Low Cost Reverse Polarity And Over Current Protection (corrected) Apr 2026

If current exceeds the limit, the PTC heats up rapidly, its resistance spikes, and it effectively "opens" the circuit until the fault is removed and it cools down. 📐 Circuit Design Value/Part No. Q1 P-Channel MOSFET Reverse Polarity Switch F1 PTC Resettable Fuse Over-current Protection D1 10V - 15V Zener Gate Over-voltage Protection R1 10kΩ - 100kΩ Gate Pull-down 💡 Key Advantages

) rating is higher than your input voltage. If not, use the Zener diode to clamp it.

This circuit provides a robust, low-cost solution for protecting sensitive electronics from two common killers: accidental battery reversal and excessive current draw. By using a P-Channel MOSFET instead of a standard diode, you achieve high efficiency with minimal voltage drop. 🛠️ The Core Components If current exceeds the limit, the PTC heats

Acts as the main switch for reverse polarity protection.

Unlike a standard diode that loses ~0.7V, a (e.g., AO3401 or IRF9540) has very low "on-resistance" (RDSon). If not, use the Zener diode to clamp it

Always choose a PTC with a "Hold Current" slightly above your maximum expected operating current to avoid nuisance tripping.

While the MOSFET stays cool, the PTC will get hot during a fault—keep it away from heat-sensitive components like electrolytic caps. To help you select the specific components, tell me: Your input voltage range? The maximum current your device pulls? 🛠️ The Core Components Acts as the main

Protects the MOSFET Gate from high voltage spikes.