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Zvs driver Questions. lots of them

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StormInABottle

Thu Jan 31 2013, 04:15PM

Registered Member #9252 Joined: Fri Jan 04 2013, 06:27AM
Location: Andromeda
Posts: 253

First
The mosfets the shop has are IRF640N i bought 4. In hopes of paralleling them. One is capable of 200 volts at 18 amps. So if i parallel 2 togeather. What are the specs of the final product

The power supply for the zvs is a 200 watts 36 volts ac transformer. Spits out 50-40 volts after rectification..
Also should the zenners be 15 or 12 volts. I have booth
Would the fr607 diodes work..

And people say the ZVS is all about inductors and capacitors

So for the inductor. I have a spare old flyback transformer's core.. How much turns of wire should i put on that core to get a nice higher voltage not higher current zvs driver..

And... I could not find mmc or mkp types of capacitors.. So i bought ceramic.. IS there anything i can do to make the ceramic things act like mmc or mkp..

Also... For a dual flyback zvs...

Should i like. Make 4+4 turns in each of the flybacks then parallel those

Or 4 on one. and 4 on the other. And series them. Alsooo. I am able to buy the EXACTLY 2 same flybacks. The same model etc...
The model is a large nice flyback that gives spectacular results. :)

Also i can go NAUGHTY MODE. And buy another transformer like the one i have for some 72 volts in or something

zippotix

Thu Jan 31 2013, 04:55PM

Registered Member #5208 Joined: Thu Jun 07 2012, 06:12PM
Location:
Posts: 86

Hi there, I'm not much of help but I would suggest using 15v zener, or if you have 18v. Last time I think I noticed slightly better performance on higher value zeners, but I'm not sure if it doesn't increase the stress of other components.
Regarding paralleling mosfets, I asked the same question some time ago, and apparently it's good idea, you can feed more power into it.
Don't waste money on transformers (I wanted to do it as well), just buy a MOT and rewind it to the voltage you need, cheap and durable.

StormInABottle

Thu Jan 31 2013, 05:17PM

Registered Member #9252 Joined: Fri Jan 04 2013, 06:27AM
Location: Andromeda
Posts: 253

Naw i dont want to rewind a mot i 'd perfer a high voltage mot.. i have lots of money anyway.. And a transformer like that i am using costs less than a mot. So 15 volts zenner. And please give me the mathemaics and values for the mosfets. And tell me if the diode is going to work. etc.

zippotix

Thu Jan 31 2013, 05:25PM

Registered Member #5208 Joined: Thu Jun 07 2012, 06:12PM
Location:
Posts: 86

I think the diode will work, but from what I see it's a fast diode. You should be using ultra fast diode, I would wait for other users to chime in. I don't think the inductor you're planning to make will work, it needs an air gap. Dri0m made an inductor with a hollow PVC pipe if I recall correctly. Don't know if ceramic capacitor will work.

Sulaiman

Fri Feb 01 2013, 06:42AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

First
The mosfets the shop has are IRF640N i bought 4. In hopes of paralleling them. One is capable of 200 volts at 18 amps. So if i parallel 2 togeather. What are the specs of the final product
__________________________________________ ________________
Two mosfets in parallel would have almost double the current capacity of one.
Use one resistor per mosfet gate / do not directly parallel all three mosfet leads
as there is a chance of 'parasitic' oscillation at very high frequency that could cook your mosfets.
_________________________________________________ ___________

The power supply for the zvs is a 200 watts 36 volts ac transformer. Spits out 50-40 volts after rectification..
Also should the zenners be 15 or 12 volts. I have booth
Would the fr607 diodes work..
___________________________________________ _____________
either will work, the 15V allows slightly higher current, the 12V slightly higher frequency.
FR607 Trr=500nS from a datasheet, ok for 10's kHz.
_________________________________________________ _______

And people say the ZVS is all about inductors and capacitors

So for the inductor. I have a spare old flyback transformer's core.. How much turns of wire should i put on that core to get a nice higher voltage not higher current zvs driver..
_________________________________________ ___________________
If the core and airgap are similar to your resonant core, start with twice as many turns as the total for the resonant core.
_________________________________________________ ___________

And... I could not find mmc or mkp types of capacitors.. So i bought ceramic.. IS there anything i can do to make the ceramic things act like mmc or mkp..
_________________________________________________ ___________
Ceramic capacitors are more lossy than KP types but can withstand quite a lot of self-heating so are quite robust.
_________________________________________________ ____________
Also... For a dual flyback zvs...

Should i like. Make 4+4 turns in each of the flybacks then parallel those

Or 4 on one. and 4 on the other. And series them. Alsooo. I am able to buy the EXACTLY 2 same flybacks. The same model etc...
The model is a large nice flyback that gives spectacular results. :)
_________________________________________________ ______________
The zvs would work as 'normal' with N + N turns per primary,
with multiple primaries in parallel.
Two similar primaries in parallel will be half of the inductance of one,
so with fixed primary capacitance the resonant frequency will be 1.414 time higher.
Due to the resonant capacitor the zvs MAY work with two separate primaries,
there may even be an unexpected benefit.
_________________________________________________ ______________

Also i can go NAUGHTY MODE. And buy another transformer like the one i have for some 72 volts in or something
________________________________________ _______________________
PI x 72 = 226 V peak which is more than the voltage rating of your transistors.
_________________________________________________ ______________

StormInABottle

Fri Feb 01 2013, 08:23AM

Registered Member #9252 Joined: Fri Jan 04 2013, 06:27AM
Location: Andromeda
Posts: 253

Inductors do not need an air gap. I can make a inductor on a rod of ferrite. But a toroid is a common method to save space. And i do not even care about space

StormInABottle

Fri Feb 08 2013, 10:00AM

Registered Member #9252 Joined: Fri Jan 04 2013, 06:27AM
Location: Andromeda
Posts: 253

I got new mosfets. robust nice ones.. Tommrow i get the diodes and the resistors.. The specs of the new re built zvs is like.. Irfp250N 15 volt zenners half a watt. 10kohm resistors 2 watts. 470 ohm resistors 5 watt. Please suggest a diode :3 cause i dont really know what to get :P a inductor wound around a old flyback ferrite core. input is 50 volts from a rectified 36 volts transformer Thank you

Harry

Fri Feb 08 2013, 03:27PM

Registered Member #4081 Joined: Wed Aug 31 2011, 06:40PM
Location: UK
Posts: 139

Use a couple of UF4007's
They're cheap and plentiful

Ash Small

Fri Feb 08 2013, 04:17PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Arcingnoob wrote ...

Also... For a dual flyback zvs...

Should i like. Make 4+4 turns in each of the flybacks then parallel those

Or 4 on one. and 4 on the other. And series them. Alsooo. I am able to buy the EXACTLY 2 same flybacks. The same model etc...
The model is a large nice flyback that gives spectacular results. :)

I'd try putting the two flybacks back to back, and winding the centre-tapped primary around both, assuming space allows for this. (One primary, two flybacks)

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