Shunting type PWM dimming circuit for individually controlling brightness of series connected LEDS operated at constant current and method therefor

摘要

A dimming circuit for driving a string of LEDs at constant current has a power converter. A control circuit is coupled to the power converter. A plurality of shunt switches is provided. An individual shut switch is coupled to each LED. Each LED can be shunted individually by the individual shunt switch. The control circuit corrects an internal DC state based on a feedback signal V_O so that the output current of the power converter remains unchanged when at least one LED is shunted.