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Tekko 9th September 2012 11:50 AM

Tekko goes crazy
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I have today started on a output stage using mosfets that with the right PSU make over 2kW RMS power into a 2 ohm load and over 4kW peak.

The fets are joined together with busbars made outta flattened copper tubing to minimum stray inductance and maximum current transfer capability.

Now before you say anything, no this is not a serious project, it is all 100% for fun as it will not have any sort of practical use.

Heres a drawing to show how crazy i'm going :D

Tekko 9th September 2012 01:22 PM

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And here it is in reality:

DUG 9th September 2012 02:03 PM

Looks compact.

Current transfer at higher frequencies takes place away from the core of the conductor.

Research "skin effect" and "Litz wire".

Now all you need to do is to build a drive system for the FET's.

Watch for the equivalent gate charge you will need to inject (in the time allowed) to turn them on for good efficiency. This will result in a significant number of peak amps.
Thus begins the interesting tradeoff between peak drive (gate) current, final drive (gate) voltage, switching frequency, supply voltage, and even FET selection (although you have that already)

Have fun learning.


"The more you learn the less you know"

Tekko 9th September 2012 02:46 PM

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As the carrier is only 200kHz, there is not gonna be any problems with a 550nC gate charge, the IR2110 will have no problem driving these mosfets.

The igbt module i pushed to 500kHz had way higher gate charge.

The power stage is done:

ionutzxpo 9th September 2012 02:52 PM

:D interesting project tekko, a 250-300Khz carrier will be OK for fullrange audio maybe u will post the complete schematic when the circuit is complete :sing:

ionutzxpo 9th September 2012 03:06 PM

STE70NM50 is superior to STE75N50 low gate capacitance,low gate charge,faster turn on time etc

Tekko 9th September 2012 03:21 PM

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The circuit is that of my thread "simple class d amplifier"

The new power stage is now alive and kicking! :D

This was never intended as fullrange use, but it still does a fair job.

ChocoHolic 9th September 2012 07:42 PM

The basic set up is looking Ok to me.
But the choice of the MosFet is really unpleasant.
It is not just the gate charge, but also the body diodes.
trr =1100ns, Qrr=40uC !!
IMHO a no go for class D.
Don't you observe massive heating, when running at high rails and high signal levels? At 200kHz you might even risk defects.

Ever looked at these?

No snubbers?

DUG 9th September 2012 07:54 PM

At first I was looking at the signal path thinking "what is he doing here".

Then I figured it out.

I like it...

Except for one small change.


I would add a cap in series with R12 to prevent any DC...

But that is just me.

Tekko 9th September 2012 08:16 PM

This amp has now been running for several hours on 2x60V rails and have never even gotten warm, its stone cold!

A video: Feedbackless Class D amp with new Power Stage - YouTube

Why the STE47N50 ? well i happened to have 12 of them laying around and as it turns out, the amp is now working ALOT better, its even sounding better.

The feedback loop depicted in the schematic is not actually implemented yet, the amp is running completely open loop.

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