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Fail safe circuit and battery pack using same

  • US 6,046,575 A
  • Filed: 04/02/1998
  • Issued: 04/04/2000
  • Est. Priority Date: 03/31/1998
  • Status: Expired due to Fees
First Claim
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1. A fail safe circuit for a battery pack having at least one battery cell for providing a battery voltage, the fail safe circuit comprising:

  • a fuse electrically coupled in series with the at least one battery cell and having a current rating;

    a current shunt switch coupled in across the fuse and the at least one battery cell for shunting current from the at least one battery cell through the fuse; and

    a critical voltage control circuit operably coupled to the current shunt switch for controlling a switch state of the current shunt switch;

    wherein the critical voltage control circuit places the current shunt switch in an open switch state while the battery voltage is below a critical voltage level and places the current shunt switch in a closed state upon the battery voltage reaching the critical voltage level; and

    wherein upon being placed in the closed switch state, the current shunt switch conducts current in excess of the current rating of the fuse, thereby causing the fuse to open.

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