ucd 25 watts to 1200 watts using 2 mosfets - Page 9 - diyAudio
Go Back   Home > Forums > Amplifiers > Class D

Class D Switching Power Amplifiers and Power D/A conversion

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 2nd June 2010, 10:07 AM   #81
diyAudio Member
 
Join Date: Sep 2009
Location: Romania,Calarasi
Send a message via Yahoo to ionutzxpo
i use IRFP 260 ,i don't use original components and i think that is why my amp dosen't work, i get on pin 8 on LM 24 volts i use +/-29volts to power the amp.....at first power up all the 2N transistor blow up in smoke and after them the IR2110
  Reply With Quote
Old 2nd June 2010, 05:08 PM   #82
AP2 is offline AP2  Italy
Banned
 
Join Date: Dec 2009
Location: Italy
Quote:
Originally Posted by qsa View Post
which mosfets do you use ?

another people say its working very well, Im confused

I dont have build and test

but in my experience class D is not so good sounding in mid and High frequency in premium sound system for finest sound compare to class AB and class H

In low quality sound system class D is ok and working very well

have test last 2 years different commercial Class D amplifier including powersoft K series and there is not big different in sound only in price for brand

Class D is more energy efficient in power consumption but a good designed Class H output stage does Class D kick out of the job
Hi,I agree with you. This is exactly the problem of D-class amplifier Having tried everything on the market as I thought the answer to the resolution on medium and high frequencies and obtain a crystal clear sound like a professional class AB.
Unfortunately the low resolution at high audible frequencies can not be measured and not depend solely on the carrier frequency on the class D does not depend on the type of feedback if this is pre or post filter.

Regards
  Reply With Quote
Old 2nd June 2010, 05:08 PM   #83
diyAudio Member
 
Join Date: Jan 2010
Location: Brazil, São Paulo
I honestly am suspicious of this circuit, it is very easy to build .. was almost buying components to assemble a class AB amplifier of 1300W on 2R (9 pairs in the output) would be very expensive ....

I now see this in class D 1250W 4R .. I wonder if he has a good quality bass, with punch, can someone tell me if it's really good? even being so simple ....
  Reply With Quote
Old 2nd June 2010, 08:44 PM   #84
qsa is offline qsa  Germany
diyAudio Member
 
qsa's Avatar
 
Join Date: May 2007
Quote:
Originally Posted by Rafael S. M. View Post
I honestly am suspicious of this circuit, it is very easy to build .. was almost buying components to assemble a class AB amplifier of 1300W on 2R (9 pairs in the output) would be very expensive ....

I now see this in class D 1250W 4R .. I wonder if he has a good quality bass, with punch, can someone tell me if it's really good? even being so simple ....
Half Bridge class D Amps have physical Problem with power supply pumping and not good solution for good quality bass... trust me each low cost class AB amp kick Half Bridge class D Amps out of the job < 100 Hz

for good quality bass its important to use full bridge class D Design otherwise you are not satisfied with sound
  Reply With Quote
Old 2nd June 2010, 09:01 PM   #85
Pafi is offline Pafi  Hungary
diyAudio Member
 
Join Date: May 2004
Location: Budapest
Quote:
Originally Posted by ionutzxpo View Post
i have made the circuit for +/-29Volts ,on LM's pin 8 i have 24Volts....the zenner diode is OK....sorry for my english i use google translator to translate from romanian to english:P sorry...
You misconnected something for sure. Check your circuit against the schematic, or send a good photo!
  Reply With Quote
Old 2nd June 2010, 09:03 PM   #86
diyAudio Member
 
Join Date: Jan 2010
Location: Brazil, São Paulo
so unfortunately I will build the amplifier class ab ..

just to kill the doubt, if I mount these two, and put in the bridge (the bridge as AB amps), this would be a full bridge?

and more an issue in the region between 100hz and 2KHz, he has a good sound? or worse in this region than in the bass?
  Reply With Quote
Old 2nd June 2010, 09:16 PM   #87
savu is offline savu  Romania
diyAudio Member
 
savu's Avatar
 
Join Date: Feb 2007
Location: Cluj - Napoca
Send a message via MSN to savu Send a message via Yahoo to savu
Quote:
Originally Posted by Pafi View Post
You misconnected something for sure. Check your circuit against the schematic, or send a good photo!
Hello Pafi,

He had 24Vdc everywhere, stabilizer circuit was ok, zenners were ok, he even used 12V from external trafo. nothing ...

That thing has no dead time implementation before the IR.
It lack's some things... It should have had one 4070 in place of q1,q2,q3,q4

Hope he will start again soon....
I started making a SMPS for him.

Best Regards,

Savu Silviu
__________________
1'st rule of chess:
The only way to get smarter is by playing a smarter opponent.
  Reply With Quote
Old 2nd June 2010, 10:43 PM   #88
Pafi is offline Pafi  Hungary
diyAudio Member
 
Join Date: May 2004
Location: Budapest
Quote:
He had 24Vdc everywhere, stabilizer circuit was ok, zenners were ok, he even used 12V from external trafo. nothing ...
Why did you tell this to me? This changes nothing. There must be a (or more) misconnection (changed component, etc...). My suspects are the pnp transistors.
  Reply With Quote
Old 2nd June 2010, 11:59 PM   #89
diyAudio Member
 
Join Date: Apr 2009
Location: In a IRFP4229
Quote:
Originally Posted by Pafi View Post
The theory is fine, but you ignore too many facts. You ignore all of the switching losses (turn on, turn off, and the most important: diode loss), which can be much more then the conduction loss. You ignore the not perfect cooling. You don't seem to be aware the fact that a hot FET has a 2.5 times higher Rdson then the nominal. You don't provide safety margins.

