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Class D Switching Power Amplifiers and Power D/A conversion

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Old 8th May 2004, 10:03 PM   #11
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Default amp man can!!!

amp_man !!!!

Nice to see people sharing their designs, good one !! Also wanted to start an "Open" initiative for ClassD, ClassH and SMPS. If you need webspace just shout.
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Old 10th May 2004, 05:45 AM   #12
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hi

wishing you guys all the best , with class - d

suranjan
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Old 11th May 2004, 12:49 AM   #13
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Default Re: Re: Commentable Thoughts

Quote:
Originally posted by amp_man_1


Well , I remember that their is no need to reference the feedback to the center tap of transformer in case of feedback taken from H-bridge and fed to difference amp.
Secondly, only single supply will do the entire job for the amp, Thats why No level shifter, no Dual Supplies.

With Regards
Ampman
Typo in my last post: The feedback path is NOT necessary in a full bridge design, but it lowers THD

With a bipolar design or a single rail design, you can still take the voltage from between the two mosfets on each side of the bridge and feed it to the difference amp. As mentioned before the voltage needs to be stepped down for higher voltage designs.
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Old 11th May 2004, 11:25 AM   #14
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As far as level shifting and gate drivers go, has any consideration been given to transformer coupling the drive (small ferrite toroids)? I have seen this used in a number of commercial amps, including Peavey's latest line, and would eliminate the need for level shifting, special gate driver ICs with their negative rail referencing, etc. As only around 20turns of wire is required, winding these would be easy and cheap.

Cheers
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Old 11th May 2004, 12:08 PM   #15
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Quote:
including Peavey's latest line,
Were these of the DPC type ? I assume, since the trafo principle won't work with a real PWM signal. In the DPC case however this transformers always carry a 50% duty-cycle signal.

It would be possible however to make level translation with x-formers with some additional tricks.

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Charles
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Old 16th May 2004, 12:01 AM   #16
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Arrow Commentable Thoughts

Ok Guys, Can I say that There is no need of feedback in Full-Bridge topology in case of Class-D amp.
Complimets
AMPMAN
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Old 18th May 2004, 11:52 PM   #17
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Arrow Commentable Thoughts

To generate a Triangle one must use high speed opamp such as LM6172 100MHZ type.
IS there any other viable substitute other than this is available?
Secondly , The concept of Complementary Comparator is I think is very Good to utilize to generate out of phase PWM signals, instead of using CMOS IC to do that job.
PLZ Comment on it?
Can we rely on the gate capacitance of mosfet to implement Deadtime as The LT schematic [crest audio] illustrates it.
With Compliments
AMPMAN
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Old 19th May 2004, 01:51 AM   #18
bknauss is offline bknauss  United States
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Quote:
Ok Guys, Can I say that There is no need of feedback in Full-Bridge topology in case of Class-D amp.
No, you can't say there is *NO* need for feedback in a full bridge design. Is it necessary, no, but again, it will keep the THD down.

For the triangle generator, a 555 timer should work up to about 500kHz.

If you use the IR FETs that are made for Class D amps, you shouldn't have to worry about the internal capacitances.

Hopethat helps
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Old 19th May 2004, 07:11 AM   #19
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Arrow Commentable Thoughts

Quote:
Originally posted by bknauss
For the triangle generator, a 555 timer should work up to about 500kHz.
Hopethat helps
Acc to my opinion 555 Timer can only generate ramp i.e. Sawtooth wave not the triangular wave which has double sampling resolution than sawtooth.
If I am wrong can u illustrate a circuit for this.
With Compliments
AMPMAN
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Old 20th May 2004, 12:08 AM   #20
bknauss is offline bknauss  United States
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Sorry, I was incorrect about the 555 timer. I had a friend that intended on using this, and I thought he said it worked for 400kHz, but the basic triangle wave generator circuit was used.

There is a Maxim signal generator, but it is fairly terrible. I personally saw the waveforms for a triangle wave at 400kHz, and it was very noisy and inaccurate.
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