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MicroTesla

Sun Oct 04 2009, 05:51PM

Registered Member #2394 Joined: Sun Sept 27 2009, 11:32AM
Location:
Posts: 6

Hello guys,
Today I've build my ZVS flyback driver. I used IRFP250, BYV-29 diodes, 50uH inductor and 0,1uF resonant cap.
It works, but it draw only 1ampere at 12v input, and the arcs are only 2cm large.
My power supply is able to power more than 5amperes, so what's the problem ?
Thanks
PS : I'm french so sorry to the bad english...

...

Sun Oct 04 2009, 06:35PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

How many turns are you using on the flyback core?

Also, the way your board is arranged there is a huge amount of extra inductance, which could cause problems at higher powers, although for low power runs it should be acceptable.

Also, double check your circuit for loose wires, it is a really simple circuit so there is not a lot to have wrong, but connecting the diodes incorrectly will give the results you show.

MicroTesla

Sun Oct 04 2009, 07:35PM

Registered Member #2394 Joined: Sun Sept 27 2009, 11:32AM
Location:
Posts: 6

I'm using 10 turns center tapped on the ferrite core.
The diodes looks correctly connected, but tomorow I will check it.
I will also short the wires to reduce the extra inductance.
If I increase the value of the cap, the sparks are smaller (for 1uF I get 4mm sparks, and for 0,1uF I get 2cm sparks).
Thanks for posting.

MicroTesla

Mon Oct 05 2009, 04:58PM

Registered Member #2394 Joined: Sun Sept 27 2009, 11:32AM
Location:
Posts: 6

Ooops !
Today I've check the diodes's connections, everything was correct, but when I connect the driver, it draw 2,5amperes, and there is no output.
The flyback emits a noisy buzz when the driver is connected.
What's the problem ?
Thanks.

vasil

Mon Oct 05 2009, 06:25PM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

Your flyback is "hors d'ousage' (is correct?)
Get a new flyback.

Zenador

Mon Oct 05 2009, 06:25PM

Registered Member #1733 Joined: Thu Oct 02 2008, 03:17PM
Location: Hamilton, ON, Canada
Posts: 100

... wrote ...

Also, the way your board is arranged there is a huge amount of extra inductance, which could cause problems at higher powers, although for low power runs it should be acceptable.

... is right. Check-out Mads' setup here -

with his point to point solder job. I have built all my ZVS drivers this way. One thing I have deviated from is the single heatsink. My original build looked similar to yours, and caused problems. Despite the insulation between the MOSFETS, the tabs (drain) are too close in my experience. By chance I found that my fets were arcing to each other through the heatsink. That arc was 5mm in length, more than enough to arc from tab to tab directly on your setup.

If the FBT is buzzing, it may be arcing internally. My FBT's will buzz if I killed them, or if it's running and the HV/GND terminals are too far apart (in the process of killing it.)

A quick test of your mosfets may be in order. I tested all my suspected dead ones with a DMM and a 9V battery, and only half were toast.

MicroTesla

Mon Oct 05 2009, 08:00PM

Registered Member #2394 Joined: Sun Sept 27 2009, 11:32AM
Location:
Posts: 6

vasil wrote ...

Your flyback is "hors d'ousage' (is correct?)
Get a new flyback.

"hors d'usage"
I've made a new PCB board today and it works with another flyback, but I have the same problem : the driver draw only 1ampere, and my power supply is able to power 5amperes.
The sparks are 2cm long, but I've noted that they are brighter with the new pcb board.
Another question : how many amperes a car battery is able to power ?
Thanks for posting.

Arcstarter

Mon Oct 05 2009, 10:12PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Well, you might want to try more capacitance in the LC circuit. Not sure what affect that may have. What kind of power supply are you using? I am not sure why, but i used a smps from a laptop, which could supply more than 2 amps but it would only pull .4 amps (for testing). I have still not figured that out, but when i used a smoothed supply from a transformer i could easily pull 300 watts, and i made a new one that i could pump 720 watts continuous with a homemade transformer.

A car battery can supply many hundreds of amps. A short circuit would be more than 1000 amps in a typical car battery.

MicroTesla

Tue Oct 06 2009, 04:25PM

Registered Member #2394 Joined: Sun Sept 27 2009, 11:32AM
Location:
Posts: 6

If I try a larger capacitor (like 1uF or 0,68uF), the spark is only 3-4mm. I'm using a 12v transformer rectified and smoothed, it can power more than 5amperes.
My driver draw 1,13amperes at maximum.
Thanks.

Dr. Dark Current

Tue Oct 06 2009, 05:14PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Try to reduce primary turns to 3+3 and see what happens.

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