Short-circuit protection circuits, system, and method
Systems, circuits, and methods for protecting an Insulated-Gate Bipolar Transistor (IGBT) from short-circuit events are provided. A short-circuit protection circuit is described that includes a switch, a resistor, a capacitor, and an optional current buffer that provide a strong pull-down to the IGBT in response to detecting a short-circuit event and then controls a rate at which turn-off current is decreased, thereby minimizing a peak voltage for the IGBT.
1. A circuit, comprising:
at least one Insulated-Gate Bipolar Transistor (IGBT) having a gate, collector, and emitter;
a first driver for the at least one IGBT, the first driver configured to provide a driving current to the gate of the IGBT;
a load connected to the emitter of the at least one IGBT;
a short-circuit protection circuit connected across the gate and the emitter of the at least one IGBT, wherein the short-circuit protection circuit is further connected to the first driver, wherein the short-circuit protection circuit comprises a switch to provide a strong pull-down to the at least one IGBT in response to detection of a short-circuit event in the circuit, and wherein the short-circuit protection circuit further comprises a capacitor and resistor that control a turn-off current provided to the gate of the at least one IGBT; and
a current buffer connected across the switch and the at least one IGBT.
2. The circuit of claim 1 , wherein the resistor and capacitor are connected in parallel with one another and each have a terminal connected to a first terminal of the switch.
3. The circuit of claim 2 , wherein a second terminal of the switch is connected to the first driver and wherein a third terminal of the switch is connected to the emitter of the at least one IGBT.
4. The circuit of claim 3 , wherein the resistor and capacitor also have terminals that connect directly to the gate of the at least one IGBT.
5. The circuit of claim 1 , wherein the current buffer is connected across the gate and emitter of the at least one IGBT.
6. The circuit of claim 1 , wherein the current buffer comprises a first terminal connected to the emitter of the at least one IGBT, a second terminal connected to both a terminal of the resistor and a terminal of the capacitor, and a third terminal connected to the emitter of the at least one IGBT.
7. The circuit of claim 1 , wherein the current buffer comprises a transistor that boosts a turn-off current for the at least one IGBT and reduces a Miller plateau time for the at least one IGBT during the short-circuit event.
8. The circuit of claim 1 , wherein the switch remains on after a peak voltage in the at least one IGBT is reached.
9. The circuit of claim 1 , wherein the switch comprises an NPN transistor.
10. The circuit of claim 1 , wherein the at least one IGBT comprises a first IGBT and a second IGBT configured in a half-bridge circuit configuration and wherein the short-circuit protection circuit is connected to an emitter of the first IGBT and connected to a collector of the second IGBT.
11. The circuit of claim 1 , wherein the switch is turned on in response to the first driver being disconnected from the at least one IGBT.
12. The circuit of claim 1 , wherein the short-circuit event corresponds to a condition where the emitter of the at least one IGBT is shorted to at least one of a common voltage and ground.
13. An Insulated-Gate Bipolar Transistor (IGBT) short-circuit protection circuit configured to protect an IGBT from damage during a short-circuit event, wherein the IGBT is driven by a driver and, in response to signals received from the driver, drives a load, and wherein the IGBT comprises a gate, collector, and emitter, the short-circuit protection circuit comprising:
a switch configured to switch on during the short-circuit event and provide a route for current as an alternative to passing through the IGBT;
a resistor having a first terminal and a second terminal, wherein the first terminal of the resistor receives current from a first circuit node connected to the gate of the IGBT, and wherein the second terminal of the resistor provides the current received from the first circuit node connected to the IGBT to the first terminal of the switch;
a capacitor connected in parallel with the resistor; and
a current buffer that is positioned between the gate of the IGBT and the combination of the resistor and capacitor.
14. The short-circuit protection circuit of claim 13 , wherein the resistor and capacitor control a turn-off current provided to the gate of the IGBT.
15. The short-circuit protection circuit of claim 14 , wherein the switch provides a strong pull-down to the IGBT in response to detection of the short-circuit event.
16. The short-circuit protection circuit of claim 13 , wherein the second terminal of the resistor and the second terminal of the capacitor are both connected directly to the first terminal of the switch.
17. The short-circuit protection circuit of claim 16 , wherein a second terminal of the switch receives a control signal from the driver and, in response to the control signal, closes a conduction path between the resistor, the capacitor, and the emitter of the IGBT.
18. The short-circuit protection circuit of claim 13 , wherein the current buffer comprises a transistor that boosts a turn-off current for the IGBT and reduces a Miller plateau time for the IGBT during the short-circuit event.
19. A method of operating a short-circuit protection circuit, the method comprising:
detecting an occurrence of a short-circuit event in a circuit comprising a driver, a short-circuit detection circuit, and an Insulated-Gate Bipolar Transistor (IGBT) having a gate, collector, and emitter;
in response to detecting the occurrence of the short-circuit event, disconnecting the driver from the IGBT;
also in response to detecting the occurrence of the short-circuit event, activating a switch in the short-circuit protection circuit to provide a strong current pull-down to the IGBT, wherein the strong current pull-down causes a Miller current to flow through the IGBT for an amount of time until an internal capacitance of the IGBT is fully charged and then causes a gate-to-emitter voltage of the IGBT to decrease at a predetermined rate;
controlling the rate at which the gate-to-emitter voltage of the IGBT decreases with a resistor and capacitor connected between the gate of the IGBT and the switch such that an amount of time between when the Miller current is no longer flowing through the IGBT and the IGBT is fully turned-off is extended thereby decreasing a peak voltage provided to the IGBT; and
utilizing a current buffer to boost a turn-off current of the IGBT.
20. The method of claim 19 , wherein utilizing the current buffer to boost a turn-off current of the IGBT reduces an amount of time that the Miller current is provided to the IGBT.