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Sorry for the confusing topology.
The idea is as it follows - the charging capacitor is representative of a NTC thermistor responding to a change in temperature. The resistance of the NTC falls, with rising temperature and the voltage rises at the common point (green line) . At first temperature rises a bit sharply, due to lack of air cooling and reaches the threshold of the op amp on the right, which triggers a forced air cooling (fan). This air cooling can be seen to slow down the heating and voltage rise rate, but let's say for some reason it keeps rising slowly towards critical. At some point it reaches a critical temperature, which in turn triggers the threshold of the op amp on the left. Its job would be to introduce a maximum negative feedback in the path of the heating element (thus disabling it). At this point, the critical protection is reached, the heating element disabled and the fan is still operational, which lowers the temperature quickly until it reaches the lower hysteresis point of the op amp on the left. In turn, the heating element is once again enabled and force cooled by the fan until it reaches a critical temperature again.
Ideally, when working with output transistors, this critical protection should never enable (if heatsink is well sized, good airflow, low ambient temperature, device under operating conditions etc). However, having such a protection is always handy.
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