Single-ended primary inductance converter (SEPIC) based power supply for driving multiple strings of light emitting diodes (LEDs) in roadway lighting fixtures
First Claim
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1. A power supply for providing a constant current to a light emitting diode (LED) load, the power supply comprising:
- a power controller receiving an alternating current (AC) input and providing a direct current (DC) output voltage controlled to maintain a constant feedback voltage, the DC output voltage provided to a high side of the LED load, the DC output voltage relative to a common power line coupled to a low side of the LED load and the power controller;
a current sense resistor connected in series on the high side of the LED load;
a current sensing circuit coupled across the current sense resistor providing a reference current at an output line proportional to a current sense voltage across the current sense resistor; and
a current selector resistor coupled between the output line of the current sensing circuit and the common power line coupled to the low side of the LED load, the current selector resistor and the reference current generating a current-sensed voltage for use as the feedback voltage used by the power controller;
wherein the DC output voltage provided by the power controller is controlled to provide a constant current to the LED load.
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Abstract
A lighting fixture and power supply are provided that allows a power factor correction (PFC) single ended primary inductance controller (SEPIC) that provides a controlled voltage output to provide a constant current to an LED load. The power supply provides an efficient and stable power supply for LEDs. Multiple power supplies can be provided on the same printed circuit board to control multiple LED channels.
25 Citations
24 Claims
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1. A power supply for providing a constant current to a light emitting diode (LED) load, the power supply comprising:
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a power controller receiving an alternating current (AC) input and providing a direct current (DC) output voltage controlled to maintain a constant feedback voltage, the DC output voltage provided to a high side of the LED load, the DC output voltage relative to a common power line coupled to a low side of the LED load and the power controller; a current sense resistor connected in series on the high side of the LED load; a current sensing circuit coupled across the current sense resistor providing a reference current at an output line proportional to a current sense voltage across the current sense resistor; and a current selector resistor coupled between the output line of the current sensing circuit and the common power line coupled to the low side of the LED load, the current selector resistor and the reference current generating a current-sensed voltage for use as the feedback voltage used by the power controller; wherein the DC output voltage provided by the power controller is controlled to provide a constant current to the LED load. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A lighting fixture for mounting above an illumination surface, the lighting fixture comprising a housing supporting:
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a light emitting diode (LED) light string for illuminating the illumination surface; and a power supply for providing a constant current to a light emitting diode (LED) load, the power supply comprising; a power controller receiving an alternating current (AC) input and providing a direct current (DC) output voltage controlled to maintain a constant feedback voltage, the DC output voltage provided to a high side of the LED load, the DC output voltage relative to a common power line coupled to a low side of the LED load and the power controller; a current sense resistor connected in series on the high side of the LED load; a current sensing circuit coupled across the current sense resistor providing a reference current at an output line proportional to a current sense voltage across the current sense resistor; and a current selector resistor coupled between the output line of the current sensing circuit and the common power line coupled to the low side of the LED load, the current selector resistor and the reference current generating a current-sensed voltage for use as the feedback voltage used by the power controller; wherein the DC output voltage provided by the power controller is controlled to provide a constant current to the LED load. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method of controlling a lighting fixture, the method comprising:
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rectifying an alternating current (AC) input; producing a controlled voltage output from the AC input using a single ended primary inductance converter; producing a sensing current proportional to the controlled voltage output using a current sense resistor in series with the controlled voltage output and a current sensing circuit connected across the current sense resistor; generating a feedback voltage using the sensing current and a current selector resistor; and adjusting the controlled voltage output to maintain the feedback voltage at a reference voltage, wherein the controlled voltage output provides a constant current to an light emitting diode (LED) load. - View Dependent Claims (22, 23, 24)
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Specification