DIYHiFi.org

For the sake of audio
It is currently Sun Dec 17, 2017 2:30 am

All times are UTC




Post new topic Reply to topic  [ 30 posts ]  Go to page 1, 2  Next
Author Message
PostPosted: Wed Dec 03, 2008 6:41 pm 
Offline
Sheep

Joined: Mon Oct 08, 2007 1:37 pm
Posts: 88
Location: Ontario, Canada
Taken from a thread on the 'dreaded' diyaudio.com but interesting just the same. After reading this thread it appears the designer of this circuit suggests that this has all the advantages of batteries without being batteries.

http://www.diyaudio.com/forums/showthread.php?s=&postid=1674557#post1674557

Quote:
I already blocked source jitter, but I didn't block mains noise. Clean power supplies turned out to be just as important as low timing jitter. Battery power supplies have the potential of providing a clean power supply voltage, but using batteries can be rather problematic.

First I had the illusion that a super regulator could solve this mains noise issue, it turned out it can't. The noise still enters through the multiple closed current paths between transformer, connected electronics, and connected equipment (amplifiers, CD players, Computers). The noise causes both DC and ac voltage drops across GND, that are then added to the clean super reg output, resulting in virtually similar noise levels at the load. Even worse is that the current path often extends to connected equipment, causing even more problems.

So I figured the only way to get rid of the mains noise was to completely interrupt the current paths between transformer and electronics while still transferring the required energy. In other words, I had to transfer energy from transformer to load without actually connecting both.

Well I have come up with a suitable solution, the charge-transfer power supply. It completely interrupts the current path between both transformer and load (blocking mains noise) while still transferring energy from the mains power supply to the load.

At first I tried all the tricks that are commonly used in an attempt to obtain clean power supplies (Schottky diodes, exotic caps, filters, ultra-low noise voltage regulators, super regulators, gyrators and so on). But compared to a good battery power supply, all these tricks simply seemed to fail.

I spend quite some time figuring out what caused this, why does a battery power supply work so much better, despite comparable noise levels?

It appears to be the pollution on the supply current path, a battery creates a pure DC supply current path, while a mains voltage creates both a DC and ac (pollution) current path at the same time. Since this current runs through all connected electronic circuits, it pollutes all.

So I attempted to mimic a battery power supply using a mains power supply. My batteries are electrolytic caps, and they are depleted within a few hundred milliseconds, so they need to be charged frequently, 50 ... 120 times a second. This is done by using an electronic power switch that is operated at the mains frequency (half-wave rectifier), or double mains frequency (full-wave rectifier). The trick is to charge this capacitor without introducing the unwanted polluted current path between transformer and load.

They say that a picture tells more than a thousand words, so I added a simple basic schematic of both a conventional mains power supply, and the new charge-transfer power supply.

I used the red color to indicate the polluted current path, and the green color to indicate the clean current path. The dark red color at the peak of the sine-wave illustrates the charge current flow, the electronic switch is OPEN during this short charge cycle.

The blue color indicates no current flow (rectifier diodes are not conducting). This basically means that the unwanted charge current path is interrupted (open circuit) during this time

These charge-transfer power supplies seem to be able to mimic a very good battery power supply, while running on a heavily polluted mains power supply.

I already tested 3 of these charge-transfer power supplies (+10V, -10V, and -20V) in the DI4T, the impact on sound quality could best be described using your phrase "I have no words ....".


Regards,
Dan :grin:


You do not have the required permissions to view the files attached to this post.


Top
 Profile  
Reply with quote  
PostPosted: Wed Dec 03, 2008 8:10 pm 
Offline
Board jester
User avatar

Joined: Mon Dec 13, 2004 3:08 pm
Posts: 2042
Can you explain how such a power supply works?

_________________
Elso


Top
 Profile  
Reply with quote  
PostPosted: Wed Dec 03, 2008 8:11 pm 
Offline
Goat

Joined: Sat Mar 04, 2006 5:26 pm
Posts: 576
Location: Nova Scotia
So, um, what happens if C1 and C2 have different voltages and you close the switch?


