Author Topic: A Lithium Battery Charger with Load Sharing  (Read 2098 times)

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Offline chota.sanjiv

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A Lithium Battery Charger with Load Sharing
« on: June 11, 2016, 07:55:46 pm »
Hi Guys,

I was referring the following circuit for battery charger with load sharing ie. the circuit will get powered via main power and when its not there it will switch to battery immediately, in the circuit I cannot understand the R2 pull down ,won't it cause extra power consumption for my circuit. ?

http://blog.zakkemble.co.uk/wp-content/uploads/2013/05/MCP73831_loadshare.png

regards,
Sanjeev
 

Offline ConKbot

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Re: A Lithium Battery Charger with Load Sharing
« Reply #1 on: June 11, 2016, 08:06:52 pm »
Without r2, what happens when the charger is removed? The voltage on the VDD net will be floating at a point where the diode leakage and current used by the charger ic are equal. The mosfet may not be turned on fully or at all, adding a diode drop between the battery and the load. With the pulldown, VDD goes to ground, the mosfet his turned on fully, and the load gets full battery voltage.
 

Offline Signal32

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Re: A Lithium Battery Charger with Load Sharing
« Reply #2 on: June 13, 2016, 08:13:01 pm »
As ConKbot mentioned, R2 is required so that the circuit will function correctly. And yes, you are correct, it will add extra load to your circuit, though a very small one (0.05mA).
 


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