembly to the gas. Making at least a portion of the heat sink structure in relatively close proximity to the enclosure shortens the length of the thermal path to the enclosure where the heat is dissipated to the ambient environment.
In one embodiment, the distance between the heat sink structure 1149 and the enclosure 1112, at the closest point between the heat shrink structure and the enclosure, is less than about 8 mm. In the illustrated embodiment this is accomplished by arranging the heat sink structure to one side of the LED array such that the distal end of the heat sink structure is disposed adjacent the narrow neck portion 1115 of the enclosure where the narrowed neck brings the surface of the enclosure into close proximity with the heat sink structure. Suitable dimensions of one embodiment of a lamp are shown in
In one embodiment, the surface area of the LED assembly is at least about 3,000 square mm. In some embodiments, the exposed surface area of the heat sink structure is at least 4,000 square mm, at least 5,000 square mm, and at least 8,000 square mm. The exposed surface area may be between approximately 2,000 to 10,000 square mm and in one embodiment the surface area may be approximately between 4,000 square mm and 5,000 square mm. In another embodiment, the exposed surface area of one side of the heat sink structure 1149 may approximately between 1500 square mm and 4000 square mm. Referring to
In some embodiments, the LED bulb 1000 is equivalent to a 60 Watt incandescent light bulb. In one embodiment of a 60 Watt equivalent LED bulb, the LED assembly 1130 comprises an LED array 1128 of 20 XLamp® XT-E High Voltage white LEDs manufactured by Cree, Inc., where each XLamp® XT-E LED has a 46 V forward voltage and includes 16 DA LED chips manufactured by Cree, Inc. and configured in series. The XLamp® XT-E LEDs may be configured in four parallel strings with each string having five LEDs arranged in series, for a total of greater than 200 volts, e.g. about 230 volts, across the LED array 1128. In another embodiment of a 60 Watt equivalent LED bulb, 20 XLamp® XT-E LEDs are used where each XT-E has a 12 V forward voltage and includes 16 DA LED chips arranged in four parallel strings of four DA chips arranged in series, for a total of about 240 volts across the LED array 1128 in this embodiment. In some embodiments, the LED bulb 1000 is equivalent to a 40 Watt incandescent light bulb. In such embodiments, the LED array 1130 may comprise 10 XLamp® XT-E LEDs where each XT-E includes 16 DA LED chips configured in series. The 10 46V XLamp® XT-E® LEDs may be configured in two parallel strings where each string has five LEDs arranged in series, for a total of about 230 volts across the LED array 1128. In other embodiments, different types of LEDs are possible, such as XLamp® XB-D LEDs manufactured by Cree, Inc. or others. Other arrangements of chip on board LEDs and LED packages may be used to provide LED based light equivalent to 40, 60 and/or greater other watt incandescent light bulbs, at about the same or different voltages across the LED array 1128.
In one embodiment, the LED assembly 1130 has a maximum outer dimension of the first portion that includes the LED array 1128 that fits into the open neck of the enclosure 1112 during the manufacturing process and an internal dimension of a portion of the second portion that is at least as wide as the width or diameter of the stem 1120. In one embodiment, at least an upper portion of the LED assembly has a maximum diameter that is less than the diameter of the neck and a lower portion has an internal dimension that is at least as wide as the width or diameter of the stem. In one embodiment the LED array is dimensioned so as to be able to be inserted through the neck of the enclosure and at least another portion of the LED assembly has a greater diameter than the stem. In some embodiments the LED assembly, stem and neck have a cylindrical shape such that the relative dimensions of the stem, LED assembly and the neck may be described as diameters. In one embodiment, the diameter of the LED assembly may be approximately 20 mm. In other embodiments some or all of these components may be other than cylindrical or round in cross-section. In such arrangements the major dimensions of these elements may have the dimensional relationships set forth above. In other embodiments, the LED assembly 1130 can have different shapes, such as triangular, square and/or other polygonal shapes with or without curved surfaces.
Still referring to
a shows a portion of an exploded view of an embodiment of the LED bulb 1000 showing further detail of how the electrical wires 1150 are connected to the Edison base socket 1103. As shown, the electrical wires 1150 run through the stem 1120 which has been fused to the enclosure 1115 as described herein. The base upper part 1102a comprises wire retention features 1116. In this embodiment, the wire retention features are simply members 1116 that extend across the base upper part 1102a. The wires are wrapped or at least retained by the wire retention features. In certain embodiments, the retention members 1116 can include holes, grooves or other features that aid in the alignment and retention of the wires 1150. In this embodiment the retention members 1116 are integral with a cavity or hole 1117 which assists in aligning the upper base 1102a with tube 1126 and thereby the enclosure 1112. Other alignment, support and/or retention features are possible.
