| 摘要 |
PURPOSE:To make input current constant by a method wherein a temperature sensor for detecting temperature of a switching element is provided while ON time of the switching element becomes shorter as the detected temperature rises. CONSTITUTION:A switching transistor 27 of a switching circuit 25 is controlled to turned ON/OFF by a control circuit 35 comprising a microcomputer 33 and a transistor driving circuit 34 while when the detected temperature of a temperature sensor 36 is 40 deg.C or higher, the microcomputer 33 controls ON time of the switching transistor 27 to be shorter every 5 deg.C between 40 deg.C and 60 deg.C. Therefore, peak current of the switching transistor 27 is reduced to make input current drop so that constant control of the input current is possible.
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