Patent ID: 7573248

Claim:
A step-up switching voltage regulator circuit which outputs as an output voltage a voltage obtained by raising a power voltage supplied from a battery, comprising: a switch which switches an output in such a manner as to output the power voltage supplied from the battery as the output voltage when the power voltage supplied from the battery is larger than a predetermined output voltage, and in such a manner as to raise the power voltage supplied from the battery to the predetermined output voltage and to output the raised voltage as the output voltage when the power voltage supplied from the battery is smaller than the predetermined output voltage, wherein a light emitting diode is driven by the output voltage, and the output is switched based on a cathode voltage of the light emitting diode; and a plurality of light emitting diodes which are driven by the output voltage, wherein the output is switched based on the lowest cathode voltage among the cathode voltages of the plurality of light emitting diodes.