Provides simple, low-cost over-current protection.
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 Provides simple, low-cost over-current protection
Ensures the MOSFET stays "OFF" when no power is applied. ⚡ How It Works 1. Reverse Polarity Protection Q1 P-Channel MOSFET Reverse Polarity Switch F1 PTC
Unlike a standard diode that loses ~0.7V, a (e.g., AO3401 or IRF9540) has very low "on-resistance" (RDSon). The Gate is pulled low relative to the
The Gate is pulled low relative to the Source, allowing current to flow freely to the load.
The Gate-Source voltage becomes positive (or zero), keeping the MOSFET closed and blocking current. 2. Over-Current Protection