Try to build the 4MHz ClassE SSTC

[NyaaX_X]

Thank you Dave.

Ok ,then to the power stage . I didn't start it.

Oh I have another questions Dave . What do you mean that is a DR one for your 13.56MHz. Is that means the first 4MHz richieburnett's one was only a single resonant circuit ? I don't know if the primary LC not resonant. The Class E still can be tuned to ZVS ? And I think there is a huge power difference between yours, 曹sir's 12MHz, richieburnett's uzzors2K's and mine. I mean how to make the HF flame more longer with same input voltage but more current ? I also wonder if your primary and secondary have more less coupling, the secondaey connected to circuit as a "free resonator" will it work?

[davekni]

My 13.56MHz HFSSTC schematic shows primary and secondary inductances and coupling factor:
    https://highvoltageforum.net/index.php?topic=1638.msg12549#msg12549

Beyond that, I don't know the answers to all your other questions.

[NyaaX_X]

Ah Dave. I am saying that , You said that yours is a DR one. Is that means you tuned the series LC "primary" to resonant? (L6,C2,C8,C12) And how about our normal topology?

[NyaaX_X]

Hello, I'm here again.
This time I draw the power stage.

Please Have a see.~
Thank you and have a nice day.

[davekni]

Layout looks fine.  I presume 0.1uF is a placeholder value.

For all this work to drive gate, why not use a better FET than IRFP460?  There are many higher-power FETs with much lower gate charge (lower gate drive power).  Even with IRFP460, you could probably drive GDT directly from NCP81074 chips.

SiC FETs would be great.  There are plenty of good Si ones too.  For example:
TK110Z65Z,S1F
IPZA60R120P7
These are higher voltage and current than IRFP460, much lower gate charge, and in 4-pin packages to allow separating GDT return connection separate from power connection.  (Joined inside FET package.)

[NyaaX_X]

Thank you again Dave~

But...Sorrt I edit the driver and power board a little. Please watch them again in your free time.

Yes the 0.1uF capacitors are like hundreds of picoF for real

Here I found a Si FET seems good. But I'm not familiar to those components. I was keep using IRF and other "famous" FETs this days. I think these old school FETs are commom for ZVS self oscillator or SSTC on the internet.

The SiC FETs usually have not symmetry VGS.. And I think most of them are expensive. Also the TO-247-4 make me to remake the layout.. So maybe when I am good at tuning this circuit. I will try them

Here is the FET I found
https://www.vishay.com/docs/92425/sihg24n80aef.pdf

PS. I see that there are some "via" do not place in the good spot (power board) I will move them tomorrow. And I think I will add more GND via around the input toroid inductor.

[davekni]

The SiC FETs usually have not symmetry VGS.

There are cascode SiC FETs that drive like normal Si FETs, such as UF3C120080K3S.  This part is in a 3-pin package too.  Steve Ward used a cascode SiC FET for his 3kW HFSSTC.  Yes, SiC FETs are generally more expensive.

Here is the FET I found
https://www.vishay.com/docs/92425/sihg24n80aef.pdf

Yes, that looks like a good choice, similar current capability to IRFP460, higher voltage and lower gate charge.
IRFP460 does have a high avalanche energy capability, so would have some robustness to being abused (excess voltage).  However, I think one reason IRFP460 is cheap is because there are many counterfeit sources.  No way to know if a counterfeit part meets avalanche energy or any of the other specifications.

[NyaaX_X]

Yes, and it has faster body diode. I think it can provide more margin for tuning.
Oh and I don't want to drive the power mos directly because tbh isolated driver is more safer for the driver, I guess.

The driver board is 9cm*4cm, and the power board is 6cm * 6cm.

And I buy IRFP460APBF on mouser/digikey, sadly I have killed some of them 

[NyaaX_X]

Excuse me,

I have a problem with my power stage.

If I use wide copper wiring. Do I need to add extra exposure path to add more tin? I set the max current flow can up to 20A for the MOSFET to resonant part. And the PCB copper will be 2oz.

Sorry for not a clearly depiction.

[davekni]

Do I need to add extra exposure path to add more tin?

No.  For high frequency AC, adding tin increases resistance due to skin effect.  DC component of current improves, but AC component will see higher resistance, much higher at 4MHz.

[NyaaX_X]

Ah.. So why happen? Because the high frequency current been pushed to tin and they have more resistance to copper?

And so, which is better below ? Or any problem with the layout ? Please have a look.

And the exposure copper can add or not add tin



Thank you !!