A linearly regulated power supply is provided for providing a load voltage to a load. In a preferred embodiment, the linearly regulated power supply includes: a voltage divider module for receiving a backup voltage and then providing a voltage reference; a controlling module for receiving the voltage reference and then providing a controlling voltage; and a regulating module receiving the controlling voltage and then regulating a core voltage down to a load voltage, the regulating module providing the load voltage to a load. The linearly regulated power supply is capable of reducing the power of the transistor, and has a higher efficiency.