Soft Switching Symmetric Bipolar Outputs DC-Transformer (DCX) for Eliminating Power Supply Pumping of Half-Bridge Class-D Audio Amplifier

A soft switching symmetric bipolar outputs dc-transformer (DCX) for eliminating power supply pumping of half-bridge class-D audio amplifiers is proposed in this paper. Compared with the traditional unidirectional front-end dc–dc converter in the half-bridge class-D audio amplifier, output capacitances of the proposed DCX and voltage stress of the half-bridge class-D audio amplifier are significantly reduced. Soft switching of the proposed DCX can be achieved when the load current of half-bridge class-D audio amplifier is positive or negative. Thus, the efficiency and power density of the proposed audio amplifier system can be improved. In addition, the proposed DCX has smoothing transition between the positive load current and the negative load current with a simple open-loop controller. The operating principle of the proposed DCX is analyzed and a 200-W prototype is built up. Experimental results show that power supply pumping is reduced with small DCX output capacitors, symmetric bipolar outputs are obtained and peak efficiency of 96.3% is achieved.