Circuit design help - power supply - Non FIRST

[Josh Siegel]

Hi guys (and gals),
First off, sorry that this post isn't exactly FIRST related. I posted this here, though, because people on CD know what they're talking about and are always willing to help. Plus, it may help our robot (among other things) if my theory works out.

Anyway, I need to design a power supply with dual frequency generators that can do the following, with a minimum of parts and cost:

1. Take in 12VDC at up to 30 amps (so this is a high wattage application).
2. From this, split the voltage into 6V and 6V (running in series) for use in two VARIABLE frequency sine wave generators (both use the same frequency – from about 5Hz-50Hz is what I’m looking for, though 0-150 would be great too) that are phase shifted from one another by a few degrees/radians/seconds
3. From the generators, I will rectify the outputs so that they are all positive
4. Then I will recombine the signal

What I’ve seen leads me to a few things…

First, I could use an op-amp or a wein bridge as my sine wave generator, but these do not handle high voltage or amperage well. If I could somehow get these to work without extremely expensive components (300 watt resistors and such), these would be great because the frequency is variable by a resistor, and I could share one POT between the two circuits (in parallel) so that the frequencies are the same in both circuits. The delay could simply be a variable 555 timer circuit, if my logic is correct – more time delay initially (“single fire,” if you will) means a bigger phase shift. The only thing I am unsure about is how to make sure I get full amplitude out of the circuit (6V in, the voltage oscillating from +/- 6V peak to peak rectified into +6V).

Second, I could somehow build a power inverter (DC to AC converter) and rectify the output, but I wouldn’t use a transformer and would somehow make the frequency adjustable, with a POT or similar.

Third, I could make a MAX038 or similar circuit, but my electronics skills are limited and the MAX038 has very low current/voltage limits.

The hardest part of this is making things to handle high-wattage. I hate to sound as simple as I am with electronics, but there has to be some way to use low-wattage resistors and other components in high-wattage circuits, either using the low-wattage circuit as a driver for relays or something else... Not that this is necessarily the best option; I'm just thinking out loud.

Since I'm using the output as a power supply and not to produce sound waves or anything, accuracy of the sine is not really critical as long as it is predictable. The key in this circuit would be efficiency and accuracy of the frequency, so that it makes the powered devices function as predicted.

Sorry if I'm being wordy or convoluted, I'll gladly explain as much as I can about this if it helps design the supply. I have some jpeg files of the desired output at every step, if those would help - they're on my desktop, so I can post them tomorrow.

Thanks a lot!
Josh