When working with MOSFETs in power electronics, overcurrent conditions can silently destroy your components if not addressed. Overcurrent often occurs due to short circuits, stalled motors, or unexpected load surges—leading to overheating and eventual failure. Thankfully, simple overcurrent detection methods can protect your circuit.

⚠️ The Problem: MOSFETs Don’t Always Fail Loudly

Unlike fuses that blow visibly, a stressed MOSFET may partially degrade, causing intermittent behavior. This is risky in DIY power supplies, motor drivers, or LED dimmers.

✅ The Solution: Use a Sense Resistor + Comparator

To detect overcurrent:

• Insert a low-value shunt resistor (e.g., 0.1Ω) in the MOSFET’s source path.

• Feed the voltage across it to a comparator or op-amp.

• If the sensed voltage exceeds your threshold (indicating high current), use the output to cut off the gate drive or trigger a fault.

🔧 Practical Example

Let’s say your load should not exceed 2A. Using Ohm’s Law (V = IR), and R = 0.1Ω:

V = 2A × 0.1Ω = 0.2V

Set your comparator to trigger at 0.2V and disable the gate to prevent damage.

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