Power-saving circuitry and method of cpu

A power-saving circuitry of CPU, wherein an operating voltage of the CPU is adjusted based on a voltage identification code, and one bit code of the voltage identification code is outputted via an identification code switching circuitry, and the power-saving circuitry comprises:

• a first switching transistor having a first source/drain electrode, a second source/drain electrode, and a gate electrode, wherein the first source/drain electrode of the first switching transistor is grounded, the second source/drain electrode of the first switching transistor is electrically coupled to a DC power, and the gate electrode of the first switching transistor is electrically coupled to the CPU, and when the CPU is under a normal operation mode, the first switching transistor is turned on, and when the CPU is under a power-saving mode, the first switching transistor is turned off;
• a diode having an anode electrically coupled to the second source/drain electrode of the switching transistor;
• and
• a second switching transistor having a first source/drain electrode, a second source/drain electrode, and a gate electrode, wherein the first source/drain electrode of the second switching transistor is electrically coupled to the cathode of the diode, the second source/drain electrode of the second switching transistor is electrically coupled to an output terminal of the identification code switching circuitry for determining a state of the voltage identification code, and the gate electrode of the second switching transistor is electrically coupled to a control terminal of the identification code switching circuitry for receiving a selection signal to turn on either the second switching transistor or the identification code switching circuitry.