The Problem :

When MOSFETs operate under high load or poor ventilation, they can heat up rapidly. If this thermal rise isn’t managed, it can lead to permanent failure or circuit damage. That’s where thermal shutdown circuits come in—they cut off the load when the MOSFET gets too hot.

The Solution :

Pair your MOSFET with a thermistor and a comparator circuit. When the thermistor senses a temperature rise (say above 80°C), it triggers the comparator to shut down the gate drive, turning the MOSFET off until temperatures normalize.

Real-World Example :

In an LED driver project running from a 12V rail, the MOSFET handles about 2A. In summer, the enclosure gets hot, pushing junction temperatures past 100°C. A thermal shutdown circuit ensures your system disables output temporarily—protecting your load and increasing lifespan.

Sample Calculation :

Suppose you use a 10k NTC thermistor with a comparator.

At 85°C, its resistance drops to ~2.7kΩ.

You can set a voltage divider with another 10k resistor to feed into the comparator’s reference.

When voltage drops below the set threshold, the comparator disables the MOSFET gate.

Useful Components :

• MOSFET (Made in India)

• Flux for clean prototyping

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