Thermistor type over-current protection circuit
Thermistor type over-current protection circuit
A thermistor-type over-current protection circuit, comprising zinc oxide varistor, a ceramic PTC thermistor circuit to be protected; the circuit to be protected and the ceramic PTC thermistor is connected in parallel, and then pressing and zinc oxide sensitive resistors connected in series. The effect of the program is to improve the technology of zinc oxide varistors reliability, to avoid prolonged overvoltage failures caused by sensitive; accelerate the speed of protecting ceramic PTC thermistors; reduce the speed of the ceramic PTC thermistor protection by the ambient temperature affected.
A thermistor-type over-current protection circuit, which is characterized by comprising zinc oxide varistor, a ceramic PTC thermistor circuit to be protected; the ceramic circuit connected in parallel with the PTC thermistor is protected, then connect with zinc oxide varistor series.
Thermistor type over-current protection circuit
Technical field
[0001] The technical solution belongs to the technical field of electronic circuits, in particular to a thermistor-type over-current protection circuit.
BACKGROUND
[0002] Zinc oxide varistor with nonlinear voltage characteristics, are generally used to make electronic circuits against excessive voltage, lightning protection devices, its working principle is varistors and connected to the protected circuit when the line voltage is lower than the operating voltage varistor varistor high resistance, almost open, and thus will not affect the normal operation of the device or electrical equipment. When the voltage is higher than a certain value the moment, the varistor resistance decreased rapidly conducting high current, the voltage clamp within the protected device or electrical equipment can withstand the voltage range to protect the protected device or electrical equipment. Zinc oxide varistor absorbs the energy conduction, its temperature rises quickly, so the energy can be absorbed by the varistor conduction is limited, if too high temperature will result in thermally varistor breakdown failure.
SUMMARY OF THE INVENTION
[0003] In order to solve the above problems in the prior art, the present technique is proposed a overcurrent protection circuit,
Follows:
A thermistor-type over-current protection circuit, which is characterized by comprising zinc oxide varistor, a ceramic PTC thermistor circuit to be protected; the ceramic circuit connected in parallel with the PTC thermistor is protected, and then Zinc oxide varistor connected in series.
[0004] The principle of the technical solution as follows:
Ceramic PTC thermistors have a non-linear resistance-temperature characteristics, is now widely used in various electronic circuits instead of the traditional blown fuse did flow, overload protection. Its working principle is: When the circuit is in a normal state, ceramic PTC thermistor is less than the rated current through the current, PTC thermistor is normal, the resistance is small, does not affect the normal operation of the circuit to be protected. When the circuit fails, the current is greater than the rated current, PTC thermistor suddenly heating, high-impedance state, so
Relative circuit is "off" state, thereby protecting the circuit from damage. When troubleshooting, overcurrent protection with PTC thermistor will automatically return to low resistance state, the circuit resumes normal operation.
[0005] The technical solution set overvoltage protection and overcurrent and overload functions in one. At the same time because when an overvoltage condition, the varistor heat conduction and heat quickly passed to the ceramic PTC thermistors, PTC thermistors and resistance temperature rise due to the rapid increase, in turn, protect the varistor avoid thermal breakdown due to high temperature, which greatly improves the reliability of zinc oxide varistors. At the same time because of the heat-sensitive coupling relationship with PTC thermistor, speed up the rate of PTC thermistor protection and reduce the speed of the level of protection PTC thermistor is affected by the ambient temperature.
[0006] the effect of the technical program are as follows:
1, to improve the reliability of zinc oxide varistors, avoid prolonged overvoltage caused by pressure-sensitive failure.
[0007] 2, accelerate the speed of protecting ceramic PTC thermistors.
[0008] 3, to reduce the impact of ambient temperature ceramic PTC thermistor protection speed by.
Brief Description
[0009] Figure 1 is a thermistor type over-current protection circuit;
Fig 1 - zinc oxide varistor 2 - ceramic PTC thermistor.
Embodiment
[0010] below with reference to specific embodiments of the present technical solution is further described as follows: A thermistor-type over-current protection circuit, comprising zinc oxide varistor, a ceramic PTC thermistor circuit to be protected; the After being connected to the protection circuit in parallel with the ceramic PTC thermistors, and then with zinc oxide varistor connected in series.
上一篇：Dual thermistor self protection, over-voltage and over-current protection circuit
下一篇：Method and apparatus for controlling the resistance of a thermistor device without