Patent ID: 8368669

Claim:
A position detecting device, comprising: a position pointer to transmit a position-pointing signal using power supplied from a rechargeable power storage unit of said position pointer; and a tablet to detect a position pointed to by said position pointer using the position-pointing signal transmitted from said position pointer, wherein said position pointer comprises, a coil for generating power from an alternating magnetic field transmitted from an excitation coil of said tablet, a charging circuit for charging said rechargeable power storage unit using the power transmitted through said coil of said position pointer, and a transmitter for transmitting the position-pointing signal to said tablet, and wherein said tablet comprises said excitation coil wound around a periphery of a position detecting area of said tablet, an excitation circuit to drive said excitation coil for generating the alternating magnetic field, a position-pointing signal detector to detect the position-pointing signal from said position pointer, and an excitation controller to control said excitation circuit to cause said excitation coil to generate the alternating magnetic field based on a determination that said position pointer is in a peripheral portion within said position detecting area and to cause the excitation coil not to generate the alternating magnetic field based on a determination that said position pointer is in a central portion of said position detecting area, said peripheral portion surrounding said central portion being defined by specific x and y coordinates within said position detecting area, the determinations being made based on detection of said specific x and y coordinates of the position-pointing signal by said position-pointing signal detector, said excitation controller controlling said excitation circuit to cause said excitation coil to generate the alternating magnetic field for charging said rechargeable power storage unit using said charging circuit when the determination is that said position pointer is in said peripheral portion within said position detecting area of said tablet, wherein said excitation controller initiates a charging operation for a predetermined period of time when said position pointer is located in said peripheral portion and initiates a transmission stop when said position pointer is not located in said peripheral portion.