Dual Half-Bridge LLC Resonant Converter with Hybrid-Secondary-Rectifier (HSR) for Wide-Ouput-Voltage Applications

In this paper, a dual half-bridge (HB) LLC resonant converter with a new hybrid secondary rectifier (HSR) is proposed for wide-output-voltage applications. In the proposed converter, the HSR can operate like a voltage doubler rectifier or voltage quadrupler rectifier according to the switching strategy of the dual HB LLC resonant converter. For low output voltage range, the dual HB LLC resonant converter are controlled by 180 degree phase-shifted gate signals. Thus, it can achieve low voltage gain with a voltage doubler rectifier. Whereas, in high output voltage range, in-phase gate signals are applied to the dual HB LLC resonant converter. Thus, the proposed converter can obtain high voltage gain with a voltage quadrupler rectifier. As a result, the proposed converter is able to be designed with narrow switching frequency variation, which results in high efficiency over the entire output voltage range. The validity of the proposed converter is confirmed by a 750W prototype with 400V input, 100-300V output.