MHz Level Two-Stage ZVS DC-DC Converter with Wide Input and Output Voltage Ranges

This paper develops a high frequency ZVS 500-W wide-input-range (200-400V) and wide-output-range (10-14V) isolated dc-dc converter for applications where high efficiency, high density and a wide voltage range are usually strongly required. The first stage is a non-isolated four-switch buck-boost (FSBB) step-up and step-down dc-dc converter with GaN devices. The quadrangle current modulation method of inductor current is applied to achieve zero voltage switching with minimized rms current algorithm. In terms of the step-up and step-down abilities of FSBB stage, a cellular MHz SRC (series resonant converter) DCX (dc transformer) is adopted in the downstream stage, where low-voltage and low-NFoM (new figure of merit, NFoM = Rdson×Coss) device are utilized to achieve high efficiency and high density with ultra-low switching loss and optimized conduction loss. A resonant driver is used to shrink the large driving loss and improve light load efficiency. Finally, the proposed dc-dc converter achieves a peak full load efficiency of 96.6% with a power density of 240 W/in ³ considering the heatsink.