A Variable Frequency ZVS Control of a Three-level Buck without Zero Crossing Detection for Wide-Range Output Voltage Battery Chargers

In this paper, a variable frequency soft-switching control for a three-level half bridge (TLHB) buck converter is proposed to achieve wide-range output battery charging function without losing zero voltage switching (ZVS) or high efficiency. The adopted variable frequency triangle-current-modulation (TCM) is based on dc measurement and average-model calculation, thus able to realize ZVS operation fully digitally without current zero-crossing-detection (ZCD) circuits. A top-level average current or output voltage feedback controller further ensures the desired power or output voltage regulation. Experimental results from a GaN based TLHB prototype have shown the reliable TCM control and smooth transition of ZVS operation through the charging procedure.