Circuit for Recharging Battery with a Device

Question

I am working on a hardware design that is meant to run off of an internal 5V battery or via USB power, and also to have the battery be rechargeable via USB. I have been looking at battery recharge circuits like those found here: http://www.ti.com/lit/an/snva557/snva557.pdf

I was wondering how the design of the recharge circuit is affected by the battery being part of the device, and how I might go about powering the device and charging the battery simultaneously.

Right now I have the battery taken out of the circuit via a relay when external power is connected to prevent the device from receiving power from both sources, but this obviously needs to be modified for the battery to recharge.

Answer 1

You are asking to provide you with system architecture solution for your project. Although it is a very broad request, industry of mobile devices already has several basic ideas, and there are several companies who compete in the area of "battery power management". Usually the solution is to have a IC that detects the USB source capabilities, an IC that manages battery charging and clean switch (instead of relay) to external power (when available), and an IC that gauges the charge, all under a supervision of a microprocessor, typically over I2C communication.

To start, go Texas Instruments pages, and learn what do they offer in the area of battery PMIC.

This overview from Maxim looks extremely useful.