JPH0610545Y2 - Rotation control circuit for disc player - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a rotation control circuit for a spindle motor used in a disc reproducing apparatus.

(B) Prior art In a disc reproducing apparatus that optically reproduces information recorded on the disc surface, the disc is rotated by a spindle motor, and a light beam emitted from an optical pickup is irradiated onto the disc, The optical pickup detects the EFM signal of the light beam reflected in accordance with the EFM signal recorded on the digital signal, AD-converts the detected EFM signal, and digital-processes the digital-signal-processed signal. The original information signal is being reproduced. In such a disc reproducing apparatus, a CD player or the like is designed so that a light beam emitted from an optical pickup tracks a track of the disc at a constant linear velocity. As a method for keeping the linear velocity constant, as described in JP-A-60-85465, EFM is used.
The spindle motor is controlled by comparing the EFM symbol signal / EFM signal in the signal with the internal synchronizing signal.

(C) Problems to be solved by the invention As described above, in order to make the linear velocity constant in the disc reproducing apparatus, the EFM symbol signal / EFM signal in the EFM signal is compared with the internal synchronization signal, and the line at that time is compared. A drive signal having a pulse width corresponding to the speed is applied to the spindle motor so that the light beam irradiates the track of the disk at a constant linear velocity.

By the way, recently, in the same disc reproducing apparatus, a disc which is capable of reproducing a conventional 12 cm diameter CD disc and an 8 cm diameter single CD disc is being commercialized. When playing discs with different diameters with the same spindle motor as above, the inertia during rotation varies greatly due to the difference in the weight of the discs. If the spindle motor is added as it is when reproducing a single CD disc, the phase margin becomes small and the servo system becomes unstable.

The present invention eliminates such drawbacks and provides a rotation control circuit of a spindle motor in which the gain of the rotation control circuit is made different according to the type of the diameter of the disc to be reproduced.

(D) Means for solving the problem The rotation control circuit of the disc reproducing apparatus of the present invention is applied to the diameter detecting device for detecting the diameter of the disc and the spindle motor so as to irradiate the light beam at a constant linear velocity. The rotation control circuit controls the drive signal, and the switching circuit switches the gain of the rotation control circuit according to the detection signal from the diameter detecting device.

(E) Action Since the rotation control circuit of the disc reproducing apparatus of the present invention is configured as described above, the diameter detecting device detects the type of the diameter of the disc to be reproduced and switches the switching circuit to change the gain of the rotation control circuit. Make it appropriate for the diameter of the disc to be played.

(F) Embodiment An embodiment of the rotation control circuit of the disc reproducing apparatus of the present invention will be described with reference to the drawings.

(1) is a turntable rotated by a spindle motor (2), on which a CD disk (3) with a diameter of 12 cm or a single CD disk (4) with a diameter of 8 cm is placed. (5) is a motor drive circuit for supplying a drive current to the spindle motor (2),
(6) is an optical pickup, C on the turntable (1)
A light beam is emitted to the D disk (3), and the reflected light beam is detected by emitting the light beam to the CD disk (3) to extract an electric signal. (7) is an analog signal shaping circuit for converting an analog electric signal extracted from the optical pickup (6) into a parallel digital signal,
(8) is a microprocessor for processing the parallel digital signal, which comprises a digital signal processing circuit for processing the digital signal and obtaining left and right audio signals, a rotation control circuit, a diameter detecting section and the like. (9) is a motor drive circuit (5) for applying positive and negative motor drive pulses (DM +, DM-) obtained from the rotation control circuit of the microprocessor (8).
In the supply path to supply to the bleeder resistance (10) (11) (12) (13) for bleeding with the motor drive pulse, and the switching transistor (14) (15) in the one bleeder resistance (11) (13)
And division resistors (16) and (17) connected in parallel with each other. (1
Reference numeral 8) is a switching circuit which is operated by a detection signal from the diameter detecting portion of the microprocessor (8) and turns on or off the switching transistors (14) and (15).

