Patent ID: 8416661

Claim:
An optical disk device comprising: a plurality of semiconductor laser diodes configured to emit laser lights of different wavelengths; an output controller configured to control light output of semiconductor laser diodes; and a composite power source configured to generate a plurality of voltage power supplies from a single voltage power source in order to drive the plurality of semiconductor laser diodes and to operate the output controller, and configured to selectively output the generated power supplies, the composite power source comprising an input port configured to receive a first control signal at a time of voltage selection and being configured to cause an output voltage to change from a selected first constant voltage to a selected second constant voltage which is higher than the first constant voltage, and to cause the output voltage to change from the second constant voltage to the first constant voltage which is lower than the second constant voltage, via multiple voltage levels between the selected first and second constant voltages in response to the first control signal, wherein the first control signal comprises a pulse train, and the composite power source is configured to cause the output voltage to change stepwise each time a pulse of the pulse train is input to the input port.