Power Invertor

Hi, guys i am currently onto designing a power invertor, i have obtained a sinusoidal signal from controller but its a dc sinusoidal and i need to make it an ac sinusoidal signal. I have obtained pwm from controller and on giving it to a low pass filter, i get my sinusoidal signal .I am giving this pwm to an H-bridge to get an amplified a.c pwm. I have attached the hex file and circuit. But the output from h bridge varies too little. I need 12V potential difference across my h-bridge output. You can test it yourself to know what i am talking about, Can anyone make the required changes in this circuit. I use proteus 7.8, do check design file on it and OC0A is giving me my required pwm on pin 26 and yes don't worry about its frequency, i ll change it later.