High efficiency asymmetrical half-bridge converter using new rectifier with an active-clamp cell

Abstract

In this paper, a new asymmetrical half-bridge (AHB) converter using new rectifier with an active-clamp cell is proposed. The AHB converter is one of the popular topologies in low power applications due to small number of components, ZVS capability, and small output filter size. However, when the AHB converter is designed in wide input voltage range to satisfy the hold-up time requirement, it operates with small duty ratio in nominal state and has a small turns-ratio of transformer which causes several problems such as large DC offset current, poor ZVS condition, and large conduction losses. To solve these problems, the proposed converter uses an active-clamp cell in rectifier. The active-clamp cell not only clamps the voltage stress of a diode, but also makes additional voltage gain for the hold-up time. Therefore, the proposed converter can be designed regardless of hold-up time which enables to be operated with large duty ratio in nominal state and has a large turns-ratio of transformer. Therefore, the proposed converter has a high efficiency in entire load conditions. The effectiveness of the proposed converter is verified with a 19.5V/10.25A prototype converter.