Gate driver circuit fault detection techniques
A desaturation detection circuit is described that uses two or more desaturation circuit threshold values, which shifts the desaturation threshold value in a normal operational mode to a higher voltage when the active short circuit (ASC) signal is present in a faulted operational mode. Including two or more desaturation detection circuit threshold values allows a lower desaturation threshold value during a normal operational mode and a higher voltage in a faulted operational mode, or mode-dependent threshold value selection.
1 . A gate driver circuit for driving a transistor, the gate driver circuit comprising:
a source of a current coupled with a terminal of the transistor; and
an overcurrent detection circuit including:
a switch configured for selecting, based on an operational mode, a threshold value from a plurality of threshold values; and
a comparator configured for:
receiving a voltage representing an ON voltage across the transistor;
comparing the voltage to the threshold value; and
generating an output signal when the voltage exceeds the threshold value,
wherein the output signal represents an overcurrent condition of the transistor,
wherein the plurality of threshold values includes a first threshold value and a second threshold value, and wherein the switch is configured for selecting the first threshold value during a normal operational mode and the second threshold value, higher than the first threshold value, during a faulted operational mode.
2 . The gate driver circuit of claim 1 , wherein the switch is a multiplexer.
3 . The gate driver circuit of claim 1 , wherein the faulted operational mode is an active short circuit mode.
4 . The gate driver circuit of claim 1 , wherein the overcurrent detection circuit comprises:
a timer configured for controlling a duration for which the second threshold value is applied during the faulted operational mode.
5 . The gate driver circuit of claim 1 , wherein the overcurrent detection circuit comprises:
a timer configured for controlling a duration before which the second threshold value is applied during the faulted operational mode.
6 . The gate driver circuit of claim 1 , wherein the overcurrent detection circuit comprises:
a timer configured for controlling a duration for which the second threshold value remains ON after the faulted operational mode is disabled.
7 . The gate driver circuit of claim 1 , wherein the gate driver circuit is coupled with a control terminal of the transistor, and wherein the transistor forms part of a bridge circuit.
8 . A method for dynamically adjusting a desaturation detection threshold in a gate driver circuit, the method comprising:
sourcing a current to a terminal of a transistor;
selecting, based on an operational mode, a threshold value from a plurality of threshold values;
receiving a voltage representing an ON voltage across the transistor;
comparing the voltage to a threshold value, wherein the threshold value is selected from a plurality of threshold values; and
generating an output signal when the voltage exceeds the threshold value, wherein the output signal represents a desaturation event of the transistor,
wherein the plurality of threshold values includes a first threshold value and a second threshold value, and wherein the selecting includes selecting the first threshold value during a normal operational mode and selecting the second threshold value, higher than the first threshold value, during a faulted operational mode.
9 . The method of claim 8 , wherein the faulted operational mode is an active short circuit mode.
10 . The method of claim 8 , comprising:
controlling a duration for which the second threshold value is applied during the faulted operational mode.
11 . The method of claim 8 , comprising:
controlling a duration before which the second threshold value is applied during the faulted operational mode.
12 . The method of claim 8 , comprising:
controlling a duration during which the second threshold value remains ON after the faulted operational mode is disabled.
13 . A desaturation detection circuit comprising:
a switch configured for selecting, based on an operational mode, a threshold value from a plurality of threshold values; and
a comparator configured for:
receiving a voltage representing an ON voltage across a transistor;
comparing the voltage to a threshold value, wherein the threshold value is selected from a plurality of threshold values; and
generating an output signal when the voltage exceeds the threshold value, wherein the output signal represents an overcurrent condition of the transistor,
wherein the plurality of threshold values includes a first threshold value and a second threshold value, and wherein the switch is configured for selecting the first threshold value during a normal operational mode and the second threshold value, higher than the first threshold value, during a faulted operational mode.
14 . The desaturation detection circuit of claim 13 , wherein the faulted operational mode is an active short circuit mode.
15 . The desaturation detection circuit of claim 13 , comprising:
a timer for controlling one of the following:
a duration for which the second threshold value is applied during the faulted operational mode;
a duration before which the second threshold value is applied during the faulted operational mode; or
a duration for which the second threshold value remains ON after the faulted operational mode is disabled.