Electrified vehicle with active discharge of high-voltage bus
An electrified vehicle includes an active discharge system having a plurality of resistors connected in parallel, a switch connected in series with the plurality of resistors with the switch and the plurality of resistors connected across positive and negative legs of a high-voltage DC bus, and a controller coupled to the switch and programmed to close the switch in response to a vehicle shutdown signal, and in response to voltage of the DC bus exceeding a first threshold after a predetermined elapsed time from closing the switch, open the switch. The controller may also open the switch when the voltage of the DC bus is below a second threshold.
1 . An electrified vehicle comprising:
a plurality of resistors connected in parallel;
a switch connected in series with the plurality of resistors, the switch and the plurality of resistors connected across positive and negative legs of a high-voltage DC bus; and
a controller coupled to the switch and programmed to:
close the switch in response to a shutdown signal; and
in response to voltage of the DC bus exceeding a first threshold after a predetermined elapsed time from closing the switch, open the switch.
2 . The electrified vehicle of claim 1 wherein the switch comprises a normally-closed switch that opens in response to a signal from the controller and closes in response to no signal from the controller.
3 . The electrified vehicle of claim 2 wherein the controller is further programmed to open the switch in response to the voltage of the DC bus being below a second threshold, the second threshold lower than the first threshold.
4 . The electrified vehicle of claim 3 wherein the second threshold corresponds to 60 VDC.
5 . The electrified vehicle of claim 3 wherein the controller is further programmed to open the switch in response to the voltage of the DC bus being below the second threshold after a predetermined elapsed time from closing the switch.
6 . The electrified vehicle of claim 1 further comprising:
a DC bus capacitor connected across the positive and negative legs of the DC bus.
7 . The electrified vehicle of claim 6 wherein the plurality of resistors and the switch are connected in parallel with the DC bus capacitor.
8 . The electrified vehicle of claim 1 further comprising:
a traction battery;
a voltage converter connected to the traction battery;
an inverter connected to the voltage converter;
a DC bus capacitor connected across the plurality of resistors and the switch; and
an electric machine connected to the inverter, wherein the plurality of resistors and the switch are connected to the DC bus between the traction battery and the inverter.
9 . A method for controlling an electrified vehicle, comprising, by a vehicle controller:
connecting a plurality of resistors connected in parallel across positive and negative legs of a high voltage DC bus in response to receiving a vehicle shutdown request; and
disconnecting the plurality of resistors from across the positive and negative legs in response to voltage of the DC bus exceeding a first threshold after a predetermined elapsed time from receiving the vehicle shutdown request.
10 . The method of claim 9 wherein connecting the plurality of resistors comprises controlling a switch connected in series with the plurality of resistors.
11 . The method of claim 10 wherein controlling the switch comprises applying a control signal to close the switch.
12 . The method of claim 10 wherein disconnecting the plurality of resistors comprises applying a control signal to open the switch.
13 . The method of claim 9 further comprising disconnecting the plurality of resistors when the voltage of the DC bus is below a second threshold.
14 . The method of claim 13 wherein the second threshold is 60 VDC.
15 . A system comprising:
a traction battery connected to a DC bus;
a DC bus capacitor connected across positive and negative legs of the DC bus;
a plurality of resistors connected in parallel to one another, the plurality of resistors connected in series with a switch, the plurality of resistors and the switch connected across the DC bus capacitor; and
a controller configured to control the switch to discharge voltage of the DC bus capacitor through the plurality of resistors for a predetermined time responsive to voltage of the DC bus being greater than a first threshold, and to stop discharging voltage of the DC bus responsive to the voltage of the DC bus being less than a second threshold lower than the first threshold.
16 . The system of claim 15 wherein the second threshold is 60 VDC.
17 . The system of claim 15 further comprising:
a voltage converter connected to the traction battery;
an inverter connected to the voltage converter; and
an electric machine connected to the inverter, wherein the plurality of resistors and the switch are connected to the DC bus between the traction battery and the inverter.
18 . The system of claim 17 wherein the switch comprises a normally closed switch.
19 . The system of claim 15 wherein the controller is configured to control the switch to discharge the voltage of the DC bus in response to receiving a vehicle shutdown signal.
20 . The system of claim 19 wherein the controller is configured to generate a signal to open the switch until receiving the vehicle shutdown signal.