A ZVS Control Scheme for High-Efficiency BuckBoost Current-Fed Isolated DCDC 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.