WO2013014580A1 - Pilote de diode électroluminescente à circuit non destructif indiquant la défaillance ou la panne de la charge de diodes électroluminescentes - Google Patents

Pilote de diode électroluminescente à circuit non destructif indiquant la défaillance ou la panne de la charge de diodes électroluminescentes Download PDF

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Publication number
WO2013014580A1
WO2013014580A1 PCT/IB2012/053681 IB2012053681W WO2013014580A1 WO 2013014580 A1 WO2013014580 A1 WO 2013014580A1 IB 2012053681 W IB2012053681 W IB 2012053681W WO 2013014580 A1 WO2013014580 A1 WO 2013014580A1
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WIPO (PCT)
Prior art keywords
led
load
driver
fault
input
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PCT/IB2012/053681
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English (en)
Inventor
Aly Aboulnaga
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Koninklijke Philips Electronics N.V.
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Publication of WO2013014580A1 publication Critical patent/WO2013014580A1/fr

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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/10—Controlling the intensity of the light
    • H05B45/14—Controlling the intensity of the light using electrical feedback from LEDs or from LED modules
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B45/385—Switched mode power supply [SMPS] using flyback topology
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/40—Details of LED load circuits
    • H05B45/44—Details of LED load circuits with an active control inside an LED matrix
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/50—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
    • H05B45/58—Circuit arrangements for operating light-emitting diodes [LED] responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits involving end of life detection of LEDs

Definitions

  • the present invention is directed generally to light emitting diode (LED) based lighting units, and drivers for LED light sources. More particularly, various inventive methods and apparatus disclosed herein relate to a driver for a load of one or more LED light sources that is configured to provide a desired change in its input impedance in response to a fault or outage of the LED load.
  • LED light emitting diode
  • FIG. 1 is a high level block diagram of one example of a traffic light system 100.
  • Traffic light system 100 includes a traffic light controller 110, a traffic lighting unit 120, a 20 kQ load resistor 130 and a relay 140.
  • traffic light system 100 is shown in FIG. 1 with one traffic light controller 110 and one traffic lighting unit 120, in some implementations a single traffic light controller 110 may control three or more traffic lighting units 120 (e.g., a red traffic lighting unit 120, a yellow traffic lighting unit 120, and a green traffic lighting unit 120).
  • traffic lighting unit 120 may comprises an incandescent lamp and a color filter to output light of a desired color (e.g., red, yellow, green, white, etc.).
  • traffic light controller 110 supplies an AC output voltage 115, e.g., nominally 110-120 VAC, which is provided via the parallel combination of load resistor 130 and relay 140 as an AC input voltage 125 to traffic lighting unit 120.
  • AC output voltage 115 e.g., nominally 110-120 VAC
  • traffic light controller 110 "turns on” traffic lighting unit 120 by controlling relay 140 to be switched on or connected across load resistor 130.
  • AC input voltage 125 provided to traffic lighting unit 120 is essentially the same as AC output voltage 115 provided by traffic light controller 110, and the incandescent lamp in traffic lighting unit 120 is lit to produce light.
  • controller In an OFF mode, controller "turns off” traffic lighting unit 120 by controlling relay 140 to be switched off or disconnected across load resistor 130.
  • AC output voltage 115 is provided to traffic lighting unit 120 via the 20 kQ load resistor 130 as a series input impedance.
  • a voltage divider occurs between the impedance of the filament in the incandescent lamp in traffic lighting unit 120, which is normally very low, and the 20 kQ load resistor 130.
  • input voltage 125 applied across the input of traffic lighting unit 120, and therefore applied to the incandescent lamp in traffic lighting unit 120 is only a few volts at most (e.g., ⁇ 10 VAC). Accordingly, the incandescent lamp in traffic lighting unit 120 is not lit and does not produce light.
  • the incandescent lamp in traffic lighting unit 120 has a lifetime and eventually the filament will "burn out” and become open so as to no longer cause conduct current and cause the incandescent lamp to produce light. Accordingly, the incandescent lamp will need to be replaced from time to time.
  • traffic light controller 110 includes a means for detecting when the incandescent lamp in traffic lighting unit 120 needs to be replaced, in which case, traffic light controller 110 may generate a signal or other indicator that the incandescent lamp in traffic lighting unit 120 requires replacement.
  • traffic lighting unit 120 When the incandescent lamp in traffic lighting unit 120 is working properly, then traffic lighting unit 120 will have a relatively low input impedance ( « 20 kQ) set by the low impedance of the filament of the incandescent lamp. In that case, when relay 140 is open so that there is a voltage divider between the impedance of the incandescent lamp (which is quite small) and load resistor 130, only a small percentage of AC output voltage 115 will appear across the input of traffic lighting unit 120 as AC input voltage 125. On the other hand, when the incandescent lamp in traffic lighting unit 120 has burned out, then traffic lighting unit 120 will have a relatively high input impedance (e.g., > 20 kQ) based on the lamp filament being open.
  • a relatively high input impedance e.g., > 20 kQ
  • traffic light controller 110 may measure AC input voltage 125 across the input of traffic lighting unit 120 in the OFF mode where traffic light controller 110 opens relay 140 and turns off traffic lighting unit 120. In particular, if traffic light controller 110 measures AC input voltage 125 in the OFF mode as being less than a predetermined threshold voltage (which may be, for example a voltage between about 10 VAC and 100 VAC) then traffic light controller 110 may determine that the incandescent lamp in traffic lighting unit 120 is working properly.
