Feedback on USB-C for Powering + LiPo Charging

TL;DR: I need a technical check on my circuit design that utilizes LiPo battery & USB-C charging.

Hi everyone! I couldn’t find a sub-category in the forum that fit my post so I just put it under general electronics.

I’ve been working on a project to build my own camera slider. It’s powered by Sparkfun Pro Micro and A4988 Stepper Driver Modules. Right now, I’m using only one stepper motor but I do want to have the option to have two more stepper motors for more degrees of movements in the slider. Each motor is rated at 12V and 0.4A/phase.

I’m designing the PCB (on EasyEDA) and I have a few constraints in terms of how it will be powered; either through a USB-C connector or the LiPo battery. The battery itself can also be recharged by the USB-C port. As for the power through the USB-C port, I’m going with the standard 15W option (5V & 3A) so I don’t have to deal with the whole USB-PD circuitry BS that comes with it. There is a switch that will turn on the Arduino & motors from either the battery or USB-C power source. When the switch is off, the battery can still be recharged if the USB-C is plugged in.

For the components, I’m thinking of choosing this battery from Adafruit as it should provide enough power for now. I also found this YouTube video from Electronoobs on battery charging and boost converting so I followed along for my circuit design. I mixed and matched to try to fit my need. I’ve attached a screenshoot of the circuit that involves the power management. Note that the “C” and “NO” nets are the common and normally-open pins of the power switch. The diode “D2” is to force the anode (+ side) to flow the positive/conventional current from the battery to the boost converter and not back into the TP4056 recharging IC. Diode “D1” is to prevent the 5V current from the USB-C Vbus to flow to the anode of the battery which is 3.7V.

If you see any potential problems with my design or got some questions, please comment on it. I want to make the PCB design using this circuit ASAP so I can get it made. I’m still very new to this area of circuitry. Thanks!

First, I think your protection circuit is wrong. The FS8205A functions as a low-side switch between the battery’s minus terminal and system ground. But you don’t have the ground connection. I think pins 6 & 7 should be connected to GND.

Second, I have concerns about your dual Schotty diode setup - D1 and D2. You will have some voltage drop across D1, which will reduce battery life. And there may be significant reverse leakage current through D1, which could overcharge the Lipo. So I would replace all that with a “load sharing” circuit, which would replace D1 with a P-channel mosfet, oriented kinda backwards, and a resistor. The mosfet would have no voltage drop, and no reverse leakage current. And I think I would just make D2 a regular diode.

I haven’t really looked at the rest of the circuit, and know nothing about USB C, so can’t help with that.

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