Electronics > Projects, Designs, and Technical Stuff
Isolated 5V 5-10ma supply
(1/6) > >>
ali_asadzadeh:
Hi,
I need to have 16 channel, isolated 5V 5-10ma supply, what's the cheapest solution to do that?
any Ideas? the input can be flexible,like 12V or 5V or 3.3V, the design should be small efficient and cheap, I was thinking about using EFD15 ferrite core with a 10 pin bobbin and generating 3-4 channel isolated voltage on each transformer, But I think maybe we have something better and smaller.
David Hess:
A flyback switching regulator with multiple output windings is one way.  Better I think is to use a square wave inverter because then current is continuous allowing for a smaller transformer and lower noise.  If the lowest noise is required, then a sine wave inverter can be used with the associated loss of efficiency.
ali_asadzadeh:
Since the output current is so small, I was thinking of a simple circuit with open loop, and use low cost post LDO's to regulate the outputs. in this way maybe I could save one aux winding and add one more output.
TurboTom:
Isolation requirements? Capacitive coupling? Depending on the application, there are many options. I once played with the idea to use the smallest available mains-rated symmetric common mode chokes with a common exciter to provide a multitude of well-isolated outputs. The sensitivity of the application required a sine drive and as little stray capacitance as possible. A few quick-and-dirty proof of concept tests showed this approach to be quite promising but since the expense of the PSU was of little importance, finally the decision was reached to use off-the-shelf DC/DC converters (which coused their own, different problems...of course  ::)).

If you plan to follow this road, please be aware that the exciter has to be perfectly symmetric (capacitive coupling) to avoid core saturation (there is no air gap in the ferrite cores) and that the secondary rectifier also has to provide a symmetrical load (full bridge or voltage doubler). Otherwise, this concept works really well and requires little post-regulation since it's a pure forward converter with good output voltage stability. If a single exciter is going to be used for all channels, it's good practice to use an individual DC blocking capacitor for each transformer to minimize mutual coupling.
JohnnyBerg:
You can buy Isolated DC DC converters ready made:

https://www.digikey.com/product-detail/en/recom-power/RFM-0505S/945-3159-ND/8550767

On EBay or Aliexpress even cheaper. No need to reinvent the wheel.
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod