Re: Flyback Transformer
Posted by Josh on 1/21/2010, 2:38 pm, in reply to "Re: Flyback Transformer "
: --Previous Message--
: Hey Bert,
: My goal is to have a SSTC to act as a plasma speaker. Based on your reply
: and additional research into the flyback design, I found that it will give
: me a better audio sample and the design is somewhat easier than the
: air-core transformer design but I feel as though I am cheating myself and
: I am not getting the full Tesla Coil design experience. I am in the
: process of switching my design to using an air-core transformer using a
: sphere top load. What supply voltage do I need in order to operate the
: coil? I have seen many sites that use a 12Vdc supply to power their SSTCs
: while others use high voltage transformers (NST in particular). I am
: looking to produce sparks of 30cm and I feel that using a 12Vdc supply
: will not give me enough power to achieve this.
: Hi Josh,
: Most solid state coils operate from relatively low DC supply voltages -
: from tens to to hundreds of volts. A few special systems use costly high
: voltage power transistors (such as Greg Leyh's new solid state coils).
: These may operate with DC supply voltages as high as 1-3 kV.
: All Tesla Coils using NST's either use spark gap switching or a newer
: solid state "equivalent" using a stack of Sidac IGBT Spark Gap
: (SISG) solid state switching modules. (Look up SISG in the Pupman archives
: at www.pupman.com for more information). NST-powered coils are not easily
: modulated for audio.
: Tesla Coil spark length is a function of design/construction efficiency
: and input power. A well-designed Tesla Coil can easily deliver at least 30
: cm (~12" sparks with an input power of 90 watts. The input power
: could be supplied by a 12V power supply capable of supplying 7.5A, or a 90
: volt supply delivering 1A... either will work as long as the SSTC circuit
: is designed to work at the desired voltage.
: If your focus is to make a coil that you can use to drive a relatively
: high fidelity plasma "speaker", and if you don't have much prior
: electronics design experience, you may want to check out the Plasmasonic
: Tesla Coils and kits from Dan McCauley at Eastern Voltage Research. The
: best audio fidelity tends to occur with coils operating at high frequency
: (1 MHz+) and short output sparks (actually more like an almost silent
: flame-like corona) that's only 1/2" - 2" long. This severely
: limits low frequency performance. Systems that generate longer sparks
: often use DRSSTC's or higher power SSTC's. While you can get much louder
: sound from these larger systems, they tend to have poorer audio fidelity
: due to spark-generated artifacts (hissing, crackling). Also, audio
: modulated DRSSTC's are limited to hundreds of Hz to a few kHz by the
: nature of their operation.
: For some ideas for both types of systems, see Dan's site:
: Good luck,
I have started designing the transformer for my Tesla coil, and I just wanted to run some things by you before I start construction. I am going for a DRSSTC, so I started designing my secondary in which I found the resonant frequency and then I tuned the primary accordingly.
Diameter of secondary - 5inches
# of turns - 950
wire diameter - 0.0126inches (28AWG)
L(Using the inductance formula for a Helical Coil) = 21.382mH
self capacitance of coil - 9.47pF
Capacitance of topload (sphere) - 27.8pF
Resonant Frequency - 178.285kHz
Inner diameter - 8inches
# turns - 5
wire diameter - 0.25 inches
spacing - 0.25 inches
L(using the inductance formula for Flat Spiral Coil) - 9.92uH
C(based on resonant frequency and inductance of primary) - 80nF
*The schematic of the XFMR is shown here [img][/img]
I have the following gain vs freq and impedance vs freq plots shown below
I am having problems simulating what the output voltage and current as well as the input current. I have looked around the web for some way to calculate these values but cannot find a clear cut way.
Also, I am going to have two sets of switching MOSFETS connected in a half bridge configuration at the input to the primary but I am wondering at which voltage should I be pulsing at?
Thanks again for all your help,