Patent Application
20140293603
The invention relates to lighting systems and, in particular, to a light emitting diode (LED) retrofit for an incandescent or fluorescent light bulb.
Various embodiments may include a light emitting diode (LED) light bulb replacement apparatus that may include a plurality of circuit boards or chip on board modules (or COB modules) upon which LEDs may be mounted, a multi-sided heat sink with internal fins, wherein one or more circuit boards or chip on board modules may be mounted on one or more sides of the heat sink, the heat sink being arranged about an axis with the fins on the heat sink facing the axis to allow convective air flow across the fins, an airflow cavity defined by a volume around the axis and inside the fins of the heat sink, and opposite ends of the axis being open to enable airflow through the airflow cavity along the fins of the heat sink. In some embodiments, the internal fins may be ribbed to increase a surface area of the fins without significantly impeding an air flow cross-sectional area. In some embodiments, the heat sink may be attached to one of a plurality of interchangeable mechanical bases that can be mounted in or on legacy light sockets, and the interchangeable mechanical bases have arms mounting to the heat sink that do not significantly block air flow through the airflow cavity. In some embodiments, the LEDs may be mounted on the plurality of circuit boards, and a total number of the circuit boards on each side of the heat sink may be adjusted to approximate an ideal light distribution. In some embodiments, the LEDs may be mounted on the plurality of the chip on board (COB) modules. In some embodiments, the heat sink being attached to one of a plurality of interchangeable mechanical bases that can be screwed into legacy light sockets, a rotational orientation of the heat sink relative to a light fixture being adjustable by a set screw, a total number of LED circuit boards being adjusted by a parallel output connector and cutting a length of the heat sink, and a light distribution in a plane orthogonal to the axis being adjusted by mounting the plurality of circuit boards or chip on board modules symmetrically or asymmetrically on the one or more sides of the heat sink. In some embodiments, the light distribution in the plane containing the axis may be adjusted by an array of reflective flaps with adjustable angles, and wherein the array of reflective flaps may be positioned such that each flap in the array of reflective flaps reflects a substantial amount of rays from a single LED. In some embodiments, the light distribution in the plane containing the axis may be adjusted by a plurality of lenses positioned such that each lens focuses a substantial amount of rays from a single LED, and each lens has a different mounting orientation relative to the LEDs.
In other embodiments, a light emitting diode (LED) light bulb replacement apparatus may include a plurality of circuit boards or chip on board modules upon which LEDs may be mounted, and an array of reflective flaps mounted over the plurality of circuit boards or chip on board modules such that each flap reflects a significant portion of rays from one or more LEDs towards an illumination area, wherein an angle and a shape of each reflective flap can be adjusted to control a distribution of reflected rays reflected by the each reflective flap.
In other embodiments, a light emitting diode (LED) light bulb replacement apparatus may include a plurality of circuit boards or chip on board modules upon which LEDs may be mounted, and a plurality of directional lenses with each lens mounted over the plurality of circuit boards or chip on board modules so as to direct a substantial amount LED light rays in a preferred direction, wherein the mounting of the lenses may be adjustable so that more than one preferred direction can be achieved by mounting the lenses with more than one orientation.
The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate exemplary embodiments of the invention, and together with the general description given above and the detailed description given below, serve to explain the features of the invention.
Various embodiments will be described in detail with reference to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. References made to particular examples and implementations are for illustrative purposes, and are not intended to limit the scope of the invention or the claims.
The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations.
Background Terminology
The invention described here provides means of controlling the light distribution of an LED retrofit that replaces the legacy lighting technology in a lighting fixture or luminaire. As such certain terminology is used. The lux is a measure of illuminance and luminous emittance set by the International System of Units (“SI”) described in terms of luminous flux per unit area. One lux is equal to one lumen per square meter.
The candela is an SI defined unit of luminous intensity; that is, power emitted by a light source in a particular direction, weighted by the “luminosity function.” The luminosity function is a standardized model of the sensitivity of the human eye to different wavelengths, sometimes also called the luminous efficiency function. A common candle emits light with a luminous intensity of roughly one candela. If an opaque barrier blocks emission in a direction, the emission is still approximately one candela in the directions that are not obscured.
The lumen is an SI derived unit of luminous flux, a measure of the total “amount” of visible light emitted by a source. Luminous flux differs from power (radiant flux). Luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light, while radiant flux measurements indicate the total power of all light emitted, independently from the eye's ability to perceive it. The lumen is defined in relation to the candela as 1 lumen equals=1 candela steradian. Because a sphere has a solid angle of 4·π steradians, a light source that uniformly radiates one candela in all directions has a total luminous flux of 1 cd·4π sr=4π≈12.57 lumens.
In this application “LED lightbulb replacement” and “LED retrofit” are used interchangeably to indicate the apparatus that replaces the lightbulb inside a lighting fixture.
