goldenreference low voltage power supply

[Blueman2]

Very cool!  Congratulations on the build.  And the Mechanical Engineer in me loves seeing that dainty little circuit in that massive bench clamp.  

 

[JoaMat]

Milled this today – negative regulator. Shot by USB camera approximately magnitude 20. Using a 15th end mill, minimum clearance between pads, traces etc. is 16th. There are 5 vias 12th and they actually hit the bottom pads quite accurate. CNC machine is a fantastic gadget

[chinsettawong]

Very nice!

[Pars]

Yes, that is fantastic work!


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[Kerry]

That's amazing that you can mill that board.  Nice work ?

[sbelyo]

does anyone have a GRLV + board to spare?

[JoaMat]

Thinking loud.

What if a simple CCS north of the 9 volt Zener as below?

Will certainly make a tiny smd version layout looking cleaner.

[kevin gilmore]

works fine, more diode switching noise gets thru. Also requires more voltage differential as that current source eats up about 4v.

[luvdunhill]

works fine, more diode switching noise gets thru. Also requires more voltage differential as that current source eats up about 4v.

What are 60Hz and harmonics down to with the stock design?

[kevin gilmore]

way under a microvolt. pain in the ass to measure.

[luvdunhill]

Hm, how way? -120dBV shouldn’t be hard to measure. -150dV, sure.

[JoaMat]

 

9 hours ago, kevin gilmore said:

works fine, more diode switching noise gets thru. Also requires more voltage differential as that current source eats up about 4v.

LTspice indicates a need of another 3 V unregulated. Plus more diode switching noise. Still a golden reference device or is it a silver line thing?

[sbelyo]

Is a 9+9 30 VA transformer enough to pull 9V DC from a GRLV?

[cspirou]

36 minutes ago, sbelyo said:

Is a 9+9 30 VA transformer enough to pull 9V DC from a GRLV?

That would give you ~12V before regulation which is only a 3V drop. Seems to be to cutting a little close. 10VAC is a little more comfortable.

also don't forget to change the lt1021 reference 

[sbelyo]

I'm going to connect a transformer to the mains to see what voltage it puts out.  My mains are a little high so it might be 10V or a little over

for the lt1021 reference, do I need the 5 or 7V ?

[cspirou]

4 minutes ago, sbelyo said:

I'm going to connect a transformer to the mains to see what voltage it puts out.  My mains are a little high so it might be 10V or a little over

for the lt1021 reference, do I need the 5 or 7V ?

Definitely do that. I bought a 18v + 18v transformer and it's giving me 22v + 22v.

I'll find the post but I think it's better you use 5v.

[sbelyo]

for V+: ((R8 + R7) / R7) x 10 (reference voltage of D5 - LT1021-10)

for V-: ((R9 + R10) / R10) x 10 (reference voltage of D7 - LT1021-10)

If I use this calculation and all resistors are 1.5K like the silkscreen, then use a 5V reference I'd get 10V

That'd work for me because I need 9-12 Vdc.  Now I'll see what the xformer is putting out in the way of voltage.

it's 10.96 Vac with no load so that should be fine pulling 9 - 9.25 Vdc @ 0.80 A right?

Edited January 14, 2018 by sbelyo

[cspirou]

Here it is:

10.96 VAC will give you a 5-6V drop before regulation. You should be okay.

I suspect you don't want a voltage close to the reference because then you would need a much higher R7/R10 resistor, which would increase noise.

[sbelyo]

With a 5V reference will the GRLV work with an output lower than 12Vdc?  

[mypasswordis]

Yes but I would rather go with a higher vac trafo and set it to 10Vdc output than hope that the pre-reg voltage is high enough using a 9vac trafo for 9vdc. If you really have to use the 9vac then there are any number of low noise LDOs out there to use

[JoaMat]

As I understand LT1021 is used in shunt mode in GRLV. From datasheet I get the impression that the 5 volts version of LT1021 is not meant to be used in shunt mode. As I recall one builder once tried a LT1021-5 in a KGSShvPSU without success.

[sbelyo]

I'm starting to think that I should use something else.  I think it's better

[mypasswordis]

Ah yeah forgot about that, it's in the very first paragraph of the datasheet that the 5V version only works in series mode.

The TPS7 regulators that are used in the amb modules and Dynalo mini are rated to 1A and are LDO

[cspirou]

Is the only thing keeping the GRLV from running effectively <10V the reference? In an earlier post I think Kerry mentioned using a LM4040 and those are available down to 2.048V.

[mypasswordis]

I used the 4040 on one of my GRLVs so I didn't have to put in a separate order for the LT1021. It works but is noisier than the LT1021, not sure if it's audible though