Abstract: In a direct-current power supply device that includes a smoothing capacitor C1, which performs a DC/DC converter operation, a transformer T1, a switching element Q1, a diode D2, a smoothing capacitor C2, a reactor L1, which performs a PFC operation, a fast recovery diode D1 and a switching element Q1, when compared with the case of a rated load, the voltage of the smoothing capacitor C1 of a PFC circuit rises at a time when a load is light. Therefore, the following has been required: a capacitor having a sufficient withstanding voltage rating, or an operation of connecting a plurality of capacitors in series or any other operation to secure a voltage-withstanding capability.

Abstract: In a direct-current power supply device that includes a smoothing capacitor C1, which performs a DC/DC converter operation, a transformer T1, a switching element Q1, a diode D2, a smoothing capacitor C2, a reactor L1, which performs a PFC operation, a fast recovery diode D1 and a switching element Q1, when compared with the case of a rated load, the voltage of the smoothing capacitor C1 of a PFC circuit rises at a time when a load is light. Therefore, the following has been required: a capacitor having a sufficient withstanding voltage rating, or an operation of connecting a plurality of capacitors in series or any other operation to secure a voltage-withstanding capability.

Abstract: A switching power supply apparatus has a switching device control circuit for performing overcurrent protection by controlling switching-on/off of a switching device, connected serially to a primary winding of a transformer, so as to make a voltage output from a rectifying and smoothing circuit, connected to a secondary winding of the transformer, have a specific value, and switching off the switching device when the electric current flowing through the switching device exceeds a value as an overcurrent detection point.

Abstract: A switching power supply apparatus has a switching device control circuit for performing overcurrent protection by controlling switching-on/off of a switching device, connected serially to a primary winding of a transformer, so as to make a voltage output from a rectifying and smoothing circuit, connected to a secondary winding of the transformer, have a specific value, and switching off the switching device when the electric current flowing through the switching device exceeds a value as an overcurrent detection point.