| 摘要 |
PROBLEM TO BE SOLVED: To provide a vehicular power supply unit which eliminates a battery voltage detection error due to secular change to detect a battery voltage highly precisely for a long time. SOLUTION: The vehicular power supply unit includes a battery 1 for running a vehicle and a voltage detecting circuit 2 which detects the voltage of the battery 1. The voltage detecting circuit 2 has a voltage-dividing resistor 3 which divides a voltage applied to the battery 1, a voltage detecting portion 4 which detects a divided voltage given by the voltage-dividing resistor 3, a bias power supply circuit 5 which is connected to add a bias voltage to the battery 1, a switching element 6 which short-circuits the bias power supply circuit 5, and a calculating circuit 7 which calculates a voltage-dividing ratio of the voltage-dividing resistor 3 from a first detected voltage detected by the voltage detecting portion 4 when the switching element 6 is switched off and the bias power supply circuit 5 adds the bias voltage to the battery 1, and from a second detected voltage detected by the voltage detecting portion 4 in a short-circuit state where the switching element 6 is switched on. COPYRIGHT: (C)2009,JPO&INPIT
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