Raivope's POC replication attempt

  • Last Post 26 November 2020
raivope posted this 22 November 2020


I really wanted to keep it simple. LOL!

Here is a standard POC setup - in my case 14-turn primary and two POC opposing coils (0.8mm wire, ca 180 turns). Maybe @Chris will correct me if I have to modify the turns value.

I created double-rail circuit that has special mosfet driver sync switching. Kept power supply low 3V and noticed the collapsing EMF (CEMF) to fry the mosfet. Upgraded CEMF bypass diodes to 1200V SiC shottky diodes - now better.

Then played with different PW and frequencies - found that the lower mosfet Q2 was a bit out of sync and still got CEMF fry at 110V level (debugged with oscilloscope).



Sorry about the picture quality, noticed later in computer that it did not come out well. Using AMCC core.


  • mosfets turn off very fast, mosfet driver has 10ohm resistor, primary has 14 turns, all together creates high voltage spike - mmm... I think I know where part of the problem is - my 220uF electrolytic cap is too slow to capture it
  • I really wonder how you guys manage with a single mosfet!? Either slow gate turnoff or high voltage mosfet to keep spike low.
  • oscilloscope is essential to debug mosfet driving and collector peaks



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Chris posted this 22 November 2020

Hey Raivo,

Excellent Work! Thank You for Sharing!

If I may suggest, while at this stage, please keep the Mosfet Switching High Side, if you follow the thread: The Input Coil, and look for the Waveform: Here

At least while learning. Makes for easier steps forward.

The Sawtooth Waveform is important, some over look this and do not study its importance! I recommend In depth Study in this area! Do you have an Oscilloscope? Sounds like you do, check for The Sawtooth Waveform, pay special Attention here.

Great Work! Thank You for Sharing! It is great to see others Progressing!

Best Wishes,


Vidura posted this 22 November 2020

Hey Raivo, In a pulsed transformer the BEMF appears in all coils of a common core when the switch turns off, and normally if we want to trigger the POC with a magnetic pulse we should not recycle the BEMF to the source, but instead allow to be transferred to the POC and bring their voltage up. Therefore a single low side switch, without diode in the primary might be a better choice. For the protection of the switch a MOV can be used with a clamp voltage below the max rating of the MOSFET. Also check the diode polarity referenced the dot marks of the POC. Regards Vidura.

raivope posted this 23 November 2020


I thought I give you guys a quick update. Took some advice and tested with a single mosfet.

Found my mini retro mosfet driver (similar circuit as quadratron) and connected it to 800V fast mosfet.

Power supply was at 3V, 12khz PW=10% where BEMF peak exceed 650V and lasted about 50ns. Mosfet runs cool, because its rating is 800V.

While zooming out - we can see 1200khz reflection

It was interesting, when I lowered frequency - at some point below 5khz this peak started to descent. I explain it so that the POC coils have its own frequency and it when it fluctuates, it creates changing impedance, and it affects the BEMF.

So - what about the current?

Did not get much current flowing yet from 3V input (tested from 100hz up, actually, the driver can run up to a few megahertz) - I had oscilloscope current clamp connected and it showed current fluctuation, but it had very short duration. In a week or two - will update component stock and will build a dedicated current shunt.

So - my advice to the beginners is to use at least 600-800V mosfet to avoid BEMF destruction.


raivope posted this 23 November 2020

I want to Stress about The Sawtooth Waveform. In the Thread: Some Coils Buck and some Coils DONT, I gave the different Waveforms and how each Waveform was different depending on how we Wound, and Connected our Coils.

What waveforms, voltage or measured from shunt, did you mean current?

The second Waveform is very much more Linear that the first Waveform. - This is really important and we want to see this Linear and not the Exponential Curve. /../

same here

Figure 4. - the same.

We have read this over and over again, it is obvious for the smart mind, but my transient memory cannot handle over one thing, have to scroll back to find out what was actually meant. Chris - just a word or two are missing, can you reedit the post, and every time you write waveform expand it: a la "current waveform must be sawtooth".

Thanks for the help!


PS! I basically understand the road. Have to find the sawtooth wave that indicates the coils are talking and generating. My coils are wound by hand and are a bit different. Will fix coils if they refuse talking. I guess then there are no limits! I see in my mind a number of different ways to pulse coils.

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Chris posted this 23 November 2020

Hey Raivo,

Voltage and Current will follow each other, so both the Voltage and the Current Waveform will have a Sawtooth Waveform! You will see when doing further experiments.

Experiment is the path forward, this will give you more insight! Follow what I shared in my video and remember, this is just the start!

Best Wishes,



P.S: I have moved the post to the thread: The Sawtooth Waveform.

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raivope posted this 26 November 2020


After building my new shunt as promised, I can provide you clean picture.

The same standard POC setup:

Here I have a clean gate signal (18V, 2kHz) and current measured from lightbulb circuit (37mA).

Played from 3 to 10V - mosfet went hot, lightbulp did not start.

I know, Chris likes triangles, but still to go... (triangle must continue after the activation pulse) 

(I hate my coils so in time will build better and more symmetric coils, and later will use more expensive mosfet)

Best wishes,



Chris posted this 26 November 2020

Hello Jcil.nl,

I agree! Stop Posting Jcil.nl! Until you have something of VALUE To Share!

Your posts are really just spam and non-sense! I will Ban and Delete your Posts if you continue!

You have been put on Moderation until further notice!

Best Wishes,


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