The Flashy-Light Circuit Challenge

Ok, bright children, design this:

An inverter circuit which generates high-voltage AC (200 volts) at a frequency that varies continuously from 60 Hz to 1500 Hz.

Let me be more specific. The frequency generator should be a standard 555 timer chip, rigged in astable mode to produce a square wave on a 9-volt signal line. (See, even I can figure out how to do that. All hail Forrest Mims the Third.)

Your job is to take that output (9V signal and ground) and turn it into a 200-volt alternating current.

[Input wave]   [Output wave]

I've drawn the output as a square wave, but it doesn't have to be exact. Anything with the right primary frequency will do.

I assume a transformer will be involved. I'm told the naive setup (attaching the transformer directly to the 555) is a bad idea, because when you switch it off, the collapsing magnetic field will spike current back through the 555 and fry it. Is this true? If so, deal with it.


(Email to me, posted here with the writer's permission)

Last updated December 4, 2000.

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