ZVS Driver, Intermittent Operation Question

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Dave Xanatos
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ZVS Driver, Intermittent Operation Question

Post by Dave Xanatos » Tue May 17, 2016 12:58 am

I have built a ZVS Driver, using a 4000 turn secondary from amazing1.com, and a common schematic for a ZVS from the internet. Photos/schematic below.

The driver works intermittently - specifically, when I apply power (13.8v at 25 Amps available) and POKE the primary coils... physically poke them. Then the unit jumps into action and I get an arc at the output of the flyback. Video is here:


Below are the images of the driver PC Board & schematic. Can anyone help me, based on the information presented, determine if I have to increase/decrease the number of turns on each primary section, or if I have a capacitor problem, or...??? I have tried opening the space between the coils as well as closing, and increasing the air gap between the two halves of the ferrite core of the flyback, to no avail. I'm not really sure why I would get arc only after poking the primary.

When I do get an arc, my current draw is only about 2 amps... much less than I was expecting.

Thanks for any guidance or feedback... no pun intended...
ZVS Board 2.jpg
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Dennis P Brown
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Re: ZVS Driver, Intermittent Operation Question

Post by Dennis P Brown » Tue May 17, 2016 2:53 pm

In my (VERY LIMITED) readings on this very subject, the writer mentioned that the inductor's circuits can be balanced such that, in theory, they will not oscillate until something causes the two circuits to get out of balance (voltage variance?) and then they will oscillate. Your issues sounds a bit like this issue. Maybe changing the primary inductor to a different value might do the trick - guessing here; others here know far more and may weigh in ... .

Not sure if the limit in current draw is due to your power supply (since no details on it are available.) My power supply's transformer saturated out and limited my input to 28 volts and a few amps max. I am going to try a far more powerful transformer to test this idea.

Also, very nice ZVS design/build!

Jeroen Vriesman
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Re: ZVS Driver, Intermittent Operation Question

Post by Jeroen Vriesman » Tue May 17, 2016 5:44 pm

Two things to check:

I cannot see it clearly on the picture, but maybe your 470 ohm resistor is 4700 ohm? (third ring red?)

But more likely: your 13.8v power supply might have a high impedance for high frequencies.
So try to put a good capacitor (low impedance, high frequency, high current) over the power supply close to the board, maybe low esr elco of 100uF with high frequency ceramic of 470n parallel.

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