Next, the operation of the rotation control circuit of the disc reproducing apparatus of the present invention will be described.

First, the case of reproducing a CD disc (3) having a diameter of 12 cm will be described. Now turntable (1) to CD disc (3)
And place the power switch to turn on the optical pickup.
Although (6) moves from the outer diameter to the inner diameter, the optical pickup (6) performs a focus search when the CD disc (3) is moved to the outermost track position. In this state, turntable (1) has a CD disk (3) with a diameter of 12 cm.
When is mounted, the light beam emitted from the optical pickup (6) is reflected by the surface of the CD disc (3), and the reflected light beam reflected is received by the optical pickup (6) and is detected by the photodetector. The applied focus error signal is detected by the astigmatism means, the focus error signal is applied to the coil, and the objective lens is moved up and down to perform focus search. When a focus search is performed and a focus is achieved, a signal is obtained from the photodetector, applied to the analog signal shaping circuit (7), converted into a digital signal, and supplied to the microprocessor (8) to detect the diameter of the microprocessor (8). 1 from the circuit
A detection signal indicating that the diameter is 2 cm is generated. When the detection signal is applied to the switching circuit (18), a negative signal is generated from the switching circuit (18) to turn off the switching transistors (14) and (15). Therefore, the signal of the supply path (9) is the bleeder resistance (10) (11).
Only (12) and (13) will be breeders.

Next, select a song and turn on the play button.
(6) is moved to the innermost track and reads the TOC (Table of Contents) recorded on the lead-in track on the innermost track, and then picks up the selected track.
(6) is moved, and the light beam emitted from the optical pickup (6) is irradiated again to the CD disk (3) to read the information recorded on the track of the CD disk (3). The information is modulated into an EFM signal and recorded in pits and lands, and the information includes a frame synchronization signal indicating the beginning of each frame. The light beam emitted from the optical pickup (6) and applied to the CD disc (3) is reflected according to the bits and lands recorded on the tracks of the CD disc (3) and is received by the optical pickup (6) again. The photodetector extracts the original EFM signal, and the analog signal shaping circuit (7) converts it into a parallel digital signal. The digital signal is digitally processed by the microprocessor (8) and separated into left and right signals, which are DA converted into voice signals. By the way, during playback, an optical pickup (6)
The light beam emitted from the CD disk (3) is required to track the track at a constant linear velocity.
The spindle motor (2) must be controlled as such.

Therefore, the EF added to the analog signal shaping circuit (7)
A frame sync signal is taken out of the M signal, compared with an internal sync signal oscillated by the reference signal oscillator (20) in the microprocessor (8), and a drive signal is obtained from the rotation control circuit of the microprocessor (8). This drive signal generates a positive drive pulse DM + having a pulse width corresponding to the tracking speed of the light beam when the tracking speed is slower than the predetermined linear speed, and when the tracking speed is faster than the specified linear speed, the speed is increased. A negative drive pulse DM- having a pulse width corresponding to The drive pulse is supplied to the bleeder resistor (1
It is divided by 0) (11) (12) (13) and supplied to the motor drive circuit (5). The motor drive circuit (5) generates a DC drive current according to the pulse width of the drive pulse,
It is supplied to (2) and the rotation of the spindle motor (2) is controlled to track the light beam at the specified linear velocity.

Next, the case of reproducing the single CD disc (4) will be described.

When the single CD disc (4) is placed on the turntable (1) and the power switch is turned on, the optical pickup (6) moves in the inner circumferential direction and moves to the outermost track of the above-mentioned 12 cm diameter CD disc (3). When the position to respond is reached, focus search is performed. However, since there is no single CD disc (4) at this position, the light beam emitted from the optical pickup (6) is not reflected and is not focused. Therefore, no signal is detected by the optical pickup (6) and a detection signal indicating that the disc is a single CD disc (4) is generated by the diameter detecting means of the microprocessor (8) and is supplied to the switching circuit (18).
As a result, a positive signal is generated from the switching circuit (18) and the switching transistors (14) and (15) are turned on.
Dividing resistors (16) and (17) are connected in parallel to (11) and (13).

