A Power Supply and High-Voltage Blocking Sensing Circuit for High Voltage Synchronous Rectifier

Commercial synchronous rectifier (SR) ICs usually have a limited V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</inf> (drain-source voltage) rating of about 200V, which will restrict their applications in high-voltage SR circuits. This paper proposes a novel power supply and high-voltage blocking sensing circuit for high voltage SRs, which is improved on the basis of traditional transistor series voltage regulator power supply circuits and realizes the high-voltage blocking of the detected high V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</inf> without sacrificing the detection accuracy. Meanwhile, the proposed circuit has low cost and high versatility, and can be applied to existing commercial SR control ICs, which greatly reduces the input sense voltage of the SR controller on the one hand, and supplies power for SR IC on the other. Finally, the proposed power supply and high-voltage blocking sensing circuit is verified on a 720kHz flyback converter with ON Semiconductor's NCP4306 SR control IC.