Patent ID: 7825539

Claim:
An electronic device comprising: a first power supply unit; a second power supply unit; a control circuit connected between the first power supply unit and the second power supply unit, capable of determining whether to receive power from the second power supply unit to cooperatively power a load with first power supply unit, the control circuit comprising: a detecting unit receiving an operating current signal of the first power supply unit, and transforming the operating current signal into an analog voltage signal; an analog-to-digital converting unit transforming the analog voltage signal into a digital signal; a microcontroller calculating a value of an output power of the first power supply unit according to the digital signal, and comparing the output power with a rated power of the first power supply unit; and a switch unit; wherein the microcontroller turns on the switch unit to allow the second power supply unit to power the load in response to the output power exceeding the rated power of the first power supply unit; and an output connector configured for connecting and supplying power to the load; wherein the detecting unit comprises a current detector comprising: a first gain resistor pin receiving a first voltage signal from the first power supply unit via a first resistor; a second gain resistor pin receiving the first voltage signal from the first power supply via a second resistor and a third resistor connected in series, and connected to the output connector via the second resistor; and an output pin connected to the analog-to-digital converting unit; and wherein the analog-to-digital converting unit comprises an analog to digital converter (ADC) comprising: an analog signal input pin connected to the output pin of the current detector, and grounded via a fourth resistor; a positive reference voltage pin connected to a node between the second resistor and the third resistor; a negative reference voltage pin grounded; a digital signal output pin connected to a first pin of the microcontroller; a chip selection signal pin connected to a second pin of the microcontroller; and a clock signal pin connected to a third pin of the microcontroller.