Short circuit protection circuit for semiconductor switching element
In a short circuit protection circuit, a first gate resistor is connected between a first output node of a gate driver and a first gate terminal. A first real-time control circuit operates to decrease a potential of the first gate terminal when the first real-time control circuit detects that a short circuit current passes through a first semiconductor switching element. The operation monitoring circuit includes a differential voltage circuit configured to output a potential difference between a potential proportional to a potential difference across the first gate resistor and the potential of a first power supply. The operation monitoring circuit monitors, based on an output of the differential voltage circuit, whether the first real-time control circuit is in operation.
1. A short circuit protection circuit for a semiconductor switching element, the short circuit protection circuit protecting a first semiconductor switching element, the first semiconductor switching element having a first gate terminal and turned on by receiving a potential of a first power supply at the first gate terminal from a first output node of a gate driver, the short circuit protection circuit comprising:
a first gate resistor connected between the first output node of the gate driver and the first gate terminal;
a first real-time control circuit that operates to decrease a potential of the first gate terminal when the first real-time control circuit detects that a short circuit current passes through the first semiconductor switching element; and
an operation monitoring circuit, the operation monitoring circuit including a differential voltage circuit configured to output a potential difference between a potential proportional to a potential difference across the first gate resistor and the potential of the first power supply, and monitoring, based on an output of the differential voltage circuit, whether the first real-time control circuit is in operation.
2. The short circuit protection circuit for a semiconductor switching element according to claim 1 , the short circuit protection circuit protecting a second semiconductor switching element, the second semiconductor switching element having a second gate terminal and turned on by receiving the potential of the first power supply at the second gate terminal from the first output node of the gate driver, the short circuit protection circuit further comprising:
a second gate resistor connected between the first output node of the gate driver and the second gate terminal; and
a second real-time control circuit that operates to decrease a potential of the second gate terminal when the second real-time control circuit detects that a short circuit current passes through the second semiconductor switching element,
wherein the differential voltage circuit is further configured to output a potential difference between a potential proportional to a potential difference across the second gate resistor and the potential of the first power supply.
3. The short circuit protection circuit for a semiconductor switching element according to claim 2 , further comprising:
a first diode connected to the first gate terminal such that the first gate terminal is located on a side of a cathode thereof;
a second diode connected to the second gate terminal such that the second gate terminal is located on a side of a cathode thereof; and
a connection node to which an anode of the first diode and an anode of the second diode are connected in common,
wherein the differential voltage circuit is configured to output a voltage proportional to a potential difference between the first output node of the gate driver and the connection node, as a potential difference from the first power supply.
4. The short circuit protection circuit for a semiconductor switching element according to claim 3 , wherein
the differential voltage circuit includes:
a first differential amplifier having a positive input terminal connected to the first output node of the gate driver, a negative input terminal connected to the connection node, and an output terminal outputting a potential difference of a potential of the positive input terminal minus a potential of the negative input terminal; and
a second differential amplifier having a positive input terminal connected to the first power supply, a negative input terminal connected to the output terminal of the first differential amplifier, and an output terminal outputting a potential difference of a potential of the positive input terminal minus a potential of the negative input terminal and multiplied by a constant, and
the operation monitoring circuit monitors, based on a potential of the output terminal of the second differential amplifier, whether the first real-time control circuit is in operation.
5. The short circuit protection circuit for a semiconductor switching element according to claim 4 , wherein
the operation monitoring circuit further includes a PNP transistor having a base terminal connected to the output terminal of the second differential amplifier and an emitter terminal connected to the first power supply, and
a signal representing whether the first and second real-time control circuits are in operation is output from a collector terminal of the PNP transistor.
6. The short circuit protection circuit for a semiconductor switching element according to claim 3 , wherein
the differential voltage circuit includes a first differential amplifier having a negative input terminal connected to the first output node of the gate driver, a positive input terminal connected to the connection node, a reference terminal connected to the first power supply, and an output terminal outputting a potential difference of a potential of the positive input terminal minus a potential of the negative input terminal multiplied by a constant plus a potential of the reference terminal, and
the operation monitoring circuit monitors, based on a potential of the output terminal of the first differential amplifier, whether the first real-time control circuit is in operation.
7. The short circuit protection circuit for a semiconductor switching element according to claim 6 , wherein
the operation monitoring circuit further includes a PNP transistor having a base terminal connected to the output terminal of the first differential amplifier and an emitter terminal connected to the first power supply, and
a signal representing whether the first and second real-time control circuits are in operation is output from a collector terminal of the PNP transistor.
8. The short circuit protection circuit for a semiconductor switching element according to claim 2 , further comprising:
a third gate resistor connected parallel to the first gate resistor and connected between the first output node of the gate driver and the first gate terminal;
a fourth gate resistor connected parallel to the second gate resistor and connected between the first output node of the gate driver and the second gate terminal;
a third diode connected in series with the first gate resistor and connected between the first output node of the gate driver and the first gate terminal such that the first gate terminal is located on a side of a cathode thereof;
a fourth diode connected in series with the third gate resistor and connected between the first output node of the gate driver and the first gate terminal such that the first gate terminal is located on a side of an anode thereof,
a fifth diode connected in series with the second gate resistor and connected between the first output node of the gate driver and the second gate terminal such that the second gate terminal is located on a side of a cathode thereof; and
a sixth diode connected in series with the fourth gate resistor and connected between the first output node of the gate driver and the second gate terminal such that the second gate terminal is located on a side of an anode thereof.
9. The short circuit protection circuit for a semiconductor switching element according to claim 2 , wherein
the gate driver includes:
the first output node;
a first transistor connected between the first output node and the first power supply;
a second output node different from the first output node; and
a second transistor connected between the second output node and a second power supply, and
the short circuit protection circuit further comprises:
a fifth gate resistor connected in series with the second transistor and connected between the second output node and the second power supply;
a seventh diode connected between the first gate terminal and the second output node such that the first gate terminal is located on a side of an anode thereof, and
an eighth diode connected between the second gate terminal and the second output node such that the second gate terminal is located on a side of an anode thereof.
10. The short circuit protection circuit for a semiconductor switching element according to claim 9 , further comprising a sixth gate resistor connected in series with the first transistor and connected between the first output node and the first power supply.