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Switching device with power FET and short-circuit detection

  • US 5,914,545 A
  • Filed: 05/09/1997
  • Issued: 06/22/1999
  • Est. Priority Date: 05/11/1996
  • Status: Expired due to Fees
First Claim
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1. A circuit arrangement for protecting against an overload an FET power switch (1) having a drain terminal (D), a source terminal (S), and a gate terminal (G), comprising a load (5) connected to said drain terminal (D) and to an operating voltage source (UB), a short circuit detector (DT) having an input connected to said source terminal (S), a microcontroller (9A) for controlling said FET power switch (1), said short circuit detector (DT) having an output (INT) connected to a control input of said microcontroller (9A) for supplying a control signal representing a short circuit to said control input of said microcontroller, a series resistor (9) connecting a control output of said microcontroller to said gate terminal (G), a gate terminal voltage limiter diode (7) connected to said gate terminal (G) and to a constant clamping voltage, and a shunt resistor (3) connected between said source terminal and ground for cooperation with said gate terminal voltage limiter diode (7) in limiting a short circuit current flowing through said FET power switch at least until said FET power switch (1) is switched off by said control signal in response to a short circuit.

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