The rate of change of the flux in the primary winding induces a voltage in a sensing winding, which voltage is integrated and used to control the on time of the switching device so as to control {HEAD ~ the flux} in {TAIL ~ the main coil} 
The rate of change of the flux in the primary winding induces a voltage in a sensing winding , which voltage is integrated and used to control the on time of the switching device so as to control { HEAD ~ the flux } in { TAIL ~ the main coil }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL