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Voltage clamp circuit for switched inductive loads

  • US 4,658,203 A
  • Filed: 03/07/1986
  • Issued: 04/14/1987
  • Est. Priority Date: 12/04/1984
  • Status: Expired due to Fees
First Claim
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1. In a control system in which a current is passed through an inductive load by controlling an electronic switch means in series with said inductive load across a power supply by opening and closing said switch with a control voltage on a control voltage lead;

  • the improvement comprising means to clamp the inductive voltage generated by said inductive load as said current flowing through said load is cut off by the opening of said electronic switch means with said control voltage, said clamp means further comprising;

    (a) circuit means having a first terminal connected to the junction of said load and switch; and

    a second terminal connected to said control voltage lead; and

    (b) said circuit means having a Zener diode and a simple diode connected in series with either their cathodes together, or their anodes together, and the cathode of said simple diode connected toward said control voltage lead, and the cathode of said Zener diode connected toward said first terminal;

    whereby when the control voltage is removed from said electronic switch means, said electronic switch means opens, and an inductive voltage peak appears on said first terminal;

    current flows in reverse through said Zener diode and through said simple diode thereby generating a control voltage to turn on said electronic switch means passing current through said switch until the inductive voltage is dissipated;

    removing said generated voltage from said control lead and opening said electronic switch means until the next load carrying cycle begins.

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