US20150009688A1 - Light sources incorporating light emitting diodes - Google Patents

Abstract

Taught herein are various light sources using light emitting diodes. A light source includes a housing, a connector configured for connection to an electrical socket and coupled to an end of the housing, at least one organic light emitting diode sheet mounted inside the housing and in electrical communication with the connector, and a power supply circuit for supplying electrical current to the at least one organic light emitting diode through the connector.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This Application is a continuation of U.S. patent application Ser. No. 13/836,825, filed Mar. 15, 2013, which is a divisional of U.S. patent application Ser. No. 12/242,033, filed Sep. 30, 2008, now U.S. Pat. No. 8,482,212, issued Jul. 9, 2013, which is a continuation of Ser. No. 11/007,417, filed Dec. 8, 2004, now U.S. Pat. No. 8,093,823, issued Jan. 10, 2012, which is a continuation-in-part of U.S. patent application Ser. No. 09/782,375, filed Feb. 12, 2001, now U.S. Pat. No. 7,049,761, issued May 23, 2006, which claims priority to provisional Application Ser. No. 60/181,744, filed Feb. 11, 2000.
FIELD OF THE DISCLOSURE
• The present invention relates to light sources incorporating light emitting diodes.
BACKGROUND
• All lighting systems have shortcomings. Conventional fluorescent lighting systems include, for example, light sources such as fluorescent light tubes and ballasts. Fluorescent lighting systems are used in a variety of locations, such as buildings and transit buses, for a variety of lighting purposes, such as area lighting or backlighting. Such systems have some advantage over incandescent lighting systems, which include light sources such as light bulbs incorporating filaments. Fluorescent lighting systems, for example, generate less heat. On the other hand, the light generated by fluorescent lighting systems is less desirable in many applications than incandescent lighting systems because conventional fluorescent lighting systems generally produce a cooler light that has more blue and less red than incandescent lighting systems. Conventional fluorescent and incandescent lighting systems can also include fragile components. Fluorescent light tubes, in particular, have a short life expectancy, are prone to fail when subjected to excessive vibration, consume high amounts of power, require a high operating voltage and include several electrical connections that reduce reliability. Conventional ballasts are highly prone to fail when subjected to excessive vibration.
BRIEF SUMMARY
• The present invention includes replacements for conventional light sources such as fluorescent light tubes and incandescent light bulbs that overcome the disadvantages of the prior art. Specifically, the invention comprises various light sources incorporating light emitting diodes. Light emitting diodes can be manufactured that have superior color rendering than most fluorescent lamps, which improves the usability and aesthetic qualities of the light. In addition, light emitting diodes are less fragile than incandescent and fluorescent lighting components.
• A first embodiment of the light source according to the present invention comprises a housing portion, a connector disposed at an end of the housing portion, at least one organic light emitting diode sheet surrounded by at least a portion of the housing portion, the at least one organic light emitting diode sheet in electrical communication with the connector, and a power supply circuit for supplying electrical current to the at least one organic light emitting diode sheet through the connector. The housing portion can comprise a rigid hollow bulb made of glass or plastic, for example, or can comprise a clear or tinted potting material or a thin conformal coating. The organic light emitting diode sheet(s) can be flexible. Other variations of this embodiment are possible and are described in more detail herein.
• A second embodiment of the light source according to the present invention comprises a housing portion formed of a coating material, a connector disposed at an end of the housing portion, a plurality of light emitting diodes surrounded by the housing portion and mounted on a circuit board, the plurality of light emitting diodes electrically coupled to the connector, and a power supply circuit for supplying electrical current to the plurality of light emitting diodes, the power supply circuit electrically coupled to the connector. The coating material can be a clear or tinted potting material or can be a thin conformal coating for the circuit board and light emitting diodes. At least part of the power supply circuit can be mounted on the circuit board. Other variations of this embodiment are also possible and are described in more detail herein.
