Abstract:
A motor rotation control device for an optical disk player including a motor outputting rotation signals, a sensor for sensing the rotational direction and rotational state of the motor in response to rotation signals of the motor, a motor control signal generator for generating a motor control signal according to the rotational direction and rotational state of the motor, and a motor rotation controller for controlling the rotation of the motor in response to the motor control signal. The motor rotation control device operates independently of a system controller, thereby reducing the load on the system controller.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Application No. 80578/1997, filed Dec. 31, 1997, in the Korean Patent Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to an optical disk player, and more particularly, to a motor rotation control device for an optical disk player. 
     FIG. 1 is a diagram of a conventional motor rotation control device  10 . To rotate a stationary disk (not shown) at a normal speed, a system controller  100  outputs a forward acceleration signal to a motor rotation controller  102  causing a motor  104  to forwardly accelerate. When the disk is rotating at a normal speed, the system controller  100  supplies a normal driving signal to the motor rotation controller  102  causing the motor rotation controller  102  to continue rotation of the motor  104  so as to maintain a Constant Angular Velocity (CAV) or a Constant Linear Velocity (CLV) of the optical disk. If the motor  104  accelerates to an explosive (or overrun) state, the system controller  100  outputs a backward acceleration signal to the motor rotation controller causing the motor  104  to backwardly accelerate (i.e., decelerate) so as to reach a normal speed range. During operation, the motor  104  supplies motor rotation signals (including a period of rotation) to the system controller  100 . 
     In summary, the motor rotation controller  102  causes the motor  104  to forwardly rotate in response to a forward acceleration signal, controls the motor  104  at a CLV/CAV in response to a normal driving signal, and causes the motor  104  to rotate backwards in response to a backward acceleration signal. 
     FIG. 2 is a flowchart of a conventional motor rotation control process. At step  200 , the system controller  100  generates a forward acceleration signal to accelerate the motor  104  forwardly. At step  202 , the system controller  100  checks the period of the rotation, using the motor rotation signal generated from the motor  104 , and judges whether the number of rotations per unit of time of the motor  104  is greater than a number N corresponding to a forward acceleration limit speed. If the number of rotations is not greater than the number N, the process goes to step  204  and the system controller  100  continues to accelerate the motor  104  forwardly. If, in step  202 , the number of rotations is greater than the number N, the process goes to step  206  and the system controller  100  checks whether the number of rotations per unit of time of the motor  104  is less than a number M corresponding to a backward acceleration limit speed. 
     If, in step  206 , the number of rotations is less than the number M, the process goes to step  210  and the system controller  100  carries out normal CLV/CAV control of the motor  104 . The process then returns to step  202 . If, in step  206 , the number of rotations is not less than the number M, the process goes to step  208  and the system controller  100  generates a backward acceleration signal to accelerate the motor  104  backwardly at step  208 . The process then returns to step  202 . 
     The system controller  100  must continually check the rotation period of the motor  104  so as to be able to set a forward acceleration speed and a backward acceleration speed for the motor  104 . Hence, the system controller  100  must spend a lot of time checking the rotation speed of the motor  100 . Unfortunately, in the conventional motor rotation control device, while controlling the motor  100  at a CLV/CAV, the system controller  100  does not know whether the motor  104  is rotating forwardly or backwardly. Therefore, it is difficult to prevent the motor  104  from rotating backwardly during focus drop, i.e., when the RF signal from the optical pickup contains only noise and no sync signal, and degrading the performance of an optical disk player. 
     The system controller  100  must continually check the rotation period of the motor  104  so as to be able to set a forward acceleration speed and a backward acceleration speed for the motor  104 . Hence, the system controller  100  must spend a lot of time checking the rotation speed of the motor  100 . Unfortunately, in the conventional motor rotation control device, while controlling the motor  100  at a CLV/CAV, the system controller  100  does not know whether the motor  104  is rotating forwardly or backwardly. Therefore, it is difficult to prevent the motor  104  from rotating backwardly during focus drop, i.e., when the RF signal from the optical pickup contains only noise and no sync signal, and degrading the performance of an optical disk player. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a motor rotation control device for an optical disk player which can reduce the load of a system controller while driving a motor. 
     It is a further object of the present invention to provide a motor rotation control device in which a system controller is aware of the rotational direction of the motor. 
