Sine wave power inverter

[mincing]

Hope you are fine.

Thios time I have come up with a weird question.What is the meaning of Sine PWM being 25KHz.

Say we consder 32 samples it gives ,20ms/32=625uS.
===>frequency of each sample is only 1.6KHz .

Then ecverybody talks of 25 KHz .Could you please explain that a little.

Thanks,

[sougata]

Hi,

You are using a lookup table to modulate a carrier frequency (The PWM). In analogue world this is AM. But the pronciple here is of a class D amplifier. That is your switches are either off/on and not working in the linear region. You can use any frequency thats twice (nyquist) the output frequency mulitplied by the resolution (steps) of the lookup table. Your output transformer and parallel resonant capacitor forms a filter to integrate the modulated PWM into a sinewave. Normally the PWM is kept higher than 20KHz to reduce audible noise in the transformer. While keeping it lower has a certain advantage of lower switching loss.