  • a predetermined threshold voltage which may be, for example a voltage between about 10 VAC and 100 VAC
  • traffic light controller 110 may determine that the incandescent lamp in traffic lighting unit 120 has bu rned out. In that case, traffic light controller 110 may generate an alarm signal or other indication (e.g., light an indicator light) that the incandescent lamp in traffic lighting unit 120 requires replacement.
  • an alarm signal or other indication e.g., light an indicator light
  • LEDs light-emitting diodes
  • Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, durability, lower operating costs, and many others.
  • Recent advances in LED technology have provided efficient and robust full-spectrum LED light sources that enable a variety of lighting effects in many applications.
  • Some LED-based lighting units embodying these LED light sources feature a lighting module, including one or more LEDs capable of producing different colors, e.g.
  • red, green, and blue as well as a processor for independently controlling the output of the LEDs in order to generate a variety of colors and color-changing lighting effects, for example, as discussed in detail in U.S. Patent Nos. 6,016,038 and 6,211,626.
  • the LED-based lighting unit needs to present a relatively low input impedance ( « 20 kO, e.g., ⁇ 1 kO) to the traffic light controller so that the input voltage across the input terminals of the LED-based lighting unit as measured by the traffic light controller is low (e.g., ⁇ 10 VAC) and the traffic light controller will conclude that the LED-based lighting unit is working properly.
  • 20 kO e.g., ⁇ 1 kO
  • the LED-based lighting unit needs to present a relatively high input impedance (» 20 kO, e.g., > 200 kO) to the traffic light controller so that the input voltage across the input terminals of the LED-based lighting unit as measured by the traffic light controller is relatively high (e.g., > 100 VAC) and the traffic light controller will determine that the LED-based lighting unit has a defect and one or more LED light source s need to be replaced.
  • a relatively high input impedance « 20 kO, e.g., > 200 kO
  • LED-based lighting unit configured to be retrofit into an existing light system, such as a traffic light system, and an LED driver for one or more LED light sources in such an LED-based lighting unit.
  • an LED-based lighting unit that can mimic the input impedance and voltage behavior of an incandescent lamp in an OFF state when the one or more LED light sources is/are working normally, and when there is an open or short fault in the one or more LED light sources.
  • LED driver whose fault detection may be tested nondestructive ⁇ during manufacturing and while installed, and which is relatively small, inexpensive, and efficient.
  • the present disclosure is directed to inventive methods and apparatus for providing a driver for a load of one or more solid state light sources that is configured to provide a desired change in its input impedance in response to a fault or outage of the load.
  • the present invention provides a solid state lighting unit, and a driver for one or more solid state light sources in a solid state lighting unit, that can permit a traffic light controller to detect a fault in the solid state light sources using the existing means that the traffic light controller already employs to detect when an incandescent lamp in an existing traffic light system needs to be replaced.
  • a driver for supplying power to a load including at least one light-emitting diode (LED) light sources.
  • the driver includes: a rectifier configured to rectify an AC input voltage; a DC/DC converter including a switching device (e.g., a power switching device) for converting the rectified AC input voltage into a regulated DC current for driving the load; and a controller configured to supply a switching control signal to control a switching operation of the switching device of the DC/DC converter.
  • the controller has a zero crossing detection (ZCD) input and supplies the switching control signal in response to a voltage supplied to the ZCD input.
  • ZCD zero crossing detection
  • the driver also includes a fault detector configured to detect whether the load has a fault, including detecting when the load has an open circuit condition and detecting when the load has a short circuit condition, and producing a fault detector output signal that indicates whether the load has a fault; and a controller disabler configured to receive the fault detector output signal and in response thereto to disable the ZCD input of the controller when the fault detector output signal indicates that the load has a fault.
  • a fault detector configured to detect whether the load has a fault, including detecting when the load has an open circuit condition and detecting when the load has a short circuit condition, and producing a fault detector output signal that indicates whether the load has a fault
  • a controller disabler configured to receive the fault detector output signal and in response thereto to disable the ZCD input of the controller when the fault detector output signal indicates that the load has a fault.
  • the switching device of the DC/DC converter when the ZCD input is disabled (e.g., by driving the ZCD input to control ground), then the switching device of the DC/DC converter is turned off.
  • the driver also includes a pair of input terminals configured to receive the AC input voltage, wherein when the switching device of the DC/DC converter is turned on then an input impedance of the driver across the pair of input terminals has a first value, and when the switching device of the DC/DC converter is turned off then the input impedance of the driver has a second value, wherein the second value is substantially greater than the first value.
  • the controller disabler comprises a field effect transistor having a first terminal connected to fixed potential, a second terminal connected to the ZCD input of the controller, and a gate connected to receive the fault detector output signal from the fault detector.
  • the driver is turned off when the AC input voltage is supplied from a source with a series impedance of about 20 kQ.
  • a method for operating a driver for supplying power to a load including one or more light-emitting diode (LED) light sources.
  • the method comprises: rectifying an AC input voltage; converting the rectified AC input voltage to a regulated DC current for driving the load by performing a DC/DC conversion with a switching device; supplying a switching control signal to the switching device to control a switching operation thereof in response to a zero crossing detection (ZCD) input; detecting whether the load has a fault, including detecting when the load has an open circuit condition and detecting when the load has a short circuit condition; and in response to detecting that the load has a fault, disabling the ZCD input so as to disable switching of the switching device and provide a high input impedance across input terminals of the driver.
