Amplitude to PWM

188

01:36:33

So im trying to create a PWM from a music signal depending on its amplitude. What i thought of was to controll the current through current mirrors which will cause the cap to charge/discharge faster/slower and so change the dutycycle of the orange mark.
But whenever i add a bjt or sth else in series with the 1k resistors it comes up with the cfs.
Is there any chance this basic idea could ever work?
If it works it would need to be rather high frequency to compansate for the changing current right?
Ignore the stuff at the top. That was just me trying to split the input so i could controll the current mirrors individually.

published 8 years ago

Valveman11

8 years ago

That's an interesting thought, but I think you're over-thinking this! The way it's done is to use a high-frequency triangle or sawtooth generator (triangle works best), running at 4 Mhz, the higher the better, and feed that into one side of a comparator. Feed the audio signal into the other side, and the comparator will output your PWM. Google Class-D amplifiers. Hope this helps!

ViolationMad

8 years ago

@Valveman11 Yes it does help so thanks alot for your comment. Also really appreciate that you have created a nice example right away.

rich11292000

8 years ago

Slow down sim speed

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