As you might know, LED lamps over 25W require a minimum 0.9 power factor in Europe.
I have designed a PSU for a specific LED lamp which is rated about 50W. There is a PFC-stage (crm) in order to achieve a high PF. However, if I reduce the load to 25W (input) by dimming the light, the pf will be below this value (0.85 - 0.87) for 230VAC. For 264VAC, there is not even a chance to come close (below 0.8).
Now the question is, has the power factor requirement of the lamp to be fulfilled for the nominal rating or also for different loads (dim level)?
I have checked some datasheets of 50W LED drivers which would not achieve 0.9 pf at 25W load although they have a build-in active pfc function. At nominal load, there is no issue. I have also checked a UCC28051 TI Eval Board with same issue (0.87 at about 25W):- datasheet, See Table 5 in Chapter 6.1.1.
If the requirement has to be fulfilled for different dim levels as well, how is it possible to achieve this with a standard pfc? What about 265VAC?