Electronic rheostat method and apparatus

  • US RE35,428 E
  • Filed: 06/19/1992
  • Issued: 01/21/1997
  • Est. Priority Date: 08/02/1988
  • Status: Expired due to Term
First Claim
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1. A .Iadd.vehicle .Iaddend.power control circuit for regulating energizing power coupled to a device in a motor vehicle comprising:

  • (a) a .[.d.c..]. .Iadd.vehicle .Iaddend.voltage source for supplying energizing .[.the device.].power;

    (b) oscillator means for generating an oscillating voltage waveform that varies between a maximum and a minimum voltage;

    (c) comparator means for comparing the oscillating voltage waveform from the oscillator means with a reference voltage to produce a pulse width modulated output whose duty cycle varies as a function of the reference voltage; and

    (d) drive means coupled to the pulse width modulated output of the comparator means for coupling the device to the d.c. voltage source in synchronism with the pulse width modulated output;

    (e) said comparator means including a reference voltage divider circuit connected to the d.c. voltage source including adjustment means to allow a user to adjust the reference voltage and .[.control.]. .Iadd.to vary .Iaddend.the average voltage applied to the device by the drive means.

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