| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply capable of controlling the generated heat temperature of its main unit to a prescribed temperature range and the main unit of which can be miniaturized. SOLUTION: The switching power supply 10 is provided with a triangular- wave oscillating circuit 22 that generates triangular waves; an FET 14 that generates pulse signals from a DC voltage supplied from a power source 15 based on the frequency of the triangular waves; a smoothing circuit 16 that is provided with a capacitor 16b to smooth the pulse signals and output a DC voltage Va; and a frequency controlling circuit 23 in which resistance changes in accordance with the generated heat temperature of the main unit detected by a thermistor 26. The frequency of the triangular waves is set to fb when the main unit is heated to a high temperature, and set to fa (fa>fb) in the opposite case. As a result, the number of switching times (switching loss) per unit time is controlled, that is, the generated heat value from the main unit is controlled. |
