Noise Problem regarding TRIAC DIMMING

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I am trying to build a 30W LED Driver with Triac dimming feature.Its performing fine when firing angle is set to zero.But when i start to increase the firing angle, some noise starts coming. Most probably noise comes from the triac circuit. May be its becuase of the distortion of input current. i have tried to tune damping resistor as well as bleeder cappacitor. Bur still that noise persists.I am using LNK410EG. Please give some suggestion to sort out this problem.





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If you are using leading-edge triac dimmer, then you can hear audible noise from the triac dimmer, thus you should put it a little further if you are checking audible noise of the LED driver.

Other components may cause audible noise such as the EMI filter and transformer. Varnish the transformer to minimize noise coming from it.

Reduce the value of C2 and C4, if EMI and dimming performance allows because large values will draw higher inrush current every time the triac turns ON. You may also need to increase the current rating of your EMI inductors. If the inrush current is high, it could exceed inductor rating and if it saturate, it will cause high audible noise. 

If you can pot the whole driver, then noise can be minimize as well.



Thanks for your reply.Do you mean that anyway that audible noise will come from leading edge triac dimmer? and is it possible to use a trailing edge triac dimmer with rest of design remaing same?

We typically consider both leading-edge and trailing-edge dimmers when designing the LED driver and you should verify the design on both dimmers in order to be compatible with wider range of dimmers.


Audible noise is much worse in leading-edge than in trailing-edge dimmer. You can verify that on your setup.

Please compare the peak input current between these two types.