JP2000323783A - Laser power control circuit and drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable reduction of power loss by producing laser driving voltage by carrying out DC/DC convert to a power supply voltage based on a laser power detection signal of a laser light source and a reference signal which becomes a reference of laser power of a laser light source. SOLUTION: The differential between a reference signal SPWM and a detection signal SPD is compared to a saw-like wave and a switching signal as a PWM signal of the comparison results is produced. It is applied to a gate of an FET 43 through a resistor R15. A stable laser driving voltage VLD is produced from a power supply voltage + B since the FET 43 is controlled by such a PWM switching signal. Since a laser power control APC circuit 25 generates a laser driving voltage VLD directly from a power supply voltage + B of a power supply part 26 of a battery, etc., power loss depends on only efficiency of DC/DC convert operation in the APC circuit 25. Power loss can be reduced in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a laser power control circuit for driving a laser light source, and a drive device equipped with the laser power control circuit.

[0002]

2. Description of the Related Art Various optical recording media such as optical disks and magneto-optical disks and recording / reproducing devices (drive devices) corresponding thereto have been developed. In these drive devices, semiconductor lasers (laser diodes and the like) are used. Reading and writing of information are performed by irradiating the recording medium with laser light. Then, for example, a laser power control circuit (hereinafter, referred to as a laser power control circuit) that controls the light emission operation so that the laser diode emits laser light at a required level while supplying drive power to the laser diode.
APC circuit (called Automatic Power Control) is provided.

FIG. 4 shows an example of a conventional APC circuit. This A
The PC circuit includes a required part in the drive device (servo controller or system controller, etc.)
A reference signal of the laser output level is supplied as a PWM signal (pulse width modulation signal) SPWM, and a detection signal SPD by, for example, a photodetector for detecting the output level of the laser diode is supplied. The reference signal SPWM is
This signal specifies the laser output level of the laser diode. The detection signal SPD is a monitor signal of the current laser output level.

The reference signal SPWM is smoothed by a resistor R55 and a capacitor C52, and is input to an inverting input terminal of the differential amplifier 51 via a resistor R54. The detection signal SPD
Is input to the non-inverting input terminal of the differential amplifier 51. The resistors R51 and R52 and the capacitor C51 constitute a feedback system of the differential amplifier 51. And by this differential amplifier 51,
The difference between the reference signal SPWM and the detection signal SPD is output at a predetermined amplification factor. This differential output is applied to the base of the transistor Q31 via the resistor R53. An operating voltage Vcc output from a power supply circuit unit (DC / DC converter) provided in the drive device is supplied to the emitter of the transistor Q31 via a resistor R56. The operating voltage Vcc is obtained by, for example, stepping down or stepping up a power supply voltage + B of a battery mounted in the apparatus by a DC / DC conversion process.

In the transistor Q31, the operating voltage V
By controlling cc on the basis of the differential output, a drive voltage VLD of the laser diode is obtained and supplied to the laser diode.

According to such an APC circuit, the detection signal S
Since the drive voltage VLD is generated based on the difference between the PD and the reference signal SPWM (that is, the error from the reference value as the laser power), the output power of the laser diode is controlled to a predetermined level by a so-called feedback loop operation. Will be.

[0007]

However, such an A
The PC circuit has a problem that the power loss is large. That is, in the circuit of FIG. 4, a voltage drop of (Vcc-VLD) occurs in the system of the transistor Q31 and the resistor R56, but all of that is considered to be power loss. In addition, since the operating voltage Vcc itself is obtained by raising and lowering the battery voltage, power loss also occurs at that time, that is, double power loss occurs. For example, in the case of a dry battery or a portable drive device driven by a charge value, such power loss greatly affects the battery life, and is very undesirable.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an APC circuit capable of reducing a power loss in view of the above problems. Therefore, as a laser power control circuit, a laser drive voltage is generated by performing DC / DC conversion on a power supply voltage based on a laser power detection signal of a laser light source and a reference signal serving as a reference of the laser power of the laser light source. I do.

