Hello Tahmid can you please help me to think why using square wave at 1KHZ I am getting immediately on the output of the H-bridge 7V AC when applying 100VDC even above 100VDC I stay with those 7VAC.;Please help me.Feed the 555 output to a flip flop. Feedback the outputs of the flip flop a high/low side driver which will drive the four MOSFETs in the H-brigde.
Why do you want to use the 555 chip? Can't you use SG3525 or SG3524 or TL494? Or even the CD4047?