Apparatus for discharging a high-voltage bus

A power inverter disposed to control an electric machine, the power inverter being electrically connected to a high-voltage DC power source via a high-voltage bus, the power inverter comprising:

• a multi-phase inverter circuit electrically connected to positive and negative conductors of the high-voltage bus;
• a bulk capacitor electrically connected between the positive and negative conductors of the high-voltage bus;
• and
• a discharge circuit for the high-voltage bus, including:
• first and second contactors being controllable to electrically connect a respective one of the positive and negative conductors of the high-voltage bus to the high-voltage DC power source,
• first and second trigger circuits in communication with a respective one of the first and second contactors,
• a capacitive divider electrically connected between the positive and negative conductors, and including a first capacitor electrically connected in series with a second capacitor at a first node,
• a discharge resistor electrically connected in series with a discharge switch between the positive and negative conductors,
• a bi-stable switch electrically connected between the first node and a gate of the discharge switch, and
• the first and second trigger circuits being in communication with a gate of the bi-stable switch,
• wherein the first and second trigger circuits communicate with the gate of the bi-stable switch to control the discharge switch to an open state when the ignition switch is in a key-ON state, and
• wherein the bi-stable switch controls the discharge switch to a closed state to provide a low-impedance electric current flow path through the discharge resistor between the positive and negative conductors of the high-voltage bus in response to an activation signal that is communicated to the bi-stable switch.

A method for discharging electric power stored on a high-voltage bus, the method comprising:

• activating a bi-stable switch in response to a trigger signal,
• wherein the bi-stable switch includes an input line that is electrically connected to the high-voltage bus;
• wherein the bi-stable switch includes an output line that is electrically connected to a gate of a discharge switch;
• and
• wherein the discharge switch is electrically connected in series with a discharge resistor between positive and negative conductors of the high-voltage bus.