Top
 Profile  
Reply with quote  
PostPosted: Wed Dec 03, 2008 8:16 pm 
Offline
Board jester
User avatar

Joined: Mon Dec 13, 2004 3:08 pm
Posts: 2042
gmarsh wrote:
So, um, what happens if C1 and C2 have different voltages and you close the switch?

Supposedly C2 is a super-cap and charged with the switch closed. Then the switch openend when power is drawn?? Right, wrong?
:shock:

_________________
Elso


Top
 Profile  
Reply with quote  
PostPosted: Wed Dec 03, 2008 8:34 pm 
Offline
Benjamin
User avatar

Joined: Mon Dec 13, 2004 3:29 pm
Posts: 4333
Location: Somewhere other than here.
Bet it only works with low-power stuff.

Part of getting low 1/f noise performance is good DC stability. If the voltage sags a lot in the time the cap supplies the load all by itself........well, you fill in the blanks.

Jocko


Top
 Profile  
Reply with quote  
PostPosted: Wed Dec 03, 2008 8:35 pm 
Offline
Sheep

Joined: Thu Jan 13, 2005 10:34 am
Posts: 92
Location: Bath, UK
Elso - that is gmarsh's point, isn't it?

If the switch is a 'dead short', and there is a difference in potential between caps, you get an EMI mess just the same as any other rectifier.

If the switch is softened by using , say a small amount of series R, or perhaps FET switch with a controlled turn-on time then...there's no topological difference from a regular rectifier with some series R (or selected secondary winding resistance) except (perhaps) you get to choose the refresh freqency and so spray the impact around a little.


I asked the same questions of the people behind those 'never connected ' supplies. Never did get an answer that made sense.


Last edited by Martin Clark on Wed Dec 03, 2008 8:37 pm, edited 1 time in total.

Top
 Profile  
Reply with quote  
PostPosted: Wed Dec 03, 2008 8:36 pm 
Offline
Pig
User avatar

Joined: Mon Dec 13, 2004 2:32 pm
Posts: 1325
"Polluted supply"? If you have stumbled across one, don't use it at all, just run away as fast as you can, you may get infected... :hello:

Other than usual audiophile lyrics... it may and may not work. The concept actually doesn't look that new. You can try to Google for "never connected".


Top
 Profile  
Reply with quote  
PostPosted: Wed Dec 03, 2008 8:55 pm 
Offline
Sheep

Joined: Mon Oct 08, 2007 1:37 pm
Posts: 88
Location: Ontario, Canada
Elso Kwak wrote:
Can you explain how such a power supply works?
As some of you might know my electronics knowledge is very limited but that doesn't dampen my interest in potential DIY upgrades for the projects I have. I'm assuming that this designer is using some sort of switching device to charge C2 with C1 and then opens a switch to let C2 supply the circuit while C1 recharges. That's my guess.

Regards,
Dan :doh:


Top
 Profile  
Reply with quote  
PostPosted: Wed Dec 03, 2008 9:14 pm 
Offline
Goat

Joined: Sat Mar 04, 2006 5:26 pm
Posts: 576
Location: Nova Scotia
Dan Twomey wrote:
Elso Kwak wrote:
Can you explain how such a power supply works?
As some of you might know my electronics knowledge is very limited but that doesn't dampen my interest in potential DIY upgrades for the projects I have. I'm assuming that this designer is using some sort of switching device to charge C2 with C1 and then opens a switch to let C2 supply the circuit while C1 recharges. That's my guess.

Regards,
Dan :doh:

As far as implementation, auxiliary windings on the transformer or a separate transformer could be used to turn on a FET acting as the switch.

(Hey! I'm a bit patent-bitter right now, so I'll say this. This idea was invented by me, right now, as an innovation on transformer-driven synchronous rectification for "never connected" power supplies. I'm now placing this work in the public domain.)


Top
 Profile  
Reply with quote  
PostPosted: Wed Dec 03, 2008 10:32 pm 
Offline
Sheep

Joined: Mon Oct 08, 2007 1:37 pm
Posts: 88
Location: Ontario, Canada
TNT Audio has a brief review http://www.tnt-audio.com/accessories/ncpsu_e.html of the Never Connected PS and a small peek at the PCB.