Then, similar to the above, when the play button is operated, the light beam emitted from the optical pickup (6) irradiates the tracks on the single CD disc (4), and the EFM is performed in the same manner as described above.
Signal detection and EFM signal analog signal shaping circuit (7)
Is converted into a digital signal by, and the microprocessor (8) performs digital processing such as error correction to obtain left and right signals. The left and right audio signals are extracted by performing DA conversion on the left and right signals.

The rotation control circuit of the microprocessor (8) compares the frame sync signal extracted from the EFM signal with the internal sync signal in the same manner as described above to obtain a drive signal. The drive signal is supplied to the motor drive circuit (5) via the supply path (9), and after being converted into a DC drive current, drives the spindle motor (2) to rotate the turntable (1). By the way, when the drive signal obtained by the rotation control circuit is supplied to the motor drive circuit (5) in the supply path (9) with the same voltage division ratio as described above,
In this case, since the single CD disk (4) to be driven is small in both weight and diameter and has small inertia, the rotation speed of the spindle motor (2) rapidly increases or decreases and the rotation becomes unstable. Therefore, as mentioned above, switching transistors
By turning on (14) (15), the bleeder resistance (11) (13)
The dividing resistors (16) and (17) are connected in parallel, and the level of the drive signal from the rotation control circuit of the microprocessor (8) that is divided and supplied to the motor drive circuit (5) is lowered. As described above, the spindle motor (2) is prevented from being excessively controlled and unstable in rotation.

In the above, the detection of the disc diameter whether the disc to be reproduced has a diameter of 12 cm or a diameter of 8 cm is detected in the range outside the outermost periphery of the single CD disc having a diameter of 8 cm and inside the outermost periphery of the CD disc having a diameter of 12 cm. The focus search operation is performed depending on whether or not the reflected light from the disc is obtained from the optical pickup. Therefore, it is not necessary to provide a dedicated detection element for detecting the disc diameter.

(G) Effect of the Invention As described above, the rotation control circuit of the disc reproducing apparatus of the present invention operates the switching circuit according to the diameter of the disc to be reproduced and switches the gain of the rotation control circuit. Optimal rotation control can be performed for each disc, and in particular, the diameter of the disc to be reproduced is detected by the focus search operation outside the outermost circumference of the small diameter disc and inside the outermost circumference of the large diameter disc. Therefore, it is not necessary to provide a dedicated detection element for detecting the disk diameter, the configuration can be simplified, and the cost is advantageous.

[Brief description of drawings]

The figure is a rotation control circuit diagram of the disk reproducing apparatus of the present invention. (2) …… Spindle motor, (3) …… 12cm diameter CD disc, (4) …… Single CD disc, (5) …… Motor drive circuit, (6) …… Optical pickup, (9) …… Supply path, (10)
(11) (12) (13) …… Bleeder resistance, (14) (15) …… Switching transistor, (16) (17) …… Bleeder resistance, (18)…
... Switching circuit.

Claims (1)

[Scope of utility model registration request] 1. A disc rotated by a spindle motor is irradiated with a light beam from an optical pickup to reproduce the disc, and at least two discs having different diameters, a large diameter and a small diameter, are used as the reproducing disc. The optical disc pickup apparatus includes a rotation control circuit for generating a drive signal for controlling the rotation of the spindle motor, and a switching circuit for switching the level of the drive signal obtained from the rotation control circuit. When the focus search operation for obtaining the in-focus point of the light beam from the disk is performed outside the outermost circumference of the small-diameter disk and inside the outermost circumference of the large-diameter disk, the in-focus point with the disk is obtained. When it is judged that the playback disc has a large diameter, and the focus point with the disc cannot be obtained, the playback disc Determining that small diameter, the rotation control circuit of the disk reproducing apparatus is characterized in that so as to switch the switching circuit according to the determination.