Abstract: A method and a circuit for detecting a light load mode of a switching power supply system are provided. The switching power supply system has a first winding, a second winding, a third winding having a voltage being in proportion to an output voltage of the second winding, and a signal converting device electrically connected to the third winding. The method includes steps of measuring a voltage of the signal converting device, and determining the switching power supply system being under the light load mode when the voltage of the signal converting device is smaller than a predetermined threshold voltage.

Abstract: A load-dependent frequency modulation circuit and a method thereof for a switching power system. The load-dependent frequency modulation circuit has a control integrated circuit, a feedback circuit and a clock control generator. The control integrated circuit has a clock signal generation terminal and a feedback input terminal. The clock signal generation terminal is used to generate a clock signal. The feedback circuit processes the output of the switching power system, and feedbacks the processed feedback signal to the feedback input terminal. The clock control generator is electrically connected to the feedback input terminal. According to the control signal generated by variation of the feedback signal, the clock frequency at the clock signal generation terminal is adjusted.

Abstract: A protection circuit arranged in a switching power supply system for protecting the switching power supply system is provided. The protection circuit includes a detecting circuit electrically connected to a switching controller of the switching power supply system for providing a trigger signal when a supply voltage drops to an under-voltage level, and a protection circuit electrically connected to the detecting circuit for providing a signal to protect the switching power supply system when the detecting circuit provides the trigger signal to the protection circuit. A method for protecting an switching power supply system is provided. The method includes the steps of detecting that the reference voltage signal disappears when the supply voltage is smaller than a minimum of operating voltage and providing a trigger signal, and providing an protection to protect the switching power supply system in response to the trigger signal.

Abstract: A method and a circuit for detecting a light load mode of a switching power supply system are provided. The switching power supply system has a first winding, a second winding, a third winding having a voltage being in proportion to an output voltage of the second winding, and a signal converting device electrically connected to the third winding. The method includes steps of measuring a voltage of the signal converting device, and determining the switching power supply system being under the light load mode when the voltage of the signal converting device is smaller than a predetermined threshold voltage.

Abstract: A load-dependent frequency modulation circuit and a method thereof for a switching power system. The load-dependent frequency modulation circuit has a control integrated circuit, a feedback circuit and a clock control generator. The control integrated circuit has a clock signal generation terminal and a feedback input terminal. The clock signal generation terminal is used to generate a clock signal. The feedback circuit processes the output of the switching power system, and feedbacks the processed feedback signal to the feedback input terminal. The clock control generator is electrically connected to the feedback input terminal. According to the control signal generated by variation of the feedback signal, the clock frequency at the clock signal generation terminal is adjusted.

Abstract: A protection circuit arranged in a switching power supply system for protecting the switching power supply system is provided. The protection circuit includes a detecting circuit electrically connected to a switching controller of the switching power supply system for providing a trigger signal when a supply voltage drops to an under-voltage level, and a protection circuit electrically connected to the detecting circuit for providing a signal to protect the switching power supply system when the detecting circuit provides the trigger signal to the protection circuit. A method for protecting an switching power supply system is provided. The method includes the steps of detecting that the reference voltage signal disappears when the supply voltage is smaller than a minimum of operating voltage and providing a trigger signal, and providing an protection to protect the switching power supply system in response to the trigger signal.