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Registered Member #1902
Joined: Fri Jan 02 2009, 07:59PM
Location: Lancaster, NY
Posts: 75
I bought some cores for my class e coil awhile ago I have yet to get the drive to work right. The drive rings badly every time i draw sparks not sure why but I believe its the cores I am using at the moment the have a permabity of approx 2500. Very low from what I have read. If someone could recommend a core type for a drive of 700 khz would be awesome. Thanks
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
You don't need a gate drive transformer for a class-e, especially if you're frequency is only 700kHz.
Just use an IXYS IXDD414 gate driver. These are used in many class-e RF amplifiers and provide more than enough drive power for most high power MOSFETs at frequencies up to 8MHz.
We use them for our class-e designs which switch at 4MHz and drive IXFN16N50s.
Registered Member #1902
Joined: Fri Jan 02 2009, 07:59PM
Location: Lancaster, NY
Posts: 75
Well right now I'm running the gate drive with the UCC non-inverting driver connected to ground via .1uf cap and the GDT primary. I need a GDT for isolation because I'm using a 30-0-30 x-former fed through a doubler for 120VDC for the B+ and using the center tap for the low side electronics. In this situation the ground for the UCC and the Source are not at the same potential which requires me to use a GDT. So i would like to know if anyone has had success with GDT at this high of a freq and what material to use. Thanks EVR I know your trying i just have to be more clear about what I'm talking about.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Just use Fair-Rite Type 77 or Type 78 material. This is what i've used before on my class-e gate drives that used gate transformers. These were good up to 8Mhz.
Registered Member #1902
Joined: Fri Jan 02 2009, 07:59PM
Location: Lancaster, NY
Posts: 75
Cool thanks a bunch! I sure hope this fixes the ringing on my gate. Every time i draw sparks the leading edge of my drive waveform rings uncontrolably turning the fet on and off several times a cycle, even clamped with 12v zeners and a 10 ohm gate resistor! Otherwise my gate waveform looks pretty descent. As of right now I really hope it's just my GDT and not something else.
Registered Member #1902
Joined: Fri Jan 02 2009, 07:59PM
Location: Lancaster, NY
Posts: 75
It's just like ward's class e coil only diff is i'm feeding 120vdc to the high side. And low side eg the 555 ucc are getting 30vac rectified and regulated to 12vdc. Same transformer powers both high side and low via tapped windings and doubler. Another difference is the gdt but thats pretty obvious hehe. Any other info needed?
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GDT Core Material
