LED CONTROL METHOD AND STRUCTURE
First Claim
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1. A power factor LED control system comprising:
- a plurality of series coupled LEDs coupled to receive an LED current between an input and a first common return;
an error amplifier coupled to form an error signal that is representative of the LED current; and
a PWM controller coupled to receive a signal that is representative of the LED current and control the LED current to a substantially constant value wherein the PWM controller is coupled between the first common return and a second common return to receive an operating voltage for the PWM controller wherein the PWM controller does not sense a waveshape of an AC input voltage received by the power factor LED control system.
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Abstract
In one embodiment, an LED system is controlled to have a substantially unity power factor.
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Citations
20 Claims
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1. A power factor LED control system comprising:
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a plurality of series coupled LEDs coupled to receive an LED current between an input and a first common return; an error amplifier coupled to form an error signal that is representative of the LED current; and a PWM controller coupled to receive a signal that is representative of the LED current and control the LED current to a substantially constant value wherein the PWM controller is coupled between the first common return and a second common return to receive an operating voltage for the PWM controller wherein the PWM controller does not sense a waveshape of an AC input voltage received by the power factor LED control system. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A power factor LED control system comprising:
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a plurality of series coupled LEDs referenced to a first common reference signal; an error amplifier coupled to provide an error signal that is representative of a current through the plurality of series coupled LEDs wherein the error amplifier is referenced to the first common reference signal; and a PWM controller operably coupled to receive a signal that is representative of the current through the plurality of series coupled LEDs and form a substantially dc voltage for operating the plurality of series coupled LEDs wherein the PWM controller is configured to operate at a substantially fixed frequency and a substantially constant duty cycle and wherein the PWM controller is referenced to a second common reference signal. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A method of forming an LED system comprising:
configuring a control system to operate a PWM controller to control a current through a plurality of series coupled LEDs to a substantially constant value wherein the PWM controller is configured to operate with a substantially constant frequency and a substantially constant duty cycle. - View Dependent Claims (17, 18, 19)
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20. A method of forming an LED system comprising:
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configuring the LED system in a boost configuration; coupling a plurality of LEDs in series; and configuring the LED system to form a waveform of an input current to the LED system to be substantially equal to a current waveform through a power switch that regulates current through the plurality of LEDs wherein the power switch operates at a substantially constant frequency and a substantially constant duty cycle.
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Specification