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

Class D Switching Power Amplifiers and Power D/A conversion

LTspice Ncore simulation
LTspice Ncore simulation
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 3rd October 2018, 06:28 PM   #11
Reactance is offline Reactance  South Africa
diyAudio Member
 
Reactance's Avatar
 
Join Date: Jun 2005
Location: Cape Town
Interesting seems like alot of reverse engineering effort, missing bus rail bead inductors.
__________________
There’s nothing worse than the smell of burned output transistors!!
  Reply With Quote
Old 3rd October 2018, 06:29 PM   #12
irs20957 is offline irs20957  Russian Federation
diyAudio Member
 
Join Date: Dec 2017
Location: NNovgorod
simplified a little for simulate, i have full scheme
  Reply With Quote
Old 3rd October 2018, 07:09 PM   #13
luka is offline luka  Slovenia
diyAudio Member
 
luka's Avatar
 
Join Date: Sep 2005
Location: in Slovenia :)
LTspice Ncore simulation
Quote:
Originally Posted by analogspiceman View Post
I have created a 5-pole, 4-zero (I think - haven't derived the transfer function yet) network that reproduces the magnitude loop-gain curve in the white paper. The phase response curve is not published (at least I haven't seen it)
YouTube
from 19:20 onwards
__________________
home page @ http://www.classdaudio.tk/ @ 24/7 all year long
I FEEL SLOVENIA
  Reply With Quote
Old 4th October 2018, 01:46 AM   #14
analogspiceman is offline analogspiceman  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Yahoo, USA
I looked at Ncore section in the NAD M22 service manual. It seems to use a twin tee active filter for the low frequency pole pair and the output L-C for the 3x higher frequency pole pair. Everything is fully differential so it is more difficult to follow. Also much of the circuitry is just a discrete fast comparator that drives the output MOSFETs.

For the purpose of analysis, understanding and system simulation the output can be replaced with a simple behavioral power comparator with settable delay and the feedback and analog front end may converted to a single ended equivalent. The saturation protection can be behaviorally simplified as well. If correctly done, the result should simulate correctly both in the frequency and time domains.
  Reply With Quote
Old 4th October 2018, 04:00 AM   #15
kASD is offline kASD
diyAudio Member
 
kASD's Avatar
 
Join Date: Dec 2004
Location: 5AAB
Yet another similar approach using twin T networks
Attached Files
File Type: pdf NCORE.pdf (239.6 KB, 134 views)
  Reply With Quote
Old 5th October 2018, 01:55 AM   #16
analogspiceman is offline analogspiceman  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Yahoo, USA
Okay, I have simplified and reduced the NAD M22 Ncore fully differential design to its single-ended equivalent. The output stage (which is just a fast power comparator) has been replaced with a behavioral subcircuit. The front-end opamp (also a behavioral model) is driven single ended but it has complimentary outputs in order to achieve proper phasing in the feedback loop.

The behavioral model of the output includes a stimulus source to enable measurement of loop-gain (which then is measured at the comparator input fb node).

Self-oscillation at the undesired lower frequency is suppressed with a bidirectional behavioral diode (its clamping parameters are adjustable).

Because it is cut down to the bare essentials, the simulation runs very fast. It probably could run even a little faster by removing the linear time delay element required for the ac analysis (it would be replaced by a simple a-device delay).

The feedback network around the opamp is not really a twin-tee. In the original circuit it is a dual differential balanced low pass tee (two tees, but not twins in the usual sense).
Attached Images
File Type: gif Ncore.gif (57.0 KB, 387 views)
Attached Files
File Type: asc UcD Ncore.asc (5.5 KB, 48 views)
  Reply With Quote
Old 5th October 2018, 04:00 AM   #17
luka is offline luka  Slovenia
diyAudio Member
 
luka's Avatar
 
Join Date: Sep 2005
Location: in Slovenia :)
LTspice Ncore simulation
peak gain is a bit too high, should be about 65-66dB, as is where double zero act, there should be about 10dB, apart from that, it looks just like the real thing
__________________
home page @ http://www.classdaudio.tk/ @ 24/7 all year long
I FEEL SLOVENIA
  Reply With Quote
Old 5th October 2018, 04:15 AM   #18
analogspiceman is offline analogspiceman  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Yahoo, USA
I haven't analyzed the influence of R1-R3, C1. It must tweak the closed loop transfer function a bit. I wonder why they are there. Maybe they help to linearize the open loop transfer function.

Last edited by analogspiceman; 5th October 2018 at 04:36 AM.
  Reply With Quote
Old 5th October 2018, 07:13 PM   #19
Reactance is offline Reactance  South Africa
diyAudio Member
 
Reactance's Avatar
 
Join Date: Jun 2005
Location: Cape Town
Quote:
Originally Posted by analogspiceman View Post
I haven't analyzed the influence of R1-R3, C1. It must tweak the closed loop transfer function a bit. I wonder why they are there. Maybe they help to linearize the open loop transfer function.
Have you looked at the patent I think vie seen it described in the UcD patent.
__________________
There’s nothing worse than the smell of burned output transistors!!
  Reply With Quote
Old 5th October 2018, 07:30 PM   #20
analogspiceman is offline analogspiceman  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Yahoo, USA
Quote:
Originally Posted by analogspiceman View Post
I haven't analyzed the influence of R1-R3, C1. It must tweak the closed loop transfer function a bit. I wonder why they are there. Maybe they help to linearize the open loop transfer function.
I made a small mistake in the conversion to a single ended topology. The value for C1 should be 4n7 rather than 1n0. Please correct this in your simulation schematic.
  Reply With Quote

Reply


LTspice Ncore simulationHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
How to do IMD simulation in LTspice!!! nicholas1113 Solid State 40 23rd February 2017 04:51 PM
NTC thermistor LTSpice simulation danny92 Software Tools 4 28th November 2013 04:00 AM
LTspice simulation 8409513 Power Supplies 2 28th May 2012 03:02 PM
About LTSpice Simulation. nicholas1113 Solid State 2 15th November 2009 07:52 AM
LTSpice Simulation template?! ipop07 Software Tools 5 13th May 2009 06:17 PM


New To Site? Need Help?

All times are GMT. The time now is 06:23 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki