High frequency transformer assisted a new passive clamp ZVS quasi-resonant DC-link PWM inverter with low voltage stress across the switches

This paper presents a new passive clamp quasi-resonant DC-link (QRDCL) PWM inverter with zero voltage switching (ZVS) capability and easier control. The proposed quasi-resonant circuit creates zero voltage intervals in the DC-link to facilitate ZVS of the inverter switches under all operating conditions, This is achieved with the DC link voltage being clamped at the clamping voltage K_cV_s (where K_c, is the clamping factor) using minimum additional components. It requires only one additional switch, a passive clamp and a high frequency transformer compared to the conventional PWM converter and it has the ability of controlling the zero voltage time of the DC-link without the intervention of the inverter switches. Moreover, the control circuit does not require any current/voltage sensing devices, thereby, making the control circuit simple and cheap. The operating principle of the circuit is explained and detailed analysis of each operating mode is given. A design criterion for achieving ZVS is obtained from the mathematical analysis. The feasibility of the proposed circuit operation has been verified by PSPICE simulation. The simulation results show full ZVS for both the proposed circuit and the PWM inverter