"Triac": It is developed on the basis of ordinary thyristors. It can not only replace two thyristors connected in parallel with opposite polarity, but also requires only one trigger circuit, which is an ideal AC switching device. . Its English name TRIAC means three-terminal two-way AC switch.
1.What is a triac
A P1N1P2N2 four-layer three-terminal device with silicon single crystal as the basic material was created in 1957. Because its characteristics are similar to vacuum thyristors, it is commonly known as silicon thyristor internationally, or thyristor T for short. And because the thyristor was originally used in the controllable rectifier, it is also called the silicon controlled rectifier element, referred to as the thyristor SCR.
In terms of performance, thyristor not only has unidirectional conductivity, but also has more valuable controllability than silicon rectifier components (commonly known as "dead silicon"). It has only two states of on and off.
The thyristor can control high-power electromechanical equipment with milliampere current. If the frequency exceeds this frequency, the switching loss of the components will increase significantly and the average current allowed to pass will decrease. At this time, the nominal current should be degraded.
There are many advantages of thyristor, such as: controlling high power with low power, the power amplification is as high as hundreds of thousands of times; the response is extremely fast, turning on and off in microseconds; contactless operation, no spark, no noise; High efficiency, low cost and so on.
Weaknesses of thyristor: poor static and dynamic overload capacity; easy to be misled by interference.
2.Triac application
At present, the application market of thyristor is quite broad, and thyristor is used in the field of automatic control, electromechanical field, industrial electrical appliances and household appliances. More importantly, the application of thyristor is quite stable, such as electronic switches used in home appliances, which can be said to be rarely changed. No matter how other components change, the change of thyristor is not big, which is equivalent to expanding the application market of thyristor and reduces the risk of investment. With the hot sales of consumer electronic products, more thyristor has provided sales space. Introduced two new standard triacs that optimize the performance of consumer electronic products. These two triacs are designed with advanced planar silicon structure, which have high reliability and On-state losses are only 1.5V at most, resulting in high efficiency. Target application areas for both products include: washing machines, vacuum cleaners, dimmers, remote switches and AC motor control devices.
The internal circuit of the zero-crossing trigger type AC solid state relay (AC-SSR). It mainly includes input circuit, optocoupler, zero-crossing trigger circuit, switch circuit (including triac), and protection circuit (RC absorption network). When the input signal VI (generally high level) is added, and the AC load power supply voltage passes through the zero point, the triac is triggered to turn on the load power supply. Solid state relays have the advantages of low driving power, no contact, low noise, strong anti-interference ability, short pull-in and release time, long life, compatible with TTL\CMOS circuits, and can replace traditional electromagnetic relays.
Triac can be widely used in industry, transportation, household appliances and other fields to realize various functions such as AC voltage regulation, motor speed regulation, AC switch, automatic opening and closing of street lamps, temperature control, table lamp dimming, stage dimming, etc. It is also used in solid state relay (SSR) and solid state contactor circuits.