A drive device for performing a recording or reproducing operation by irradiating a recording medium with a laser beam from a laser light source supplies a laser driving voltage to the laser light source to execute a laser light emitting operation. A laser power control means for detecting the laser power output from the laser light source, a laser power detection means for supplying a laser power detection signal to the laser power control means, and a reference signal indicating the laser power to be output to the laser light source. Laser power setting means for supplying to the laser power control means, power supply means for generating a power supply voltage, and DC / DC conversion for the power supply voltage,
Power supply circuit means for obtaining a required operating voltage is provided, and the laser power control means performs DC / DC conversion on the power supply voltage based on the laser power detection signal and the reference signal to generate a laser drive voltage. To do.

That is, in the present invention, the laser power control circuit controls the DC voltage with respect to the power supply voltage of the power supply means such as a battery.
A laser drive voltage is generated by performing / DC conversion.

[0011]

Embodiments of the present invention will be described below. An example of a drive device according to this embodiment is a recording / reproducing device using a magneto-optical disk (mini disk) as a recording medium, and an example of a laser power control circuit is an APC circuit mounted on the recording / reproducing device. .

First, the configuration of a mini disc recording / reproducing apparatus will be described with reference to FIG. The disk 90 on which audio data is recorded is driven to rotate by the spindle motor 2. The disk 90 is irradiated with laser light by the optical head 3 during recording / reproduction.

The optical head 3 performs a high-level laser output for heating a recording track to the Curie temperature during recording, and a relatively low-level laser for detecting data from reflected light by a magnetic Kerr effect during reproduction. Perform output. For this reason, the optical head 3 has a laser diode 3b as a laser output means, an objective lens 3a as a laser output terminal, a photodetector 3c for detecting reflected light, and guides laser light / reflected light between these components. An optical system (not shown) such as a polarization beam splitter is mounted. A photodetector 3d for receiving a part of the laser beam from the laser diode 3b to obtain a detection signal of the laser output level is also provided. The objective lens 3a is held by the biaxial mechanism 4 so as to be displaceable in the radial direction of the disk and in the direction of coming into contact with and separating from the disk.

The optical head 3 with the disk 90 interposed therebetween
The magnetic head 6a is arranged at a position facing the above. The magnetic head 6a performs an operation of applying a magnetic field modulated by the supplied data to the disk 90. The entire optical head 3 and the magnetic head 6a can be moved in the disk radial direction by the thread mechanism 5.

The information detected from the disk 90 by the photodetector 3c in the optical head 3 by the reproducing operation is supplied to the RF amplifier 7. The RF amplifier 7 performs an arithmetic operation on the supplied information to reproduce the RF signal, the tracking error signal TE, the focus error signal FE, and groove information (absolute position information recorded as a pre-groove (wobbling groove) on the magneto-optical disk 90). G
FM and the like are extracted. The extracted reproduced RF signal is supplied to the encoder / decoder section 8. Further, the tracking error signal TE and the focus error signal FE are supplied to the servo circuit 9, and the groove information GFM is supplied to the address decoder 10.

The servo circuit 9 is provided with the supplied tracking error signal TE and focus error signal FE, and the system controller 1 constituted by a microcomputer.
Various servo drive signals are generated based on a track jump command, an access command, rotation speed detection information of the spindle motor 2 and the like from the controller 1 to control the two-axis mechanism 4 and the sled mechanism 5 to perform focus and tracking control. 2 is controlled to a constant linear velocity (CLV).

Further, under the control of the system controller 11, the servo circuit 9 supplies a reference signal SPWM for setting a laser power level to an APC circuit 25 described later.
Is supplied as a PWM signal. As the laser output level, a laser power at the time of reproduction and a laser power at the time of recording are respectively set.

The address decoder 10 decodes the supplied groove information GFM to extract address information.
This address information is supplied to the system controller 11 and used for various control operations. The reproduced RF signal is subjected to decoding processing such as EFM demodulation and CIRC in the encoder / decoder section 8. At this time, addresses, subcode data, and the like are also extracted and supplied to the system controller 11.

