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Hi Freerider,
Welcome to our forum. ;D
The Inverter project does not work. It is too simple to be an inverter.
Its capacitors are backwards and blow up.
Its transistors have avalanche breakdown that wastes the small amount of power they produce.
The transistors have a very low base current so their output current is much too low for an inverter.

You can use a 220V to 12V-0-12V transformer and get about 25W out.

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Hi Freerider,
Welcome to our forum. ;D
The Inverter project does not work. It is too simple to be an inverter.

Thanks , it is a pity that the inverter does not work(why the administrator doest not delet that project ?)...

This one is much better:

Thanks , maybe i try to built that later , for now , i'am afraid it is too difficult for me , i'am new in electronic... (sorry for bad english)
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I just wish to say that the inverter he is talking about was designed when i was in school by one of my seniors and i saw it at work.But there was a BUZZ sound coming from the circuit.Can anyone know why this happenned?

The buzz comes from the transformer but I wonder if some sound is made by the backwards capacitors.
The capacitors have a very high current pulse that causes them to heat (just before they explode) as a transistor conducts on one side and they quickly discharge into the "dead short" of the other transistor having avalanche breakdown like a zener diode.

The circuit is probably very old and originally used germanium transistors that don't have low voltage avalanche breakdown. It used PNP transistors which explains the backwards capacitors in this NPN circuit.

There is a transistor multivibrator project that explains avalanche breakdown of its silicon transistors. Its capacitors are connected with the correct polarity and it uses a 5V supply to avoid the breakdown:
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  • 1 month later...

Bose: The buzz sound that you heard was caused from not using a large enough transformer.
Freerider: There are much better inverter designs on the web, which will give you much better satisfaction. I would rate this project as a learning project for basic inverter design. Years ago, Delco introduced a very similar design to this one in the US which was mounted on the inner fender well of your car and gave you 120VAC to run appliances from your car. These were also very primitive and barely useful. However, they did sell a lot of them.


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