Your R1 of 1k ohms was making a voltage divider feeding 8.7V to the gate instead of 0V to turn off the Mosfet.
Since the maximum allowed Vgs is 20V for the IRFZ44 Mosfet then R1 is not needed with your supply of only 12V.
All clear.After removing the 1K resistor everything worked perfectly.Now the driving hardware & output wavforms are ok.
For testing I just hooked a 12-0-12 / 230V (1A) transformer & checked the output voltage.I see only 145 VAC.And my FETs are extremely hot even without a load on AC side.Battery voltage is 12.5V.
Oddly enough, the ratio of target to actual output voltage is 1.586
Divide 12 (input) by that, to get the primary voltage needed to get around 230V out, and you get 7.56V
That pretty much matches your UPS transformer primary!
The datasheet for the FPQF-55N06 Mosfets show that they need a Vgs of 10V to fully turn on. If the Vgs is less than 10V then they get hot and the transformer gets less than the 12.5V.
What frequency is the PIC driving the Mosfets?
The datasheet for the FPQF-55N06 Mosfets show that they need a Vgs of 10V to fully turn on. If the Vgs is less than 10V then they get hot and the transformer gets less than the 12.5V.
What frequency is the PIC driving the Mosfets?