Problems getting ZVS driver to work / High Voltage / Forums

Forums

4hv.org :: Forums :: High Voltage

« Previous topic | Next topic »

Problems getting ZVS driver to work

first previous 2 3 4 5 next

Move Thread

LAN_403

Kiwihvguy

Wed Jan 20 2016, 09:17AM

Registered Member #3395 Joined: Thu Nov 04 2010, 08:42AM
Location: Christchurch, New Zealand
Posts: 193

Sigurthr wrote ...

Unless you're using a scope you're not going to get any meaningful measurements from a DMM, save perhaps an AC measurement across the tank capacitor. If there's continuous DC present at any gate (the kind of signal a DMM could actually measure), the driver has latched up and entered a failure state.

Sigurthr has a point here, it's quite difficult to diagnose the problem in this switching DC circuit if you don't have a scope. If you don't have one, it's not an issue but it's good to know a scope is very handy because you can see exactly how the voltage waveform looks.

1. Can you confirm you have reversed the direction of one of your primary windings?

2. In reference to the facts that this circuit is currently not functioning and that your observation with one mosfet's gate's voltage being 0.6V, this seems to suggest to that one of zener diodes has gone bad. Although you had tested them, can you confirm that you tested all 4 diodes (UF and zeners) individually, while they were disconnected from the circuit? If not, the test results will likely be false.

A lot times my ZVS circuit wouldn't oscillate because of dead zener diodes.

I just want to confirm the above 2 points before getting into in-depth technical analysis, as keeping things simple where possible is always helpful :)

GrantX

Wed Jan 20 2016, 11:14AM

Registered Member #4074 Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335

Heisenberg said that the flyback and it's primary coil worked fine with another ZVS driver. I think the ziptie on the left side is creating the illusion that the wire is exiting under the core. It looks like its just tightly wrapped and doubling back over the tie.

Antonio

Wed Jan 20 2016, 02:11PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

Try to verify if the circuit is working by replacing the primary coils by two lamps, or leds in series with resistors. Disconnect the diodes. Powering the circuit, both lamps shall light up. Connecting one diode, the opposite lamp shall turn off.

Heisenberg

Thu Jan 28 2016, 08:00PM

Registered Member #58279 Joined: Sat Jan 09 2016, 05:39AM
Location: Houston, TX
Posts: 13

I know its been a while, been super busy and took a break from working on this project out of frustration. I picked it back up again a few days ago with renewed determination as to why the heck this circuit won't work for me. I even went as far as starting completely over, brand new components, and built it back up from scratch and it still won't work. BUT...I've made some progress. I began troubleshooting at the most basic level. I was connecting the three outputs to the coil and the two inputs from the power supply using alligator wire so I thought maybe they were too thin to carry the necessary current. So I took the ZVS driver that I ordered from Amazon a while back that I know works and tried connecting that the same way I did with the driver I built...using the alligator clips and lo and behold it didn't work....interesting. I removed the alligator clips and soldered 14 gauge stranded wire directly from all three outputs to the flyback wires. I then used the same 14 gauge wire and crimped on a couple of terminal connectors and screwed them into the power supply. Now the circuit was using the same exact gauge wire as the known working ZVS driver.

I fired it up, and it still doesn't work....but this time was different. The Jacob's ladder that the flyback is connected to for a split second made a high pitched whine like it was about to arc and then silence. I measured the voltage right at the terminals on the power supply that the driver was connected to while the PSU was on and it read only 4 volts...and its a 24 volt power supply. Weird...So I disconnected the driver and just tested the terminals with the multimeter to make sure my PSU wasn't dead and it measured 24 volts without any load connected.

So, it seams it is detecting a short or something. So I connected the driver to my lab PSU that has the voltage/current adjustment knobs and a digital LCD that would give me more information about what's going on. It is a 30V 5A power supply. I powered it on and set it to 24v, max current, and connected it to the driver and turned it on. The driver was drawing over 5 amps, but there was still nothing going on. I used my infrared thermometer and measured the temps on the FETs and saw that it was rapidly climbing about 5-10 degrees a second and began smoking slightly so I shut it down.

