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Can I drive a LOPT (flyback) With this ?

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ZakWolf

Wed Oct 14 2015, 05:15AM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

I have a working version and have been doing some googling for another project im working on. I have never powered a flyback with a half-bridge set up. How many primary turns on flyback would i be looking at ? Probably have to disable the interrupter and run it in CW mode(120v wall power, i do not own a variac).

Lastly I was reading not to long ago someone built a staccato interrupter fr this tesla coil and the sword sparks were amazing anyone have a link ?

GrantX

Wed Oct 14 2015, 06:48AM

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

The half bridge will work fine, but you will need to modify the circuit. The antenna picks up the oscillations from the resonator and feeds the signal into the input of the GDT driver ICs. You don't want to drive a flyback at its resonant frequency, since the voltage rise across the open-circuit secondary will nuke the insulation (plus you would need a ferrite CT over the ground lead from the secondary anyway, an antenna isn't really suitable for a ferrite-core transformer).

You will want to remove the antenna and 74HC14 IC, and replace the whole mess with some kind of local oscillator. The oscillator will provide a "clock signal" to the input of the driver ICs and will be responsible for controlling the frequency of the half-bridge inverter. The best frequency will vary depending on the transformer, so it's usually good to be able to adjust the frequency with a pot. One important thing is that the oscillator should be operating at a 50% duty cycle, in order to avoid saturating the GDT. Something like the SG3525 could be suitable, but there's probably far better choices out there (I can't remember if it's capable of an exact 50% duty cycle).

You can disable the interrupter if you wanted a smooth silent arc, but it should function perfectly if you wanted to play around with spark effects or creating a loud tone. You can set up the interrupter to provide a variable duty cycle output, and that will allow you to have some control over the RMS input power without the need for a variac (however, peak voltage will be roughly the same).

TwirlyWhirly555

Wed Oct 14 2015, 09:09AM

Registered Member #4104 Joined: Fri Sept 23 2011, 06:54PM
Location: Uk .
Posts: 122

I used a LTC1799CS5 to drive a full bridge for flybacks , its a fully contained 5V ossilator with a rail to rail 50% duty output from 1Khz - 33Mhz with a single resistor to set the frequency and 1 pin to set internal divider .

I did try FM modulation too by coupling a audio signal to the oscillators set pin , it worked not to badly

GrantX

Thu Oct 15 2015, 04:09PM

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

TwirlyWhirly555 wrote ...

I used a LTC1799CS5 to drive a full bridge for flybacks , its a fully contained 5V ossilator with a rail to rail 50% duty output from 1Khz - 33Mhz with a single resistor to set the frequency and 1 pin to set internal divider .

I did try FM modulation too by coupling a audio signal to the oscillators set pin , it worked not to badly

That looks like a very good option, it's wide frequency band is nice.

It'd be great to have a list of common IC's that are useful for 4HV-related circuits, such as Tesla coils, induction heaters, etc etc. Things like oscillators, PWM IC's, FET drivers and other SMPS-related items might be a good starting point.

TwirlyWhirly555

Fri Oct 16 2015, 11:37AM

Registered Member #4104 Joined: Fri Sept 23 2011, 06:54PM
Location: Uk .
Posts: 122

For fixed based stuff like fly backs or similar its very good considering most stuff like that is below 100Khz , I came across it while looking for VCO ICs .

That would be handy , there are a lot if ICs out there .

Here's the IC

IMG_1101[1] by TwirlyWhirly555, on Flickr

Its directly soldered to copper clad , etch pen was used to draw the circuit , its Opto coupled the the gate driver side

IMG_1097[1] by TwirlyWhirly555, on Flickr

ZakWolf

Sat Oct 17 2015, 07:20PM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

GrantX wrote ...

The half bridge will work fine, but you will need to modify the circuit. The antenna picks up the oscillations from the resonator and feeds the signal into the input of the GDT driver ICs. You don't want to drive a flyback at its resonant frequency, since the voltage rise across the open-circuit secondary will nuke the insulation (plus you would need a ferrite CT over the ground lead from the secondary anyway, an antenna isn't really suitable for a ferrite-core transformer).

You will want to remove the antenna and 74HC14 IC, and replace the whole mess with some kind of local oscillator. The oscillator will provide a "clock signal" to the input of the driver ICs and will be responsible for controlling the frequency of the half-bridge inverter. The best frequency will vary depending on the transformer, so it's usually good to be able to adjust the frequency with a pot. One important thing is that the oscillator should be operating at a 50% duty cycle, in order to avoid saturating the GDT. Something like the SG3525 could be suitable, but there's probably far better choices out there (I can't remember if it's capable of an exact 50% duty cycle).

You can disable the interrupter if you wanted a smooth silent arc, but it should function perfectly if you wanted to play around with spark effects or creating a loud tone. You can set up the interrupter to provide a variable duty cycle output, and that will allow you to have some control over the RMS input power without the need for a variac (however, peak voltage will be roughly the same).

Since Im bouncing around with a couple projects I was looking at repairing my Plasma Speaker (Adam

and getting my sstc 5 mini running again.

Can I drive the sstc mini UCC's pin 3 directly with the output of the sg355 from the plasma speaker?

Would audio mod. still work?

Could I audio modulate the tesla coil or if I used the sstc mini H bringe for a flyback could I run it of the line voltage(120v)?

GrantX

Wed Oct 21 2015, 11:39AM

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

Pin 3 on the UCC driver ICs is the enable pin, its used to hold the IC in a on or off state (that's why its used for the interrupter in that design). Pin 2 is the input, and it should work fine with the signal from a SG3525. Unless I'm missing something, the audio input to the SG3525 should also work (for the flyback only, unless you have tuned the SG3525 to the same frequency as your coil, like an open-loop SSTC).

The bridge is already running off a 120V line, so that will also work for your flyback, just make sure you have enough turns on the primary!

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