| 摘要 |
PROBLEM TO BE SOLVED: To reduce stand-by power to be consumed in a control circuit for a power switch to zero to the utmost, though a charging power source and a set are normally separated from each other in a power system for a portable telephone, etc., are connected and used when charging is performed, and it is desired to cut the charging power off to curtail stand-by power consumption, when charging is not performed, i.e., when the set is detached from the charging power source or when a main battery is fully charged, and it used to be necessary to supply power of about 50 mW to the power switch control circuit before to start up the charging power source stably. SOLUTION: A minute power source, whose power consumption is minute, is prepared. The control circuit for causing the charging power source to operate is started up by making the minute power source a closed circuit, when the set is connected to the charging power source. Then the power switch oscillates, and the charging power source operates. Moreover, a starting switch is inserted into a part of the minute power circuit. The switch is opened, when the main battery of the set is charged fully, and is made when its voltage becomes a specified value or lower, to start up the charging power source.
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