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DC/DC converter having a bootstrapped high side driver

  • US 5,627,460 A
  • Filed: 12/28/1994
  • Issued: 05/06/1997
  • Est. Priority Date: 12/28/1994
  • Status: Expired due to Term
First Claim
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1. A step-down converter for converting an input voltage to a lower output voltage, said converter comprising:

  • a pair of NMOS switches coupled in series, a first one of said switches being coupled to said input voltage and a second one of said switches being coupled to ground;

    an output filter coupled to said pair of switches, said output filter providing an output terminal at which said output voltage is provided;

    a bootstrap capacitor charged by said input voltage through a path including said second switch and having a bootstrap voltage thereacross; and

    a control circuit receiving a signal indicative of said output voltage and providing gate drive signals to each of said pair of switches to control the duty cycles of said switches so as to maintain said output voltage substantially constant, said control circuit including a sensor for sensing said bootstrap voltage and increasing the duty cycle of said second switch in response to said bootstrap voltage being below a first predetermined level and said first switch being closed.

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