High-Power Asymmetrical Half-bridge ZCS Quasi-Resonant Converter

High-power zero-switching converters are the focus in the domain of power electronics, and zero-switching circuit with half-bridge topology has only few types. Half-bridge circuit economizes two power switches and two thick-film drive integrated circuits compared with full-bridge circuit, so the application of half-bridge circuit is increasing when the output power range is from kilowatts to tens kilowatts.Familiar half-bridge circuits mostly use symmetrical structure, and in fact, half-bridge circuits can also use asymmetrical structure. It is reported that the zero-voltage-switching asymmetrical PWM half-bridge converter has been developed. But this converter has some limitations such as low output power, small load varying range, complex control, large filter capacitor which accomplishes the goal of steady output, and it is difficult to maintain soft-switching at light load.In this paper a high power ZCS quasi-resonant converter with asymmetrical half-bridge topology is presented, its main circuit topology and control technique is different from the traditional. Main circuit adopts asymmetrical half-bridge topology. As the resonant supplied by the additive capacitor in the secondary side and the leakage inductance of thetransformer, zero-current-switching from full load to light load is achieved in use of frequency modulation technique.The operation principle and resonant process of the proposed converter is analyzed in detail. The main voltage and current waveforms are given with the equivalent circuits at different time intervals in a half switching cycle. The condition of soft switching is discussed, and the calculating method of resonant elements is deduced. A high power soft-switching inverter welding power supply is developed using the AHB-ZCS-QRC, and it is detailed in four aspects: main circuit design, control circuit design, gate drive circuit design, and auxiliary power supply design. At last, the computer simulation and experiment of the prototype is done to verify the feasibility and validity. The results of simulation and experiment show that the converter owns the advantages of wide soft-switching range and high efficiency.