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Electric current compensation circuit for brushless motors for reducing ripples in output torques during phase change

  • US 5,821,725 A
  • Filed: 10/16/1996
  • Issued: 10/13/1998
  • Est. Priority Date: 10/16/1996
  • Status: Expired due to Term
First Claim
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1. An electric current compensation circuit for a multiple-phase burshless motor wherein said motor includes a DC power source for supplying power to the motor, a driver for driving the motor, a sensor for detecting a position of magnetic flux in the motor and thereby generating a feedback signal in the form of a compensation current;

  • further wherein said electric current compensation circuit comprises a plurality of electric current compensation loops each for a respective phase and each of said electric compensation loops comprises;

    a first input for receiving a line current from said driver;

    a second input for receiving said compensation current;

    a forward rectifying circuit for forwardly rectifying said line current and said compensation current and outputting a forwardly rectified compensation current;

    a reverse rectifying circuit for reversely rectifying said line current and said compensation current and outputting a reversely rectified compensation current; and

    a summation circuit for summing said forwardly rectified compensation current from said forward rectifying circuit and said reversely rectified compensation current from said reverse rectifying circuit and outputting a synthetic current to a phase winding of said motor;

    whereby each time the phase is changed, said electric current compensation circuit is triggered so as cause said synthetic current to be sent to the motor to allow the motor to generate an output torque with reduced ripple.

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