Class D Vs Class I (Balanced Current Amplifier)

Was wondering if any electronics engineers could offer some technical opinions
on the subject.

Which topology is better, class-d, class-i or even class-h ?

From my limited experience in audio, I've learned that most arguments come
down to application, but since they're all a form of digital, perhaps there is
a "better" choice. When I say better, I'm thinking manufacturing costs,
reliability, sound quality and THD etc. Perhaps Class-I is just marketing hype?

I've been toying with the idea of contracting out some designs, hence the question. Application would be _big_ sound...pubs, clubs, events
and competition car audio. The dream is something along the lines of crown's
i-tech and JBL's 6KW beast http://www.caraudiomag.com/specialfeatures/0205cae_jbl_6000_watt_crown/photo_03.html ....probably not quite so big, but along competition lines.
 
Well,

Class-D is Classical Pulse Width Modulation switching amplifier...Its output consists of Mosfets in Pushpull manner and a series connected Inductor filter to retrieve the audio wave from the Pulsating signal through averaging effect of inductor.Efficiency is around 90-95%.....

Class-I is just another hyped version of Class-D but it uses two large inductors for storing energy as the both output mosfet conduct at same time, though absence of dead-time, but its high frequency response is not good one.....Its also Known as Balanced Current amplifier [BCA]...

Class-H is actually a Class-AB amplifier whose supply rails were switched from lower level to upper level in accordance with the output voltage required to get efficiency.....2 Tier Class-H is Efficient upto
65-75% with music signals


I have developed both Class-D and Class-H amplifiers......

regards,
K a n w a r
 
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TOINO said:
When I look for “class-I” schematics, the only thing I see is two Buck regulators bridge connected…
One positive the other negative, like class-B analog amplifier.

Could some body tell me if I need eyeglasses, please..?:(

Hi TOINO,

www.crownaudio.com/pdf/amps/137234.pdf
www.crownaudio.com/pdf/amps/137331.pdf


jmartins said:
Where can I read more about Class-H ?

There is schematics ? websites???

regards,
João

In mY Thread

http://www.diyaudio.com/forums/showthread.php?s=&threadid=68415

regards,
K a n w a r
 
Hi Workhorse

Yes I know all the Crown “pa-ta-ti-bla-bla”, but analysing the schematics: http://www.jblproservice.com/pdf/VerTec Series/Main Assembly Schematics.pdf
Is just two Buck converters assembled like a class-AB output “linear” power amplifier.
On class-AB you have 1 power transistor for positive part of signal and another for negative.
Positive one could only source current to load=Class-I positive Buck converter.
Negative one could only sink current from load= Class-I negative Buck converter.
For my eyes, class-I looks like a switched class-AB counterpart in which the output transistors are Buck-converters.
Even the modulation scheme is in a way to simulate the linear class-AB amplifier.
 
Hi Workhorse

Shure that both mosfets switch with complementary signals, but the output is taken after the coils.
Each switch group, positive and negative, are complementary after the coil.
Please note that at this node (where the two coils join to form the output signal) only one switch group sinks our sources, never both at some time.
Otherwise you have catastrophic cross-conduction (like in class-AB linear counterpart).

RAM is robust, but conventional…
It is like this one, http://www.audio-circuit.dk/PDF/Schematic Design_ LYNX_v2-1B.pdf
but with class-G rails.
 
The Class I just seems to me to be what is also called PWM Class BD. Both TI and National make 5V versions using that modulation class. Rockford Fosgate got a patent on some improvements to Class BD. Here is the patent. It is an interesting read and talks about Classs AD and BD.

Hmm, can't attach patent because the file is too big. The patent number is: 6,097,249, dated Aug 2000

-SL
 
I read in one of their articles on their website that:

"A class-I amp handles reactive (inductive) speaker loads easily and gracefully. It re-uses the energy returned from the speaker rather than dissipating it as heat or forcing the amp into premature current-limiting."

I wonder how this is accomplished?
 
I am talking about the Crown “class-I” switch arrangement because it seems to me as a regular Buck converter (or two).

You are right! Its only 2 paralelled (and 2 sets bridged) Buck converter. But this fact has consequences!

- dead time distortion can be avoidable
- switching loss and EMI is less, because of lower Qrr of discrete diode
- possibility of using higher voltage MOSFET
- possibility of 5 level modulation (in bridge)

Hence this is the best arrangement for very high power.
 
Hi rmsaudio
this is the "class-I" patent
http://www.freepatentsonline.com/5657219.pdf

Hi Pafi
Thanks for your comments.
I need some time to think about it, as I am a learner in these things.
Anyway, a first glance, I honestly can’t see nothing on “class-I” patent who could be really patented.
My meaning is that the Buck-converter and BD-modulation are in fact public domain at the time the patent was granted.
See for example this one: http://www.freepatentsonline.com/5025360.pdf is the some arrangement...
About the topological similitude’s I found in “class-I” / class-AB(linear) the “class-I” has also “bias adjust” to compensate for crossover distortion…?!
 
I guess it is a pet peve of mine but I hate when companies make a new class of amplifier when, in fact, it is just some improvement to an existing class. Class I and Class T to me are nothing more than marketing, just more BS. Sure they might do some things other Class D's haven't done but there are tons of Class AB designs that do some things different. Drives me crazy. Who determines a Class? Problem is no one, just name it if you want., take out a trade mark out and BOOM, new class of amplifiers that are not really much new to the basic idea/theory of an existing class.

I will read their patent but I think they have just a different way to accomplish a Class BD design that is still Class BD.

Stupid marketing.

-SL