I changed the function of c1 and c2 around. this also means the L2 is connected in reverse, outside rim (grounded) on C2
It simply makes a more powerfull impulse in L2:
- C2/L2 connection (outside rim L2) gets to see the back emf impulse. giving a maximum negative voltage.
- While the C1/L2 connection (inside rim L2) is being resonant, giving a maximum positive voltage.
this outside negative with inside positive results in a bigger voltage difference over the whole of L2, during the impulse.
I also changed the negative DC offset connection to C2/L2
The negative impulse, now reaches a quicker maximum, the 500V maximum of the IRFP460 makes it impossible to step up the voltage higher, as the body diode starts avalance and cuts the voltage off.
To avoid this, I slightly slowed down the impulse, by adding C5 parallel over L2, 700pF. Its small capacitance is charged up by the back emf, and this adds some time to the discharge, making the impulse wider, and lower in voltage.
Now the back emf impulse voltage is lower (and loinger in duration), I can Increase the current and voltage of the dc power supply again. resulting in a higher voltage resonant sine in L2
I added the changes to the picture below in RED
The resonant sine of L2 at C1/L2 now doesn't show the impulse anymore, but is a flawless sine wave.
The circuit still works the same and can light a 28W lightbulb,
But it does look, like it needs less power for equal light. I tested this without proper tuning. So when tuned better, I should be able to see how much more...
Another thing could be using a 900V SiC mosfet, and doubling the voltage of D1 by putting 2 diodes is series. But I havent done this yet, because the capacitors also need to be stepped up, to deal with these increased voltages