The Problem:

When working with MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), heat is a common issue that can cause the device to shut down if it gets too hot. This is a protective feature called over-temperature shutdown. If the MOSFET gets too hot, it can fail, damaging your circuit and components. The main reason for overheating is excess current or inadequate heat dissipation.

The Solution:

To prevent MOSFETs from shutting down due to heat, you need to manage their temperature effectively. You can do this by ensuring proper heat sinking and using thermal shutdown circuits. A simple way to implement this is by adding a temperature sensor to monitor the MOSFET’s temperature. If it exceeds a threshold, the circuit can automatically reduce the power or shut down, keeping everything safe.

Practical Example:

Let’s say you’re building a motor controller circuit using a MOSFET, and it shuts down unexpectedly. The problem could be that the MOSFET is overheating due to excessive load. By adding a temperature sensor (like a thermistor) to the circuit, you can monitor the MOSFET’s temperature. If it reaches a certain level, you can have the circuit reduce the current flow or turn off the MOSFET, ensuring that it doesn’t overheat and cause damage.

Sample Calculation:

If your thermistor has a resistance of 10kΩ at room temperature and changes by 2kΩ per °C increase, you can calculate the voltage drop across the thermistor at a certain temperature.

For example, at 50°C, the resistance would be 20kΩ, and if paired with a 10kΩ resistor, you can calculate the voltage divider output.

This helps determine when the MOSFET needs to shut down.

Products Suggestion:

For your projects, consider using MOSFETs and thermal sensors. Both can be found easily at SmartXProKits. Shop now at SmartXProKits.

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