A and T labs K6 SMPS for Class D amp use - Page 11 - diyAudio
 A and T labs K6 SMPS for Class D amp use
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 Class D Switching Power Amplifiers and Power D/A conversion

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 28th September 2005, 02:42 PM #101 Banned   Join Date: Nov 2004 Location: Paris In fact, if I am not wrong, dissipation in the resistor depends more on the cap value. Typical snubbers range from 2.2 ohms to 100 ohms. The lower ones can be found in ATX psu's, and are 5W maximum. (although they are half bridge and that must suppose a great difference as the voltage is halved). The formula for max. power dissipation in the resistor is, according to my references, Pr=f x C x V^2 min. power is Pr=4 x C^2 x V^2 x f^2 x R The same references say that the typical power is about half of maximum typically (I suppose it depends on the magnitude of the absorbed ringing).
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Join Date: Jun 2004
Location: Japan
Quote:
 Originally posted by Pierre In fact, if I am not wrong, dissipation in the resistor depends more on the cap value. Typical snubbers range from 2.2 ohms to 100 ohms. The lower ones can be found in ATX psu's, and are 5W maximum. (although they are half bridge and that must suppose a great difference as the voltage is halved). The formula for max. power dissipation in the resistor is, according to my references, Pr=f x C x V^2 min. power is Pr=4 x C^2 x V^2 x f^2 x R The same references say that the typical power is about half of maximum typically (I suppose it depends on the magnitude of the absorbed ringing).
When this SMPS switches, it switches more than 600V as it is a bridge type. Depending on how fast it switches, dissipation will be more or less. Can do some measurements on the waveforms sometime. The dV/dt slope should determine what current flows through the cap and the R and thus the voltage drop over the R can be calculated and thus the amount of power dissipated during each switching event can be calculated and that can be multiplied by the number of switching events. A rough calculation I did predicts something like 5W power dissipation when the 600V switching takes 300ns and when the switching frequency is 150kHz.

Best regards

Gertjan

 20th October 2005, 06:48 PM #104 diyAudio Member   Join Date: Sep 2003 Location: - Fred, You manufacture impressive products..... Can you tell me more about your design? Fixed frequency, full bridge? Pre or post feedback? BTW, do people really need more power as 2kW in 4 ohm?? Regards, Jan-Peter
 20th October 2005, 09:27 PM #105 diyAudio Member   Join Date: Mar 2005 Location: Quebec Hi Jan Peter I use fixed frequence forced oscilation at 250Khz for my first series and 500Khz for the HVI serie. First serie are in half bridge with the trick I described in last post. Second serie is full floating full bridge with reverse side tighted to ground, so you can bridge amplifier if you need more power (????). Power stage is all isolated from drive circuit by optocoupler and power supply provide regulated floating 190V. For now, my 8000HVI is the better seller. 4000W in 4 ohms is more than most speaker can handle, but a stack with 4x 16 ohms speaker per side is impressive. If you dont run amplifier in limiter all the time, most 18'' of 600W handle it. When run at full power, ie limiter go on at each bass kick, most speaker ''fuse'' in less than 2 minute, no burn voice coil...At this time, only Eminence ''kilomax'' serie and Transparence NAC218 (www.tr.ca) handle that power for all night long. More technic now...Power supply is half bridge with IXIS 500V 21 Amp mosfet with direct drive by 6N137 and Micrel Drivers. Control is SG3525 in voltage mode with regulation by secondary. Current limit is done with small current transformer, who limit the output voltage above 50 Amp at the secondary to limit power, but with a really slow respond time, about 30 second. So maximum power is reach within 30 second, after that, power go down to 670W per channel in 4 ohms. With music, each time that signal pass trought 0V, circuit is reseted. So no effect on music, but limit power on the bench for savage tech... after 30 second. Another circuit sense current and voltage waveform at the main AC supply, and when current wave is more dense that voltage wave, amplifier limiter begun active. This will prevent fuse and breaker blowing. Last trick, another circuit sense current in the speaker and when current ration is over range, meaning that speaker voice coil is out of is tolerance, limiter is actived too. Some kind of speaker saver, for short time. For all who ask for schematics, I'm sorry but I have work 6 years on this amplifier, so I can give you lot of cue, but no schematic....You know that I'm in advance over Crown, crest and peavey, I whant to keep it! Sorry for guy who work here! Have a nice day! Fred
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Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
Quote:
 Originally posted by Jan-Peter BTW, do people really need more power as 2kW in 4 ohm??
More is better, don't you know it?

