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Bridge motor driver with short-circuit protection and motor-current limiting feature

  • US 5,457,364 A
  • Filed: 01/18/1994
  • Issued: 10/10/1995
  • Est. Priority Date: 01/18/1994
  • Status: Expired due to Term
First Claim
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1. A full-wave bridge driver of the kind having two DC-supply-voltage terminals, four driver transistors connected in a circuit configured as a transistor bridge having two motor load terminals to which a motor may be connected, said bridge being connected between said two DC-supply-voltage terminals, and a fault detector means connected to said bridge for latching off said four driver transistors when the bridge current drawn by said bridge from said DC-supply terminals jumps essentially instantaneously to exceed a predetermined safe-peak value due to a fault occurring in said bridge;

  • wherein the improvement comprises;

    a) a bridge-current sensing means for producing a bridge-current signal that is proportional to the bridge current;

    b) a comparator means having a predetermined current threshold that is less than said predetermined safe-peak value, connected to said bridge-current sensing means for when the bridge current exceeds said current threshold producing a signal proportional to the difference between the bridge current and said current threshold; and

    c) a pulse-width-modulator means connected to said comparator eans and to said four driver transistors for only during periods when the bridge current exceeds the comparator threshold value, chopping the signal at said control elements of said four driver transistors and varying the chopped pulse widths to hold the bridge current at said threshold current value.

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