EFM demodulation in the encoder / decoder unit 8
The decoded audio data (sector data) such as CIRC is temporarily written into the buffer memory 13 by the memory controller 12. The reading of data from the disk 90 by the optical head 3 and the transfer of reproduced data in the system from the optical head 3 to the buffer memory 13 are at 1.41 Mbit / sec, and are usually performed intermittently.

Output from the encoder / decoder section 8
The data written in the buffer memory 13 is read at a timing when the transfer of the reproduction data becomes 0.3 Mbit / sec, and is supplied to the encoder / decoder unit 14. Then, a reproduction signal process such as a decoding process for the audio compression process is performed to obtain a digital audio signal of 44.1 KHZ sampling and 16-bit quantization.

The digital audio signal output from the encoder / decoder 14 is converted into an analog signal by the D / A converter 15, and the output processor 16 adjusts the level of the digital audio signal.
The impedance is adjusted and the like, and the analog audio signal Aout is output to an external device from the line output terminal 17 or supplied to the headphones connected to the terminal unit 27 as the headphone output HPout.

The digital audio signal decoded by the encoder / decoder section 14 is supplied to the digital interface section 22 so that the digital audio signal can be output from the digital output terminal 21 to an external device. . For example, it is output to an external device in the form of transmission by an optical cable.

When a recording operation is performed on the magneto-optical disk 90, the recording signal (analog audio signal Ain) supplied to the line input terminal 18 is converted into digital data by the A / D converter 19. Thereafter, the data is supplied to the encoder / decoder unit 14 and subjected to audio compression encoding processing. Or from a digital input terminal 20
Is supplied with the digital audio signal Din,
The digital interface unit 22 extracts control codes and the like, and the audio data is supplied to the encoder / decoder unit 14 and subjected to audio compression encoding processing. Although not shown, it is naturally possible to provide a microphone input terminal and use the microphone input as a recording signal.

The recording data compressed by the encoder / decoder section 14 is once written and stored in the buffer memory 13 by the memory controller 12, and then read out in units of a predetermined amount of data.
The data is sent to the decoder unit 8. After being subjected to encoding processing such as CIRC encoding and EFM modulation in the encoder / decoder section 8, it is supplied to the magnetic head drive circuit 6.

The magnetic head drive circuit 6 supplies a magnetic head drive signal to the magnetic head 6a according to the encoded recording data. That is, the magnetic head 6a applies an N or S magnetic field to the magneto-optical disk 90. At this time, the system controller 11 sends the AP signal via the servo circuit 9 based on the above-described reference signal SPWM.
The control circuit 25 controls the C circuit 25 to output a laser beam at a recording level.

The operation section 23 is provided with various operation keys for the user to instruct recording / reproducing / editing operations and the like. Specifically, play key, record key, stop key,
A record key, an AMS / search key, a pause key, an edit mode key, an edit operation key, and the like are provided, and an operator for inputting a disc title and a track name and other information are provided. Editing operations include track name input, disc name input, track division, track concatenation, track movement (change of track number as playback order), track erasure, and the like.
Operators necessary for instructing these editing operations are provided. Operation information from various operation keys and dials in the operation unit 23 is supplied to the system controller 11, and the system controller 11 executes operation control according to the operation information.

The display unit 24 is provided, for example, on a device housing.
1 is controlled. That is, the system controller 11
Transmits data to be displayed when the display operation is performed to the display driver in the display unit 24. The display driver drives a display such as a liquid crystal panel based on the supplied data, and executes display of required numbers, characters, symbols, and the like.

The system controller 11 is a microcomputer having a CPU, a program ROM, a work RAM, an interface, and the like, and controls the various operations described above.

The APC circuit 25 controls the laser diode 3b so that the laser output from the laser diode 3b is performed at the level specified on the basis of the reference signal SPWM.
Is supplied with a drive voltage VLD. In addition, the operation of generating the drive voltage VLD is performed using the detection signal SPD from the photodetector 3d so that the laser output level is stably performed at a predetermined level. A detailed configuration example will be described later.

