High Voltage Diodes... / High Voltage / Forums

Forums

4hv.org :: Forums :: High Voltage

« Previous topic | Next topic »

High Voltage Diodes...

1 2 next

Move Thread

LAN_403

Matt Edwards

Sat May 01 2010, 02:00AM

Registered Member #2838 Joined: Fri Apr 30 2010, 07:55PM
Location: tehachapi, CA
Posts: 333

Could someone recommend a good rectifier diode for the output of a zvs flyback driver??? I am using the revised mazilli circuit with 48v input and IRFP460's instead of 250's. I have had a lot of trouble determining what the best choice is... I intend to use this driver for a small tesla coil. Hopefully...

hboy007

Sat May 01 2010, 10:09AM

Registered Member #1667 Joined: Sat Aug 30 2008, 09:57PM
Location:
Posts: 373

If you could tell us what your estimated peak and RMS output voltage will be, we might be able to help you. Do you need rectifier diodes for the output of your transfomer or freewheeling diodes? What needed current rating do you estimate?

Edit: I saw on the other thread that you use HFA15TB60PBF as clamping / freewheeling diodes. So what is your estimated output voltage/current? Your idle frequency is at about 8 kHz?

Antonio

Sat May 01 2010, 05:33PM

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

Why don't you use a flyback transformer with a built-in rectifier? Most of them have the diode already.

Matt Edwards

Sat May 01 2010, 09:56PM

Registered Member #2838 Joined: Fri Apr 30 2010, 07:55PM
Location: tehachapi, CA
Posts: 333

I am sorry but I should have elaborated a bit more... Unfortunately I do not have any HV equipment to test the output of the flyback nor do i have any information "about" the flyback because it was given to me. I am pretty sure that it is not internally rectified but I could be mistaken. It is a pretty old flyback from about 1980 or so...
I am looking for a rectifier diode for the High voltage output of the flyback. The circuit that I was modeling this after used a Rectifier diode after the high voltage out and then a capacitor bank connected parallel between the HV out and the 0v on the flyback. The HV out end of the cap was then connected to a spark gap, then the top of the primary on the tesla. The 0v end of the cap was connected to the bottom of the primary on the tesla.

I apologize for the crude drawing!

F/B HV out ------(diode)------------------------------------- ------------------|>Spark Gap<|--------(Primary coil of tesla)

|
_____
_____

|

F/B 0v------------------------------------------------ -------------------------------------------------- -(Primary coil of tesla)

MRacerxdl

Sun May 02 2010, 12:46AM

Registered Member #989 Joined: Sat Sept 08 2007, 02:15AM
Location: SÃ£o Paulo, Brazil
Posts: 476

If the flyback doesnt have internal diode, you can make one with series string of ultrafast diodes, but have in mind, that you will also need how much is the output that you will have. UF4004 is 1000V 1A Ultrafast diode.

Proud Mary

Sun May 02 2010, 12:20PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Oidium45 wrote ...

It is a pretty old flyback from about 1980 or so...

By 1980, 'diode split' 'LOPT's ('flybacks') had almost completely replaced the type with external rectifier/tripler in new TV design.

With the diode split LOPT, the secondary is split into several sections interconnected by HV diodes, so the output from the unit is both tripled and rectified. For all practical purposes, the internal diodes of the split secondary type cannot be removed, though one hears of young desperados trying to overload them in the hope that the diodes will fail and fuse in such a way as to close the circuit.

My advice: find something interesting to do with 25kV DC.

Matt Edwards

Sun May 02 2010, 05:47PM

Registered Member #2838 Joined: Fri Apr 30 2010, 07:55PM
Location: tehachapi, CA
Posts: 333

Thank you everyone for the feedback! Proud Mary, your explanation might account for the fact that I have several HV out wires to choose from??? A few seem to produce more current/less voltage, while others produce more voltage/less current. With the IRFP250's at 24v I am getting varying results between yellow/orange-white/blue-blue/purple depending upon wire configuration. When I connected the circuit containing the 250's to a 48v supply I was getting a bright white (varying in length depending upon wire configuration). Unfortunately it did not last long before I shorted one of the fets.
When I connected the circuit containing the IRFP460's to a 48v supply all wire configurations produced bright blue arcs varying in length depending upon wire configuration. I have not been able to try the 460's on a lesser voltage supply.

My goal was to use this supply to power a vary small tesla coil and perhaps a small lifter... As fun as it is watching big sparks for a while is, it was not where I was hoping to leave off with this project...

Proud Mary

Sun May 02 2010, 06:03PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

The three wires coming out of the LOPT are the high voltage output - usually red with thick insulation - and the screen and focus outputs, which you should leave floating, not connected to anything, and ignore. They do have quite high voltages on them, so tape over the ends, so they don't short out on something, including yourself.

radhoo

Mon May 03 2010, 11:15AM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 699

I've built a small ZVS/Flyback based Tesla coil but it only offers small sparks and a lot of noise

Matt Edwards

Wed May 05 2010, 05:20AM

Registered Member #2838 Joined: Fri Apr 30 2010, 07:55PM
Location: tehachapi, CA
Posts: 333

I was actually hoping for something like this...

1 2 next

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