PLaying with ClassD again

TroelsM · 11th February 2008, 08:35 AM

Hi.

Here's a small peak at my latest classD-fumblings.

I concentrated on the output-stage at first. It's build around a IR2110 and two FQB19n20L.

Here's a few pics of the output-waveforms before the filter. First a 115Vpp square and the rising/faling edge. Rise/fall-time is approx. 35nS (10%->90% of voltage-range). Looks promising.

Next on the to-do is the modulator-scheme. Most likely selvf-osc in some form. Any ideas? What's your favorite-scheme of the day?

Please click this link to see more info: http://kofoedmejer.squarespace.com/classd-amplifier/

Regards TroelsM

luka · 11th February 2008, 08:39 AM

Hi

I have tried clocked version, works great. Ucd's are also great...really hard to say what to go for... ucd is more simple if you make it all discrete

Hope you will have bigger cap for upper gate drive, when you will go into hard clipping

Are those pics befere or after LC filter?

TroelsM · 11th February 2008, 08:42 AM

Waveforms are taken before filter. Just edited my prev. post to reflect this.

Regards

luka · 11th February 2008, 08:48 AM

Hi

Bit you to it

Before LC you won't have really any problems, you should connect LC filter too, and see what you get there...
Do you have any rail-rail decoupling caps on board?

TroelsM · 11th February 2008, 08:54 AM

Hi.

Each rail has a 330uF/100V e-cap and a smaller film-cap. There is no caps from rail to rail. Why?

lumanauw · 11th February 2008, 08:55 AM

Is there any good clocked classD schematic with feedback taken after LC filter?

luka · 11th February 2008, 09:03 AM

Hi

@ TroelsM

You will need noise free rails as much as possible, this is why you should have rail-rail cap too, 2x100n or 1x220-330nF, try to find some good ones

@lumanauw

Yes there is as far as you ask me, made by fredos and then redesigned by alexclaire

TroelsM · 11th February 2008, 01:34 PM

@Luka

Output filter was connected at the time, but the plot shows the pre-filter waveform.

The cap on the floating supply is not very big, but I will change it later. Right now its not the biggest problem.

Thanks for the help. Re-visit the tread later to see more.

Regards

TroelsM · 20th February 2008, 06:10 AM

Doh!

Regards TroelsM

luka · 20th February 2008, 06:48 AM

Hi

What are you trying to say?
It is better then my...

11th February 2008, 08:35 AM	#1
TroelsM diyAudio Member Join Date: May 2003 Location: AARHUS. DK	PLaying with ClassD again Hi. Here's a small peak at my latest classD-fumblings. I concentrated on the output-stage at first. It's build around a IR2110 and two FQB19n20L. Here's a few pics of the output-waveforms before the filter. First a 115Vpp square and the rising/faling edge. Rise/fall-time is approx. 35nS (10%->90% of voltage-range). Looks promising. Next on the to-do is the modulator-scheme. Most likely selvf-osc in some form. Any ideas? What's your favorite-scheme of the day? Please click this link to see more info: http://kofoedmejer.squarespace.com/classd-amplifier/ Regards TroelsM __________________ Need more time...

11th February 2008, 08:39 AM	#2
luka diyAudio Member Join Date: Sep 2005 Location: in Slovenia :)	Hi I have tried clocked version, works great. Ucd's are also great...really hard to say what to go for... ucd is more simple if you make it all discrete Hope you will have bigger cap for upper gate drive, when you will go into hard clipping Are those pics befere or after LC filter? __________________ home page @ http://www.classdaudio.co.cc @ 24/7 all year long I FEEL SLOVENIA

11th February 2008, 08:42 AM	#3
TroelsM diyAudio Member Join Date: May 2003 Location: AARHUS. DK	Waveforms are taken before filter. Just edited my prev. post to reflect this. Regards __________________ Need more time...

11th February 2008, 08:48 AM	#4
luka diyAudio Member Join Date: Sep 2005 Location: in Slovenia :)	Hi Bit you to it Before LC you won't have really any problems, you should connect LC filter too, and see what you get there... Do you have any rail-rail decoupling caps on board? __________________ home page @ http://www.classdaudio.co.cc @ 24/7 all year long I FEEL SLOVENIA

11th February 2008, 08:54 AM	#5
TroelsM diyAudio Member Join Date: May 2003 Location: AARHUS. DK	Hi. Each rail has a 330uF/100V e-cap and a smaller film-cap. There is no caps from rail to rail. Why? __________________ Need more time...


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11th February 2008, 08:55 AM	#6
lumanauw diyAudio Moderator Emeritus Join Date: Oct 2002 Location: Bandung	Is there any good clocked classD schematic with feedback taken after LC filter?

11th February 2008, 09:03 AM	#7
luka diyAudio Member Join Date: Sep 2005 Location: in Slovenia :)	Hi @ TroelsM You will need noise free rails as much as possible, this is why you should have rail-rail cap too, 2x100n or 1x220-330nF, try to find some good ones @lumanauw Yes there is as far as you ask me, made by fredos and then redesigned by alexclaire __________________ home page @ http://www.classdaudio.co.cc @ 24/7 all year long I FEEL SLOVENIA

11th February 2008, 01:34 PM	#8
TroelsM diyAudio Member Join Date: May 2003 Location: AARHUS. DK	@Luka Output filter was connected at the time, but the plot shows the pre-filter waveform. The cap on the floating supply is not very big, but I will change it later. Right now its not the biggest problem. Thanks for the help. Re-visit the tread later to see more. Regards __________________ Need more time...

20th February 2008, 06:10 AM	#9
TroelsM diyAudio Member Join Date: May 2003 Location: AARHUS. DK	Doh! Regards TroelsM __________________ Need more time...

20th February 2008, 06:48 AM	#10
luka diyAudio Member Join Date: Sep 2005 Location: in Slovenia :)	Hi What are you trying to say? It is better then my... __________________ home page @ http://www.classdaudio.co.cc @ 24/7 all year long I FEEL SLOVENIA

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