Optical disk recording/reproducing apparatus and its disk rotary driving apparatus

Abstract: A disk rotary driving apparatus in an optical disk reproducing apparatus capable of reproducing disks having different sizes includes a spindle motor(3) for rotationally driving a disk(2), a servo unit (4,6,7,18) for controlling rotation of the spindle motor, and a control unit(15) for detecting an activation response state of the spindle motor (3) upon starting, and switching a gain of the servo unit on the basis of the detection result.

Description: The present invention relates to a disk rotary driving apparatus according to the preambles of claims 1 or 2, in, e.g., an optical disk reproducing apparatus and, more particularly, to a disk rotary driving apparatus in an optical disk reproducing apparatus for a compact disk player or the like, capable of reproducing a plurality of types of disks having different sizes. In a conventional disk rotary driving apparatus of a reproduction-only optical disk reproducing apparatus such as a CD-ROM disk player or a compact disk player, rotation of a spindle motor is phase-controlled on the basis of a phase comparison signal between a clock signal separated from a reproduction signal obtained by an optical pickup and a predetermined reference signal. In this manner, in a compact disk player, a spindle motor and its driver constitute a PLL (phase locked loop) circuit as a whole, thereby rotationally driving a compact disk with high precision. An optical disk such as a compact disk has various diameter sizes, e.g., a compact disk has two diameters 8 cm and 12 cm. Therefore, in a spindle motor of a compact disk player, the weight of an object to be rotationally driven as a load on the spindle motor changes in accordance with whether a compact disk having a diameter of 8 cm or 12 cm is to be driven. Therefore, in a compact disk player capable of reproducing two types of compact disks having diameters of 8 cm and 12 cm, a servo gain of a PLL circuit must be automatically switched in accordance with the type of a loaded compact disk. Therefore, various detecting methods are used to detect the disk size of the loaded compact disk. In a first detecting method, a photoreflector is arranged at a predetermined position of an optical disk reproducing apparatus. The diameter of a loaded optical disk is discriminated in accordance with the presence/absence of light reflected by the optical disk. In this manner, the disk size is detected. In a second method, a photointerruptor, instead of a photoreflector, is arranged at a predetermined position in an optical disk reproducing apparatus. As in the first method, the size of a loaded optical disk is detected in accordance with whether light from the photointerruptor is interrupted by the optical disk. In a third detecting method, mechanical contacts are arranged at a predetermined position in an optical disk reproducing apparatus. As in the first and second methods, the type of an optical disk is detected in accordance with ON/OFF of the contacts. In a fourth detecting method, a reproduction light beam is radiated from an optical pickup of an optical disk reproducing apparatus onto a loaded optical disk. The optical pickup detects the presence/absence of a reflected light beam, thereby detecting the type of the loaded optical disk as in the above methods. Therefore, one of the first to fourth detecting methods is selected upon designing of an optical disk player. The servo gain of a PLL circuit of a spindle motor is switched on the basis of a detection result obtained by the selected method. In the first to third detecting methods, however, an exclusive detecting mechanism must be provided to detect the disk size of a loaded optical disk. Therefore, an arrangement of an optical disk reproducing apparatus such as a compact disk player is complicated. In addition, in order to reproduce an 8-cm size compact disk in a compact disk player capable of reproducing only a 12-cm size compact disk, an 8-cm size compact disk with an adaptor, consisting of a synthetic resin or the like, mounted on its outer circumference surface is sometimes rotationally driven. In this case, since an 8-cm size compact disk with an adaptor mounted on its outer circumference is rotationally driven, a spindle motor of a compact disk player must be phase-controlled with a servo gain similar to that used to rotationally drive a 12-cm compact disk. Since, however, the adaptor is not formed to reflect light, a loaded compact disk is detected as an 8-cm compact disk in the above first and fourth detecting methods. Therefore, a spindle motor is phase-controlled with a servo gain for driving an 8-cm compact disk, resulting in an insufficient servo gain. In addition, some compact disks have a transparent outer circumference. In this case, in the first, second, and fourth detecting methods, an 8-cm compact disk may be erroneously detected although a 12-cm compact disk is loaded. In order to avoid an erroneous detection of CD's of different size placed on a turntable for rotational driving by a spindle motor, a servo loop for controlling the rotation of said spindle motor and a control circuit are known (JP-A-61 293 183 and US-A-4 653 040) for detecting, on the basis of different inertias of the CD's of different size, an activation response state of said spindle motor upon starting based on a voltage proportional to the rotation of the spindle