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Converting sqare wave into sine wave

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Advanced Member level 3
Apr 24, 2010
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Dhaka, Bangladesh, Bangladesh
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What is the best way to convert square wave into sine wave in an economic way? Project must have to be micro-controller based(PIC)

1. 220VAC/50HZ (square) >> HVDC >> 220V AC (sine)?
2. Using LC Filter?
3. Using sine oscillator?

Note: power ratings will be 1.0-10.0 KW/ 220V AC / 50Hz. No-load loss should be < 5W.


so where is this square wave coming from in the first place ?!? 10Kw 220V ... nice !!

Basically I need to modify some old inverters of square wave into sine wave. Power rating will be around 1-5KW. But I noted up to 10KW because some inverters are too old to understand.

To illustrate the concept (difficult though it may be to put into practice)...

How a second order filter can turn square waves from an inverter into sine waves:

I cannot be certain whether this method will or won't harm components inside the inverter.

The coil and capacitor must be chosen to suit the load and frequency.

Components carry several amps. A lone small capacitor will be inadequate for this. A bank of several capacitors is needed.

The best thing to do is to used micro-controller to generate spwm if you want to get your real sinewave signal without any problem

yes i think i saw puresine wave inverter using pic16F72 in this forum and its working fine just search you will see it..

Ok, But I don't need the full inverter. I need to convert the power wave shape. Anyway, it may help in my work.

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Ok, But I don't need the full inverter. I need to convert the power wave shape. Anyway, it may help in my work.

shaping a square wave to sine wave isn't that easy and it's going to be less efficient and it can generate a lot of loses so the only thing is if you really need pure sine wave then used SPWM + LPF and you will get your pure sine wave signal

1. 220VAC/50HZ (square) >> HVDC >> 220V AC (sine)?
I think very difficult, 220v RMS sine= 310v dc or above for losses etc.
3. Using sine oscillator?
May be complex circuit.
2. Using LC Filter?
Some thing reasonable.
Use three pole RC/ LOW PASS FILTER with 1K resistance and 1uF cap in series of MCU and driver circuit and check.

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