Pros tend to have many amps with reasonable power instead of one gaint.

BTW: Just read the data. It makes me wonder because some things sound not right.

97.5% effeciency and 7800 watts or?

9600 Watts and 110/220 volts AC? Is that possible in the US, sure not in Europe??
__________________
/Per-Anders (my first name) or P-A as my friends call me
PA03 LM4780 amplifier group buy, SIGN UP HERE 70 boards delivered but you can sign the queue list.

 20th October 2005, 10:33 PM #107 diyAudio Member   Join Date: Mar 2005 Location: Quebec Hello peranders 4800va per channel is the maximum instantanous consumption recorded in amplifier with music at hard clipping....Sorry for this, I will try to update web site to make this more simple....Sound like some people call peak power....All high power test have been done with 240V 30 amp main supply...The fuse saver in amplifier limit output power to avaible power source...So dont expect more than 1800W RMS total on 120V 15A outlet, but peak at 4000W per side is theire! Bye Fredos
 20th October 2005, 11:06 PM #108 Account Disabled   Join Date: Feb 2004 I thought it would be peak. Could you also clarify what you mean on your site by "inductive and reactive power includes", that'd be VAR or something no? Thanks, Chris
diyAudio Member

Join Date: Dec 2004
Re: Hi Jan Peter

Quote:
 Originally posted by fredos I'm sorry but I have work 6 years on this amplifier, so I can give you lot of cue, but no schematic....You know that I'm in advance over Crown, crest and peavey, I whant to keep it! Sorry for guy who work here! Have a nice day! Fred

Hi Fredos,

You had worked hard for 6 years and now enjoying the Fruit of Class-D at Kilowatt power levels and that is your Right too....

But Have you visited http://pro-audio.powersoft.it/ these guys had 12KW [12000Watts]CLASS-D amps in 1 U rack space featuring Centifugal Blowers for cooling instead of axial fans...

one more question,
Did your Class-D amps feature 2 LEVEL PWM or 3 LEVEL PWM when they are bridged?

Keep it up ,

regards,
K a n w a r

 21st October 2005, 08:31 AM #110 diyAudio Member   Join Date: Mar 2005 Location: Quebec Hello Workhorse! I know powersoft...I already made some test on their 7Kw amplifier, the first serie I think...Not impressive...First, output was not thighted to ground and have a potentialy dangerous DC voltage, referenced to AC and input ground, and second, explain my why, on the bench, they only put 222W RMS in 4 ohms...Something wrong??? I dont know....On music, they seem to peak near 2Kw 4 ohms per side, but bass is very lean, very noticiable with hip hop music whit ''fat'' bass (maybe rolling bass in english???). On other music, like rock with good attack bass, it was a bit impressive, but compare to a Crown VZ5002 (my reference to overkill!), nothing to compare...I dont know about new serie, I cannot find nobody who buy it in Quebec....And yes, I run it on 240V....But one very good thing, the amplifier look very nice inside, I like the way that they have built it.... Nice for their 12KW, but by experience, for now 4KW per side is a bit dangerous for majority of speaker, so except with serie-parrallel speaker, maybe no use....And pro dont made serie-parrallel, at least 4X 16 ohms speakers, what most use on my amplifier. But just for fun, not for production, I will plan to make maybe a 10KW mono amplifier with SGS thompson fet, the STE53NA50, With the same circuit I use in my 8KW, but at 350V...Could be nice to develop it just for fun, in 1U... To give you an answer, I only drive my power stage with 1 level PWM, out of phase for each side of my bridge topologie. That means that 1 side of H bridge provide power to speaker and other side shift the DC bus voltage above and under ground reference, just like a conventional full bridge amplifier, but on side to ground and the other to speaker. That's why I use floating power supply. It's the same power as a half bridge at +/- 190V. By the way, you maybe find that my english is not perfect, but sorry, I speak french! Thanks! Fred

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