motor when a predetermined period of time has ellapsed after said spindle motor has been energized by an activating signal and for switching the gain of the servo loop as a response of the detection result. It is an object of the invention to offer a more simple and more reliable servo loop and control circuit for a disk driving motor which moreover can be realized as an integrated circuit. In order to solve the above problems realized with the state of the art, according to the present invention, a disk rotary driving apparatus is provided with the features according to claims 1 or 2 in two alternative technical solutions. The invention and advantageous effects thereof are described in the following with reference to the accompanying drawings in which: Fig. 1 is a block diagram showing a compact disk player according to an embodiment of the present invention; Figs. 2A to 2B2 are timing charts showing signal waveforms for explaining an operation of the embodiment shown in Fig. 1; Fig. 3 is a block diagram showing a controller according to the second embodiment; and Figs. 4A to 4B2 are timing charts showing signal waveforms for explaining an operation of the second embodiment shown in Fig. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a disk rotary driving apparatus of the present invention is applied to a compact disk player as an optical disk reproducing apparatus will be described below with reference to the accompanying drawings. Referring to Fig. 1, reference numeral 1 denotes an overall arrangement of a compact disk player. In the compact disk player 1, a compact disk 2 is rotationally driven by a spindle motor (M) 3. Although not shown, information recorded in the compact disk 2 is read by an optical pickup unit provided in a main body of the disk player 1 so as to move along the radial direction of the disk. Reference numeral 4 denotes a frequency generator (FG) for outputting a rotational speed detection signal S F having a frequency increasing in proportion to the rotational speed of the spindle motor 3. Reference numeral 6 denotes a frequency/voltage converter (FVC) for converting the rotational speed detection signal S F from the frequency generator 4 into a voltage and outputting an output signal S V having a voltage changing in proportion to the rotational speed of the compact disk 2. Reference numeral 8 denotes an operational amplifier; 9, a feedback resistor; and 11 and 13, input resistors. The operational amplifier 8, the feedback resistor 9, and the input resistors 11 and 13 constitute a differential amplifier 7. The operational amplifier 8 receives at its inverting input terminal the output signal S V from the frequency/voltage converter 6 and receives at its non-inverting input terminal an activation signal S ST from a controller 15 (to be described later). The operational amplifier 8 outputs an error signal S ER of the output signal S V from the frequency/voltage converter 6 with respect to the activation signal S ST . The error signal S ER is supplied to an amplifier (AMP) 18. Reference numeral 19 denotes a driver (DRIV) for driving the spindle motor 3 on the basis of the error signal S ER amplified by the amplifier 18. With this arrangement, the spindle motor 3, the frequency generator 4, the frequency/voltage converter 6, the operational amplifier 8, the amplifier 18 and the driver 19 constitute a servo loop. The spindle motor 3, therefore, is activated such that the output signal S V follows the activation signals S ST . As shown in Fig. 1 and with reference to Figs. 2A to 2B2, the controller 15 comprises: a switch circuit 22 to be switched on the basis of a control signal S C when a reproduction operation member is operated; an analog/digital converter (ADC) 23 for converting the output signal S V from the frequency/voltage converter 6 into a digital signal; a first comparator (COM1) 24 for comparing the output signal S V converted into a digital signal by the A/D converter 23 with predetermined reference data D REF1 and raising the signal level of an output signal S E when the output signal S V rises higher than a voltage determined by the reference data D REF1 ; a timer circuit (TIM1) 26 to be reset at the same time as the switch circuit 22 is switched on at a timing t₀ by the control signal S C as in the switch circuit 22 and counting a predetermined clock signal during a feedback period from the reset timing t₀ to a timing t₁₁ or t₁₂ at which the signal level of the output signal S E rises; and a second comparator (COM2) 28 for fetching the count of the timer circuit 26 when the signal level of the output signal S E rises and comparing the count with predetermined reference data D REF2 . When an 8-cm compact disk body alone is to be driven, a small count is obtained from the timer circuit 26. When a 12-cm compact disk or an 8-cm compact disk with an adaptor is to be driven, a large count is obtained from the timer circuit 26. When a 12-cm compact disk or an 8-cm compact disk with an adaptor is to be driven, the comparator 28 raises a switch signal S GAIN of a servo gain. In this embodiment having the above arrangement, the spindle motor 3 is activated to follow the rise in the activation signal S ST . The rotational speed of an output shaft of the spindle motor 3 is gradually increased. As described above, the activation response state of the spindle motor 3 changes in accordance with the weight of the compact disk 2 to be