A 1-MHz, 12-V ZVS Nonisolated Full-Bridge VRM With Gate Energy Recovery

In this paper, a new self-driven zero-voltage-switching (ZVS) nonisolated full-bridge converter is presented for 12-V input VRM applications. The advantages of the new circuit are: 1) duty cycle extension; 2) ZVS of all the control MOSFETs; 3) lower voltage stress and reduced reverse recovery loss of the synchronous rectifier (SR) MOSFETs; 4) high-drive voltage to reduce R DS( ON) and the conduction loss of the SRs due to gate energy recovery capability; and 5) reduced body-diode conduction and no external drive IC chips with dead time control needed for SRs. Existing multiphase buck controllers and buck drivers can be directly used in the proposed converter. The experimental results verify the principle of operation and significant efficiency improvement. At 12 V input, 1.3 V output voltage, and 1 MHz switching frequency, the proposed converter improves the efficiency, using the buck converter from 80.7% to 83.6% at 50 A, and from 77.9% to 80.5% at 60 A. With two parallel SRs, the efficiency is further improved from 83.6% (single SR) to 84.7% (two SRs) and at 60 A, the efficiency is improved from 80.5% (single SR) to 83.2% (two SRs).

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