Regards,
Dan :blink:


Top
 Profile  
Reply with quote  
PostPosted: Wed Dec 03, 2008 11:38 pm 
Offline
Benjamin
User avatar

Joined: Mon Dec 13, 2004 3:29 pm
Posts: 4333
Location: Somewhere other than here.
So......unless it is totally glitch-less, how is it better? They have enough parts on that PCB that maybe they can control the turn-on.

Jocko


Top
 Profile  
Reply with quote  
PostPosted: Thu Dec 04, 2008 12:32 am 
Offline
God

Joined: Thu Dec 30, 2004 10:50 pm
Posts: 998
Location: Minnesota
I think the designer is pulling a fast one, without seeing what else there is to this.

A little studying on; line conducted noise, fast transient test, burst test, etc. Would have probably answered a few questons for the guy. This has all been looked at before. By anyone who has to pass EN 55011, 55022, and other standards. Been there, done that, got the T-shirt.

Mike


Top
 Profile  
Reply with quote  
PostPosted: Thu Dec 04, 2008 12:25 pm 
Offline
Sheep

Joined: Mon Oct 08, 2007 1:37 pm
Posts: 88
Location: Ontario, Canada
Following the aforementioned DIYAUDIO.COM thread the circuit designer has been kind enough to post more details including a schematic about this charge transfer PS. He goes onto say,

Quote:
> First the primary smoothing cap (Cp) is charged with the polluted rectified voltage through D1 ... D3. R1 puts a positive voltage on P-FET T1, switching it OFF, and disconnecting the load during this charge cycle.

All interference surges through the primary smoothing cap -not the connected load- The severety of the pollution really doesn't matter at this point, main purpose is to get the primary smoothing cap Cp charged.

> Next the rectified voltage drops below the voltage across the smoothing cap Cp plus voltage drop across the rectifier diodes D1 & D3 or D2 & D3, now the rectifier diode no longer conducts, and interrupts the noisy charge current. All that remains after this interference attack is a charged capacitor. The P-MOSFET is not yet switched-on as -Vgs is still too low to make it conduct.

Now we have a floating charged cap (Cp), it's basically similar to a battery connected to GND with the minus terminal. Needless to say that all the interference signals during charging are not "remembered" by capacitor Cp.

> As the sinewave voltage drops, P-channel MOSFET -Vgs gets high enough, and T1 switches-ON. T1 now connects charged cap Cp to both Cs and load, the charge of the primary smoothing cap supplies clean energy to both Cs and load.

> After the sinewave voltage rises again, -Vgs drops and T1 is switched OFF. Now the secondary smoothing cap Cs continues to supply clean electrical energy to the load.

The cycle is repeated 50/60 times a second with half-wave rectifiers, and 100/120 times a second with full-wave rectifiers.

Both D4 and D5 (Zener diode and Schottky diode) are added for protecting the gate of T1.

D3 was added to create the required switching signal for T1. T1 is switched-on by pulling the gate to GND through both R1 and R2, the protection diodes D4 and D5 will limit -Vgs. T1 is switched off by pulling the gate to plus through R1.

The peak charge transfer current through Cs is limited by the P-MOSFET RdsON, but can be further manipulated by adding an extra series resistor in the drain lead.

Negative charge-transfer power supplies are very similar, just use a N-MOSFET, and reverse polarity of diodes and caps


Regards,
Dan


You do not have the required permissions to view the files attached to this post.


Top
 Profile  
Reply with quote  
PostPosted: Thu Dec 04, 2008 3:15 pm 
Offline
Sheep
User avatar

Joined: Sat Jul 16, 2005 8:39 pm
Posts: 56
Location: Moonee Ponds Victoria
Or maybe flying cap psu?

Regards
James

_________________
Image


Top
 Profile  
Reply with quote  
PostPosted: Thu Dec 04, 2008 5:23 pm 
Offline
Account disabled on owner's request

Joined: Wed Dec 29, 2004 8:31 pm
Posts: 899
Hi,

His big invention seems like a total rip off of "never connected"

http://www.never-connected.com/

Right down to the sales pitch. It's a joke too, but their punchline is it's patented.


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 30 posts ]  Go to page 1, 2  Next

All times are UTC


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group