SHUNTING TYPE PWM DIMMING CIRCUIT FOR INDIVIDUALLY CONTROLLING BRIGHTNESS OF SERIES CONNECTED LEDS OPERATED AT CONSTANT CURRENT AND METHOD THEREFOR

摘要

A Pulse Width Modulation (PWM) dimming circuit for individually controlling brightness of series connected Light Emitting Diodes (LEDS) operated at constant current has a first plurality of switching devices, a signal switching device of the first plurality coupled to an individual LED of series connected LEDS to control a brightness of the individual LED by periodically shunting the individual LED. A power converter supplies a constant output current to the series connected LEDs. Control circuitry is coupled to the power converter, wherein the control circuit corrects an internal DC state based on a feedback signal VO so that the output current of the power supply remains unchanged when at least one LEDs is shunted.