Zen -> Cen -> Sen, evolution of a minimalistic IV Converter - Page 77 - diyAudio
Go Back   Home > Forums > Source & Line > Digital Source

Digital Source Digital Players and Recorders: CD , SACD , Tape, Memory Card, etc.

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
Reply
 
Thread Tools Search this Thread
Old 12th April 2012, 03:58 PM   #761
qusp is offline qusp  Australia
diyAudio Member
 
qusp's Avatar
 
Join Date: Oct 2009
Location: Brisbane, Australia
thanks, covered for the charger, using a highish end Cellpro 10XP which can charge them in about 10-20 mins if I dare =) so I just need to switch it over, it has USB connection so I could conceivably work something out there, or since it automatically recognises when a battery has been connected and what type, I could just switch it on when its looking like it might be needed soon. if I was going to build something from scratch I would use the

LTC4156 and a few mosfets, or the Ti bq24105/25 EVM modified for LiFePo4 like in SLUA443. cant really have relays in the charge path, it would screw with the battery balancing and it would take a serious relay, or a fet used as switch to cope with the current. it would have to disconnect from the SEN, but be connected to the charger the whole time, which means the relay would screw with the supply impedance, though I gather thats not so important here, so that would be the way to go
  Reply With Quote
Old 12th April 2012, 11:19 PM   #762
heb1001 is offline heb1001  China
diyAudio Member
 
Join Date: Sep 2011
Quote:
Originally Posted by heb1001 View Post
I think the SEN circuit has good normal-mode PSRR and a balanced SEN has good common-mode PSRR for correlated common mode noise in the two power supplies of the balanced halves.

My problem I think was that there was no correlation in the SMPS switching noise between the two different PSUs on the two balanced halves and a component of this noise is common mode so it got through.

A single SMPS using an output transformer with two output windings for the two floating supplies of a balanced pair might be a lot better since the switching noise would be correlated and would cancel out.
I realized that my +-12V SMPS had the required two output windings and I could use the -12V supply the wrong way around to get two floating supplies from the same transformer so I tried this out just to see.

The result: there is significantly less high frequency switching noise than before. With the servo of #674 the noise from the speakers oscillates between a slight hum and a slight buzz. It does go through a point where it is pretty quiet though so maybe with a better servo it might be a usable solution.

It's certainly a good test of the servo.
  Reply With Quote
Old 13th April 2012, 02:59 PM   #763
heb1001 is offline heb1001  China
diyAudio Member
 
Join Date: Sep 2011
Default Spice model for floating op-amp?

Quote:
Originally Posted by bcarso View Post
Sometimes Bode plots lie, so transient response simulations are really the safest.

I should qualify my statement a bit: if there is sufficient loop gain and two close poles, you will see ringing. But an integrator followed by a little passive lowpass with a different tau may be a stable solution. This also filters out some of the broadband opamp noise, which appears at the output of a Sallen-Key lowpass.

If you get a complete schematic with real opamp parts I could take a look at it in sim, although I'm a little busy right now.

Brad
I'd like to learn how to do the simulation myself.

What would be useful though would be an accurate spice model of a good op-amp (I've got LME49710 and JRC 2114D) which works on a floating supply with no internal connections to ground.

If that happens to be easy for you it would help me a lot.

I found this one: Spice Macro Model for floating supply opamp for which the transient analysis of the circuit fails with voltages showing in the 100,000s - not sure where they came from.

Last edited by heb1001; 13th April 2012 at 03:29 PM. Reason: Found a floating op-amp model - doesn't work.
  Reply With Quote
Old 13th April 2012, 03:52 PM   #764
bcarso is offline bcarso  United States
diyAudio Member
 
Join Date: May 2005
Location: Canoga Park, California
Quote:
Originally Posted by heb1001 View Post
I'd like to learn how to do the simulation myself.

What would be useful though would be an accurate spice model of a good op-amp (I've got LME49710 and JRC 2114D) which works on a floating supply with no internal connections to ground.

If that happens to be easy for you it would help me a lot.

I found this one: Spice Macro Model for floating supply opamp for which the transient analysis of the circuit fails with voltages showing in the 100,000s - not sure where they came from.
Most simulators do a very poor to nonexistent job of coping with the power supply pins of op amps, unfortunately. I've gone as far as constructing entire op amps from the schematics provided by the manufacturers, with suitable substitutes for multiple-collector and multiple-emitter transistors, when I really had to include the power supply behavior.
  Reply With Quote
Old 16th April 2012, 08:42 AM   #765
heb1001 is offline heb1001  China
diyAudio Member
 
Join Date: Sep 2011
Quote:
Originally Posted by heb1001 View Post
I realized that my +-12V SMPS had the required two output windings and I could use the -12V supply the wrong way around to get two floating supplies from the same transformer so I tried this out just to see.

