Abstract: A switching power supply device that switches setting of an output voltage based on an external signal according to one or more embodiments includes: a transformer including a primary winding and n secondary windings; n synchronous rectification elements provided, corresponding to the n secondary windings; and n?1 switch elements that switch the secondary windings. Each of the n?1 switch elements is kept on or off according to a high or low voltage value out of set voltages of the output voltage, and all or any of the n synchronous rectification elements are selected to synchronously rectify pulse voltage of the secondary windings, and when operation with a high set value of the output voltage stops, a synchronous rectification element used to output the high set value performs switching operation until the output voltage goes down to the low voltage value of the set voltages of the output voltage.

Abstract: A switching power supply device that switches setting of an output voltage based on an external signal according to one or more embodiments includes: a transformer including a primary winding and n secondary windings; n synchronous rectification elements provided, corresponding to the n secondary windings; and n?1 switch elements that switch the secondary windings. Each of the n?1 switch elements is kept on or off according to a high or low voltage value out of set voltages of the output voltage, and all or any of the n synchronous rectification elements are selected to synchronously rectify pulse voltage of the secondary windings, and when operation with a high set value of the output voltage stops, a synchronous rectification element used to output the high set value performs switching operation until the output voltage goes down to the low voltage value of the set voltages of the output voltage.

Abstract: A transformer has a primary winding connected between a pair of dc input terminals via a voltage regulator switch, and a secondary winding connected between a pair of dc output terminals via a rectifying and smoothing circuit. The dc output voltage being applied to the load from the dc output terminals is detected, and the detector output voltage dually divided, to provide two feedback signals of different magnitudes. One of these feedback signals is used by a mode selector circuit to provide a mode select signal for causing the voltage regulator switch to be driven continuously under normal load, and at intervals under light load. Delivered to a conduction terminator circuit, the other feedback signal is thereby used to provide conduction terminator pulses for terminating conduction through the voltage regulator switch.

Abstract: A transformer has a primary winding connected between a pair of dc input terminals via a voltage regulator switch, and a secondary winding connected between a pair of dc output terminals via a rectifying and smoothing circuit. The dc output voltage being applied to the load from the dc output terminals is detected, and the detector output voltage dually divided, to provide two feedback signals of different magnitudes. One of these feedback signals is used by a mode selector circuit to provide a mode select signal for causing the voltage regulator switch to be driven continuously under normal load, and at intervals under light load. Delivered to a conduction terminator circuit, the other feedback signal is thereby used to provide conduction terminator pulses for terminating conduction through the voltage regulator switch.