State of the Art for Tracker/Down Converter?

[Dave Zan]

I have started to look at switch mode power supplies that track the audio, a la Bob Carver amps, and later Lab.Gruppen and others.
The use is a home theatre system with tri- and bi-amped speakers, so there's a dozen or so power supplies to build, hence a simple IC based solution is attractive.
What is the current state of the art in circuits, ICs and power semiconductors for this?
The trend in industrial SMPS seems to be towards Zero Volt Switched circuits.
My first impression is that it seems attractive for Audio too, but I see there are some tricks and traps with this technique.
Standard MOSFET or bipolar power semiconductors still look cost effective for < 600 V but perhaps there are new SiC or fancy semiconductors that I should consider.
Any comments appreciated, except that I should just use Class D amps - different discussion!

David

[wg_ski]

The Labgruppen and the similar Yamaha EEEngine don’t require special power supplies per se. They have simple self-oscillating buck converters inserted into each rail of each channel. They don’t require a ridiculous number of parts or anything hard to find and are all discrete. The actual power supply can be just a big toroid - or switcher if you’re up to building it.

The early Carver circuits were variations of class G and H, which require multiple tapped power supplies. Easy to build and get working, not quite as efficient as the tracking supplies but still beat regular class B by a huge margin. You can easily build the euquivalent of the Carver “cube” amps with a regular power supply instead of that tricky thyristor controlled supply and it would be just as efficient (and not eff up as easily). Later Carver amps adopted topologies similar to the Labgruppen to get even more efficiency.

[MorbidFractal]

Originally Posted by Dave Zan

Any comments appreciated, except that I should just use Class D amps - different discussion!
David

Not sure about your reference to ZVS and < 600V devices. That sounds like off-line LLC converter stuff.

You should just use Class D amps....


Tongue in Cheek. Synchronous Buck driving analogue bridge amplifiers would appear to be the way to go. Synchronous Buck is, in effect, half bridge Class D with the bottom Mosfet switching to circuit ground.

You can get control ICs that will drive external Mosfets.

Buck Controller External Switch | Products | Step-Down Buck | TI.com

Buck Controller External Switch | Products | Step-Down Buck | TI.com

Other manufacturers are available.

[Dave Zan]

Originally Posted by MorbidFractal

Not sure about your reference to...< 600V devices.

I am interested if there are improvements to semiconductors that would be useful for this application.
I know there has been a lot of work on SiC but practically all for the industrial power market >600V, so not suitable here AFAIK.
There is also GaN but it is not really mature, also AFAIK.
There have been improvements in Si tech, super junction MOSFETs and even power JFETs.
So I wondered if anyone familiar with the latest state of the art could recommend the best choices at this time, save a search of manufacture's brochures.

Best wishes
David

[Dave Zan]

Originally Posted by wg_ski

...don’t require special power supplies per se.

I am not fully informed about all the history, especially of the Yamaha and various versions of the Carver.
The Labgruppens appear not to have a conventional power supply, just a switcher.
But maybe different models used different tech so it would be informative to learn more.

Best wishes
David

[wg_ski]

Labgruppens do have switching supplies - but so do a lot of amps, including regular old class AB. The only thing unconventional about the supplies is that they are made to take a pounding and have PFC. So do high end gaming computer supplies. The price reflects it - the amps are very expensive. The tracking downconverters are part of the amplifier, and operate independently from the “supply”. You could build the same amp and run it off a big 60 Hz toroid. It would be big and heavy but roughly the same efficiency, other than not being PFC. The tracking downconverters or some variant thereof could also be grafted onto your favorite class AB amplifier design if you have something you really like and want to keep the same sound.

[Dave Zan]

Originally Posted by wg_ski

... downconverters are part of the amplifier, and operate independently from the “supply”...

That was not what I understood, it seems less efficient and more complex, perhaps this biased me to misunderstand, or perhaps this varied from model to model.
What model(s) does your comment cover, do you have a link or reference?

Best wishes
David

[Dave Zan]

Originally Posted by wg_ski

... downconverters are part of the amplifier, and operate independently from the “supply”.

OK, the schematic I found does show this, hmm.
Does anyone make an amp where the SMPS tracks the audio?
Seems simpler and potentially more efficient.

Best wishes
David

[traderbam]

How is a SMPS that can react at audio frequencies not a class D amp? Why not use class D amps, or a variant of, as power supplies for a linear amp?

[Dave Zan]

Originally Posted by traderbam

How is a SMPS that can react at audio frequencies not a class D amp?

A Class D amp is powered by a DC supply, a SMPS is powered from the mains.
Or that's how I use the terms in this context.
Obviously very similar but the different uses do lead to some difference in approach.
Like Power Factor Correction and isolation for the SMPS.
Also SMPS are normally optimized to respond to variations in load current demand whereas Class D track a variable "input" (required output).

Why not use class D amps, or a variant of, as power supplies for a linear amp?

Yes, this is discussed in an informative thread in "Solid State" by Damir Verson (DadoD).
That thread is on hold while he is out of action so I came to this forum to learn from a different perspective.
I'm a little disappointed in the lack of interest but at least it's educational to have to work it out from scratch.

Best wishes
David