LED lighting system

[0001] The presented invention relates to a retrofit and direct replacement of conventional fluorescent lighting tubes with light emitting diode (LED) lighting devices for usage in vehicles, including mass-transit vehicles such as buses, trains, subway trains, also for lighting watercrafts, aircrafts, signage, or buildings using LEDs.

[0002] For many years the lighting of interiors of vehicles, aircraft, buildings, signage, and watercraft, and more recently the lighting of exteriors of vehicles, and signage have use the cold cathode lamp; more commonly known as the fluorescent lamp or a fluorescent system. The fluorescent lamp however has limitations on its capabilities and usages. The fluorescent lamp has disadvantages to the consumer. The disadvantages of the fluorescent lamp are the short life, easily broken, low durability, high costs of replacement, high costs of specialty lights, limited color selection, electromagnetic interference (EMI) which may be harmful to other electronic equipment. The manufacturing of fluorescent lamps and debris from replaced lamps have a high environmental risks, as the chemicals inside of a fluorescent lamp are toxic. Also the flicker effect of dying or improperly installed fluorescent lamps may be extremely harmful to individuals with certain medical conditions. The constant inconsistency of fluorescent lighting colors is often a complaint of consumers who have to replace lamps on a regular basis. A fluorescent system cannot be used effectively in extreme low or high ambient temperatures.

[0003] To attempt to avoid difficulties with fluorescent lighting, proposals have been made to use LEDs as replacements for fluorescent lighting, as for example described in U.S. Pat. No. 6,860,628 issued Mar. 1, 2005 and U.S. Pat. No. 6,583,550 issued Jun. 24, 2003. While these devices do provide some of the advantages of LEDs, there remains a need for lighting systems that can supply sufficient illumination to meet lighting requirements in vehicles, including mass-transit vehicles such as buses, trains, subway trains, also for lighting watercrafts, aircrafts, buildings and signage without excessive heat build up, while reducing the amount of lamps, wiring, ballasts, power consumption and maintenance that fluorescent systems require.

[0004] In accordance with an aspect of the invention, there is therefore provided a light emitting diode lighting device and system that can be used for illuminating the interior and/or exterior of vehicles, aircraft, watercraft, signage or buildings is provided. The system includes a voltage feedback constant current power supply circuitry and high power LEDs. The printed circuit assemblies are preferably firmly mounted onto a continuous or semi-continuous mounting channel case that also works as a heat sink. By this means, it not only increases the reliability of the LED lighting tube but also it provides sufficient heat dissipation capability for the heat generated by the LEDs. Since the operating temperature of the LEDs is controlled and stays in cool condition, it dramatically increases the LED's lifetime and efficiency. The end caps and pins of this LED lighting device are fully compatible with existing conventional fluorescent light fixtures and can directly replace those fluorescent lighting tubes in vehicles, mass-transit, watercrafts, aircrafts, signage or buildings with minimal modifications.

[0005] In further aspects of the invention, an LED lighting system has a housing forming a channel and being heat conductive and rigid, with one or both ends of the housing having electrical connectors for connection to a power source. An LED array extends along the housing within the channel, each LED in the LED array having a power rating of greater than 0.5 watt. Onboard current control circuitry for the LED array is carried by the housing, preferably within the channel, and may provide current control for individual sets of LEDs. The current control allows careful control of the forward current passing through the LED array so that it controls the brightness and heat production by the LEDs.

[0006] These and other aspects of the invention are described in the detailed description of the invention and claimed in the claims that follow.

[0045] In this patent document, “comprising” means “including”. In addition, a reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present.

