Precise current sharing control for multi-channel LED driver based on switch-controlled capacitor

A switch-controlled capacitor (SCC)-based driver circuit is proposed for current sharing of multi-channel light-emitting diode (LED). The proposed circuit includes a transformer primary side and several secondary sides. Each secondary side as an independent unit includes an SCC module, a resonant inductor and an H-bridge to power two-channel LEDs. Two output channels within a capacitor unit achieve current sharing due to charging or discharging balance of SCC module. Since the current in each capacitor unit can be regulated independently, the proposed topology is accommodated with more units. The current sharing among different capacitor units can be realised by the adjustment of SCC module; therefore, the dimming also can be accomplished for multi-channel LEDs. The operating cycles of SCC module, the working mode and simplified equivalent circuit are analysed in detail. The relations of LED current versus the equivalent capacitance are examined. The performance is evaluated by four-channel prototype with input voltage of 48 V and rated power of 20 W. The output current is regulated from 180 to 350 mA per LED channel. The experimental results further prove that the proposed topology can effectively achieve current sharing of two LED channels, current sharing of four-channel LED and independent dimming.