Sanken Electric Co., Ltd.

Tetsuya Niijima

Hiroyuki Chikashige

In a direct-current power supply device that includes a smoothing capacitor C, which performs a DC/DC converter operation, a transformer T, a switching element Q, a diode D, a smoothing capacitor C, a reactor L, which performs a PFC operation, a fast recovery diode Dand a switching element Q, when compared with the case of a rated load, the voltage of the smoothing capacitor Cof 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. A direct-current power supply device, in which a switching element Qused by a PFC circuit is shared as a switching element Qby a DC/DC converter, includes voltage suppression means (switching elements Qand Qand resistance R) for supplying electric charge accumulated in a smoothing capacitor Cto a power supply Vcc of a control circuit CTLthat controls the switching element Qat a time when a load is light in order to suppress a rise in voltage in the smoothing capacitor C

Direct current power supply device

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. This control circuit includes: a current variation measurement circuit for measuring a gradient of the electric current flowing through the switching device, based on a current measurement signal output from a circuit for measuring this electric current; and an overcurrent detection-point correction circuit for correcting the overcurrent detection point with respect to the electric current flowing through the switching device, based on a signal output from the current variation measurement circuit.

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Niiza, Japan

Tetsuya Niijima