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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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