Chip varistor is a resistor with nonlinear volt-ampere characteristics, is a widely used in electronic circuits in the protection of components, its main role is to fight against over-voltage and voltage spikes in the circuit to protect other electronic components from damage, this article will be popularized chip varistor model parameters, as well as functionality and other information.
Chip varistor common models are:
1、EPCOS/Siemens
S14K: S14K series is a standard chip varistor with high energy absorption capacity and fast response time, they are suitable for a variety of circuit protection applications, including power lines, communication lines, automatic control equipment.
2、Littelfuse V
series:Littelfuse V series chip varistors, widely used in electronic equipment and industrial equipment over-voltage protection, the series has a compact size and high energy absorption capacity, suitable for high-density circuit board design.
3、Panasonic ERZ-V
series:Panasonic ERZ-V series are chip varistors with excellent high energy absorption capability and fast response time, these resistors are suitable for power protection, communication equipment, industrial control equipment and other applications.
4、AVX TransGuard
series:AVX TransGuard series chip varistors provide advanced circuit protection features, including overvoltage, overcurrent and ESD (electrostatic discharge) protection, these resistors are widely used in telecommunications, computers, automotive electronics and other fields.
5、TDK EZA
series:TDK's EZA series of chip varistors for a variety of circuit protection needs, they have a high energy absorption capacity, low-voltage promotion and fast response characteristics of the power line, communication lines, industrial equipment and other applications to provide reliable protection.
The above are only some common chip varistor models, there are many other brands and models available on the market, when choosing a chip varistor, you should select the appropriate model according to the specific application requirements and circuit design.
Chip varistor parameters are voltage, leakage current, VAC, VDC, IP, VC, ITM and so on:
1, voltage-sensitive voltage (V1mA) refers to the voltage across the piezoresistor when the piezoresistor passes 1mA current;
2、Leakage current (IR) means the current flowing through the varistor generally measured at 83% of the varistor voltage;
3, VAC means the alternating current voltage that can be continuously applied to both ends of the MOV at a specified temperature;
4, VDC means the direct current voltage that can be continuously applied to both ends of the MOV at a specified temperature;
5, IP refers to the peak value of the inrush current of a certain waveform, MOV is generally measured using 8/20μs current waveform;
6, VC refers to the clamp voltage, that is, in the inrush current IP under the voltage across the MOV;
7, ITM refers to the MOV does not cause failure, can be a single application of the specified waveform pulse rated maximum, it should be noted that the ITM for destructive testing, testing the ITM MOV is not recommended for use in the circuit.
The role of chip varistors
1、Over voltage protection
Chip varistor in the circuit as an over-voltage protection element, can fight against the over-voltage situation in the circuit, when there is too high a voltage in the circuit, the chip varistor will respond quickly and protect other electronic components by absorbing the over-voltage into itself, it can absorb and disperse the energy of over-voltage, to ensure that the other components in the circuit is not subjected to too large a voltage shock.
2、Energy absorption
Chip varistor has high energy absorption ability, can effectively absorb the energy pulse in the circuit, when there is an overvoltage or voltage spike in the circuit, the chip varistor will conduct quickly, the energy of the overvoltage will be absorbed into itself, so as to protect the other components in the circuit, it can absorb a large amount of energy, and will be converted into heat for dissipation.
3, fast response time
Chip varistor has a fast response time, can quickly react and protect in the circuit, when overvoltage occurs in the circuit, the chip varistor response time is very short, almost immediate conduction, so that it can quickly overvoltage energy absorption and decentralization, to prevent it from causing damage to other components.
4、Reactive power dissipation
Chip varistor in the normal operating state almost does not consume power, it is only in the circuit when the overvoltage conducts and absorbs energy, once the overvoltage disappears, the chip varistor will return to the non-conducting state, almost no impact on the normal operating state of the circuit, which makes it in the protection of circuits with a low power consumption characteristics.
To summarize, SMD varistors are commonly used in power supply systems, surge suppressors, security systems, motor protection, automotive electronic systems, household appliances and other electronic products, through the use of SMD varistors, you can improve the reliability and stability of the circuit, to extend the service life of the other components, and to ensure that the electronic equipment in the face of voltage fluctuations and emergencies can work properly.