[0046] In FIGS. 1-3, 7-12, there is shown an exemplary LED lighting system 10 that includes a plurality of LEDs 100, each LED 100 being supplied power from a circuit board 101 supported by housing 102. Housing 102 forms a channel and is made of a heat conductive and rigid material, such as aluminum or any thermally conductive formable material. In one embodiment, the housing 102 is both heat conductive and rigid and is made of a unitary piece of material. The housing 102 is rigid and extends from end to end of the LED lighting system 10. The heat sink capability may be continuous from end to end or may be semi-continuous. In the case of being semi-continuous, the material providing the heat sink function may have breaks, in which case additional connector material is required to provide the channel with sufficient rigidity so that the lighting system 10 does not collapse or sag under its own weight. The circuitry 20 or 30 provide current control for the LED lighting system 10 and are attached to the housing 102 permanently such as by fasteners 108 (FIG. 3), which may be rivets or screws, so they do not allow for vibration to loosen the connection between the circuit board 101 and the housing 102 over time. The housing 102 does not require adhesive, or thermally conductive substance to connect to the circuit board 101. The housing 102 provides a rigid backbone structure to the LED lighting system 10, and is sufficiently rigid to prevent the LED lighting system 10 to resist or prevent breakage during normal use, or bending, unless the product design requires it. The housing 102 may be provided with a cover 107 secured in a groove 109 that runs along the inside edge of the housing walls. The cover 107 is transparent, translucent and may be formed as a lens.

[0047] At one or both ends of the housing 102 there are provided electrical connectors 103, 105, and 106 for connection of the lighting system 10 to a power source. When LED lighting system 10 is configured as a bulb, rather than as tube, it will typically have connectors only at one end. In the embodiment of FIGS. 1, 4, 7 and 8, a single connector 105 of Pin Type 1 is formed in end caps of the housing 102. In the embodiment of FIGS. 2, 5, 6, and 9-12 double connectors 106 of Pin Type 2, either in the bi-pin format (FIGS. 6, 11 and 12) or the recessed double contact type (FIGS. 5, 9 and 10) are formed in end caps 104 of the housing 102. These connectors 105, 106 are of conventional design. The end caps 104 may be any suitable material such as plastic, Lexan™, polycarbonate, acrylic, ABS, metal such as aluminum, copper, brass, stainless steel, metal alloy, combination of metal and plastic, or fiberglass. The end caps 104 may be manufactured in different shapes and sizes, all able to connect to the circuit boards 101 within the housing 102. The end caps 104 encase the channel, are secured against movement and do not break with vibration. The end caps 104 also secure and prevent movement of the lens 107, 118-127. As with the other components of the lighting system 10, the end caps 104 should be made to withstand high ambient temperatures (up to 125° C.+) and low ambient temperatures (as low as −40° C.). In the case of use of the LED lighting system 10 as a fluorescent light fixture replacement, the connectors 105, 106 are conventional pins for attached to fluorescent light fixture receptacles. In other embodiments, such as when the LED lighting system 10 is used in a single socket fixture, the connectors 106 may be provided at one end only of the housing 102.

[0048] An LED array formed of LEDs 100 extends along the housing within the channel formed by the housing 102. To provide sufficient power to provide light, particularly in an industrial or commercial environment, each LED 100 in the LED array should have a power rating of greater than 0.5 watt. The circuit boards 101 provide onboard current control circuitry for the LED array. The circuit boards 101 are carried by the housing 102 and are in electrical communication with the electrical connectors 103. 105, 106. The LEDs 100 are preferably organized in groups of LEDs, either in series, or parallel. The LEDs may be surface mounted (SMT) or through hole mounted (TH). The colour of the LEDs can be any available colour such as white, blue, green, red, yellow, amber, or orange.