As shown in
a shows another embodiment of the base upper part 1102a in which an electrical coupling 1119 is integral with the upper base 102a. In this embodiment, the electrical coupling or interconnect 1119 includes a first contact portion 1119a that engages the wires 1150, and a second contact portion 1119b that engages the contacts 1106 of the circuitry 1110 in the lower base 1102b when the upper base 102a, the lower base 1102b and the enclosure 1112 are connected together. In this embodiment, the electrical coupling 1119 includes a hole 1117 which receives the tube 1126 to aid in alignment and retention of the electrical wires 1150 and of the electrical coupling 1119 as well as the upper base 1102a with the enclosure 1112. Other configurations are possible for the electrical interconnect 1119, the lower base 1102b and/or the upper base 1102a. Depending on the embodiment, the electrical coupling between the wires 1150 and any circuitry 1110 in the base 1102 as well as any alignment or wire retention features 1116, 1117 or 1118, the lower base 1102b and/or the upper base 1102a can be integrated into a single component and/or comprise multiple components. For example,
e illustrate an embodiment of a lamp 1000 that can serve as a replacement for an incandescent bulb. This embodiment makes use of similar components or features which have already been described using the reference numbers shown in the drawings. In this embodiment, the support 1143 is similar to the support described with reference to
Any aspect or features of any of the embodiments described herein can be used with any feature or aspect of any other embodiments described herein or integrated together or implemented separately in single or multiple components.
To further explain the structure and operation of an embodiment of the lamp 1000 an embodiment of a method of making a lamp will be described. Referring to
Referring to
Referring to
Referring to
Because the LEDs 1127 and LED assembly 1130 are heat sensitive the application of heat to fuse the stem part 1131 to the enclosure 1112 may cause an overtemperature situation for the LED assembly 1130. Overtemperature is a concern for at least two reasons. First, overtemperature may degrade the performance of the LEDs 1127 in use such as by substantially shortening LED life. Overtemperature may also affect the solder connection between the LEDs 1127 and the PCB, base or other submount where the LEDs may loosen or become dislodged from the LED assembly 1130. Overtemperature may be caused by a combination of both peak temperature and the length of time the LED assembly 1130 is exposed to heat. Overtemperature as used herein means a heating of the LED assembly 1130 or LEDs 1127 such that either the performance of the LEDs is degraded or the solder connection is degraded or both. It is desired when attaching the stem part 1131 to the enclosure 1112 that heat transferred to the LEDs 1127 during the fusing process is minimized. The fusing operation occurs at approximately 800 degrees C. and the temperature of the LED array and LEDs must typically be maintained below 325 degrees C. Depending upon the type of LED and its construction in some embodiments the temperature of the LED array and LEDs must be maintained below 300 degrees C., 275 degrees C., 250 degrees C., 235 degrees C., and 215 degrees C. The time of exposure of the heat must also be controlled depending upon the reflow characteristics of the solder and the LED assembly specifications. The overall cycle time of the fusing operation is approximately 15 seconds to 45 seconds in duration, with the glass in the molten stage for 5 to 15 seconds. Prior to the molten stage the glass to be fused is preheated so that residual stress is not incorporated into the assembly. The thermal resistance of the electrical path is selected so as to not cause overtemperature for the duration of the heating process such that the long-term operation of the LEDs and/or the bonds to the submount are not degraded. The temperature at the LEDs should be maintained at least below the temperature and time period where the LED remains bonded to the submount and/or does not fall apart or degrade. Depending on the particular LEDs and bonding materials, these temperatures may vary. Additionally, these temperatures may change depending on the time duration of the exposure to the elevated temperatures.
The inventors of the present invention have determined that during the fusing operation the transfer of heat to the LEDs results primarily from heat conduction through the wires 1150 rather than heat convection through the ambient environment. The inventors have concluded that by increasing the thermal resistance through the wires 1150 and/or by increasing the thermal resistance of the electrical path from the connection point of the wires 1150 to the LED assembly 1130 and the LEDs 1127, the heat transfer to the LEDs during the fusing operation may be maintained below overtemperature levels. Increasing the thermal resistance of the wires 1150 may be accomplished using a variety of techniques. In one embodiment the thermal resistance of the wires is increased by increasing the length of the wires. The wire length may be increased by simply making the wires 1150 longer as shown in
Thermal resistance of the wires may also be increased by making the cross-sectional area of the wires thin enough that the heat does not cause an overtemperature. The thermal resistance of the wires may also be increased by a combination of making the cross-sectional area of the wires thinner and increasing the length of the wire path.
Another technique for increasing the thermal resistance of the electrical path between the heat source during the fusing operation and the LEDs 1127 is to connect the wires to an electrically conductive element that is remote from LEDs 1127 as shown in
Referring to
The steps described herein may be performed in an automated assembly line having rotary tables or other conveyances for moving the components between assembly stations.
