PSU topology question for LEDs

I've been on a mission the past few days to decide on a power supply design for a UV LED bar I want to make but it hasn't been as straight forward as I expected it to be. Initially my goal was to design an isolated switcher, unfortunately after looking at nearly every datasheet on Digikey and Mouser I was unable to find an acceptable transformer. My two main restrictions are physical size and power capabilities. The way I have it envisioned at the moment I will need about 24-30V at 3.5-4A, however the space I'm dealing with will not accommodate a traditional 50/60Hz stepdown transformer and none of the high frequency transformers for smps I found were capable of supplying both my voltage and current requirements.

I'm starting to consider a transformer-less design now despite it not being my preference but my knowledge of PSUs isn't up to where I'd like it to be yet. I need to figure out how to get the power as efficiently as possible with a small footprint. I've got 36 inches of length to work with but only about 1.5 inches squared for height and width. This is also why I'm looking for efficiency because the confined area is already almost entirely devoted to heatsinking 70W from the LEDs.

The idea I'm looking into now essentially consists of rectifying mains voltage and then using a buck converter to step down the voltage to what I need, however I'm also intending on powering a microcontroller with this as well. I'm playing around with the idea of making it DMX controllable I guess my question is what are the design issues I should be concerned with (or is it even practical)? I'm sure I can limit the voltage ripple enough with caps and a linear regulator that it won't bother the microcontroller but I'm just not familiar with the limitations of buck converters (as far as input voltages are concerned). I will likely need two, one to step down the rectified mains voltage to 24-30V for the LEDs and then a second to step down the 24-30V to 5V for the controller I'm also not sure what effect a second converter might have on the first or vice versa.

Any insight is appreciated and if anyone has any suggestions on other methods of power delivery I would be interested in hearing them as well. I really wish I had one of the American DJ UV bars to tear apart. I'd like to know how they fit their power converter in such a tight spot. Perhaps I've just been trying to over design this and in reality I should just keep it as bare bones as possible.

:cat:
@"the confined area is already almost entirely devoted to heatsinking 70W from the LEDs. "

Maybe best, not to screw up this rather important task, by bunging in a load of extra heat, and taking up all the space.
IMHO better to keep the PSU separate and use this space for control only (perhaps a large capacitor to avoid power line surge issues).
This would also allow you to use "off the shelf SMode PSUs" and "buck modules" with a more "conventional" shape.>:)

Cheers :)

Yes, that was definitely considered. I use external PSUs for my other black lights but this one is going to be intended for outdoor use and I'm trying to keep it as weatherproof as possible. An external supply won't hold up as well in the elements and I don't like the idea of an exposed DC jack. However, That did get me to thinking that the supplies I have been using are quite small (laptop style converters) and I still get 24V 3A from them. I don't know why I didn't think of it sooner but I may just crack one open and see what's going on inside. height wise they would work so I could probably just rearrange components to narrow it down some. Thanks for sparking my memory :D

:cat:
Sounds OK for winter months ...but Summer evenings ? *vigil
Cheers :)

That's why I'm trying to keep the PSU as efficient as possible to limit excessive hear, however the whole frame is going to be made from a hefty chunk of aluminum with plenty of exposure to ambient air. I think it will be fine as long as the most inefficient components are the LEDs.

I would suggest a commercial driver such as the meanwell HLG series with the dimming function get the IP67 rated driver. I use these as well as cheap aliexpress drivers for my COB leds. It is not worth your time or money to build them on your own, which was my original plan.