Linkswitch PH dimming range ISSUES

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Hi again,

We have used your Linkswitch PH ICs on a number of designs. Previously we had a issue which we had to solve with our own external technology (flicker with digital dimming caused by the fundamental mains frequency), but now on a different design/ product range we have encountered a different issue which I will try to explain here.

Looking at all your triac dimmable reference designs and application notes we can see many dimmers have been tested from all around the world. As a engineer the testing stacks up, but in reality there are real world issues with how it operates.

Firstly, the dimming curve does not match current technology. We used to sell up-to 150,000pcs of halogen dimmers every month for over 10 years, we have an existing install base and these people would like to upgrade to a suitable LED product. I can grab almost any halogen driver and lamp combination with any dimmer and they almost work identically. Different dimmers will work a little different but in general they are all similar. Using the Linkswitch PH we find that adding the LED product the dimming range is different and effectively not in sync ( i.e they have different dimming curves).

Secondly, most of your testing (for example der314)shows that most dimmers will only dim to around 20%, except for some cheaper Chinese dimmers. 20% is still a very high lighting level and is not good enough to operate along side the existing market.

The issue I see is the the dimming curve needs to be remapped internally inside the linkswitch PH to account for the above problems and improve overall compatibility with the current market (it is the same world wide). Currently with the limited range of dimming due to the design of most dimmers in most markets the linkswitch PH is not a good option. Other manufactures are doing this already, so I don't know why this has not already been solved with the PH.

I would like to take this issue further and would love to liaise with Paul Lacey of someone that has direct input into this issue and future PH designs

Your help and response in this matter would be appreciated.


Thanks for your input and concern.

We have worked on improvement of LinkSwitch-PH performances, specially triac dimming issues as you mentioned.

Thank you again.

Thanks for your reply PI-Skywalker.

Are you able to give any more details regarding the upgrades in performance? or when something will be published?

One of our engineers solved some problems by dimming it with a different method. It used 3 extra parts but should bring it inline with halogen products. I just don't know which method I should use until I know PI's plans


I am sorry, but I can not say anything about our new product until it is available in public.

There will be a public announcement when it is ready.