A New Zero-Voltage Switching Half-Bridge Converter With Reduced Primary Conduction and Snubber Losses in Wide-Input-Voltage Applications

In this paper, a half-bridge (HB) converter, additionally employing a diode compared with the conventional modified duty-cycle-shifted (MDCS) HB converter, is proposed to achieve a high efficiency in wide-input-voltage and low-output-current applications. Since the proposed converter has symmetrical operation, it maintains the advantages such as no transformer dc-offset current, and identical and low-voltage stresses on the secondary diodes. Moreover, due to one additional switch connected in series, the zero-voltage-switching capability of the upper switch is improved. As a result, small resonant inductances are required, which reduces the duty cycle loss, thus the primary conduction losses decrease. In addition, since additional clamping diodes separate external resonant inductor from the resonance path, additional voltage stresses on the secondary diodes can be decreased. Therefore, its snubber loss can be reduced, and it can achieve higher efficiency than that of the MDCS HB converter. To confirm the operation, features, and validity of the proposed converter, a 310–400 V input and 50-V/250-W output laboratory prototype is built and tested.