  • ZCD zero crossing detection
  • a device includes: a rectifier configured to rectify an AC input voltage; a DC/DC converter including a switching device, wherein the DC/DC converter is configured to convert the rectified AC input voltage into a DC current in response to a switching operation of the switching device, and to supply the current to a load including at least one light-emitting diode (LED) light source; a controller configured to supply a switching control signal to control the switching operation of the switching device of the DC/DC converter in response to a signal at a feedback input of the controller; a fault detector configured to detect a fault at the load, wherein the fault detector produces a fault detector output signal that indicates whether the load has a fault; and a controller disabler configured to receive the fault detector output signal and in response thereto to disable the input of the controller when the fault detector output signal indicates that the load has a fault.
  • LED light-emitting diode
  • the term "LED” should be understood to include any electroluminescent diode or other type of carrier injection/junction- based system that is capable of generating radiation in response to an electric signal.
  • the term LED includes, but is not limited to, various semiconductor-based structures that produce light in response to current, light emitting polymers, organic light emitting diodes (OLEDs), electroluminescent strips, and the like.
  • LED refers to light emitting diodes of all types (including semi-conductor and organic light emitting diodes) that may be configured to generate radiation in one or more of the infrared spectrum, ultraviolet spectrum, and various portions of the visible spectrum (generally including radiation wavelengths from approximately 400 nanometers to approximately 700 nanometers).
  • Some examples of LEDs include, but are not limited to, various types of infrared LEDs, ultraviolet LEDs, red LEDs, blue LEDs, green LEDs, yellow LEDs, amber LEDs, orange LEDs, and white LEDs (discussed further below).
  • LEDs may be configured and/or controlled to generate radiation having various bandwidths (e.g., full widths at half maximum, or FWHM) for a given spectrum (e.g., narrow bandwidth, broad bandwidth), and a variety of dominant wavelengths within a given general color categorization.
  • bandwidths e.g., full widths at half maximum, or FWHM
  • FWHM full widths at half maximum
  • an LED configured to generate essentially white light may include a number of dies which respectively produce different spectra of electroluminescence that, in combination, mix to form essentially white light.
  • a white light LED may be associated with a phosphor material that converts electroluminescence having a first spectrum to a different second spectrum.
  • electroluminescence having a relatively short wavelength and narrow bandwidth spectrum "pumps" the phosphor material, which in turn radiates longer wavelength radiation having a somewhat broader spectrum.
  • an LED does not limit the physical and/or electrical package type of an LED.
  • an LED may refer to a single light emitting device having multiple dies that are configured to respectively produce different spectra of radiation (e.g., that may or may not be individually controllable).
  • an LED may be associated with a phosphor that is considered as an integral part of the LED (e.g., some types of white LEDs).
  • the term LED may refer to packaged LEDs, non-packaged LEDs, surface mount LEDs, chip-on-board LEDs, T-package mount LEDs, radial package LEDs, power package LEDs, LEDs including some type of encasement and/or optical element (e.g., a diffusing lens), etc.
  • the term "light source” should be understood to refer to any one or more of a variety of radiation sources, including, but not limited to, LED light sources (including one or more LEDs as defined above), incandescent sources (e.g., filament lamps, halogen lamps), fluorescent sources, phosphorescent sources, high-intensity discharge sources (e.g., sodium vapor, mercury vapor, and metal halide lamps), lasers, other types of electroluminescent sources, pyro-luminescent sources (e.g., flames), candle-luminescent sources (e.g., gas mantles, carbon arc radiation sources), photo-luminescent sources (e.g., gaseous discharge sources), cathode luminescent sources using electronic satiation, galvano-luminescent sources, crystallo- luminescent sources, kine-luminescent sources, thermo-luminescent sources, triboluminescent sources, sonoluminescent sources, radioluminescent sources, and luminescent polymers.
  • LED light sources including one
  • a given light source may be configured to generate electromagnetic radiation within the visible spectrum, outside the visible spectrum, or a combination of both.
  • a light source may include as an integral component one or more filters (e.g., color filters), lenses, or other optical components.
  • filters e.g., color filters
  • lenses e.g., prisms
  • light sources may be configured for a variety of applications, including, but not limited to, indication, display, and/or illumination.
  • illumination source is a light source that is particularly configured to generate radiation having a sufficient intensity to effectively illuminate an interior or exterior space.
  • sufficient intensity refers to sufficient radiant power in the visible spectrum generated in the space or environment (the unit “lumens” often is employed to represent the total light output from a light source in all directions, in terms of radiant power or "luminous flux”) to provide ambient illumination (i.e., light that may be perceived indirectly and that may be, for example, reflected off of one or more of a variety of intervening surfaces before being perceived in whole or in part).
  • the term “spectrum” should be understood to refer to any one or more frequencies (or wavelengths) of radiation produced by one or more light sources. Accordingly, the term “spectrum” refers to frequencies (or wavelengths) not only in the visible range, but also frequencies (or wavelengths) in the infrared, ultraviolet, and other areas of the overall electromagnetic spectrum. Also, a given spectrum may have a relatively narrow bandwidth (e.g., a FWHM having essentially few frequency or wavelength components) or a relatively wide bandwidth (several frequency or wavelength components having various relative strengths). It should also be appreciated that a given spectrum may be the result of a mixing of two or more other spectra (e.g., mixing radiation respectively emitted from multiple light sources).
  • color is used interchangeably with the term “spectrum.”
  • the term “color” generally is used to refer primarily to a property of radiation that is perceivable by an observer (although this usage is not intended to limit the scope of this term). Accordingly, the terms “different colors” implicitly refer to multiple spectra having different wavelength components and/or bandwidths. It also should be appreciated that the term “color” may be used in connection with both white and non-white light.
