Dual thermistor self protection, over-voltage and over-current protection circuit
Since dual thermistor type overvoltage protection circuit protection
A dual thermistor type overvoltage protection from overcurrent protection circuit, comprising a pressure-sensitive resistor, the first PTC thermistor ceramic, the second ceramic PTC thermistor
And the protection circuit; said first ceramic varistor and PTC thermistors connected in series, and then connected in parallel with the circuit to be protected, and finally a second ceramic PTC
A thermistor 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 pressure-sensitive;
To solve the conventional overvoltage overcurrent protection device is too slow due to thermistor failure caused by sensitive situation.
A dual thermistor type overvoltage protection from overcurrent protection circuit, characterized in that the varistor comprises a first ceramic
The first varistor ceramic PTC thermistor; PTC thermistor, PTC thermistor and the second ceramic is the protection circuit
Resistor connected in series, connected in parallel circuit to be protected and then, finally connected to the second resistor in series with the ceramic PTC thermistor.
 The technical solution belongs to the technical field of electronic circuits, in particular from a dual thermistor type overvoltage protection overcurrent
 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 below the varistor
When the operating voltage, high resistance varistors, almost open, and thus will not affect the normal operation of electrical equipment or devices
Made。 When the voltage is higher than a certain value the moment, the varistor resistance decreased rapidly conducting high current, the voltage is clamped at
The protection device or electrical equipment can withstand the voltage range to protect the protected device or electrical equipment. Zinc oxide varistor
When the conduction resistance of the energy absorption, its temperature rises quickly, so the energy can be absorbed by the varistor when the conduction is limited, such as
If it can overload will lead varistors high temperature thermal breakdown failure.
SUMMARY OF THE INVENTION
 In order to solve the above problems in the prior art, and the technical solutions proposed a self-protective type overvoltage overcurrent protection
Protection circuits and devices, specific technical programs are as follows:
A dual thermistor type overvoltage protection from overcurrent protection circuit, characterized in that the varistor comprises a first ceramic PTC
Thermistor, PTC thermistor and the second ceramic circuit to be protected; the varistor ceramic PTC thermistor and the first string
Joint connection, and then the protection circuit is connected in parallel with the final connection of the second ceramic PTC thermistors connected in series.
 The principle of the technical solution as follows:
Ceramic PTC thermistors have a non-linear resistance-temperature characteristics, its resistance increases with increasing temperature and with high pressure,
High anti-aging properties, is an excellent thermal protection components。 Meanwhile ceramic PTC thermistors are also widely used in various electronic line
Road 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
Normal operation of the circuit to be protected. When the circuit fails, the current is greater than the rated current, PTC thermistor suddenly issued
Hot, high-impedance state, so that the circuit is relatively "off" state, thus protecting the circuit from damage。 When troubleshooting, overcurrent
Protection PTC thermistor will automatically return to low resistance state, the circuit resumes normal operation.
 The technical program works: When the line voltage exceeds the breakover voltage varistor varistor voltage conduction,
Temperature rises rapidly and passed to the first ceramic PTC thermistor 2, the first ceramic PTC thermistor 2 due to temperature resistance
Rapidly increasing varistor protection to avoid prolonged overvoltage and thermal breakdown, while the second ceramic PTC thermistors 3
But also because the first ceramic PTC thermistors and temperature varistor 2 pass and self-heating temperature, its resistance quickly
Increasing the protected circuit protection, overvoltage protection to achieve the effect. When the line when an overcurrent condition because of PTC thermistor
Itself has overcurrent protection characteristics to achieve the effect of over-current protection.
 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.
 2, to solve the conventional overvoltage overcurrent protection device is too slow due to thermistor failure caused by pressure-sensitive situation.
 Figure 1 is a self-protective structure diagram type overvoltage overcurrent protection circuit;
Figure, varistors 1, the first ceramic PTC thermistor 2, the second ceramic PTC thermistors 3.
 below with reference to specific embodiments of the present technical solution is further described as follows:
A self-protection type overvoltage protection circuit, comprising a pressure-sensitive resistor, the first PTC thermistor ceramic, the second ceramic
PTC thermistor circuit to be protected; said first ceramic varistor and PTC thermistors connected in series, then with the protected
Parallel connection circuit, and finally connected in series with the second ceramic PTC thermistor.
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