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Topic: Ardubuck V3.0. Arduino based buck converter for use as a solar MPPT controller (Read 2440 times) previous topic - next topic

antman85

Following on from my older projects i wanted to design a buck converter to work with the Arduino so that I can charge my lead acid and lithium batteries from higher voltage domestic solar panels.

Older thread here
http://forum.arduino.cc/index.php?topic=247320.0

I finally got the time to design, build and test a newer revision after learning mistakes from the old ones.

The unit is based around the IR2184 synchronous mosfet controller. I am using an awesome high power inductor from coilcraft and 60V mosfets. It is a single sided pcb with thermal via's so that it can be stuck inside a metal enclosure or onto a heatsink with themal tape to remove the heat.

After testing the buck converter section is around 96 - 98% efficient which I am very happy with. Unfortunately to make the design cheaper and simpler I used 4 low forward voltage drop diodes to protect against reverse polarity and reverse current leakage. This brings the actual efficiency down to 89 - 94% which is better than most of the chinese rubbish on the market anyway. I may improve this at a later date by using an ideal diode circuit.

Here is a quick video showing it working :)
https://www.youtube.com/watch?v=FoQ4FwA329g

antman85

I have carried out more testing since it has been more sunny here in the last couple of days. The MPPT works very well in sunny conditions but gets stuck at a false power point at lower wattages. The software I am using is not the best since it works based on output current not output power. I think having a routine in software that resets the MPP every five minutes would be ideal.

I have no idea how to code Arduino at all so I am using code from Rusdy Simano with adjusted variables. It works ok but could be alot better. I am also losing efficiency at higher power levels due to the 32Khz operating frequency. 50 - 60Khz is much better for this circuit.

Here is a vid showing the unit tracking the MPPT. Voltage shown is input voltage and the oscilloscope is showing the changing duty cycle.
https://www.youtube.com/watch?v=LLOfkegiPrg
 

antman85

Here is a couple of close ups



Testing efficiency. The top meter is input power. The bottom is output. 93.7% at this power level.

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