PRE-CHARGING CIRCUIT AND PRE-CHARGING METHOD

1 . A pre-charging circuit, comprising: a controller, a pulse width modulation (PWM) control unit, and a drive unit, wherein the controller and the PWM control unit are electrically connected to the drive unit, and the drive unit is electrically connected to a main switch of a battery management system circuit;

the PWM control unit is configured to detect a current existent in the battery management system circuit when the main switch is turned on;

the PWM control unit is further configured to output a control signal to the drive unit according to the current existent in the battery management system circuit;

the controller is configured to output a preset PWM signal to the drive unit; and

the drive unit is configured to turn the main switch off or on according to the received control signal and PWM signal, so as to pre-charge a load capacitor of the battery management system circuit when the main switch is turned on.

2 . The pre-charging circuit according to claim 1 , wherein the PWM control unit is specifically configured to output a low level control signal to the drive unit when the current is greater than a preset current threshold, and stop output of the low level control signal to the drive unit when the current is less than or equal to the preset current threshold; and

the drive unit is specifically configured to turn the main switch off when the low level control signal and the PWM signal are received, and turn the main switch on when the low level control signal is not received and the PWM signal is at a high level to pre-charge the load capacitor of the battery management system circuit.

3 . The pre-charging circuit according to claim 1 , wherein the PWM control unit comprises a sampling unit, a PWM output unit, and a semiconductor switch that are connected in sequence, and the semiconductor switch is connected to the drive unit;

the sampling unit is configured to detect the current existent in the battery management system circuit when the main switch is turned on; and

the PWM output unit is configured to output the low level control signal to the drive unit through the semiconductor switch when the current is greater than a preset current threshold, and stop output of the low level control signal to the drive unit through the semiconductor switch when the current is less than or equal to the preset current threshold.

4 . The pre-charging circuit according to claim 1 , wherein the pre-charging circuit further comprises a high-voltage sampling unit electrically connected to the PWM control unit and the controller;

the high-voltage sampling unit is configured to detect a voltage across the load capacitor;

the PWM control unit is further configured to stop output of the control signal to the drive unit when the voltage across the load capacitor reaches a preset voltage threshold; and

the controller is configured to stop output of the PWM signal when the voltage across the load capacitor reaches the preset voltage threshold, and output a high level electrical signal to the drive unit.

5 . The pre-charging circuit according to claim 3 , wherein the sampling unit is specifically configured to collect a voltage across a current divider in the battery management system circuit, and calculate the current according to a resistance value of the current divider and the voltage across the current divider.

6 . The pre-charging circuit according to claim 3 , wherein the PWM output unit is specifically configured to output a high level electrical signal to turn on the semiconductor switch when the current is greater than a preset current threshold, so as to output the low level control signal to the drive unit; and

the PWM output unit is specifically configured to output a low level electrical signal to turn off the semiconductor switch when the current is less than or equal to the preset current threshold, so as to stop output of the low level control signal to the drive unit.

7 . The pre-charging circuit according to claim 1 , wherein the main switch is a semiconductor power switch.

8 . The pre-charging circuit according to claim 7 , wherein the semiconductor power switch is an insulated gate bipolar transistor (IGBT) or a metal oxide semiconductor field effect transistor (MOSFET).

9 . A pre-charging method, applied to a pre-charging circuit, wherein: the pre-charging circuit comprises a controller, a PWM control unit, and a drive unit, the controller and the PWM control unit are connected to the drive unit, and the drive unit is connected to a main switch of a battery management system circuit;

the method comprises:

detecting, by the PWM control unit, a current existent in the battery management system circuit when the main switch is turned on;

outputting, by the PWM control unit, a control signal to the drive unit according to the current;

outputting, by the controller, a preset PWM signal to the drive unit; and

controlling, by the drive unit according to the received control signal and PWM signal, the main switch to turn off or on, so as to pre-charge a load capacitor of the battery management system circuit when the main switch is turned on.

10 . The pre-charging method according to claim 9 , wherein the outputting, by the PWM control unit, a control signal to the drive unit according to the current further includes:

outputting, by the PWM control unit, a low level control signal to the drive unit when the current is greater than a preset current threshold, and stopping output of the low level control signal to the drive unit when the current is less than or equal to the current threshold; and

the controlling, by the drive unit according to the received control signal and PWM signal, the main switch to turn off or on, so as to pre-charge a load capacitor of the battery management system circuit when the main switch is turned on further includes:

turning, by the drive unit, the main switch off when the low level control signal and the PWM signal are received; and

turning, by the drive unit, the main switch on when the low level control signal is not received and the PWM signal is at a high level so as to pre-charge the load capacitor of the battery management system circuit.

11 . The pre-charging method according to claim 9 , wherein the PWM control unit comprises a sampling unit, a PWM output unit, and a semiconductor switch that are connected in sequence, and the semiconductor switch is connected to the drive unit; and

the detecting, by the PWM control unit, a current existent in the battery management system circuit when the main switch is turned on, and outputting, by the PWM control unit, a control signal to the drive unit according to the current further comprises:

detecting, by the sampling unit, the current existent in the battery management system circuit when the main switch is turned on; and

controlling the PWM output unit to output the low level control signal to the drive unit through the semiconductor switch when the current is greater than a preset current threshold; and

controlling the PWM output unit to stop output of the low level control signal to the drive unit through the semiconductor switch when the current is less than or equal to the preset current threshold.

12 . The pre-charging method according to claim 9 , wherein the pre-charging circuit further comprises a high-voltage sampling unit connected to the PWM control unit and the controller; and

the method further comprises:

detecting, by the high-voltage sampling unit, a voltage across the load capacitor;

stopping, by the PWM control unit, output of the control signal to the drive unit when the voltage across the load capacitor reaches a preset voltage threshold; and

stopping, by the controller, output of the PWM signal when the voltage across the load capacitor reaches the preset voltage threshold, and outputting, by the controller, a high level electrical signal to the drive unit.