Electronics > Projects, Designs, and Technical Stuff
Designing a 48VDC to 30VDC 3A isolated power supply
Decee1:
Hello.
I'm working on a project where i got 48VDC and i want to isolate it and step it down to 30V @ 3A
I've been looking for a IC that can do it with opto isolation but no luck.
I'v also made a PCB based on my theory of functionality which turned out to not work. Diagram attached so i can get shamed on.. There is some additional circuit behind the opto circuit I've designed but cut out of the picture. The TPS54361 circuit is a modified version of a recommendation from TI's WEBENCH.
So now I'm asking on the forum.. Anyone had experience with isolated DC-DC designs?
The ideal way to go would of-course to just do a 230v to 30V @ 3A but i don't want to play around with mains.. I don't have a deathwish ;D
Decee1:
Here is a picture of my simulation. It is just a proof of concept and not optimized at all
Inductor is 1:3 which was the value i came up with though the recommended inductor for the TPS DC-DC converter and then i just trimmed the inductor until it gave me more than 30V on the output when i had a 10 ohm load at 30V aka over 3A load.
The generator thingie im using is just a simple ideal opamp and a comparator block i made for TI. The selected duty cycle is 40%
So in a nutshell
32V with 10 ohm load, 33uH PRI 99uH SEC, 100KHz Switching frequency and 40% duty cycle
TimNJ:
You should be able to use most offline flyback controllers to work with a lower input rail voltage. Just avoid controllers with baked in UVLO/brownout protection. You want one which allows you to adjust the parameters. Most offline controllers also have an integrated HV start feature. Usually these are current source driven, which means they can start-up consistently over a wide range of voltages. The only thing to consider is if there's a minimum start voltage on the HV pin. I've seen some which won't try to source current unless the voltage on HV is ~70V or so.
From a brief search, seems that UCC28740-Q1 might be an okay pick: https://www.ti.com/lit/ds/symlink/ucc28740-q1.pdf?ts=1597463696174&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FUCC28740-Q1
NiHaoMike:
--- Quote from: Decee1 on August 14, 2020, 07:16:57 pm ---The ideal way to go would of-course to just do a 230v to 30V @ 3A but i don't want to play around with mains.. I don't have a deathwish ;D
--- End quote ---
Have you considered a ready made module? Meanwell is fairly cheap but good quality, just beware of EMI.
coromonadalix:
You wont play with the main if you use a good psu ???
you convert a dc voltage to an lower one with isolation .... you will have some efficency losses, a 10v margin should compensate ...
and the Meanwell brand is very good, we use tons of them at my shop
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