Boundary conduction mode LED driver problem

[ocset]

Hi,
Why do virtually all offline LED driver IC’s involve the Boundary Conduction Mode  (BCM) principle? (AKA critical conduction mode)  It certainly has advantages, but the one huge disadvantage is that you can’t dim them down to low light levels without the switching  frequency getting ridiculously high. It’s possible to avoid this by making them with a minimum off time, but virtually none of these BCM led dirver chips have this facility.
So why is this?
LED driver datasheet (NCL30002)
https://www.onsemi.com/pub/Collateral/NCL30002-D.PDF

[Giaime]

Why do virtually all offline LED driver IC’s involve the Boundary Conduction Mode  (BCM) principle?

Because it's zero voltage switching in theory, thus reducing losses. Very few in the industry are concerned about dimming to less than 10% or so.
If you need better dimming, it's best to go to a two-stage principle, maybe with a pulse-skipping PFC front-end to avoid going too high with switching frequency.