Transil, Trisil and SIDAC
Transil is the trade name of Transient Voltage Suppression diode or TVS diode of ST
Microelectronics, Transil diode is used to protect sensitive electronic devices from voltage
spikes and transients induced by the mains. Transil protects the circuit by shunting excess
current if the induced current exceeds the avalanche breakdown point. It works like a clamping
diode to remove all the excess voltage induced. When the overvoltage condition goes off, the
Transil automatically resets. Trisil is the trade name of the Thyristor Surge Protection device,
another surge protector for electronic equipments. SIDAC is also a protection device less
commonly used for surge protection for AC.
The Transil may be either Unidirectional or Bidirectional. The Unidirectional diode functions
like a rectifier diode conducting only in the forward direction but can handle very high peak
current around 1500 watts for short time. The Bidirectional Transil has two avalanche diodes
arranged in opposite directions for two way conduction. The two diodes are arranged in series
with each other and connected parallel to the device to be protected. The Transil can handle very
high current and is more efficient than other surge protectors like Varistor, Gas Discharge
Device (GDS).The Clamping takes place less than one picoseconds so that its operation is very
fast. These devises are very good for protection especially in areas with frequent power
transients and lightning.
Trisil act as a Cow bar device switches on when the voltage exceeds its break over voltage. It is
a bidirectional device conducting in both the directions. In structure, it is similar to a Triac
without a gate. Trisil works very fast and can handle large currents. Trisil is used widely in
Telecommunication devices to protect the Telephony system from lighting induced transients
and surge from power lines.
SIDAC is also a protection device less commonly used for surge protection for AC.SIDAC is the
Silicon Diode for Alternating Current having very high current rating and fast response.
SIDAC is also known as SYDAC (Silicon thYristor for Alternating Current).In structure,
SIDAC is a bidirectional device formed of bidirectional Thyristor diodes and technically
specified as a bilateral voltage triggered switch. The working of SIDAC is similar to a DIAC
used as pulse generators in Triac controlled devices. It is similar to a Triac without gate and is a
five layered device. Since the SIDAC handles much current, it can be used to switch on a device
and not like the triggering in DIAC.
SIDAC functions like a Spark Gap and remains non conducting until the voltage exceeds its
specified rated voltage. Once entering into the conducting mode, it conducts current even if the
input voltage reduces. Once the voltage drops below the breakdown voltage, it resets into the non
conducting state.