Apparatus and method for controlling laser power for disc drive
AssigneeSamsung Electronics Co., Ltd.
InventorSung-un Yang
Life of this patent
Estimating the term…
Abstract
A laser power control apparatus and method prevent fluctuation in the level of laser power due to a difference between reaction speeds of an automatic power controller according to write speeds of a disc drive. In the apparatus and method, laser power can be automatically controlled to prevent a variation in the level of laser diode driving voltage in read power periods, according to the write speeds of a disc drive, in a write mode. Thus, it is possible to prevent unstable operations of a servo circuit due to a variation of the level of laser power and further, prevent deterioration in the quality of the servo circuit due to a variation in the level of a wobble signal, thereby stabilizing recording characteristics of the disc drive.
Claims19
An apparatus controlling laser power in a disc drive, comprising:
- a memory unit which stores reference laser power data according to write speeds, the reference laser power data being set to compensate for a variation in driving voltage input to a laser diode;
- a system controller which reads reference laser power data corresponding to a set write speed from the memory unit in a write mode and generates a reference power control signal corresponding to the reference laser power data;
- and
- an automatic power controller which controls the level of voltage, which corresponds to an optical signal output from the laser diode, to be the same as that of the voltage of the reference power control signal,
- wherein the reference laser power data comprises reference read power data that is set according to the write speeds in the write mode.
An apparatus generating reference laser power data for controlling laser power -in a disc drive, comprising:
- a photodetector which converts an optical signal output from a laser diode into an electrical signal in a read mode and a write mode according to write speeds;
- a sampling and holding unit which samples and holds the electrical signal output from the photodetector in a read power period;
- a subtracter that calculates voltage differences between read power sample and hold voltage output from the sampling hold unit in the read mode and sample and hold voltage in read power periods, according to the write speeds, in the write mode;
- an operation unit which generates reference laser power values corresponding to the voltage differences calculated by the subtracter, the reference laser power values reducing a variation in read power according to the write speeds in the write mode;
- and
- a memory unit to record information regarding the reference laser power values according to the write speeds.
A method of controlling laser power in a disc drive, comprising:
- generating reference laser power data compensating for a variation in laser diode driving voltage according to write speeds, and storing the reference laser power data in a memory unit;
- reading from the memory unit reference laser power data corresponding to the write speeds set in a write mode;
- and
- controlling the laser diode driving voltage so as to make the level of voltage corresponding to an optical signal output from laser diode of the disc drive be the same as that of voltage corresponding to the reference laser power data,
- wherein the reference laser power data comprises reference read power data according to the write speeds in the write mode.
A method of generating reference laser power data for controlling laser power -in a disc drive, comprising:
- detecting laser diode driving voltage in a read mode;
- detecting laser diode driving voltages in read power periods, according to write speeds, in a write mode;
- calculating voltage differences between the laser diode driving voltage in the read mode and the laser diode driving voltages in the read power periods, according to the write speeds, in the write mode;
- and
- generating reference laser power data reducing a variation in read power, according to the write speeds, to correspond to the voltage differences according to the write speeds.
A method of generating reference laser power data to reduce a variation in read power at a write speed, thereby controlling laser power in a disc drive, comprising:
- detecting a read voltage in a read period (Vrdc_rd);
- detecting a write voltage during the read period (Vrdc_wr);
- calculating a voltage difference ΔVrdc as Vrdc_rd-Vrdc_wr and
- generating and storing the reference laser power data according to:
- Vref_rd=Vref_rd(0)+αΔVrdc,
- wherein Vref_rd(0) is a reference power laser voltage in the read period and α is a proportional factor.
A method of generating laser power reference values for controlling laser power in a disc drive, comprising:
- performing a write operation;
- increasing a write speed from a minimum write speed to a maximum write speed during the write operation;
- detecting driving voltages as the write speed increases, including read driving voltages as the write speed increases;
- and
- storing the detected driving voltages at the increasing write speed as reference driving voltages.
A method of generating laser power reference values for controlling laser power in a disc drive, comprising:
- setting a write speed to a maximum write speed;
- calculating a voltage difference between the laser diode driving voltage in a read mode and the laser diode driving voltage in a read power period immediately after a transition from a write mode to the read mode;
- and
- determining and storing a reference read voltage for the set write speed based on the calculated voltage difference, without all stored reference read voltages being required to be identical for different write speeds.
A method of generating laser power reference values for controlling laser power in a disc drive, comprising:
- setting a write speed to a maximum write speed;
- calculating a voltage difference between the laser diode driving voltage in a read mode and the laser diode driving voltage in a read power period immediately after a transition from a write mode to the read mode for the generation of the laser cower reference values;
- and
- determining if the write speed is the maximum write speed,
- wherein the calculating comprises calculating the voltage difference if the write speed is the maximum write speed.
A method of controlling fluctuation in a laser diode driving voltage of a disc drive, comprising:
- automatically controlling a level of laser power in a write mode to prevent fluctuation of the laser diode driving voltage during a read power period according to write speeds of the disc drive, based on reference read values dependent on the write speeds.
Dependencies are inferred from the claim text.