It is desirable to upgrade currently installed incandescent and compact fluorescent light bulbs to LED lights for several reasons: (1) efficiency—LED technology delivers more lumens per Watt than other lighting technologies so that the same illumination can be obtained with significantly lower power consumption; (2) reliability—LED technology has statistically much longer lifetimes than other technologies so that it requires fewer hardware replacements and lower maintenance costs; (3) directionality—as a point source, it is easier to direct LED light with lenses and reflectors so that the light can be concentrated on the desired illumination area and excluded from areas where it is not desired; and (4) adjustability—LED light levels can be dimmed, and colors can be controlled via software and hardware controls.
Prior art examples of LED lighting include the following. U.S. Pat. No. 8,646,944 describes a standalone LED luminaire for achieving a desired illumination pattern where LED panels are rotatable in at least two dimensions. US 2013/0250575 describes a linear LED lens array that can be used to direct light towards an illumination area. US 2012/0281405 describes a low-glare LED luminaire with translucent lenses. U.S. Pat. No. 8,496,360 describes an LED luminaire that uses a combination of lenses and a reflector to direct light towards an illumination area. U.S. Pat. No. 8,403,533 describes an LED module that can be rotated along one axis to point the light towards an illumination area. U.S. Pat. No. 8,534,867 describes an LED luminaire that uses an array of parabolic reflectors to direct the light towards an illumination area.
Many lighting customers that want to take advantage of LED technology also want to keep the legacy lighting fixture so as to reduce cost, reduce waste, and maintain the architectural integrity of decorative fixtures. Therefore, there is demand for LED products that retrofit the lightbulb within the fixture while re-using the outer fixture.
Conventional lighting uses omnidirectional bulbs with reflectors and/or refractors to direct the light from the bulb in the desired illumination distribution. LED luminaire manufactures design luminaires for a given light distribution (1) by orienting the LEDs in the desired direction or (2) by adding lenses with the required light distribution. These designs can direct the LED light in the required direction, but if a different direction is required a different product must be ordered. Also, when the prior art luminaires are installed, the light distribution cannot be adjusted on site. It would be desirable to provide a single fixture that is adjustable on site to meet the needs of the site depending on the type of lighting distribution, pole spacing, and mounting height.
LEDs convert electrical energy into light, but with undesired heat (albeit in a smaller quantity than incandescent light bulbs). The power supply for the LED, which typically converts incoming alternating current power to direct current, also creates heat. The LED power supplies are typically 80% to 90% efficient, with the remaining 10-20% of incoming energy converted to heat. The excess heat generated by the LEDs and the power supply reduces the light output and product lifetime. To limit the temperature increase, LED luminaires typically use a passive heat sink with fins that are convection cooled by the surrounding air as it flows over the fins. In some installations, however, the LED assembly operates in an enclosed fixture, for example, a post top luminaire. In these installations there is limited airflow because the air is constrained inside the cover of the luminaire. In these installations the excess heat is transferred from the LEDs and the heat sink to the air, then from the air to the luminaire cover or base, and finally from the cover or base to the outside air. One well-known method of improving heat transfer is to place a fan inside the luminaire to circulate the air. Because of the additional component, use of a fan can potentially reduce the lifetime of the LED/fan combination. In some installations the noise generated by the fan is undesirable. The fan also adds extra cost as a result of the fan and its power supply. Furthermore, in some installations the size of the fan limits the deployment to applications where the luminaire is large enough to contain the additional components.
To minimize inventory and lower manufacturing costs by using component parts in high volume, there is therefore a need for an LED lightbulb retrofit that can be (a) adjusted for both top-socket and bottom-socket applications, (b) adjusted to generate a variety of IESNA illumination distributions, (c) adjusted to different levels of total lumens, (d) adjusted to mount to different sockets such as medium and mogul bases, and (e) adjusted to work in both refractors and globes. The retrofit must have good thermal design so as to enhance the natural convection flow within the fixture to maintain the LED and power supply temperatures at acceptable levels.
Various methods and apparatus of the embodiments of the invention relate to an LED light bulb replacement that can be installed in various lighting fixtures while providing adjustable output light distribution so as to optimize the light distribution with regards to the retrofitted lighting fixture, mounting height, pole spacing, and illumination area.
This invention discloses an apparatus for replacing conventional light bulb with LED-based retrofits. LED chips are mounted on printed circuit boards (PCBs) that are mounted on an extruded aluminum heat sink. The heat sink has an enclosed chimney area with fins located in a cavity about a central axis so that the air enters from below and rises to the top of the cavity by natural convection. The heat sink has a two-dimensional extrusion profile that can be cut to different lengths so that a different number of PCBs can be mounted to provide different lumen levels. Different numbers of PCBs can be mounted on different sides of the heat sink so as to provide the different categories of lighting distributions. The PCB design has connectors and traces designed so that the PCBs can be connected in parallel to one or more constant-current direct-current power supplies (henceforth referred to as “drivers”). To improve thermal performance, the driver is mounted separately from the LED heat sink in a plastic holder. Interchangeable bases enable the same retrofit to be mechanically mounted in different conventional sockets such as the standard Medium E26 socket or the mogul E39 socket. For asymmetrical distributions, a set screw in the mechanical base enables the retrofit to be oriented along a desired direction.