• A second embodiment of the light source according to the present invention comprises a connector adapted to be coupled to an electrical socket, a circuit board extending from the connector, at least one light emitting diode mounted on the circuit board and in electrical communication with the connector, the at least one light emitting diode exposed to an ambient environment external of the light source, and a power supply circuit for supplying electrical current to the at least one light emitting diode through the connector.
• Other embodiments are described in more detail herein.
BRIEF DESCRIPTION OF THE DRAWINGS
• The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:
• FIG. 1 is a line drawing showing a light tube, in perspective view, which in accordance with the present invention is illuminated by LEDs packaged inside the light tube;
• FIG. 2 is a perspective view of the LEDs mounted on a circuit board;
• FIG. 3 is a cross-sectional view ofFIG. 2 taken along lines3-3 with the addition of optional heat sinks;
• FIG. 4 is a fragmentary, perspective view of one embodiment of the present invention showing one end of the light tube disconnected from one end of a light tube socket;
• FIG. 5 is an electrical block diagram of a first power supply circuit for supplying current to power a light source incorporating LEDs;
• FIG. 6 is an electrical schematic of a switching power supply type current limiter;
• FIG. 7 is an electrical block diagram of a second power supply circuit for supplying current to power a light source incorporating LEDs;
• FIG. 8 is an electrical block diagram of a third power supply circuit for supplying current to power a light source incorporating LEDs;
• FIG. 9 is a fragmentary, perspective view of a second embodiment of the present invention showing one end of a light tube disconnected from one end of the light tube socket;
• FIG. 10 is an electrical block diagram of a fourth power supply circuit for supplying current to power a light source incorporating LEDs;
• FIG. 11 is a fragmentary, perspective view similar toFIG. 4 showing another embodiment of the circuit board;
• FIG. 12 is a line drawing showing a light bulb, in perspective view, which in accordance with the present invention is illuminated by LEDs packaged inside the light bulb;
• FIG. 13 is a cross-sectional view ofFIG. 1 taken along lines13-13;
• FIG. 14 is a perspective view of a sheet comprising an organic light-emitting diode that can be incorporated into the light sources of the present invention; and
• FIG. 15 is an end view of a light tube omitting the end cap and electronics and incorporating an organic light-emitting diode.
DETAILED DESCRIPTION
• FIG. 1 is a perspective view showing a light source according to the invention in the form of alight tube20. In accordance with a first embodiment of the invention, thelight tube20 is illuminated byLEDs22 packaged inside thelight tube20. Thelight tube20 includes a cylindricallyshaped housing portion24 having a pair ofend caps26 and28 disposed at opposite ends of thehousing portion24. Preferably, thehousing portion24 is made from a transparent or translucent material such as glass, plastic, or the like. As such, the housing material may be either clear or frosted.
• In a preferred embodiment of the present invention, thelight tube20 has the same dimensions andend caps26 and28 (e.g., electrical male bi-pin connectors, type G13) as a conventional fluorescent light tube. As such, the present invention can be mounted in a conventional fluorescentlight tube socket40 as shown inFIG. 4.FIG. 4 is a fragmentary, perspective view of one embodiment of the present invention showing one end of thelight tube20 disconnected from one end of alight tube socket40. Similar to conventional fluorescent lighting systems and in this embodiment of the present invention, thelight tube socket40 includes a pair of electricalfemale connectors42 and thelight tube20 includes a pair of matingelectrical male connectors44.
• Alternatively, end caps with single-pin connectors, incorporating so-called “instant start” ballasts, as well as recessed double-pin connectors are also possible with suitable mounting sockets for this embodiment. Another possible connector and its related socket for alight tube20 are shown inFIG. 9.FIG. 12, discussed in more detail below, shows yet another connector in a different embodiment of the light source according to the present invention. Thelight tube20 could also be in the form of a conventional round housing portion, i.e., the “doughnut” shaped bulb, with the 4-pin connector used with such bulbs.
• Returning now toFIG. 1, the line drawing ofFIG. 1 also reveals the internal components of thelight tube20. Thelight tube20 further includes acircuit board30 with theLEDs22 mounted thereon. Thecircuit board30 andLEDs22 are enclosed inside thehousing portion24 and the end caps26 and28.
