500W 12v to 220v Inverter

[photoar]

oh !
and the 'step up' transformer can be any usual 220v to 2x12v transformer, right ?
or it must say clearly 'step up' or 'inverter' ??

i'm using a regular "step down"(?) transformer

[audioguru]

Hi Photoar,
You made my corrected circuit that has been on the site for nearly 3 years until it was changed recently.
Look at the changed one in POWER CIRCUITS in our PROJECTS section. It is missing important parts and its frequency determining parts values are wrong.

The transformer is a 220VAC to 2x12VAC power transformer rated for 500VA or 600VA. The 2x12VAC windings can also be 24VAC center-tapped.

[MP]

Thanks MP !!

can you please attach or tell me the difference between the one i did and the one on your site ?
i found it on this site of course.... 

The one now on the site is designed just like any other square wave inverter. The one you built is designed just like an audio amplifier with heat generating resistors to ground. Something you would expect to be designed by a stereo technician or audiophile. It consumes way too much energy from the battery. Others have emailed me to let me know they had to make serious changes to get it to work properly for them. It was after these emails that the one you made was removed from the site.

MP

[audioguru]

The one you built is designed just like an audio amplifier with heat generating resistors to ground.
.... It consumes way too much energy from the battery.

With a 500W load, each 0.1 ohm emitter resistor dissipates 10W half the time. Their total power dissipation is only 40W (8% of the load's power). Then the transistors don't need to be matched to have the same current gain. Remove the resistors if you can buy matched transistors.
With less load then there is less power in the equalizing emitter resistors.

Mosfets are much better than old transistors in a simple square-wave inverter. This circuit is old and is used where Mosfets are not available.

Others have emailed me to let me know ...

They didn't e-mail me and I developed the modification. But they e-mail you?