The Advantages and Disadvantages of Triac Dimmable LED Driver

- Sep 24, 2018-

With the progress of LED technology, there are many dimming modes for LED illumination, Triac LED dimmable driver is one of them. Compared with other dimming modes, Triac dimmable LED driver has its special advantages and disadvantages.
The common incandescent, halogen lamps are often controlled by Triac dimmable LED driver. They has no requirement on the input voltage. Just only changing the valid values of input voltage, it is very easy for Triac LED dimmable driver to dim them.
The Triac LED dimmable driver is an ideal device to use for AC switching applications because it can control the current flow over both halves of an alternating cycle. A thyristor is only able to control them over one half of a cycle. During the remaining half no conduction occurs and accordingly only half the waveform can be utilised.


The fact that the Triac LED dimmable driver can be used to control current switching on both halves of an alternating waveform allows much better power utilisation. However the TRIAC is not always as convenient for some high power applications where its switching is more difficult.
The Triac LED dimmable driver is a component that is effectively based on the thyristor. It provides AC switching for electrical systems. Like the thyristor, the TRIACs are used in many electrical switching applications. They find particular use for circuits in light dimmers, etc., where they enable both halves of the AC cycle to be used. This makes them more efficient in terms of the usage of the power available. While it is possible to use two thyristors back to back, this is not always cost effective for low cost and relatively low power applications.
It is possible to view the operation of a TRIAC in terms of two thyristors placed back to back.


One of the drawbacks of the Triac LED dimmable driver is that it does not switch symmetrically. It will often have an offset, switching at different gate voltages for each half of the cycle. This creates additional harmonics which is not good for EMC performance and also provides an imbalance in the system.
In order to improve the switching of the current waveform and ensure it is more symmetrical is to use a device external to the Triac dimmable LED driver to time the triggering pulse. A DIAC placed in series with the gate is the normal method of achieving this.
When requiring to switch both halves of an AC waveform there are two options that are normally considered. One is to use a Triac dimmable LED driver, and the other is to use two thyristors connected back to back - one thyristor is used to switch one half of the cycle and the second connected in the reverse direction operates on the other half cycle.
As there are two options the advantages and disadvantages of using a Triac dimmable led driver must be weighed up.


Despite what may seem like a number of disadvantages, it is still the best option for many circumstances. However when using a Triac dimmable led driver, 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.