[Prev][Next][Index][Thread]
Solid state design
Nick
It's not that easy unfortunately.
You've got a few additional problems for your application
small coils won't be spectacular. They emit a lot of RF interference
which will be picked up by the audio system. Ozone is produced by
the output sparks as well. And how do you ensure that there will never
be someone with a pacemaker in the audience.
I'm also experimenting with a primary rather than output
transformer approach it looks promising. And as you say output
transformers are a pain.
3524 works at 150kHz max (200kHz at a push)
At 400kHz you will have big switching losses.
3825 works to 1mHz. Its the chip I'm using but there must be a better
chip out there!
MC34151 I'm not familiar with but check that they switch fast enough.
For a half bridge you should be using a low side and a high side driver.
Or a driver transformer (not hard to make).
I'll bring my half bridge to the teslathon.
I would strongly recommend an isolating transformer and a variac
(I got a 500W toriodal from J&N factors for £25)
You're on the right lines.
Alan Sharp.
Message text written by INTERNET:tesla-at-pupman-dot-com
>Hi All,
After some thought I decided to avoid an output transformer because the
many
hours needed to make one didn't really seem all that exciting. When you
actually calculate the impeadance of a 12µH inductor (typical helical pri)
at
400kHz it is actually quite high, about 30ohms. So if I use a 300V
H-bridge
drive (IRF3415 FETs) I can put 10A throught it, well within the capability
of
the fets and a nice round 3kW power input. I am using the SG3524 pwm chip
buffered by MC34151 and MC34152 drivers, inverting and non-inverting
respectively. A question for all you smpsu designers is how safe is it to
just rectify 240V mains and run this off that? Should I use an iso
transformer? I also wondered if anyone had any ideas on my choice of pwm
chip (does the 3524 run at 400kHz? - Is any of this really stupid?
Thanks in advance
Nick Field
<