The power supply section 26 is a battery such as a dry cell or a charged value, and supplies a power supply voltage + B. The power supply voltage + B is applied to a DC / DC converter 27 as a power supply circuit.
, The operating power supply Vcc required in the device is generated and supplied to each unit. However, the power supply voltage + B is supplied to the APC circuit 25 instead of the operating voltage Vcc.

FIG. 2 shows a circuit example of the DC / DC converter 27. The DC / DC converter 27 performs a DC / DC conversion operation on the power supply voltage + B in the system including the coil L1, the FET (switching element) 33, the diode D1, and the smoothing capacitor C2 based on the switching operation of the FET 33. Then, an operating voltage Vcc as a required voltage value is obtained. For example, an operating voltage Vcc of 2.4 V to 1.2 V is obtained from a power supply voltage of 1.2 V.

The switching signal applied to the gate of the FET 33 is generated by the differential amplifiers 31 and 32. A non-inverting input terminal of the differential amplifier 31 has a resistor R
3. The operating voltage Vcc divided by R4 is input. That is, the operating voltage Vcc is fed back. The reference voltage Vr is applied to the inverting input terminal of the differential amplifier 31.
ef is input. Note that resistors R1 and R2 and capacitor C
Reference numeral 1 denotes a feedback system of the differential amplifier 31.

The differential amplifier 31 detects the difference between the divided operating voltage Vcc and the reference voltage Vref, and supplies the difference to the inverting input terminal of the next stage differential amplifier 32. A sawtooth wave is supplied to the non-inverting input terminal of the differential amplifier 32 (operating as a comparator).
Therefore, the difference between the divided operating voltage Vcc and the reference voltage Vref and the difference between the sawtooth wave (comparison result) is PW
A switching signal as an M signal is generated, and a resistor R5
Is applied to the gate of the FET 33. By controlling the FET 33 by such a PWM switching signal, a stable operating voltage Vcc is generated from the power supply voltage + B.

Next, a circuit example of the APC circuit 25 is shown in FIG. As described above, this APC circuit 25 has a DC / DC
Instead of operating voltage Vcc generated by converter 27,
A power supply voltage + B is supplied from the power supply unit 26. Then, as shown in FIG. 3, the APC circuit 25 has a power supply voltage of + B
, Coil L11, FET (switching element)
43, a diode D11, and a smoothing capacitor C12.
The C / DC conversion operation is performed to obtain an operation voltage Vcc as a required voltage value. For example, a laser drive voltage VLD of about 1.2 V to 2.2 V from the power supply voltage is obtained. That is, similarly to the DC / DC converter 27, the DC / DC conversion operation for the power supply voltage + B is performed.

The switching signal applied to the gate of the FET 43 is generated by the differential amplifiers 41 and 42. The detection signal SPD from the photodetector 3d is input to the non-inverting input terminal of the differential amplifier 41. The above-described reference signal SPWM is smoothed by the low-pass filter including the resistor R13 and the capacitor C13 to the inverting input terminal of the differential amplifier 31, and is input to the inverting input terminal of the differential amplifier 41 via the resistor R14. Resistance R1
1, R12 and capacitor C11 constitute a feedback system of the differential amplifier 41.

Therefore, in the differential amplifier 41, the reference signal SPW
The difference between M and the detection signal SPD is detected, and the difference is supplied to the inverting input terminal of the differential amplifier 42 at the next stage. The differential amplifier 42 operates as a comparator,
A sawtooth wave is supplied to the non-inverting input terminal. Therefore, a difference between the reference signal SPWM and the detection signal SPD is compared with the sawtooth wave, and a switching signal is generated as a PWM signal as a result of the comparison. And FE via the resistor R1.
Applied to the gate of T43. By controlling the FET 43 by such a PWM switching signal, a stable laser drive voltage VLD is generated from the power supply voltage + B.

As described above, since the APC circuit 25 directly generates the laser drive voltage VLD from the power supply voltage + B of the power supply section 26 such as a battery, power loss is caused by this APC circuit.
This is only due to the efficiency of the DC / DC conversion operation in the circuit 25, and power loss can be reduced as compared with the conventional APC circuit configuration. Therefore, the recording / reproducing apparatus can also reduce the power loss and thereby prolong the battery life, and is particularly suitable as a portable recording / reproducing apparatus using a battery. However, it is needless to say that this embodiment can be applied to a recording / reproducing apparatus using a commercial AC power supply.

