| 摘要 |
<p>Voltage of a terminal (C) at a high impedance is set to a fixed voltage (2.5 V) by a constant current source (301) and a resistor (302), and whether the voltage of the terminal (C) is a fixed voltage which is between 3.5 V and 5.5 V or not is detected by comparators (303, 304) and a NOR circuit (306). A control signal is sent from an ECU (1) to the terminal (C) to turn on a switching transistor (401) to lower a divided voltage so that the alternator (3) generates a high voltage only when the voltage of the terminal (C) is the special voltage, and generates normal voltage otherwise. In case of disconnection of the communication line (2) or grounding of the communication line (2), or when the battery voltage is applied to the communication line (2), the voltage of the terminal (C) does not become abnormal voltage but become the normal voltage. Thus, the battery (4) is protected from abnormal voltage. <IMAGE></p> |
