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Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
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Posts: 608
[quote]
jdub1581hv wrote ...
So I fixed the calculator link (forgot to put the http in) .. Sorry bout that.
Also here is another good read.. helped me out at least though it is geared more to class F Class F and Inverse class F Covers it all as far as getting the design down, switching behavior, filtering etc.. I'm leaning more to the E/F hybrid myself, as to be both efficient and powerful (F is less efficient, yet more power out from what I read.. but can reach 100% as well with precision parts and design).
And also, I think the impedance matching and component reduction finally started making sense last night. For me only being able to read online and not converse with live people (aside from here) has made this quite the adventure...
I have a couple Cree SiC Mosfets 900v 36a I want to use for this, but for now I'm too timid and don't enjoy $10 smoke rings.
So for now I have 3 CEFF630 mfets, 10a, 650v, low Ciss 800pf / Coss 150pf , and rds of .27 - .4ohms I'm a little worried about the dissipation only being 35W...
There also seems to be a lot of different ways to deal with drive signal, but I'm debating Res. Feedback vs Xtal .. I don't think the 4046 pll would have any problems, but I've read it has its own intrinsic flaws...
Still curious if anyone could give some design guidelines as far as where to start.. Start with resonator, fets, frequency? I've got about 15 resonators to choose from, starting: 1/2"dia x 3" -> 6"dia x 24" , with a rough F range of 6mhz down to 150khz ...
jdub1581hv wrote ...
Another good read..
This is a step by step design for class e power amp MUST READ !!
Inducktion wrote ...
jdub1581hv, you have to be careful with SiC Fet's.
Pay heavy attention to the voltage they can handle on their gates.... They do not tolerate negative swings more than like, -5 volts before they start to have issues/break down.
What do i check for in the specs to calculate the switching speed max? There has to be something better then an IRFP460 fet
Edit: Try out multi sim blue, Mouser offers it free with there parts database to simulate circuits
Registered Member #58280
Joined: Sat Jan 09 2016, 06:48AM
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Posts: 43
What about the secondary coilform in class E tesla coils? Is there any data on ideal height, turns ratio, wire, form material. PVC has pretty bad dielectric losses at 4Mhz, does that really make a difference in the big scheme of things?
Registered Member #55219
Joined: Tue Jun 09 2015, 11:21PM
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Posts: 80
Inducktion wrote ...
jdub1581hv, you have to be careful with SiC Fet's.
Pay heavy attention to the voltage they can handle on their gates.... They do not tolerate negative swings more than like, -5 volts before they start to have issues/break down.
Yup .. I am aware :) .. I 'try' to get as much info beforehand as possible. I am saving these as I said for when I get a stable circuit going.. Through the Cree website I was able to download schematics for an 8kw SiCfet 3 level resonant ZVS driver, with a nice section on the drive circuitry. Need to adapt for my switches, but a good reference none the least.
I'm also aiming for the lower F due to not having a real scope. Right now I'm running an arduino scope / LCF meter with lcd (yeah I know... -_-) but it's fairly accurate for what it can do. Especially for measuring the inductors at small values and caps into low pf up to about 1mf (added circuitry) so that's at least been a help. (Anyone who wants the code let me know, I did not write it, though fixed a lot of code errors and adapted it to the seeed2.8"tft) I'll apologize up front for the ton of questions and long-fingeredness.
I did attach the ZVS schem though for those who want it, or go get the whole package yourself. ]zvs_schematic_v3.pdf[/file]
Registered Member #55219
Joined: Tue Jun 09 2015, 11:21PM
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Posts: 80
ZakWolf wrote ...
How do you ground a HFSSTC ?
Many say a counterpoise would work though Ive had no probs with connecting to mains ground.. Really depends on environment and how anal you want to be...
Registered Member #3114
Joined: Sat Aug 14 2010, 08:33AM
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Posts: 608
jdub1581hv wrote ...
ZakWolf wrote ...
How do you ground a HFSSTC ?
Many say a counterpoise would work though Ive had no probs with connecting to mains ground.. Really depends on environment and how anal you want to be...
Gotcha
So would a mains power design be possible? From what I have read the power needs to stay pretty constant to feed the MOSFET class e portion. I think is not using 150v as it says in his schematic since the MOSFET sees about 3.5 times the input voltage. Not possible with at least that FET. I think he meant 50v, if you look closely in the background of his close up shots of the coil you can see the yellow and black twisted pair of wire going to his 50v power supply he made in another project. However, powers his from 150v. Is it actually 150v or 170v as it becomes after being filtered?!?
Registered Member #55219
Joined: Tue Jun 09 2015, 11:21PM
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Posts: 80
ZakWolf wrote ...
Gotcha
So would a mains power design be possible? From what I have read the power needs to stay pretty constant to feed the MOSFET class e portion. I think is not using 150v as it says in his schematic since the MOSFET sees about 3.5 times the input voltage. Not possible with at least that FET. I think he meant 50v, if you look closely in the background of his close up shots of the coil you can see the yellow and black twisted pair of wire going to his 50v power supply he made in another project. However, powers his from 150v. Is it actually 150v or 170v as it becomes after being filtered?!?
Well he's probably using a doubler/3x , regarding his voltage.. And yes at Mains voltage you would want a fet around 4.5x the input, includes a safety margin. Look at Steve Wards again... He had up to 150v over what it should have been... Which is probably why a few of my early on attempts blew up..
Registered Member #58280
Joined: Sat Jan 09 2016, 06:48AM
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Posts: 43
What is a good ultrafast, low capacitance MOSFET for single ended class E? I'm having difficulty choosing a MOSFET balancing higher input voltage for more power, vs lower gate capacitance for faster switching. Right now I'm using the IRF630
Registered Member #55219
Joined: Tue Jun 09 2015, 11:21PM
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Posts: 80
Chris_Knight wrote ...
What is a good ultrafast, low capacitance MOSFET for single ended class E? I'm having difficulty choosing a MOSFET balancing higher input voltage for more power, vs lower gate capacitance for faster switching. Right now I'm using the IRF630
I am wondering too...
With class E I think(?) the Zin -> Zout is the more important factor.. So you'd have to look at how the Ciss reacts at your frequency and balace with the load .. For many switches the Ciss seems to average around 2nf..
But these are assumptions on my part so don't take it verbatim...
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Class E? Class E...