     These and other objects of the present invention are realized by a motor rotation control device for an optical disk player comprising a motor, a sensor sensing the rotational direction and rotational state of the motor in response to rotation signals of the motor, a motor control signal generator generating a motor control signal according to the rotational direction and rotational state of the motor, and a motor rotation controller controlling the rotation of the motor in response to the motor control signal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings of which: 
     FIG. 1 is a block diagram of a conventional motor rotation control device; 
     FIG. 2 is a flow chart of a conventional motor rotation control process; 
     FIG. 3 is a block diagram of a motor rotational state detector according to the preferred embodiment of the present invention; 
     FIG. 4 is a diagram of waveforms of signals generated by the rotation of a motor; 
     FIG. 5 is a block diagram of a motor control signal generator according to the preferred embodiment of the present invention; 
     FIG. 6 is a diagram of waveforms showing how a motor rotation control state varies with the number of rotations of a motor; 
     FIG. 7 is a diagram showing the relationship between the number of rotations of a motor and the rotational direction thereof; and 
     FIG. 8 is an overall block diagram of a motor rotation control device according to the preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the following description, numerous specific details are set forth to provide a more thorough understanding of the present invention. However, one skilled in the art does not need every specific detail to practice the invention. Accordingly, well known functions or constructions have not been described, so as not to obscure the description and understanding of the present invention. 
     FIG. 8 is a block diagram of a motor rotation control device  410  according to a preferred embodiment of the present invention. A motor  400  rotates under the control of a motor rotation controller  406 . The motor  400  generates rotation sensing signals u, v and w. A motor rotational state detector  402  checks, in response to the rotation sensing signals u, v, and w, whether the motor  400  is rotating forwardly or backwardly. The motor rotational state detector  402  also determines whether the motor  400  is rotating within the range of a forward accelerated interval, a backward accelerated interval or a normal driving interval. 
     The motor rotational state detector  402  generates a plurality of signals (explained in more detail hereinafter) including a signal indicating the rotational direction of the motor  400  supplied to a system controller  408 . Using this signal, the system controller can determine the rotational direction of the motor  400  at any time. 
     The plurality of signals generated by the motor rotational state detector  402  are supplied to a motor control signal generator  404 . The motor control signal generator  404  generates signals for accelerating the motor  400  forwardly or backwardly. The motor control signal generator  404  also generates a signal for maintaining the motor  400  at a current state. A motor rotation controller  406 , connected to the motor control signal generator  404 , controls the rotation of the motor  400  in response to the signals generated by the motor control signal generator  404 . 
     FIG. 3 is a block diagram of the motor rotational state detector  402  shown in FIG.  8 . The rotation sensing signals u, v and w, sensed from a spindle of the motor  400  at intervals of 120°, are supplied to a binary circuit  300 . The motor  400  may be, for example, a brushless motor. The binary circuit  300  binarizes the sensing signals u, v and w and generates binary signals hu, hv and hw (not shown). The binary signals hu and hv are supplied to a rotational direction sensor  302 , while the sensing signal hu is supplied to a rotational state sensor  304 . The rotational direction sensor  302  compares phases of the binary signals hu and hv to determine whether the motor  400  is rotating forwardly or backwardly and outputs a forward or backward rotation sensing signal, respectively. 
     FIG. 4 is a diagram of waveforms of signals generated by the motor  400  and the binary circuit  300 . Specifically, FIG. 4 shows the sensing signals u, v and w generated from the motor  400  in relationship to the binary signals hu, hv and hw generated from the binary circuit  300 . The sensing signal hu has a period t 1 . The number of rotations of the motor  400  is as follows:                Rotation                   No   .              of                   Motor     =       60              [   sec   ]       m   ×   t1               (   1   )                                
     where m is the number of the binary signals hu generated when the motor  400  rotates once. The binary signal hv is generated a prescribed time after the binary signal hu has been generated. The interval between the rising edge of the binary signal hu and the rising edge of the binary signal hv is a phase difference t 2  between the binary signals hu and hv. When expressing the period t 1  as 360°, the phase difference t 2  is 120° during the forward rotation of the motor  400  and 240° during the backward rotation of the motor  400 . That is, the phase difference t 2  can be expressed as:                Phase                 Difference                 t2                 during                 Forward                 Rotation                 of                 Motor     =     t1   3             (   2   )                 Phase                 Difference                 t2                 during                 Backward                 Rotation                 of                 Motor     =       (     2   ×   t1     )     3             (   3   )                                
     Referring once again to FIG. 3, the rotational direction sensor  302  checks whether the motor  400  rotates forwardly or backwardly by analyzing the phase difference t 2 , which varies according to the forward or backward rotation of the motor  400 . In other words, the rotational direction sensor  302  counts the interval between the rising edge of the binary signal hu and the rising edge of the binary signal hv. If the counted value corresponds to the phase difference t 2  experienced during the forward rotation of the motor  400  (in this example 120°), the rotational direction sensor  302  generates a forward rotation sensing signal. If the counted value corresponds to the phase difference t 2  experienced during the backward rotation of the motor  400  (in this example 240°), the rotational direction sensor  302  generates a backward rotation sensing signal. The rotational direction sensor  302 , in turn, supplies the forward or backward rotation sensing signal to the system controller  408 . Therefore, the system controller can determine the rotational state of the motor  400 . 
