The TRIAC is a three terminal semiconductor device for controlling current. It gains its name from the term TRIode for Alternating Current.
The TRIAC is an ideal bidirectional device to use for AC switching applications because it can control the current flow over both halves of an alternating cycle.
TRIACs' bidirectionality makes them convenient switches for alternating-current (AC). In addition, applying a trigger at a controlled phase angle of the AC in the main circuit allows control of the average current flowing into a load (phase control). This is commonly used for controlling the speed of induction motors, dimming lamps, and controlling electric heaters.
Moreover, the fact that the TRIAC can be used to control current switching on both halves of an alternating waveform allows much better power utilization. However the TRIAC is not always as convenient for some high power applications where its switching is more difficult.
● Can switch both halves of an AC waveform
● Single component can be used for full AC switching
● A TRIAC does not fire symmetrically on both sides of the waveform
● More susceptible to EMI problems as a result of the non-symmetrical switching
Despite what may seem like several disadvantages, it is still the best option for many circumstances. However when using a TRIAC, it is necessary to be aware of its limitations so that these can be satisfactorily addressed and overcome should they affect the operation of the overall circuit in any significant way.