Patent Application
20090129087
The invention relates generally to light emitting diode type lights and the thermal management of LED type lighting systems.
No federal funds were used to develop or create the invention disclosed and described in the patent application.
Not Applicable
High bay lights are a type of high intensity discharge (HID) light that are suitable for general purpose lighting in areas such as warehouse facilities, assembly areas, gyms, hangars, transportation garages, and loading and staging areas. High bay lights or fixtures of the prior art are typically suitable for indoor applications in which ceiling height exceeds fifteen feet. Typical prior art high bay light fixtures are made by Howard Lighting. They may have a 1000 watt (W) metal halide bulb and a twenty-two inch (22″) aluminum reflector. The die-cast plate is often tapped three-quarter inch nominal pipe size (NPS) and accepts three-quarter inch pipe or a 715NEW die-cast hook for installation and positioning from a rafter or beam. According to the specifications for such lights, they often have a minus forty degrees Fahrenheit minimum starting temperature. The available power sources for such lights are 120, 208, 240, 277 and 480 volts.
U.S. Pat. No. 7,282,869 issued to Mayer et al. (the '869 patent, which is incorporated by reference herein) provides relevant background on other HID lights, of which the present art is intended to replace. HID lamps are used in many applications because of their long life and high efficiency. Principal types of HID lamps are high pressure sodium (HPS), pulse start metal halide (PSMH), and mercury vapor lamps.
Mercury vapor, metal halide, and HPS lamps all operate similarly during stabilized lamp operations. The visible light output results from the ionization of gases confined within an envelope and which must be broken down before there is any flow of ionization current. Accordingly, a high open circuit voltage must be applied to an HID lamp for igniting. This voltage is substantially higher than the operating voltage and the available line voltage. HID lamps also exhibit negative resistance. When operating, their resistance decreases with increase in the applied voltage. As a result, such lamps require an impedance means in their power supply to limit the alternating current flow to a predetermined value.
Because of the high starting or igniting voltage requirement and the negative resistance characteristic, HID lamps are provided with igniting and operating circuits, which provide a relatively high open circuit voltage and impedance means for current limitations. A ballast between the power supply and lamp typically serves as its impedance means in igniting and operating circuits for HID lamps. For HID lamps such as mercury vapor lamps, igniting voltages may be two times the operating voltage. The igniting voltage is generated by the ballast secondary coil winding. For HPS lamps, the required voltages may be more than ten times the operating voltages and more complex igniting mechanisms are employed.
The ballast system also typically provides for certain requirements when electronic igniters are used in conjunction with the HID lamps. For example, electronic igniters used in conjunction with HPS ballast coils produce a high voltage pulse to start the HPS lamp. These electronic igniters work by sensing whether the lamp is burning. If the lamp is not burning, the igniter continuously supplies starting pulses to the lamp, regardless of whether the lamp is not burning because of lamp failure, absence of a lamp in the lamp socket, or by the lamp cycling off.
Lamp cycling is a well-known phenomenon in which a lamp nearing the end of its life will light, turn on for some time, go out, relight, and repeat this cycle time after time until the lamp is replaced or the lamp will fail to start at all. In an HPS lamp, as the HPS lamp nears the end of its life, its lamp operating voltage gets so high that the ballast will no longer sustain operation, and the lamp cycling condition manifests itself.
From the foregoing, it is clear that certain problems may arise in the operation of HID lamps and associated ballasts. In certain situations, (e.g., when a lamp is cycling, failed, or is missing) the igniter in the lamp's HID circuit continues to operate. Such operation shortens igniter and ballast life due to the presence of continuous high voltage pulses that inflict unusual, extended stress on the lighting system. The result of this stress on the ballast transformer may result in burning or smoking, and/or damaged HID lamp fixtures and wiring. Cycling lamps in need of replacement may avoid replacement if the lamp is in an illuminated state when inspected, and thus cause future maintenance problems.
Because many times HID lamps are used in roadway lighting, manufacturing installations with high/inaccessible ceilings, military installations, aircraft hangars, parking lots, tennis courts, athletic arenas and the like, replacement of a failed lamp installation may also be time consuming and require specialized access equipment not always immediately available. Maintenance and operational inspections may be infrequent. Often, replacement of the lamp of a failed lamp installation is the first step. If the lamp is not the cause of the lamp outage, the cause may be a failed igniter or failed ballast or both. The cause may not be determined until the failed element is replaced and operating power is applied.
