Improved single transistor flyback driver / High Voltage / Forums

Forums

4hv.org :: Forums :: High Voltage

« Previous topic | Next topic »

Improved single transistor flyback driver

first previous 3 4 5 6 next last

Move Thread

LAN_403

Mads Barnkob

Fri May 02 2008, 04:40PM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

I just tried out this circuit with components harvested from the same CRT as the flyback transformer but its not working as intended, unless I wanted something cooked.

12 V PC PSU / 14A

I used 4400uF / 25V, 500R, 27R, E13009L transistor, EGP30D diode 200V and a 0.27uF capacitor. I used 7T and 4T on the windings.

When powering it up after a few seconds the transistor is so hot that the wire on the collector will disconnect due to the heat melting the solder. Dont know if its dead, but it can repeat this torture.

Dr. Dark Current

Fri May 02 2008, 04:48PM

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

MadsKaizer wrote ...

I just tried out this circuit with components harvested from the same CRT as the flyback transformer but its not working as intended, unless I wanted something cooked.

12 V PC PSU / 14A

I used 4400uF / 25V, 500R, 27R, E13009L transistor, EGP30D diode 200V and a 0.27uF capacitor. I used 7T and 4T on the windings.

When powering it up after a few seconds the transistor is so hot that the wire on the collector will disconnect due to the heat melting the solder. Dont know if its dead, but it can repeat this torture.

1) try to reverse polarity of one of the windindings (feedback OR primary). If nothing happens, now reverse polarity of BOTH primary and feedback.
2) some transistor with Vce of >250V do not work well
3) maybe your transistor is cooked

Mads Barnkob

Fri May 02 2008, 05:56PM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

Plasmaddict wrote ...

first try: Reversing the polarity of the feedback worked, now I can draw some arcs, but I get a shortcircuit that suddenly jumps between ABL and +40V on the flyback. Also changed to a 2n3055 which gets too hot to run for more than 30seconds.

second try: tried with old transistor again, the E13009L but once again it overheats and melts the solder.

third try: wire on chickenstick was connected to +40V instead of ABL, no more shortcircuting between those two pins and it can now draw a nice hot arc starting at 10mm and can be drawn up to about 20mm.

nice circuit and thanks for the help :)

edit: fourth try: gave it 17V and it could draw arcs about 2-4 mm further away than before, but 2n3055 heats up very fast and it can only run for a few seconds before i chicken out and turn it off.

Dr. Dark Current

Fri May 02 2008, 06:27PM

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

MadsKaizer wrote ...

edit: fourth try: gave it 17V and it could draw arcs about 2-4 mm further away than before, but 2n3055 heats up very fast and it can only run for a few seconds before i chicken out and turn it off.

glad you got it working, I was getting some 5cm arks and the transistor was not too hot on a big heatsink after a minute. Maybe you can try to tune it better (220-680nf high quality cap works best), and wind the windings tightly on top of each other (insulate with some tape). Do you have rectified or unrectified transformer? Do you have some gap in the core?

Mads Barnkob

Fri May 02 2008, 06:59PM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

Plasmaddict wrote ...

Ive installed the transistor on a piece of siemens plc rail now, so it got a huge 30cm long heatsink, it can drive for minutes without even being luke warm.

Its a real messy birdnest circuit I made just to try it out, when I put it on some board ill try to tune it with different caps.

There is not much space around the core of the transformer, its a fairly new one from a computer crt, so they are wound above each other, the core aint broken if thats what you mean, else its gaps 1-1.5 mm from its housing where i have the windings placed. I guess its a rectified transformer, since its new and the output arcs are very smooth and silent compared to my ignition coil.

Dr. Dark Current

Fri May 02 2008, 07:03PM

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

MadsKaizer wrote ...

I guess its a rectified transformer, since its new and the output arcs are very smooth and silent compared to my ignition coil.

With rectified transformers try to change polarity of both primary and feedback coils, it will either work better or worse. This is because the HV output pulse is much bigger in one polarity and the diode will either block it or pass it depending on polarity.

Mads Barnkob

Fri May 02 2008, 07:22PM

Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968

Plasmaddict wrote ...

MadsKaizer wrote ...

I guess its a rectified transformer, since its new and the output arcs are very smooth and silent compared to my ignition coil.

I will look into your surgestions tomorrow, got some other stuff that needs my attention for the rest of the day. I will write down the different settings with some pictures for comparison.

dingo27

Mon May 12 2008, 09:50PM

Registered Member #890 Joined: Tue Jul 10 2007, 10:06PM
Location: Slovakia
Posts: 180

i managed to do my own HV transformer (bit nerdy... but works :) ) it gives 3-4mm sparks and one end of secondary gets really hot - red hot. i must try that with capacitor and diode, as it will be powering my yet smaller TC i am building tomorrow...

btw. i post photos as soon as i get suitable batteries, because that rechargeable i am using are crap.

but if you want to imagine, it is 15mm diameter x 2 cm width , and shape is " H " ... it works quite good for that little thing :)

Firefox

Tue May 13 2008, 01:02AM

Registered Member #1389 Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346

This is a wonderful little circuit, and I was wondering, how far could I push it with the right components? My transistor is rated 600V 7A, diode is a 250V 8A rectifier, my cap is 250VAC, my smoothing cap is 300V 600uF, and my resistors are a string and a bank of 5 5W resistors each. Could I theoretically put rectified wall voltage into it? Its already drawing ~6-8mm arcs on a 12V 6A rail of a computer PSU.

Dr. Dark Current

Tue May 13 2008, 07:08AM

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

Firefox wrote ...

Could I theoretically put rectified wall voltage into it? Its already drawing ~6-8mm arcs on a 12V 6A rail of a computer PSU.

No, no! The transistor voltage should be generally at least 6x your supply voltage (a rule of thumb, some transistors can take more abuse than others), so for rectified mains you would need at least 1200V transistor (if you are on 120V) or a 2000V one /if you are one 230V- I've never seen a commonly available transistor of this rating).
For operating at higher voltages it is also advised to increase number of primary turns and possibly the value of the "upper" resistor (maybe too decrease the value of the capacitor and increase its voltage rating).

first previous 3 4 5 6 next last

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