  • the term "lighting unit” is used herein to refer to an apparatus including one or more light sources of same or different types.
  • a given lighting unit may have any one of a variety of mounting arrangements for the light source(s), enclosure/housing arrangements and shapes, and/or electrical and mechanical connection configurations. Additionally, a given lighting unit optionally may be associated with (e.g., include, be coupled to and/or packaged together with) various other components (e.g., control circuitry, which may include one or more drivers) relating to the operation of the light source(s).
  • An "LED-based lighting unit” refers to a lighting unit that includes one or more LED light sources as discussed above, alone or in combination with other non LED light sources.
  • driver is used herein generally to refer to an apparatus for receiving input power for supplying that power in a format to one or more light sources to cause the light source(s) to produce light.
  • LED driver refers to an apparatus for receiving input power and supplying that power to a load of one or more LED light sources including one or more LEDs as discussed above to cause the one or more LED light sources to produce light.
  • controller is used herein generally to describe various apparatus relating to the operation of one or more light sources.
  • a controller can be implemented in numerous ways (e.g., such as with dedicated hardware) to perform various functions discussed herein.
  • a "processor” is one example of a controller which employs one or more microprocessors that may be programmed using software (e.g., microcode) to perform various functions discussed herein.
  • a controller may be implemented with or without employing a processor, and also may be implemented as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions. Examples of controller components that may be employed in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field-programmable gate arrays (FPGAs).
  • ASICs application specific integrated circuits
  • FPGAs field-programmable gate arrays
  • a processor or controller may be associated with one or more storage media (generically referred to herein as "memory,” e.g., volatile and non-volatile computer memory such as RAM, PROM, EPROM, and EEPROM, floppy disks, compact disks, optical disks, magnetic tape, etc.).
  • the storage media may be encoded with one or more programs that, when executed on one or more processors and/or controllers, perform at least some of the functions discussed herein.
  • Various storage media may be fixed within a processor or controller or may be transportable, such that the one or more programs stored thereon can be loaded into a processor or controller so as to implement various aspects of the present invention discussed herein.
  • program or “computer program” are used herein in a generic sense to refer to any type of computer code (e.g., software or microcode) that can be employed to program one or more processors or controllers.
  • FIG. 1 shows a functional block diagram of a traffic light system.
  • FIG. 2 shows one example of an LED-based lighting unit that may be employed, for example, in the traffic light system of FIG. 1.
  • FIG. 3 shows a functional block diagram of one embodiment of an LED-based lighting unit that may be employed, for example, in the traffic light system of FIG. 1, while overcoming one or more of the shortcomings of the LED-based lighting unit of FIG. 2.
  • FIG. 4 shows a detailed schematic diagram of one embodiment of an LED-based lighting unit that may be employed, for example, in the traffic light system of FIG. 1, with an LED driver whose fault detection may be tested non-destructively.
  • Applicants have recognized and appreciated that it would be beneficial provide an LED-based lighting unit that can mimic the input impedance and voltage behavior of an incandescent lamp in an OFF state when the LED load is working normally, and when there is an open or short fault in the LED load. More specifically, there is a need for such an LED driver whose fault detection may be tested non-destructively during manufacturing and while installed, and which is relatively small, inexpensive, and efficient.
  • various embodiments and implementations of the present invention are directed to an LED-based lighting unit, and an LED driver for an LED-based lighting unit that provides a relatively low input impedance in an OFF state when the LED load is working normally, and provides a relatively high input impedance in an OFF state when there is an open or short fault in the LED load. More specifically, there is a need for such an LED driver whose fault detection may be tested non-destructively during manufacturing and while installed, and which is relatively small, inexpensive, and efficient.
  • FIG. 2 shows one example of an LED-based lighting unit 200 that may be employed, for example, in the traffic light system of FIG. 1.
  • LED-based lighting unit 200 includes, in pertinent part, a rectifier 210, a DC/DC converter 220, an LED load 230, a controller 240, an outage monitor 250, a switch 260, and a fusistor 270.
  • DC/DC converter 220 includes a flyback transformer 222 and a switching device 224.
  • switching device 224 is a first high power Metal Oxide Semiconductor Field Effect Transistor (MOSFET)
  • switch 260 is a second high power MOSFET.
  • LED load 230 may comprise one or more LED light sources, including one or more LEDs.
  • the portion of LED-based lighting unit 200 excluding LED load 230 is referred to as an LED driver.
  • LED-based lighting unit 200 may be installed in a traffic light system, such as the traffic light system 100 of FIG. 1.
  • LED-based lighting unit 200 may be retrofit in traffic light system 100 as a replacement for a lighting unit that employs incandescent lamps.
  • LED-based lighting unit 200 may be configured to produce light having one of the three traditional traffic light colors: red, amber or green.
  • a traffic light system may include three LED-based lighting units, one for each of the three traditional traffic light colors all under control of a single traffic light controller.
  • each LED-based lighting unit may be associated with and controlled by its own traffic light controller.
  • LED-based lighting unit 200 An operation of LED-based lighting unit 200 will now be explained with respect to an installation in traffic light system 100.
  • traffic light controller 110 controls LED-based lighting unit 200 to be ON or OFF in accordance with a desired traffic light pattern.
  • Traffic light controller 110 turns ON LED-based lighting unit 200 by switching relay 140 to be connected across the 20 kO load resistor 130. In that case, all or virtually all of AC output voltage 115 appears as AC input voltage 125 across the input terminals of LED-based lighting unit 200.
