| 摘要 |
PROBLEM TO BE SOLVED: To surely protect a transistor for controlling charging operation which is provided in a charging path. SOLUTION: A voltage across a transistor Tr, provided in the charging path, is detected with a voltage detection circuit 11, and a current flowing into the transistor Tr is detected with a current detection circuit 12. The loss power of the transistor Tr is obtained from a voltage detection signal from the voltage detection circuit 11 and a current detection signal from the current detection circuit 12. When this loss power exceeds the allowable loss of the transistor Tr, the transistor Tr is turned off by a charging control circuit 14.
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