Discharge circuit, battery management system, battery, protection method, and electrical apparatus

A battery management system, comprising:

• a discharge circuit comprising:
• a first branch configured to be connected to a protected unit, and comprising a first overvoltage protection device configured to passively discharge a surge voltage;
• and
• a second branch connected in parallel to the first branch and comprising a second overvoltage protection device and a control switch connected in series, the control switch being configured to be connected to a control unit, and to be opened or closed based on a control signal of the control unit;
• a microcontroller;
• a voltage sampling unit;
• and
• a multi-stage voltage comparison unit;
• wherein:
• at least one of the microcontroller, the voltage sampling unit, or the multi-stage voltage comparison unit is connected to the control switch of the second branch of the discharge circuit, and the control switch receives a control signal from the at least one of the microcontroller, the voltage sampling unit, or the multi-stage voltage comparison unit, and is opened or closed based on the control signal;
• the first branch comprises N sub-branches, N being a positive integer greater than or equal to 2;
• the first overvoltage protection device is one of N first overvoltage protection devices each connected in series to one of the sub-branches;
• the N first overvoltage protection devices are connected in parallel;
• each of the sub-branches further comprises a resistor connected in series to the corresponding first overvoltage protection device;
• and
• when the first branch is connected to the protected unit, the resistor is located on a side closer to the protected unit than the corresponding first overvoltage protection device.

A discharge circuit, comprising:

• a first branch configured to be connected to a protected unit, and comprising a first overvoltage protection device configured to passively discharge a surge voltage;
• and
• a second branch comprising a second overvoltage protection device and a control switch connected in series, the second branch being connected in parallel to the first branch;
• wherein:
• the control switch is configured to be connected to a control unit, and to be opened or closed based on a control signal of the control unit;
• the second branch comprises M sub-branches connected in parallel, M being a positive integer greater than or equal to 2;
• the second overvoltage protection device is one of M second overvoltage protection devices each belonging to one of the sub-branches;
• the control switch is one of M control switches each belonging to one of the sub-branches and connected in series to the corresponding second overvoltage protection device;
• and
• all of the control switches are configured to be connected to the control unit.