Boost Converter Troubleshooting

[Marc124]

Hello,

I am currently working as a team on a project with our university, we have chosen to use a 3-6V - 400kV boost converter as part of the project. None of use have much knowledge on them and we're trying to troubleshoot why the two we have tried to use haven't worked.

Our circuit its just the positive and the negative soldered to the respective pads of a battery holder with a push button in the middle of the negative wire, the supply we are using is rated at 5V (we have also tried 3V and 9V since).

All our connections are mechanically sound but we only seem to be getting a maximum of 60V from the higher voltage side.

Sorry if its something really simple just a bit lost on where to move with this and we have other things we need to finish so any advice would be greatly appreciated.

 

[sagor1]

400kV !!!
Best to post what converter you are using or at least a schematic of it....

 

[Marc124]

Its just one like this if that helps at all. Not really sure what we're using it for to be honest but the other people in the group have it in a list of things we need to prepare.

 

[sagor1]

I have my doubts that is a 400kV booster. It would arc across the output posts most likely with that picture.
Back to basics, what does the converter specifications say? What is the input voltage and current requirements? Without knowing if the input is correct, one cannot guess if the output is working properly or not.

EDIT: A spark gap of 1cm needs about 30,000V. A 400kV generator would spark across 13cm, way more that the spacing of the output contacts.
Also, to produce even 1mA of current at 30,000V, you would need 1A at 30V, or 10A at 3V. Your input supply has to be able to supply high current.

 

[Marc124]

Thanks for your replies.

I'll try and fetch some more information from the people who sourced it and all that.
At the moment I believe they're leaving around 1cm - 2cm gap and I didn't know if that was too distanced and it'd burned out some internal components but not sure whether that would explain low voltage and not just be a case of no voltage out of the higher end.

the power supply at the moment is mainly just standard UK batteries but I don't know exactly what they're using, they seemed pretty confident that they were using correctly rated things.

 

[rjenkinsgb]

Those modules are not "Boost converters", or at least not in the normal sense; I believe they are gas ignition modules.

They have two stage circuits - a boost converter up to a few hundred volts, then a capacitor discharge circuit that produces the extremely high voltage as repeating AC bursts, each time the capacitor fires through the output transformer.

The ones I have appear to be intended for 1.5V or 3V; they actually work fine at that and when used with a single 1.5V, produce the fast repeat "tick" sparks just the same as many gas hobs etc.

Despite any resellers claims, running them at much above that can probably damage them over time, depending on component tolerances. They get hot quite quickly at 4V, again implying they are intended for short bursts rather than continuous operation.

The maximum spark I can get from them is near 20mm at 3-4V input.

At that voltage and frequency, just about any PCB will cause leakage and may kill the output. Even the shape of the spark terminals matters - points give a rather smaller maximum than folded over(rounded) ends.

I did a video demonstrating one of these at different voltages, but I've not got around to processing it and putting it on my youtube channel yet - I'll see if I can do that today.

 

[rjenkinsgb]

Now I remember why I did not post the video originally - the audio is abysmal, as the noise from the sparks shuts down the camera AGC!

I've put it on anyway; looking through it, 20mm is just achievable , at least with my module, using 4V from a lithium cell.

 

[Marc124]

That video was perfect, thanks for that.
Pretty sure they've either burned it out or are just using an unsuitable power supply as they were trying to run it at 5V as was mentioned when they bought it apparently and I couldn't hear the inverter going at all and there were no sparks when they tested it.

Going to try and figure out whats going on with it today but thanks for the help with this and thanks for the video that cleared everything up for me.