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Off-line bootstrap startup circuit

  • US 5,477,175 A
  • Filed: 10/25/1993
  • Issued: 12/19/1995
  • Est. Priority Date: 10/25/1993
  • Status: Expired due to Term
First Claim
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1. An off-line bootstrap circuit being responsive to a line voltage for providing a bias voltage to an integrated circuit, the off-line bootstrap circuit comprising:

  • a high voltage device having first and second current carrying terminals and a control terminal, said first current carrying terminal of said high voltage device being connected for receiving the line voltage, said second current carrying terminal of said high voltage device being coupled for providing the bias voltage, said high voltage device including,(a) a first transistor for extending a range of the bias voltage, said first transistor having first and second current carrying electrodes and a control electrode, said second current carrying electrode coupled for providing the bias voltage, said control electrode of said first transistor coupled to said control terminal of said high voltage device, and(b) a second transistor having first and second current carrying electrodes and a control electrode, said first current carrying electrode connected for receiving the line voltage, said second current carrying electrode connected to said first current carrying electrode of said first transistor, said control electrode of said second transistor coupled to a first supply voltage terminal wherein said first current carrying electrode of said first transistor is merged in a common region with said second current carrying electrode of said second transistor;

    control means having an output coupled to said control terminal of said high voltage device and responsive to a control signal for rendering said high voltage device inoperative when the bias voltage has exceeded a predetermined threshold; and

    a switching transistor having a first electrode coupled to said output of said control means for receiving a switching signal, a second electrode coupled to said first supply voltage terminal, and a third electrode connected to the line voltage.

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