Selection circuit for dual batteries in a battery powered electronic device

DETAILED DESCRIPTION It is therefore an object of the invention to provide a battery selection circuit for battery powered electronic circuits having two battery packs in which discharging of batteries is effectively performed and battery usage time is substantially increased.
It is another object of the present invention to provide a battery selection circuit which can prevent overdischarging of a battery pack in dual battery powered electronic circuits.
In accordance with principle of the present invention, the above objects are achieved by a battery selection circuit for an electronic device which comprises: a first battery source; a second battery source; a battery detector for sensing the existence of the first and second battery sources and for producing detect signals corresponding thereto; a microcontroller for producing first and second battery discharge enable signals in response to first and second battery detect signals output from the battery detector; a first and second switch means for respectively connecting each power supply line from the first and second battery sources to a power supply circuit of the device in response to the first and second battery discharge enable signals; a cut off means for blocking reverse currents in the power supply lines and provided in series with the first and second switch means; a current path means for providing low resistive current paths and which is in parallel with the cut off means; a control means for opening the current path means when both the first and second battery sources are detected and for closing the corresponding low resistive current path when one of the first and second battery sources is detected.
In the preferred embodiment described below, the battery detector includes a pair of voltage divider resistors connected to a positive terminal of the first and second battery sources.
Thus, the battery detector senses output voltages of the first and second battery sources, and when the detected output voltages are below a preset voltage level, the microcontroller permits the corresponding battery discharge enable signal to be deactivated