• FIG. 2 is a perspective view of theLEDs22 mounted on thecircuit board30. A group ofLEDs22, as shown inFIG. 2, is commonly referred to as a bank or array of LEDs. Within the scope of the present invention, thelight tube20 may include one or more banks or arrays ofLEDs22 mounted on one ormore circuit boards30. In a preferred embodiment of the present invention, theLEDs22 emit white light and, thus, are commonly referred to in the art as white LEDs. InFIGS. 1 and 2, theLEDs22 are mounted to onesurface32 of thecircuit board30. In a preferred embodiment of the present invention, theLEDs22 are arranged to emit or shine white light through only one side of thehousing portion24, thus directing the white light to a predetermined point of use. This arrangement reduces light losses due to imperfect reflection in a conventional lighting fixture. In alternative embodiments of the present invention,LEDs22 may also be mounted, in any combination, to theother surfaces34,36 and/or38 of thecircuit board30.
• FIG. 3 is a cross-sectional view ofFIG. 2 taken along lines3-3. To provide structural strength along the length of thelight tube20, thecircuit board30 shown is designed with an H-shaped cross-section that fits snugly into thelight tube20. To produce a predetermined radiation pattern or dispersion of light from thelight tube20, eachLED22 is mounted at an angle relative to adjacent LEDs and/or the mountingsurface32. The total radiation pattern of light from thelight tube20 is affected by (1) the mounting angle of theLEDs22 and (2) the radiation pattern of light from each LED. Currently, white LEDs having a viewing range between 6° and 120° are commercially available. Note thatFIG. 3 includesoptional heat sinks35, not included inFIG. 2, which extend from theside34 of thecircuit board30 opposed to theLEDs22. The addition of the heat sinks35 may be desirable in certain environments and where a large number ofLEDs22 are incorporated. The heat sinks35 could be made of metal, ceramic or other heat dissipating materials and, of course, could be incorporated in different numbers or configurations.
• Although thecircuit board30 as shown is H-shaped as discussed above, other shapes for thecircuit board30 are possible. For example, thecircuit board30 may be a conventionalflat circuit board30 as shown inFIG. 11. Note that thehousing portion24 has been omitted, and the plurality ofLEDs22 has been removed fromFIG. 11 for additional clarity. In such a configuration, theend31 of thecircuit board30 could be fixed within arecess27 of theend cap26 or otherwise fixed, such as by glue, to theend cap26. In yet another embodiment, thecircuit board30 could be a flexible circuit board in the form of a thin piece of Mylar or similar material, either laid on a mounting surface or arranged in a housing portion.
• Additional support for the light emitting diodes and the circuit board may be provided in the embodiment ofFIG. 11 or any other embodiment by coating the board, such as, for example, potting theboard30 by filling in the empty space around theboard30 or part of theboard30 with any known transparent, translucent or tinted material such as is shown inFIG. 12. A conformal coating comprising a resin or other known materials could be used. By example,FIG. 12 shows a light source according to the invention in the form of a light bulb. The light bulb includes ahousing portion25 in the form of a conventional incandescent light bulb portion with a conventionalEdison screw connector29 and aballast33. Theconnector29 would screw into a conventional base. Theballast33 can be, for example, the ballast of a conventional self-ballasted compact fluorescent light bulb, or it could be merely an enclosure to incorporate control electronics as discussed in more detail herein. Theballast33 could also be omitted with certain designs of the control electronics where the electronics would be incorporated into thehousing portion25, theconnector29 or the base (not shown). Acircuit board30 coupled to theballast33 extends from theballast33 into thehousing portion25. A plurality ofLEDs22 is mounted on opposing sides of thecircuit board30. The space between thecircuit board30 and theLEDs22 and thehousing portion25 is filled with slightly tintedmaterial23. In some cases, as where thematerial23 is tinted, the pottingmaterial23 can provide the benefit of making the light from thediscrete LEDs22 more diffuse.
