A 1 MHz bi-directional soft-switching DC-DC converter with planar coupled inductor for dual voltage automotive systems

The 48V - 14V automotive power system is gaining acceptance - due to the increasing number and power rating of electrical and electronic components in vehicles to support advanced functionalities. Multiphase synchronous bi-directional buck/boost converter is currently employed for connecting two bus voltages. However, it has low efficiency at high frequency operation and high EMI noise due to its hard-switching. A zero-voltage transition bi-directional buck/boost converter with coupled inductor is proposed for this application, which provides ZVS for main switches and ZCS for auxiliary switches, and features wide ZVS range and low loss in auxiliary branch. The operating principles including ZVS/ZCS mechanism, details of circuit design, and experimental results from a 1 MHz and 250 W prototype are presented.