A new family of active clamp PWM dc-dc converters with ZVS for main switch and ZCS for auxiliary switch

摘要

The objective of this paper is to present a family of PWM dc-dc converters that achieves ZVS (Zero Voltage Switching) for the main switch and ZCS (Zero Current Switching) for the auxiliary switch using a new configuration of the auxiliary circuit cell. It is shown that the proposed auxiliary circuit cell can be used in all three basic dc-dc converters — buck, boost and buck-boost — to transform a PWM hard-switched converter into a low-loss soft-switched equivalent without affecting operation of the original PWM converter. The same auxiliary circuit cell can also be used to implement loss-less switching in other non-isolated or isolated PWM converter circuits such as Cuk, sepic, flyback or forward. The auxiliary circuit of the basic converters includes two additional diodes. These diodes allow clamping of the voltage across the auxiliary switch. In this paper different circuit modes of a ZVS PWM buck converter with the proposed auxiliary circuit are analyzed. The analog circuit that would be required for generation of the switching pulses for the main and auxiliary switches is provided. The experimental results of a 12V, 40W ZVS PWM buck converter with the proposed auxiliary circuit are presented. It shows that for the main switch ZVS and for the auxiliary switch ZCS operations are achieved.