[time-nuts] Power supply for Thunderbolt

Jeroen Bastemeijer J.Bastemeijer at TUDelft.nl
Mon Apr 21 05:16:48 EDT 2008

Dear David,

I have no recipe for your thunderbolt powersupply, but the Ebay power 
supply you mention is not a linear power supply but a switching power 

I have two Thunderbolts however, these boards came from Telecom and have 
a 48V switcher built in. So I use them in the same way as I use my Z3801.

As a suggestion for your power supply: You could consider using multiple 
transformers. One for each voltage. This will lower the dissipation, 
certainly for the low 5V voltage.

Good luck, Jeroen

David C. Partridge schreef:
> I'm in the process of buying a Thunderbolt, and will need to provide it with
> some volts.
> I sat down over the weekend to design a linear supply for it.  Initially
> things looked OK using a 12-0-12 transformer, and a few IC voltage
> regulators, but then I did some worst case design and dissipation analysis,
> and found that I needed to use a 15-0-15 transformer to allow for a -10%
> mains variation, and add pass transistors and lots of heat sinking to all
> the regulators to allow for a +10% mains variation.
> Add to that transformer regulation issues (over-size transformer), the time
> to design the PCB and the cost of getting it made, and things started to
> look expensive :-(.
> I can probably source a linear supply on eBay, but these are typically
> pretty large and heavy.  For example: eBay item number 330201077319
> So is it reasonable to use an SMPS, and add additional filtering to the
> output?  Typically these talk in terms on 150mV ripple & noise which I need
> to reduce by a factor of ten or better. 
> If you have been there, done that, I'd be interested to hear what you did.
> Thanks
> Dave Partridge
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Ing. Jeroen Bastemeijer

Delft University of Technology
Department of Electrical Engineering
Electronic Instrumentation Laboratory
Mekelweg 4, Room 13.090
2628 CD Delft
The Netherlands

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E-mail: J.Bastemeijer at TUDelft.nl
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