  • Rectifier 210 rectifies AC input voltage 125
  • DC/DC converter 220 converts the rectified AC input voltage into a desired current and voltage for driving LED load 230.
  • Controller 240 receives a DC supply voltage Vcc from the rectified AC input voltage and in response to a current through switching device 224 sensed at input pin Isen, controls the switching operation of switching device 224 to cause DC/DC converter 220 to provide the desired current and voltage to LED load 230 according to well-known algorithms.
  • the DC current from DC/DC converter 220 causes the LED(s) in LED load 230 to be lit and produce light of a desired color.
  • Traffic light controller 110 turns OFF LED-based lighting unit 200 by switching relay 140 to be open across the 20 kQ load resistor 130. In that case, AC output voltage 115 is supplied across the input terminals of LED-based lighting unit 200 as AC input voltage 125 according to a voltage divider:
  • VAC-IN VAC-OUT (Z, N /( Z, N + 20 ⁇ )
  • V A ⁇ MN is the voltage of AC input voltage 125
  • V A C-OUT is the voltage of AC output voltage 115
  • Z !N is the input impedance of LED-based lighting unit 200 in the OFF mode.
  • the AC input voltage 125, and input current, supplied to LED-based lighting unit 200 is reduced in the OFF mode so as to cause outage monitor 250 to turn on switch 260 and thereby provide a low impedance current path to ground through fusistor 270.
  • the input impedance Z M of LED-based lighting unit 200 in the OFF mode is essentially the impedance of fusistor 270, which for example, may have a nominal impedance of 300 ⁇ .
  • V A C-OUT ⁇ 0.015 * V A C-OUT- SO
  • V A C IN would be about 1.6 VAC which would cause LED-based lighting unit 200 to be OFF, and thus the LED(s) in LED load 130 would not produce light.
  • traffic light controller 110 turns OFF LED-based lighting unit 200 by switching relay 140 to be open across the 20 kQ load resistor 130, and there is no fault or outage in LED load 230, then traffic light controller 110 will detect AC input voltage 125 as being about 1.6 VAC as explained above, and therefore below the predetermined threshold voltage level (for example, a voltage between 10 VAC and 100 VAC) for detecting a fault or outage. Accordingly traffic light controller 110 will not generate an alarm signal.
  • the predetermined threshold voltage level for example, a voltage between 10 VAC and 100 VAC
  • LED-based lighting unit 200 needs to present a high input impedance Z m to traffic light controller 110 in the OFF mode so as to cause the input voltage V AC -IN detected by to be higher than the predetermined threshold voltage (for example, a voltage between 10 VAC and 100 VAC) so that traffic light controller 110 will detect the outage or fault and may generate an alarm signal or other indication that LED-based lighting unit 200, or at least the LED(s) of LED-based lighting unit 200, needs to be replaced.
  • the predetermined threshold voltage for example, a voltage between 10 VAC and 100 VAC
  • traffic light controller 110 when traffic light controller 110 next (and henceforth) opens relay 140 to cause LED-based lighting unit 200 to be in an OFF mode, switching device 224 is turned off and there is no longer a current path through switch 260 to be turned on, so that the input impedance Z
  • traffic light controller 110 will determine that there is a fault or outage in LED load 230. In that case, traffic light controller 110 may generate an alarm signal or other indication that LED-based lighting unit 200, or at least the LED(s) of LED-based lighting unit 200, needs to be replaced.
  • LED-based lighting unit 200 has determined that there are a number of shortcomings and deficiencies with LED-based lighting unit 200, and particularly the LED driver of LED-based lighting unit 200 with respect to fault or outage detection.
  • a first shortcoming of the LED driver of LED-based lighting unit 200 is that when a fault or outage in LED load 230 is detected, fusistor 270 is blown. That means that it is not possible to test the proper operation of the LED driver, including the proper operation of the outage detection, without blowing fusistor 270 and thereby destroying LED-based lighting unit 200.
  • a second shortcoming of the LED driver of LED-based lighting unit 200 is that it requires two high power MOSFETS - switching device 224 for DC/DC converter 220, and also switch 260 for blowing the fusistor 270. This adds significantly to the size and cost of the LED driver.
  • a third shortcoming of the LED driver of LED-based lighting unit 200 is that outage monitor 250 is always supplied current from the rectified AC input voltage, which contributes to the power loss in the LED driver and thereby decreases its efficiency.
  • a fourth shortcoming of the LED driver of LED-based lighting unit 200 is that outage monitor 250 is required to drive a high power MOSFET (switch 260) which complicates the circuitry.
  • a fifth shortcoming of the LED driver of LED-based lighting unit 200 is that the high power MOSFET (switch 260) has a large junction capacitance and therefore turns off and on slowly, which tends to overload fusistor 270.
  • a sixth shortcoming of the LED driver of LED-based lighting unit 200 is that the voltage measured at the input of LED load 230 in the OFF mode depends on the resistance of fusistor 270. Therefore one or more circuit components of LED-based lighting unit 200 may need to be changed according to AC input voltage levels, for example in different countries.
  • FIG. 3 shows a functional block diagram of one embodiment of an LED-based lighting unit 300 that may be employed, for example, in the traffic light system of FIG. 1, while overcoming one or more of the shortcomings described above.
  • LED-based lighting unit 300 includes, in pertinent part, a rectifier 310, a DC/DC converter and high/low impedance network 320, an LED load 330, a controller 340, a fault detector 350, and a controller disabler 360.
  • the portion of LED-based lighting unit 300 excluding LED load 330 may be referred to as an LED driver 305.
  • LED-based lighting unit 300 may be installed in a traffic light system, such as the traffic light system 100 of FIG. 1.
  • LED-based lighting unit 300 may be retrofit in traffic light system 100 as a replacement for a lighting unit that employs incandescent lamps.
  • LED-based lighting unit 300 may be configured to produce light having one of the three traditional traffic light colors: red, amber or green.
  • a traffic light system may include three LED-based lighting units, one for each of the three traditional traffic light colors all under control of a single traffic light controller.
  • each LED-based lighting unit may be associated with and controlled by its own traffic light controller.
  • LED-based lighting unit 300 An operation of LED-based lighting unit 300 will now be explained with respect to an installation in traffic light system 100. It should be understood, however, that LED-based lighting unit 300 may be employed in other settings and applications, for example in an automotive lighting system or an emergency lighting system.
  • traffic light controller 110 controls LED-based lighting unit 300 to be ON or OFF in accordance with a desired traffic light pattern.
  • Traffic light controller 110 turns ON LED-based lighting unit 300 by switching relay 140 (not shown in FIG. 3) to be connected across 20 kO load resistor 130 (also not shown in FIG. 3). In that case, all or virtually all of AC output voltage 115 of traffic light controller 110 appears as AC input voltage 125 across the input terminals of LED-based lighting unit 300.
  • Rectifier 310 rectifies AC input voltage 125
  • DC/DC converter and high/low impedance network 320 converts the rectified AC input voltage into a desired current and voltage for driving LED load 330.
  • Controller 340 controls DC/DC converter and high/low impedance network 320 to provide the desired output signal to LED load 330 according to well-known algorithms.
  • the output signal of DC/DC converter and high/low impedance network 320 causes the LED(s) in LED load 330 to be lit and produce light of a desired color.
  • Traffic light controller 110 turns OFF LED-based lighting unit 300 by switching relay 140 (again, not shown in FIG. 3) to be open across the 20 kQ load resistor 130 (also not shown in FIG. 3). In that case, AC output voltage 115 is supplied across the input terminals of LED- based lighting unit 300 as AC input voltage 125 according to the voltage divider relationship of Equation (1).
  • fault detector 350 supplies a fault detector output signal 355 to controller disabler 360 whose operation will be explained below.
  • fault detector fault detector 350 causes fault detector output signal 355 to have a first level or voltage (e.g., zero volts) which indicates that there is no fault or outage.
  • controller disabler 360 does not disable controller 340, and therefore controller 340 may operate normally.
  • fault detector 350 when fault detector 350 does detect a fault or outage in LED load 330, then fault detector 350 causes fault detector output signal 355 to have a second level or voltage (e.g., a few volts) which indicates that there is a fault or outage.
  • controller disabler 360 disables controller 340, for exampling by disabling a feedback input of controller 340 for controlling a switching operation of a switching device in DC/DC converter and high/low impedance network 320.
  • traffic light controller 110 determines that there is a fault or outage in LED-based lighting unit 300, and may generate an alarm signal or other indication that LED-based lighting unit 300, or at least the LED(s) of LED- based lighting unit 300, needs to be replaced.
  • FIG. 4 shows a detailed schematic diagram of one embodiment of an LED-based lighting unit that may be employed, for example, in the traffic light system of FIG. 1, with an LED driver whose fault detection may be tested non-destructively.
  • the circuit shown in FIG. 4 may be one embodiment of the LED-based lighting unit 300 of FIG. 3.
  • LED-based lighting unit 400 includes, in pertinent part, a rectifier 410, a DC/DC converter and high/low impedance network 420, an LED load 430, a controller 440, a fault detector 450, and a controller disabler 460.
  • DC/DC converter and high/low impedance network 420 includes a flyback transformer 422 and a switching device 424.
  • switching device 424 is a high power Metal Oxide Semiconductor Field effect Transistor (MOSFET).
  • LED load 430 may comprise one or more LED light sources, including one or more LEDs.
  • the portion of LED-based lighting unit 400 excluding LED load 430 is referred to as the LED driver 405.
  • Controller disabler 460 comprises transistor Q3, which is beneficially a small signal MOSFET.
  • LED-based lighting unit 400 beneficially includes only a single power MOSFET, switching device 424.
  • LED-based lighting unit 400 may be installed in a traffic light system, such as the traffic light system 100 of FIG. 1.
  • LED-based lighting unit 400 may be retrofit in traffic light system 100 as a replacement for a lighting unit that employs incandescent lamps.
  • LED-based lighting unit 400 may be configured to produce light having one of the three traditional traffic light colors: red, amber or green.
  • a traffic light system may include three LED-based lighting units, one for each of the three traditional traffic light colors all under control of a single traffic light controller.
  • each LED-based lighting unit may be associated with and controlled by its own traffic light controller.
  • LED-based lighting unit 400 An operation of LED-based lighting unit 400 will now be explained with respect to an installation in traffic light system 100. It should be understood, however, that LED-based lighting unit 400 may be employed in other setting and applications, for example in an automotive lighting system or an emergency lighting system.
  • traffic light controller 110 controls LED-based lighting unit 400 to be ON or OFF in accordance with a desired traffic light pattern.
  • LED-based lighting unit 400 First, an explanation of the operation LED-based lighting unit 400 will be described in a normal situation where there LED load 430 does not have any open circuit or short circuit fault.
