are isolated supplies needed for high-power class-D? - Page 3 - 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 25th February 2009, 08:08 PM   #21
diyAudio Member
 
darkfenriz's Avatar
 
Join Date: Jun 2004
Location: Warsaw
And how about power factor?
  Reply With Quote
Old 25th February 2009, 09:14 PM   #22
Pafi is offline Pafi  Hungary
diyAudio Member
 
Join Date: May 2004
Location: Budapest
Who cares? (However rectification, PFC, and idle potential are 3 different things, so I don't see the relevance.)
  Reply With Quote
Old 25th February 2009, 09:46 PM   #23
iand is offline iand  United Kingdom
diyAudio Member
 
Join Date: Feb 2007
Location: London
Quote:
Originally posted by darkfenriz
And what are the technical benefits of non-isolating a high power class D amp?

I assume that the amp's outputs are close to earth at idle, hope this is undisputable.

In the end you need around +-100 to +-150V for the full bridge audio PWM stage, capable of several dozens of amperes at least. As far as I understand to achieve that you may use either:

1. boost PFC, full bridge transformer coupled H-bridge PSU, audio amp (isolated)
2. active front end (AFE) PFC for symmetrical rails, symmetic bucks, audio amp (complicated)
3. AFE PFC and duty cycle limited audio amp (you'll need 1000V switching transistors for audio)

So why bother? My feeling is that this is an idea inspired by the synchronous motor driver circuits, which use nonisolated approach for obvious reasons, one can quarrel taht a speaker actually is a motor, but...
For really high power outputs the only sensible approach is to use fast-switching 600V MOSFETS (CoolMOS) with series Schottky diodes and antiparallel hyperfast diodes -- preferably in one package like this:

http://ixdev.ixys.com/DataSheet/IXKF40N60SCD1.pdf

These can run straight off a centre-tapped half-bridge with up to 500V across it (+/-250V relative to centre tap), and all this then needs is a single-stage PFC boost stage -- this can use CoolMOS and SiC diodes to get very high efficiency (much better than a 2-stage PFC/PWM).

Put 4 of these IXYS devices in parallel for high and low switches (8 devices total) and you have a half-bridge amp which can put out 100A and 225V peak, and can be bridged if you need truly ludicrous single-channel power -- hang on, this sounds very like the Powersoft K20...

Combine both these and you should be able to exceed 90% wall-to-speaker efficiency, which is what you want to do for really high-power amps -- 95% would be even better...

I wouldn't be at all surprised if this is also what Eva's working on :-)

Ian

P.S. Outputs don't need to be close to earth at idle or any other time, since you won't be able to touch them it doesn't matter...
  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
High Current Power Supplies matt_uk Solid State 13 11th October 2004 08:49 AM
About high voltage regulated power supplies wd40 Tubes / Valves 4 25th March 2004 03:16 AM
High current DC power Supplies fr0st Parts 7 27th April 2003 03:28 AM
JLH Class A power supplies David H Solid State 1 17th August 2001 04:18 PM


New To Site? Need Help?

All times are GMT. The time now is 01:25 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