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Need help with current limiting.

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Patrick

Sun Jan 21 2018, 06:47PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

klugesmith wrote ...

Could even literally saw off the board near the isolation line.

this does sound like something i would do.

but i do need 24v, 12, 5 and an adjustable Vout for this first one. so id like it to be built entirely of my own design. Also the main purpose of this project is to learn every part of an off-line and isolated supply. Also this first one is basically a ATX PS, with a 24V wire too. but the next PS's will be 300-500 watt ones with 48 and 90 Vdc and some other odd Vdc version ones in between. And the board houses have a 5 board minimum, so changing the component values to get diffent outputs doesnt seem to hard (but for the opto). so ill probably be buying 10 more of those gang boxes.

I really need that 90 Vdc @ 2 amp one too, my mega (52kv) flyback doesnt want anything more or less it seems.

Im willing to have a slow opto response to regulation error if that means no bizarre oscilations and easier component values in the circuits below. Keep in mind i dont have a network analyzer.

1516564672 2431 FT1630 Onstableloopsfig1

Made another box just for the boards im drawing up now in KiCad.

unrelated, but my ground bot can be seen here.

Patrick

Sun Jan 21 2018, 08:03PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Plasma

Mon Jan 22 2018, 03:28AM

Registered Member #61406 Joined: Thu Jan 05 2017, 11:31PM
Location:
Posts: 268

The middle compactor and pfet is replaced with a hex inverter the optoislotor is lm311, but will double check. The solid switch is on a different board

johnf

Tue Jan 23 2018, 05:13AM

Registered Member #230 Joined: Tue Feb 21 2006, 08:01PM
Location: Gracefield lower Hutt
Posts: 284

Plasma
R1 10K is no where near enough to drive an opto should be around 1K or just below especially to take in aging of the IR LED

hen918

Tue Jan 23 2018, 12:03PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

johnf wrote ...

Plasma
R1 10K is no where near enough to drive an opto should be around 1K or just below especially to take in aging of the IR LED

The opamp drives the opto, not R1.

johnf

Wed Jan 24 2018, 04:21AM

Registered Member #230 Joined: Tue Feb 21 2006, 08:01PM
Location: Gracefield lower Hutt
Posts: 284

Hen918
Really
LT1011 is open collector output so source is from VDD through 10K

hen918

Wed Jan 24 2018, 10:18AM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

johnf wrote ...

Hen918
Really
LT1011 is open collector output so source is from VDD through 10K

ahhh, maybe I should have read further down the datasheet. At the top it says it can source and sink 50 mA, only when you get to the application note does it give you a drawing of the output stage.
Thanks for putting me right.

Patrick

Wed Jan 24 2018, 04:01PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

I'm going to pick one of the more common opto layouts and send the board out. We can alway change values later as long as the holes and traces are right. And I'll include a prototype hole grid on the optometrist low side and another on the current transformer side.

Patrick

Sun Jan 28 2018, 08:25PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Ok i went back and looked at Uzzors2k's website and found his excellent article on all kinds of SMPSs. specifically this one:

Auxiliary Flyback SMPS

i first saw this years ago, and he uses a simple opto loop and values.

Im going to include traces for non-isolated FB, type 1,2,3 and several prototype strips like a breadboard and wrap the issue up. its time to move on to Power and logic trace layout.

Patrick

Thu Feb 01 2018, 03:15AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

making progress...

Heres the new box, painted red this time. 16 awg 3 conductor rubber SOOW cord. Ground lug and screw at the bottom, hot and neutral will be soldered directly to the main board.

I painted it red because that's what I had on hand ill paint each unit a different color.

Top will be drilled out like the green one and a spec label put on.

The upper cinch will out put heavy wire of 24+, 12+, 5+ Vdc each with a dedicated black ground, and then a single green chassis wire should i need it in some odd application.

The lower cinch will carry smaller diameter wire of 3.3+, 5+, 9+, 12+ and -12 Vdc. these will be regulated tighter than the heavy current ones and current limited with noise isolation for logic. There will be no green ground for these, just black wires.

The previous version was converted into a multi charger with a ebay SMPS.

Now i can charge all of my devices at once and in the same place, without 9 million wall warts plugged in all around the house.

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