• The use of thepotting material23 with the embodiment according toFIG. 1 is shown in the cross-sectional view ofFIG. 13. It is worth noting that, as can be seen by reference toFIGS. 11-13, the glass, plastic or the like that normally forms ahousing portion24,25 can be omitted. In controlled environments, thecircuit board30 andLEDs22 can be left unprotected. An alternative is to form the housing portion using a coating material such as the pottingmaterial23 or a conformal coating molded over theLEDs22 andcircuit board30. Particularly advantageous can be the use ofpotting material23 as shown inFIGS. 12 and 13 where thepotting material23 forms a shape at least partially in the form of a conventional bulb.FIG. 12 shoes the potting material12 shaped in as a conventional incandescent bulb and surrounded by a glass, plastic, etc.housing portion25. If thathousing portion25 is omitted, the potting material12 would form a housing portion for the light source.FIG. 13 shows the pottingmaterial23 forming a shape that partially conforms to a conventional tube that would, if the part identified as thehousing portion24 were omitted, form the housing portion. With respect toFIG. 13, the pottingmaterial23 could alternatively be molded around theentire circuit board30 to complete the shape of the conventional tube and serve as the housing portion, which would simplify the couplings to theconnectors26,28. As another option, the shape of the potting compound can act as a lens to affect the light distribution from the light source. This property can be used to optimize the light distribution for a particular application.
• Within the scope of the present invention, light sources such as thelight tube20 may be powered by current supplied by one of at least fourpower supply circuits100,200,300, and400. A first power supply circuit includes a power source and any conventional fluorescent ballast used to power a conventional fluorescent tube. This may include iron ballasts, high-frequency switchmode ballasts or other ballast technologies. A second power supply circuit includes a power source and a rectifier/filter circuit and eliminates the ballast. A third power supply circuit includes a DC power source and a PWM (Pulse Width Modulation) circuit. A fourth power supply circuit powers the light sources inductively.
• In the embodiments presented, the power conditioning circuits are shown as a rectifier/filter circuit coupled to a PWM switch circuit, which is coupled to a current-limiting circuit. They constitute a particular topology for a switching power supply as an example, and the invention is not intended to be limited thereby. One skilled in the art, provided with the teachings and goals herein, would know how to modify the topology from that described herein.
• FIG. 5 is an electrical block diagram of a first power supply circuit100 for supplying current to the light sources. The first power supply circuit100 is particularly adapted to operate within an existing, conventional fluorescent lighting system that incorporates a ballast. Using thelight tube20 as an example, the first power supply circuit100 includes a conventional fluorescentlight tube socket40 having two electricalfemale connectors42 disposed at opposite ends of the socket. Accordingly, alight tube20 particularly adapted for use with the first power supply circuit100 includes twoend caps26 and28, each end cap having the form of an electricalmale connector44 which mates with a corresponding electricalfemale connector42 in thesocket40.
• The first power supply circuit100 also includes apower source46 and a conventional magnetic or electronic fluorescent ballast48. Thepower source46 supplies power from the conventional fluorescent ballast48 through the connectors for the light source such as theconnectors40,42.
• The first power supply circuit100 further includes a rectifier/filter circuit50, aPWM circuit52, and one or more current-limitingcircuits54. In this example, the rectifier/filter circuit50, thePWM circuit52, and the one or more current-limitingcircuits54 of the first power supply circuit100 are packaged inside one of the twoend caps26 or28 of thelight tube20. The electronics described could be mounted with theballast33,48, or could alternatively be mounted on thecircuit board30.
• The rectifier/filter circuit50 receives AC power from the ballast48 and converts the AC power to DC power. ThePWM circuit52 receives the DC power from the rectifier/filter circuit50 and pulse-width modulates the DC power to the one or more current-limitingcircuits54. In a preferred embodiment of the present invention, thePWM circuit52 receives the DC power from the rectifier/filter circuit50 and cyclically switches the DC power on and off to the one or more current-limitingcircuits54. The DC power is switched on and off by thePWM circuit52 at a frequency which causes the white light emitted from theLEDs22 to appear, when viewed with a “naked” human eye, to shine continuously. The PWM duty cycle can be adjusted or varied by control circuitry (not shown) to maintain the power consumption of theLEDs22 at safe levels.