While specific reference has been made with respect to an A-series lamp with an Edison base 1102 the structure and assembly method may be used on other lamps such as a PAR-style lamp such as a replacement for a PAR-38 incandescent bulb or a BR-style lamp. Moreover, while the use of a thermally conductive gas in the enclosure has been found to adequately manage heat, additional heat sinks may be provided if desired. For example heat conductive elements may be formed in or adjacent to the glass stem 1120 to conduct heat from the LEDs 1127 to the base 1102 where the heat may be dissipated by the base or an associated heat sink.
An embodiment of the LED assembly 1130 will be described with reference to
Connectors 1203 connect the anode 1201 from one pair to the cathode 1202 of the adjacent pair to provide the electrical path between the pairs during operation of the LED assembly 1130. Typically, tie bars 1205 are also provided in the lead frame 1200 to hold the first portion of the lead frame to the second portion of the lead frame and to maintain the structural integrity of the lead frame during manufacture of the LED assembly. The tie bars 1205 are cut from the finished LED assembly and perform no function during operation of the LED assembly 1130. The lead frame 1200 also comprises a heat sink structure 1149 such as fins 1141 that are connected to the anodes 1201 and cathodes 1202 to conduct heat away from the LEDs and transfer the heat to the thermal gas in enclosure 1112 where the heat may be dissipated from the lamp. While a specific embodiment of fins 1141 is shown, the heat sink structure 1149 may have a variety of shapes, sizes and configurations. The lead frame 1200 may be formed by a stamping process and a plurality of lead frames may be formed in a single strip or sheet or the lead frames may be formed independently. In one method, the lead frame 1200 is formed as a flat member and is bent into a suitable three-dimensional shape such as a cylinder, sphere, polyhedra or the like to form LED assembly 1130. Because the lead frame 1200 is made of thin bendable material, and the anodes 1201 and cathodes 1202 may be positioned on the lead frame 1200 in a wide variety of locations, and the number of LEDs may vary, the lead frame 1200 may be configured such that it may be bent into a wide variety of shapes and configurations.
Referring to
In some embodiments, the LED packages 1210 may not hold the lead frame 1200 together with sufficient structural integrity. In some embodiments separate supports 1211 may be provided to hold the lead frame 1200 together as shown in
The LED packages 1210 may be secured to the lead frame 1200 before or after the supports 1211 are attached. While in the illustrated embodiments the supports 1211 are connected between the anodes 1201 and cathodes 1202 the supports 1211 may connect between other components such as portions of the heat sink structure 1149. The supports 1211 may be made of polyphthalamide white reflective plastic such as AMODEL® manufactured by Solvay Plastics. The material of the supports 1211 may preferably have the same coefficient of thermal expansion as the LED substrate of LED packages 1210 such that the LED packages and supports 1211 expand and contract at the same rate to prevent stresses from being created between the components. This may be accomplished using a liquid crystal polymer to make the supports 1211 with the desired engineered parameters
The lead frame 1200 may be bent or folded such that the LEDs 1127 provide the desired light pattern in lamp 1000. In one embodiment the lead frame 1200 is bent into a cylindrical shape as shown, for example, in
Because the lead frame 1200 is pliable and the LED placement on the lead frame may be varied, the lead frame may be formed and bent into a variety of configurations.
Another embodiment of a lead frame is shown in
The anodes 1501 are connected to the cathodes 1502 by the LEDs to provide the electrical path between the pairs during operation of the LED assembly 1130. Typically, tie bars 1505 are also provided in the lead frame 1500 to hold the portions of the lead frame together and to maintain the structural integrity of the lead frame during manufacture of the LED assembly. The tie bars 1505 are cut from the finished LED assembly and perform no function during operation of the LED assembly 1130. The tie bars may be located at other locations and a greater or fewer number of tie bars may be used.
The lead frame 1500 also comprises a heat sink structure 1549 such as fins 1541 that are connected to the anodes 1501 and cathodes 1502 to conduct heat away from the LEDs and transfer the heat to the thermal gas in enclosure 1112 where the heat may be dissipated from the lamp. While a specific embodiment of fins 1541 is shown, the heat sink structure 1549 may have a variety of shapes, sizes and configurations. The lead frame 1500 may be formed by a stamping process and a plurality of lead frames may be formed in a single strip or sheet or the lead frames may be formed independently. In one method, the lead frame 1500 is formed as a flat member and is bent into a suitable three-dimensional shape such as a cylinder, sphere, polyhedra or the like to form LED assembly 1130. Because the lead frame 1500 is made of thin bendable material, and the anodes 1501 and cathodes 1502 may be positioned on the lead frame 1500 in a wide variety of locations, and the number of LEDs may vary, the lead frame 1500 may be configured such that it may be bent into a wide variety of shapes and configurations. In one embodiment the lead frame is approximately 10-12 thousandths of an inch thick.
