Inductive charging

[alphacat]

Hello.
I read about inductive charging in Wikipedia.
I understand that it is implemented by two coils - one in the charging baes, and second in the mobile device - where the second coil transfers the inductive energy into electical current which charges the battery.

I was looking for schematics of such system which include both the charging base-station and the unit which comprises the battery, however I didnt manage to find any.

Could you please refer me to schematics?

Thank you.

 

[Hero999]

There is no schematic for a simple inductive charger.

The base is just a transformer primary and the secondary is mobile device which has a rectifier, smoothing capacitor and battery charger which is often as simple as a resistor.

The weight can be reduced by using a higher frequency. In this case a self-oscillating circuit such as blocking oscillator or Royer converter is normally used (because it's cheap and reliable) for the primary and a high speed Schottky rectifier is used for the charger on the secondary. Plenty of schematics for blocking oscillators and Royer converters can be found using Google.

 

[nickagian]

My advice is to search for RFID communications at the frequency range of High Frequency (13.56MHz). These systems use exactly the principles of inductive coupling that you look for! RFID tags at 13.56MHz are powered from the magnetic field created from the RFID reader. You can find a lot of schematics in this field, until of course the point of delivering DC power to the charging circuit. The electronics for charging the battery depend on the battery that you want to charge.

Just one more thing. Have in mind that for delivering enough power for charging a battery within a logical period of time, you'll need to place the two systems (the primary and the secondary coils) very close to each other. The distance should be less than 10-20cm. Unless you have a battery with very small capacity (coin batteries etc.)

You can also find useful information at the Fraunhofer website (Fraunhofer IIS Homepage) - > search for energy harvesting

 

[Hero999]

The good thing about using a PCB program, is that you can ensure the PCB is correct and all the connections go to the right places. If you design the PCB without a schematic net-list then it's easy to make silly mistakes which can go unnoticed.