Patent ID: 7636377
Filing Date: 2009-12-22
Classification: G11B

Abstract:
1. An optical disc laser power control circuit, comprising: at least two laser diodes for emitting laser beams, the laser beam being emitted for reproducing or recording data from/to an optical disc; a first current source; a second current source coupled to the first current source, the second current source and the first current source coupled in parallel to a single control output; a memory unit coupled to the second current source, the memory unit configured for storing a predetermined laser diode working current value; a laser diode driver for controlling emission power of one of the at least two laser diodes with a driving current supplied from the single control output; a photodetector for detecting at least part of laser beams emitted from the laser diode to convert the emitted laser power into an electrical signal, where the electrical signal is configured to be fed back to the automatic power control circuit; an amplifier coupled to an output of the photodetector, where the amplifier is configured to adjust at least one conversion resistance value; and an automatic power control circuit coupled to the first current source, the automatic power control circuit for controlling the first current source, where the automatic power control circuit is configured for comparing the converted electrical signal and a target laser power and is configured to adjust the first current source based on a compared converted electrical signal and a target laser power, where a register value is set to zero when the automatic power control circuit is frozen during a write operation; wherein the ratio of the full scale current output values of the first current output mode DAC and the second current output mode DAC lies between eight and eighty, and wherein the first current source is a fine pitch current source, the second current source is a coarse current source configured to set a current based on the predetermined laser diode working current value, and the first current source is configured to be operable independent from the second current source.