Method of maximizing power efficiency for power amplifier system and power amplifier system thereof

A power amplifier system for maximizing power efficiency, comprising:

• a power amplifier;
• a power supply, for supplying a power supply voltage;
• a controller, for determining whether the power amplifier is activated according to a communication protocol to generate a determination result and generate a select signal according to the determination result;
• and
• a converter, coupled to the power amplifier, the controller and the power supply, for converting the power supply voltage into a supply voltage having a first voltage level or a second voltage level to supply the power amplifier according to the select signal;
• wherein the second voltage level is lower than the first voltage level.