Hi everyone. Im doing a little reverse engineering of a failed solar charger. Im not sure what has happened to it, but it doesnt seem to be charging any more.
Curious about how it works, particularly on the "power side" of things I traced out some of the pins between the MOSFETs and power terminals and came up with the attached image.
Trying to get my head around exactly how Q1 and Q2 are interacting.
Q3 I assume could be PWM'd to achieve a particular load output voltage, or could simply be switched on hard to connect the load directly to the battery. There does seem to be a means to turn the load on and off via some buttons, so either of those.
Q1 I can imagine might also be PWM'd to achieve a charging voltage for the battery from the solar input voltage.
But other than using the reverse body diode in Q2 to provide a path back to the solar panel, I cant quite work out why there is another MOSFET in this position.
The gates of all three MOSFETs do seem to be connected to the microcontroller in some way, through a convoluted maze of zener diodes, resistors and transistors that I havent quite been able to trace out, so it would seem they are all actively controlled in some way.
Can anyone share any insight on what they think is going on?
All MOSFETs are FBM75N68's.
Thanks.