An LED package containing at least one LED 1127 is secured to each anode and cathode pair where the LED package spans the anode 1501 and cathode 1502. The LED packages are located in the squares 1503. The LED packages may be attached to the lead frame 1500 by soldering. Once the LED packages are attached, the tie bars 1505 may be removed because the LED packages 1510 hold the portions of the lead frame together.
Referring to
The plastic material extends through the pierced areas 1212 to both sides of the lead frame 1200 such that the plastic material bridges the components of the lead from to hold the components of the lead frame together after the tie bars 1205 are cut. The supports 1211 on the outer side of the lead frame 1200 (the term “outer” as used herein is the side of the lead frame to which the LEDs are attached) comprises a minimum amount of plastic material such that the outer surface of the lead frame is largely unobstructed by the plastic material (
Further, referring to
In addition to electrically insulating the edges of the lead frame, the plastic overhangs 1513 and 1515 may be used to join the edges 1514 and 1516 of the lead frame 1500 together in the three dimensional LED assembly. One of the overhangs may be provided with a first connector or connectors 1517 that mates with a second connector or connectors 1519 provided on the second overhang. The first connectors may comprise a male or female member and the second connectors may comprise a mating female or male member. Because the overhangs are made of plastic the connectors may comprise deformable members that create a snap-fit connection. The mating connectors formed on the first overhang 1513 and second overhang 1515 may be engaged with one another to hold the lead frame in the final configuration.
The LED packages 1210 may be secured to the lead frame 1500 before or after the supports 1511 are attached. While in the illustrated embodiments the supports 1511 are connected between the anodes 1501 and cathodes 1502 the supports 1511 may be connected between other components such as portions of the heat sink structure 1149. The supports 1511 may be made of polyphthalamide white reflective plastic such as AMODEL® manufactured by Solvay Plastics. The material of the supports 1511 may preferably have the same coefficient of thermal expansion as the LED substrate of LED packages 1210 such that the LED packages and supports 1511 expand and contract at the same rate to prevent stresses from being created between the components. This may be accomplished using a liquid crystal polymer to make the supports 1511 with the desired engineered parameters
The lead frame 1500 may be bent or folded such that the LEDs 1127 provide the desired light pattern in lamp 1000. In one embodiment the lead frame 1500 is bent into a cylindrical shape as shown in
Another alternate embodiment of LED assembly 1130 is shown in
In one embodiment the core board 1300 is formed as a flat member having a central band 1304 on which the LED packages 1310 containing LEDs 1127 are mounted as shown in
Referring to
Another embodiment of LED assembly 1130 is shown in
Referring to
The LED assembly 1130 comprises a bendable circuitized submount 1802 where the submount includes electrical circuitry 1803 for connecting the LEDs to the electronics on board 1800 and the LEDs 1127 are mounted directly to the submount 1802 in electrical communication with the circuitry 1803. The LEDs 1127 may be mounted to the submount 1802 using chip on board technology. In one embodiment the LEDs 1127 are mounted to the submount 1802 when the submount is in a planar or flat configuration. After the LEDs 1127 are mounted to the submount 1802 the submount may be bent to form the three-dimensional shape as described herein and as shown in
Another embodiment of the LED assembly 1130 is shown in
A connection may be made directly between the board 1800 supporting the lamp electronics and the LED assembly 1130 to physically support the LED assembly and to provide current to the LEDs. In one embodiment, the submount 1802 is formed with one of a male connector and a female connector and the board 1800 is formed with the other one of a mating female and a male connector. In the illustrated embodiment, the submount 1802 is formed with the female connector in the form of a slot 1812. The board 1800 is formed with the mating male connector in the form of a tab 1814 where the tab may be inserted into the 1812 slot to connect the LED assembly 1130 to the board 1800. The board 1800 is also formed with mating male connectors in the form of tabs 1816 where the tabs 1816 may be inserted into slots 1818 between adjacent fins 1804 to further secure the LED assembly 1130 to the board 1800 and to orient and guide the LED assembly 1130 as it is mounted on the board 1800. The submount 1802 may also be secured to the board 1800 using a mechanical lock or friction engagement, or fasteners including mechanical fasteners, adhesive or the like. In the illustrated embodiment a resilient tab 1820 is provided adjacent the slot 1812 that is deformed by the tab 1814 when the LED assembly 1130 is mounted on the board 1800. The resiliency of the tab 1820 creates a pressure force on the tab 1814 to further secure the board to the LED assembly.
Electrical contacts may also be formed on the board 1800 and the LED assembly 1130 to complete the electrical path between the board 1800 and the LED assembly 1130 when the LED assembly 1130 is mounted on the board 1800. In one embodiment, a first pair of contacts 1822 may be formed on the resilient tab 1820 that engages a second pair of contacts 1824 on the board 1800 to complete the electrical path. The electrical contacts 1822 on the tab 1820 are electrically coupled to the LEDs 1127 via the circuit on the submount 1802. The contacts 1824 on the board are electrically coupled to the lamp electronics and via the board 1800 to the wires 1150 and Edison base 1103. While a pressure contact may be used to connect the contacts 1822 to the contacts 1824 the electrical connection between the board 1800 and the LED assembly 1130 may be made through a soldered joint or other electrical connection.