[0049] FIGS. 13 and 14 show circuit diagrams with an example circuit 20 for onboard current control. The circuits of FIGS. 13, 14, 35, 36 may all be placed on the circuit board or boards 101. FIG. 13 illustrates a single circuit 20 connected to a conventional power source 208, while FIG. 14 shows multiple circuits 20 in parallel connected to a conventional power source 208. The circuit boards 101 for the circuits 20 may be made of fiberglass based printed circuit board (PCB) or metal based (for example Aluminum) PCB. The circuit boards 101 may be TH type or SMT type. Preferably, the surface of the circuit boards 101 have a white solder mask and exposed areas of tinned plane so as to efficiently reflect the majority of LED light. The circuit boards 101 may be flexible to accommodate mounting channels and lighting fixtures in different shapes and curves. As shown in FIGS. 13 and 14, the LED array is divided into sets 209 of LEDs, with for example five LEDs per set. As shown in FIG. 14, the onboard current control circuitry is formed of multiple circuits 20. Each circuit 20 of the multiple current controllers provides current control for a corresponding set 209 of LEDs in the LED array.

[0050] The onboard current control circuitry 20 is configured to provide constant current to the LEDs 100 of the LED array 209. A polarity protection circuit 201 of conventional design safeguards against the user installing the product in the wrong polarity. Current control is provided by current control circuit 202, also of conventional design. As an example, the current control circuit 202 may be use pulse width modulation (PWM) to control the current supplied to the LEDs. The circuit 202 supplies constant, controlled, current to unit for the entire LED set 209 with information from voltage sensor 203. The voltage sensor 203 receives current information from LEDs 209 and feeds back information to the current control circuitry 202. For example, in the use of PWM, the voltage sensor 203 converts the current of LED array 209 to voltage signal and supplies the voltage signal to the current control circuit 202. The current control circuit 202 senses how much the detected voltage varies from the desired level, and by varying the pulse width or frequency, changes the current supplied to the LEDs towards the desired level. The power supply 208 may be AC or DC, although in the example shown it is DC. Current control provides constant brightness and prevents overheating. A typical pulse frequency for the current control may be 200 kHz to 4 MHz. This low voltage application shown here provides voltage for applications below about 72 volts.

[0051] The organization of the circuit boards 101 is shown in FIGS. 15 and 16. FIG. 15 shows a single set of five LEDs 100 with circuit components 201, 202 and 203. FIG. 16 shows an exploded side view of an LED lighting system 10, with housing 102, cover 107 and with LEDs 100 secured to a circuit board 101 with heat sink compound 117.

[0052] FIG. 17 is an example of an LED lighting system or tube 10 in a mass transit application. A transit vehicle has a body or hull 303 with a windshield 300. The break away shows floor 304, with seating 306 and partition 305. Lighting tubes 10 may be installed in pre-existing fluorescent light sockets or receptacles 309, with bypassing or removal of the fluorescent light ballasts 308. FIG. 26 is another view of the mass transit application, showing also passengers 310 and a reading plane 311 and floor plane 313, which acts as a test zone for establishing whether the LEDs are providing sufficient illumination. FIGS. 18, 19 and 20 illustrate an application in which the LED lighting system 10 is used as part of an advertising sign 401 for a taxi 400. FIGS. 21, 22 and 23 illustrate an application in which the LED lighting system 10 is used as part of an on duty sign 404 for a taxi 400. FIGS. 24 and 25 illustrate installation of the LED lighting system 10 in new or pre-existing fluorescent light fixtures of an aircraft with a fuselage 500, seating 501, windows 502, upper luggage compartment 503, cargo area 504 and floor 505.

[0053] In FIGS. 27A-27K, various shapes of cover lens 107 are shown including moderate convex 124, straight 107, straight raised 118, asymmetrically peaked 119 and 120, symmetrically peaked 121, raised dome 122, low dome 123, convex 124, depressed low dome 125 raised convex 126, and low dome with channel enclosing 127. FIG. 28 shows a fluorescent lamp fixture 600 with power receptacles or sockets 601, conventional ballast 602 for lamp 603, replacement LED lighting tube 10, ballast cover 604 and diffuser panel 605. While the lens 107 is not required for the final assembly it can be added to act as a guard against vandalism, as a dust/dirt guard, as a light enhancing device, as a light directing/focusing device, as a moisture/waterproofing device (sealing unit completely with the addition of sealant) or as a light diffuser. In FIG. 28, only the lighting tube 10 is new. FIG. 37 shows replacement of a fluorescent lamp 603 in a display sign application with an LED lighting tube 10 that fits between power receptacles 601. The ballast 602 may be removed or bypassed.