  • Traffic light controller 110 turns OFF LED-based lighting unit 400 by switching relay 140 (not shown in FIG. 4) to be open across the 20 kO load resistor 130 (also not shown in FIG. 4).
  • AC output voltage 115 is supplied across the input terminals of LED-based lighting unit 400 as AC input voltage 125 according to the voltage divider relationship of Equation (1).
  • Resistor R3 of LED-based lighting unit 400 activates switching device 424 to turn on, and the voltage across the input terminals of LED-based lighting unit 400 equals the gate threshold voltage of switching device 424, which is relatively low (e.g., 2-4 volts).
  • LED-based lighting unit 400 With switching device 424 turned on, LED-based lighting unit 400 thereby has an apparent low input impedance (e.g., ⁇ 1 kO).
  • the current in switching device 424 is limited by the external 20 ⁇ load resistor (see FIG. 1).
  • LED-based lighting unit 400 is OFF, and thus the LED(s) in LED load 430 do not produce light. That is, the low voltage of 2-4 volts across the input terminals of LED-based lighting unit 400 does not trigger any circuitry on LED-based lighting unit 400 other than switching device 424.
  • traffic light controller 110 when traffic light controller 110 turns OFF LED-based lighting unit 400 by switching relay 140 to be open across the 20 kQ load resistor 130 and there is no fault or outage in LED load 430, then traffic light controller 110 will detect AC input voltage 125 as being about 2-4 volts as explained above, and therefore less than the predetermined threshold voltage level (for example, a voltage of about 10 VAC or less) for detecting a fault or outage in LED load 430. Accordingly traffic light controller 110 will not generate an alarm signal.
  • the predetermined threshold voltage level for example, a voltage of about 10 VAC or less
  • Traffic light controller 110 turns ON LED-based lighting unit 400 by switching relay 140 (not shown in FIG. 4) to be connected across 20 kQ load resistor 130 (also not shown in FIG. 4). In that case, all or virtually all of AC output voltage 115 of traffic light controller appears as AC input voltage 125 across the input terminals of LED-based lighting unit 400.
  • Rectifier 410 rectifies AC input voltage 125, and DC/DC converter and high/low impedance network 420 converts the rectified AC input voltage into a desired current and voltage for driving LED load 430.
  • Controller 440 receives a DC supply voltage Vcc derived from the rectified AC in put voltage and in response to a zero crossing detection (ZCD) voltage on its ZCD pin, supplies a switching control signal via its CNTL pin to control the switching operation of switching device 424 such that DC/DC converter and high/low impedance network 420 provides the desired DC current to drive LED load 430 according to well-known algorithms.
  • the ZCD input may be a triggering input for receiving a feedback signal for controlling the switching operation of switching device 424.
  • a ZCD input helps to improve the power factor correction and the total harmonic distortion of the input current waveform.
  • the DC current from DC/DC converter and high/low impedance network 420 causes the LED(s) in LED load 430 to be lit and produce light of a desired color.
  • LED-based lighting unit 400 When LED-based lighting unit 400 is turned ON from an OFF state, once AC input voltage 125 goes above 10V, the zener Zl in LED-based lighting unit 400 is activated and the transistor Q7 turns on and discharges the gate voltage of switching device 424. Switching device 424 will remain off until the voltage builds up and controller 440 starts working to control a switching operation of switching device 424. To assure that switching device 424 correctly responds to the switching control signal of controller 440 supplied by the CNTL pin via R7 and Dl, transistor Q6 - which is beneficially a small signal device - also works directly with the gate drive signal. Q6 will always guarantee that the Q7 turns off once the switching control signal from controller 440 becomes high.
  • fault detector 450 supplies a fault detector output signal 455 to controller disabler 460 whose operation will be explained below.
  • fault detector fault detector 450 In normal operation, when fault detector 450 does not detect any fault or outage in LED load 430, then fault detector fault detector 450 causes fault detector output signal 455 to have a first level or voltage (e.g., zero volts) which indicates that there is no fault or outage. In response to fault detector output signal 455 having the first level or voltage (e.g., zero volts), controller disabler 460 does not disable controller 440, and therefore controller 340 may operate normally.
  • first level or voltage e.g., zero volts
  • controller disabler 460 comprises a small signal MOSFET Q3 having a first terminal connected to a fixed voltage (in particular, control ground), a second terminal connected to the ZCD input of controller 440, and a gate connected to receive fault detector output signal 455 from fault detector 450.
  • fault detector 450 does not detect any open circuit or short circuit fault in LED load 430, then fault detector output signal 455 has the first level or voltage (e.g., zero volts) which it supplies to the gate of the MOSFET Q3..
  • the MOSFET Q3 is turned off.
  • controller disabler 460 does not disable or affect the voltage that appears on the ZCD pin of controller 440, and controller 440 operates normally to provide a switching control signal to switching device 424 to control the operation of DC/DC converter and high/low impedance network 420 to supply the desired current and voltage to LED load 430.
  • LED load 430 If LED load 430 is open circuited, the output voltage of the LED driver supplied to LED load 430 increases until the zener diode Z4 conducts, causing the fault detector output signal 455 to have a level or voltage of a few volts, which is supplied to the gate of the MOSFET Q3 of controller disabler 460, thereby turning on the MOSFET Q3. Also, if the LED load is shorted, then the output voltage of the LED driver is zero and the drive to transistor Q4 is removed and therefore Q4 is turned off.
