andre tchmil

SMPS PS on. Can I abuse this function ? :)
« on: October 05, 2018, 08:06:15 PM »
hey guys, same project different question  :o

I have a nice SMPS supply here and I wonder if I can use the "PS on" function (connection to ground) to power on / off some solenoids in a rapid way without harming the PS. Or is the " PS kill" more suitable ?


abbey road d enfer

Re: SMPS PS on. Can I abuse this function ? :)
« Reply #1 on: December 17, 2018, 02:36:31 AM »
Can you provide more info? I don't know what PS on or PS kill are...?
Brand/type of SMPS? Datasheet/link?
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

andre tchmil

Re: SMPS PS on. Can I abuse this function ? :)
« Reply #2 on: December 18, 2018, 07:37:25 AM »
Can you provide more info? I don't know what PS on or PS kill are...?
Brand/type of SMPS? Datasheet/link?


that's what I found on another forum  https://static.rcgroups.net/forums/attachments/3/1/3/5/4/3/a4013688-30-Delta%20DPS-750EB%20full%20pinout.JPG

and here's a schematic of another type , same brand . thanks for looking

abbey road d enfer

Re: SMPS PS on. Can I abuse this function ? :)
« Reply #3 on: December 18, 2018, 08:06:39 AM »

that's what I found on another forum  https://static.rcgroups.net/forums/attachments/3/1/3/5/4/3/a4013688-30-Delta%20DPS-750EB%20full%20pinout.JPG

and here's a schematic of another type , same brand . thanks for looking
It looks to me like PS on is just for turning on and PS kill for turning it off, so you need an MOM/OFF/MOM switch.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

squarewave

Re: SMPS PS on. Can I abuse this function ? :)
« Reply #4 on: December 18, 2018, 10:28:13 AM »
From glancing at the schem (assuming that is the correct schem) it looks like the PS-ON net controls a photo transistor that ultimately controls the "Fast Fault" pin of the switching controller which appears to be maybe an onsemi NCP1396 for which the datasheet reads:

"Fast Fault: Fast shut--down pin. Upon release, a clean startup sequence occurs. Can be used for skip cycle purposes."

So it kinda sounds like if you ground the PSON# pin momentarily, it will stop driving within ~55ns.

Reading the datasheet regarding "Fast Fault" says:

Skip cycle possibility: The absence of soft--start on
the NCP1396A fast fault input offers an easy way to
implement skip cycle when power saving features are
necessary. A simple resistive connection from the
feedback pin to the fast fault input, and skip can be
implemented.

So if they are skipping cycles by watching the feedback network it certainly sounds like a legit thing to do.

Although it sounds like there are 2 versions of the chip that behave differently. And I'm not 100% that the schem and chip are correct. I just did some hasty googling.

andre tchmil

Re: SMPS PS on. Can I abuse this function ? :)
« Reply #5 on: December 18, 2018, 10:31:02 AM »
that's correct , but I have no idea why PS on and PS kill need both connected to ground for power.
If I connect mains , the PSU starts up in a kind of idle state, only when I connect both mentioned points to ground I have DC on the output. I would like to have a fast switching on/off on the output for experimental purposes with a solenoid.
Would certainly be easier than adding an extra relay or so.

JohnRoberts

Re: SMPS PS on. Can I abuse this function ? :)
« Reply #6 on: December 18, 2018, 10:36:31 AM »
can you leave one of the two always connected to ground?

JR
Don't only half-ass tune your drums. Visit https://circularscience.com to hear what properly "cleared" drums sound like.

andre tchmil

Re: SMPS PS on. Can I abuse this function ? :)
« Reply #7 on: December 29, 2018, 12:24:51 PM »
yes , PS kill always connected , and a relay for PS on.
I tested it and it works good . Dual fans are kicking in each time I switch on.
I know little about SMPS and just wander if fast switching on/off will hold up over time.
Or would the  PS kill better suited for the switching ?
thanks for looking
« Last Edit: December 29, 2018, 12:28:46 PM by andre tchmil »

squarewave

Re: SMPS PS on. Can I abuse this function ? :)
« Reply #8 on: December 29, 2018, 04:26:04 PM »
Is it the Delta DPS-750EB you said? The one that's $20 on Ebay?

Torture one. Test it with solenoids at full load and monitor the output voltage with a scope (or at least a meter). Then connect PS on to a function generator and drive it with a square wave. See how fast you can get the solenoids to switch and let it run like that for as long as you feel comfortable.

 

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