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Motor controller

  • US 7,590,334 B2
  • Filed: 08/08/2007
  • Issued: 09/15/2009
  • Est. Priority Date: 08/08/2007
  • Status: Active Grant
First Claim
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1. A control circuit to control a speed of a motor, comprising:

  • a PWM oscillator configured to generate a PWM output signal having a duty cycle, wherein the speed of the motor is controlled by the PWM output signal to be proportional to the duty cycle; and

    a duty cycle control circuit responsive to a duty cycle selection signal and coupled to the PWM oscillator, the duty cycle control circuit being configured to compare a voltage reference and a supply voltage,wherein the duty cycle control circuit controls the duty cycle of the PWM output signal to be inversely proportional to the supply voltage, andwherein the speed of the motor is substantially constant with respect to variations in the supply voltage.

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