class d amplifier- problem with feedback loop

[aborigini]

hi,

I am designing this class d amplifier with feedback. I am not sure how much of the feedback should I fedback and summed with the input audio signal. I am using a resistive feedback network.

I used integrator to remove the higher order harmanics. But wondering whether it would be better to use a low pass filter instead of an integrator.

Anyone can give input? thank you.

 

[Harmasha]

Hi friend,

Its wise to have a high order filter and have the feedback section tapping from the filter output. However note that the time shift is not too high that it upsets the stability of the amplifier and making it an oscillator.

Some methods also involve taking the feedback directly from the output so that the frequency and phase can be maintained.

Check out this link also:

h**p://www.ee.ucr.edu/~rlake/EE135/Class_D_amp_notes_AL.pdf

 

[aborigini]

thank you for the input. I already have the paper and use it for the initial design stage.

Actually I am using a second order intgrator, but thinking to upgrade to 3rd or 4th order, but not sure whether it is advisable.

I am taking the output prior to the low pass filter output. So, the feedback it still in switching pulses.

I am very concerned about the harmonics, how to reduce it. I did manage to minimise odd order harmonics, but the second one is really high.

Could anyone suggest the cause for the even harmonics?

Thankyou.