A ZVS Control Scheme for High-Efficiency Buck–Boost Current-Fed Isolated DC–DC Converter

Buck–boost current-fed isolated dc–dc converter (B3CFIDC) has the advantages of a wide voltage conversion range but cannot achieve zero-voltage switching (ZVS) and zero-current switching (ZCS). In this article, a ZVS control scheme based on discontinuous conduction mode (DCM) and quadrilateral inductor current modulation (QCM) is proposed. Compared with existing control schemes, the proposed ZVS control scheme can achieve wide-range voltage regulation, full range ZVS for all switches, and full range low-current-switching (LCS) turn-off for part of switches by only adding a zero-current detection (ZCD) circuit. Furthermore, the ZVS conditions of all switches and the principle of soft commutation between the buck–boost inductor and the resonant inductor are discussed. To prevent the failure of the soft commutation condition when the resonant inductor current is small, a passive and lossless clamping circuit is also proposed in this article to feedback the commutation energy to the output bus as much as possible with little cost. In addition, a simple implementation of the proposed control scheme in DSP and a robust high-speed ZCD circuit is given. Finally, the proposed ZVS control scheme is verified by detailed experimental results in a 1-kW 98.9% efficiency prototype.