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Solid State coil
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From: Harri Suomalainen [SMTP:haba-at-cc.hut.fi]
Sent: Monday, June 08, 1998 9:56 AM
To: leena-at-icon.fi; PICLIST-at-MITVMA.MIT.EDU; leena-at-icon.fi; tesla-at-pupman-dot-com
Subject: Re: Solid State coil
>Michael wrote:
>>inch X 6 inch box. I would like this circuit to be solid state. Does
any
>>one know how to build a high voltage 2Mhz oscillator? Ant plans would
be
>of
>>great help. Thanks to anyone who answers.<
>
>I think that a switching power supply using MOSFET's may not be feasable
>at 2Mhz - switching time / losses
Switching losses *can* be eliminated but it requires some techniques like
resonant type driver. That complicates the driver a bit more. Even the
normal
square wave driver is far more than an "oscillator" anyway.
Then there is the case with ferrites (if used). Usually some sort of
step-up
transformer is needed. Air-cored transformers are not good for such a low
frequency. Ferrites however are lossy and losses increase a lot when
frequency
rises. (Losses are roughly proportional to second power of freq.) At 2MHz
square
wave drive you would have huge losses for the 2MHz and enormous losses for
all
the harmonics (like 6MHz and 10MHz). With resonant topologies harmonics
might
be eliminated and range of roughly 1MHz or so would become feasible.
Transformer design is also more complicated at high frequency. Step-up
transformers do have leakage inductance and parasitic capasitance (not
small).
Those parasitic elements might cause resonanses where they are not wanted.
I've seen those resonate at eg. 2MHz or even much below that with a poorer
design. Sticking to the range where those do not cause problems allows you
to almost forget them.
Usually you're much better off if you go for 1-200kHz or so if you are a
biginner
with smps. You definately need a scope too.
--
Harri Suomalainen mailto:haba-at-cc.hut.fi
We have phone numbers, why'd we need IP-numbers? - a person in a bus