Abstract: An insulated power supply apparatus includes: a transformer; a switching element connected in series with a primary-side winding of the transformer; an active clamp circuit connected between terminals of the winding; and a semiconductor device for power supply control that controls the switching element and the active clamp circuit. A current-to-voltage converter element is connected in series with the switching element. The semiconductor device includes: a circuit that generates a timing to turn off the switching element based on a voltage obtained by conversion by the converter element and a predetermined turn-off threshold level; a circuit that performs ON/OFF control of the switching element in a burst mode at a predetermined load or less; and a circuit that, in the burst mode, changes a burst frequency to be lower as a load current is smaller with the number of switching times of the switching element in one burst cycle fixed.

Abstract: An insulated power supply apparatus includes, a transformer; a switching element connected in series with a primary side winding of the transformer; an active clamp circuit connected between terminals of the primary side winding of the transformer; and a power supply control semiconductor device. The switching element includes a field effect transistor and a current-voltage conversion element is connected between a source terminal of the switching element and a grounding point. The power supply control semiconductor device includes the following, a first external terminal in which voltage according to a drain side of the switching element is input, a second external terminal in which voltage converted by the current-voltage conversion element is input, an on/off control circuit that performs turn-on and turn-off of the switching element, and a ZVS determining circuit that determines whether zero voltage switching control is performed.

Abstract: Disclosed is a switching power supply device including: a transformer for voltage conversion; a main switching element connected in series to a primary coil; a primary side control circuit that performs on/off control of the main switching element; a synchronous rectification MOS transistor connected in series to a secondary coil; and a secondary side control circuit that performs on/off control of the MOS transistor, wherein the secondary side control circuit includes: an off-timing detection circuit that compares a drain voltage of the MOS transistor with a predetermined threshold voltage, and detects a timing to turn off the MOS transistor; and a threshold voltage setting circuit that sets the threshold voltage, and the threshold voltage setting circuit sets the threshold voltage based on a conduction period of the secondary coil or a period obtained by adding the conduction period to a conduction period of the primary coil.

Abstract: A switching power supply device includes a transformer for voltage conversion, a synchronous rectification MOS transistor, and a secondary side control circuit. The synchronous rectification MOS transistor is connected in series to a secondary side coil of the transformer. The secondary side control circuit performs on/off control of the synchronous rectification MOS transistor based on a drain voltage of the synchronous rectification MOS transistor. The secondary side control circuit includes a peak period detection circuit and a determination reference voltage generation circuit. The peak period detection circuit detects a peak period of the drain voltage. The determination reference voltage generation circuit generates a reference voltage to be used as a reference for determining the peak period based on a voltage in the peak period. The peak period detection circuit detects the peak period based on the drain voltage and on the reference voltage.

Abstract: A switching power supply device includes a transformer for voltage conversion, a synchronous rectification MOS transistor, a secondary side control circuit, and a minimum on-time setting circuit. The synchronous rectification MOS transistor is connected in series to a secondary side coil of the transformer. The secondary side control circuit performs on/off control of the synchronous rectification MOS transistor based on a drain voltage of the synchronous rectification MOS transistor. The minimum on-time setting circuit sets a minimum on-time when turning on the synchronous rectification MOS transistor based on a peak period and a bottom period detected by the secondary side control circuit.

Abstract: A switching power supply device includes a transformer for voltage conversion, a synchronous rectification MOS transistor, a secondary side control circuit, and a minimum on-time setting circuit. The synchronous rectification MOS transistor is connected in series to a secondary side coil of the transformer. The secondary side control circuit performs on/off control of the synchronous rectification MOS transistor based on a drain voltage of the synchronous rectification MOS transistor. The minimum on-time setting circuit sets a minimum on-time when turning on the synchronous rectification MOS transistor based on a peak period and a bottom period detected by the secondary side control circuit.