[0054] In FIGS. 29-31, powered end of an LED lighting tube for a vehicle application includes LED 100 (one of several in the array), housing 102, connecting wires 103 that connect to the circuit board 101 and rivets 108 for securing the circuit board 101 on the housing 102. The connecting wires 103 pass through the holes 114 in O-rings 110 that are secured to the upstanding flange of an inner mounting bracket 116. The mounting bracket 116 is secured to the housing 102 by a bolt 113 secured with nuts 112 and washer 111. Bolt 113 and nuts 112 also secure outer mounting bracket 115 to the housing 102. Rivets 108 also secure the side walls of the mounting bracket 116 to the channel walls of the housing 102. Mounting bracket 115 is used to connect the LED lighting tube of this embodiment to a structural portion of a vehicle. FIGS. 32-34 show the non-powered end of the LED lighting system for a vehicle, which is the same as the powered end except that there are no power connections.

[0055] FIG. 35 shows electrical circuitry 30 of an onboard circuit board, and FIG. 36 shows several such boards connected in parallel between respective power buses. FIGS. 35 and 36 show circuitry for a high voltage power source, above 72 volts, for example 120 volts to 240 volts, either AC or DC. The example shown here is for AC power supply. Fuse 215 protects the circuitry of the board from power surges. The fuse can be permanent or be a resettable fuse. Bi-directional filter circuit 204 filters out noise. Full wave rectifier 205 transforms AC current from the power bus (left side of figure) to DC current. The DC current from the full wave rectifier 205 is supplied to voltage regulator 207 to step the voltage down to a low level, for example 5 volts, to power switching power supply control IC 210. The switching power supply control IC 210 provides a modulated signal at about 250 kHz or more that determines the switching frequency or pulse width of a high voltage switching power driver circuit 211. The switching signal from driver 211 drives a primary coil of transformer 216, and causes DC voltage supplied by the full wave rectifier 205 to switch at the switching frequency or pulse width determined by the control IC 210. Transformer 216 couples this switching voltage through half-wave rectifier 206 which also filters the high frequency signal from the transformer 216 to the LED array 209 on the right side of FIG. 35. The half-wave rectifier 206 provides the switching frequency or pulse width of the current from the secondary of the transformer 216 and supplies a isolated feedback signal through a signal feedback circuit 212 to control IC 210. Depending on whether the sensed signal is above or below the desired current level, the control IC 210 varies the pulse width or pulse frequency of the signal driven by the driver circuit 211 to ensure a constant average current supplied to the LEDs. The transformer 216 both isolates input from the output, which drives the LEDs, and provides a voltage step down from high voltage above 72 volts, to low voltage required by the LED array 209. The control IC 210 may also be configured to vary the average current supplied to the LEDs, by suitable controlling the pulse width or frequency of the drive signal to the circuit 211, and thus provide a dimmable controller that can be used to control the brightness of the lighting devices. The switching power supply circuit 30 may be mounted on each circuit board 101, or shared by each of several circuit boards 101 and located at one end of the lighting device 10.

[0056] The switching power supply circuit 30 is integrated with the LEDs 100 on each section of printed circuit board 101, so that any defect of each power supply circuits or LEDs 100 would not affect the lighting device 10 as a whole. The other circuit boards 101 of the lighting device are still active. The LED lighting device 10 can be installed in polarity or no polarity, and may have any required length. The LED lighting device 10 may use voltages from 1.5V˜240V in both DC and AC, and may fit retroactively into existing fluorescent lighting fixtures after removing or bypassing the ballast. This LED lighting device 10 can be a replacement or retrofit for all existing fluorescent lighting tubes larger than the size of T6.

[0057] Immaterial modifications may be made to the embodiments described here without departing from the invention.