There are two L in series: L_total = L_BTL + L_BTL = 2x L_BTL.
There are two C_G in series but in parallel with C_BTL.
so C_total = C_BTL + C_G / 2
As you make L1 larger, it starts to 'choke' the output amplitude. It's hard to be sure what tradeoff point to choose.
Statements like this are pretty usless. Specify your requirements and find the necessary filter order.really I want as high attenuation as possible at 300KHz
i have been looking at stuff like this in LTspice but I am trying to see the best to simulate it, I will have a look at it in that software too to see what happens. Is there any way to get a higher order? Or any comments on the inductor design in terms of Isat?
That's an option to save a few components. The differential topology is used to suppress radiated interferences. If you have no speaker cables, you could also use a pure single ended filter. Or take the opposite way, make the whole filter fully differential.Adding a new L and a new C. After the first "symmetric" stage you may now use an unsymmetric stage, that means "really one" L and "one" C.
you can´t use a common mode choke here, because the useful audio currents will compensate each other.
Thus it can´t filter the PWM frequency
1) Look at binary (AD) and tertiary level (BD) Class D and choose BD for better filtering.
You might also consider adding a pair of 300 Khz notch filters (traps) in addition to the usual LPF.
300KHz signal on one leg and the audio on the other
I believe one leg is switched while the other is grounded. No need to apply audio.
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Then reverse the situation when you have a polarity change.
Ground the first leg. Switch the second.
.The low frequency current is the only relevant contribution to core magnetization, or the filter design is flawed
So if the other leg is grounded and switching the other leg, then you do have to take the audio in consideration then?
From what I understand, DC pulses are the only thing that is applied to the output stage
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