An improved self-driven synchronous rectifier for high efficiency dimmable LED lighting applications

This paper presents an asymmetrical half bridge (AHB) converter for dimming low-voltage high-current LED lighting application. An improved driving circuit of a self-driven (SD) synchronous rectification (SR) is proposed for switching loss reduction at the secondary of the transformer. The control circuit is designed such that the SR MOSFET switch operates under zero-voltage switching (ZVS) mode while the driving signals are always within the acceptable voltage limits under duty cycle variations of the LED dimming applications. Experimental results obtained from a 60-W prototype have shown that the switches operate under ZVS throughout all operating region where the highest efficiency of the AHB converter is at 96.4%.