A New Center-Tapped Half-Bridge Zeta Converter With Small Transformer DC-Offset Current and Low Voltage Stress

In this paper, an asymmetrical half-bridge (AHB) converter employing a new center-tapped zeta rectifier (CTZR) is proposed to achieve a high efficiency in wide-input-voltage and low-output-current applications. Due to the proposed CTZR with high dc conversion ratio and extended maximum duty cycle above 0.5, the transformer turns ratio of the proposed converter can be increased, which decreases the transformer dc-offset current compared with that of the AHB converter. Therefore, its transformer core size is decreased. Moreover, it has a wide zero-voltage-switching range with small transformer leakage inductor, which improves light and medium load efficiency. Furthermore, since it has low voltage stress on the secondary diode, its conduction loss can be reduced. In addition, due to the elimination of a diode, the snubber loss in the secondary side is reduced compared with the AHB converter. Therefore, the proposed converter can achieve a higher efficiency compared with the AHB converter without additional devices. To confirm the operation, features, and validity of the proposed converter, a 250-400 V input and 50 V/250 W output laboratory prototype is built and tested.