Another embodiment of the lamp is shown in
The LED assembly 1130 comprises a single sided flex circuit 1900 comprised of a thermally conductive material such as copper, aluminum or the like on a flexible film. The flex circuit 1900 may comprise a flexible conductive layer supported on a dielectric film such as a polyimide film. The flex circuit 1900 is populated with LEDs 1127 and the LEDs may be reflow soldered to the conductive layer 1522. The LED solder joints 1524 provide the electrical connections to the anode and cathode sides of the flex circuit. A white cover layer may be added to increase the light reflectivity of the LED assembly. The flex circuit 1900 is bent, rolled or otherwise formed into a suitable three-dimensional shape providing surfaces for supporting the LEDs 1127. The LEDs may comprise surface mount LEDs. In the illustrated embodiment the flex circuit 1900 comprises a generally cylindrical shape having vertical surfaces that support the LEDs 1127 such that the bases of the LEDs 1127 are disposed generally along the longitudinal axis of the lamp with the LEDs facing laterally generally toward the sides of the lamp. The edges of the flex circuit may be joined using sonic welding, heat stakes, adhesive or other mechanism to hold the flex circuit in the desired three-dimensional shape. The LEDs 1127 are mounted to the flex circuit 1900 to complete the LED assembly. In one embodiment the LEDs 1127 are mounted to the flex circuit when the flex circuit is in a planar or flat configuration. After the LEDs are mounted to the flex circuit the flex circuit may be bent or rolled to form the three-dimensional shape as described herein and as shown in
The flex circuit is flooded with copper to provide enough heat conductive material that heat generated by the LEDs may be dissipated to the thermal gas in the enclosure such that the performance of the LEDs is not degraded. As used herein “flooded” means that the portion of the circuit that is connected to the thermal pads on the mounting faces of the LED packages is maximized. Typically in a flex circuit the circuit connections are point to point, such that the connections form relatively narrow conductive paths on the substrate. In the present invention it is desired to maximize the amount of thermally conductive material, e.g. copper, on the substrate to the extent possible such that the circuit connections that are coupled to the thermal pads on the mounting faces of the LED packages form the large areas of copper rather than the narrow paths of traditional circuits. The thermally conductive electrical connectors are provided on the flexible substrate everywhere it can possibly go without compromising the integrity of the active electrical connections. In some applications minimum spacing or gaps are required between the active circuit portions and the thermal portions of the copper. The copper or other thermally conductive material is, in some embodiments, extended to the minimize this spacing. In some embodiments the spacing may be approximately 1.2 mm gaps up to approximately 2 mm or in some embodiments the spacing may be greater than 2 mm. The gaps may be present everywhere there are LEDs with electrical connections being routed; however, the gaps are minimized to the extent possible to maximize the amount of thermally conductive material on the flex circuit. In some embodiments the copper or other thermally conductive material may comprise up to approximately 50% of the area of the flex circuit substrate. The copper or other thermally conductive material may comprise between approximately 30% and 50% of the surface area of the flex circuit substrate. In some embodiments the copper or other thermally conductive material may comprise between approximately 20% and 40% of the surface area of the flex circuit substrate.
As a result, in some embodiments the flex circuit 1900 comprises significantly more copper than is necessary to create the electrical path to the LEDs 1127. The submount may be configured such that portions 1902 of the submount form “fins” or heat conducting elements that provide suitable surface area and allow air circulation such that heat generated by the LEDs is transferred to the thermal fluid in enclosure and is dissipated from the lamp. Because the flex circuit 1900 may be formed in a wide variety of patterns and the LEDs 1127 may be mounted in a variety of positions on the flex circuit, the flex circuit may be bent to provide a variety of LED patterns and corresponding light emission patterns. In some embodiments the flex circuit may comprise score lines 1903 to facilitate the bending of the flex circuit in the desired shape. In some embodiments an aluminum stiffener 1903 may be utilized to provide greater structural support for the LEDs and/or better thermal conductivity. The aluminum stiffener 1903 may be attached to the back of the flex circuit.
A connection may be made directly between the flex circuit 1900 and the board 1800 to physically support the LED assembly 1130 and to provide current to the LEDs 1127. In one embodiment the flex circuit 1900 is formed with one of a male connector and a female connector and the board is formed with one of a mating female and a male connector. In the illustrated embodiment the flex circuit 1900 is formed with the female connector in the form of slots 1912. One such slot may be provided on each side of flex circuit 1900. The board 1800 is formed with the mating male connectors in the form of tabs 1914 where the tabs 1914 may be inserted into the slots 1912 to connect the LED assembly 1130 to the board 1800. Each side of the board 1800 may also be formed with a recess that forms a top flange 1864 and a bottom flange 1866 where the lead frame 1850 is supported in the recess between the top and bottom flanges to further support the lead frame in the enclosure. The lead frame may be provided with notches that receive the flanges 1864, 1866. The flex circuit 1900 may also be secured to the board using a mechanical lock, friction engagement, mechanical fasteners, adhesive or the like. The tabs 1914 or areas of the board adjacent the tabs may comprise plated surfaces 1918 that are soldered to the flex circuit 1900 to create an electrical connection 1917 between the board and the flex circuit.
