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Current control circuit for an electromagnetic type actuator

  • US 5,214,561 A
  • Filed: 10/29/1991
  • Issued: 05/25/1993
  • Est. Priority Date: 11/01/1990
  • Status: Expired due to Term
First Claim
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1. A current control circuit for controlling a current (E) supplied to a coil (3) of an electromagnetic actuator in response to an input pulse signal (A), a duty factor of which corresponds to a target level of the current supplied to said coil, said current control circuit comprising:

  • a) switching means (2) for turning on and off a current supplied to said coil of the actuator; and

    b) means for controlling an average level of the current flowing through the coil such that the target level of the current is maintained irrespective of variations in circuit characteristics of the electromagnetic actuator, including source voltage variations and temperature induced coil resistance variations, said controlling means comprising;

    c) current detector means (4) for detecting a level of current flowing through said coil of the actuator;

    d) peak hold circuit means (6) for holding a voltage level corresponding to each peak level of the current detected by said current detector means;

    e) smoothing circuit means (14) for smoothing said input pulse signal by a predetermined degree;

    f) comparison means (18) for comparing outputs of said peak hold circuit means with said smoothing circuit means, said comparison means outputting a signal when a level of the output (C) of said smoothing circuit means is higher than a level of the output (D) of said peak hold circuit means; and

    g) OR gate means (20), having input terminals coupled to said input pulse signal and an output of said comparison means, said OR gate means turning on said switching means when either said input pulse signal or an output of said comparison means is generated.

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