| 摘要 |
PROBLEM TO BE SOLVED: To eliminate power loss due to the flow of a current to a resistor for discharging accumulated electric charge in a switching power supply device. SOLUTION: A first switching element 73 is connected in series with a first discharge resistor 13 for discharging the accumulated electric charge of a filter circuit 14 of AC input, and a second switching element 25 is connected in series with a second discharge resistor 19 for discharging the accumulated electric charge of a smoothing capacitor at the output side of a rectification diode. A switching power supply device is provided with a current detection means 30 for detecting the charge current of the smoothing capacitor 20, and a control means 40 for controlling the first and second switching elements based on a detection signal from the current detection means 30. When AC input is applied, the current detection means 30 detects the presence of the charge current of the smoothing capacitor 20 and transfers it to the control means 40, the control means 40 turns off the first and second switching elements and break current flowing to the first and second discharge resistors, thus eliminating the power loss of the first and second discharge resistors.
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