ucd 25 watts to 1200 watts using 2 mosfets - Page 8 - 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 23rd May 2010, 02:51 PM   #71
diyAudio Member
 
nigelwright7557's Avatar
 
Join Date: Apr 2008
Location: Carlisle, England
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!
There is also the fact that MOSFETs require about 3.5 volts to turn them on so you lose 7 volts in total to the output.

You also lose 40% of your power as heat in the heatsink.
__________________
PCBCAD50 software. http://www.murtonpikesystems.co.uk
  Reply With Quote
Old 23rd May 2010, 03:01 PM   #72
Pafi is offline Pafi  Hungary
diyAudio Member
 
Join Date: May 2004
Location: Budapest
Quote:
a branch of the amplifier up to 106VCD and the other was down to 82 ... As I said the creator of the amplifier, there are several causes for what happened to me.
1 .- Very low capacitance reservation. I used 8000uF.
2 .- the threshold voltage MOSFETs. He used the IRFP250
These are false reasons, reflecting no knowledge about ClassD amps. The reason is DC offset on output. Against it a capacitor (22 uF) in series with the lower resistor of the feedback can help. There is a better, but a little more complicated solution too.
  Reply With Quote
Old 23rd May 2010, 03:06 PM   #73
Pafi is offline Pafi  Hungary
diyAudio Member
 
Join Date: May 2004
Location: Budapest
Nigelwright7557!

This is Class D, not Class AB!
  Reply With Quote
Old 23rd May 2010, 03:25 PM   #74
diyAudio Member
 
Workhorse's Avatar
 
Join Date: Dec 2004
Pafi..........class-d is new buddy
  Reply With Quote
Old 25th May 2010, 10:14 AM   #75
RX5 is offline RX5  Philippines
diyAudio Member
 
RX5's Avatar
 
Join Date: Apr 2004
Location: TaC
another mutation of the NXP ucd amp...
__________________
RoCk On!!! I love my diy UcD!!
  Reply With Quote
Old 31st May 2010, 10:14 AM   #76
diyAudio Member
 
Join Date: Sep 2009
Location: Romania,Calarasi
Send a message via Yahoo to ionutzxpo
hello I made myself this amp and do not work!Click the image to open in full size.
  Reply With Quote
Old 31st May 2010, 03:49 PM   #77
opor is offline opor  Thailand
diyAudio Member
 
Join Date: Nov 2005
If power rail is +-65V what is the value of R7?
  Reply With Quote
Old 31st May 2010, 03:51 PM   #78
opor is offline opor  Thailand
diyAudio Member
 
Join Date: Nov 2005
And what about if power is+-70V? How to calculate?
  Reply With Quote
Old 31st May 2010, 05:43 PM   #79
diyAudio Member
 
Join Date: Sep 2009
Location: Romania,Calarasi
Send a message via Yahoo to ionutzxpo
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...
  Reply With Quote
Old 2nd June 2010, 08:06 AM   #80
qsa is offline qsa  Germany
diyAudio Member
 
qsa's Avatar
 
Join Date: May 2007
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
  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 05:42 AM.


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