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I am currently testing a 5W LED bulb (direct operating on 230V AC) switching using a Triac BTA12-600B. I fed the signal from a microcontroller to an opto-triac coupler MOC3041. The LED bulb turns ON and OFF without any issues. Please note: I am using the LED only for ON/OFF purpose (no dimming).

Below is the working circuit.

without snubber

Now I add a snubber circuit in between just to protect my Triac in case of overvoltage. Below is the modified circuit

with snubber

Now comes one big issue:

The LED bulb flickers repeatedly, think at the rate of 50Hz or more. I am unaware of the internal circuitry the LED bulb has as it is enclosed in a retrofit case.

I feel, addition of snubber circuitry is causing the flicker because the LED bulb never flicker when I used the circuit without snubber.

Any reason why the LED flickers and its possible solution ?

Thanks in advance

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  • \$\begingroup\$ The problem is energy hold-up in the LED bulb, not your triac dimmer. You can't solve it with a snubber. \$\endgroup\$ – winny Oct 17 '16 at 7:42
  • \$\begingroup\$ Any idea how do i get rid of hold-up energy in LED bulb? \$\endgroup\$ – gaurav bhand Oct 17 '16 at 7:59
  • \$\begingroup\$ Get a bulb made för triac dimmers. \$\endgroup\$ – winny Oct 17 '16 at 8:02
  • \$\begingroup\$ ...and get a dimmer made for LED bulbs..and compatible with the specific type you have. It's a bit of a dog's breakfast I'm afraid. \$\endgroup\$ – Spehro Pefhany Oct 17 '16 at 9:48
  • \$\begingroup\$ Please note that I am not dimming the LED bulb. Only ON/OFF \$\endgroup\$ – gaurav bhand Oct 17 '16 at 9:58
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Your config seems a bit odd to me. You may try this one:

schematic

simulate this circuit – Schematic created using CircuitLab

Note that the snubber cap C1 may be 10n to 100nF.

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  • \$\begingroup\$ Thank you for reply. I will try the circuit you suggest and see if the issue gets resolved. \$\endgroup\$ – gaurav bhand Oct 17 '16 at 7:56
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Look at the specifications of the led bulb. Not all led bulbs have do have dimmable electronics. There are many different situations and it can be hard to tell you if it works or not.

Example. Some inmitation carbon thread led bulbs can be dimmed. Others have the strange behaviour of dimming partly or not at all. Somethimes they start to flicker.

Advise. Before buying a ledbulb you have to ask yourself the question if you want to use a dimmer or just on/off switching. Then select the bulb accordingly. A good store advisor should be able to inform you correctly.

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  • \$\begingroup\$ @ Decapod: I am using LED just for ON/OFF switching and not dimming. Yet i find flicker in LED when Traic is turned ON. \$\endgroup\$ – gaurav bhand Oct 17 '16 at 7:58
  • \$\begingroup\$ @gauravbhand Oh! That's a compleatly different issue! Please add this in your original question. You have too high hold-up current in your triac compared to your LED bulb consumption. Does it go away for now if you add more load in parallel? \$\endgroup\$ – winny Oct 17 '16 at 8:03
  • \$\begingroup\$ @winny: I didn't try with more loads. Will arrange for more such 2-3 LEDs and check. \$\endgroup\$ – gaurav bhand Oct 17 '16 at 8:11
  • \$\begingroup\$ @winny: With same Triaccirc uit, but without snubber, the LED does not flicker. The flickering started after i added snubber circuit. \$\endgroup\$ – gaurav bhand Oct 17 '16 at 8:19
  • \$\begingroup\$ @gauravbhand You could be right on the ridge/threshold of minimum triac current and slightly reshape the current waveform to push you over the limit to start the flickering. \$\endgroup\$ – winny Oct 17 '16 at 8:26

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