Self-driven schemes for 12V self-driven voltage regulator

Compared with conventional multi-phase buck converter, the 12V ZVS self-driven non-isolated full-bridge converter has many advantages for voltage regulator module (VRM) applications. The employment of the synchronous rectifier (SR) self-driven technology in VRs leads to lower SR drive loss and body diode conduction loss. However, the SR drive voltage is fixed at the input voltage, which is too high to increase the light-load efficiency and to further decrease drive loss. This paper proposes three different SR self-drive methods that allow the SR driver voltage to be lowered from the input voltage to an optimized voltage to help increase the overall efficiency. 1U 700kHz VR prototypes were built in the lab to implement different SR drive methods. The auto transformer drive method is found to be the best candidate, and achieved 88.2% efficiency at 1.2V/130A output. The experimental result verifies the theoretical analysis.