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.