Connect with us

Switching power source on plugin for battery charger

Discussion in 'Electronic Design' started by Zebov, Sep 26, 2007.

Scroll to continue with content
  1. Zebov

    Zebov Guest

    'm designing my first battery charging circuit for a device and need
    some assistance. As a preface, I am charging a 3.7V 850mAh Polymer
    LiIon battery from a 5V wall-wart through a MAX1555.

    I have a battery charge circuit and I have the rest of my circuit
    which runs off of 3.3V (3.7V down-converted to 3.3V via a MAX710 step-
    down) pulling about 100mA. My problem comes when I merge the two
    parts.

    I don't want to overcharge my battery and would like the circuit to be
    running while the battery is charging. The problem is, if I just
    connect the battery + to the +rail of the circuit, it will draw 100mA
    +battery charging draw. Will this confuse the MAX1555 and make it not
    turn off when it's supposed to?

    My first thought is to somehow switch power sources from the battery
    to the 5v wall (through a step-down to get 3.3V) whenever the 5V
    supply is plugged in. I'm trying to think of the best way to do
    this. I was thinking of just putting steering diodes between the
    battery and wall rail but don't think this will work well because the
    battery will be switches on once it is charged and I'll run into the
    same problem as if I was just running off the battery charging rail by
    itself (as mentioned previously). Any suggestions? Thanks ahead of
    time for the help.

    - Wes
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-