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The circuit design is based on a Weinberg topology, which is sort of like a push-pull switching power supply with a flyback transformer. This was selected because it appears to have a response that will allow reasonably efficient solar power conversion during bright midday sunlight and also during twilight hours until Vin dips below Vo/2.

After failing once with a basic buck converter brain-dumped onto a whiteboard and yet again with a full-bridge topology ripped from some application notes, I did some reading and settled on the Weinberg circuit.

A Beaglebone Black was selected for the controller for convenience and cheapness. Features that would be nice to have would be automatic tuning of power supply parameters, data logging, remote control and monitoring and other fun stuff. These are low priorities.

I'm currently struggling with getting the PWM subsystems under control on the am335x to generate the switching waveforms. All 6 of the chip's PWM outputs seem ideally suited to this application, however the drivers in the Linux kernel are not. The main control that is missing is the phase offset between A and B outputs. Frequency modulation would be nice to have but is not absolutely necessary. I'm currently looking at writing some PRU software as a bridge between userspace and PWM controls because it doesn't require rebuilding the kernel (ugh). I have a feeling that it might actually be a more efficient method to feed data to the PWM subsystem than throwing strings at /sys/class/pwm/.

Analog inputs are also a concern. To keep the design simple, I'd like to use the analog touchscreen inputs on the am3359, but they are limited to 0-1.8V and notoriously noisy. Obviously the right way to do this is to bolt on a differential ADC, but I'm going to try to prove that the am3359's inputs are useless first. Since the - input terminal tends to dip down below GND voltage, I'm going to try to pull the analog reference down maybe 0.2V with a reference diode and use the same divider that is on the positive input. Op-amps feeding the am3359 inputs are also an option but would probably require a dual-rail supply or negative voltage generator.

Information I have found to be helpful