Common commercial inverter without feedback ?

[unavezmasysale]

Hi,
I am working with a very common commercial inverter because it will be part of my project. I tried to find the schematics but I couldn´t. However, I found one that is very similar, but not exactly the same. It is attached.

The problem is that the output is OK without charge, but once I connect a lamp the duty cycle of the output become very very small.

As the schematic show, the feedback is connected to the primary circuit that is the one that I suppose control the output, through R8 and VD4. The problem is that in my circuit, that is not exactly the same to the attached one, there is not feedback between the primary and the secondary.

Is that possible?
What do you think about the problem?

I add that VT10 (down mosfet of the bridge) is the only mosfet that become very hot.

I really need help...

Thanks you very much.

Regards,

 

[chuckey]

If VT10 is getting hot, it sounds like it is not being switched off properly, could be VD10/R28 or VT10 are faulty.
Frank

 

[unavezmasysale]

Hi Chuckey, the inverer is working, the problem were two capacitors.

Thanks!