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Old 1st May 2006, 01:45 PM   #21
fredos is offline fredos  Canada
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I agrre with Tekko! You can just begin with a simple full bridge design with mosfet drivers for power stage..That's work great if you use TC4420 and TC4429 drivers with only 1 drive signal from lM319....You get a schematic right now! That's the simple class d you can built! At 18V you can get 40W into 4 ohms....

Fredos

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Old 1st May 2006, 02:07 PM   #22
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To get back on topic.

Fredos, Do you design and build these amps yourself ?

If so im impressed. They look very VERY complicated.
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Old 2nd May 2006, 01:00 AM   #23
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Tekko, he's into pro audio, and copies the design from the Chinese, as they have identical looking products


Fredos, pretty cool of you to be giving out those kinds of hints on your newest Chinese rip off. I think the idea of a seperate charge pump is well served. Drivers have been using it for awhile, at least I thought so? I wonder why it isn't implemented more commonly or as default with the standard higher power driver IC's.

I like how you take care of clipping as well, very nice.

Good luck with em. Sorry for the chinese rip off joke.. I'm just beyond help.
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Old 2nd May 2006, 03:16 AM   #24
fredos is offline fredos  Canada
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Thanks classd4sure!

Anyways, I'm working now on news approach with combinated power amp and switching power supply, in phase modulation schem, all IGBT power converter. I have fews bug to fix, but so fare 2kW of power continuously without heat sink on booth switching device and output device...All surface mount! Sound is bit harsh for now, but I work hardly on this!

More info now...The circuit is a reference switching power supply without rectifier diode. 4 AC switch with IGBT switch the reference signal (2 in 45 degree phase and 2 in 270 phase) to a low pass filter and PWM signal control the phase between 0-90 degree and 180-360 degree for other leg. Work weel for now, stable, VERY efficient, but sound is bit harsh, I have to found why...Each part work at 125kHz, but PWM at output filter is 250Khz, because reference switch in the midle of the sequence of the AC switch. Effective frequency is 500kHz because we run power signal in differential mode....Some pick of the prototype soon! Very simple and efficient!

If someone have evre built a power converter like this and have experience, let me know!

Sleep time...!

Fredos

www.d-amp.com
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Old 2nd May 2006, 03:17 AM   #25
fredos is offline fredos  Canada
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Sorry Tekko...

Yes I design and built amplifier for fun, but the more funny thing is that now I can live with this!

Thanks for comment!

Fredos

www.d-amp.com
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Old 2nd May 2006, 05:17 AM   #26
Eva is offline Eva  Spain
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Do you really believe what you write?

Your pictures clearly show mains rectification diodes, rectified mains storage capacitors, two IGBTs in half-bridge configuration, DC blocking capacitors for the transformer, output rectifier diodes without any filter (the supply is either badly or not regulated) and output storage capacitors.

Why telling fairy tales about rectifierless supplies, a pair of SMD IGBTs without heatsink producing 2KW continuous in half bridge at 125Khz and the like? Each IGBT would be dissipating over 100W in these circumstances (and I know because I'm tired of using them).

Obviously you are taking advantage of the fact that most people reading your thread has never designed and built switching mode power supplies, but I have been doing that for quite a long time now, so you can't just deceive me. I'm sorry (not to mention that now I'm applying all that switching experience to class D).

Finally, if you want to reduce the "harsh sound" problems, you'll have to take an oscilloscope and start finding and fixing switching glitches on every circuit node. You'll probably have plenty of them judging by what you told, and they disturb op-amps and comparators quite badly

p.s. You have not explained us yet how do you expect to reduce or prevent MOSFET body diode conduction by paralleling an external diode whose voltage drop is way higher than the voltage drop from the own body diode. That's only possible when you don't bother reading the datasheets!! The fact speaks for itself.

Why did you seem so puzzled when I mentioned diode charge storage phenomena? That's elemental PN junction semiconductor theory!! Stored charge is a key parameter that determines reverse recovery time and reverse peak current.

Also, that sentence about some comparator hysteresis increasing as instantaneous input signal level increases is even funnier, because it has to be exactly the opposite in order to obtain a relatively stable operating frequency.

Take classd4sure's advice and tell us what are you trying to copy
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Old 2nd May 2006, 06:16 AM   #27
Pafi is offline Pafi  Hungary
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Eva!

That's a different design. The rectifiers he mentioned are not on mains, but after the transformator. But whatever it is, it is unbelieveable.

fredos writes "continuous", but he states on his homepage that "In the case that measurement are done with the non significant method of continuous sine wave input signals (applied for more than 30 seconds), the system is self-protected from that unusefull signals, and lower output values will be found."
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Old 2nd May 2006, 06:26 AM   #28
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Some confusing issues here and we all struggle with the typical language barrier at times.

Firstly we have the ES1D? diode mentioned to be in "anti parallel".

I've heard of anti series in this application, but from the context of everything else it seems this diode would be in parallel would it not?

Secondly EVA speaks to recombination time without any added reverse polarity, natural recombination, this can be sped up with added reverse polarity, but then.... you have high EMI, it would seem.

Fredos mentions using it for it's faster application.. and then the body diode takes over. So can you further explain the usefullness of the // diode if the body diode still conducts for the majority of the time? Am rather confused here, it's a complex topic and can't be discussed very well in bits and pieces like this.

Lastly, Fredos also rates his amps in apparent power, which is only relevant from the point of view of the SMPS capability, and not what it produces across the load, it would seem.
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Old 2nd May 2006, 11:13 AM   #29
Eva is offline Eva  Spain
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Also, if anybody tries to count SMPS transformer turns ratio, the result will be something like 35:7+7. That in turn will produce +-32V rails in a half bridge configuration, and +-64V if I'm wrong and there are two more IGBTs not shown in the picture to form a full bridge. Anyway, the power output attainable with these rails is clearly lower that the ratings claimed, as in practice +-64V unregulated at no load won't produce much more than 400W on 4 ohms!!

If the mains was not being rectified directly, why there are three or more clear-blue coloured big storage capacitors on the left side of the picture with a heatsink near them? It's too obvious that a mains diode bridge is mounted on that heatsink. Also, the classic NTC inrush supressor routinely employed in that arrangement is clearly shown in front of one of the yellow iron powder CM filters!!
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Old 2nd May 2006, 12:10 PM   #30
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Eva, you should start a smps manufacturing company, if you arent doing that already.
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