The lights of the prior art, such as those described in the '869 patent, also require a large amount of energy for the light produced (i.e., HID lights are not energy efficient). Additionally, the light produced may have a yellow tinge that is common for fluorescent-based lights. By contrast, light emitting diodes (LEDs) are efficient at converting electrical energy into light. Furthermore, LEDs may produce a high intensity white light that many users prefer.
The many advantages of LEDs are numerous and well known to those of ordinary skill in the art. LEDs produce more light per watt than do incandescent bulbs. LEDs may emit light of an intended color without the use of color filters that traditional lighting methods require. This is more efficient and may lower initial costs. The solid package of an LED may be designed to focus its light. Incandescent and fluorescent sources often require an external reflector to collect light and direct it in a usable manner. When used in applications where dimming is required, LEDs do not change their color tint as the current passing through them is lowered, unlike incandescent lamps, which turn yellow.
LEDs are ideal for use in applications that are subject to frequent on-off cycling, unlike fluorescent lamps that burn out more quickly when cycled frequently, or HID lamps that require a significant time before restarting. LEDs, being solid state components, are difficult to damage with external shock. Fluorescent and incandescent bulbs are easily broken if dropped on the ground. LEDs have an extremely long life span. One manufacturer has calculated the ETTF (Estimated Time To Failure) for their LEDs to be between 100,000 and 1,000,000 hours. Fluorescent tubes typically are rated at about 30,000 hours, and incandescent light bulbs at 1,000-2,000 hours. LEDs mostly fail by dimming over time rather than the abrupt burn-out failing associated with incandescent bulbs. LEDs light up very quickly. A typical red indicator LED will achieve full brightness in microseconds; LEDs used in communications devices may have even faster response times.
LEDs may be very small and are easily populated onto printed circuit boards (PCB). LEDs do not contain mercury, while compact fluorescent lamps do. However, before the creation and disclosure of the present art, it has not been economical nor practical to use LEDs in combination with a high bay light fixture for replacement of HID lights or fixtures. LEDs are known to produce a significant amount of heat during operation, and methods of thermal management of LEDS are lacking. This heat lowers the efficiency of light generation, thereby increasing power use and costs. Furthermore, the ambient temperature of the air surrounding the light fixture may decrease overall energy efficiency of the structure in which the fixture is located. Optical drift (i.e., deterioration of the quality of the light produced) is another result of the heat produced by the prior art configurations of LEDs. A method of thermal managing LED lighting systems is desirable as is an HID composed of LEDs.
In order that the advantages of the invention will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limited of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings.
Before the various embodiments of the present invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that phraseology and terminology used herein with reference to device or element orientation (such as, for example, terms like “front”, “back”, “up”, “down”, “top”, “bottom”, and the like) are only used to simplify description of the present invention, and do not alone indicate or imply that the device or element referred to must have a particular orientation. In addition, terms such as “first”, “second”, and “third” are used herein and in the appended claims for purposes of description and are not intended to indicate or imply relative importance or significance.
An LED light fixture 10 in accordance with the present disclosure is shown in
The amount and pattern of illumination produced during operation of the LED light fixture 10 may be tailored to the specific application for the LED light fixture 10 by means known to those skilled in the art. For example, different lenses (not shown) may be affixed to the housing 12 and used to direct the light in a certain pattern, and the amount of total illumination produced by the LED light fixture 10 may be predetermined by the number and intensity of LEDs 40 used in the LED light fixture 10, as well as the specific arrangement thereof. If a lens (not shown) is used, it may be configured to concentrate the light from the LEDs 40, to spread that light, or to manipulate that light in any other manner known to those skilled in the art. Furthermore, the color and quality of the light emitted by the LED light fixture 10 may be varied through the use of different LEDs 8, as is known to those skilled in the art. Accordingly, the LED light fixture 10 is not limited by the type of LED 40 used, and any LED 40 known to those skilled in the art may be used therewith out departing from the spirit and scope of the present invention. For example, the LED light fixture 10 may be configured to produce light that is bright and white, not yellow, as is common with prior art lighting systems. In another embodiment, the LED light fixture 10 may be configured to produce red or blue light, depending on the type of LED 40 used. The LED light fixture 10 provides for increased efficiency by increasing the amount of power converted to light, as compared to a typical HID light using metal halide or mercury vapor bulbs. Furthermore, the LED light fixture 10 configuration virtually eliminates optical drift during operation.
