Design and Simulation of anti reverse connection circuit based on MOS transistor

        This article is based on MOS Design of anti reverse connection circuit of tube , The previous post is based on MOS Over voltage protection of , Its core principle is control MOS On and off of . In terms of anti reverse connection , Circuit design can also be based on this principle .

1.NMOS Anti reverse circuit

（1） When the power supply is normally connected

        When the circuit is normally connected , Because of the voltage stabilizing effect of the zener diode ,NMOS Tubular Vgs>Vgs(th), here NMOS Working in the on state .

 （2） When the power supply is reversed

          After the power supply is reversed ,NMOS The conduction condition will not be met （Vgs=0V）, So turn off .

2.PMOS Anti reverse circuit

         PMOS and NMOS Circuit similarity , Also by 3 Components , The principle and NMOS equally , I won't go into details here .

3. Add

        For the above anti reverse connection circuit , I think other people's circuits seem to use only one resistor and one MOS tube , No zener diode . I thought about , In fact, do you use zener diode , Can prevent reverse connection , But in normal operation （ Positive connection of power supply ） The maximum voltage of is different , If the zener diode is not used , When the circuit works normally ,Vgs Will be equal to the input voltage ,MOS Tubular Vgs There must be a maximum , So for different MOS, When used in anti reverse circuit , This maximum value determines the maximum working voltage of the circuit .

        What about the circuit with zener diode ? Circuit with zener diode ,MOS Of Vgs It is always clamped at the stabilized voltage during normal operation , So don't worry because Vgs Too large a tube will puncture .

        Vgs The nominal withstand voltage is generally 20~30v about , For anti reverse connection circuit design , My advice is , Select the model first MOS, And according to it Vgs Withstand voltage and voltage of practical application circuit , Decide whether to add zener diode , Of course , It's better to add more if conditions permit .

        For the above simulation circuit , I have applied it in practical circuits , No problem at all , Share it for your reference and study , If there is something wrong , Also please correct me ！