1, using diode unidirectional conductivity to prevent the input voltage reverse connection, such a good circuit is simple, the cost is low, but a little loss, because the diode have pressure drop and pressure drop at least 0.2 SS14, but also good, the advantages of schottky diode itself lies in the forward bias voltage is low, not like some of the pressure drop of the diode is larger. But there is a problem is in case the power supply really after the diode conduction will be directly short circuit, so this kind of circuit is generally to add a fuse in the front, if there is no fuse can add 0 ohm resistance instead of insurance, so after the replacement of the fuse or fuse, if there is a condition, add a self-recovery fuse.

2, sometimes can also be connected in this way, when the power is reversed diode cut-off circuit to schottky diode SS14 type for example, its current is 1A voltage is 40V schottky diode, the circuit input voltage should be less than 40V, may be 12V input. Schottky diode, also known as fast recovery diode, is characterized by fast working speed, large current, but the reverse voltage resistance is small, one-way conductivity, the most significant feature is the reverse recovery time is very short, so it is used for high frequency, low voltage, continuous flow diode, protection diode and other occasions.

Anti-input anti-connection protection circuit generally USES the one-way conductivity of the diode or the MOS tube, which can be achieved as follows: