| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply detection circuit which prevents erroneous detection at the come-off of a power supply without the need for an external diode for backflow prevention. SOLUTION: The power supply detection circuit is constituted in such a manner that a contained backflow prevention switch is arranged between the power supply and a PMOS transistor for controlling a charging current or a charging voltage, and the backflow prevention switch is turned off for a certain period of time at a certain cycle when the charging current is lowered to a set current or below due to the come-off of the power supply. Since there exists no backflow from a secondary battery during the backflow prevention switch is turned off, a voltage of a power supply terminal is lowered, and the come-off of the power supply can be detected, the erroneous detection at the come-off of the power supply can be prevented without inserting the external backflow prevention diode between the power supply and the PMOS transistor. COPYRIGHT: (C)2008,JPO&INPIT
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