Is this really working?

[lumanauw]

Patent #6844777 or #6937092, are these patents really working in reality (for high quality classD amp)?

Isn't that transformer coupled signal has a certain minimum pulse width to work well?

If it works, we can make high quality, high power classD with only IRFZ44

 

[classdphile]

For a single advantage such simplicity is not without cost. Why not wrap a quality control loop around it, if it's estable enough pyre can manufacture it and sell it back to us. Or is this better seen as one of those open loop things.

 

[lumanauw]

If the output always 50%-50% there will be no trouble. But for small/large duty cycle, what will happen? Considering the set-reset of Volt-Second area.

 

[darkfenriz]

LOL

Since the Switch-mode transformer cannot transform low frequency audio signals, then one should use heavy tube-style transformer.
Then why class-D ??

Authors don't seem familiar with the existance of DC-DC converters (in 2003).

 

[luka]

LOL

LOL indeed

 

[phase_accurate]

It is theoretically possible to build such an amplifier but the technical requirements for the transformers wouldn't give any advantages over ANY other amp topology.

Apart from that this has been discussed in web forums etc so many times that it shouldn't be patentable in the first place.

Regards

Charles

 

[lumanauw]

In patent #6844777, the key is fig.1 to fig.2. Full bridge classD is being isolated by a transformer. If fig.1 is working at 400khz, then the transformer in fig2 should be built by -2 material (maybe T130-2).
Then the carrier is eliminated by L-C like usual.
Then we can move to fig.3, the push-pull one.
At first glance, it seems to be working.
But when I experiment with transformer working with very narrow (or very wide) duty cycle, the weakness of transformer appear. I cannot fool the Volt-Second product of a quadrant.

 

[lumanauw]

If this really works, it would be very nice. I can make +/-150V swing amp only with IRFZ44N (don't have to look for quality high voltage mosfet), in push-pull mode (like primary of car SMPS) without the need for level shifter etc Just adjust Np:Ns.

 

[thespeakerguy]

I built an xformer Class D

I tried similar in the lab once. Used a MAX4295 open-loop Class D amp, driving N FETs. It dis work, doing aabout 4 watts into 8ohms at 1kHz or so. Anywhere below that it died, because this becomes close to DC flowing through the core.

With a large enough core it could be improved. it should have some feedback to correct for FET, voltage and xformr non linearities.

An alternative is to reverse the current in the transformer by having active rectifiers. This way no DC in the core.

 

[lumanauw]

Hi, thespeakerguy,

Anywhere below that it died, because this becomes close to DC flowing through the core.

That's an important restriction

An alternative is to reverse the current in the transformer by having active rectifiers. This way no DC in the core.

Could you tell more about this?

 

[phase_accurate]

In order to work the x-former would need to work from the lowest audio frequency up to higher than the carrier frequency. This would be extremelly difficult to build and also be bulky and espensive.
That's why I said there would be absolutely no advantage to it.

Regards

Charles

 

[lumanauw]

-2 material won't work for this?

 

[raintalk]

You would be able to sell something like this to the musical amplifier industry. Just say the transformer is for "warmth".

http://www.warwickbass.com/amps/JHpoweramps.htm

 

[fredos]

Funny...I think I will built a class d amplifier with a heater inside to "warmth" the sound too... And with output transformer to add weight too!

 

[darkfenriz]

Re: I built an xformer Class D

An alternative is to reverse the current in the transformer by having active rectifiers. This way no DC in the core.

How?

If there is no low frequency through core, then you have to store energy somewhere. You will probably end up with synchronously rectified SMPS + PWM amplifier equivalent this way.

 

[phase_accurate]

There is a circuit called "ampliverter" which is actually an SMPS whose output voltage is following the magnitude of the audio signal and that uses synchronous rectification to reconstruct the polarity of the output signal.

Regards

Charles

P.S.: I don't like it BTW

 

[thespeakerguy]

secondary switches

the way to get it to work is to reverse the current in the transformer at every switching cycle, or at least at above 50kHz or so.

The output of the xformr would need a reversable full bridge setup

 

[lumanauw]

I remember that a variation of Cuk converter can make bidirectional energy transfer. Patent#4186437. http://ece-www.colorado.edu/~rwe/papers/Powercon5.pdf

BTW, what is this patent about? #7057905

 

[kASD]

If the core has enough Iron like CRGO stack lamination, it can do the magic.