JP2501405Y2 - Laser drive circuit of optical disk reproducing device - Google Patents

Description

[Detailed description of the device]

[Industrial applications]

The present invention relates to a laser drive circuit of an optical disk reproducing device, and more particularly to optimizing a drive voltage of a laser diode.

[Prior art]

The optical disc reproducing device reproduces various signals such as images and music recorded on an optical disc such as a compact disc (CD) by irradiating the optical disc with laser light and reflecting the same, and drives a laser diode. A laser driving circuit for generating laser light is installed. As shown in FIG. 2, this laser drive circuit sends a drive current to the laser diode 2 through the drive transistor 4 and irradiates the laser light 6 generated by the laser diode 2 toward an optical disk (not shown). The light-receiving diode 8 receives the light-received output through the amplifier 10 to the base of the drive transistor 4 to control the drive current of the laser diode 2. The power supply voltage Vcc is applied to the anode of the laser diode 2 as a drive voltage via the drive transistor 4.

[Problems to be solved by the device]

By the way, in the optical disc reproducing apparatus, a mechanical driving unit such as a motor for rotating the optical disc requires a driving voltage of 5 to 12 V, and therefore the power supply voltage Vcc in such a laser driving circuit is also a driving voltage of 5 to 12 V. It is common. Normally, the forward voltage drop V _F of a laser diode is 1.8 V
However, if a voltage higher than that is used as the driving voltage, a voltage exceeding 1.8V becomes a reactive voltage, and therefore the power consumption of the driving transistor 4 increases and the driving efficiency decreases. It has the drawback of coming. Therefore, it is an object of the present invention to provide a laser drive circuit for an optical disk reproducing apparatus, which improves drive efficiency by optimizing the drive voltage of the laser diode without changing the value of the power supply voltage Vcc.

[Means for Solving the Problems]

As shown in FIG. 1, the laser drive circuit of the optical disk reproducing apparatus of the present invention is provided with a servo system circuit such as a focus servo or a tracking servo, and a drive current is supplied from the transistor (drive transistor 4) to the laser diode 2. , Laser diode 2
Is a laser drive circuit of an optical disk reproducing apparatus for controlling the drive current of the laser diode by receiving the laser light 6 generated by the light receiving diode 8 and feeding back the received light output to the base of the transistor through an amplifier 10. A DC-DC converter 12 that receives a clock signal CLK common to the circuit 14 and switches is provided, and by applying the voltage obtained by the DC-DC converter 12 to the transistor as a drive voltage V _D , the laser is passed through the transistor. A drive current is passed through the diode.

[Action]

In the laser drive circuit of the optical disk reproducing apparatus of the present invention, the power supply voltage Vcc is converted into the drive voltage V _D suitable for driving the laser diode 2 by using the DC-DC converter (DC-DC converter 12), and the drive voltage is converted. Laser diode 2 through V _D transistor (driving transistor 4)
In addition, the reactive voltage is reduced by directly applying the power supply voltage Vcc.

【Example】

FIG. 1 shows an embodiment of a laser drive circuit of the optical disk reproducing apparatus of the present invention. In this laser drive circuit, a drive current is applied to the laser diode 2 through the drive transistor 4 to irradiate the optical disk (not shown) with the laser light 6 generated by the laser diode 2, and the light receiving diode 8 receives the laser light 6. Controlling the drive current of the laser diode 2 by feeding back the received light output to the base of the drive transistor 4 through the amplifier 10 is similar to the laser drive circuit shown in FIG. This laser drive circuit is equipped with a DC-DC converter (DC / DC) 12 as a DC-DC converter that converts the power supply voltage Vcc into a voltage suitable for driving the laser diode 2, and is obtained by this DC / DC12. A proper driving voltage V _D is applied to the laser diode 2 through the driving transistor 4. The DC / DC 12 operates, for example, a switching element with a clock signal to intermittently switch the power supply voltage Vcc, convert the voltage, and then rectify it to obtain an appropriate voltage V _D.
Is a DC voltage conversion circuit for obtaining Therefore, the DC / DC 12 shares an oscillator (OSC) 16 that supplies the clock signal CLK to the servo system circuit 14 in the optical disc reproducing apparatus, and uses the clock signal CLK obtained by the oscillator 16 as a switching signal. Therefore, the circuit configuration is simplified. The servo system circuit 14 in the optical disc reproducing apparatus includes a constant linear velocity servo that synchronizes with the linear velocity of the optical disc that is the recording medium, a focus servo that matches the focus of the optical system to the pits of the optical disc to read the pits of the optical disc, There are tracking servos for tracking tracks. As the oscillator 16, a highly accurate oscillator using an oscillating element such as a crystal oscillator 18 is used. Therefore, in such a laser drive circuit, while the power supply voltage Vcc is shared with the servo system circuit 14 and other drive circuits, the DC / DC 12 is used to form an appropriate drive voltage V _D. The driving efficiency of can be improved. When the clock signal CLK is shared in this way, in the optical disk playback device, there is no beat failure with the audio signal, so there is no deterioration in sound quality, and the synchronization status of the phase-locked loop that plays back the pit clock does not occur. Do not disturb.

[Effect of device]

As described above, according to the present invention, the DC-D that switches using the clock signal common to the servo system circuit is used.
Since the voltage obtained by the C converter is converted to an appropriate drive voltage to drive the laser diode, the power supply voltage can be shared with the servo system circuit, and the reactive voltage can be reduced to improve drive efficiency and beat failure. Therefore, it is possible to obtain effects such as not disturbing the synchronization state of the phase locked loop.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a laser drive circuit of an optical disc reproducing apparatus of the present invention, and FIG. 2 is a circuit diagram showing a laser drive circuit of a conventional optical disc reproducing apparatus. 2 …… Laser diode 4 …… Drive transistor 8 …… Light receiving diode 10 …… Amplifier 12 …… DC-DC converter 14 …… Servo system circuit 16 …… Oscillator CLK …… Clock signal

Claims (1)

(57) [Scope of utility model registration request] 1. A servo system circuit such as a focus servo or tracking servo is provided, a drive current is made to flow from a transistor to a laser diode, a laser light generated by the laser diode is received by a light receiving diode, and the light reception output thereof is the base of the transistor. Is a laser drive circuit of an optical disk reproducing device for controlling a drive current of a laser diode by feeding back to an amplifier through a DC-DC converter that receives a clock signal common to the servo system circuit and performs switching. A laser drive circuit for an optical disk reproducing apparatus, wherein a drive current is supplied to the laser diode through the transistor by applying a voltage obtained by a converter as a drive voltage to the transistor.