The switch operation and the transient overvoltage caused by direct or indirect lightning will interfere in the electronic equipment. All of electronic products or components need to be protected in order to avoid the surge effect caused by switch or lightning.
This area is belong to low current area, the voltage and current will meet the ohm law characteristic, the resistor coefficient is about 1012~1013Ω, considered as an insulator. It will affect by temperature, when the temperature is raising, the current will increase through the MLV. This current is called Leakage Current.
(b) Breakdown Region
This area is the MLV working and breakdown area which the voltage and current doesn’t meet Ohm's law. When the voltage slight change, the current will have significant change. MLV is using this characteristic to protect the circuit
This area is belong to high current area, which the voltage and current meets Ohm’s law and the resistance coefficient is about 1~10Ω. The reason for this condition is because insulation breakdown and the collapse of the insulating layer makes the zinc oxide grains in parallel connection.
|0402||Cellular phone，Notebook，Digital Camera，PDA，MP3，Motherboard，LCM，HUB，microphone，WLAN，VOIP|
|0805||Charger, Notebook，ISDN，card reader , POS，small fan，toy，VGA CARD|
|1206||Security products, Controller, Industrial PC, Security Gate|
|1812||Automobile LCD，Car light system protection, ADSL，VDSL|
|2220||Car wiper, Medical equipment, Power supply|
It is defined as the MLV internal circulation of 1mA/cm2 current value of the applied voltage. For the Zinc oxide varistors, the breakdown voltage is related to the microstructure grain size, not change due to the volume and variety of the composition of the device.
It’s called Nonlinear Exponent to adjust MLV characteristic parameter. This value is related to the MLV construction and also the composition variety. It could use the calculation formula to check out.
α = log ( I1 / I2 ) / log ( V1 / V2 )
Under normal working status of the device, there is only a few μA micro-currents flowing through the device generally. Under normal working status refers to a device in the normal operating voltage (Working Voltage), that is, the device is in a State of pre-breakdown, the resistance values is high can be seen as an insulator, and only a tiny current flows General is using breakdown voltage 80% make the test.
Max Clamping Voltage:
Maximum peak voltage across the MLV measure at a specified pulse current and waveform.
Max Peak Current:
MLV major function is absorb the overvoltage current, so the peak current of MLV is the major characteristic. Also this test will affect the product lifetime and the largest surge current with surge width into anti. General test method is 8/20μS and 10/1000μS.
Max Energy Absorption:
When the surge hit, MLV breakdown when it is working, there would be a large current flows through the body, energy is absorbed by MLV. MLV absorb energy has its limits. Its test methods such as surge tolerance, standard surge current test, using the formula conversion.