Design of a High-to-Low Voltage, Low-Power, Isolated DC/DC Converter for EV Applications

The design of a low-cost 800–12 V, 4 W isolated dc/dc converter for automotive applications is investigated. Such a converter is required to supply tiny systems directly from the high-voltage battery of an electric vehicle. In particular, a selected topology based on a multilevel flying-capacitor stage is analyzed. The converter operating mode selection is studied and simulation results reveal the interest of operating at the limit of the zero voltage switching (ZVS) mode. The design of a planar transformer adapted to the application is described. Design considerations of an IC brick that includes the main blocks required to control the power stage are discussed. The performances of a 4-W prototype with two transformer designs validate the choice of the operating mode. The peak efficiency is 87.4% which confirms the interest of the selected approach compared to existing solutions.