| 摘要 |
PROBLEM TO BE SOLVED: To provide a charging circuit for feeding more charging current while suppressing heat generated by a transistor essential for charging. SOLUTION: A charging circuit consists of an external power supply, a step-down DC/DC converter for stepping down the voltage of an external power supply, a secondary battery E that is charged by the output of the step-down DC/DC converter, and a step-up DC/DC converter IC2 where the output of the step-down DC/DC converter or the secondary battery E is outputted and output after step-up is used as a system power supply, thus varying the output voltage of the step-down DC/DC converter according to a battery voltage and at the same time making constant the output voltage of the step-up DC/DC converter when the output voltage of the step-up DC/DC converter IC2 reaches a preset voltage.
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