A potentiometer controlled Varicap diode may help.

what I noticed: you can vary the frequency from that semi-adjustable resistor

The 5 turns are in parallel that make as much as a turn but has a high current
the 28 turns would be equivalent to the 3 turns in Ruslan's system with high current and high voltage at serial resonance.

Quote from: conico on February 03, 2021, 07:30:02 AM
what I noticed: you can vary the frequency from that semi-adjustable resistor

Thanks conico. If the frequency is matched to the primary LC, will this circuit behave as a ZVS driver?

Quote from: conico on February 03, 2021, 07:30:02 AM
The 5 turns are in parallel that make as much as a turn but has a high current
.

No, it is 5turns in series but made out of five wires in parallel. Like 5T with very thick cable.
Yes it is the half circuit of Ruslan what ever that means.

ok, but I don't see enough space for 5 turns of 5 wires each turn,
What does ZVS mean?

Yes, there is no space at all. But i saw his video and i counted them turn by turn. It was difficult but he did it. Perhaps the real diameter of his wires might be smaller than what they look like. I tried with 1mm on same core but i had not chance of doing it. I made it only by using 0.75mm wire for secondary and 4mm primaries on the top.

ZVS means zero voltage switch. See mazzilli driver below. It switches when voltage is zero and so it handles heat much easier than normal push pulls. I was just wondering if a normal push pull will operate the same if we attach a cap between drains like the chineese.