An Efficient Soft-switching Buck Converter with Parasitic Resonance Suppression in Auxiliary Circuit

In this paper, a new efficient soft-switching synchronous rectification (SR) buck converter is proposed, which is without voltage stress increment for all switches and diodes. By introducing an auxiliary circuit to the SR buck converter, soft-switching condition is achieved within the wide range of load power for the power semiconductor devices. The auxiliary network, which consists of capacitor, inductor, switch and three diodes, provides a zero-voltage condition for main switch and SR switch at both the turn-on and the turn-off instant. Besides, the auxiliary inductor creates a zero-current turn-on and a zero-voltage turn-off condition for the auxiliary switch. Considering the resonance between the parasitic capacitors of the semiconductor components and the auxiliary inductor, two diodes are designed to avoid the additional voltage stress on power devices. The operating principle of this proposed converter is analyzed. A 600 W prototype is implemented to test the soft-switching operation. The advantage of the proposed converter is demonstrated by the efficiency curve over a wide range of load power against the conventional SR buck converter.