Multiple regulated voltages

Piotr Wyderski <peter.pan@neverland.mil> wrote in
news:qdvhp5$4tc$1@gioia.aioe.org:

That was one of the considered options, but a more conservative
design won. You have to dump the kW-level amount of heat somewhere
anyway and it is better not to have any fluids nearby when it is
operating in HV mode.
Click to expand...

They are closed systems, and the CPU boys have had years to perfect
them to be leak and problem free.
 
Piotr Wyderski wrote...
Lasse Langwadt Christensen wrote:

it is a bit special, it is emitter follower output so in principal
not an LDO, but it has extra input for a higher control voltage so
it can have a low drop out

LM1117 has 1.2V dropout in the worst case and it is
counted as an LDO. One VBE drop is absolutely fine.
Click to expand...

I think that's a shame, and try to avoid applying the
term for anything that wants more than 300 or 400mV.
We call them "lower dropout" in our book. Also see
Figure 9.11, where there's a region well below LM317
types, that should be reserved for the LDO label.


--
Thanks,
- Win
 
On Thursday, June 13, 2019 at 9:58:21 PM UTC+2, Jan Panteltje wrote:
On a sunny day (Thu, 13 Jun 2019 20:14:06 +0200) it happened Piotr Wyderski
peter.pan@neverland.mil> wrote in <qdu3pb$vnn$1@node2.news.atman.pl>:

I need +/-10V (about 1A), +/-2.5V (about 100mA) and 5V (about 60mA).
I was shocked that it is virtually impossible to find a negative voltage
LDO capable of hundreds of milliamps and reasonably cheap. It seems
that producing all these rails with a bunch of opamp-boosted emitter
followers will be cheaper than a single adjustable negative LDO.
I already have a decent 2.5V reference (LTC6655) in the project so why
exactly should I avoid the temptation of making this PSU out of discrete
elements? Noise properties should be comparable to that of an LDO and
I can shape thermal/max voltage issues with a proper transistor.

Best regards, Piotr

As long as you do not specify tolerances and ripple,
you may as well use a tapped transformer
a few diodes and capacitors
and some oscillator.
That is how PC power supplies work.
Click to expand...

Diode rectification loses about half a volt of diode drop.

Active rectification with MOSFETs can drop a lot less voltage, and you can actively regulate the rail you need to be precise, and the rest won't be too far away from nominal.

Ripple is a probelm, but post-rectification filtering and carfeful board layout can keep it pretty low.

--
Bill Sloman, Sydney
 
On Friday, June 14, 2019 at 4:46:18 AM UTC+2, DecadentLinux...@decadence.org wrote:
Winfield Hill <winfieldhill@yahoo.com> wrote in
news:qdus310fln@drn.newsguy.com:

Piotr Wyderski wrote...

To be honest, heatsinking is not exactly a problem in this case:

https://i.postimg.cc/bvq5RvjB/20190613-232726.jpg
https://i.postimg.cc/tgDMvHqC/20190613-232755.jpg
https://i.postimg.cc/4yH237zm/20190613-232817.jpg

5kg of high-performance alu + some 800 cubic meters per hour of
forced airflow. I am enchanted by the sound of this unit at its
full rated speed. Now just don't want to mess the analog
front-end.

What in the world are those fans cooling?

Probably better off putting two of the CPU self contained water
coolers under a quarter inch thick Al plate with the parts on it..
Quiet, small fans, and extremely good cooling characteristics. Much
smaller end product. Oh, and the fans and radiator are remote to
the actual cooling plates. Far easier to enclose and service.

Quieter electrically too. Especially proximal to the electronics.
Click to expand...

A heat pipe might be even better. The water gets circulated as steam - so you don't need a pump. It's got to be a made-for-the-job design, but getting one designed isn't a big or expensive deal.

--
Bill Sloman, Sydney
 
On a sunny day (14 Jun 2019 04:10:14 -0700) it happened Winfield Hill
<winfieldhill@yahoo.com> wrote in <qdvvam0261n@drn.newsguy.com>:

Piotr Wyderski wrote...

Lasse Langwadt Christensen wrote:

it is a bit special, it is emitter follower output so in principal
not an LDO, but it has extra input for a higher control voltage so
it can have a low drop out

LM1117 has 1.2V dropout in the worst case and it is
counted as an LDO. One VBE drop is absolutely fine.

I think that's a shame, and try to avoid applying the
term for anything that wants more than 300 or 400mV.
We call them "lower dropout" in our book. Also see
Figure 9.11, where there's a region well below LM317
types, that should be reserved for the LDO label.
Click to expand...

Agreed.
 
Jan Panteltje wrote:

> Agreed.

Agreed or not, that's what the TI datasheet says. I am not influential
enough to make them consider the change seriously.

Best regards, Piotr
 
On a sunny day (Fri, 14 Jun 2019 15:29:08 +0200) it happened Piotr Wyderski
<peter.pan@neverland.mil> wrote in <qe07e5$1847$1@gioia.aioe.org>:

Jan Panteltje wrote:

Agreed.

Agreed or not, that's what the TI datasheet says. I am not influential
enough to make them consider the change seriously.

Best regards, Piotr
Click to expand...

