# US 6,724,793 B2 · Laser diode drive circuit and amplifying circuit for optical disc recording and/or reproducing apparatus

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- Number: US 6,724,793 B2
- Document ID: US6724793B2
- Status: Granted
- Kind: B2
- Application number: 10/173,246
- Filed: 2002-06-18
- Published: 2003-01-02
- Granted: 2004-04-20
- Earliest claimed: 2001-06-19
- Assignees: Sony Corporation
- Inventors: Toru Nagara
- Web page: https://patentgrep.com/patent/US6724793B2

## CPC

- G11B 7/1263: Power control during transducing, e.g. by monitoring
- G11B 7/1275: Two or more lasers having different wavelengths
- H01S 5/042: Electrical excitation {; Circuits therefor (monolithically integrated laser drive components H01S5/0261)}
- H01S 5/40: Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30 (H01S5/50 takes precedence)
- G11B 2007/0006: {adapted for scanning different types of carrier, e.g. CD & DVD}
- H01S 5/0683: by monitoring the optical output parameters
- H01S 5/4087: {emitting more than one wavelength}
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL

## Abstract

A laser diode drive circuit for an optical disc recording and/or reproducing apparatus includes a plurality of laser diodes to output laser beams having different wavelengths, a switch circuit for selectively connecting a required laser diode from a plurality of laser diodes, a laser diode drive power supply circuit for driving the laser diode selectively connected by the switch circuit, a photodiode for detecting at least part of laser beams emitted from the laser diode to convert a detected part of laser beams into an electrical signal, a plurality of current-to-voltage conversion amplifiers connected to an output of the photodiode and whose conversion resistance values can be adjusted and having differently designed center conversion resistance values and an automatic power control circuit connected to outputs of the current-to-voltage conversion amplifiers to output a feedback signal to the laser diode drive power supply circuit. An amplifying circuit for such a laser diode drive power supply circuit, an optical disc recording and/or reproducing apparatus including such a laser diode drive circuit and a laser diode drive method for an optical disc recording and/or reproducing apparatus are also provided.

## Claims

### Claim 1

A laser diode drive circuit for an optical disc recording and/or reproducing apparatus, comprising:
a plurality of laser diodes for outputting laser beams having different wavelengths and different power output levels;
a laser diode drive power supply circuit;
a first switch circuit for selectively connecting a required laser diode from said plurality of laser diodes to said laser diode drive power supply circuit;
a photodiode for detecting at least part of laser beams emitted from said laser diode to convert a detected part of laser beams into an electrical signal;
a plurality of current-to-voltage conversion amplifiers connected to an output of said photodiode, being configured to adjust conversion resistance values and having different center conversion resistance values corresponding to respective said different power output levels of said plurality of laser diodes; and
an automatic power control circuit connected by way of a second switch to outputs of said current-to-voltage conversion amplifiers to output a feedback signal to said laser diode drive power supply circuit.

### Claim 2 (depends on 1)

The laser diode drive circuit for an optical disc recording and/or reproducing apparatus according to claim 1, wherein
said photodiode comprises a single diode, and
a plurality of switch circuits configured to selectively connect a required current-to-voltage conversion amplifier provided both between an output of said photodiode and inputs of said plurality of current-to-voltage conversion amplifiers, and between outputs of said plurality of current-to-voltage conversion amplifiers and an input of said automatic power control circuit.

### Claim 3 (depends on 1)

The laser diode drive circuit for an optical disc recording and/or reproducing apparatus according to claim 1, wherein
said photodiode comprises a plurality of diodes,
outputs of said respective diodes are connected to inputs of corresponding current-to-voltage conversion amplifiers of said plurality of current-to-voltage conversion amplifiers respectively, and
a plurality of switch circuits for selectively connecting required current-to-voltage conversion amplifiers are provided between outputs of said plurality of current-to-voltage conversion amplifiers and an input of said automatic power control circuit.

### Claim 4

An amplifying circuit comprising:
a plurality of current-to-voltage conversion amplifiers connected in parallel, being configured to adjust conversion resistance values and having different center conversion resistance values corresponding to respective different power output levels of a plurality of operably linked laser diodes; and
a plurality of change-over switches provided at the input sides and output sides of said plurality of current-to-voltage conversion amplifiers, whereby one amplifier is selectively connected under change-over control of said plurality of change-over switches.

### Claim 5

An optical disc recording and/or reproducing apparatus including a laser diode drive circuit, said laser diode drive circuit comprising:
a plurality of laser diodes for outputting laser beams having different wavelengths and different power output levels;
a laser diode drive power supply circuit;
a switch circuit for selectively connecting a required laser diode from said plurality of laser diodes to said laser diode drive power supply circuit;
a photodiode for detecting at least part of laser beams emitted from said laser diode to convert a detected part of laser beams into an electrical signal;
a plurality of current-to-voltage conversion amplifiers connected to an output of said photodiode, being configured to adjust conversion resistance values and having different center conversion resistance values corresponding to respective said different power output levels of said plurality of laser diodes; and
an automatic power control circuit connected by way of a second switch to outputs of said current-to-voltage conversion amplifiers to output a feedback signal to said laser diode drive power supply circuit.

### Claim 6

A laser diode drive method for an optical disc recording and/or reproducing apparatus, comprising:
selectively connecting a laser diode from a plurality of laser diodes having different output wavelengths and different power output levels to a laser diode drive power supply circuit with a first switch circuit;
driving said laser diode drive power supply circuit to allow the connected laser diode to emit laser beams;
detecting at least part of laser beams emitted from said laser diode to convert said detected part of laser beams into an electrical signal by a photodiode;
outputting said electrical signal to a corresponding current-to-voltage conversion amplifier of a plurality of current-to-voltage conversion amplifiers, the corresponding amplifier being configured to adjust conversion resistance values and having different center conversion resistance values corresponding to respective said different power output levels of said plurality of laser diodes, wherein said electrical signal is current-to-voltage-converted and is amplified;
selectively connecting an output of a required current-to-voltage conversion amplifier from said plurality of current-to-voltage conversion amplifiers to an automatic power control circuit with a second switch circuit;
generating a feedback signal from said electrical signal, which has been current-to-voltage-converted and amplified, by said automatic power control circuit; and
outputting said feedback signal to said laser diode drive power supply circuit to effect a closed loop control.