Patent ID: 7215043

Claim:
A power supply voltage switching circuit for selecting a power supply voltage for an integrated circuit according to a first control signal, the circuit comprising: a high power auto selecting module for automatically generating an intermediate voltage according to a higher one of a voltage output by a first outer power pin and a second outer power pin which are directly connected to the high power auto selecting module at the same time without additional circuits or transistors, the high power auto selecting module comprising: a first transistor where a first terminal of the first transistor is electrically coupled to the first outer power pin without additional circuits or transistors, a second terminal of the first transistor is electrically coupled to an intermediate node, and a gate of the first transistor is directly connected to the second outer power pin without additional circuits or transistors; and a second transistor where a first terminal of the second transistor is directly connected to the second outer power pin without additional circuits or transistors, a second terminal of the second transistor is electrically coupled to the intermediate node, and a gate of the second transistor is directly connected to the first outer power pin without additional circuits or transistors; wherein the high power auto selecting module selectively generates an intermediate voltage according to a higher one of the voltages output by the first outer power pin and the second outer power pin which are directly connected to the first terminals and gates of the first and second transistors at the same time, and wherein the high power auto selecting module generates an intermediate voltage automatically with no additional control signal; a level shifting module electrically coupled to the high power auto selecting module for inputting the intermediate voltage as a power supply of the level shifting module, for performing level shift on the first control signal according to the intermediate voltage; and a selecting switch module electrically coupled to the level shifting module, for selectively outputting the voltage output by the first outer power pin or the voltage output by the second outer power pin as the power supply voltage of the integrated circuit according to the level-shifted first control signal.