Transient-voltage-suppression diode

Suppressors also Transient absorption zener diode ( TAZ diode ) or Transient Voltage Suppressor diode ( TVS diode ) called, are components to protect electronic circuits against voltage pulses. In such cables connected to the circuit voltage pulses can occur by switching operations in the network or nearby lightning strikes. The short duration and voltage produced may be sufficient to destroy semiconductor devices in the circuit. Suppressor diodes become conductive when a voltage threshold is exceeded. The power of the pulse is discharged safely to ground. This means that no destructive tension can build up.

The breakdown voltage and the leakage current of the diode - except when an overvoltage event - ideally no effect on the circuit to be protected. The current-voltage characteristic and the structure similar to a zener diode. They differ mainly in the fact that Suppressors have a steeper curve at high currents. The tension is rising at very high currents even less than among Zener diodes. They have a higher discharge capacity compared with Zener diodes. As Suppressors Zener diodes are characterized by their short integration time in the range of nanoseconds. For use in AC circuits, there are also bipolar suppressor, which consist of against each other serially connected diodes, which behave independently of their polarity the same.

Suppressors are made for a number of close-tolerance breakdown voltages.

TVS diodes are available as SMT, through-hole components, as arrays or as a component with screw thread.

Typical component values

  • Peak power of ≈ 200-30000 W
  • Ligation time to 20 microseconds ( TVSD ), or up to 1000 microseconds (Power- TVSD )

Further characterizing component values ​​:

  • Leakage current (a few microamperes ) is the current at nominal threshold voltage, it should be as small as possible
  • Protection level is at a defined power ( e.g., 50 A) on the component voltage applied. He should be as little as possible about the protected voltage, the subsequent electronic circuit should tolerate this level.

Applications

TVS diodes are mainly used for the protection of sensitive components and signal inputs before one-time, temporary surges (transients ) as ESD events, disturbances used by switching operations or lightning storm. Occasionally, with them also induction surges, such as relay coils, against mass derived. Cause the diodes, as long as they are not destroyed by heat, as opposed to gas-filled surge arresters no voltage drop of the protected voltage and therefore after the response without power interruption for use.

As an alternative to Suppressors varistors are used especially at voltages from about 100V. However, these have a slightly longer response time and a higher protection level. In addition, there is the already mentioned gas arrester as coarse protection elements.

With unlimited surges as they can for example occur with defective power supplies, it overheats the TVS diode, mostly with thermal failure, whereby the surge protector is then omitted. To protect against unlimited surges called a clamping circuit is provided.

Unipolar Suppressors replace because of better properties and lower price increasing Zener diodes in the high power range and have this almost out of the market.

Brand name

TVS diodes are marketed by various semiconductor manufacturers under protected brand name. Some well-known brand names for TVS diodes are:

  • Transil - trademark of ST Microelectronics;
  • Transzorb - Brand Name Vishay (formerly General Semiconductor ).
  • Diode
  • Electromagnetic interference suppression
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