Power supply device including induction voltage detection coil for charging portable electronic devices

In combination, a power supply device detachably connected to a portable electronic terminal device for supplying power for charging a rechargeable battery included in said terminal device by non-contact electromagnetic induction, comprising:

• a secondary coil in said terminal device connected to said battery;
• said power supply device further including a primary coil juxtaposed to said secondary coil, an oscillation switch, a detection coil inductively coupled to said primary coil and detection coil inductively coupled to said primary coil and responsive to a variation in magnetic flux of an alternating signal applied to said primary coil by said oscillation circuit for detecting a load fluctuation resulting from and varying in accordance with a change in the distance between said primary coil and said secondary coil, and for outputting a voltage signal representing the load fluctuation as a change in an induction voltage induced in said detection coil, and
• a control means which controls, based on the change in the induction voltage output by the detection coil, an output of said oscillation circuit so that the power supplied to the secondary coil remains constant.