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some Questions regarding ZVS flyback driver

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raff

Thu Aug 27 2009, 08:50AM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

Hi guys,

I have some questions ..

#1> with supply of 50Vdc , the 470R/2Watt -heats up- in a few seconds from power ON , what value/wattage to use for an input supply of 50V? should I also UPPER the voltage value of the zener?

#2> I have tried an AC flyback(with 0.2mm airgap) , but never got to work off sparks from it with 5T+5T primary (but 15T+15T does the trick) how come? cap Im using is 1.5uF/400V..supply was 13Vdc @ 1.5A ... now with a DC flyback(also has stock airgap), I did manage to make it work with 5T+5T, but lesser spark compared to my AC flyback... here is a video of the AC flyback used

Im using IRF630A at the moment because our local parts dealer ran out of stock with IRFP250... I also have here a 38-0-38Vac @ 8A transformer (would equate to more than 50Vdc) .. I never tried it , might damage the IRF630A

raff

Thu Aug 27 2009, 10:19PM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

update:

DC flyback is BETTER with the zvs flyback driver..the cap <1.5uF> was destroyed, thats why the LESSER spark compared to the AC flyback...

I ran it using 20Vdc(unloaded) @ 2A and I got nearly 2" on spark length..

wow!

video

again, anyone care to answer my questions above?

eniyuki

Fri Aug 28 2009, 10:18AM

Registered Member #2148 Joined: Tue Jun 02 2009, 02:22AM
Location:
Posts: 62

sir if you increase input voltage beyond 20v /i think/ increase nyo rin yung value of the 2 watt resistor para daw mawala yung parasitic blah blah. Sorry i forgot how they call it.

Cant youtube in my cellph0ne!

Myke

Fri Aug 28 2009, 03:32PM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

You might want to try to use a separate supply for the gates of the MOSFETs. I'm surprised that you haven't hit parasitic oscillations in the gate circuit. People usually just increase the gate pull up resistors. You may also want to increase the number of primary turns so that you don't push the core so far into saturation.

raff

Fri Aug 28 2009, 10:35PM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

hi myke

with supplies of 50V, how many turns for primary should I use? 10 turns perhaps? that core has never been disassembled, im guessing its still got 0.2mm plastic spacer(for air gap) ... so you suggest I just power this up with lower supply voltages(30V) @ >>5Amps ?

@eniyuki
rak en rol bro :)

Myke

Sat Aug 29 2009, 06:14AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

I haven't tried up to 50V so you would have to mess around and see how the primary turns affect the output. If you have many turns, the output current will be higher and if you have fewer, the output voltage would be higher.

If you hit parasitic oscillations, the driver would stop working so you are probably fine with your 50V supply. I was thinking you might try 12-24V for the gate supply and 12-50V for the tank part of the circuit. I'm not sure what will happen though as I haven't tested what happens at that input voltage. I may have to remake my current driver.

raff

Sat Aug 29 2009, 07:12AM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

myke,

I have just read older threads (#37?) regarding powering up tank circuit with higher voltage (24-40) and the "470R & zener" with a separate 12-15V.. though they should share a common ground... still have not tested it though... I was a bit busy wiring up a new power supply for the mazzilli driver.the transformer was from a UPS, wired it backwards :)

I got 12Vac @ 5 A (maybe).... used KBPC3510 bridge diode (35A 1000V) man, even with this diode, it still heats up a bit, it does need heatsinking...

I think ill STOP for now, unless I get my hands on an IRFP250 as switching elements, or else ill kill my IRF630A (heats up a bit also, im using a SMALLish heatsink)

I get close to 2" spark length with with 12Vac(15Vdc) @ 5 A. nice! :)

btw, you said MORE tunrns for MORE current, does this mean WHITER arcs? I get violet arcs with 5T+5T

on the AC line side(220Vac 60Hz), I get almost 80watts reading on my wattmeter with the arcs stretched... power hungry beast! :)

raff

Tue Sept 01 2009, 11:37PM

Registered Member #2315 Joined: Tue Aug 25 2009, 02:35AM
Location: Leyte, PH
Posts: 161

This week , I finally have 2 pcs IRFP250, so I made a board for it and powered it up with 40Vdc @ 8A ... wow! the POWER!

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