Patent ID: 9276494
Filing Date: 2016-03-01
CPC Classification: H02M,Y02B,Y02P

Claim Text:
1. A switching power supply device that includes: an inductor connected to a rectifier circuit for rectifying AC power, a switching element forming a current path from the rectifier circuit through the inductor in an ON state of the switching element; a diode forming a current path from the inductor to an output capacitor in an OFF state of the switching element; and a control circuit controlling electric current flowing through the inductor by ON/OFF driving the switching element; the control circuit comprising: wherein the zero current detecting circuit receives a signal for controlling ON/OFF driving of the switching element, receives a voltage signal proportional to the current flowing through the inductor in an OFF state of the switching element, compares the voltage signal sequentially with a first comparison reference voltage and a second comparison reference voltage, detects a gradient of the current flowing through the inductor, and detects the timing of zero current flowing through the inductor corresponding to the detected gradient of current; and wherein the zero current detecting circuit comprises a capacitor that is charged by a first constant current source and discharged by a second constant current source, charges the capacitor by the first constant current source after the voltage signal exceeds the first comparison reference voltage until the voltage signal reaches the second comparison reference voltage, then discharges a charged voltage of the capacitor by the second constant current source, and detects a timing at which the charged voltage of the capacitor reaches a third comparison reference voltage through the discharge as the timing of zero current flowing in the inductor.