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Transient voltage suppression diode

 

 
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Transient voltage suppression diode
 
 
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A transient voltage suppression (TVS) diode is an electronic component
Electronic component

An electronic component is a basic Electronics element usually packaged in a discrete form with two or more connecting leads or metallic pads....
 used to protect sensitive electronics
Electronics

Electronics refers to the flow of charge through nonmetal electrical conductor , whereas electrical refers to the flow of charge through metal electrical conductor....
 from voltage spike
Voltage spike

In electrical engineering, spikes are fast, short duration electrical transient s in voltage , current , or transferred energy in an electrical circuit....
s induced on connected wires. It is also commonly referred to as a transorb, after the brand name TranZorb registered by General Semiconductor (now part of ).






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Transient Voltage Suppression Diode Symbol
A transient voltage suppression (TVS) diode is an electronic component
Electronic component

An electronic component is a basic Electronics element usually packaged in a discrete form with two or more connecting leads or metallic pads....
 used to protect sensitive electronics
Electronics

Electronics refers to the flow of charge through nonmetal electrical conductor , whereas electrical refers to the flow of charge through metal electrical conductor....
 from voltage spike
Voltage spike

In electrical engineering, spikes are fast, short duration electrical transient s in voltage , current , or transferred energy in an electrical circuit....
s induced on connected wires. It is also commonly referred to as a transorb, after the brand name TranZorb registered by General Semiconductor (now part of ). STMicroelectronics
STMicroelectronics

STMicroelectronics is an Italy-France electronics and semiconductor manufacturer headquartered in Geneva, Switzerland.While STMicroelectronics corporate headquarters and the headquarters for Europe and emerging markets, are based in Geneva, the holding company, STMicroelectronics N.V....
 sells them under the name Transil. The name Tranzil can also be seen.

The device operates by shunting excess current when the induced voltage exceeds the avalanche breakdown
Avalanche breakdown

Avalanche breakdown is a phenomenon that can occur in both Electrical insulation and Semiconductor materials. It is a form of electric current multiplication that can allow very large currents to flow within materials which are otherwise good insulators....
 potential. It is a clamping
Clamp (circuit)

A clamp or clamp circuit is an electrical circuit used to prevent another circuit from exceeding a certain predetermined voltage level. It operates by sensing the output voltage of the monitored circuit and then as the output voltage approaches the preset limit, applies an electric load which draws greater and greater current from the...
 device, suppressing all overvoltages above its breakdown voltage. Like all clamping devices, it automatically resets when the overvoltage goes away, but absorbs much more of the transient energy internally than a similarly rated crowbar
Crowbar (circuit)

A crowbar circuit is an electrical circuit used to prevent an overvoltage condition of a power supply unit from damaging the circuits attached to the power supply....
 device.

A transient voltage suppression diode may be either unidirectional or bidirectional. A unidirectional device operates as a rectifier
Rectifier

A rectifier is an electrical device that converts alternating current to direct current , a process known as rectification. Rectifiers have many uses including as components of power supply and as detector s of radio signals....
 in the forward direction like any other avalanche diode
Avalanche diode

An avalanche diode is a diode that is designed to go through avalanche breakdown at a specified reverse bias voltage and conduct as a type of voltage reference....
, but is made and tested to handle very large peak currents. (The popular 1.5KE series allows 1500 W of peak power, for a short time.)

A bidirectional transient voltage suppression diode can be represented by two mutually opposing avalanche diode
Avalanche diode

An avalanche diode is a diode that is designed to go through avalanche breakdown at a specified reverse bias voltage and conduct as a type of voltage reference....
s in series with one another and connected in parallel with the circuit to be protected. While this representation is schematically accurate, physically the devices are now manufactured as a single component.

A transient voltage suppression diode can respond to over-voltages faster than other common over-voltage protection components such as varistor
Varistor

A varistor is an electronic component with a significant non-Ohm current?voltage characteristic. The name is a portmanteau of resistor#Variable resistors....
s or gas discharge tubes. The actual clamping occurs in roughly one picosecond, but in a practical circuit the inductance
Inductance

Inductance is the property in an electrical circuit where a change in the current flowing through that circuit induces an Electromotive force that opposes the change in current ....
 of the wires leading to the device imposes a higher limit. This makes transient voltage suppression diodes useful for protection against very fast and often damaging voltage transients. These fast over-voltage transients are present on all distribution networks and can be caused by either internal or external events, such as lightning or motor arcing.

Characterization

A TVS diode is characterised by:
  • Leakage current: the amount of current conducted when voltage applied is below the Maximum Reverse Standoff Voltage.
  • Maximum Reverse Standoff Voltage:: the voltage below which no significant conduction occurs.
  • Breakdown voltage: the voltage at which some specified and significant conduction occurs, typically1 mA.
  • Clamping voltage: the voltage at which the device will conduct its fully rated current (hundreds to thousands of ampere
    Ampere

    The ampere is the International System of Units unit of electric current. The ampere, in practice often shortened to amp, is an SI base unit, and is named after Andr?-Marie Amp?re, one of the main discoverers of electromagnetism....
    s).
  • Parasitic capacitance: The nonconducting diode behaves like a capacitor
    Capacitor

    A capacitor or condenser is a Passive component electronic component consisting of a pair of electrical conductor separated by a dielectric....
    , which can have a deleterious effect on high-speed signals. Lower capacitance is generally preferred.
  • Parasitic inductance: Because the actual overvoltage switching is so fast, the package inductance is the limiting factor for response speed.
  • Amount of energy it can absorb: Because the transients are so brief, all of the energy is initially stored internally as heat; a heat sink
    Heat sink

    A heat sink is an environment or object that absorbs and dissipates heat from another object using thermal contact . Heat sinks are used in a wide range of applications wherever efficient heat dissipation is required; major examples include refrigeration, heat engines, Thermal management of electronic devices and systems and lasers....
     only affects the time to cool down afterward. Thus, a high-energy TVS must be physically large. If this capacity is too small, the overvoltage will possibly destroy the device and leave the circuit unprotected.


See also

  • Transient voltage suppressor
  • Varistor
    Varistor

    A varistor is an electronic component with a significant non-Ohm current?voltage characteristic. The name is a portmanteau of resistor#Variable resistors....