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Class D Switching Power Amplifiers and Power D/A conversion

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Old 23rd December 2009, 07:54 AM   #1
rha61 is offline rha61  France
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Default new hybrid A/D amp

D E V I A L E T

the ADH is a class A amp driving 4 class D amps with no output filter

very good reviews here in France
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Old 23rd December 2009, 09:07 AM   #2
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salesman, huh?
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Old 23rd December 2009, 10:34 AM   #3
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Class ad audio amplifier - Google Patent Search

It looks like a switching current booster for a standard linear amplifier.
Quite interesting, but keep in mind that the linear stage will have to carry (and dissipate) the whole ripple current of the switching part.
It must be the reason why the linear part has a "switching" cascode implementation.
Possibly the efficiency or maximum swing go down at 20kHz, because the class D part either injects the ripple current to linear amplifier or has a very limited bandwidth.
Another downside is the series sense resistor directly at the output, which limits maximum possible damping factor.

Otherwise it looks like a very nice hybrid in styley cases and lots of functionality.
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Old 23rd December 2009, 10:49 AM   #4
rha61 is offline rha61  France
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Originally Posted by Workhorse View Post
salesman, huh?
no , UCD user
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Old 24th December 2009, 06:38 AM   #5
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I did simulations with such a topology about 12 years ago. THD looked promising, but pure class-d is still much more interesting. Didn't expect it to be too interesting for being patented (there is even an old patent by some Australins that could probably kill this one here) back then.

Regards

Charles
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Old 25th December 2009, 08:07 PM   #6
Ltralus is offline Ltralus  Denmark
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Old 26th December 2009, 09:39 AM   #7
rha61 is offline rha61  France
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Quote:
Originally Posted by phase_accurate View Post
I did simulations with such a topology about 12 years ago. THD looked promising, but pure class-d is still much more interesting. Didn't expect it to be too interesting for being patented (there is even an old patent by some Australins that could probably kill this one here) back then.

Regards

Charles
why pure class d is still much more interesting ?
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Old 26th December 2009, 01:29 PM   #8
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Class D sets its own unique set of possibilities and challenges, contrary to numerous tricks to reduce dissipation in linear mode amplifier (class G/H, tracking rails, current boosters/dampers, ...)
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Old 28th December 2009, 06:05 AM   #9
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Well ....... let's see:

The main advantage of class-d is its efficiency.
The main advantage of conventional linear amps is that every other performance figure (apart from efficiency) can be made very good with known and easily implemented topologies.

It may thus sound logical to "marry" both of course. But now we will get an amp whose efficiency is still lower than a class-d's efficiency and which is certainly more complicated than either kind of amps alone.

A modern pure class-d amp can achieve the same small-signal- and power- bandwith - something that can't be taken for granted for many conventional linear amps and certainly not for switching/linear hybrids.

Furthermore one has to take into account that class-d is enough mature nowadays to make most conventional amps obsolete. It is only a question of a few years when pure class-d will rival the best conventional amps out there.

Regards

Charles
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Old 7th January 2010, 07:27 PM   #10
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How about 'floating' the ground rail with a class-A amplifier, needing full current capability, but at low voltage (and power-/cooling-) levels. Wouldn't this give class D power and efficiency and simplify/cheapening te class-A amplifier?
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