Hello
There is a problem that seems well recognised, that it can be difficult to charge a LIPO battery while that battery is still powering a load. A solution to this, using the MCP73831 as the charging chip, is described here: http://blog.zakkemble.net/a-lithium-battery-charger-with-load-sharing
The circuit there uses a P channel mosfet to switch off power to the load while the battery is charging, and instead power the load from the USB port, via a Schottky diode.
Since I do not need the load to be switched on while the battery is charging, it is sufficient simply to cut power to the load while there is a voltage present from the USB, therefore it seems to me I do not need the diode. Also, I am in fact charging from a wireless charger which has an output of 4.2V rather than the 5V from a USB.
So I am hoping that this schematic will work
Apart from - will this work, my small questions are: presumably R1 can be any reasonably high value, eg 100k, enough to pull the gate low when there is no voltage from the charger, but small enough to not cause a voltage drop that would stop the MCP73831?
Also, is that capacitor really necessary, given that there is already one on the other side of the battery
There is a problem that seems well recognised, that it can be difficult to charge a LIPO battery while that battery is still powering a load. A solution to this, using the MCP73831 as the charging chip, is described here: http://blog.zakkemble.net/a-lithium-battery-charger-with-load-sharing
The circuit there uses a P channel mosfet to switch off power to the load while the battery is charging, and instead power the load from the USB port, via a Schottky diode.
Since I do not need the load to be switched on while the battery is charging, it is sufficient simply to cut power to the load while there is a voltage present from the USB, therefore it seems to me I do not need the diode. Also, I am in fact charging from a wireless charger which has an output of 4.2V rather than the 5V from a USB.
So I am hoping that this schematic will work
Apart from - will this work, my small questions are: presumably R1 can be any reasonably high value, eg 100k, enough to pull the gate low when there is no voltage from the charger, but small enough to not cause a voltage drop that would stop the MCP73831?
Also, is that capacitor really necessary, given that there is already one on the other side of the battery
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