摘要 |
The technique of the present invention sets two reference voltages, that is, a minimum reference voltage and an operation inhibiting reference voltage, as the criteria for detecting the conditions of power supply of a low voltage power source system including a low voltage battery. The operation inhibiting reference voltage is lower than the minimum reference voltage and represents a threshold value ensuring the normal operation of an apparatus that establishes the power source of a high voltage power source system. In a first range where the power source voltage of the low voltage battery is lower than the minimum reference voltage but is not lower than the operation inhibiting reference voltage, a converter is activated to charge the low voltage battery, so as to recover the power source voltage of the low voltage battery to the minimum reference voltage. The whole system of, for example, a vehicle or an apparatus then functions normally. In a second range where the power source voltage of the low voltage battery is lower than the operation inhibiting reference voltage, on the other hand, operation of the whole system is inhibited. This arrangement brings outs the best performance of the low voltage battery while assuring safety of the whole system. <IMAGE> |