Overheating protection circuit based on p-n junction forward voltage drop temperature characteristic

Abstract

An overheating protection circuit based on a p-n junction forward voltage drop temperature characteristic comprises a voltage conversion circuit and an overheating control signal conversion circuit. The heating sensing element of the overheating control signal conversion circuit is a PNP triode, when the temperature detected by the PNP triode does not exceed a setting value, the emitter junction voltage set by the circuit for the emitter of the PNP triode in advance does not reach the minimum voltage of the conduction, the emitter of the PNP triode is located at a closing state, and a comparator outputs high level to control the normal work of the module required being protected; when the temperature detected by the PNP triode exceeds the setting value, because the emitter junction p-n junction forward voltage has the negative temperature characteristic, the emitter junction conduction voltage of the thermal detection triode is dropped to the circuit preset voltage to allow the emitter to be conducted, and the comparator overturns the output low level to control the closing of the module required being protected to play a thermal protection effect. The voltage conversion circuit employs a high-precision and low-temperature drift reference circuit which is taken as the power supply of the overheating control signal conversion circuit so as to improve the accuracy of the overheating protection.

Description

technical field [0001] The invention belongs to the technical field of overheating protection circuits, and in particular relates to an overheating protection circuit based on the temperature characteristics of the forward voltage drop of a PN junction. Background technique [0002] In switching power supplies and power drive electronic modules, due to the relatively large power dissipation, when the ambient temperature is too high or an internal short circuit occurs, the power consumption will increase sharply, resulting in damage to internal devices due to excessive temperature. In order to prevent the occurrence of the above situation, an overheating protection circuit is generally added inside the module. Commonly used overheating protection circuits are mainly realized by thermistors, temperature switches and temperature fuses. Among the existing over-temperature protection methods, the thermistor and temperature switch detection methods have the disadvantages of serio...

AI Technical Summary

Problems solved by technology

In the existing over-temperature protection methods, the thermistor and temperature switch detection methods have shortcomings such as serious non-linear relationship between resistance and temperature, poor consistency and interchangeability of components, easy aging of components, and poor stability.

In addition to the above-mentioned shortcomings of thermistor and temperature switch, the temperature fuse also has the disadvantage that it cannot be restored after the overtemperature disappears.

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