Asymmetrical zero-voltage-switching PWM DC-DC converter employing two transformers and current doubler rectification

A new zero-voltage-switching (ZVS) PWM DC-DC converter with two switches driven by asymmetrical duty cycles is presented. Two small transformers with the same turns ratio instead of one large transformer are used to fulfil the low-profile design. The current doubler rectifier can reduce the current ripple in the output capacitors. The leakage inductance of the transformer or an additional resonant inductance helps to achieve ZVS during the dead times. Therefore high conversion efficiency can be obtained. The maximum duty cycle can be extended to be above 50%. Thus, the proposed converter is suitable for the applications with a wide input voltage range. Detailed analysis and design of the presented ZVS PWM DC-DC converter are described. Experimental results are recorded for a prototype converter with a DC input voltage of 120-190-V, an output voltage of 12-V and a load current of 12-A, operating at a switching frequency of 180-kHz.