In the exemplary embodiment of the LED light fixture 10 as shown in the various figures, the LED light fixture 10 includes a housing 12 enclosing a portion of the internal components. A switched mode power supply 15 is mounted externally to the housing 12 to better mitigate heating caused by the switched mode power supply 15. However, in other embodiments the power supply may be mounted internally of the housing 12. In the exemplary embodiment, the switched mode power supply 15 is a Mean Well, brand model ASP-150 series, which is a 150 watt single output with PFC function. A wire 16 may be used to provide electrical energy from an electrical energy source to the switched mode power supply 15. As illustrated, and without limitation, the exemplary embodiment of the LED light fixture 10 as shown herein is for use with alternating current (AC) supplied at 50-60 Hz and 98-230 VAC. As those of ordinary skill in the art will appreciate, the present art may use other voltages, frequencies, and/or currents without limitation. A hanger 18 may be placed on the exterior of the housing 12 for mounting the LED light fixture 10.
The housing 12 typically functions to protect and support the circuitry of the LED light fixture 10. A portion of the printed circuit board (PCB) 20 for use with the exemplary embodiment is shown in
The PCB 20 of the exemplary embodiment, shown from various vantages in
A power conductive pathway 30 may be electrically connected to the switched mode power supply 15 through a power connection 31a, which is best shown in
The entire PCB 20 from the exemplary embodiment is shown in
In the exemplary embodiment, each LED circuit 44 includes six LED pads 34, one resistor pad 36, one resistor 50, and seven LEDs 40, which yields a total of one hundred twenty six LEDs 40 per LED board section 46 in the exemplary embodiment. Each LED 40 and resistor 50 require two electrical lead apertures 26. Accordingly, the total number of LEDs 40 attached to the PCB 20 in the exemplary embodiment is three hundred seventy eight. A schematic illustration of the exemplary embodiment of an LED circuit 44 is shown in
A cross-sectional view of a portion of the PCB 20 is shown in
Adjacent the resistor pad 36 is an LED pad 34 having two electrical lead apertures 26; one adjacent the resistor pad 36 and one adjacent another LED pad 34. In the exemplary embodiment, the LED pad 34 of each LED circuit 44 that is located adjacent the resistor pad 36 is shaped differently from the other LED pads 34 in the LED circuit 44. However, the shape of the LED pads 34, resistor pads 36, power conductive pathways 30a, and ground conductive pathways 30b is in no way limiting, and may be different in embodiments not pictured herein depending on the specific application of the LED light fixture 10. The LED pad 34 adjacent the resistor pad 36 is electrically connected to the resistor pad 36 through an LED 40. As shown in
Another LED 40 electrically connects the LED pad 34 adjacent the resistor pad 36 to an LED pad 34 on the opposite side of the LED pad 34 adjacent the resistor pad 36, which is best shown in
In the exemplary embodiment, the LED leads 42 are positioned on the PCB second side 24 and the bulb is positioned on the PCB first side 22. However, in other embodiments the LED leads 42 may be placed on the PCB first side 22. The PCB second side 24 of the exemplary embodiment with the LEDs 40 and resistors 50 installed thereon is shown in
In other embodiments not shown herein, the LEDs 40 may be electrically connected in a different manner that results in a different configuration, or they may be electrically connected in the same manner with a different configuration. For example, the LEDs 40 of each LED circuit 44 may be electrically connected to one another in series, but be configured in a curved or other non-linear manner. The LEDs 40 may also be electrically connected in parallel, but be configured in a curved or linear manner without departing from the spirit and scope of the present invention.
In the exemplary embodiment, the LEDs 40 are sold by BestHongKong under the part number BUWC5363W55BC26, ultra white in color, designated as 5363 10 mm Series 5 Chips Round LED Lamps. These LEDs 40 have a maximum peak forward current of 200 mA, a maximum DC forward voltage of 4.0 V, a maximum intensity luminous of 18,000 mcd, and a maximum color temperature of 10,000K. However, the LED light fixture 10 and PCB 20 may be configured to be used with any type of LED 40 known to those skilled in the art. The specifications of the LEDs 40 to be used with the present invention will depend on several factors, and will vary from one application to the next.
