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Constant current source and battery charger

  • US 4,885,522 A
  • Filed: 11/16/1988
  • Issued: 12/05/1989
  • Est. Priority Date: 12/02/1987
  • Status: Expired due to Fees
First Claim
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1. A battery charger operated from a single-ended power supply comprising:

  • pulse width modulation means including a transistor power switch, a diode and an inductor for supplying current to a battery;

    means for monitoring current flow to said battery;

    trigger means for controlling the frequency and duty cycle of said pulse width modulation means responsive to said monitoring means;

    a speed up circuit for said switch transistor comprising a shorting transistor coupled across the base-emitter circuit of said switch transistor and means responsive to said trigger means for driving said shorting transistor conductive;

    current foldback means including zener diode sensing means for monitoring the voltage of said battery; and

    means for changing said monitoring means to substantially reduce current flow to said battery when a battery voltage corresponding to a fully charged state is reached.

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