| 摘要 |
PROBLEM TO BE SOLVED: To provide a surge protection circuit for a vehicle meter capable of protecting electronic components, even under a condition of severe fluctuation of a power supply voltage for the vehicle meter.SOLUTION: A surge protection circuit for a vehicle meter includes: switch means 3 consists of a P-channel MOS FET for switching power supply and cutoff from a power supply B to a load 2; a voltage limiting transistor 52 for detecting over-voltage of the power supply B and driving a switch means 3; a current limiting transistor 62 for detecting over-current of the power supply B and driving the switch means 3; a capacitor 4, connected at an output terminal of the switch means 3, for supplementing power to the load 2; and a Zener diode 7 for limiting each voltage between collector and emitter of the voltage limiting transistor 52 and the current limiting transistor 62, and limiting a voltage between gate and source of the switch means 3.SELECTED DRAWING: Figure 1 |