I think I'm making progress at least, it never did any of that before so I think I'm getting close to solving this mystery. I double-checked all the solder joints and everything and didn't see any shorts. I'm using the same part values I used the last time I posted except for the FETs which are IRFP260M instead of 250...I'm not sure why there is an IRFP260N and IRFP260M, different manufacturers maybe? I checked the data sheets on both and they were identical so IDK. I am using a 1uF MKP capacitor, a 150 uH inductor, and two 18v zeners along with the UF4007 diodes. I noticed that different schematics on the net show that you can use a 12, 15, or 18v zener, can anyone tell me what different it makes to use 12v vs 18v? I have 12v zeners too, not sure if it would make a different or which one would be better.

Once again, if you guys think a photo of the new circuit would be helpful, I can definitely post one. I'm getting really close to solving this mystery that has been plaguing me for months, I could have bought like 5 ZVS drivers off of Amazon easy with the amount of money I sank into this project but you know how it is, the feeling of something that you built with your own hands coming to life is a feeling that no drug can touch.

Again, any help is very much appreciated.

hen918

Thu Jan 28 2016, 08:59PM

Registered Member #11591 Joined: Wed Mar 20 2013, 08:20PM
Location: UK
Posts: 556

yeah, SMPSs don't like Mazzilli drivers. Try putting a fairly large electrolytic capacitor on the output of your PSU. It forces the power supply to ramp the voltage, and therefore current, up slowly so it doesn't immediately limit the voltage too low for the driver to function.

Heisenberg

Thu Jan 28 2016, 09:08PM

Registered Member #58279 Joined: Sat Jan 09 2016, 05:39AM
Location: Houston, TX
Posts: 13

hen918 wrote ...

yeah, SMPSs don't like Mazzilli drivers. Try putting a fairly large electrolytic capacitor on the output of your PSU. It forces the power supply to ramp the voltage, and therefore current, up slowly so it doesn't immediately limit the voltage too low for the driver to function.

But the power supply works just fine with my other driver so this isn't the problem...

Sigurthr

Thu Jan 28 2016, 10:21PM

Registered Member #4463 Joined: Wed Apr 18 2012, 08:08AM
Location: MI's Upper Peninsula
Posts: 597

The other driver may not be reflecting back as much RF, or the peak currents could be lower (or both). Always run HV and inverter circuits from linear or magnetic supplies unless you want to add tons of low pass filtration.

Antonio

Thu Jan 28 2016, 10:26PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

Test the series indutor in the driver that works, or the series inductor of the working driver in yours. If that inductor has insufficient inductance or saturates the circuit enters a destructive mode of operation with large input current.

Heisenberg

Fri Jan 29 2016, 01:38AM

Registered Member #58279 Joined: Sat Jan 09 2016, 05:39AM
Location: Houston, TX
Posts: 13

Finally figured out the problem! I removed the 18v zeners and replaced them with 12v zeners and replaced the 150uH inductor with a 55uH inductor and it works! Since I did a couple of things at the same time, I'm not sure which one resolved the issue. Could have been a bad zener, the inductor could have been too big, or maybe the 12v vs 18v zener did it, or maybe a combination of a few different factors.

I'm glad I finally conquered this demon. I'll still play around with different amounts of capacitors and different inductors to find the best results, but at least I have a working ZVS driver at last.

Thanks to all who posted for your help and nudging me in the right direction.

jdub1581hv

Fri Jan 29 2016, 10:11AM

Registered Member #55219 Joined: Tue Jun 09 2015, 11:21PM
Location:
Posts: 80

I am betting on the Zeners... I personally run 2 on each transistor in Tvs arrangement ... The inductor doesn't seem likely.. Glad you got it going...

first previous 2 3 4 5 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob