Since I had make a bifilar inductor for a boost DC DC converter, the trigger coil 0.22 mm/Dia one of the two bifilar coil is used for a trigger to the MOSFET gate and the Dutty cycle of the wave ~75% I saw in my oscilloscope was the blue line AC wave as you see above.Too mach waste of current through the driven inductor plus the other problem should follow.Then I make this circuit to trim and square the trigger pulse with an adjustable Dutty cycle.The two transistor on the left with the zener diode on the net are a VR, and feed stable voltage to rest of the circuit this is important because any change to load resistance should effect the output voltage through trigger coil thus effect the Dutty cycle of the pulse to the MOSFET's gate.The frequency change slightly under load resistance, changes either way with or without the this circuit maybe you see some deferences on Dutty cycle, that's normal as a frequency following.The trigger coil have double turns than driven inductor coil the same path way of wrapting,the end of trigger coil connected to the start of driven coil and both to (+V),a high watt resistor is need to limit current.
