A High-Speed Synchronous Rectifier With Improved Dead Time Compensation and Suitable for High-Voltage Applications

VDS (drain-source voltage)-based synchronous rectifiers (SRs) are widely used due to their simplicity and low cost. However, there are still three obvious issues. 1) The premature turn-OFF caused by parasitic inductance under high frequency. 2) The turn-ON propagation delay is typically tens of nanoseconds. 3) Commercial SRs usually have a limited VDS rating of about 200 V. To solve the above problems, a high-speed SR (including a customized SR IC and a peripheral circuit) is proposed. A high-speed comparator together with a slope detection circuit is proposed to reduce the turn-ON delay, and the proposed fully integrated SR IC is implemented in a 1-mu m bipolar process with a die area of 1.47 x 1.98 mm(2). The peripheral circuit contains the improved dead time compensation circuit, the self-driven high-voltage isolation circuit, and the power supply circuit for SR IC, and the component count is reduced by device reuse. In a 200-W Double clamp zero voltage switching (DCZVS) buck-boost converter prototype, the proposed SR can achieve a switching frequency of more than 700 kHz with minimal dead time, the turn-ON propagation delay including peripheral circuits and SR IC is reduced to 8.1 ns, the isolated drain-source voltage is limited to within 10 V, and the peak efficiency is 93.6%.