High-efficiency multi-string LED driver based on constant current bus with time-multiplexing control

A high-efficiency multi-string LED driver based on constant current bus with time-multiplexing control scheme is proposed and analysed. Each LED string is connected to the constant current bus, which is provided by the output of a front-end high-efficiency converter. The current of each LED string can be independently controlled by the turn on duty ratio of its time-multiplexing switch. A capacitor is connected to the current bus to provide a current flowing path for constant bus current when none of the LED string is connected to the current bus. It needs only one output filter capacitor, which makes circuit volume small and cost low. Finally, a 7.2 W two-string LED driver is provided to verify the studied results.