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

State of the Art for Tracker/Down Converter?
State of the Art for Tracker/Down Converter?
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 9th November 2018, 10:44 PM   #31
xrk971 is offline xrk971  United States
Got Foam?
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
State of the Art for Tracker/Down Converter?
Some of the latest advances in MOSFET switching technology is in GaN. They are high power and high speed ideal for RF and microwave. Audio doesn’t really need ultrahigh speed, but since you asked about advances. They are interesting and certainly SOA.

https://epc-co.com/epc/Portals/0/epc...ndamentals.pdf
__________________
XRKaudio https://www.etsy.com/shop/XRKAudio
  Reply With Quote
Old 10th November 2018, 01:19 AM   #32
wg_ski is offline wg_ski  United States
diyAudio Member
 
Join Date: Oct 2007
Class D is all about switching speed. You really need a carrier frequency of about 400 kHz for full range operation. Just about any transistors can be made to switch at that frequency, but the faster they turn on and off the lower the switching losses. And the shorter the dead time between one turning off and the other turning on the lower the distortion.

The actual semiconducor physics of even old school silicon MOSFETs aren’t really the limiting factor in their speed. They switch very fast if you can pull the gate charge out fast enough. This is often limited by package inductance and the external circuit. The advantages of things like GaN is you can make a very small high current chip. This enables building an electrically “small” circuit with low capacitance and inductance per ampere of current capacity.
  Reply With Quote
Old 10th November 2018, 02:02 AM   #33
Dave Zan is offline Dave Zan  Australia
diyAudio Member
 
Join Date: Nov 2010
Quote:
Originally Posted by MorbidFractal View Post
In relative terms I do not know dick.
Ok, I was briefly mistaken.

Quote:
Originally Posted by xrk971 View Post
Some of the latest advances...in GaN
Thank you for that link, when I didn't receive much response initially I started to look at GaN myself.
Some of the performance metrics are better than Si but, yes, I am not sure if they provide much benefit for audio.
It does look a reasonable option however, and would be fun, not to mention "latest SOTA transistors" claims.

Quote:
Originally Posted by wg_ski View Post
...You really need a carrier frequency of about 400 kHz...And the shorter the dead time...the lower the distortion.
...an electrically “small” circuit with low capacitance and inductance per ampere of current capacity...
Yes, many trade-offs of efficiency, distortion, complexity and cost.
That's why the ZVS/ZCS circuitry interests me, better efficiency and lower EMI.
The electrically small circuit implies physically small too, so inevitably SMT.
I don't want to push that too far but it should please "Krisfr".

Best wishes
David

Last edited by Dave Zan; 10th November 2018 at 02:14 AM.
  Reply With Quote
Old 10th November 2018, 02:16 AM   #34
wg_ski is offline wg_ski  United States
diyAudio Member
 
Join Date: Oct 2007
ZVS/ZCS switching is applicable to the power supply, but not the amplifier. The timing of the turn-off needs to be in sync with one of the resonant modes of the circuit. In a class D amp or tracking down converter, the position of the zero crossings is going to move around.
  Reply With Quote
Old 10th November 2018, 02:28 AM   #35
Dave Zan is offline Dave Zan  Australia
diyAudio Member
 
Join Date: Nov 2010
Quote:
Originally Posted by wg_ski View Post
...the turn-off needs to be in sync with one of the resonant modes of the circuit...
A SMPS can vary the power to the load, which is all a down converter has to do.
The down converter doesn't have to be PWM at fixed frequency.
Apparently it's typical for an LLC circuit to maintain ZVC/ZVS over a 3 to 1 frequency variation.
The quiescent current draw of the linear amp actually helps to provide a load so the down converter doesn't have to vary too much.
So 900 kHz to 300 kHz perhaps, the ratio can be limited by choice of the inductance ratio for the two Ls in the LLC.
I suspect that a class-D could be done similarly but am less positive.

Best wishes
David

Last edited by Dave Zan; 10th November 2018 at 02:34 AM.
  Reply With Quote
Old 10th November 2018, 02:54 AM   #36
wg_ski is offline wg_ski  United States
diyAudio Member
 
Join Date: Oct 2007
The down converter’s output voltage and will need to change directly one for one with the instantaneous output voltage of the amplifier, and the current change proportionally once the output current gets above the quiescent value. It’s a big swing - it needs to be in order to maintain efficiency (keeping Power lost to a few volts times Iout).

An LLC supply may stay in resonant mode over a 3:1 range of load current by changing the switching frequency, but it’s output voltage remains fairly constant. The tracker will swing over a lot more than 3:1 - and the current and voltage change together. I doubt even the guys that designed the Labgruppens have figured out how to keep soft switching over that much range. If you do you could make a lot of money...
  Reply With Quote
Old 11th November 2018, 01:47 AM   #37
Dave Zan is offline Dave Zan  Australia
diyAudio Member
 
Join Date: Nov 2010
Quote:
Originally Posted by wg_ski View Post
...over a lot more than 3:1
The 3:1 represents a reasonable frequency variation, this is not the same as the achievable load variation.
The trick is to have a wide load variation result in a small frequency variation.
The relationship between the two variations depends on the details of the converter and is not clear to me yet.
But it looks doable.

Quote:
If you do you could make a lot of money...
I just wanted a nice system for my home!
Then I have ideas and it becomes a quest to satisfy my curiosity.

Best wishes
David
  Reply With Quote
Old 11th November 2018, 02:56 AM   #38
wg_ski is offline wg_ski  United States
diyAudio Member
 
Join Date: Oct 2007
3:1 is about the range of load current that an LLC can stay in resonant mode (by adjusting frequency and duty cycle). At low currents it is not and the efficiency drops somewhat. But it’s still less heat than at full load where it operates at full efficiency. I wouldn’t sweat the fact that the converter will be a hard switched application - or at least it will over the majority of its operating range. It is still going to be way more efficient than a class B amplifier.
  Reply With Quote
Old 11th November 2018, 07:11 AM   #39
Dave Zan is offline Dave Zan  Australia
diyAudio Member
 
Join Date: Nov 2010
Quote:
Originally Posted by wg_ski View Post
3:1...load current that an LLC can stay in resonant mode...
Do you have a reference for this?
Or an example, specifications for a typical LLC SMPS maybe?

Best wishes
David
  Reply With Quote

Reply


State of the Art for Tracker/Down Converter?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
My Linear Tracker (a new variation perhaps?) soyuz Analogue Source 208 5th March 2016 06:00 PM
DIY parallel tracker air arm - another one Speedysteve7 Analogue Source 36 30th May 2013 02:10 AM
Issues with Emu tracker and THD measurements Stefanoo Solid State 165 4th May 2012 02:20 AM
E-MU tracker GK Everything Else 7 9th November 2009 02:14 PM


New To Site? Need Help?

All times are GMT. The time now is 03:56 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki