Variable resistance power switch feedback
A vehicle powertrain has a power inverter that includes a load switch with a main emitter and a current mirror emitter, a variable resistor coupled between the current mirror emitter and the main emitter, and a controller. The controller may be configured to adjust a gate voltage based on a voltage across the variable resistor, and responsive to the gate voltage exceeding a Miller plateau gate voltage, increase a variable resistor resistance such that feedback increases as the load switch saturates.
1. A vehicle powertrain comprising:
a power inverter including
a load switch with main and current mirror emitters, and
a variable resistor coupled between the main and current mirror emitters; and
a controller configured to
adjust a gate voltage based on a voltage across the variable resistor, and
responsive to the gate voltage exceeding a Miller plateau gate voltage, increase a resistance of the variable resistor such that a feedback voltage increases as the load switch saturates.
2. The vehicle powertrain of claim 1 , wherein the variable resistor includes a first resistor coupled in parallel with a second resistor that is selectable via a solid-state switch, wherein a resistance of the first resistor is greater than the second resistor.
3. The vehicle powertrain of claim 1 , wherein the variable resistor is a solid-state variable resistor coupled in parallel with a sense resistor.
4. The vehicle powertrain of claim 3 , wherein the controller is further configured to select a resistance of the solid-state variable resistor based on an ambient temperature.
5. The vehicle powertrain of claim 3 , wherein the controller is further configured to select a resistance of the solid-state variable resistor based on a temperature of the load switch.
6. The vehicle powertrain of claim 1 , wherein the load switch is an Insulated Gate :Bipolar Junction Transistors (IGBTs).
7. A vehicle powertrain comprising:
a load switch monolithically integrated with a mirror switch;
a variable resistor coupled between a mirror switch emitter and a reference point; and
a controller configured to
adjust a gate voltage based on a voltage across the variable resistor, and
responsive to the gate voltage exceeding a Miller plateau gate voltage, increase a resistance of the variable resistor such that a feedback voltage increases as the load switch saturates.
8. The vehicle powertrain of claim 7 , Wherein the reference point is a main emitter and the load switch and the mirror switch are insulated Gate Bipolar Junction Transistors (IGBTs).
9. The vehicle powertrain of claim 7 , wherein the variable resistor includes a first resistor coupled in parallel with a second resistor that is selectable via a solid-state switch, wherein a resistance of the first resistor is greater than the second resistor.
10. The vehicle powertrain of claim 7 , wherein the load switch is configured to flow current into an inductor of a variable voltage converter.
11. The vehicle powertrain of claim 7 , wherein the load switch is in a power inverter and configured to flow current into a phase winding of an electric machine.
12. The vehicle powertrain of claim 7 , wherein the variable resistor is a solid-state variable resistor coupled in parallel with a sense resistor.
13. The vehicle powertrain of claim 12 , wherein the controller is further configured to select a resistance of the solid-state variable resistor based on an ambient temperature.
14. The vehicle powertrain of claim 12 wherein the controller is further configured to select a resistance of the solid-state variable resistor based on a temperature of the load switch.
15. A method of controlling a power switch in a vehicle powertrain comprising:
setting a resistance of a variable resistor, coupled between a current mirror emitter and reference point, to a first value while a gate voltage of the power switch is below a turn-on threshold;
applying a charge to the gate to increase the gate voltage; and
responsive to the gate voltage exceeding a Miller plateau gate voltage, increasing the resistance of the variable resistor.
16. The method of claim 15 , wherein the variable resistor includes a first resistor coupled in parallel with a second resistor that is selectable via a solid-state switch, and changing the resistance of the variable resistor is disconnecting the second resistor.
17. The method of claim 15 , wherein the resistance is set based on a temperature of the power switch.
18. The method of claim 15 , wherein the resistance is set based on a power demand of the vehicle powertrain.