Another embodiment of the lamp is shown in
The LED assembly 1130 comprises a lead frame 1950 where the metal of the lead frame 1950 provides the physical support for the LEDs 1127 and forms part of the electrical path between the LEDs 1127 and the board 1800. The lead frame 1800 is made of a conductive material that is formed into a circuit. The circuit may be formed by stamping a flat conductive material such as copper, tin plated cold rolled steel, aluminum, nickel silver or other electrically conductive material. The lead frame 1850 may be stamped from, for example, a copper foil or a thin gauge copper sheet. The circuit may be stamped with interconnecting tie bars to hold the lead frame together during assembly of the LED assembly as previously described. The LEDs 1127 are populated on the lead frame 1850 and are connected to the electrical pads on the lead frame at joints. The joints may be formed by reflow soldering the LEDs to the electrical pads. In other embodiments the joint may be formed by a mechanical crimp, a weld, a press fit or other suitable joint. The tie bars may then be stamped out or otherwise removed from the lead frame leaving the LED solder joints, or other joints, to mechanically hold the lead frame circuit together as well as provide the electrical connections to the anode and cathode sides of the lead frame assembly. The LED assembly 1130 may then be formed into the desired three-dimensional shape. In one embodiment, the lead frame is bent or otherwise formed into a cylindrical shape. The lead frame 1850 may be provided with electrical contacts 1852, 1854 to electrically couple the lead frame to contacts on the board as previously described. The lead frame may also comprise portions 1856 or fins that are provided to increase heat transfer between the lead frame and the thermal gas in the enclosure 1112. The portions 1856 increase the surface area of the contact between the thermal gas and the lead frame 1850 to facilitate heat transfer. A high temperature tape 1856 such as a polyimide tape, such as KAPTON tape sold by DuPont, may be used to electrically isolate the fins 1856 from one another by holding the finds in spaced relationship relative to one another to prevent the fins from touching and shorting out the LED assembly.
A connection may be made directly between the lead frame 1850 and the board 1800 supporting the lamp electronics to physically support the LED assembly 1130 and to provide current to the LEDs 1127. In one embodiment the lead frame 1850 is formed with one of a male connector and a female connector and the board is formed with one of a mating female and a male connector. In the illustrated embodiment the lead frame is formed with the female connector in the form of slots 1860. The board is formed with the mating male connector in the form of tabs 1862 where the tabs may be inserted into the slots to connect the LED assembly 1130 to the board 1800. The board 1800 may also be formed with a recess that forms a top flange 1864 and a bottom flange 1866 where the lead frame 1850 is supported in the recess between the top and bottom flanges to further support the lead frame in the enclosure. The lead frame may be provided with notches that receive the flanges 1864, 1866. The lead frame 1850 may also be secured to the board 1800 using a mechanical lock, friction engagement, mechanical fasteners, adhesive or the like. The tabs 1862 or areas of the board adjacent the tabs may comprise plated surfaces that are soldered to the anode and cathode side of the lead frame to complete the electrical path between the board and the LED assembly.
Another embodiment of the lamp is shown in
The LED assembly 1130 comprises a bendable submount 1870 where the LEDs 1127 are mounted directly to the submount. Unlike the embodiment of
A connection may be made directly between the board 1800 supporting the lamp electronics and the LED assembly 1130 to physically support the LED assembly and to provide current to the LEDs. In one embodiment the submount is formed with one of a male connector and a female connector and the board is formed with one of a mating female and a male connector. In the illustrated embodiment the board 1800 is formed with the female connector in the form of slots 1876. The submount 1870 is formed with the mating male connector in the form of tabs 1878 where the tabs 1878 may be inserted into the slots 1876 to connect the LED assembly 1130 to the board 1800. The board 1800 is also formed with the mating male connectors in the form of tabs 1890 where the tabs may be inserted into slots 1891 between adjacent fins to further secure the LED assembly to the board and to orient and guide the board as it is inserted into the LED assembly. The submount may also be secured to the board using a mechanical lock or friction engagement. Moreover fasteners including mechanical fasteners, adhesive or the like may also be used. The tabs or areas of the board adjacent the tabs may comprise plated surfaces that are soldered to the LEDs to create an electrical connection 1893 to complete the electrical path between the board and the LEDs.
