| 摘要 |
PURPOSE:To supply a circuit with source voltage with small voltage drop by inserting a switch means having small voltage drop between a power supply terminal and the circuit to be supplied with power, judging the polarity of the power supply and controlling the switch means. CONSTITUTION:A reverse power supply preventing circuit X is inserted between a power supply terminal 1 and a circuit 2 to be supplied with power and power supply is blocked when the power is supplied with reverse polarity to the power supply terminal 1. In this case, switch means 3 having small voltage drop, for example, a transistor, is inserted between the power supply terminal 1 and the circuit 2. The switch means 3 is controlled by the output from a polarity judging means 4 for judging the polarity of the power supply. That is, the switch means 3 is turned on when the power supply has a forward polarity and turned off when the power supply has a reverse polarity. Thus, power supply is blocked and the circuit is protected against damage. |
