Trisil is a trade name for a

thyristor A thyristor () is a solid-state semiconductor device with four layers of alternating P- and N-type materials used for high-power applications. It acts exclusively as a bistable switch (or a latch), conducting when the gate receives a current ...

surge protection device, an electronic component designed to protect electronic circuits against

overvoltage When the voltage in a circuit or part of it is raised above its upper design limit, this is known as overvoltage. The conditions may be hazardous. Depending on its duration, the overvoltage event can be transient—a voltage spike—or perm ...

. Unlike a

transient voltage suppression diode A transient-voltage-suppression (TVS) diode, also transil or thyrector, is an electronic component used to protect electronics from voltage spikes induced on connected wires. Description The device operates by shunting excess current when the ...

s, such as Transil, a Trisil acts as a crowbar device, switching ON when the voltage on it exceeds its breakover voltage.

Overview

A Trisil is bidirectional, behaving the same way in both directions. It is principally a voltage-controlled

triac A TRIAC (triode for alternating current; also bidirectional triode thyristor or bilateral triode thyristor) is a three terminal electronic component that conducts current in either direction when triggered. The term TRIAC is a genericised tradem ...

without gate. The behavior of a Trisil is similar to a SIDAC, but unlike SIDAC, Trisil devices are commonly used to protect circuits from overvoltage. They act faster and can handle more current. In 1982, the only manufacturer was

Thomson SA Thomson may refer to: Names * Thomson (surname), a list of people with this name and a description of its origin * Thomson baronets, four baronetcies created for persons with the surname Thomson Businesses and organizations * SGS-Thomson M ...

; a successor company,

ST Microelectronics STMicroelectronics N.V. commonly referred as ST or STMicro is a Dutch multinational corporation and technology company of French-Italian origin headquartered in Plan-les-Ouates near Geneva, Switzerland and listed on the French stock market. ST ...

continues to make the devices. This type of crowbar protector is widely used for protecting telecom equipment from lightning-induced transients and induced currents from power lines. Other manufacturers of this type of device include Bourns (TISP) and

Littelfuse Littelfuse, Inc is an American electronic manufacturing company headquartered in Chicago, Illinois. The company primarily produces circuit protection products but also manufactures a variety of electronic switches and automotive sensors. Littelfus ...

(SIDACtor). Rather than using the natural breakdown voltage of the device, an extra region is fabricated within the device to form a

Zener diode A Zener diode is a special type of diode designed to reliably allow current to flow "backwards" (inverted polarity) when a certain set reverse voltage, known as the ''Zener voltage'', is reached. Zener diodes are manufactured with a great var ...

. This allows a much tighter control of the breakdown voltage. It is also possible to make gated versions of this type of protector. In this case, the gate is connected to the telecom circuit power supply (via a diode or transistor) so that the device will crowbar if the transient exceeds the power supply voltage. The main advantage of this configuration is that the protection voltage tracks the power supply, thus eliminating the problem of selecting a particular breakdown voltage for the protection circuit.

References

External links

Overvoltage protection

''Trisil/Transil Comparison'', ST Application Note (PDF)
Solid state switches Voltage stability {{electronics-stub

Overview

See also

References

External links