In electronics, one of the common problems you might face while using MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) is overcurrent—when too much current flows through the MOSFET, leading to overheating or failure. Understanding how to protect your MOSFET from overcurrent can save you time and money in your prototypes.

The Problem :

When you use MOSFETs in a circuit, they are often tasked with controlling high-current loads. If the current exceeds the MOSFET’s rated limit, it can get damaged. To prevent this, an overcurrent protection circuit is needed. This can be done by integrating a current sensing resistor or using a dedicated overcurrent protection IC, which monitors the current flow and shuts down the circuit when an overload is detected.

Practical Example :

Imagine you’re building a simple DC motor controller. If the motor stalls, the current can spike and damage your MOSFET. To fix this, you can add a low-value current sensing resistor in series with the motor. When the current exceeds a certain threshold, the circuit triggers a shutdown mechanism, saving your MOSFET from damage.

Sample Calculation :

Let’s say you use a 0.1Ω current sensing resistor. If the motor draws 2A, the voltage across the resistor will be:

V=I×R=2A×0.1Ω=0.2V

This voltage is fed to the comparator. If the threshold is set to 0.3V, the circuit will trigger protection before any damage occurs.

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