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| Boost converter + lipo charger/battery protection circuit |
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| aiq25:
Hi. I designed a boost converter + lipo charger/battery protection circuit (based on YouTuber GreatScott!'s design). I would appreciate some feedback. Attached are the Gerbers, view of all PCB layers and schematic files. I would like to test the boost and battery circuits seperately, so I have two SMD pads that I will bridge to connect the two circuits later on. This was designed in KiCad. I can share those files if anyone is interested. |
| Peabody:
As I remember his circuit, it did not include something called load sharing. This is needed if you want to charge the battery and power your device at the same time. Load sharing allows the Vbus source to power both the load and the charger independently so the load doesn't have to be supplied by charger current. If that happens, the load current may prevent the charger from ever shutting down, which would be a safety problem. http://ww1.microchip.com/downloads/en/AppNotes/01149c.pdf http://blog.zakkemble.net/a-lithium-battery-charger-with-load-sharing/ Basically, load sharing requires adding a P-channel mosfet, a schottky diode and a resistor. |
| aiq25:
--- Quote from: Peabody on March 15, 2019, 01:09:53 am ---As I remember his circuit, it did not include something called load sharing. This is needed if you want to charge the battery and power your device at the same time. Load sharing allows the Vbus source to power both the load and the charger independently so the load doesn't have to be supplied by charger current. If that happens, the load current may prevent the charger from ever shutting down, which would be a safety problem. http://ww1.microchip.com/downloads/en/AppNotes/01149c.pdf http://blog.zakkemble.net/a-lithium-battery-charger-with-load-sharing/ Basically, load sharing requires adding a P-channel mosfet, a schottky diode and a resistor. --- End quote --- Thanks. I thought about this after completing the PCB. This module will be used for a small portable game system I'm building, so I don't think it's a big issues for me but I will add it to a future revision of this board if it works out. |
| janoc:
--- Quote from: Peabody on March 15, 2019, 01:09:53 am ---Basically, load sharing requires adding a P-channel mosfet, a schottky diode and a resistor. --- End quote --- Or a charger IC with a "power-path" feature built-in. E.g. TI has a few chips such as bq25890, bq25606 etc. that do this. The features these have, such as the OTG support, may be an overkill, but if space is at premium it is likely worth it than hacking up a discrete solution. They even support a "supplement mode" where if the load needs more current than available from the charger the rest will go out of the battery automatically. These are also fast chargers - supporting the USB BC 1.2 spec, the various non-standard resistor-between D+/D- pin hacks and there are even variants supporting the USB C Power delivery standard. Just beware, the datasheets of these are a horrid confused mess :( |
| Peabody:
The MCP73871 also supposedly has sharing built in. But I have no experience with it. |
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