I know I can buy inverters on the cheap, but I want to fix this. Actually, no, I want to know what's wrong with it, I couldn't care less about an old LCD.
So, to sum things up, I power the LCD, 3-4 seconds pass, then the logic IC sends the ON/OFF command to the PWM controller to turn the backlight on, and that's when things go kaboom, it draws more than 3.5A and my power supply shuts down. Now that I think of it, the problem must be somewhere in the MOSFETS-transformers area, because that is the only thing not engaged in the first 3-4 seconds. And if only one of the P and N MOSFETs were to be shorted, the failure would occur only when you try to open the other one. And the transformers would still get half the input on the primary, so they still work somewhat, so I have picture AND a huge current draw on the power supply.
When I get home tomorrow I'll check the signal on the transformer(s), should be 24Vpp, since it's H-Bridge driven. Also, I'll double check the MOSFETS. But why would they burn out after only a couple of minutes?
@wraper: thanks for the tip