class D amp

On Sun, 13 Aug 2017 15:19:33 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

>On Sun, 13 Aug 2017 15:08:07 +0100, Piglet wrote:
>
>> Ouch! Phil you are one of the very few really knowledgeable contributors
>> here
>
>LOL!:-D You haven't been here very long then, Piglet. Allison is about 
>the most ignorant and bigotted arsehole who ever posted here. When he 
>fucks up (which is almost constantly) he attacks anyone who attempts to 
>correct him. KF him. You will find life much more pleasant without the 
>ravings of this conspicuously autistic retard to content with.

Yep, and he's totally wrong, you can do the same asymmetry check at
the driver devices.
		
                                        ...Jim Thompson
-- 
| James E.Thompson                                 |    mens     |
| Analog Innovations                               |     et      |
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| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
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             I'm looking for work... see my website.

Thinking outside the box...producing elegant & economic solutions.

On 08/13/2017 11:19 AM, Cursitor Doom wrote:
> On Sun, 13 Aug 2017 15:08:07 +0100, Piglet wrote:
> 
>> Ouch! Phil you are one of the very few really knowledgeable contributors
>> here
> 
> LOL!:-D You haven't been here very long then, Piglet. Allison is about
> the most ignorant and bigotted arsehole who ever posted here. 

That's a little bit unfair--Phil's worth listening to on the subject of 
audio gear when he's on his meds.  Some folks find his rants amusing, 
though I'm not one of them.

Cheers

Phil Hobbs

-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

"Klaus Kragelund" <klauskvik@hotmail.com> wrote in message 
news:ecfdc33d-636b-40d6-be9a-22eae6bf760d@googlegroups.com...
> Staircase saturation can be difficult to manage with full confidence

FYI, nothing is staircasing.  At least, whoever came up with it, chose a 
terrible name.

Staircase flux would only happen if you apply "pulsed DC" (i.e., a unipolar, 
constant voltage source) to a zero-resistance winding.

Note that's not /switched/ DC, which allows flux to return to zero 
(flyback).  Because the source isn't constant voltage in that case: it 
switches between constant voltage and constant current (the current is 
zero).

Even resistance will "tilt" the staircase, so that it goes backwards during 
each "tread", and after a few L/R time constants, it will simply be ripple: 
or, if you like, it'll be a very "tilted" staircase that doesn't climb at 
all.

So it would be very difficult indeed to have a circuit generate a proper 
staircase.

Maybe "staircase" is meant to mean, if you sample the flux at a consistent 
point each cycle -- that way if there's an imbalance, it's clearly rising; 
but that's still a poor description, because it's no more a staircase (zero 
order hold) than a sampled ramp, or any other of infinite functions that 
happen to have that result when sampled at a particular time.

The phenomena I described seems to have little to do with the switching 
frequency or duty cycle (given that DC balance is good), and more to do with 
material properties.  It took on the order of 10k cycles to drift off 
towards saturation.  It's not obvious if the saturation was the same 
polarity each time (hmm, I recall measuring inverter current, but I don't 
remember which phase was saturating, if it was consistent or not).  The 
timing was inconsistent as well; sometimes it would saturate in a few 
seconds, sometimes it would come and go, then go back to saturation.

Not that that phenomena is terribly common either, but it's a material thing 
more than a circuit thing.

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com 

On Sunday, August 13, 2017 at 7:23:05 PM UTC+2, Tim Williams wrote:
> "Klaus Kragelund" <klauskvik@hotmail.com> wrote in message 
> news:ecfdc33d-636b-40d6-be9a-22eae6bf760d@googlegroups.com...
> > Staircase saturation can be difficult to manage with full confidence
> 
> FYI, nothing is staircasing.  At least, whoever came up with it, chose a 
> terrible name.
> 
> Staircase flux would only happen if you apply "pulsed DC" (i.e., a unipolar, 
> constant voltage source) to a zero-resistance winding.
>

Staircasing, or a better name for it flux walking. The name staircasing comes AFAIK from push pull converters, when if you observe the current in one winding, it will show a semi staircase look cycle to cycle (envelope)

It is not an effect caused by the magnetics, but caused by unequal volt seconds product by the converter control. For example in a push pull converter with non equal duty cycle for push and pull, or from other non-linear effect (RDSon, matching of push/pull paths etc)

It can be remedied by deadtime and negative feedback of the paths (increasing resistances, bifilar windings etc)

A current mode converter can also remedy the effect, but also cause it to be worse, due to interaction of the coupling capacitor and the current mode control, which makes the problem a lot worse

See page 7 for explanation:

http://www.ti.com/lit/an/sprabw0b/sprabw0b.pdf
 
Cheers

Klaus

Cursitor Doom wrote:

-------------------------

> Piglet wrote:
> 
> > Ouch! Phil you are one of the very few really knowledgeable contributors
> > here
> 
> LOL!:-D You haven't been here very long then, Piglet.