Have you measured the output power (with dummy load and sine wave)? The paper can bear anything, but practice is different!
Of course I do not know many things! No one knows everything!
At first, the circuit is not mine. Am not the author.
II. Obviously there are losses, but which have the greatest impact is the output MOSFET Rdson. This determines the estimated efficiency of the amplifier, which is of interest ...
In the third ...
Each one provides the level of security you want to build this amplifier. Margins of safety ... Of course! It is obvious that for high power is necessary: Put an extra heatsink size or a little help from the forced-ventilation ...

As mentioned by the sound quality at high frequencies. According to the author, this design is high fidelity. It is known that when the output inductor is not well done, the frequency response changes ... For better or for worse ...
In my case, I found no differences in sound compared to conventional AB amplifiers, quasi-complementary designs and input based on OPAM.

Greetings!

PS: Much more obvious are the differences between real life and the calculation on paper. We do not need to remember them. And no, I measured the output of my amp ... But, get an idea, the power source I used for testing was a Peavey CS800 with an estimated power output of 1200W ... Capacitance but I lacked, that sounded, Uffff, is fierce ...
__________________
See You On The Other Side
  Reply With Quote
Old 3rd June 2010, 10:33 AM   #90
Pafi is offline Pafi  Hungary
diyAudio Member
 
Join Date: May 2004
Location: Budapest
Quote:
II. Obviously there are losses, but which have the greatest impact is the output MOSFET Rdson. This determines the estimated efficiency of the amplifier, which is of interest
Sorry, but I have to say this is simply not true. What you have ignored are very strong effects, in some cases they can be much stronger then Rdson. And these cases are especially at high voltage, high power devices.

Quote:
Put an extra heatsink size or a little help from the forced-ventilation .
If you calculate with the nominal current rating (eg. 30 A in case of IRFP250N) of MOSFET, then you can't put extra heatsink, because nominal current is defined with infinite heatsink, with infinite thermal conductivity, without any insulator between them. What could be bigger then infinite? And it is specified without any switching loss.

If you calculate with the specified Rdson, then the situation is even worse! Rdson is specified at 25C, but at high chip-temperature can be 2-2.5 times more. Let's see IRFP250N again: It's "allowed" dissipation is 214 W. You said "PDmos = I * I * Rdson / 2", so I=sqrt(2*214/0.075)=75 A. Do you really think this MOSFET will handle this much current?

To make things worse: switching loss. Current rise time with this high Rg will be about 50 ns. This is not too much, for example at fsw=100 kHz this means only 2*V*I*tr*fsw=1.5 % loss (almost the same amount what you calculated for Rdson loss). But then add reverse recovery diode loss! Qrr at only Id=18A would be 1.3 nC at 25C, and 100A/us, but at elavated temperature and faster current slope (eg. 20A/50ns=400A/us) it will be higher, about 3 nC. This means P=Qrr*2*V*f=54 W, while Rdson dissipates Pcond_loss=0.15*18*18=49W in a bad case. We can add turn off loss of approximately 20 W, (total loss in MOSFET: ~ 140 W) and we've already reached the practical dissipation limit (at only 18 A output current).

If you use higher voltage, higher power MOSFETs, the ratio between your estimated power, and real power will be even worse because of the increasing diode recovery time and the cooling problem.

Only with MOSFETs optimised for ClassD audio can your calculations be more or less correct, but also with these devices you have to calculate with parameters at elevated temperature, and realisable cooling!

11250 W with 2 FETs, in this circuit is a joke.

Quote:
Of course I do not know many things! No one knows everything!
Yes. But one who doesn't know, he shouldn't give advice in the unknown fields, or at least attach an 'as far as I know', or 'but please correct me if I'm wrong'! These issues are the basics of high power ClassD amps, everybody should be aware of them.

Quote:
And no, I measured the output of my amp ... But, get an idea, the power source I used for testing was a Peavey CS800 with an estimated power output of 1200W ... Capacitance but I lacked, that sounded, Uffff, is fierce ...
I don't understand any of these sentences.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Philips 40/25/15 watts amplifier with Universal preamplifier circuit. renjiish Solid State 64 28th July 2014 11:33 AM
Decibel Watts VS Watts ? fivestring Solid State 11 1st April 2009 01:08 PM
AMP1-B: why only 25 watts @8ohms? theAnonymous1 Class D 10 15th August 2005 06:55 PM
Sound quality of amps at 0.3 watts vs @ typical 5 watts rick57 Solid State 2 26th March 2005 06:25 AM
Need 2 watts Vivek Everything Else 4 17th July 2003 08:29 AM


New To Site? Need Help?

All times are GMT. The time now is 03:38 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2