Modified Sine Wave Inverter

Hi Guys. I'm busy building a modified sine wave inverter based on a schematic I found on the internet. I'm using a Pic18f452 for my controller and IRFZ44 mosfets. Currently I'm testing the inverter using a very small centre tap transformer to switch 12vdc to 220V AC at 50hz. The problem is the primary input voltage is bad looking due to the transformer primary being switched causing back emf and there is nothing in the circuit to absorb the voltage spikes. I need help with a snubber circuit of something to clamp down these voltage spikes. I have included pictures of the circuit diagram, unloaded Mosfet output waveforms and the transformer Primary voltage waveform. Any help would be appreciated. Thanks

 

I'm getting my transformer soon. Its an old microwave transformer thats being rewound to 12-0-12 on the secondary and then I will try to put a 100watt light bulb on.

 

Thanks. I will give it a try

 

I found this article on the internet http://www.homemade-circuits.com/2013/10/modified-sine-wave-inverter-circuit.html?m=1

My unloaded waveforms compare with their's and when I load my transformer the voltage spikes seem to clear out a bit . I'm going experiment and modify my code to produce sine wave pwm output and then use LC filter on the primary to try and get better results. Will put up some waveform when I done.