Inductive Charging

Discussion in 'General Electronics Chat' started by machman, Mar 3, 2006.

  1. machman

    Thread Starter New Member

    Mar 3, 2006
    Can anyone explain how an electric toothbrush charging system works? I know it uses inductive charging but I can't find a detailed explanation anywhere that really describes the process. How does it take 120V AC and turn it into 1.5V DC for the battery? How far can the voltage travel across the inductors? Could the inductors be 2 inches apart and still receive power? Does anyone know a place that describes the process?
    Much thanx!!
  2. hgmjr

    Retired Moderator

    Jan 28, 2005
    Try googling with the term "splash power" or you may want to try splash-power. This is the term I seen used to refer to the inductive battery charging technique.

  3. machman

    Thread Starter New Member

    Mar 3, 2006
    thanx for the reply. I am familiar with Splashpower but they don't explain the process as it is new patented technology. I am looking for something much more specific as I'm a novice electronics hobbyist trying to understand the process.
  4. Papabravo


    Feb 24, 2006
    I don't know for absolute certainty, but it seems like an ordinary transformer. The primary winding is in the base. The secondary winding is in the toothbrush. I think the geometry is two coils on a common axis, one inside the other.

    In the toothbrush the AC voltage is rectified and used to charge a battery. When you remove the toothbrush from the stand and hit the button the battery drives the brush actuator. When done it goes back in the stand for another charge cycle.

    That's my opinion, and I could be wrong.
  5. windoze killa

    AAC Fanatic!

    Feb 23, 2006
    Pretty much as you explained it. The one I pulled apart had a coil in the bottom and a small and very rough rectifier to charge the battery.
  6. thingmaker3

    Retired Moderator

    May 16, 2005
    Patents are public record.

    Splashpower patent at USTPO

    another Spashpower Patent at USPTO

    (Note, one needs a TIFF viewer to get full use of the USPTO website)

    Looks to me like it works same as the toothbruch, but at a higher frequency (eliminating need for a core). The really cool part (from my point of view) is the automatic frequency control.
  7. van_loke

    New Member

    Mar 30, 2006

    I too am a amateur and trying to build and test some electronic ckt as a hobby, and do understand the theory but need help on specifics.

    For eg: In the primary side, there would be a switching ckt, <200KHz, and the secondary side a resonant circuit. If I use an air coil in the secondary is it enough or do we need a ferrite core?

  8. mangtronix

    New Member

    Apr 10, 2006
    Patent 6,934,167 "Contactless electrical energy transmission" is good and not too complicated. I'm looking through it now.

    I like this site for generating pdfs
    The text comes out as images though, so you can't search/select.