In the exemplary embodiment, three thermal vias 28 are positioned adjacent each LED 40 nearest the resistor pad 36 in each LED circuit 44, three thermal vias 28 are positioned adjacent each LED 40 nearest the ground conductive pathway 30b, and six thermal vias 28 are positioned adjacent the remaining LEDs 40 in each LED circuit 44. Each thermal via 28 extends from the PCB first side 22 through the PCB substrate 21 to the PCB second side 24. In this manner, the thermal vias 28 allow for fluid flow from the PCB first side 22 to the PCB second side 24 and vice versa, which dissipates heat generated through operation of the LED light fixture 10. Typically, the fluid will be air, but it may be any gas, vapor, liquid, or other fluid as the heat removal from the specific configuration of the PCB 20 requires, which will be dependent on design, as is well known to those skilled in the art. As shown in
Each thermal via 28 is coated with a plating 38 that is in thermal conductive communication with the LED pad(s) 34 and/or resistor pad(s) 36 in which the thermal via 28 is located, which is best shown in
It is envisioned that the design of an LED light fixture 10 according to the present disclosure will begin with determining the luminosity requirements and space restraints for the LED light fixture 10. After this, a PCB of adequate physical size and electrical capacity will be designed for an LED 40 having certain specifications. Next, a mathematical model may be used to predict the locations of the PCB 20 that will have the highest amount of thermal energy. Another mathematical model may then be used to predict the heat transfer resulting from a certain number of thermal vias 28 having a certain size positioned in a certain location. These parameters may then be adjusted until the PCB 20 possesses the desired thermal gradient. A thermal map of one LED pad 34 (one which is not positioned on either respective end of an LED circuit 44) from the exemplary embodiment is shown in
As will be apparent to those skilled in the art in view of the present disclosure, the power and ground conductive pathways 30a, 30b, LED pads 34, and resistor pads 36 are configured to maximize the ratio of surface area to mass of those respective components, which increases the heat dissipation efficiency of the PCB 20. Other configurations exist for embodiments not pictured herein, and such configurations will be dependent on the particular application for each LED light fixture 10. In certain embodiments, it is envisioned that the energy requirements for the LED light fixture 10 will be greater than that of the exemplary embodiment, in which case the power and ground conductive pathways 30a, 30b, LED pads 34, resistor pads 36, plating 38, and or LEDs 40 would be designed to withstand a larger load than those respective components in the exemplary embodiment. In other embodiments not picture herein, it is envisioned that the energy requirements for the LED light fixture 10 will be less than that of the exemplary embodiment, in which case the components listed above would be designed to withstand a lower load than those respective components in the exemplary embodiment.
A method for constructing the exemplary embodiment will now be disclosed. However, the description that follows describes merely one method of many possible methods for making merely one exemplary embodiment of many possible embodiments of the invention, and is not therefore to be considered limiting as to the scope of the invention as disclosed and claimed herein.
After the space considerations and luminosity requirements have been determined, the configuration of LED pads 34, resistor pads 36, and power and ground conductive pathways 30a, 30b on the PCB first and second sides 22, 24 must be achieved, which will also determine the configuration of the LEDs 40. In the exemplary embodiment, this is accomplished by starting with a blank PCB 20 having a layer of electrically conductive material bonded to the PCB substrate 21 on both the PCB first and second sides 22, 24. The unwanted conductive material is removed and the LED pads 34, resistor pads 36, power conductive pathways 30a, and ground conductive pathways 30b are left, all of which are oriented according to the desired configuration and luminosity requirements for the LEDs 40. The unwanted conductive material may be removed from the PCB first and second sides 22, 24 through any method known to those skilled in the art, such as etching, milling, or any other method known to those skilled in the art. In other embodiments not pictured herein, the conductive pathways 26 may be made by adding conductive pathways 26 to a PCB substrate 21.
Next, or concurrently with removing unwanted conductive material, a plurality of apertures are fashioned in the PCB 20. These apertures extend from the PCB first side 22 through the PCB substrate 21 to the PCB second side 24. The number of apertures will depend upon the configuration of the LED light fixture 10. Each LED 40 in the exemplary embodiment requires two electrical lead apertures 26, as does each resistor 50. Each power and ground connection 31a, 31b also require an aperture, as does each thermal via 28. As previously explained, the number of LEDs 40 and thermal vias 28 for each LED light fixture 10 will vary depending on the specific application and design requirements.
The optimal number and placement of thermal vias 28 may be determined for any given configuration of LEDs 40 having known specifications using calculations known to those skilled in the art, as was described above. After a configuration of LEDs 40 has been determined (which is often performed prior to or concurrently with determining the configuration of the conductive material on the PCB first and second sides 22, 24), a heat profile may be estimated and thermal vias 28 may be fashioned on the PCB 20 in the areas having the highest projected temperature.
A solder mask may also be placed on the PCB first and second sides 22, 24 to protect the conductive material from the atmosphere. However, solder mask should not be positioned at any area of the PCB 20 that will later serve as an electrical connection or on the sides of any aperture in the PCB 20 that is designed to function as a thermal via 28. That is, solder mask is typically not placed on any area of the PCB 20 that will be coated with plating 38.
