Hey, all, I thought this would be easy but it's not been so far. What I want to do is take a DC power supply and output an AC voltage. The power supply I'm using puts out 6 volts DC and is marked that it can handle 1.66 amps output. All I want to do is take that and turn it into square-wave AC; not sinusoidal AC, but strictly square-wave AC and at the same 6 volts as the input. The mechanism needs to be able to handle the maximum of 1.66 amps and the 6 volts. The load is NOT inductive and, to the best of my knowledge is NOT capacitive; I believe the load is STRICTLY resistive. Many Bothans died to bring us this information. :)
What I've done is search for: buck converters, buck-boost converters, dc ac converters, dc ac inverters, dc chopper, dc square wave ac, and similar but most of what I find falls under either some patent site, or dc to ac inverters for taking 12 volts dc and making 120 volts ac sine-wave for driving appliances, or taking dc voltage up or down to DC.
All I want is to take my DC source and alternate the polarity like AC but I want it to be square-wave and I'd like to be able to vary the frequency. The oscillator like I'm using now (555-based) should handle the frequency variations (but I'm always open to suggestions, of course, or I wouldn't be posting here); what I'm hoping for is a "chopper" circuit to turn this output into square-wave AC.
What I've done is create an oscillating circuit using a 555 timer and a pot that allows me to vary the frequency of output from about 160 Hz to about 10.86 kHz at roughly 50% duty cycle. What I would like to do is use that to drive a circuit that can alternate the polarity of my DC power supply at the same frequency. It would seem that I need a MOSFET to control the power (several, in fact). I have used this timer circuit to drive a MOSFET (a BUZ11) and it works; I get variable frequency, pulsed DC power. That is, use the 555 output to drive the gate of the BUZ11, the power supply positive at the Drain, the power supply negative at the Source, and what I get is pulsed DC. But what I want, again, is square-wave AC.
I have found that in DC motor control (particularly for robotics) people use H-Bridge's to control electric motor direction which would seem to do what I need to have done; the schematics I've seen use 4 MOSFETs (two P channel, two N channel) to apply source voltage in one polarity or another. I could use the output of the 555 timer (or another oscillator) with an inverter of some kind (I'm NOT an expert at this stuff by any means, so some technicality will be lacking in anything I say but I try to be accurate) to take the output and make one MOSFET gate low (N channel) and one MOSFET gate high (P channel) when one polarity is required and reverse it for the other.
That leaves me using one 555 timer to control oscillations, 4 MOSFETs to control power (two of each channel), some number of logic comparators (I'm not educated enough in electronics to know what the component would be called) to make the output high for one MOSFET and low for another (for the gates), and maybe some transistors if the 555 output couldn't handle the brief current of charging the gates.
I have an old froo-froo LED flasher kit I put together years ago that uses two transistors and some caps and resistors; this makes me think there has to be a simple way to do what I'm trying here using just two MOSFETs but I cannot find it and, quite honestly, I think I may be too much of an amateur to know what the right terms are to search for it.
Anyway, sorry for the length but I wanted to explain what I was after and that I did try to find the answer before posting. Of course, if it goes like it does when I ask where the restroom is in a business then someone will point right over my shoulder behind me and say, "There.". :)
Thanks in advance.