Specifically, when the conventional APC circuit described with reference to FIG. 4 is used, the power loss P1 is P1 = (Vcc × ILD × (1 / η−1)) + (Vcc−
VLD) × ILD [W]. Here, ILD is the current flowing through the laser diode, and η is the DC / DC conversion efficiency. On the other hand, when the APC circuit 25 of this example is used, the power loss P2
P2 = (VLD × ILD × (1 / η−1)) [W] It is understood from this equation that the reduction of the power loss of this example is effective. It can also be seen that the power consumption can be reduced as the voltage difference between the operating voltage Vcc and the laser drive voltage VLD increases.

Although the embodiment has been described above, the laser power control circuit according to the present invention employs the APC circuit 2
It is needless to say that the present invention is not limited to the configuration of FIG. 5 and various modified circuit examples are possible within the scope of the gist. The drive device of the present invention includes not only the above-described mini-disc recording / reproducing device but also a CD-type disc such as MD, CD (compact disc), CD-ROM, CD-R, and DVD (Digital Versatile Disc / Digital Video D
isc), a laser disk, an MO (magneto-optical disk), and other reproducing and recording devices corresponding to various optical recording media. That is, the present invention is useful as long as the drive device performs recording or reproduction by irradiating a laser beam with a laser light source.

[0040]

As described above, in the present invention, the laser power control circuit generates a laser drive voltage by performing DC / DC conversion on the power supply voltage based on the laser power detection signal and the reference signal. As a result, there is an effect that the power loss at the time of generating the laser drive voltage can be reduced, and thereby the effect of reducing the power loss as the drive device and prolonging the battery life can be obtained.

Further, a switching signal is generated from a difference signal between the laser power detection signal and the reference signal, and a switching element connected to a power supply voltage line is driven by the switching signal to perform DC / DC conversion. For example, the laser drive voltage (VLD) can be stably generated from the power supply voltage (+ B).

[Brief description of the drawings]

FIG. 1 is a block diagram of a recording and reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a DC / DC converter of the recording / reproducing apparatus according to the embodiment.

FIG. 3 is a circuit diagram of an APC circuit of the recording / reproducing apparatus according to the embodiment.

FIG. 4 is a circuit diagram of a conventional APC circuit.

[Explanation of symbols]

1 disk, 3 optical heads, 6a magnetic head, 8
Encoder / decoder section, 11 system controller, 11a RAM, 12 memory controller, 13
Buffer memory, 14 encoder / decoder units, 1
4a level meter section, 23 operation section, 24 display section,
25 APC circuit, 26 power supply, 27 DC / DC converter

Claims (3)

[Claims] 1. A laser power control circuit for supplying a laser drive voltage to a laser light source to execute a laser emission operation, comprising: a laser power detection signal of the laser light source; and a reference serving as a reference of the laser power of the laser light source. A laser power control circuit that performs DC / DC conversion on a power supply voltage based on a signal to generate the laser drive voltage. 2. A DC / DC conversion is performed by generating a switching signal from a difference signal between the laser power detection signal and the reference signal, and driving a switching element connected to a power supply voltage line by the switching signal. The laser power control circuit according to claim 1, wherein: 3. A drive device for performing a recording or reproducing operation by irradiating a recording medium with a laser beam from a laser light source, wherein a laser drive voltage is supplied to the laser light source to perform a laser light emitting operation. Laser power control means to be executed, detecting a laser power output from the laser light source,
A laser power detection unit for supplying a laser power detection signal to the laser power control unit; a laser power setting unit for supplying a reference signal indicating a laser power to be output to the laser light source to the laser power control unit; Power supply means for generating; and performing DC / DC conversion on the power supply voltage,
Power supply circuit means for obtaining a required operating voltage; and wherein the laser power control means performs DC / DC conversion on the power supply voltage based on the laser power detection signal and the reference signal, and outputs the laser drive voltage. A drive device characterized by generating: