Re: Egg Circuit Revisited - A Solid State Driver

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Original poster: Ed Phillips <evp@xxxxxxxxxxx>

I would like to find a better way to create the additional phase. I have
looked at various triac and scr circuits as well as plans for DC to AC
inverters. The inverter circuits are closer to what I need but I already
have 120VAC so I need to work directly with it rather than create a power
supply to drop to 12VDC and then back to 120VAC using another transformer.
Most of the circuits use a center tapped transformer to combine the two half
waves together and boost the voltage to 120V. This is not useful.

The only circuit that seems promising is this:
http://www.interq.or.jp/japan/se-inoue/e_ckt30_1.htm

He is using 2 pairs of MOSFETs in sort of a push-pull arrangement to create
both positive and negative cycles in the same circuit. If I can find
replacement MOSFETs capable of handling 120VDC directly, I should be able to
double the circuit and invert the gates on the second set of MOSFETs which
should mimic two phase AC. Of course this will be a square wave output, but
I don't think the egg will mind.

Please let me know what you all think about this and if there may be a
better way (short of using 2 phase directly of course).

Thanks,
Cameron"

   Should be no problem finding suitable 
MOSFETSof almost any voltage and power rating at 
very reasonable prices.  Look up the IRC HEXFET's in Mouser or Digikey.  As for

"double the circuit and invert the gates on the second set of MOSFETs which
should mimic two phase AC. Of course this will be a square wave output, but
I don't think the egg will mind."

not sure what you mean.  The two signals need to 
be 90° out of phase, not 180°.  I'm not a logic 
circuit designer but should be easy to start with 
a 120 Hz square wave source and combine the 
outputs to get the desired square wave drive signals.

Ed