High Efficiency of Asymmetric Half-Bridge Converter with Simple SR Switch Control under Light Load Condition

An asymmetric half-bridge (AHB) converter is commonly utilized in low-power systems. However, due to its asymmetric operation, the AHB converter suffers from degraded efficiency. To improve this drawback, several approaches have proposed a new secondary rectifier structure. Among various rectifier structures, the series capacitor rectifier (SCR) structure has a strong advantage such as the zero dc-offset current and balanced average current of diodes. However, it suffers from weakened energy for zero-voltage switching (ZVS) under light load conditions. In this paper, simple synchronous rectifier (SR) switch control is proposed. The strong point of the proposed converter is that it can simply integrate two different rectifier structures by replacing two diodes with two SR switches. Consequently, the proposed converter can achieve higher efficiency than previous AHB converters. The feasibility of the proposed converter is verified with a 48 V/400 W prototype converter.