Abstract: A control circuit of a power supply is provided. The control circuit includes a circuit and a PWM circuit. The circuit generates a limit signal in response to an output voltage of the power supply for limiting a switching current of a transformer of the power supply. The PWM circuit generates a switching signal in response to a feedback signal and the limit signal for switching the transformer and regulating the output voltage of the power supply. A level of the feedback signal is related to a level of the output voltage of the power supply. The output voltage of the power supply is programmable.

Abstract: A discharge circuit for an electromagnetic interference (EMI) filter is provided. The discharge circuit includes a switch circuit, a control circuit, and a detection circuit. The switch circuit is coupled to an X-capacitor of the EMI filter. The control circuit is coupled to the switch circuit and configured to turn on the switch circuit in a predetermined period to provide a discharge path. The detection circuit is coupled to the discharge path. In the predetermined period, the detection circuit detects whether a cross point occurs between a discharge voltage signal on the discharge path and a reference voltage signal to generate a detection signal which is provided to the control circuit. When the detection circuit detects that the cross point does not occur, the control circuit continuously turns on the switch circuit according to the detection signal after the predetermined period has elapsed.

Abstract: A discharge circuit for an electromagnetic interference (EMI) filter is provided. The discharge circuit includes a switch circuit, a control circuit, and a detection circuit. The switch circuit is coupled to an X-capacitor of the EMI filter. The control circuit is coupled to the switch circuit and configured to turn on the switch circuit in a predetermined period to provide a discharge path. The detection circuit is coupled to the discharge path. In the predetermined period, the detection circuit detects whether a cross point occurs between a discharge voltage signal on the discharge path and a reference voltage signal to generate a detection signal which is provided to the control circuit. When the detection circuit detects that the cross point does not occur, the control circuit continuously turns on the switch circuit according to the detection signal after the predetermined period has elapsed.

Abstract: A control circuit of a power supply is provided. The control circuit includes a circuit and a PWM circuit. The circuit generates a limit signal in response to an output voltage of the power supply for limiting a switching current of a transformer of the power supply. The PWM circuit generates a switching signal in response to a feedback signal and the limit signal for switching the transformer and regulating the output voltage of the power supply. A level of the feedback signal is related to a level of the output voltage of the power supply. The output voltage of the power supply is programmable.