UPWM - diyAudio
Go Back   Home > Forums > Amplifiers > Class D
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Thread Tools Search this Thread
Old 1st July 2011, 11:45 AM   #1
diyAudio Member
Join Date: Apr 2010
Default UPWM

I have read that NPWM(natural analog PWM) is fundamentally linear whereas UPWM(digital PWM) distorts the input signal. Intuitively, are not the pulse widths linear to the input amplitude in both the above cases?

Could someone please give me intuition on this or can point me to some resource which gives intuition on this. I have referred Karsten Nielson's thesis too, but could get only a mathematical proof.
  Reply With Quote
Old 2nd July 2011, 11:13 AM   #2
Pafi is offline Pafi  Hungary
diyAudio Member
Join Date: May 2004
Location: Budapest
Intuitively, are not the pulse widths linear to the input amplitude in both the above cases?
Not amplitude, but sampled values of the signal! And the difference is in the sampling points. As long as the input signal is DC, or very low frequency, the two methods are equivalent, but at high input freq the naturally sampled and uniformly sampled PWM takes different sample values. This can be seen if you draw them.

Basically both methods generates some problematic spectral components, but while UPWM generates harmonic distortion, NPWM generates non-harmonic components. I can't tell why.

PS: NPWM is not neccessarily analog and UPWM is not neccessarily digital. Both can be realised in both way, but the basic operation in theory is always analog! True digital "PWM" is a totally different thing (sigma-delta converters).
  Reply With Quote
Old 2nd July 2011, 12:18 PM   #3
diyAudio Member
Join Date: Apr 2010
pafi, thanks for replying. I have referred many papers. Everywhere, people tell UPWM is nonlinear and come up with techniques to approach NPWM. But they never explain intuitively why UPWM is non-linear and why NPWM is linear.

Another doubt I have is that, even though the comparator is such a non-linear block, the NPWM output spectrum is totally linear for the signal in the baseband. Can anyone please discuss their angle of viewing this property of the PWM.

Last edited by terminator12; 2nd July 2011 at 12:23 PM.
  Reply With Quote


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

New To Site? Need Help?

All times are GMT. The time now is 01:30 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2