You see many relatively simple options for chargers with power path function and (2) inputs, but…what about the case where you have (3) inputs and the third input is from a solar cell?
How would you architect a charger for a single LiPo 2200mAh battery that can accept input from the three different sources below.
The system should source power in the priority listed if multiple inputs are present. The system should have protection to allow any of the sources to be simultaneously present.
1) External +5 to +12V 500 mA max.
2) +5V from USB. 500 mA max.
3) Small Solar Cell (widest range of Voc 3-12V preferred ). 100 mA max.
One thought is a buck converter with power path and charger for (1) & (2) and a separate charger optimized for use with a small solar cell for (3), and then a power multiplexer to select which output to feed to the battery? Will that work?
Another approach might use the same IC for (1) & (2) plus a buck-boost optimized for use with a small solar cell and output = +5V placed ahead of the first IC and then add a power mux to select the source input. This system would have cascaded switchers so there would be an efficiency penalty, but perhaps other benefits.
Comments? Part suggestions?