LNK 406EG Dimming range issue

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We have built up several iterations of the 500 mA /28V LED driver design using the LNK 406 as per RDR194.

The non dimming units perform extremely well, our problem is with the triac dimming unit, the dimming range is very poor. At max output we are getting exactly 500mA but when fully dimmed we are still getting 109mA which still represents quite a bright light.

Where do we start looking? Once it is possible to dim down lower, will the unit restart from a very low dimmed point? a factor that is important in marketing.

The dimming range with LinkSwitch-PH depends on the characteristic of a triac itself.

If the minimum phase angle of a triac dimmer is high (> 60 deg), the dimming range will be low.

But if the mimum phase angle is low, (< 45 deg), the dimming range will be high.

Also there will be a bandgap between turn off and turn on levels with triac dimming application.

Thanks very much for that, I will get hold of some different triac units and see how we go. Your help is appreciated.