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Load drive device having short-circuit protection function

  • US 5,986,442 A
  • Filed: 07/06/1998
  • Issued: 11/16/1999
  • Est. Priority Date: 10/27/1997
  • Status: Expired due to Term
First Claim
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1. A load drive device having a short-circuit protection function which drives an electric load in response to a drive signal, comprising:

  • a switching element coupled in series to said load and operating in response to said drive signal;

    a power source which supplies a voltage to a series circuit of said load and said switching element;

    a voltage detection circuit which detects a voltage exertion on to said load so as to generate a voltage exertion detection signal; and

    a short-circuit protection circuit which interrupts a supply of said drive signal to said switching element in case no voltage exertion detection signal is generated at the expiration of a predetermined period of time from an initiation of the supply of said drive signal, wherein said short-circuit protection circuit comprises a time constant circuit including a capacitor to be charged by a voltage level of said drive signal;

    a transistor turned on when a charged voltage level of said capacitor exceeds a predetermined level, thereby interrupting supply of said drive signal to said switching element; and

    discharging means for discharging a storage energy of said capacitor when said voltage exertion detection signal appears.

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