Oh I would not even try
many people and organisations say many things
Now Iran has hit some ships or so says US Precedent.
A previous one saw weapons of mass destruction in some fish and chips stands.

I do go by what I measure.

It is simple to do a discrete one with the pass transistor the other way around,
so you get at most a few hundred mV drop, driven from a diff amp.
 
On Fri, 14 Jun 2019 08:43:30 +0200, Piotr Wyderski
<peter.pan@neverland.mil> wrote:

Winfield Hill wrote:

What in the world are those fans cooling?

A mother of Godzilla dual linear electronic load.

Best regards, Piotr
Click to expand...

Can it do AC?


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
 
On a sunny day (Fri, 14 Jun 2019 10:37:15 -0700) it happened John Larkin
<jjlarkin@highland_snip_technology.com> wrote in
<jpm7ge1jhqfqa71f8cli4trpgpihs7428c@4ax.com>:

On Fri, 14 Jun 2019 08:43:30 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

Winfield Hill wrote:

What in the world are those fans cooling?

A mother of Godzilla dual linear electronic load.

Best regards, Piotr


Can it do AC?
Click to expand...

It is probably one of those super powerful audio amps for in car stereo :)
Sometimes they 'driveby' here...
 
John Larkin:

> Can it do AC?

Yes, that's the plan. Dual independent positive DC channels with common
GND, a single combined DC with double the current capacity or AC. Plus a
lot of internal and external triggers for the purpose of transient
response checking and allowing the device to act as a curve tracer for
magnetic components. All that with just 2 BNC connectors, PSoC5LP allows
obscenic level of dynamic analog reconfiguration.

This configuration allows for a significant analog resource sharing,
so there is no dual fully independent mode, with split GNDs. I don't
work with bipolar sources, so I have decided to implement this simpler
variant.

Best regards, Piotr
 
On a sunny day (Mon, 17 Jun 2019 09:27:35 +0200) it happened Piotr Wyderski
<peter.pan@neverland.mil> wrote in <qe7fc6$oq7$1@gioia.aioe.org>:

Jan Panteltje wrote:

It is probably one of those super powerful audio amps for in car stereo :)

But seriously, what can be the rightful application of such a crazy
heatsink?
My seller didn't know, it was a bargain purchase for about 17 USD.

Best regards, Piotr
Click to expand...

Yes, I bought his one some years ago:
http://panteltje.com/pub/big_heatsink_IMG_6292.JPG
lighter for size reference.
 
Jan Panteltje wrote:

> It is probably one of those super powerful audio amps for in car stereo :)

But seriously, what can be the rightful application of such a crazy
heatsink?
My seller didn't know, it was a bargain purchase for about 17 USD.

Best regards, Piotr
 
Jan Panteltje wrote:

> I do go by what I measure.

I think that the VBE should be a fair discrimination level. If below
that, you are an LDO, if above or equal, sorry, no banana.

Best regards, Piotr
 
On a sunny day (Mon, 17 Jun 2019 09:24:10 +0200) it happened Piotr Wyderski
<peter.pan@neverland.mil> wrote in <qe7f5p$nqm$1@gioia.aioe.org>:

Jan Panteltje wrote:

I do go by what I measure.

I think that the VBE should be a fair discrimination level. If below
that, you are an LDO, if above or equal, sorry, no banana.

Best regards, Piotr
Click to expand...

Agreed.
Vcesat or MOSFET will allow LDO.
Anyways the ripple must then be guaranteed not to go below that.
As electrolytic caps age and have large tolerances,
.... a huge margin is always needed.

In the sixties I did a regulator that measured the voltage across the serial transistor
and adjusted a pre-regulator (thyristor) to always have sufficient voltage
to filter the ripple.
 
Jan Panteltje wrote:

> As electrolytic caps age and have large tolerances,

Do people still use that electrochemical fossil? (kidding)

Best regards, Piotr
 
On Sun, 16 Jun 2019 18:58:14 +0200, Piotr Wyderski
<peter.pan@neverland.mil> wrote:

John Larkin:

Can it do AC?

Yes, that's the plan. Dual independent positive DC channels with common
GND, a single combined DC with double the current capacity or AC. Plus a
lot of internal and external triggers for the purpose of transient
response checking and allowing the device to act as a curve tracer for
magnetic components. All that with just 2 BNC connectors, PSoC5LP allows
obscenic level of dynamic analog reconfiguration.

This configuration allows for a significant analog resource sharing,
so there is no dual fully independent mode, with split GNDs. I don't
work with bipolar sources, so I have decided to implement this simpler
variant.

Best regards, Piotr
Click to expand...

We make some resistor simulators, but signal level, not power. We
simulate RTDs and thermistors and such. Bipolar and wideband, since
some people excite sensors with AC, or multiplex the excitation and
sensing stuff.

Resistor simulation turns out to be one of the most difficult things
we have done, especially because we need isolation and serious
accuracy.

P620 here

http://www.highlandtechnology.com/categories/measurement_simulation.shtml

and a VME module

http://www.highlandtechnology.com/DSS/V420DS.shtml


We have a couple of old Leader active DC load boxes, which are really
great to have around once in a while.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top