Patent ID: 8786252

Claim:
A battery charger cradle designed to be used with a battery built-in device having an induction coil and a battery rechargeable with power induced by the induction coil, the battery charger cradle comprising: a primary coil for inducing electromotive force to the induction coil; a movement mechanism for moving the primary coil; and a position detection controller for detecting a position of the induction coil and controlling the movement mechanism to bring the primary coil closer to the induction coil, wherein the position detection controller includes: a plurality of position detection coils; a pulsed power source for supplying a pulse signal to one of the position detection coils; a receiver circuit for receiving an echo signal outputted to the position detection coils from the induction coil which is excited by the pulse signal; and a discrimination decision circuit for detecting a level of the echo signal received by the receiver circuit and judging the position of the induction coil on the basis of the level of the echo signal.