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kevin gilmore

goldenreference low voltage power supply

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The opamp needs to be able to run on what the output voltage is, and the zener plus 1.4V has to be less than the desired output voltage.

 

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Is OPA134 or LME49710 good for +/-30VDC output? Supply voltage is ±2.5V to ±18V, so I guess not. Only choice is OPA445 then. 

Could you elaborate more on zener please? Is 9.1V 1W 1N4739A from the BOM good for +/-30VDC output?

 

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The opamp in the GRLV runs single supply, so it will only see V+ or V- to gnd. OPA134, etc. is fine as long as it’s total max voltage is high enough, 36V in this case.

 

The 9.1V zeners are fine for this as well.

 

 

Sent from my iPhone using Tapatalk

 

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The Zener voltage minus 1.4V (darlington) plus about 1 V across the control transistor specifies the minimum output voltage.

The zener guarantees enough start up voltage to power up the opamp

so something like 8v with a 5v reference

Edited by kevin gilmore

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Maybe use a LED instead in the Zener and use a low voltage op amp.  I saw some that have supply voltages from 1.8v - 10v.

I can run this through spice this evening.

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So here's something that should work as a 5V supply.  I've run it in LTSpice and it shows < 3uV of noise at 5A output.  Reality will push that up a bit with the reference being a big culprit.

You've got to have at least 2.5V above your output to regulate, but 3V is safer (like Kevin said).

GRLV-5V.thumb.jpg.1ad75c10a90932867db8aaf13a1cb7f4.jpg

I had to kill the current source feeding the reference, but that was driven more by the LT1021 (higher current requirements) and higher voltages and is not really necessary.  I've run my GR78xx without the current source just fine.  

Also, you might be able to get away with one LED (for D9/D12) depending on the OpAmp min supply voltage.

Hmmm... Less parts / smaller parts... could this fit on a smaller board B)

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Nice Kerry!

Loving the SiC rectifiers. Would love a GRLV done like this (both std. LT1021 and your lower voltage version here... not sure if a single PCB could support both?), with

1) 3 output terminal blocks (2.54 and 5.08mm pitch)

2) Dispense with the 3rd bridge support

3) Support up to 35mm main caps

This of course doesn't fit with your less/smaller goals above... might be great for the next GB :indra:

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Here's one for Joachim ;) 

It a low voltage version of the GR78xx Micro.  It's only .45"(W) x .8"(H).  It can run from 5V to 20V (with the right parts).  I still need to do the negative. 

Here's what it looks like...

Front.thumb.jpg.655b8c36b2eca923c5d50786d06543c1.jpg Back.thumb.jpg.b885f73e6c047a309137d8f0e662dc31.jpg

 

GR78xxMicro_2018-Jan-20_11-19-57PM-000_CustomizedView19871757487_png.thumb.png.e24e86f5fd16cab9a6a592b9b6a16d31.png

I also re-did the layout of the larger version that can support up to 50V now.

 

I can also do a supply that accepts these regulators, but pretty much any board designed for the LM78xx/LM79xx should support them.

Edited by Kerry
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Just finished my morning coffee. Seems to be an interesting day. Thanks a lot Kerry.

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Just another rendering with the transistor and screw mounting in...

GR78xxMicro_2018-Jan-25_04-28-30AM-000_CustomizedView12548132324_jpg.thumb.jpg.7baa2ee05d83a60713a1df9f668ba51e.jpg

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On 2018/1/27 at 5:41 AM, UFN said:

Neat! How big is the PCB?

about 130*65mm  

max od.for pre-reg cap is 30mm 

tant and opamp compensate caps are moved to the backside of pcb

Edited by ang728

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On 20.02.2017 at 12:21 AM, mwl168 said:

Another two GRLV live! These are set up for 20VDC rails to power my dual-mono SS Dynalo.

Thanks to Pars for his creation and generosity of sharing the Schottky bridges with a built-in AC snubber. Although I have to settle for the LM4040 VREF for now until I get the LT1021.

 

GRLV with Schottky bridges.JPG

schottky bridges.JPG

Pars, any chance you have more rectifiers left? I'd like to try them out on one set of GRLVs.

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Pars, any chance you have more rectifiers left? I'd like to try them out on one set of GRLVs.

No I don’t, at least that I want to get rid of. Also, I’m interested in Kevin’s latest large cap version, which checks most of the boxes I was looking for. The SiC rectifiers used on that are Schottky...
The larger diameter caps would allow much shorter (25-30mm) caps to be used, allowing something like a 1U chassis for a Dynalo Mk2, etc.


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Is there a possibility to add them to the running group buy?

Add what? Rectifier boards? Kevin’s latest large cap GRLV? The mid-size GRLV?


Sent from my iPhone using Tapatalk

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I have some of Pars’ rectifier boards made (with Pars’ permission) and can spare a few.

PM me if you are interested.

EDIT: just read that this board will be added to the GB in the 2018 GB thread. That’s a better option - in many cases, the shipping from me will likely equal or exceed the cost of the boards.

Edited by mwl168

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mwl168Pars thank you.

Pars would you mind sharing Gerber and BOM for discreet rectifier board please?

I don't think that I will participate in the nearest PCB GB, but I'll try to have them made when I order PCBs for myself next time.

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Anybody has experience with electronic constant current loads from PSU testing purposes?

Quite interested but I'd wanna weigh in other comments first.

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For some reason, the Positive Rail starts giving out 22.4 while the negative is still at -20 stable.

The LED next to the MJF15030 only lights up very shortly when I switch it on and stays off after that.

Are there any subjects I should check?

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I'm not very good at this :( but seeing the scheme led 1 is directly powered by the diode bridge and and the negative side is connected to KPS92. I would look there first.

 

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1 hour ago, jose said:

I'm not very good at this :( but seeing the scheme led 1 is directly powered by the diode bridge and and the negative side is connected to KPS92. I would look there first.

 

Yes, check your rectified input voltage ...probably too low ...or you might be pulling too much current >3A or so

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