| 摘要 |
PROBLEM TO BE SOLVED: To magnify a usable temperature range without changing a switching element or a smoothing capacitor, in a switching power unit which is requested to be downsized. SOLUTION: A temperature detecting circuit 40 detects the temperature of a power supply IC 10, and in case that the power supply IC 10 is in a higher temperature state than room temperature, a switching frequency adjusting circuit 50 changes the switching frequency of a switching element TR0, thereby suppressing the heat generation of the switching element TR0, and in case that the power supply IC 10 is in a lower temperature state than room temperature, it changes the switching frequency, thereby preventing the ripple of output voltage from getting over a tolerable range owing to an increase of the equivalent series resistor of a smoothing capacitor C1 consisting of an aluminum electrolytic capacitor. Moreover, when the temperature of the power supply IC 10 gets over an overheat protection temperature, it stops driving the switching element TR0 by the driving circuit 30. COPYRIGHT: (C)2009,JPO&INPIT
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