Multimode Control Scheme for Full-Load Range ZVS of Phase Shift Full-Bridge Converter

This article proposes a multimode control (MMC) scheme to resolve the narrow zero-voltage switching (ZVS) range of the lagging-leg switches in the conventional phase-shifted full-bridge (PSFB) converter. This article analyzes and establishes ZVS process model and then transitions the converter operating mode based on the model to achieve ZVS over the full-load range without the need for resonant inductors and auxiliary circuits. A prototype PSFB converter with a rated output power of 480 W and an output voltage of 13.5 V is designed and implemented in this article with the aim of verifying the accuracy and effectiveness of the model and control scheme. The experimental results demonstrate that the MMC scheme, in comparison to the conventional two-mode control, is capable of filling the ZVS vacuum gap during light load and suppresses hard switching oscillations. Also, the efficiency improves by 0.31%–31.13% during light load.