Transient voltage suppression diode

Transient voltage suppression diode.
Transient voltage suppression diode is referred to as TVS device. Under the prescribed reverse application conditions, when it is subjected to a high-energy instantaneous overvoltage pulse, its working impedance can be immediately reduced to a very low conduction value, allowing large current to pass through, and clamping the voltage to a predetermined level, so as to effectively protect the precision components in the electronic circuit from damage. It is a kind of high efficiency circuit protection device widely used in the world at present.
Characteristics of transient voltage suppression diodes.
1. Vmuri characteristics of one-way TVS.
The forward characteristic of unidirectional TVS is the same as that of ordinary Zener diodes, and the reverse breakdown inflection point is a hard breakdown, which is a typical PN junction avalanche device. The curve segment from the breakdown point to the VC value shows that when there is an instantaneous overvoltage pulse, the current of the device increases rapidly and the reverse voltage rises to the clamp voltage and remains at this level.
2. Vmuri characteristics of bi-directional TVS.
The Vmuri I characteristic curve of bi-directional TVS is like a combination of two unidirectional TVS "back to back". It has the same avalanche breakdown and clamping characteristics in both directions. The symmetry relationship between positive and negative breakdown voltage is: 0.9 ≤ V (BR) (positive) / V (BR) (inverse) ≤ 1.1. as soon as the interference voltage at both ends exceeds the clamping voltage VC, it will be suppressed immediately. The application of bi-directional TVS in AC circuit is very convenient.
Main parameters of transient voltage suppression diodes.
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 clamping voltage VC (MAX) is the maximum 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.
3. Maximum reverse working voltage VRWM (or modified voltage).
When the device works in reverse, under the specified IR, the voltage at both ends of the device is called the maximum reverse working voltage VRWM. Usually VRWM= (0.8-0.9) V (BR). At this voltage, the power consumption of the device is very small. When in use, the VRWM should not be lower than the normal working voltage of the protected device or line.
Selection principle of transient Voltage suppression Diode.
When choosing TVS, we must consider the specific conditions of the circuit, and generally follow the following principles:
1. The large clamp voltage VC (MAX) is not greater than the maximum allowable safety voltage of the circuit.
Second, the maximum reverse working voltage (modification voltage) VRWM is not lower than the maximum working voltage of the circuit, generally, VRWM is equal to or slightly higher than the maximum working voltage of the circuit.
Third, the rated maximum pulse power must be greater than the maximum transient surge power in the circuit.
Application of transient Voltage suppression Diode.
Transient voltage suppression diodes have been widely used in computer systems, communication equipment, AC / DC power supplies, automobiles, electronic ballasts, household appliances, instruments (watt-hour meters), 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.