A simple soft-switched buck converter without implementing auxiliary switch

In this paper, a simple auxiliary circuit is utilized to provide soft-switching condition for the conventional buck converter. The utilized auxiliary circuit contains no switches and without significant additional losses eliminates switching losses completely. This structure contains just one switch which is the conventional buck converter's main switch, and turns on under ZVS condition, and turns off under near to soft-switching condition. Furthermore, the only utilized power diode turns off under ZCS condition. Consequently, switching and reverse recovery losses have been approximately eliminated and the proposed structure operates with high power efficiency. Due to the mentioned features, this converter can be an optimal structure for high-efficiency required applications. In this paper, the operational modes, designing components, power efficiency, and comparison results are discussed in detail. In addition, in order to verify the claimed features, a laboratory prototype of the proposed converter at 175 W output power and 185 kHz frequency is assembled in the laboratory and the results have been investigated completely. In addition, in order to investigate the soft-switching operation of the analyzed structure at light loads, the soft-switching waveforms are achieved for 100 W and 50 W output powers under the same switching frequency.