Patent ID: 7808496

Claim:
An apparatus for supplying power source comprising: a boosting circuit configured to boost a battery voltage and including a first node to which the boosted battery voltage is outputted, and a first signal terminal to which a first controlling signal is inputted; a boosted voltage detecting circuit configured to detect the boosted battery voltage, and transmit the detection result to the boosting circuit; and an output selecting circuit coupled to the boosting circuit and the boosted voltage detecting circuit, and configured to provide selectively the boosted battery voltage to a first display device and a second display device, wherein the boosted voltage detecting circuit includes a second node connected to the first node, a third node transmitting the detection result detected by the boosted voltage detecting circuit to the boosting circuit, a first resistor and a first capacitor connected in parallel to each other between the second node and the third node, a second resistor connected between the third node and a ground, a third resistor and a first switch connected in series between the third node and the ground, and a second capacitor connected between the second node and the ground, wherein the output selecting circuit includes a second switch connected between the second node and the second display device, and a third switch connected between the second node and the first display device, and the first and the second switches are controlled by a second controlling signal from a second signal terminal, and wherein the boosted voltage detecting circuit, the second switch and the second display device are sequentially connected in series, and the boosted voltage detecting circuit, the third switch and the first display device are sequentially connected in series, wherein the output selecting circuit further includes an inverter which provides a reversed signal of the second controlling signal to the third switch, wherein in case of the first switch is turned off, the second switch is turned on, the third switch is turned off, the second display is turned on the first display is turned off, and the first resistor is coupled with the second resistor in serial, wherein in case of the first switch is turned on, the second switch is turned off, the third switch is turned on, the second display is turned off, the first display is turned on, the second and third resistors are coupled to each other in parallel, and the first resistor is coupled to the third node in serial.