     The binary signal hu is supplied to the rotational state sensor  304  which counts the period t 1  of the binary signal hu and determines the rotational state of the motor  400 . Basically, the system controller supplies to the rotational state sensor  304  a number N of rotations corresponding to a forward acceleration limit speed, a number M of rotations corresponding to a backward acceleration speed limit, a number R of rotations corresponding to normal driving, a number A of rotations corresponding to an error limit, and a number E of rotations of an explosive state. The rotational state sensor  304  compares the period t 1 , as counted by a stable clock of crystal series with those numbers. If the counted period value is less than the number N, the rotational state sensor  304  generates a forward acceleration signal; if the counted period value is greater than the number M, the rotational state sensor  304  generates a backward acceleration signal; if the counted value is between R+a and R−a, the rotational state sensor  304  generates a normal driving signal; and if the counted value is greater than the number E, the rotational state sensor  304  generates an explosive signal. The forward and backward rotation sensing signals, the forward and backward acceleration signals, the normal driving signal and the explosive signal are all supplied to the motor control signal generator  404  (see FIG.  8 ). 
     FIG. 5 is a block diagram of the motor control signal generator  404 . The forward rotation sensing signal and the forward acceleration signal, from the motor rotation state detector  402  are supplied to an AND gate. The output of the AND gate and the backward rotation signal are supplied to a NOR gate. The NOR gate outputs a forward acceleration enable signal to the motor acceleration controller  406  (FIG.  8 ). The forward acceleration enable signal is generated when the forward rotation sensing signal and the forward acceleration signal are simultaneously generated or when the backward rotation sensing signal is generated. 
     The normal driving signal is passed through an inverter INV producing a normal driving enable signal. The normal driving enable signal is generated when the normal driving signal is generated. 
     The backward acceleration signal and the explosive signal are supplied to a rising edge detector BD 1 . The rising edge detector BD 1  detects the rising edges of the backward acceleration and explosive signals and generates a backward acceleration edge signal and an explosive edge signal. The backward acceleration edge signal is supplied to a reset terminal of a flip-flop FF, while the explosive edge signal is supplied to a set terminal the flip-flop FF. The flip-flop FF is reset by the backward acceleration edge signal and set by the explosive edge signal. The output of the flip-flop FF is supplied to a NAND gate. The NAND gate receives the output of the flip-flop FF and the forward rotation sensing signal to output a backward acceleration enable signal. The backward acceleration enable signal is generated until the backward acceleration signal is generated since the explosive signal is generated while the forward rotation sensing signal is generated. The forward and backward acceleration enable signals and the normal driving enable signal are supplied to the motor rotation controller  406  (FIG.  8 ). 
     FIG. 6 is a diagram of waveforms showing how the motor rotation control state varies with the number of rotations of the motor. FIG. 7 is a diagram showing the relationship between the number of rotations of a motor and the rotational direction thereof. During operation, a forward acceleration command is issued by the system controller causing the motor  400  to be forwardly accelerated until the number of rotations of the motor  400  is greater than the number N corresponding to a forward acceleration speed. If the number of rotations of the motor  400  is greater than the number N, the forward acceleration is ended. Thereafter, the motor  400  is influenced by inertia and enters a normal driving interval ranging between R+a and R−a. During this period the motor  400  is said to be normally driven. If the number of rotations of the motor  400  reaches the number E of rotations corresponding to the explosive state, the motor control signal generator  404  generates the backward acceleration enable signal to accelerate the motor  400  backwardly. Once the number of rotations becomes less than the number M of rotations corresponding to the backward acceleration limit speed, the backward acceleration is ended. Therefore, the motor  400  is influenced by inertia and enters the normal driving interval ranging between R+a and R−a. 
     As may be appreciated from the aforementioned description, the rotation of the motor is controlled without the constant intervention of the system controller. Therefore, the load of the system controller is reduced. Moreover, the system controller can determine the rotational direction of the motor at any time, and thus can cope with the backward rotation of the motor liable to occur during focus drop. 
     While the invention has been shown and described with reference to a certain preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.