Zen -> Cen -> Sen, evolution of a minimalistic IV Converter

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#761
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
 
#762
heb1001 said:
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.
Click to expand...

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.
 
#763
Spice model for floating op-amp?

bcarso said:
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
Click to expand...

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: http://www.diyaudio.com/forums/solid-state/81858-spice-macro-model-floating-supply-opamp.html for which the transient analysis of the circuit fails with voltages showing in the 100,000s - not sure where they came from.
http://www.diyaudio.com/forums/solid-state/81858-spice-macro-model-floating-supply-opamp.html
 
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#764
heb1001 said:
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: http://www.diyaudio.com/forums/solid-state/81858-spice-macro-model-floating-supply-opamp.html for which the transient analysis of the circuit fails with voltages showing in the 100,000s - not sure where they came from.
http://www.diyaudio.com/forums/solid-state/81858-spice-macro-model-floating-supply-opamp.html
Click to expand...

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.
 
#765
heb1001 said:
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.
Click to expand...

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.
 
#767
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
 
#768
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
 
#770
> 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
 
#774
I have been asked by PM to post a schematics of SEN IV using LU1014.

If you compare the DAO (standard) follower to a 2SK170 source follower,
you can use the same substitution in the SEN IV V18 circuit to make up your own schematics.
It is easy enough.

If you post it I shall have a look to see if I spot any obvious mistakes.
Otherwise I stick to my lessons learned and will no longer post any schematics without testing myself.
And I have no immediate plan for a DAO IV, unlikely this year.

Bear in mind you will need 48V 250mA floating supply or battery plus large enough heatsinks per single ended SEN IV.
Will undoubtedly be a spectacular project.
So don't let me discourage you.
I will be quite interest to see it working. 🙂


Patrick
 
#775
Interesting design, especially those heatsink :hypno2: where do you buy it? I'm reading first pages, but still many pages to go 🙂

I still have around 40pcs 2SK170 from dcb1 project, and I just realize how expensive 2SJ74 😱 so for AD1865, should built ZEN or SEN?
 
#777
SEN V18 current draw

I'm testing my new regulated XEN battery supplies for the SEN V18 and I'm looking for an appropriate dummy load. How is the approximate current draw calculated? The sum of the Idss of the FET's?

Cheers,

Nic
 
#779
heb1001 said:
Have you actually tested that using regulators offers an improvement? What's the benefit?
Click to expand...
Well - I have to make the regulated supply to compare - don't I😉
I don't expect anything dramatic as it is sounding so damn good right of the batteries. I had to make the charger circuit anyway and adding in regulation is really just for the fun of it. I doubt it hurts......
Cheers,
Nic
 
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