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PWM Sinewave generation Basics

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thannara123

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I am learing basics of PWM sinewave generation .
How do the negative half cycle of the sinewave genarats ? (in general condition ,) or the How the Negative portion makes ?>
is it shifting the DC offset ?
how can i accomplish it ?
 
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Hi,

it depends on your hardware.
* a full bridge: swap the left side with the right side.
* single PWM with (0V / 3.3V levels) can´t generate negative values. Thus you need to add an offset on the digital side and subtract it on the analog side.
Subtracting an offset on the analog side could be done with a high pass filter, for example.
* single PWM with (-3.3V / +3.3V levels using an analog switch) just needs to add an offset on the digital side.
* ...

--> show us your hardware details and we can give more focussed answers.

Klaus
 
The Brdiges (H or full bridge) generates the neagtive and half cycle .
microcontroller produce the positive pulses only
isnt it ?
otherwise we need to shift the signals to get sinewave .
 

If you pass the PWM signal through a hi-pass coupling capacitor, it will remove the DC offset and give a symmetrical waveform with a zero average value (one of KlausST's suggestions).
 

    thannara123

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Or consider applying 1/2 supply_V to the other end of your load. The load gets AC bipolar waveform.

SPWM posi supp LC fil 2-cap push-pull load gets AC sines.png
 

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