In one embodiment, an array of flexible reflectors stamped in a metal sheet is placed on top of the LED PCBs so as to reflect the light towards the illumination area in an adjustable manner. In another embodiment, reversible lenses that are placed on top of each LED also provide a means of adjusting the light distribution relative to the mounting socket. The number of LEDs on the circuit boards is chosen to match the direct-current voltage from the power supply.
The embodiment features may include one or more of a heat sink with fins in the middle, ribs on the heat sink, single extrusion cut to different lengths for different amounts of total lumens, PCBs connected in parallel with cascade connector, flaps with different angles, tool to adjust the flap angle, curved flaps, selective placement of LED board to get different light distributions, adjustment screw to set orientation vs. the street side, lenses and flaps can be flipped around for post top and pendant, interchangeable bases for different socket types, vertical heat sink with downwards light, low glare from many low-power LEDs (reflector instead of lens), slots on the heat sink so that drilling/tapping is not required, and driver caddy, mounted separate from the LEDs.
In various embodiments described herein, ribbed fins of heat sinks may increase a surface area without significantly impeding or blocking air flow. Additionally, in various embodiments, mechanical bases having arms mounted to a heat sink as described herein may not significantly impede or block air flow through an airflow cavity defined by a volume about an axis and inside the fins of such a heat sink. For the purpose of this disclosure, such substantially impeding (or a substantial impedance) may be considered an increase to impedance greater than 10% (e.g., embodiments may only increase impedance less than 10%). Further, various embodiments may include adjusting circuit boards on the sides of heat sinks to approximate an ideal light distribution. For the purpose of this disclosure, such an approximate may be considered to be within 10% of an ideal light distribution.
Although the exemplary descriptions of this disclosure may refer to metal heat sinks fabricated by an extrusion method, it should be appreciated that heat sinks may be fabricated by other methods, such as stamping or die casting, and thus the embodiments are not intended to be limited to heat sinks fabricated by extrusion fabrication methods.
The extrusion profile of the hexagonal heat sink is shown in
Dashed lines in
The selection of number of LEDs per PCB and type of LED depends on the required total lumens from the retrofit. For example, if the required retrofit has a minimum target of 3000 lumens, then the LEDs in one PCB for a six-sided heat sink must generate at least 500 lumens. This can be met with three high-power LEDs of approximately 200 lumens each, or eighteen medium-power LEDs of approximately 30 lumens each. Lower lumens per LED can be preferred to reduce glare, but higher lumens per LED can be preferred to reduce cost, especially when the design uses one lens per LED. In either case, the driver is selected so that the net voltage drop across the LEDs falls within the output voltage range of the driver.
Although the reflector arrays reduce the amount of up light and provide a means of adjusting the vertical light distribution, there are embodiments that do not use the reflectors. For example, in decorative post top globes there may be a desire to evenly illuminate the globe so that reflectors are not required.
For the exemplary case of the pendant LED retrofit 21 with the pendant reflector array 23, the polar plot of
The invention can also be adjusted to produce different horizontal lighting distributions as defined in
During installation, the LED retrofit for a Type III distribution must be rotated so that the designated street side of the retrofit is oriented towards the street. When the threaded base 409 is screwed into the luminaire socket, the street side of the retrofit will not necessarily end up facing the street. To provide this adjustment, an adjustment screw 90 is inserted at the base of the socket as shown in
The embodiment illustrated in
Another means of directing the light to the illumination area is directional lenses as shown in
Those skilled in the art will recognize that the scope of the invention is not limited to the examples presented. For example, a hexagonal extrusion profile was presented but similar results can be obtained with other shapes, such as a heptagon. Similarly, although the exemplary LED PCBs have eighteen or four LEDs per PCB, PCBs with a different number of LEDs will provide similar results. Furthermore, the presented examples are based on a driver that shares its current with PCBs connected in parallel, whereas the PCBs can also be connected in series. The exemplary embodiments were simplified with PCBs holding only LEDs and connectors, adding other circuitry to the PCBs does not depart from the scope of the invention. The exemplary embodiments disclose the case where the Edison socket is used for mechanical mounting only, but the scope of the invention also covers the case where the socket is also used to provide electrical power to the LEDs with power conversion circuitry on the LED PCBs or other PCB attached to the LED retrofit. The exemplary reflector array has flaps with a flat, angled geometry; the flaps can also have a curved geometry as a means of further controlling the light distribution. For example, a curved flap with a parabolic shape can be used to collimate the light towards a target angle.
The preceding description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the following claims and the principles and novel features disclosed herein.
The present application claims the benefit of priority to U.S. Provisional Application No. 61/805,595, entitled “LED Light Bulb Replacement with Adjustable Light Distribution,” filed Mar. 27, 2013, and U.S. Provisional Application No. 61/805,645, entitled “Natural Convention Cooling of LED Luminaires,” filed Mar. 27, 2013, the entire contents of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61805595 | Mar 2013 | US | |
| 61805645 | Mar 2013 | US |
