Many circuits can benefit from protection against accidental reverse polarity.While most can be protected by polarized connectors to the power source, many hobbyist circuits and kits can be powered by jumper wires, thus eliminating this simple type of polarity protection. In these cases, a reverse polarity circuit would be a very useful addition to your circuit.
In this guide, we will explore three simple methods for adding this protection to your projects. This overview will only cover protection circuits on the high (positive) side of the circuit. Each of the protection methods can also be applied to the low (ground) side. The low side versions of these circuits offer the benefit of using NPN & N-channel devices instead of their PNP or P-channel equivalents, the former which are often cheaper, more readily available and sometimes higher performance. However, low side circuits change the voltage level of the ground path which could cause issues for some circuits.
If you wish to study low side approaches, App Note AN636 from Maxim is a good one to consult. I think for most circuits, the high side versions work very well and will prevent any possible problems with a low side approach. Therefore, we … Read the rest