Synchronous Rectification for LLC Converter Based on Detecting Resonance Voltage

Abstract

The early or later turned-on and turned-off has existed in the previous synchronous rectification (SR) method that cause the extra loss, emergence of circulating currents and so on. Therefore, an Analog-Digital Mixed Control (ADMC) that drives the SR MOSFETs by detecting resonance voltage has been proposed in this paper. First, the SR method is applied based on the model considering the parasitic capacitance which is closer to real-time dynamic response. Secondly, the driving signal for SR MOSFETs is generated by comparing with the pre-set voltage and the resonance voltage to avoid the disturbance from magnetic inductance and get high-precision performance. Furthermore, this method has combined digital and analog to prevent the mis-conduction which happens in the traditional artificial SR methods. This SR method has been proved by a 400V-36V-lkW prototype.