A controlling circuit includes a pulse width modulation (PWM) circuit, a level shifter having a current source therein, a capacitor connected to a current source, an overcurrent protection circuit connected to the level shifter, and a controlling circuit configured to enable or disable a function of overcurrent protection of the overcurrent protection circuit within designated time. The controlling circuit includes a switch device. An input of the switch device connected to an output terminal of the capacitor, and an output terminal of the switch device connected to a controlling terminal of the overcurrent protection circuit.