I am trying to build a PWM controller as shown in the figure below. Considering the example that my input is 5V and output is 10V and I need a duty cycle of 50%.

Ref for image: https://i.sstatic.net/0kkWg3nC.png

My doubt was what happens once the output is 10V and the error is zero? Would the output of the error amplifier be zero? In that case then the comparator output would also be zero and there would be no regulation right? What am I missing here?