Circuit for actively performing short-circuit and motor controller

A motor controller, comprising:

• a low-voltage power supply, a driving power supply, a control circuit, a bridge arm driving circuit, a direct current side capacitor, a bridge arm and a circuit for actively performing short-circuit, wherein
• the circuit for actively performing short-circuit comprises:
• an undervoltage detecting circuit, wherein the undervoltage detecting circuit is connected to the driving power supply, and is configured to detect a driving power supply signal outputted from the driving power supply and output, in a case that an amplitude of the driving power supply signal is lower than a first threshold, an emergency active short-circuit enable signal;
• an emergency power supply and an gate level selecting switch which are connected to the undervoltage detecting circuit, wherein in response to the emergency active short-circuit enable signal, the emergency power supply is enabled and the gate level selecting switch is controlled to switch from a first conduction path to a second conduction path, to transmit an emergency power supply signal outputted from the emergency power supply to a bridge arm via the second conduction path, and wherein the first conduction path is a path between the bridge arm and the bridge arm driving circuit, and the second conduction path is a path between the bridge arm and the emergency power supply;
• and
• a reverse-flow preventing circuit, wherein the reverse-flow preventing circuit is arranged between the driving power supply and the emergency power supply, and is configured to insulate the driving power supply signal from the emergency power supply signal in a case that the emergency power supply is enabled, and wherein
• the low-voltage power supply is connected to both the driving power supply and the control circuit, and is configured to supply power to the control circuit;
• the bridge arm driving circuit is connected to both the driving power supply and the control circuit, and is configured to output, in a case that an amplitude of the driving power supply signal outputted from the driving power supply is higher than a first threshold, a bridge arm driving signal in response to a bridge arm driving control signal outputted from the control circuit, wherein the bridge arm driving signal is transmitted to the bridge arm via the first conduction path;
• and
• the circuit for actively performing short-circuit is configured to transmit, in a case that the amplitude of the driving power supply signal outputted from the driving power supply is lower than the first threshold, an emergency power supply signal outputted from the emergency power supply to the bridge arm via the second conduction path.