Hello. I'm working on making a device that I want powered by a Li-ion battery, like this one:
SparkFun Electronics - Polymer Lithium Ion Battery - 1000mAh
I want some sort of charging circuit for my device, and I'm thinking of using a MCP73837/8:
MCP73838
I would like to be able to charge using an ac-dc adapter for fast charging, but also have the ability to charge through usb safely. I would also like to charge from a 5V solar panel that is always connected to my device. The microchip above does the switching between the adapter and usb safely.
Here is my proposed circuit (also in attached pic in case imageshack doesn't work):
**broken link removed**
I have a very poor understanding of electronics, but here is my reasoning for the design:
D1 and D2 protect the adapter and solar cell. I plan to use 5V, 9V and 12V adapters.
The mess with the 6V zener and the 6V regulator and the 2 mosfets are intended to protect the microchip. It can take a max input of 6V, but I want to use 9V and 12V adapters too. I'm hoping that the circuit will operate as follows: At 5V input, the P-mosfet's gate is grounded, so the mosfet lets current through to the chip. The N-mosfet does the opposite. At higher than 6V, the zener lets current through, and the P-mosfet's gate is now high. The N-mosfet now lets current through to the 6V regulator, which now passes 6V to the chip. D3 protects the regulator, D4 protects the P-mosfet.
I do have a few questions:
1) Is it ok to have the Load attached to the Li-ion while it is charging?
2) I don't know if my circuit will work or not. Before I go and buy the parts, can anyone see any problems or any changes?
3) I don't know if D1, D2, D3 and D4 are really needed. Can someone confirm that they should be there?
4) The Li-ion is 3.7V, but my Load requires 3.3V. I plan to use a 3.3V regulator, but that requires an input of like 5V. Is there a way around this? Are there 3.3V regulators that accept voltages below 3.7V?
5) If there is no sunlight, and the usb and 5-12V sources are not connected, would the MCP73837/8 chip be ok with the Li-ion still attached to it?
6) I intend to set the charge current to be 1A in the MCP73837/8 chip, however the solar cell cannot deliver that much, only the adapter can. Would the MCP73837/8 be ok with something like 100mA input instead of the expected 1A? I'm hoping it'll just charge slower.
Thanks for your time!
SparkFun Electronics - Polymer Lithium Ion Battery - 1000mAh
I want some sort of charging circuit for my device, and I'm thinking of using a MCP73837/8:
MCP73838
I would like to be able to charge using an ac-dc adapter for fast charging, but also have the ability to charge through usb safely. I would also like to charge from a 5V solar panel that is always connected to my device. The microchip above does the switching between the adapter and usb safely.
Here is my proposed circuit (also in attached pic in case imageshack doesn't work):
**broken link removed**
I have a very poor understanding of electronics, but here is my reasoning for the design:
D1 and D2 protect the adapter and solar cell. I plan to use 5V, 9V and 12V adapters.
The mess with the 6V zener and the 6V regulator and the 2 mosfets are intended to protect the microchip. It can take a max input of 6V, but I want to use 9V and 12V adapters too. I'm hoping that the circuit will operate as follows: At 5V input, the P-mosfet's gate is grounded, so the mosfet lets current through to the chip. The N-mosfet does the opposite. At higher than 6V, the zener lets current through, and the P-mosfet's gate is now high. The N-mosfet now lets current through to the 6V regulator, which now passes 6V to the chip. D3 protects the regulator, D4 protects the P-mosfet.
I do have a few questions:
1) Is it ok to have the Load attached to the Li-ion while it is charging?
2) I don't know if my circuit will work or not. Before I go and buy the parts, can anyone see any problems or any changes?
3) I don't know if D1, D2, D3 and D4 are really needed. Can someone confirm that they should be there?
4) The Li-ion is 3.7V, but my Load requires 3.3V. I plan to use a 3.3V regulator, but that requires an input of like 5V. Is there a way around this? Are there 3.3V regulators that accept voltages below 3.7V?
5) If there is no sunlight, and the usb and 5-12V sources are not connected, would the MCP73837/8 chip be ok with the Li-ion still attached to it?
6) I intend to set the charge current to be 1A in the MCP73837/8 chip, however the solar cell cannot deliver that much, only the adapter can. Would the MCP73837/8 be ok with something like 100mA input instead of the expected 1A? I'm hoping it'll just charge slower.
Thanks for your time!