Pwm driving half bridge

[captainshahid]

hi everyone

i am confused here that in a half bridge mosfet driver opposite pwm drive upper and lower mosfet, as soon as duty cycle increases voltage increases to form a sine wave half cycle but for negative cycle how they works?

 

[elecbaba]

Supply is + and - . GND is at 0 volts. Now voltage is either positive going or negative going according to postive half and negative half cycle.