Abstract: A circuit for supplying power to an IC memory card by using primary and secondary batteries as a data preserving power means for the memory IC according to the present invention, includes: primary and secondary batteries; a secondary battery charging circuit for charging the secondary battery; and a primary and secondary battery backup circuit for connecting the primary and secondary batteries to the memory IC when an external power source is disconnected; a serial-parallel switching means for connecting the primary and secondary batteries in series or in parallel; a voltage detecting means for comparing a power voltage of the memory IC with a reference voltage to generate a voltage detection signal upon finding the power voltage dropped to below the reference voltage; and a switching control means for receiving the voltage detection signal of the voltage detecting means to control the serial-parallel switching means so as to connect the primary and secondary batteries in series or in parallel.