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konst 13th September 2020 06:59 PM

Mark, thank you very much for designing these and making them available.

I ordered 10 of these from and will have 6 left over after I am done.

The first 6 people to pm me their address will get one each for free when these arrive.

Mark Johnson 13th September 2020 07:02 PM

Very generous of you, konst! Thank you from everybody.

DontHertzMe 13th September 2020 07:45 PM

Mark, what would you recommend for a startup current limiter so that the charging of larger caps don't put an SMPS into over-current protection?

Mark Johnson 13th September 2020 08:55 PM

I've never tried to build an SMPS startup current limiter myself; I have no practical experience and I'm unable to say "method X worked well for me".

Exactly seven days ago another diyAudio member asked me this very same question on PM. To save thinking, and typing something new, here is copy and paste


Keep in mind that there are no depletion mode Pchannel MOSFETs anywhere; they do not exist. There are dramatically fewer PNP power BJTs than NPN. There are dramatically fewer Pchannel power MOSFETs than Nchannel.

So I recommend that you design the circuits for whichever supply rail it is, that needs PNPs or Pchannel MOSFETs. Do that rail first. When it's all done and your design works great, it will be an easy and quick exercise to flop out another copy using NPNs and Nchannel MOSFETs for the other supply rail.

I think perhaps the first idea I would try, is a fairly simple one. Create a constant current source whose output current is 10% or 20% lower than the SMPS rated max current, and install it in series between the SMPS and the capacitor bank. At turn-on, let this CCS charge the capacitor bank at the constant current rate. The overcurrent protector won't trip because you're 10% or 20% below its trigger level.

Then after T seconds of this, activate a relay which shorts out the CCS, and connects the capacitor bank straight to the SMPS with a direct pathway. Choose T to be long enough to fully charge the cap bank, but not long enough to really annoy the human listener who has to wait an excruciating T seconds before music appears.

This is probably not the best way or the fastest way or the most elegant way or the lowest-parts-cost way. But I do think it's pretty easy to describe, and pretty easy to conceive an implementation ,that might have a decent chance of working correctly on the first try.

konst 18th September 2020 01:03 AM

boards arrived today, they are tiny! I used jlcpcb and they are amazing value. Shipping cost 3.5x as much as the actual boards, thanks again for designing these.

Only two people have so far expressed interest in the spare 6 I have, PM me if you want one, I will be mailing them out over the weekend.

ClaudeG 18th September 2020 06:16 AM

Great news and well done!


ClaudeG 22nd September 2020 02:55 PM

Pity Konst's effort and amazing offer doesn't trigger more interest.

I can see myself using/testing Mark's latest toy on a low cost SMPS for a HP amp and if successfull possibly replicate then another one for my B1 Korg... we have and will have more SMPS in our beloved hifi devices, worth a go...

Thanks to make it happen and available


konst 22nd September 2020 06:21 PM

I have 3 left, the first 3 will go out today (as soon as I buy some stamps)

ClaudeG 22nd September 2020 06:29 PM

I should queue again perhaps then GLOL!

Thanks again for all this!


konst 30th September 2020 08:25 PM

I just sent out the boards, sorry about the delay but I have a really big project on at the moment and was not able to get to the USPS.

Letters are going to France, Britain, Australia and US.

I have a couple more left if anyone wants one.

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