Sorry, maybe I explained badly.
I would drive the transformer ( ATX ) say 100 khz , and get a high voltage that will be rectified ' around 250/300 vdc . Then by means of a "H bridge" drive by a another TL494 , in this case made to oscillate at 50/60 hz , I obtained a sine modified waveform.
I was inspired by an inverter repaired recently.
kyu9971

Once you get the hang of it, getting a high voltage by using a switcher transformer backwards is pretty easy.

Getting a mains frequency "modified sine" can be a little more tricky.

 

I would like, if possible,
But now i am working on a circuit where there are two components that need of 220 vac for some seconds and max 11 watt.
so the idea of to realize an little inverter 12 vdc - 220 vac And so I thought to the transformer of atx power supply.
kyu9971

Realistically for thats small of load and short working duration you would be time and money ahead to go out and buy a small cheap automotive mini inverter and be done with it.
You will never build anything cheaper or more functional than that from second hand parts guaranteed. Around here a tiny 50 -100 watt inverter for vehicles costs about $15- $20 at the worst.

 

Dear tmtech,
If we look from money side, i give you reason, but i look this only for my knowledge.
in this moment the circuit working with a small inverter 300w and when i need of this circuit, i must turn on it. Since i have a little line 12vdc in my house, i wanted to use it.

 

Sorry, maybe I explained badly.
I would drive the transformer ( ATX ) say 100 khz , and get a high voltage that will be rectified ' around 250/300 vdc . Then by means of a "H bridge" drive by a another TL494 , in this case made to oscillate at 50/60 hz , I obtained a sine modified waveform.
I was inspired by an inverter repaired recently.
kyu9971

Oh. That sounds like it would work.

 

Today I did some testing, it has not 'gone well

 

how about a little simpler, if you only want to get high voltage dc frfom an atx transformer with 12 volts dc in, how about using the 12 volt winding and the -5 volt winding in an oscilator, te -5 volt winding as feedback for a mosfet or 2 powering the 12 volt winding? then take the high voltage higher frequency ac off the input side of the transformer, rectify and filter?

 

how about a little simpler, if you only want to get high voltage dc frfom an atx transformer with 12 volts dc in, how about using the 12 volt winding and the -5 volt winding in an oscilator, te -5 volt winding as feedback for a mosfet or 2 powering the 12 volt winding? then take the high voltage higher frequency ac off the input side of the transformer, rectify and filter?

If the TS can find one of the old open frame flyback switchers, its much easier.

Used to be in almost plague proportions - switchers with discrete components on the primary side. Basically just a single transistor blocking oscillator, a second (small) transistor for regulation simply clamped down the power transistor's base.

On the primary side is a feedback winding that is also rectified for a supply to the regulation opto-coupler. The feedback winding works just the same if you swap the other windings over to step up instead of down.

Sometimes these blocking oscillator switchers turn up in TV set top boxes, although IC designs are becoming more common. Sometimes you can get away with using the winding for the control chip supply as the feedback winding.

 

this is the trasformer that i am using.

 

And this is the circuit With which I tested It.
in output there is voltage, but i hear an strange noise from transformer and the mosfet heat to much.

 

And this is the circuit With which I tested It.
in output there is voltage, but i hear an strange noise from transformer and the mosfet heat to much.

The complementary-symetry pairs driving the ends of the winding are an unnecessary extravagance - a straight up pair of single ended push-pull drivers are sufficient and take less drive power from the chip.

 

I also tried in this way, but the problem and 'the same. mosfets heat up so much and the transformer makes a strange noise, maybe i connect wrong the trsnformer?
i connected the wire cyan to central tap and the yellow wire (12v) to the drain of the mosftes ( irf3205).

 

how about a little simpler, if you only want to get high voltage dc frfom an atx transformer with 12 volts dc in, how about using the 12 volt winding and the -5 volt winding in an oscilator, te -5 volt winding as feedback for a mosfet or 2 powering the 12 volt winding? then take the high voltage higher frequency ac off the input side of the transformer, rectify and filter?

Can explain better, i don't understand please?

On web i found the internal schematic of atx transformer.
i found also an circuit (where is used an atx transformer), where is not used the central tap, but i not understand the connecting of the secondary wiring with the primary.