| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply device which can reduce an operation frequency when a power is not higher than a certain level such as in a steady state, in a light load state, etc., and can increase the operation frequency in a heavy load state which is a capacity limit of a transformer, etc., to contribute to the size reduction and the improvement of a load efficiency. SOLUTION: When a high level output pulse Ve is inputted to a switching device Q1, a voltage Vg is generated in a resistor R17 connected to the source of the switching device Q1 and inputted to a base of a transistor Q5. If the voltage applied to the base exceeds a detection level, the transistor Q5 is turned on and a base voltage of a transistor Q7 is earthed to a GND level via a resistor R55, the transistor Q7 is turned on, a capacitor C13 of an oscillation circuit is charged by a current from a reference voltage Vcc' via the emitter, the collector, and a resistor R57, and the charging current of the capacitor C13 is increased to increase an operation frequency.
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