There are two well-known circuits well described in the Internet, including this site:
- Reverse polarity protection with P-channel MOSFET;
- Overvoltage protection with SCR and Zener (so-called "crowbar").
I want to combine them like shown below:
- Polarity and/or voltage of the input cannot change suddenly during operation. It's a standard barrel connector, where a DC power supply is connected. So circuit must be protected against a case where user accidentally plugs in wrong polarity supply, or plugs 24-30V instead of 12V.
- D1 and D2 are both 15 volts.
- Mosfet's maximum ratings are: max current 74A, max voltage across drain-source 55V, max gate voltage 20V.
- Fuse rating is 1.5A
- SCR1 is chosen so, that it's I2t is twice more then I2t of fuse. Actually it's Littelfuse SJ6004DS2RP.
- Load is actually a quite complicated device, which includes linear regulator (AMS1117), MCU with several input devices (buttons, analog inputs), LCD screen, BT transmitters and a couple stepper motors with drivers.
Will this schematic provide protection as expected, against overvoltage and reverse polarity?
EDITED: Is this a suggested layout?