PWM to phase shifter

In some situations it can be useful to vary the phase between two square waves. Here, two D-flipflops ‘A’ and ‘B’ convert the PWM signal into a square wave in the standard manner. However, D-flipflop 'A' is clocked by the rising edge of a pulsewidth modulated (PWM) signal, whereas D-flip flop 'B' is clocked by the falling edge.