I want to ask about how the Integrated circuit decides the proper (di/dt) for next cycle , the voltage across an inductor/transformer is L*(di/dt) the Integrated circuit TNY289 as I understand it ramps up current so that (di/dt) is constant and consequently the voltage across an inductor/transformer is constant during ramp up (on time) , my question does the decision about (di/dt) for next cycle is to maintain constant Voltage on drain constant (Vsupply - L(di/dt)) ? On what criteria this decision is taken ? to maintain what constant at what value ?

I understand also that the slope should be (di/dt)= Ilimit/Ton , to change (di/dt) does Ilimit only change or Ton also ?