[sdiy] Odp: Re: Roman Filippov power supply design

[Roman]

One can abuse boost converter as inverter by adding negative peak detector (not sure if that's proper term). A capacitor and 2 diodes driven by coil's ramp voltage.   Roman  Dnia 9 maja 2017 23:24 Guy McCusker <guy.mccusker at gmail.com> napisał(a):  Can the LM25575 be used for 12V -> -15V ? The datasheet says that OUT  to GND is limited to Vin. That's why I guessed that it used the 15V  from the other converter as its input.   I didn't think about using the PCB layer as a heatsink though -- I am  a total novice at this! -- so that's a bit of very helpful insight.   On Tue, May 9, 2017 at 10:04 PM, Roman <modular at go2.pl> wrote:  My guess is IC2 (LM27313) is used for +12 -> +15V conversion. IC3 (LM25575)  is used as boost/inverter +12V -> -15V.  Obviously IC1 (LM2575) is for 5V.   If I was Roman F. I'd utilize most of the bottom layer as heatsink,  especially that IC1 and IC3 have exposed pads made just for that. IC2 (+15V)  has pretty good efficiency when supplied from 12V, about 90% according to  datasheet, so might be just slightly warm using only a bit of top layer  copper around it as heatsink.   Roman   Dnia 9 maja 2017 17:36 Guy McCusker <guy.mccusker at gmail.com> napisał(a):   Roman Filippov is selling PCBs for a power supply which he says is  enough for a Music Easel or 8 of his Buchla clone modules:  electricmusicstore.com electricmusicstore.com   The board takes 12VDC input and produces +/-15V, +12V and +5V. Taking  a look at the BOM, I can see a 5V switching regulator, a boost  converter and a buck converter.   Presumably the 12V input is passed straight to the output, and the 5V  regulator does the obvious thing. For the +/-15V, do you think it  likely that he's using the boost to produce +15V, and then using the  buck converter to produce an inverted version of that for the -15v?   If so, then could someone check my reasoning and calculations for the  maximum current one could get out of this please? I am thinking this:   the boost converter has a thermal resistance of 166 deg/W. I see no  heatsinking and at 25C ambient and max operating temperature of 125 we  have about 100 degrees to play with, so can afford to dissipate 0.6W.   The device is up to 90% efficient, so that would mean we could get  5.4W out of it, dissipating the other 0.6W. So it can produce  something like 360mA of current, and this has to feed both the +15V  and -15V rails. You get a bit less because of the inefficiency of the  buck converter for the negative rail, so we're looking at about 150mA  per rail.   This does not seem enough. On the other hand I don't exactly know what  I am talking about here. Have I messed this up?   Cheers,  Guy.  ______________________________  Synth-diy mailing list   Synth-diy at synth-diy.org  synth-diy.org synth-diy.org     ______________________________  Synth-diy mailing list   Synth-diy at synth-diy.org  synth-diy.org synth-diy.org
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