Power control apparatus and method for an optical drive

Abstract

A power control apparatus and method for an optical drive is disclosed. The power control apparatus estimates the temperature rising effect of a laser diode and performs a partial open-loop power control, achieving accurate write power control. Therefore, regarding to a high-speed, high-density optical disk recording medium combined with multi-pulse write waveforms, the invention can also achieve accurate write power control even though the response speed of a front photodiode is much slower than the modulation speed of recording pulses of the laser diode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 shows a relation between the laser power and the driving current.

FIG. 2 is a block diagram illustrating a conventional optical drive.

FIG. 3 illustrates a peak envelope waveform during changes in write strategy.

FIG. 4 shows a relation of each signal inside the multi-pulse peak-hold device while a relatively low-speed front photodiode is being used.

FIG. 5 is a block diagram of another conventional optical drive.

FIG. 6A shows a relation among a laser power level, a driving current and a pseudo power level P_v.

FIG. 6B shows a relation among a laser power level, a driving voltage and a pseudo power level P_v.

FIG. 7 is a block diagram of an optical drive according to the invention.

FIG. 8 is a flow chart illustrating a power control method according to a first embodiment of the invention.

FIG. 9 is a flow chart illustrating a power control method according to a second embodiment of the invention while the optical drive is accessing a rewritable disk.

Claims

1. A power control apparatus for an optical drive, comprising: a sample and hold circuit, for receiving a sample hold control signal and an optical power signal to generate a measured voltage signal;a closed-loop automatic power controller, for receiving the measured voltage signal and a closed-loop power command to generate a closed-loop driving voltage correspondingly;a command generator, for receiving the closed-loop driving voltage, performing temperature compensation and generating a write power command and the closed-loop power command;an open-loop power controller, for receiving the write power command and generating a write driving voltage;a laser diode driver, for receiving at least one encoded signal, the closed-loop driving voltage and the write driving voltage to generate a laser diode driven signal;a laser diode, for receiving the laser diode driven signal and radiating laser light onto an optical disk; andan optical power detection unit, for detecting a laser power of the laser diode and generating the optical power signal.

2. The apparatus according to claim 1, further comprising: an encoder, for receiving a plurality of recording data and generating the encoded signal and the sample hold control signal.

3. The apparatus according to claim 1, wherein the laser power detection unit comprises: a photodiode, for detecting laser power of the laser diode and generating an optical power current signal; anda current voltage converter, for receiving the optical power current signal and converting the optical power current signal into the optical power signal.

4. The apparatus according to claim 1, wherein the command generator comprises: a write command compensation unit, for receiving the closed-loop driving voltage, performing temperature compensation processing and generating a compensated value; anda power command output unit, for generating the write power command and the closed-loop power command according to the compensated value.

5. The apparatus according to claim 1, wherein the optical drive is a rewritable optical drive, and the closed-loop driving voltage comprises a bias driving voltage and an erase driving voltage.

6. The apparatus according to claim 1, wherein the closed-loop driving voltage comprises a bias driving voltage and an erase driving voltage.

7. A power control method for an optical drive, comprising the steps of: generating a power reference value at a first temperature according to a low power driving signal which drives a laser diode to operate at a low power level value and a high power driving signal which drives the laser diode to operate at a high power level value;controlling the low power driving signal in a closed-loop control mode; andgenerating the high power driving signal according to the low power driving signal, the low power level value, the power reference value and the high power level value.

8. The method according to claim 7, wherein the first temperature is an initial temperature of the optical drive.

9. The method according to claim 8, wherein the step of generating the power reference value comprises: generating a first linear equation of the low power level, the high power level, the low driving signal and the high driving signal according to the low power level value, the low power driving signal value, the high power level value and the high power driving signal value; andcalculating a power level value as the power reference value while the driving signal value is equal to zero according to the first linear equation.

10. The method according to claim 7, wherein the low power driving signal is a bias driving voltage.

11. The method according to claim 10, wherein the step of controlling the low power driving signal further comprises: controlling an erase driving voltage in the closed-loop control mode.

12. The method according to claim 7, wherein the low power driving signal is an erase driving voltage.

13. The method according to claim 12, wherein the step of controlling the low power driving signal further comprises: controlling a bias driving voltage in the closed-loop control mode.

14. The method according to claim 7, wherein the step of generating the high power driving signal comprises: sampling the low power driving signal as a low power sample driving signal;generating a second linear equation of the low power level, the high power level, the low driving signal and the high driving signal at a second temperature according to the power reference value, the low power sample driving signal and the low power level value; andcalculating a driving signal value as the high power driving voltage by plugging the high power level value into the second linear equation.

15. The method according to claim 14, wherein the high power driving signal is a write driving voltage.