| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to detect the state of charge of a power storing means without routing a wire from the power storing means to a power supply device that supplies power to a power consuming device having the power storing means such as a battery and a capacitor. SOLUTION: In a smart entry system, a smart ECU repeatedly supplies power to an in-vehicle receiver having a backup capacitor only for a predetermined supply period per unit time (S110). At least one of monitored power, voltage, and current is compared with a preset threshold value (S120). Based on the magnitude relation between them, it is determined whether or not it is required to charge the backup capacitor. In the smart ECU, therefore, the state of charge of the backup capacitor can be detected without routing a wire for detecting the state of charge of the backup capacitor between it and the in-vehicle receiver. COPYRIGHT: (C)2010,JPO&INPIT
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