Gate driver with temperature compensated turn-off
A vehicle powertrain includes a monolithically integrated load switch, mirror switch, and temperature array, and a gate driver. The gate driver includes a first comparator configured to filter a current level of the mirror switch, and a second comparator configured to provide a reference to the first comparator based on temperature array output such that a gate discharge rate of the switch, enabled by the first comparator, varies proportionally with a temperature adjusted filtered current level.
1. A vehicle powertrain comprising:
a monolithically integrated load switch, mirror switch, and temperature array;
an off-resistor connected to the load switch;
a fast turn-off structure configured to connect in parallel with the off-resistor to provide a fast gate discharge path; and
a gate driver including
a first comparator coupled to the fast turn-off structure and configured to filter a current level of the mirror switch, and
a second comparator configured to provide a reference to the first comparator based on temperature array output such that a gate discharge rate of the load switch, enabled by the first comparator and at least one of the off-resistor and the fast turn-off structure, varies proportionally with a temperature adjusted filtered current level.
2. The vehicle powertrain of claim 1 , wherein the load switch and the mirror switch are Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) or Insulated Gate Bipolar Junction Transistors (IGBTs).
3. The vehicle powertrain of claim 1 , wherein the rate of discharge is proportional to a change in the filtered current level.
4. The vehicle powertrain of claim 1 wherein the load switch is in a DC-AC converter and configured to flow a current in an electric machine proportional to the current level of the mirror switch, and the filter is over a window that is greater than a predetermined shut-off time.
5. The vehicle powertrain of claim 1 , wherein the load switch is in a DC-DC converter and configured to flow a current in a boost inductor configured to increase a battery voltage to drive an electric machine, and the filter is over a window that is greater than a predetermined shut-off time.
6. A method of controlling a switch comprising:
filtering a mirror current indicative of a current flow through the switch;
varying a reference voltage proportionally with a junction temperature of the switch; and
varying a discharge rate of a gate of the switch based on an open loop comparison of the filtered mirror current with the varied reference voltage such that the discharge rate decreases upon reaching a breakdown threshold of the switch.
7. The method of claim 6 , wherein the switch is a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) or an Insulated Gate Bipolar Junction Transistor (IGBT).
8. The method of claim 6 , wherein the breakdown threshold is associated with a breakdown voltage of the switch.
9. The method of claim 6 , wherein the discharge rate is varied proportionally to a change in the filtered mirror current.
10. The vehicle powertrain of claim 1 , further comprising:
a control switch connected between the first comparator and the fast turn-off structure and configured to enable the fast gate discharge path in response to the temperature adjusted filtered current level being less than a threshold value.
11. The vehicle powertrain of claim 10 , wherein the fast turn-off structure further comprises a series switch and a fast turn-off resistor.
12. The vehicle powertrain of claim 11 , wherein closing the series switch adds resistance from the fast turn-off resistor in parallel with the off-resistor thereby increasing the gate discharge rate, and opening the series switch removes the resistance from the fast turn-off resistor thereby decreasing the gate discharge rate.
13. The vehicle powertrain of claim 12 wherein the output of the first comparator is inversely proportional to a difference between an output of the temperature array an output of the second comparator.
14. The vehicle powertrain of claim 12 further comprising at least one of a resistor and a capacitor connected between the load switch and the first comparator for filtering the current signal of the mirror switch.
15. A vehicle powertrain comprising:
a gate drive circuit having an on-resistor and an off-resistor;
an insulated-gate bipolar transistor (IGBT), including signal gate, a mirror output, and a temperature array;
a turn-off structure having a fast turn-off resistor and a series switch, wherein closing the series switch adds resistance from the fast turn-off resistor to the gate drive circuit, parallel to the off-resistor thereby increasing a discharge rate of the signal gate, and wherein opening the series switch removes resistance from the fast turn-off resistor from the gate drive circuit thereby decreasing a discharge rate of the signal gate;
a second comparator capable of receiving a temperature voltage from the temperature array; and
a first comparator capable of receiving a temperature compensated voltage signal from the second comparator and receiving a filtered current level from the mirror output; and
a control switch configured to close or open the series switch based on the output of the first comparator.
16. The vehicle powertrain of claim 15 wherein the IGBT is in a DC-AC converter and configured to flow a current in an electric machine proportional to the current level of the IGBT, and the filter is over a window that is greater than a predetermined shut-off time.
17. The vehicle powertrain of claim 15 wherein the output of the first comparator is inversely proportional to a difference between the output of the temperature array and the output of the second comparator.
18. The vehicle powertrain of claim 15 further comprising a resistor/capacitor filter disposed between the IGBT and the first comparator for filtering the current signal of the mirror output.