How does overtemperature protection function in power supplies?

Overtemperature protection causes an emergency shutdown. It prevents thermal damage being caused to a switch-mode power supply or a failure of isolation as a result of excessively high temperatures.

The activation threshold of the overtemperature protection is typically much higher than the specified operating temperature range. The temperature sensor(s) are installed at safety-critical points, for example in the transformer.

After the overtemperature protection has been activated, the power supply shuts down, cools off and automatically attempts to start up again once the temperature has fallen below a specific level.