Abstract: A detector compares a drain voltage with a first threshold voltage and outputs a first detection signal. An ON counter detects a period of time during which a current flows in a switching, counts the period of time based on a predetermined clock cycle. An OFF counter detects a period of time during which a current flow through the body diode in a state where no current flows in the switching circuit, counts the period of time. An off-time setting circuit sets the time to turn off the switching circuit. A first comparison circuit compares the cycle count value with turn off time. A second comparison circuit compares a cycle count value output by the ON counter with a comparison result output by the first comparison circuit and outputs a signal to stop transmitting a PWM signal.

Abstract: A detector compares a drain voltage with a first threshold voltage and outputs a first detection signal. An ON-counter detects a period of time during which current flows in a switching circuit based on the first detection signal, counts the period of time based on a predetermined clock cycle, and outputs an ON-count value. A first comparator receives the ON-count value and an ON-threshold value and outputs a first comparison signal when the ON-count value and the ON-threshold value match. A second comparator receives the ON-count value and a decreased ON threshold value, compares the ON-count value and the decreased ON-threshold value, and outputs a second comparison signal. An ON-mask time adjuster receives the second comparison signal and outputs an ON-threshold value for adjusting a mask time and a decreased ON-threshold value that is less than the ON threshold value.

Abstract: A device and method for controlling a power supply. The method includes: a voltage signal in a primary winding is delayed, and the delayed voltage signal is sampled and held after a time when a rectifying diode stops conducting a current, then the sampled and held signal is used as a feedback signal of the power supply. Therefore, only one sampling and holding circuit is needed, the area of the circuit can be reduced and the cost of the integrated circuit can be decreased, meanwhile regulation characteristics are not deteriorated.

Abstract: A device and method for controlling a power supply. The method includes: a first correction signal is generated according to a down-slope waveform and a second correction signal is generated according to an up-slope waveform, in a period of the switching element. Therefore, two kinds of corrections can be performed by using an oscillator, while the area of the circuit can be reduced and the cost of the integrated circuit can be decreased.

Abstract: A device and method for controlling a power supply. The method includes: monitoring a feedback signal of a feedback terminal; determining whether the feedback signal of the feedback terminal is not a pulse signal; and terminating an on/off operation of a switching element when the feedback signal of the feedback terminal is not a pulse signal. Therefore, an abnormal status of the device can be correctly detected with a simple structure when the feedback terminal is open or is shorted with other terminals, while an error operation and a damage of the device can be avoided.