Improving the LM3x7 regulator circuit - Page 12

carlmart · 12th June 2011, 01:02 PM

OK.

How should I handle the transistor-modified regulator if I want to use it for higher voltages, like 60 volts? I mean keeping the improvements.

martin clark · 13th June 2011, 07:25 PM

The improvements stand. And there is no problem to using a 3x7 at voltages above 37v in the datasheet. That '37v' is maximum differential between input and output voltages allowable (subject to thermal constraints)

The trick is ensuring the LM317/337 is not exposed to more than about 30v differential from IN to OUT during startup and normal running.

The easiest way to do this is to use a large zener diode , say 15 or 18v , min 1.3W or 5w rating preferrd, in place of th reverse-bias diode between IN and OUT pins. Then, when the PSU starts-up, the zener avalanches until this voltage differential diminshes to something the regulator can withstand. At swtch-off, it behaves like the recommended diode. The zener only needs a voltage rating of a volt or two greater than the expected input-output differential so that it is 'out of circuit' during normal operation.

If you need to stand-off very high voltages the extended datasheet contains several suggestions - up to 2000V!

io · 18th June 2011, 11:50 AM

Hi

I use this low-impedance analog LM317/TL431 5 volts to Wolfson DAC.
simple

io

jackinnj · 18th June 2011, 02:08 PM

Really good LR on that IO Shunt -- I would like to confirm it experimentally:

I get impedance of around 2milliOhms which is consistent with your chart.

io · 18th June 2011, 02:43 PM

Hi
Yes it is.
intermediate version is stable curves (bond will not be published)
and bottom of today (srb-Snoise)

AndrewT · 18th June 2011, 03:18 PM

Quote:

Originally Posted by io

(bond will not be published)

Quote:

and bottom of today

What do you mean in these two phrases?

io · 18th June 2011, 03:19 PM

mid-development version, stable operation
Top line probe gnd,
bottom line power ON

carlmart · 18th June 2011, 07:27 PM

Quote:

Originally Posted by io

Hi
Yes it is.
intermediate version is stable curves (bond will not be published)
and bottom of today (srb-Snoise)

Are these curves for real or simulations?

The impedance curve gets to improve on the Jung Super Regulators?

They were 100 microohms at a 10K frequency:

http://waltjung.org/PDFs/Regs_for_Hi..._Audio_2_B.pdf

How can that be possible without the massive feedback in Jung's regulator?

io · 18th June 2011, 07:59 PM

upgrade now circuit
simulations 100hz-1Mhz= max 290 nanoOhms

real? I can not be measured

martin clark · 08:38 PM

That sim performance absolutely will not be what you get if you build one - the TL431 will dominate, it can be a noisy little sod - and does not have much gain at all; certainly not enough to drive output Z down to these levels, or maintain it there to a few 10s of khz, let alone Mhz.

18th June 2011, 08:19 PM	#120
martin clark diyAudio Member Join Date: Jul 2003 Location: Bath, UK	That sim performance absolutely will not be what you get if you build one - the TL431 will dominate, it can be a noisy little sod - and does not have much gain at all; certainly not enough to drive output Z down to these levels, or maintain it there to a few 10s of khz, let alone Mhz. Last edited by martin clark; 18th June 2011 at 08:38 PM.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Improving a turntable (motor controller circuit) ;)	sek	Analogue Source	26	15th September 2008 08:44 AM
Improving on LCaudio LowNoise regulator	ABO	Power Supplies	43	14th January 2005 11:53 AM
Fet regulator circuit	HarryHaller	Solid State	47	8th January 2003 03:26 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

12th June 2011, 01:02 PM	#111
carlmart diyAudio Member Join Date: Mar 2001 Location: Brazil	OK. How should I handle the transistor-modified regulator if I want to use it for higher voltages, like 60 volts? I mean keeping the improvements.

13th June 2011, 07:25 PM	#112
martin clark diyAudio Member Join Date: Jul 2003 Location: Bath, UK	The improvements stand. And there is no problem to using a 3x7 at voltages above 37v in the datasheet. That '37v' is maximum differential between input and output voltages allowable (subject to thermal constraints) The trick is ensuring the LM317/337 is not exposed to more than about 30v differential from IN to OUT during startup and normal running. The easiest way to do this is to use a large zener diode , say 15 or 18v , min 1.3W or 5w rating preferrd, in place of th reverse-bias diode between IN and OUT pins. Then, when the PSU starts-up, the zener avalanches until this voltage differential diminshes to something the regulator can withstand. At swtch-off, it behaves like the recommended diode. The zener only needs a voltage rating of a volt or two greater than the expected input-output differential so that it is 'out of circuit' during normal operation. If you need to stand-off very high voltages the extended datasheet contains several suggestions - up to 2000V!

18th June 2011, 02:08 PM	#114
jackinnj diyAudio Member Join Date: Apr 2002 Location: Llanddewi Brefi, NJ	Really good LR on that IO Shunt -- I would like to confirm it experimentally: I get impedance of around 2milliOhms which is consistent with your chart.