A thermally conductive plating 38 is then deposited on the PCB 20. The plating 38 is typically positioned on any portion of the PCB 20 that has not been covered by the solder mask. This may include portions of the PCB 20 adjacent electrical lead apertures 26 and the walls of electrical lead apertures 26, portions of the PCB 20 adjacent thermal vias 28 and the walls of thermal vias 28, and portions of the PCB 20 adjacent power and ground connections 31a, 31b and the walls thereof. Accordingly, in the exemplary embodiment the walls of the thermal vias 28, the ground and power connections 31a, 31b, and the walls of the electrical lead apertures 26 are covered with the plating 38. In the exemplary embodiment, this plating 38 is in electrical and thermal communication with the LED pad 34 or resistor pad 36 in which the thermal via 28 is positioned.
In this manner, the heat associated with operating the adjacent LED 40 may be thermally conducted to the thermal via 28 through the LED pad 34. From the thermal via 28, natural convection works in the exemplary embodiment to transport the heat from the thermal via 28 to the ambient atmosphere. In other embodiments, the plating 38 may be thermally conductive but not electrically conductive, and different plating 38 may be used on different elements of the PCB 20.
In experiments using the exemplary embodiment of an LED light fixture 10 as pictured herein, Applicant has measured a marked decrease in the operating temperature of the PCB 20. In identically configured LED light fixtures 10 using identical components, the average PCB 20 temperature for the LED light fixture 10 without thermal vias 28 was 148 degrees Fahrenheit after four hours of continuous operation; the average PCB 20 temperature for the LED light fixture 10 with thermal vias 28 was 120 degrees Fahrenheit after 10 hours of continuous operation.
An infinite number of electrical arrangements for the LED board sections 46, LED circuits 44, LED pads 34, resistor pads 36, power and ground conductive pathways 30a, 30b, and/or individual LEDs 40 within each LED circuit 44 are available to those skilled in the art within the spirit and scope of the present invention. For example, in certain applications the LED board sections 46 may be electrically connected in series rather than in parallel, as may be the LED circuits 44 within each LED board section 46 or individual LEDs 40 within each LED circuit 44. Accordingly, the precise electrical arrangement and/or configuration of the electrical lead apertures 26, thermal vias 28, power conductive pathways 30a, ground conductive pathways 30b, power connections 31a, ground connections 31b, non-conductive areas 32, LED pads 34, resistor pads 36, LEDs 40, LED circuits 44, LED board sections 46, and/or resistors 50 in no way limit the scope of the present invention.
In the exemplary embodiment as pictured herein, the power and ground conductive pathways 30a, 30b, LED pads 34, and resistor pads 36 are formed from copper traces, but may be any material known to those skilled in the art that is suitable for the specific application of the LED light fixture 10. For example, in other embodiments the various elements listed directly above may be formed of conductive polymers, other conductive metals, or any other material known to those skilled in the art that is suitable for the specific application of the LED light fixture 10.
The plating 38 used to coat the power connections 31a, ground connections 31b, thermal vias 28, and electrical lead apertures 26 may be any suitable plating 38 known to those skilled in the art suitable for the particular application of the LED lighting fixture 10. The exemplary embodiment uses tin for the plating 38, but gold, silver, or other materials may be used within the scope of the present invention. Furthermore, different plating 38 may be used for different elements. For example, in an embodiment not pictured herein, tin may be used for the plating 38 on the electrical lead apertures 26, gold may be used for the plating 38 of the thermal vias 28, etc.
The LED lighting fixture 10 is applicable to an infinite number of design configurations for an infinite number of applications without departing from the spirit and scope of the present disclosure. For example, the use of thermal vias 28 to cool the PCB 20 may be employed for LED lighting fixtures 10 used in automobile lights, traffic signal lights, high bay lights, flashlights, or any other application. The voltage and amperage of the power supply, number of LEDs 40, configuration of LEDs 40 on the PCB 20, and presence of a lens (not shown) and/or lens type are design considerations, whereas the placement, size, configuration, and existence of thermal vias 28 is directed to heat dissipation.
It should be noted that the present invention is not limited to the specific embodiments pictured and described herein, but is intended to apply to all similar apparatuses for lighting systems having LEDs therein or any similar methods for dissipating heat from PCBs 20. Modifications and alterations from the described embodiments will occur to those skilled in the art without departure from the spirit and scope of the present invention.
Applicant claims priority under 35 U.S.C. § 119(e) of provisional U.S. Patent Application Ser. No. 61/003,216 filed on Nov. 15, 2007, which is incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 61003216 | Nov 2007 | US |
