Suitable Triac

[Suraj143]

I want to drive a domestic light bulb (AC 230V/50Hz) via a triac.But I can supply very limited gate current.Probabaly a sensistive gate triac will help.
I planned to use TIC206D triac.

The problem is now the domestic bulbs (specially LED) consists with capacitive supplies or some high current drivers with a built in chopper transformers.
Will the above triac suits for my application?

 

[alec_t]

Some of the non-incandescent bulbs are rated as dimmable and some aren't. What type do you have? It is important NOT to use a dimmer on a non-dimmable CFL.

 

[dr pepper]

As alec says you have to use a dimmable lamp, ones that do not dim will pull lots of current as the fast rising edges of the phase controlled pulses are effectively shorted by the lamps smoothing cap, you can actually make the smoothing cap blow up with this.
On the other hand if you are just turning the lamp on/off instead of dimming you could use a zero crossing opto coupler or other zero crossing techniques and that would most likely work.

 

[Nigel Goodwin]

Some of the non-incandescent bulbs are rated as dimmable and some aren't. What type do you have? It is important NOT to use a dimmer on a non-dimmable CFL.

By 'some' you mean the vast majority of LED bulbs aren't dimmable, and CCFL have never been dimmable in this way.


If the OP wants to use normal TRIAC dimmers on LED lamps, then he needs specific dimmable types, but even then should be aware they don't dim as well as incandescent bulbs.

 

[Suraj143]

No.I'm not dimming the bulb.I just want to ON/OFF. The circuit I'm using for any bulb.it can be Capacitive driven Led lamps, Led driver type lamps, CFL lamps etc....

 

[alec_t]

But I can supply very limited gate current

What is that, in mA? Depending on the triggering quadrant, that triac needs a gate current which could be as much as 5mA or 10mA, according to its datasheet.

 

[Suraj143]

Yup you are correct.I can supply only 5mA of gate current.

 

[schmitt trigger]

If you provide a webpage link or a datasheet for the Triac part number, we can tell you where to look for the exact information you require.

 

[Suraj143]

I have attached the datasheet of the TIC206D triac. I'm sure that it needs very low gate current which can deliver from my circuit.

But that's not the problem.The problem is Does this Triac durable for capacitive loads or inductive loads? Such as capacitive LED lamps & driver driven LED lamps, CFL lamps etc?

 

[schmitt trigger]

The answer is there on the datasheet:

RATING -------------------------------------------------- SYMBOL----VALUE---UNIT
Peak on-state surge current full-sine-wave (see Note 3)......ITSM.............25........A

And then:
Note 3. This value applies for one 50-Hz full-sine-wave when the device is operating at (or below) the rated value of on-state current.
Surge may be repeated after the device has returned to original thermal equilibrium. During the surge, gate control may be lost.

 

[Suraj143]

Hi thats nice.That means I can use the above triac for such loads.

Even furthur If I tun ON the triac when zero cross position will it be too good for reliability of the triac & device?

 

[Nigel Goodwin]

Hi thats nice.That means I can use the above triac for such loads.

Even furthur If I tun ON the triac when zero cross position will it be too good for reliability of the triac & device?

Using zero-crossing is good for the TRIAC, and good for low RFI as well - everyone will love you!

 

[tcmtech]

Yup you are correct.I can supply only 5mA of gate current.

Is your driving source capable of and or designed for triggering a triac to begin with? Most power triacs use a bidirectional current triggering on their gates which means every half cycle is triggered as a polar opposite to a normal SCR by drawing current out of the gate instead of putting it in.

Also there can be an issue of control circuit isolation or integration with the AC line that the triac is part of. Personally I prefer using s low current optoisolator triac driver IC for triggering larger power triacs since they solve both the possible trigging current polarity and the possible circuit isolation issues.

 

[Suraj143]

Hi I don't know about triacs much.I just give a 5V continuous signal to its gate from a microcontroller. Is there any other way to trigger a triac?