Apparatus for discharging a high-voltage bus

A device electrically connected to a high-voltage DC power source via a high-voltage bus including a capacitor electrically connected between positive and negative conductors of the high-voltage bus, comprising:

• a discharge switch electrically connected in series with a discharge resistor between the positive and negative conductors of the high-voltage bus, the discharge switch including a control gate;
• a composite trigger gate having a plurality of input lines and an output line in communication with the control gate of the discharge switch;
• and
• a transformer having a primary circuit and a secondary circuit, wherein the secondary circuit is in communication with one of the input lines of the composite trigger gate and the primary circuit is electrically connected between a low-voltage power supply and a ground;
• wherein the discharge switch is controllable 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 to one of the input lines of the composite trigger gate that is communicated to the gate of the discharge switch.

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 capacitor electrically connected between the positive and negative conductors of the high-voltage bus;
• and
• a passive discharge circuit disposed between the positive and negative conductors of the high-voltage bus, including a discharge switch electrically connected in series with a discharge resistor between the positive and negative conductors of the high-voltage bus, the discharge switch including a control gate, wherein the control gate of the discharge switch is in communication with an ignition switch;
• wherein the discharge switch achieves 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 when the ignition switch is in a key-OFF state.