This is a circuit for switching the transformer at high frequency and so that we get ac on the secondary side. A voltage multiplier circuit is connected to the secondary of the transformer which will give a high voltage dc at the output. That dc voltage is then fedback which is shown in the figure as **OUTPUT FEEDBACK**.
In this circuit i am not able to understand 

  1. the use of 220microFarad capacitor which is connected with the centre tap of the transformer

  2. How is feedback circuit working, Is it a window comparator circuit?

  3. Use of transistor, I mean the Square wave which we are getting can be directly fed to the Mosfet but why have we used transistors?

4. I have uploaded a photo in reference to my 3rd question. I have simply removed transistors in this and i did its simulation in proteus and is working. I am unable to understand the use of transistor in this??[![new circuit][1]][1]

[![enter image description here][2]][2]


  [1]: https://i.sstatic.net/Jso6s.jpg
  [2]: https://i.sstatic.net/EFldE.jpg