A novel zero-voltage-switching converter using a coupled inductor

A novel zero-voltage-switching converter using a coupled inductor is presented and evaluated in details by analysis and experiment. The presented circuit employs a simple active energy recovery circuit which can be magnetically coupled to a conventional ZVS-PWM half-bridge converter to achieve zero-voltage switching of the lower switch of the bridge after the off period of both switches. Due to the refined mechanism, using a coupled inductor, this magnetic feedback technique has some advantages like low peak values of partial-resonant current and the current in the auxiliary circuit after ZVS decreases fast to zero. Thus, the converter using this ZVS technique exhibits the low voltage and current stresses characteristic of hard-switched PWM converters, yet achieves ZVS. Based on this technique, an experimental 5 kW, 35 kHz laboratory prototype is designed for on-board electric vehicle charger. The prototype charger achieved a remarkable maximum overall efficiency of 95% at full load and it is operated high efficiency exceeding 90% at entire load range