Half bridge voltage waveform not following PWM
I do not know what physics universe that you live in but the Vin to that chip can be no more than 40V DC. It is not suitable for connection to 240VAC. If you have not already burnt the chip I would guess that it will soon be cooked. 

I saw nothing in the data sheet that would indicate that the above circuit you show is suitable for connection to 240VAC. If there is more to your circuit then you are going to have to show that otherwise the question is unanswerable other than to watch for smoke.