Active discharge circuit for link capacitor using phase leg switches

A method of rapid discharge of a DC link capacitor in drive system for an electric vehicle, wherein the drive system includes positive and negative DC busses coupled to a DC power source by contactor switches, and wherein the link capacitor and a plurality of inverter phase legs are connected to the busses, the method comprising:

• detecting a discharge event wherein the busses are decoupled from the power source by the contactor switches;
• driving upper and lower switching devices in at least one phase leg with gate signals that simultaneously activate the upper and lower switching devices to transitional states, wherein the gate signals are configured to discharge the link capacitor within a predetermined time while limiting a current through the switching devices that maintains a temperature of the switching devices below a predetermined temperature, and wherein the gate signals are comprised of synchronous pulse trains having a gate voltage corresponding to the ON state and a duration that is too short to obtain an ON state of the switching devices.

A capacitor discharge system, comprising:

• a phase leg of an inverter comprising upper and lower switching devices configured to invert a DC voltage from a link capacitor to an AC voltage for driving a motor;
• and
• a gate driver simultaneously activating the upper and lower switching devices to transitional states to discharge the link capacitor within a predetermined time during a discharge event while maintaining the switching devices below a predetermined temperature, wherein the transitional states are comprised of simultaneously switching the upper and lower switching devices according to synchronous pulse trains having a gate voltage corresponding to the ON state and a duration that is too short to obtain an ON state of the switching devices.