  • fault detector 450 is configured to detect when LED load 430 has a fault, including detecting when LED load 430 has an open circuit condition and detecting when LED load 430 has a short circuit condition, and in response thereto causes the fault detector output signal 455 supplied to the gate of the MOSFET Q3 of controller disabler 460 to have a voltage or level of a few volts, which indicates that LED load 430 has a fault.
  • Vcc voltage supplied to the gate of the MOSFET Q3 of controller disabler 460
  • fault detector output signal 455 supplies a second level or voltage, particularly a high voltage of a few volts, to the gate of the MOSFET Q3 of controller disabler 460 so that the MOSFET Q3 is turned ON.
  • controller disabler 460 When the MOSFET Q3 of controller disabler 460 is turned ON, it shorts the ZCD pin of controller 440 to the fixed voltage (e.g., control ground) and hence disables the ZCD input to controller 440. This in turn prevents controller 440 from supplying the switching control signal to turn on switching device 424, thereby shutting down the LED driver. As a result, LED-based lighting unit 400 provides a high input impedance (e.g., » 20 kO and beneficially > 200 kO) across its input terminals.
  • a high input impedance e.g., » 20 kO and beneficially > 200 kO
  • traffic light controller 110 measures a larger voltage across the input terminals of LED-based lighting unit 400 greater than the predetermined threshold voltage (for example, a voltage > 10 VAC and beneficially > 70 VAC) for detecting a fault or outage in LED load 430. Accordingly traffic light controller 110 determines that there is a fault or outage in LED-based lighting unit 400, and may generate an alarm signal or other indication that LED-based lighting unit 400, or at least the LED(s) of LED-based lighting unit 400, needs to be replaced.
  • the predetermined threshold voltage for example, a voltage > 10 VAC and beneficially > 70 VAC
  • LED-based lighting unit 400 may address one or more of the shortcomings of the LED driver of LED- based lighting unit 200 as described above.
  • the LED driver of LED-based lighting unit 400 does not include a fusistor or other destructive device. So when a fault or outage in LED load 430 is detected, the input impedance of LED-based lighting unit 400 is driven high so as to signal the fault or outage condition, for example to traffic light controller 110, but once the fault or outage is repaired, then the LED driver is able to return to normal operation. That means that it may be possible to test the proper operation of the LED driver, including the proper operation of the outage detection in a factory during manufacturing, and in the filed when it is installed in a traffic light system.
  • the LED driver of LED-based lighting unit 400 requires only one high power MOSFET - switching device 424 for DC/DC converter and high/low impedance network 420. This may significantly reduce the size and cost of the LED driver compared to the LED driver for LED-based lighting unit 200.
  • fault detector 450 is supplied current from the output side of DC/DC converter and high/low impedance network 420, which may reduce the power loss of the LED driver of LED-based lighting unit 400 compared to the LED driver of LED-based lighting unit 200.
  • fault detector 450 is only required to drive a small signal MOSFET in controller disabler 460 which may simply the circuitry compared to the outage monitor 250 in LED-based lighting unit 200.
  • the voltage measured at the input of LED load 230 in the OFF mode depends on the gate junction threshold voltage of switching device 424 which is independent of the AC input voltage level. Therefore the same circuit components for LED-based lighting unit 400 may be employed in applications having different AC input voltage levels, for example in different countries.
  • inventive embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed.
  • inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein.
  • a reference to "A and/or B", when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.
  • the phrase "at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements.
  • This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase "at least one" refers, whether related or unrelated to those elements specifically identified.

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  • Circuit Arrangement For Electric Light Sources In General (AREA)

Abstract

L'invention concerne un pilote (305, 405) qui alimente une charge (330, 430) en énergie, laquelle charge comprenant une ou plusieurs sources lumineuses à diode électroluminescente (DEL). Le pilote comprend : un redresseur (310, 410) destiné à redresser une tension alternative d'entrée; un convertisseur continu-continu (320, 420) comprenant un dispositif de commutation (424) destiné à convertir la tension alternative d'entrée redressée en courant continu pour l'attaque de la charge; et un dispositif de commande (340, 440) destiné à fournir un signal de commande de commutation pour commander une opération de commutation du dispositif de commutation. Le dispositif de commande fournit le signal de commande de commutation en réponse à une tension fournie sur une entrée de retour du dispositif de commande. Le pilote comprend également un détecteur de défaut (350, 450), destiné à détecter si la charge présente un défaut, par exemple un état d'ouverture d'un circuit ou un état de court-circuit, et un moyen d'inhibition de dispositif de commande (360, 460) destiné à inhiber l'entrée de retour du dispositif de commande lorsque le détecteur de défaut détecte un défaut.
PCT/IB2012/053681 2011-07-22 2012-07-19 Pilote de diode électroluminescente à circuit non destructif indiquant la défaillance ou la panne de la charge de diodes électroluminescentes WO2013014580A1 (fr)

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US61/510,524 2011-07-22

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EP3037713A1 (fr) * 2014-12-23 2016-06-29 DB Netz AG Dispositif d'eclairage pour une installation de signal lumineux du trafic ferroviaire
CN107124787A (zh) * 2017-04-07 2017-09-01 广州市河东智能科技有限公司 一种容性灯具的控制装置及方法
EP2966940B1 (fr) * 2014-07-07 2018-04-25 Valeo Vision Système de pilotage de l'alimentation électrique d'une pluralité de sources lumineuses utilisant un convertisseur multiphase
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EP3594556A1 (fr) * 2018-07-13 2020-01-15 HELLA GmbH & Co. KGaA Appareil d'éclairage led pour un véhicule et véhicule doté d'un appareil d'éclairage led
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