| 摘要 |
A switching power supply circuit that uses, as the core of a transformer or choke coil, a magnetic substance that is more difficult to be magnetically saturated than ferrite, while appropriately protecting a switching element. The switching power supply circuit comprises a transformer (20) that has primary and secondary side windings and also has a core including a magnetic substance of amorphous metal; a switching element (30) that causes a current to flow through the primary side winding of the transformer in accordance with a pulse-shaped drive signal; a primary side current detecting circuit (40) that detects a current following through the primary side winding of the transformer; a plurality of circuit elements that rectify and smooth a voltage developed across the secondary side winding of the transformer to generate an output voltage; and a control circuit (70) that generates, based on at least a detection result of the primary side current detecting circuit, the drive signal, while limiting a period during which to cause the current to flow through the primary side winding of the transformer.
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