Overcurrent protection method for composite power semiconductor switches
Various examples are provided related to overcurrent protection for composite power semiconductor switches comprising a high voltage power switch in series with a low voltage non-linear element. In one example, a system includes a blocking diode connected to a sensing node of a composite switching device; a resistor connected in series with the blocking diode and to a desaturation detection input of a gate driver circuit; and a blanking capacitor connected between the desaturation detection input and a common voltage reference of the gate driver circuit. The gate driver circuit can detect a short circuit condition based upon a sensed voltage at the desaturation detection input. In another example, a method includes sensing a voltage on a blanking capacitor, the voltage provided from a sensing node of a composite switching device via a blocking diode and a resistor, and detecting a short circuit condition based upon the sensed voltage.
1 . A system for overcurrent protection, comprising:
a blocking diode directly connected to a sensing node of a composite switching device, the sensing node coupled between a high voltage power switch and a low voltage nonlinear element of the composite switching device;
a resistor connected in series with the blocking diode, the resistor connected to a desaturation detection input of a gate driver circuit of the composite switching device; and
a blanking capacitor connected between the desaturation detection input and a common voltage reference of the gate driver circuit, wherein the gate driver circuit detects a short circuit condition based upon a sensed voltage at the desaturation detection input.
2 . The system of claim 1 , wherein detection time of the short circuit condition is based upon size of the blanking capacitor.
3 . The system of claim 1 , wherein gating of the high voltage power switch is controlled based upon detection of the short circuit condition.
4 . The system of claim 1 , wherein the high voltage power switch is a Silicon MOSFET, Silicon IGBT, Silicon Carbide MOSFET or Gallium Nitride HEMT device.
5 . The system of claim 1 , wherein the common voltage reference of the gate driver circuit is connected to a source of the composite switching device.
6 . The system of claim 5 , wherein the low voltage nonlinear element is connected between the high voltage power switch and the source of the composite switching device.
7 . The system of claim 1 , wherein the composite switching device is a bidirectional composite switching device.
8 . The system of claim 7 , wherein the bidirectional composite switching device comprises a second high voltage power switch and a second low voltage nonlinear element.
9 . The system of claim 8 , further comprising:
a second blocking diode directly connected to a second sensing node of the composite switching device, the second sensing node coupled between the second high voltage power switch and the second low voltage nonlinear element;
a second resistor connected in series with the second blocking diode, the second resistor connected to a desaturation detection input of a second gate driver circuit; and
a second blanking capacitor connected between the desaturation detection input of the second gate driver circuit and a common voltage reference of the second gate driver circuit.
10 . A method for overcurrent protection, comprising:
sensing a voltage on a blanking capacitor, the voltage provided from a sensing node of a composite switching device via a blocking diode and a resistor, the sensing node coupled between a high voltage power switch and a low voltage nonlinear element of the composite switching device; and
detecting a short circuit condition based upon the sensed voltage on the blanking capacitor.
11 . The method of claim 10 , wherein detection time of the short circuit condition is based upon size of the blanking capacitor.
12 . The method of claim 10 , wherein the voltage is sensed by a gate driver circuit.
13 . The method of claim 12 , wherein the blanking capacitor is connected between a desaturation detection input of the gate driver circuit and a common voltage reference of the gate driver circuit, wherein the gate driver circuit detects the short circuit condition based upon the sensed voltage at the desaturation detection input.
14 . The method of claim 12 , wherein gating of the high voltage power switch is controlled based upon detection of the short circuit condition.
15 . The method of claim 14 , wherein the common voltage reference of the gate driver circuit is connected to a source of the composite switching device.
16 . The method of claim 15 , wherein the low voltage nonlinear element is connected between the high voltage power switch and the source of the composite switching device.
17 . The method of claim 10 , wherein the high voltage power switch is a Silicon MOSFET, Silicon IGBT, Silicon Carbide MOSFET or Gallium Nitride HEMT device.
18 . The method of claim 10 , wherein the composite switching device is a bidirectional composite switching device.
19 . The method of claim 18 , wherein the bidirectional composite switching device comprises a second high voltage power switch and a second low voltage nonlinear element.
20 . The method of claim 19 , further comprising:
sensing a voltage on a second blanking capacitor, the voltage provided from a second sensing node of the bidirectional composite switching device via a second blocking diode and a second resistor, the second sensing node coupled between the second high voltage power switch and the second low voltage nonlinear element; and
detecting a short circuit condition based upon the sensed voltage on the second blanking capacitor.