The result: there is significantly less high frequency switching noise than before. With the servo of #674 the noise from the speakers oscillates between a slight hum and a slight buzz. It does go through a point where it is pretty quiet though so maybe with a better servo it might be a usable solution.

It's certainly a good test of the servo.
I did a listening test on this and despite the lower noise than the solution with the separate SMPS PSUs the sound was awful. Measurement showed a lot of distortion too.

The best PSU option I've found so far are the cheap regulated 12V supplies.

I think these are good because they are double insulated with no connection to ground and use separate bobbins on the transformers.

My balanced SEN with these supplies sounds good enough to listen to but doesn't measure that well (PSU noise at about -90dB).

I'm heading in the direction of using the SMPSs I have to charge NIMH packs using the charger circuit suggested by EUVL.

NIMH for 4 floating supplies are going to be expensive though.
  Reply With Quote
Old 16th April 2012, 11:05 AM   #766
NicMac is offline NicMac  Italy
diyAudio Member
 
NicMac's Avatar
 
Join Date: Feb 2009
Quote:
Originally Posted by heb1001 View Post
NIMH for 4 floating supplies are going to be expensive though.
Not exceedingly so - I found 10 pcs. of 9V 280 mAh NiMH batteries for about 40 euro.
  Reply With Quote
Old 19th April 2012, 09:16 PM   #767
NicMac is offline NicMac  Italy
diyAudio Member
 
NicMac's Avatar
 
Join Date: Feb 2009
Default xen nimh charger

Patrick,

I will be trying the xen trickle charger circuit you presented in post #612.
For 3x 9V batteries (total: 21 cells, 840 mA) the spreadsheet tells me to use V_ch = 30V.
I have a 32V 2.5A smps that I would like to use for the job.
Is this higher voltage acceptable or can I change the value of R_ch to make it acceptable?
Or maybe it would be better to dump the voltage using 1-2 pcs. of 1N4007 in series with R_ch.

Cheers,

Nic
  Reply With Quote
Old 20th April 2012, 01:12 AM   #768
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
I assume they are AAA NiMHs. So your max. current should be < 200mA (at the start when they are empty).

Why not use a high power LED (red), such as OSRAM Golden Dragon Plus LH W5AM.
They will drop 2.2V and take 400mA max.
You probably need a small heat sink (0.5W), but it is a lot more interesting than 3x 1N4007.
And you can also see how much charging current you are having.




Patrick
__________________
xen-audio.com
  Reply With Quote
Old 20th April 2012, 08:08 AM   #769
NicMac is offline NicMac  Italy
diyAudio Member
 
NicMac's Avatar
 
Join Date: Feb 2009
Very bright idea Patrick

I will try this. Just have to figure out how to heat sink this component package.

Thanks again for the illuminating suggestion

Nic
  Reply With Quote
Old 21st April 2012, 03:58 AM   #770
EUVL is offline EUVL  Europe
diyAudio Member
 
Join Date: Oct 2003
> Just have to figure out how to heat sink this component package

If the substract is ceramics you can use arctic silver to glue it to a sink (>0.5W).
Just make sure the silver expoxy does not get into the electrical connections.

If not there is also an insulating epoxy from Arctic Silver call Arctic Silver Ceramics.
Make sure you get the glue and not the thermal paste (grease).


Patrick
__________________
xen-audio.com
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
FOR REGA Turntable>>> The heavy weight + Vta adjuster+ceramic ball prooptiki Swap Meet 1 22nd May 2010 05:57 PM
Multi-DAC: Lynx AES16 -> DIR9001/SRC4392 (-> SRC4192) -> PCM1794A novec Digital Line Level 11 11th May 2010 11:57 AM
> Audio <> music <> quick <> synergy <> angst>? rick57 Everything Else 0 4th May 2007 04:03 PM
&gt;&gt;&gt; cheap 50,000uF 60V capacitors here &gt;&gt;&gt; Lubomir Swap Meet 0 1st February 2007 03:36 PM


New To Site? Need Help?

All times are GMT. The time now is 06:01 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2