Evaluation of Self-Driven Schemes for a 12-V Self-Driven Voltage Regulator

Compared to the conventional multiphase buck converter, the 12-V zero-voltage switching self-driven nonisolated full-bridge converter has many advantages for voltage regulator (VR) module 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 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. 1 Unit Height (1U) 700 kHz VR prototypes were built in the laboratory to implement different SR drive methods. The autotransformer drive method is found to be the best candidate, and achieved 88.2% efficiency at 1.2 V/130 A output. The experimental result verifies the theoretical analysis.