lnk407eg dimmable

Hi,

The transformer should be varnished to avoid audible noise coming from the transformer. Other souurce of audible noise is the line filter inductors. During dimming where high peak input current is present, the line inductors could saturate if not properly designed which results to buzzing sound. The farther the inductors from saturation (bigger inductors), the less the audible noise.

The flickering problem can be addressed by the active damper and passive bleeder (series RC). I cannot see clearly your schematic so I cant give you the circuit reference. Make sure that the active damper is working correctly. The purpose of the damper is the reduce the ringing of the input current during dimming. The RC bleeder provides latching current for the TRIAC and also provides damping. These two circuits must be tuned to prevent flickering.

Thanks for your help. I will consider all your suggestions and I will do post my result in here.Again, thanks...It helps me a lot.

 Is it normal that the passive bleeder resistor will got so hot about 70 degree celcius. the case makes it so hot.

Any solution to lessen the heat on the resistor?

Resistor value = 220 ohms

capacitor value = 220 nF (204)

Please, help me. I need this sample for Monday presentation.

It depends on the power rating of the resistor you used. Measure the power dissipation of this resistor and use 50% power derating to keep temperature manageable.

You can also reduced the value of the series capacitor to reduce dissipation on the resistor, however this will reduce compatibility with dimmers. Normally, if space permits it, just use a higher power resistor that will give you passing thermals.

Thanks to your prompt reply.

I already got it work. I have 81% efficiency,14.6 input watts and temperature is tolerable. I am using EF2525 transformer(varnished). I am using MKP X2 capacitor on the input stage and passive bleeder.

My problem is I still got a little buzz on the transformer and on the capacitors when the triac dimming device is in between lowest and highest position. It would be more better if I can eliminate this noise.

Another problem is the flicker, this is not the visible flicker I have before. This flicker can only be seen using a camera from any mobile phone or smart phone. One of my customer shown me that there is a flicker using the camera with in the range of 1 meter. More flicker can be seen if the camera is near the LED luminaire.The flicker can't be seen more than 1 meter away from the LED luminaire.  

I highly appreciate your help.

Again, thank you.

The flicker seen by the camera is caused by the 100/120Hz ripple on the output current. You can try to reduced it by reducing the ripple by increasing the output capacitors. If you want to totally eliminate it, the output current should approach pure dc value with zero low frequency ripple. 

The transformer noise  can be reduced by varnished or redesigning it to operate at lower flux density.