Principle and Application characteristics of TVS transient Voltage suppression Diode

Principle and Application characteristics of TVS transient Voltage suppression Diode.
Transient suppression diode (TVS), also known as clamp diode, is a highly efficient circuit protection device widely used in the world. Its appearance is the same as that of ordinary diodes, but it can absorb surge power up to thousands of watts. Its main characteristic is that under the condition of reverse application, when it bears a large pulse with high energy, its working impedance is immediately reduced to a very low conduction value, thus allowing large current to pass through. At the same time, the voltage is clamped at a predetermined level, and the response time is only 10-12 milliseconds, so it can effectively protect the precision components in the electronic circuit. The allowable forward surge current of TVS can reach 50,200A under the condition of TA=250C,T=10ms. Bi-directional TVS can absorb instantaneous high pulse power in both positive and negative directions and clamp the voltage to a predetermined level. Bi-directional TVS is suitable for AC circuits and unidirectional TVS is generally used for DC circuits. It can be used for anti-lightning, anti-overvoltage, anti-interference, absorbing surge power and so on. It is an ideal protection device. Tolerance is expressed in watts (W).
Main Electrical parameters of TVS Devices.
(1) breakdown voltage V (BR).
In the region where the breakdown occurs, the voltage at both ends of the device is called the breakdown voltage under the specified test current I (BR). In this area, the diode becomes a low impedance path.
(2) maximum reverse pulse peak current IPP.
When working in reverse, the maximum pulse peak current that the device is allowed to pass through under specified pulse conditions. The product of IPP and the maximum clamp voltage VC (MAX) is the maximum of transient pulse power.
When in use, the TVS should be selected correctly so that the rated transient pulse power PPR is greater than the maximum transient surge power that may occur on the protected device or line.
Classification of TVS diodes.
TVS devices can be divided into unipolar and bipolar according to polarity, and can be divided into general devices suitable for all kinds of circuits and special devices suitable for special circuits according to their uses. Such as: various AC voltage protectors, 4~200mA current protectors, data line protectors, coaxial cable protectors, telephone protectors and so on. According to the package and internal structure, it can be divided into: axial lead diode, dual in-line TVS array (suitable for multi-line protection), patch type, component type and high power module type, etc.
Application of TVS Diode.
At present, it has been widely used in computer system, communication equipment, AC / DC power supply, automobile, electronic ballast, household appliances, instrumentation (watt-hour meter), RS232/422/423/485, LAN, ISDN, ADSL, USB, MP3, PDAS, GPS, CDMA, GSM, digital camera protection, common mode / differential mode protection, RF coupling / IC drive receiving protection, motor electromagnetic wave interference suppression, audio / video input, Sensor / transmission, industrial control circuit, relay, contactor noise suppression and other fields.
Characteristics of TVS Diode.
The main results are as follows: (1) adding TVS diode to the signal and power line can prevent the failure caused by the instantaneous shock of the microprocessor or single-chip microcomputer, such as electrostatic discharge effect, the surge of AC power supply and the noise of switching power supply.
(2) the electrostatic discharge effect can release more than 10000V and 60A pulses and last 10ms, while the general TTL devices will be damaged when they encounter 10V pulses exceeding 30ms. By using the TVS diode, the pulse that will damage the device can be absorbed effectively, and the interference (Crosstalk) caused by the switch between buses can be eliminated.
(3) placing the TVS diode between the signal line and the ground can prevent the data and control bus from being affected by unnecessary noise.
Measurement and judgement of TVS transient Voltage suppression Diode.
1. Measuring the quality of pipes with R × 1k block of multimeter.
For unipolar TVS, the forward and reverse resistance can be measured according to the method of measuring ordinary diodes.
Generally, the forward resistance is about 4k5 and the reverse resistance is infinite.
two。. For the bidirectional polar TVS, the resistance between the two pins should be measured by arbitrarily changing the red and black stylus.
It is infinity, otherwise, the performance of the pipe is poor or has been damaged.