Abstract: A switching power supply device includes a transformer for voltage conversion, a synchronous rectification MOS transistor, and a secondary side control circuit. The synchronous rectification MOS transistor is connected in series to a secondary side coil of the transformer. The secondary side control circuit performs on/off control of the synchronous rectification MOS transistor based on a drain voltage of the synchronous rectification MOS transistor. The secondary side control circuit includes a peak period detection circuit and a determination reference voltage generation circuit. The peak period detection circuit detects a peak period of the drain voltage. The determination reference voltage generation circuit generates a reference voltage to be used as a reference for determining the peak period based on a voltage in the peak period. The peak period detection circuit detects the peak period based on the drain voltage and on the reference voltage.

Abstract: Disclosed is a switching power supply device including: a transformer for voltage conversion; a main switching element connected in series to a primary coil; a primary side control circuit that performs on/off control of the main switching element; a synchronous rectification MOS transistor connected in series to a secondary coil; and a secondary side control circuit that performs on/off control of the MOS transistor, wherein the secondary side control circuit includes: an off-timing detection circuit that compares a drain voltage of the MOS transistor with a predetermined threshold voltage, and detects a timing to turn off the MOS transistor; and a threshold voltage setting circuit that sets the threshold voltage, and the threshold voltage setting circuit sets the threshold voltage based on a conduction period of the secondary coil or a period obtained by adding the conduction period to a conduction period of the primary coil.

Abstract: A switching power source apparatus includes: a synchronous rectifier switching element for synchronous rectification constituted of an insulated-gate field-effect transistor; and a secondary-side control circuit including a detector circuit and a timer circuit. The secondary-side control circuit performs ON/OFF control of the synchronous rectifier switching element. The detector circuit monitors a voltage of a drain terminal of the synchronous rectifier switching element, and detects an abnormal state in which the voltage of the drain terminal is undetectable. The timer circuit starts up and measures a predetermined time in response to the detector circuit detecting the abnormal state. When the detector circuit detects the abnormal state, and the predetermined time elapses according to the timer circuit, the secondary-side control circuit outputs a detection signal indicating an abnormality to outside.

Abstract: A switching power source apparatus includes: a synchronous rectifier switching element for synchronous rectification constituted of an insulated-gate field-effect transistor; and a secondary-side control circuit including a detector circuit and a timer circuit. The secondary-side control circuit performs ON/OFF control of the synchronous rectifier switching element. The detector circuit monitors a voltage of a drain terminal of the synchronous rectifier switching element, and detects an abnormal state in which the voltage of the drain terminal is undetectable. The timer circuit starts up and measures a predetermined time in response to the detector circuit detecting the abnormal state. When the detector circuit detects the abnormal state, and the predetermined time elapses according to the timer circuit, the secondary-side control circuit outputs a detection signal indicating an abnormality to outside.

Abstract: In a switching power supply device having low loss in synchronous rectifying switches, exhibiting high power efficiency, and not causing troubles by reverse current in the switches. A secondary control circuit includes a reference voltage circuit to generate a reference voltage having a predetermined potential, and an ON-timing detector circuit to detect an ON timing of a synchronous rectifying switch through monitoring of a terminal voltage of the switch, an OFF-timing detector circuit to detect an OFF timing of the switch, and a timer circuit to be turned on at the ON timing and measure a predetermined period. The threshold voltage consisting of the reference voltage generated by the reference voltage circuit and an offset voltage is applied to the OFF-timing detector circuit during the measurement of the timer circuit, and the threshold voltage consisting of the reference voltage is applied to the OFF-timing detector circuit during the non-measurement.

Abstract: In a switching power supply device having low loss in synchronous rectifying switches, exhibiting high power efficiency, and not causing troubles by reverse current in the switches. A secondary control circuit includes a reference voltage circuit to generate a reference voltage having a predetermined potential, and an ON-timing detector circuit to detect an ON timing of a synchronous rectifying switch through monitoring of a terminal voltage of the switch, an OFF-timing detector circuit to detect an OFF timing of the switch, and a timer circuit to be turned on at the ON timing and measure a predetermined period. The threshold voltage consisting of the reference voltage generated by the reference voltage circuit and an offset voltage is applied to the OFF-timing detector circuit during the measurement of the timer circuit, and the threshold voltage consisting of the reference voltage is applied to the OFF-timing detector circuit during the non-measurement.