switching class d amp

steven344 · 19th November 2005, 04:03 PM

http://www.angelfire.com/indie/jcnoe.../switching.pdf

Pierre · 19th November 2005, 04:43 PM

It seem quite a classic and not very hi-tech Class-D amp (P/N mosfets, etc), but has anyone had a look at the power supply? It seems to use the 117VAC input to produce +/-51V rails, with no transformer!!!

For apps. where the user can't touch any terminal, such as active speakers, etc, where safety is not a problem (this supply is not galvanically isolated!), it can be useful.

Mmm, I wonder if that design can be modified for 230VAC mains and any output voltage with proper component values... I will have a deeper look at it but it is, at least, interesting.

john65b · 19th November 2005, 04:53 PM

I don't get it. You rectify 117AC and you get +/- 81V (not including diode losses)

How do they get 51V?? Is my math wrong??

Pierre · 19th November 2005, 05:21 PM

The triac cuts the output during a variable time, depending on the output voltage, that is sensed and compared to a reference. This way the caps are charged to the correct voltage. It is similar to a lamp dimmer, but I hadn't seen something like this, operating from a _rectified_ mains and then filtered to get DC.

the center point (GND) is obtained by a voltage divider made by caps. I don't know how stable this will be...

mzzj · 19th November 2005, 05:22 PM

Quote:

Originally posted by Pierre:
It seem quite a classic and not very hi-tech

Not very high-tech is not right word, stone-age low-tech is proper for this!

Triac "regulated" power supply. TL074 used as a comparator. Not isolated from mains. 50khz modulation frequency. No output coils/chokes. Collection of ideas how not to do d-class.

Pierre · 19th November 2005, 05:30 PM

Yes, Class-D has been improved a little bit since them, hasn't it?
But you cannot say that the supply is not, at least, original and worths the pain being studied a bit more...

steven344 · 19th November 2005, 08:10 PM

I have only put these here because they work but know they are old and can be improved.Class d is still not as easy to build for the diy as gainclone chip amps,also there are not many schematics around.Both of these circuits could use a vco or maybe a tl494 as the osc and also use a high/low mosfet driver chip to drive better fets or maybe IGBTs.Sometimes the best thing to do is use something that works and make it better

steven344 · 19th November 2005, 08:12 PM

I would not recommend using the power supply circuit,very dangerous,better off with standard transformer setup.

steven344 · 19th November 2005, 08:17 PM

I would welcome anyone who has schematics for class d amps to post them here maybe we all can pitch in and redesign something or get a better understanding of what can be built in the diy community

steven344 · 19th November 2005, 10:22 PM

Good article

http://power.ece.uiuc.edu/blueboxes/PWM_amp/PWM_amp.htm

19th November 2005, 04:03 PM	#1
steven344 diyAudio Member Join Date: Jun 2005 Location: ohio	switching class d amp http://www.angelfire.com/indie/jcnoe.../switching.pdf

19th November 2005, 04:53 PM	#3
john65b diyAudio Member Join Date: Jan 2005 Location: Chicago	Huh? I don't get it. You rectify 117AC and you get +/- 81V (not including diode losses) How do they get 51V?? Is my math wrong??

19th November 2005, 08:10 PM	#7
steven344 diyAudio Member Join Date: Jun 2005 Location: ohio	class d amp articles I have only put these here because they work but know they are old and can be improved.Class d is still not as easy to build for the diy as gainclone chip amps,also there are not many schematics around.Both of these circuits could use a vco or maybe a tl494 as the osc and also use a high/low mosfet driver chip to drive better fets or maybe IGBTs.Sometimes the best thing to do is use something that works and make it better

19th November 2005, 08:12 PM	#8
steven344 diyAudio Member Join Date: Jun 2005 Location: ohio	class d schematics I would not recommend using the power supply circuit,very dangerous,better off with standard transformer setup.

19th November 2005, 08:17 PM	#9
steven344 diyAudio Member Join Date: Jun 2005 Location: ohio	class d schematics I would welcome anyone who has schematics for class d amps to post them here maybe we all can pitch in and redesign something or get a better understanding of what can be built in the diy community


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19th November 2005, 04:43 PM	#2
Pierre Banned Join Date: Nov 2004 Location: Paris	It seem quite a classic and not very hi-tech Class-D amp (P/N mosfets, etc), but has anyone had a look at the power supply? It seems to use the 117VAC input to produce +/-51V rails, with no transformer!!! For apps. where the user can't touch any terminal, such as active speakers, etc, where safety is not a problem (this supply is not galvanically isolated!), it can be useful. Mmm, I wonder if that design can be modified for 230VAC mains and any output voltage with proper component values... I will have a deeper look at it but it is, at least, interesting.

19th November 2005, 05:21 PM	#4
Pierre Banned Join Date: Nov 2004 Location: Paris	The triac cuts the output during a variable time, depending on the output voltage, that is sensed and compared to a reference. This way the caps are charged to the correct voltage. It is similar to a lamp dimmer, but I hadn't seen something like this, operating from a _rectified_ mains and then filtered to get DC. the center point (GND) is obtained by a voltage divider made by caps. I don't know how stable this will be...

19th November 2005, 05:30 PM	#6
Pierre Banned Join Date: Nov 2004 Location: Paris	Yes, Class-D has been improved a little bit since them, hasn't it? But you cannot say that the supply is not, at least, original and worths the pain being studied a bit more...

19th November 2005, 10:22 PM	#10
steven344 diyAudio Member Join Date: Jun 2005 Location: ohio	class d amp article Good article http://power.ece.uiuc.edu/blueboxes/PWM_amp/PWM_amp.htm

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