Front-End Bidirectional Symmetric Bipolar Outputs LLC DC-Transformer (DCX) for a Half Bridge Class-D Audio Amplifier

A front-end bidirectional symmetric bipolar outputs (SBOs) LLC dc-transformer (DCX) for half bridge class-D audio amplifier (HB-CDAA) system is proposed and studied in this article. The bidirectional SBO LLC DCX provides SBOs for the HB-CDAA without producing voltage pumping on the outputs of the SBO LLC DCX. The operation of the proposed bidirectional SBO LLC DCX is analyzed, and the effects of the HB-CDAA on the operation of its front-end bidirectional SBO LLC DCX are studied. Soft switching of the proposed bidirectional SBO LLC DCX can be realized both in the positive and negative audio frequency cycles, which improves efficiency of the proposed HB-CDAA system. A 100-W prototype is built up to verify the analysis results. The experimental results show that SBOs are obtained and soft switching of all switches are achieved.