Switch-mode supply for bug zapper (fwd)

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---------- Forwarded message ----------
Date: Wed, 22 Sep 2004 12:18:49 +0930
From: Matthew Smith <matt@xxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Switch-mode supply for bug zapper

Hi All

Unsatisfied by the performance of our bug zapper (UV tube, HV applied across a 
grid - flies crawl in, then crawl out again without shorting anything), I am 
looking at alternative designs.

The one we have uses a conventional laminated iron, 50Hz transformer.  The whole 
thing gets warmer than I'd like, so I'm looking at making a switchmode version.

My idea is to use a flyback topology (only two windings to wind) with an 
integrated switcher (TOP202), which runs at 100kHz.  This will drive a 1:10 
transformer, which will be rectified and charge a small capacitor.

1) What do I need to know and what formula would I use to calculate my primary 
turns?

2) Ditto for sizing the components for the snubber.

I assume that a microwave oven diode - normally working at 50-60Hz - would be 
too slow for the HV rectification and that I'd need a string of high-speed diodes.

Cheers

M


-- 
Matthew Smith
Kadina Business Consultancy
South Australia