A project log for Power supply power-on sequencer

This device reduces the amplitude of current peaks when you power many power supplies at the same time

Yann Guidon / YGDESYann Guidon / YGDES 03/24/2017 at 03:474 Comments

I just solved the power supply issue.

It is not a problem to get low voltage DC from high voltage AC but in my case, the power supply's characteristics matter.

The current draw is expected to be in the 50mA range, at most. There are a lot of cheap power supplies but most cheap ones are in the 500-700mA range, suitable for USB. The power is too high, with rather large capacitors.

When there is a power failure, these capacitors keep some charge for "a certain time", which keep the circuit on. The SSR will remain latched and if the power is restored immediately, a high current spike will occur, which is what we want to avoid !

I found these modules, sold for a few buck only and rated for 5V 1W, that's 200mA.

It's probably going to need some conformal coating though but we're almost done.

However there must be a "fast reset" of the circuit : if the power is absent for more than 1/5s, the whole sequencer must be reset.


K.C. Lee wrote 03/24/2017 at 04:49 point

I have seen the potted version for high current.  Here is a review of one of the better ones:


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Yann Guidon / YGDES wrote 03/24/2017 at 04:53 point

the link doesn't seem to work, even with the leading H

anyway, that model is a 3W while I only need 1W

thanks :-)

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Yann Guidon / YGDES wrote 03/24/2017 at 15:10 point

Thanks :-)

The final suggestions are great : don't forget the fuse and the overvoltage protection.

I use the most capable MOV I can but I think I forgot the fuse in my last design...

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