rotationally driven by the spindle motor 3. That is, when a 12-cm compact disk or an 8-cm compact disk fixed to an adaptor is to be driven, an object to be rotationally driven is heavier than that when an 8-cm compact disk body alone is to be driven. For this reason, increase of the rotational speed of the output shaft of the spindle motor 3 is delayed. When an 8-cm compact disk body alone is to be driven, therefore, the output signal S V rises to a predetermined voltage within a short time period as shown in Fig. 2B1. When a 12-cm compact disk or an 8-cm compact disk fixed to an adaptor is to be driven, however, the rise in the output singal S V is delayed as shown in Fig. 2B2. In this embodiment, therefore, a time period required for the output signal S V to rise to a predetermined voltage is detected to detect the activation response state of the spindle motor 3, thereby switching the servo gain on the basis of the detection result. That is, the controller 15 converts the output signal S V into a digital signal in the A/D converter 23 and supplies the converted output signal S V to the first comparator 24, compares the output signal S V with the reference data D REF1 in the first comparator 24, and outputs the output signal S E indicating that the output signal S V exceeds the voltage determined by the reference data D REF1 . At the same time, the controller 15 counts a predetermined clock signal S CK for a time period from a timing t₁₁ to a timing t₁₂ at which the output signal S E rises in the timer circuit 26, and compares the count with the predetermined reference data D REF2 in the second comparator 28. For this reason, when a 12-cm compact disk or an 8-cm compact disk with an adaptor is to be rotationally driven, the servo gain switch signal S GAIN is output, In this embodiment, a phase comparison signal between a clock signal separated from a reproduction signal and a predetermined reference signal is output together with an output signal from the amplifier 18 to the driver 19. When the servo gain switch signal S GAIN rises, the signal level of the phase comparison signal to be output to the driver 19 is raised, thereby increasing the servo gain of the PLL circuit. When the spindle motor 3 is to drive a heavy object, therefore, the spindle motor 3 is phase-controlled by a larger servo gain, thereby reliably reproducing an audio signal. A conventional compact disk player of this type includes the frequency generator 4, the frequency/voltage converter 6 and the like in order to activate the spindle motor 3. According to this embodiment, however, an object to be rotationally driven by the spindle motor 3 can be reliably detected by only adding the timer circuit 26 and the like on a circuit board. Unlike in a conventional apparatus, therefore, the type of an object to be driven can be detected without proving an exclusive detecting mechanism such as a photoreflector or a photointerruptor. As a result, an arrangement of the compact disk player 1 as a whole can be simplified. In addition, the type of an object to be rotationally driven is detected on the basis of the activation response state of the spindle motor 3 which changes in accordance with the object to be rotationally driven. Therefore, erroneous detection caused by a conventional apparatus can be prevented, thereby reliably switching the servo gain. In this embodiment, as described above, the frequency generator 4, the frequency/voltage converter 6 and the controller 15 constitute a detector for detecting the activation response state of the spindle motor 3. The frequency generator 4, the frequency/voltage converter 6, the operational amplifier 8, the resistors 9, 11 and 13, the controller 15, the amplifier 18 and the driver 19 constitute an activating circuit for activating the spindle motor 3. With this arrangement, a time period required for the output signal S V to rise to a predetermined voltage (i.e., a voltage determined by the reference data D REF1 ) is detected to detect the activation response state of the spindle motor 3. Therefore, the type of an object to be rotationally driven by the spindle motor 3 can be reliably detected with a simple arrangement. In addition, the servo gain of the PLL circuit can be switched to reliably reproduce an audio signal. Figs. 3 and 4A to 4B2 show the second embodiment of the present invention. In the second embodiment, a spindle motor 3 is activated at a timing t₀, and an output voltage S V is detected at a timing t₃ after a predetermined period of time elapses, thereby detecting an activation response state of the spindle motor 3. That is, in a controller 35, a timer circuit (TIM2) 36 is reset at the timing t₀ (Fig. 4A) on the basis of a control signal S C and then counts a predetermined clock signal S CK . When the count reaches a predetermined value, the timer circuit 36 outputs a latch signal S R to a latch circuit (LCH) 37, thereby fetching a digital value of the output signal S V (Figs. 4B1 and 4B2) into the latch circuit 37 at the timing t₃. When a 12-cm compact disk or an 8-cm compact disk fixed to an adaptor is to be driven, therefore, data having a small value is latched by the latch circuit 37. To the contrary, when an 8-cm compact disk body alone is to be driven, data having a large value is latched by the latch circuit 37. A comparator (COM3) 38 discriminates the magnitude of the data stored in the latch circuit 37 on the basis of predetermined reference