ZCS for SSTC without E class??

[Binukrockzzz]

I was wondering if there was any way to use ZCS in a normal, non DR, non class E SSTC...

Is there any way that something like this is possible??

[AstRii]

If I understand that correctly, when the load current on the primary is much higher than the magnetizing current, the primary current will be sinusoidal (assuming the secondary current is sinusoidal). Then with some clever feedback circuitry like PLL you can set the phase of the current to be close to in-phase with the output voltage of the bridge.
You can see this phase setting on a PLL driven SSTC from Jakub Tejiščák here:
 

[AstRii]

A quick parametric LTSpice simulation confirms my statement above:

[davekni]

I was wondering if there was any way to use ZCS in a normal, non DR, non class E SSTC...

Is there any way that something like this is possible??

You can see this phase setting on a PLL driven SSTC from Jakub Tejiščák here:

Yes, a PLL is probably best way to adjust to ZCS for any given SSTC design.  Some SSTCs get lucky and hit ZCS by chance.  High coupling helps, as does a high secondary Q.  If there is just enough delay in the feedback, but not too much, ZCS can be the result.  Perhaps a feedback delay adjustment would suffice at least in some cases.

[Binukrockzzz]

Thank you AstRii and Dave for taking your time to reply to my message.

If there is just enough delay in the feedback, but not too much, ZCS can be the result.  Perhaps a feedback delay adjustment would suffice at least in some cases.

I have an adjustable RC delay in my feedback, but when I adjust it even a tiny bit, the output decreases significantly...

If I understand that correctly, when the load current on the primary is much higher than the magnetizing current, the primary current will be sinusoidal (assuming the secondary current is sinusoidal). Then with some clever feedback circuitry like PLL you can set the phase of the current to be close to in-phase with the output voltage of the bridge.

I thought about PLL, but it sounds a bit complicated to implement. I've found a circuit online for a PLL SSTC, but the diagram says 300-400khz and my planned secondary resonates at around 201 kHz (JavaTC). I want to know how to tune such a circuit to drive a lower frequency secondary... The circuit is attached below.

[AstRii]

PLL sounds complicated at first but it's actually quite simple. I recommend watching this video:

If you want the circuit to oscillate at lower frequency, you need to adjust R1 and R2. The needed values can be read off the datasheet:

Although you can just put some resistors without any thinking and simply see what frequency range does it provides. And then adjust the values.
I recommend using bigger timing capacitor because using small capacitances like <100pF leads to different center frequency every time you run the circuit..

For reference I've build two PLL coils (although without ZCS tunning):
https://www.uhvlab.org/ctu-sstc
https://www.uhvlab.org/sstc-ii

The best running PLL coil I've seen is the already mentioned Jakub Tejiščák's coil, although I've never quite understood how does his approach achieve ZCS:
https://www.vn-experimenty.eu/teslov-transformator/sstc/sstc-5.html
He is modifying the value of R2 to get ZCS, but in my understanding, R2 is there only to set the frequency range at which the PLL can operate. Somehow it works though. Maybe someone can clear this up?

[Binukrockzzz]

Thank you for recommending me that video. I now understand how a PLL works.

The best running PLL coil I've seen is the already mentioned Jakub Tejiščák's coil, although I've never quite understood how does his approach achieve ZCS:
https://www.vn-experimenty.eu/teslov-transformator/sstc/sstc-5.html
He is modifying the value of R2 to get ZCS, but in my understanding, R2 is there only to set the frequency range at which the PLL can operate. Somehow it works though. Maybe someone can clear this up?

That's the part that I dont understand too. I know how the PLL oscillates at the right frequency, but how is ZCS achieved?