| 摘要 |
PROBLEM TO BE SOLVED: To provide a charging device with a temperature protection feature capable of preventing the heat generation of a charging control transistor and of continuing charging. SOLUTION: Upon starting to charge an external power supply 21, a control circuit 34 controls a transistor 25 to flow charging current to a battery 22 through a transistor 26, thereby generating heat in the transistors 25, 26. The heat generation is detected by temperature detection circuits 23, 24. While the temperature does not rise, the output of an operational amplifier 32 is at a high level to turn on a driving transistor 30 for the transistor 25 because the voltage value of a first voltage reference 33 is high. When the temperature rises and the output of the temperature detection circuit 23 reaches the voltage value of the first voltage reference 33, the on-resistance of the transistor 30 becomes high because of the output drop of the operational amplifier 32 and the gate voltage of the transistor 25 increases to cause the high on-resistance, thereby decreasing the charging current. Further, the calorific value of the transistor 25 decreases and the output of the temperature detection circuit 23 does not increase, so that the output voltage value of the temperature detection circuit 23 becomes equal to that of the first voltage reference 33 to continue charging. COPYRIGHT: (C)2008,JPO&INPIT
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