** Long or longer than you - asshole. 


> Allison is about 
> the most ignorant and bigotted arsehole who ever posted here. When he 
> fucks up (which is almost constantly) he attacks anyone who attempts to 
> correct him. KF him. You will find life much more pleasant without the 
> ravings of this conspicuously autistic retard to content with.
> 

** How fully !!.

 The CD lunatic troll just described himself to perfection.



...  Phil 

Phil Hobbs wrote:
 
> 
> That's a little bit unfair--Phil's worth listening to on the subject of 
> audio gear when he's on his meds. 
>
>

** The scheme JL posted *IS* a common audio circuit - the fact the amp is class D seems to have you all going in tiny circles and thinking about SMPS topologies. 

An audio power amp coupled directly to a iron core transformer is something I am very familiar with and so KNOW the issues. 

IMO JD would be wise to drop the class D IC as it creates additional problems  and use a class AB linear amp. 

It is obvious that none of you here have a clue. 


....  Phil 

On Monday, August 14, 2017 at 1:23:51 AM UTC+10, Cursitor Doom wrote:
> On Sun, 13 Aug 2017 15:08:07 +0100, Piglet wrote:
> 
> > Ouch! Phil you are one of the very few really knowledgeable contributors
> > here
> 
> LOL!:-D You haven't been here very long then, Piglet. Allison is about 
> the most ignorant and bigotted arsehole who ever posted here.

Cursitor Doom ignores his own claim to the title. Phil Allison does know what he is talking about when it comes to audio, and Cursitor Doom is just too prig-ignorant to be aware of this.

Phil does have short fuse, and doesn't suffer fools (or anybody else who dares to disagree with him) gladly, but ignorance isn't his problem.

One can't say as much for Cursitor Doom.

> When he fucks up (which is almost constantly) he attacks anyone who attempts  
> to correct him. KF him. 

Phil fucks up very rarely, but reacts violently to even minor differences of opinion.

> You will find life much more pleasant without the 
> ravings of this conspicuously autistic retard to content with.

Kill-filing Cursitor Doom would be much better idea. You'd miss absolutely nothing worth reading.

-- 
Bill Sloman, Sydney

bill....@ieee.org wrote:


> 
> 250mH would resonate with 0.63uf at 400Hz, 1.62uF at 250Hz.
> 
>

** JL's inductance figure is a nonsense, the tranny is toriodal with no effective air gap so the L value varies widely with magnetisation. 

https://dl.dropboxusercontent.com/content_link/Ha8ZedbZ7p6bz2cb30TWJveulbmmOMzeuMNXGdd73SiJiEhGWoWygBm56ro1c12g/file

If JL just used a coupling cap, say two 1000uF 35V electros back to back, all DC offset issues disappear. 

If he clipped the input signal so the amp never clips and followed that by even a 6dB/oct HPF set at 300Hz - another bogey is gone. 

The final bogey, inrush surges, can be *eliminated* by using a tranny with double the primary voltage rating at 300Hz his class D amp can deliver. 

Yep, AC supply transformers do not surge at switch of if run at half rated voltage or less. Fact.


....  Phil 

"Klaus Kragelund" <klauskvik@hotmail.com> wrote in message 
news:18bcf2a7-d032-4c1f-b449-d40abb9be123@googlegroups.com...
> A current mode converter can also remedy the effect, but also cause
> it to be worse, due to interaction of the coupling capacitor and the
> current mode control, which makes the problem a lot worse
>
> See page 7 for explanation:
>
> http://www.ti.com/lit/an/sprabw0b/sprabw0b.pdf

Of course, you don't use peak current mode control in a half bridge 
converter.  A current source into a coupling capacitor is just as dumb as a 
voltage source (PWM imbalance) into a PP or bridge inverter.  :-)

Peak current mode works nicely for PP (e.g., UCC3808).  Curiously, I once 
breadboarded the equivalent circuit of the '3808 using discrete gates; it 
suffered from subharmonic instability.  Not fatally, it didn't walk -- it 
can't walk, because PP is DC coupled -- but it did, shall we say, veer to 
the side of the walkway.  Unsure if the '3808 just has better matched timing 
(likely!), or if it has additional logic to control imbalance.

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com 

John Larkin wrote...
>
>I want to build an AC source to test synchros/resolvers/RVDTs. The
>target is 400 Hz 30 VRMS at maybe 30 VA, but we might want to simulate
>aircraft "wild power" and drive LVDTs, so maybe 250 Hz to a few kHz.
>
>I'm thinking of using half of a TPA3251 audio amp and a step-up
>transformer. Like this maybe:

 Skip the transformer, get a proper higher-voltage
 class D.  I like the IRS2092 chip, +/- 100V range. 
 Lots of assembled PCBs on eBay, free shipping from
 China, two-three weeks.  Just search on IRS2092.
 Choose from among the smallest wimpiest ones.


-- 
 Thanks,
    - Win