In the embodiments described with respect to
The LED assembly, whether made of a lead frame submount, metal core board submount, or a hybrid combination of metal core board/lead frame or a PCB made with FR4/lead frame may be formed to have any of the configurations shown herein or other suitable three-dimensional geometric shape. The LED assembly may be advantageously bent into any suitable three-dimensional shape. A “three-dimensional” LED assembly as used herein and as shown in the drawings means an LED assembly where the substrate comprises mounting surfaces for different ones of the LEDs that are in different planes such that the LEDs mounted on those mounting surfaces are also oriented in different planes. In some embodiments the planes are arranged such that the LEDs are disposed over a 360 degree range. The substrate may be bent from a flat configuration, where all of the LEDs are mounted in a single plane on a generally planar member, into a three-dimensional shape where different ones of the LEDs and LED mounting surfaces are in different planes.
As previously mentioned, at least some embodiments of the invention make use of a submount on which LED devices are mounted. In some embodiments, power supply or other LED driver components can also be mounted on the submount. A submount in example embodiments is a solid structure, which can be transparent, semi-transparent, diffusively transparent or translucent. A submount with any of these optical properties or any similar optical property can be referred to herein as optically transmissive. Such a submount may be a paddle shaped form, with two sides for mounting LEDs. If the submount is optically transmissive, light from each LED can shine in all directions, since it can pass through the submount. A submount for use with embodiments of the invention may have multiple mounting surfaces created by using multiple paddle or alternatively shaped portions together. Notwithstanding the number of portions or mounting surfaces for LEDs, the entire assembly for mounting the LEDs may be referred to herein as a submount. An optically transmissive submount may be made from a ceramic material, such as alumina, or may be made from some other optically transmissive material such as sapphire. Many other materials may be used.
An LED array and submount as described herein can be used in solid-state lamps making use of thermic constituents other than a gas. A thermic constituent is any substance, material, structure or combination thereof that serves to cool an LED, an LED array, a power supply or any combination of these in a solid-state lamp. For example, an optically transmissive substrate with LEDs as described herein could be cooled by a traditional heatsink made of various materials, or such an arrangement could be liquid cooled. As examples, a liquid used in some embodiments of the invention can be oil. The oil can be petroleum-based, such as mineral oil, or can be organic in nature, such as vegetable oil. The liquid may also be a perfluorinated polyether (PFPE) liquid, or other fluorinated or halogenated liquid. An appropriate propylene carbonate liquid having at least some of the above-discussed properties might also be used. Suitable PFPE-based liquids are commercially available, for example, from Solvay Solexis S.p.A of Italy. Flourinert™ manufactured by the 3M Company in St. Paul, Minn., U.S.A. can be used as coolant.
As previously mentioned, the submount in a lamp according to embodiments of the invention can optionally include the power supply or driver or some components for the power supply or driver for the LED array. In some embodiments, the LEDs can actually be powered by AC. Various methods and techniques can be used to increase the capacity and decrease the size of a power supply in order to allow the power supply for an LED lamp to be manufactured more cost-effectively, and/or to take up less space in order to be able to be built on a submount. For example, multiple LED chips used together can be configured to be powered with a relatively high voltage. Additionally, energy storage methods can be used in the driver design. For example, current from a current source can be coupled in series with the LEDs, a current control circuit and a capacitor to provide energy storage. A voltage control circuit can also be used. A current source circuit can be used together with a current limiter circuit configured to limit a current through the LEDs to less than the current produced by the current source circuit. In the latter case, the power supply can also include a rectifier circuit having an input coupled to an input of the current source circuit.
Some embodiments of the invention can include a multiple LED sets coupled in series. The power supply in such an embodiment can include a plurality of current diversion circuits, respective ones of which are coupled to respective nodes of the LED sets and configured to operate responsive to bias state transitions of respective ones of the LED sets. In some embodiments, a first one of the current diversion circuits is configured to conduct current via a first one of the LED sets and is configured to be turned off responsive to current through a second one of the LED sets. The first one of the current diversion circuits may be configured to conduct current responsive to a forward biasing of the first one of the LED sets and the second one of the current diversion circuit may be configured to conduct current responsive to a forward biasing of the second one of the LED sets.
In some of the embodiments described immediately above, the first one of the current diversion circuits is configured to turn off in response to a voltage at a node. For example a resistor may be coupled in series with the sets and the first one of the current diversion circuits may be configured to turn off in response to a voltage at a terminal of the resistor. In some embodiments, for example, the first one of the current diversion circuits may include a bipolar transistor providing a controllable current path between a node and a terminal of a power supply, and current through the resistor may vary an emitter bias of the bipolar transistor. In some such embodiments, each of the current diversion circuits may include a transistor providing a controllable current path between a node of the sets and a terminal of a power supply and a turn-off circuit coupled to a node and to a control terminal of the transistor and configured to control the current path responsive to a control input. A current through one of the LED sets may provide the control input. The transistor may include a bipolar transistor and the turn-off circuit may be configured to vary a base current of the bipolar transistor responsive to the control input.
