POWER SUPPLY UNIT

PROBLEM TO BE SOLVED: To provide a power supply unit which reduces the number of components and weight of the power supply unit, and which enhances the efficiency of power source by reducing power consumption, realizing stable power supply to a memory. SOLUTION: The power supply unit comprises a main power source, a sub-power source, a reference voltage source wherein the power source voltages of the main power source and of the sub-power source are input to output the reference voltage when the voltage of either power source exceeds a given voltage, at least one first constant voltage power supply circuit wherein the power voltage of the main power source and the reference voltage are input to output the constant voltage, and at lease one second constant voltage power supply circuit wherein the power voltage of the sub-power source and the reference voltage are input to output the constant voltage. COPYRIGHT: (C)2006,JPO&NCIPI