Dual-switch forward converter with an additional reset capacitor for hold-up operation

An improved scheme of a dual-switch forward converter is proposed in this paper. Compared with the original converter, the new one can provide higher resetting voltage during the hold-up time interval under the action of an additional reset capacitor. Namely, it allows the converter's duty cycle to be larger than 50%. As a result, the proposed method can transfer more energy stored in the bulk capacitor to the load side during the hold-up interval. Therefore, a smaller bulk capacitor can be used for the converter's hold-up time requirement. Since the additional reset capacitor acts only as a compensation, it would not affect other performance of the converter. The additional circuit can be applied for the dual-switch forward converter when small-volume and high power density are required. The working principle and the performance of the converter are analysed, and the relevant theory formulas are deduced. Then the parameters of key components are given. Finally, the theoretical analysis is validated through a 200W experimental prototype.