It cannot be overemphasized that with respect to the features described above with various example embodiments of a lamp, the features can be combined in various ways. For example, the various methods of including phosphor in the lamp can be combined and any of those methods can be combined with the use of various types of LED arrangements such as bare die vs. encapsulated or packaged LED devices. The embodiments shown herein are examples only, shown and described to be illustrative of various design options for a lamp with an LED array.
LEDs and/or LED packages used with an embodiment of the invention and can include light emitting diode chips that emit hues of light that, when mixed, are perceived in combination as white light. Phosphors can be used as described to add yet other colors of light by wavelength conversion. For example, blue or violet LEDs can be used in the LED assembly of the lamp and the appropriate phosphor can be in any of the ways mentioned above. LED devices can be used with phosphorized coatings packaged locally with the LEDs or with a phosphor coating the LED die as previously described. For example, blue-shifted yellow (BSY) LED devices, which typically include a local phosphor, can be used with a red phosphor on or in the optically transmissive enclosure or inner envelope to create substantially white light, or combined with red emitting LED devices in the array to create substantially white light. Such embodiments can produce light with a CRI of at least 70, at least 80, at least 90, or at least 95. By use of the term substantially white light, one could be referring to a chromacity diagram including a blackbody locus of points, where the point for the source falls within four, six or ten MacAdam ellipses of any point in the blackbody locus of points.
A lighting system using the combination of BSY and red LED devices referred to above to make substantially white light can be referred to as a BSY plus red or “BSY+R” system. In such a system, the LED devices used include LEDs operable to emit light of two different colors. In one example embodiment, the LED devices include a group of LEDs, wherein each LED, if and when illuminated, emits light having dominant wavelength from 440 to 480 nm. The LED devices include another group of LEDs, wherein each LED, if and when illuminated, emits light having a dominant wavelength from 605 to 630 nm. A phosphor can be used that, when excited, emits light having a dominant wavelength from 560 to 580 nm, so as to form a blue-shifted-yellow light with light from the former LED devices. In another example embodiment, one group of LEDs emits light having a dominant wavelength of from 435 to 490 nm and the other group emits light having a dominant wavelength of from 600 to 640 nm. The phosphor, when excited, emits light having a dominant wavelength of from 540 to 585 nm. A further detailed example of using groups of LEDs emitting light of different wavelengths to produce substantially while light can be found in issued U.S. Pat. No. 7,213,940, which is incorporated herein by reference.
The various parts of an LED lamp according to example embodiments of the invention can be made of any of various materials. A lamp according to embodiments of the invention can be assembled using varied fastening methods and mechanisms for interconnecting the various parts. For example, in some embodiments locking tabs and holes can be used. In some embodiments, combinations of fasteners such as tabs, latches or other suitable fastening arrangements and combinations of fasteners can be used which would not require adhesives or screws. In other embodiments, adhesives, solder, brazing, screws, bolts, or other fasteners may be used to fasten together the various components.
Although specific embodiments have been illustrated and described herein, those of ordinary skill in the art appreciate that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiments shown and that the invention has other applications in other environments. This application is intended to cover any adaptations or variations of the present invention. The following claims are in no way intended to limit the scope of the invention to the specific embodiments described herein.
This application is a continuation-in-part (CIP) of U.S. application Ser. No. 13/774,193, as filed on Feb. 22, 2013, which is incorporated by reference herein in its entirety, and which is a continuation-in-part (CIP) of U.S. application Ser. No. 13/467,670, as filed on May 9, 2012, which is incorporated by reference herein in its entirety, and which is a continuation-in-part (CIP) of U.S. application Ser. No. 13/446,759, as filed on Apr. 13, 2012, which is incorporated by reference herein in its entirety. This application also claims benefit of priority under 35 U.S.C. §119(e) to the filing date of U.S. Provisional Application No. 61/738,668, as filed on Dec. 18, 2012, which is incorporated by reference herein in its entirety; and to the filing date of U.S. Provisional Application No. 61/712,585, as filed on Oct. 11, 2012, which is incorporated by reference herein in its entirety; and to the filing date of U.S. Provisional Application No. 61/716,818, as filed on Oct. 22, 2012, which is incorporated by reference herein in its entirety; and to the filing date of U.S. Provisional Application No. 61/670,686, as filed on Jul. 12, 2012, which is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61738668 | Dec 2012 | US | |
| 61712585 | Oct 2012 | US | |
| 61716818 | Oct 2012 | US | |
| 61670686 | Jul 2012 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13774193 | Feb 2013 | US |
| Child | 13939821 | US | |
| Parent | 13467670 | May 2012 | US |
| Child | 13774193 | US | |
| Parent | 13446759 | Apr 2012 | US |
| Child | 13467670 | US |
