Hi-Fi Class-D Amplifier

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Hello guys, im a bit new to this forum!

So i am currenty developing a feedbackless Hi Fi class-D amplifier! Here is the schematic: http://ftp.torespont.hu/solarian/classd/kapcs-uj.JPG My problem is that, that the LM319 comparator picks up really lot of noise(oscillating or sy)! Ive disconnected the output of the comparator from the 4070, totally grounded the audio_in pin, and the noise is still there! The Triangle wave is almost perfect, no dc offset, but the square wave's duty cycle at the output of the lm319 is not 50%!

Here is the PCB: http://ftp.torespont.hu/solarian/classd/uj.jpg
 
I think you should apply the voltage divider to bias the non-inverting input of the comparator to half of the total supply and this would get you the 50+50 % duty cycle also.......

try this!
 

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Hi,

So i am currenty developing a feedbackless Hi Fi class-D amplifier

Good luck! Sounds like an ambitious project, it may not be all that high fi but it will be cool and you'll learn alot.

You haven't described this "noise" in any great detail.

What Lars Clausen describes makes alot of sense, coupled along with real world inputs and parasitics you're liable to have some DC offset as well which will contribute to an error in duty cycle, and Workhorse's idea should help with that in order to give the input a good dc operating point.

What I think you are likely to be a victim of is a slowly transitioning signal(s) on the input of a fairly fast comparator causing multiple/spurrious switching because it's having a hard time deciding which way to go while the inputs are close to one another.

You might try adding some positive feedback (hysteresis) around your 319 to help with this, it's a schmitt trigger is is somewhat useful in class d.

Looks like the perfect circuit to start with. Keep posted.

Regards,
Chris
 
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