data D REF3 and outputs the discrimination result as a servo gain switch signal S GAIN . According to the arrangement shown in Fig. 3, the output voltage S V is detected when a predetermined period of time elapses after the spindle motor 3 is activated, thereby detecting the activation response state of the spindle motor 3. The same effect as in the first embodiment can be obtained in this arrangement. Note that the arrangement except for the control circuit 35 is the same as the first embodiment and a detailed description thereof will be omitted. In the above embodiments, the output voltage S V from the frequency/voltage converter 6 is fetched to the controller 15 to detect the activation response state of the spindle motor 3. The present invention, however, is not limited to the above embodiments. For example, the output signal from the frequency generator 4 may be fetched directly to the controller to detect the activation response state. In addition, in the above embodiments, the controller is constituted by a timer circuit and the like. The present invention, however, is not limited to the above embodiments. For example, the controller may be constituted by a microcomputer. Furthermore, in the above embodiments, the type of an object to be rotationally driven is detected, and the servo gain of the PLL circuit is switched on the basis of the detection result. The present invention, however, is not limited to an arrangement in which the servo gain is switched but can be widely applied to an arrangement in which the type of an object to be rotationally driven is displayed and the like. Moreover, in the above embodiments, the present invention is applied to a compact disk player. The present invention, however, is not limited to a compact disk player but can be widely applied as a disk rotary driving apparatus for an optical disk reproducing apparatus for reproducing a compact disk and a video disk and an optical disk recording apparatus for optically recording an information signal in an optical disk. As has been described above, according to the present invention, an object to be rotationally driven by a spindle motor is detected on the basis of an activation response state of the spindle motor. Therefore, a disk rotary driving apparatus capable of reliably detecting the type of an object to be rotationally driven can be obtained with a simple arrangement.

Claims: A disk rotary driving apparatus (1) comprising: a spindle motor (3) for rotationally driving a disk (2); a servo loop (4, 6, 7, 18, 19) for controlling the rotation of said spindle motor (3); and a control circuit (15) for detecting an activation response state of said spindle motor (3) upon starting on the basis of a voltage proportional to the rotation of said spindle motor (3) when a predetermined period of time has elapsed after said spindle motor (3) is activated by an activating signal (S c ) and switching the gain of said servo loop on the basis of the detection result, characterized by an analog/digital converter (23) within said control circuit (15) for analog/digital-converting an information signal (S v ) proportional to the rotation of said spindle motor (3); a first comparator (24) for comparing an output signal from said analog/digital converter (23) with first reference data (D REF1 ); a timer circuit (26) started by the activating signal (S c ) for said spindle motor (3) for counting a clock signal (S CK ) until an output signal (S E ) from said first comparator (24) rises; and a second comparator (28) comparing an output signal from said timer circuit (26) with second reference data (D REF2 ) and outputting a control signal (S GAIN ) for switching the gain of said servo loop on the basis of a comparison output signal from said second comparator (28). A disk rotary driving apparatus (1) comprising: a spindle motor (3) for rotationally driving a disk (2); a servo loop (4, 6, 7, 18, 19) for controlling the rotation of said spindle motor (3); and a control circuit (35) for detecting an activation response state of said spindle motor (3) upon starting on the basis of a voltage proportional to the rotation of said spindle motor (3) when a predetermined period of time has elapsed after said spindle motor (3) is activated by an activating signal (S c ) and switching the gain of said servo loop on the basis of the detection result, characterized by an analog/digital converter (23) within said control circuit (35) for analog/digital converting an information signal (S V ) proportional to the rotation of said spindle motor (3); a latch circuit (37) for latching an output from said analog/digital converter (23); a timer circuit (36) for counting a clock signal (S CK ) on the basis of said spindle motor (3) activation signal and outputting a latch signal (S R ) when the count reaches a predetermined value; and a comparator (38) for comparing an output signal from said latch circuit (37) with reference data (D REF3 ) and outputting a control signal (S GAIN ) for switching the gain of said servo loop on the basis of the comparison output from said comparator (38).

Inventors: HATTORI HIDEKAZU C O SONY CORP, ITO HIROYUKI C O SONY CORPORAT, KITANI SATOSHI C O SONY CORPOR, HATTORI, HIDEKAZU, C/O SONY CORPORATION, ITO, HIROYUKI, C/O SONY CORPORATION, KITANI, SATOSHI, C/O SONY CORPORATION
Applicants: SONY CORP, SONY CORPORATION
Application year: 1990
Main classification: G11B7
IPC codes: G11B19, G11B7