Over-temperature protection device for automatic reset field effect transistor

Abstract

An over-temperature protection device for an automatic reset field effect transistor belongs to the technical field of electromechanical control, is applied to a field effect transistor switching circuit, has a grounded source electrode, a grid electrode controlled by a preceding-stage circuit and a drain electrode used for controlling an external load, and is characterized by further comprising an in-phase input end of a comparator C1 and an anti-phase input end of a comparator C2 which are connected with over-temperature reference voltage Vref1, the inverting input end of the comparator C1 and the output end of the comparator C2 are connected with one end of the resistor R2, the other end of the resistor R2 is connected with the drain electrode of the field effect transistor, the negative electrode of the diode D1, one end of the resistor R4 and one end of the capacitor C1 are connected with the non-inverting input end of the comparator C2, and the positive electrode of the diode D1and the other end of the resistor R4 are connected with the comparator C1,the other end of the capacitor C1 is grounded, and the resistor R3 is connected with the output end of the comparator C1 and the positive electrode B1 of the auxiliary control power supply, wherein Vref1 belongs to [1.2 UDS, u1] under the normal conduction condition of the field effect transistor; and when the temperature isoverhigh, the field effect transistor is closed for protection.

Description

technical field [0001] The invention belongs to the technical field of electromechanical control, and in particular relates to an automatic reset field effect tube overtemperature protection device. Background technique [0002] Field effect transistor is a new type of power drive transistor, which has been widely used in various control technology fields, especially in the field of electromechanical technology, motor control, heater control, relay control, excitation control, etc. Compared with bipolar transistors, field effect transistors have on-resistance characteristics with a positive temperature coefficient, which is different from bipolar transistors. However, the over-temperature protection of the field effect tube in the prior art either does not have this function, or this function uses a separate temperature sensor to measure the temperature of the field effect tube, which has the following disadvantages: [0003] ① Field effect tubes are prone to damage due to ...

AI Technical Summary

Problems solved by technology

[0003] ① Field effect tubes are prone to damage due to excessive junction temperature without temperature rise protection

[0004] ②The use of sensors to detect the temperature of field effect tubes generally makes the sensing element close to the plastic casing of the field effect tube or close to its heat sink. These have thermal resistance, so that the felt temperature change obviously lags behind the actual junction temperature, which is the difference between the junction temperature and the sensor signal. There is actually a binary relationship between them, which makes the protection action lag, and the field effect transistor chip is easily damaged by overheating

[0005] ③When the sensor is used to detect the temperature of the field effect tube, the discreteness of the sensing element and its installation consistency lead to low detection accuracy

[0006] ④ When the sensor is used to detect the temperature of the field effect tube, the sensing element also needs to cooperate with other circuits, which makes the circuit more stable and complicated

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