• The DC power is modulated for several reasons. First, the DC power is modulated to adjust the brightness or intensity of the white light emitted from theLEDs22 and, in turn, adjust the brightness or intensity of the white light emitted from the light source, herelight tube20. Optionally, the brightness or intensity of the white light emitted from the light source may be adjusted by a user. Second, the DC power is modulated to regulate the intensity of light emitted from the light source to compensate for supply voltage fluctuations, ambient temperature changes, and other such factors that affect the intensity of white light emitted by theLEDs22. Third, the DC power is modulated to raise the variations of the frequency of light above the nominal variation of 120 to 100 Hz thereby reducing illumination artifacts caused by low frequency light variations, including interactions with video screens. Fourth, the DC power may optionally be modulated to provide an alarm function wherein light from the light source cyclically flashes on and off.
• The one or more current-limitingcircuits54 receive the pulse-width modulated or switched DC power from thePWM circuit52 and transmit a regulated amount of power to one or more arrays ofLEDs22. Each current-limitingcircuit54 powers a bank of one or morewhite LEDs22. If a bank ofLEDs22 consists of more than one LED, the LEDs are electrically connected in series in an anode to cathode arrangement. If brightness or intensity variation between theLEDs22 can be tolerated, the LEDs can be electrically connected in parallel.
• The one or more current-limitingcircuits54 may include (1) a resistor, (2) a current-limiting semiconductor circuit, or (3) a switching power supply-type current limiter. Note that while it is desirable to includesuch circuits54, in some circumstances the necessary current-limiting function may be performed by the inherent electrical characteristics of the fluorescent ballast48 and/or the inherent electrical resistance of theLEDs22.
• FIG. 6 is an electrical schematic of a switching power supply-typecurrent limiter56. Thelimiter56 includes aninductor58, electrically connected in series between thePWM circuit52 and the array ofLEDs22, and apower diode60, electrically connected betweenground62 and a PWM circuit/inductor node64. Thediode60 is designed to begin conduction after thePWM circuit52 is switched off. In this case, the value of theinductor58 is adjusted in conjunction with the PWM duty cycle to provide the benefits described above. The switching power supply-typecurrent limiter56 provides higher power efficiency than the other types of current-limiting circuits listed above.
• FIG. 7 is an electrical block diagram of a secondpower supply circuit200 for supplying current to a light source according to the present invention. By example, the secondpower supply circuit200 includes a conventional fluorescentlight tube socket40 having two electricalfemale connectors42 disposed at opposite ends of thesocket40. Accordingly, alight tube20 particularly adapted for use with the secondpower supply circuit200 would include twoend caps26 and28, each end cap having the form of an electricalmale connector44, which mates with a corresponding electricalfemale connector42 in thesocket40.
• In the secondpower supply circuit200, thepower source46 supplies power directly to the rectifier/filter circuit50 through connectors, end caps26,28 orbase29. The rectifier/filter circuit50, thePWM circuit52, and the one or more current-limitingcircuits54 operate as described above to power the one or more arrays ofLEDs22. The rectifier/filter circuit50, thePWM circuit52, and the one or more current-limitingcircuits54 of the secondpower supply circuit200 are preferably packaged inside the connectors, end caps26,28 orbase29, or thehousing portion24,25 of the light source or inside the light socket(s) corresponding to the one or more connectors. This configuration has the benefit of eliminating the conventional ballast48 from the circuit, allowing direct powering of the light source from a standard building or vehicle power supply. This allows improved efficiency and reduced maintenance cost over the conventional fluorescent system.
