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Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Dr. Dark Current wrote ...
This circuit, with an additional diode in series with the input and a resistor from the PNP transistor base to ground, is very commonly used for gate driving using a GDT driven in "single ended" mode (duty<50%). The advantage is that you can drive the GDT primary using just a single transistor.
Registered Member #42796
Joined: Mon Jan 13 2014, 06:34PM
Location:
Posts: 195
i think is something like this:
The advantage come from the fact that it requires only one transistor to drive the GDT primary and it provides faster local turn OFF for the IGBT. Also i'm not entirely sure where is the best place to put the 4R7 resistor - as is shown in the picture or right after the GDT (red arrows)?
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
dexter wrote ...
.The advantage come from the fact that it requires only one transistor to drive the GDT primary and it provides faster local turn OFF for the IGBT. Also i'm not entirely sure where is the best place to put the 4R7 resistor - as is shown in the picture or right after the GDT (red arrows)?
I've studied this for a day or so, and I think the gate resistor should go on the output of the GDT. This ensures a faster turn off. The original schematic also has the PNP switch off transistor connected directly to the gate of the MOSFET.
The gate does have a 'mesh resistance'.
EDIT: Do I need to use a core with a distributed gap to deal with a DC component, or is this something that I don't need to worry about?
EDIT: I still haven't fully understood the two diodes and resistors.....
EDIT: I think I've worked it out now, there is a 'return path' for the current through the GDT secondary, through the resistors (1k and 470R), so I don't need to worry about a DC component, I think.
Registered Member #4074
Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335
Fiddy wrote ...
Some nice vids from Sigurthur on this board getting some impressive audio arcs:
That's a fantastic little driver circuit, well done guys. Are there any circuit details available online (I understand you probably don't want to release the whole schematic)? Looks like a fun kit, I'd be interested in getting one to play with.
Nothing online at the moment, since Fiddy wanted to sell these as kits I kept the development closed source. 'Tis his ball to throw as he sees fit. I might put out another revision too, but he has a decent stock of the displayed version on hand. I can say it is single ended, variable input voltage from 12-26V, with headphone level audio input - single channel mono, and low modulation distortion at the mid and upper range of the tuning band (below 30KHz you're gonna get distortion, simple physics). Future revision would include onboard stereo to mono conversion, and easy end-user modifiable frequency range adjustment for if your flyback needs higher than 90KHz.
What's funny is that I designed this circuit years ago, and literally had it sitting on a shelf covered in dust when he asked me if I knew of such a circuit or could design one, haha. There's something poetic in being too poor to produce your own designs. I'm just glad I found such a stand up fellow to take them to market for me. He even puts my name on the PCBs, haha! XD
Registered Member #8817
Joined: Mon Dec 17 2012, 05:16AM
Location: Australia
Posts: 110
GrantX wrote ...
That's a fantastic little driver circuit, well done guys. Are there any circuit details available online (I understand you probably don't want to release the whole schematic)? Looks like a fun kit, I'd be interested in getting one to play with.
Thanks dude I can sell you this driver in kit form with the board and components for $60 AUD and $10 express post being in Australia already! PM if your interested. Can supply a DC flyback too if required.
Sigurthr wrote ...
Nothing online at the moment, since Fiddy wanted to sell these as kits I kept the development closed source. 'Tis his ball to throw as he sees fit. I might put out another revision too, but he has a decent stock of the displayed version on hand. I can say it is single ended, variable input voltage from 12-26V, with headphone level audio input - single channel mono, and low modulation distortion at the mid and upper range of the tuning band (below 30KHz you're gonna get distortion, simple physics). Future revision would include onboard stereo to mono conversion, and easy end-user modifiable frequency range adjustment for if your flyback needs higher than 90KHz.
What's funny is that I designed this circuit years ago, and literally had it sitting on a shelf covered in dust when he asked me if I knew of such a circuit or could design one, haha. There's something poetic in being too poor to produce your own designs. I'm just glad I found such a stand up fellow to take them to market for me. He even puts my name on the PCBs, haha! XD
Hehe yeah, we did a lot of design work before the boards was even manufactured I had 10 boards made.
Hats off to Sig who has the brains to design the circuit, disregarding the LED resistors, theres only 1 resistor on the board in the circuit! Amazing
Registered Member #4074
Joined: Mon Aug 29 2011, 06:58AM
Location: Australia
Posts: 335
Fiddy wrote ...
Thanks dude I can sell you this driver in kit form with the board and components for $60 AUD and $10 express post being in Australia already! PM if your interested. Can supply a DC flyback too if required.
So! I've finally had some time to get around to my long list of things to do, and I whipped up another one of my driver circuits to show off Fiddy's transformer and driver.
One of my home made electrodeless tubes; ~55Torr air.
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Driving 'Fiddy's Flybacks' in flyback mode.
I can sell you this driver in kit form with the board and components for $60 AUD and $10 express post being in Australia already! PM if your interested. Can supply a DC flyback too if required.
