kevin gilmore Posted January 16, 2018 Author Report Posted January 16, 2018 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.
Helium Posted January 16, 2018 Report Posted January 16, 2018 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?
Pars Posted January 16, 2018 Report Posted January 16, 2018 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
kevin gilmore Posted January 16, 2018 Author Report Posted January 16, 2018 (edited) 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 January 16, 2018 by kevin gilmore
Kerry Posted January 16, 2018 Report Posted January 16, 2018 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.
Kerry Posted January 17, 2018 Report Posted January 17, 2018 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). 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 3
Pars Posted January 17, 2018 Report Posted January 17, 2018 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
Kerry Posted January 24, 2018 Report Posted January 24, 2018 (edited) 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... 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 January 24, 2018 by Kerry 8
JoaMat Posted January 24, 2018 Report Posted January 24, 2018 Just finished my morning coffee. Seems to be an interesting day. Thanks a lot Kerry. 1
Kerry Posted January 25, 2018 Report Posted January 25, 2018 Just another rendering with the transistor and screw mounting in... 9
ang728 Posted January 27, 2018 Report Posted January 27, 2018 (edited) 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 January 30, 2018 by ang728
kevin gilmore Posted January 28, 2018 Author Report Posted January 28, 2018 (edited) same size board, up to 35mm caps, had to move the pass transistors, needs checking silicon carbide rectifiers 100mm x 109mm goldenreferencelargecap.zip Edited January 28, 2018 by kevin gilmore 5
Helium Posted January 29, 2018 Report Posted January 29, 2018 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. Pars, any chance you have more rectifiers left? I'd like to try them out on one set of GRLVs.
steefdebruijn Posted January 29, 2018 Report Posted January 29, 2018 Is there a possibility to add them to the running group buy?
Pars Posted January 29, 2018 Report Posted January 29, 2018 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.Sent from my iPhone using Tapatalk 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
steefdebruijn Posted January 29, 2018 Report Posted January 29, 2018 Sorry if I was not clear. I meant the rectifier boards.
mwl168 Posted January 30, 2018 Report Posted January 30, 2018 (edited) 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 January 30, 2018 by mwl168
Helium Posted January 30, 2018 Report Posted January 30, 2018 mwl168, Pars 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.
Pars Posted January 31, 2018 Report Posted January 31, 2018 ^ Posted the gerbers in the GB thread, but here they are again as well... Bridge_Vert.zip 1 1
penmarker Posted February 8, 2018 Report Posted February 8, 2018 Anybody has experience with electronic constant current loads from PSU testing purposes? Quite interested but I'd wanna weigh in other comments first.
masamoto Posted February 13, 2018 Report Posted February 13, 2018 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?
jose Posted February 13, 2018 Report Posted February 13, 2018 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.
sorenb Posted February 13, 2018 Report Posted February 13, 2018 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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