• FIG. 8 is an electrical block diagram of a thirdpower supply circuit300 for supplying current to a light source according to the present invention. Similar to the first and secondpower supply circuits100 and200, the thirdpower supply circuit300 can include a conventional fluorescentlight tube socket40 having two electricalfemale connectors42 disposed at opposite ends of thesocket40. Accordingly, alight tube20 particularly adapted for use with the thirdpower supply circuit300 would include twoend caps26 and28, each end cap having the form of an electricalmale connector44, which mates with a corresponding electricalfemale connector42 in thesocket40.
• The thirdpower supply circuit300 includes aDC power source66, such as a vehicle battery. In the thirdpower supply circuit300, theDC power source66 supplies DC power directly to thePWM circuit52. ThePWM circuit52 and the one or more current-limitingcircuits54 operate as described above to power the one or more arrays ofLEDs22. In the thirdpower supply circuit300, thePWM circuit52 is preferably packaged in physical location typically occupied by aballast33,48 while the one or more current-limitingcircuits54 andLEDs22 are preferably packaged inside a connector, either one of the twoend caps26 or28 or theconnector29, or thehousing portion24,25.
• FIG. 9 is a fragmentary, perspective view of another embodiment of the present invention showing one end of thelight tube20 disconnected from one end of thelight tube socket40. In this embodiment of the present invention, thelight tube socket40 includes a pair ofbrackets68 and thelight tube20 includes a pair ofend caps26 and28 which mate with thebrackets68.
• FIG. 10 is an electrical block diagram of a fourthpower supply circuit400 for supplying current to the light sources. Unlike the first, second, and thirdpower supply circuits100,200, and300, which are powered through direct electrical male andfemale connectors44 and42, the fourthpower supply circuit400 is powered inductively. As such, the fourthpower supply circuit400 includes alight tube socket40 having twobrackets68 disposed at opposite ends of thesocket40 as shown inFIG. 9. At least onebracket68 includes aninductive transmitter70. Accordingly, alight tube20 particularly adapted for use with the fourthpower supply circuit400 has twoend caps26 and28 with at least one end cap including an inductive receiver orantenna72. When thelight tube20 is mounted in thelight tube socket40, the at least oneinductive receiver72 in thelight tube20 is disposed adjacent to the at least oneinductive transmitter70 in thelight tube socket40.
• The fourthpower supply circuit400 includes thepower source46 which supplies power to the at least oneinductive transmitter70 in thelight tube socket40. The at least onetransmitter70 inductively supplies power to the at least onereceiver72 in one of the end caps26 and/or28 of thelight tube20. The at least oneinductive receiver72 supplies power to the rectifier/filter circuit50. The rectifier/filter circuit50,PWM circuit52, and the one or more current-limitingcircuits54 operate as described above to power the one or more arrays ofLEDs22. In this manner, thelight tube20 is powered without a direct electrical connection.
• The LEDs shown in drawingFIGS. 1-3,12 and13 are the common discrete components. However, the invention is not limited to these discrete components. For example, surface-mounted light-emitting diodes that omit the familiar bulb portion are also possible. Another option is the organic LED, which is formed of semiconducting organic polymers layers sandwiched between two conductors. In the instant invention, a single organic LED (OLED), which comprises varying numbers of arrays printed on a substrate, can be made in the form of a sheet such as therigid OLED sheet35 shown inFIG. 14. Thesheet35 can be installed on or in place on the circuit boards described herein. An organic LED can also be formed on substrates comprising thin metal foils or flexible plastics. In this case, the organic LED is itself flexible and can be installed such that it is surrounded by a housing portion, such ashousing portion24 oflight tube20 by rolling a sheet comprising a flexibleorganic LED37 and allowing it to form the shape of thehousing portion24 as shown inFIG. 15. Of course, in embodiments incorporating the organic LED, the housing portion can still be formed in whole or in part by a coating material such as the pottingmaterial23 or the conforming layer.

Claims (1)

What is claimed is:

1. An LED-based replacement light source, comprising:

a flexible but unformed circuit board;

at least one LED mounted on the circuit board;

a housing portion for the circuit board and the at least one LED; and

a connector disposed at an end of the housing portion, the connector shaped for connection with a light socket.

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