Abstract:
A device and method for reducing power consumption of an optical drive are proposed. The present invention samples a carrier control signal and then compares the samples of the signals with predetermined threshold signals. According to the comparison result, the present invention produces at least one diphase excitation control signal. The diphase excitation control signal comprises at least one impulse signal, and a negative edge of the impulse signal is adjusted to a predetermined level during the period of the diphase excitation control signal. The present invention reduces the time for outputting the control signals and greatly reduces the power consumption of the optical drive thereby.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of application Ser. No. 12/699,743 filed on Feb. 3, 2010, which is a continuation of application Ser. No. 10/933,402 filed on Sep. 3, 2004 now abandoned. The entire contents of each of these applications are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is directed to a device for reducing power consumption of an optical drive and a method for the same, and more particularly, to a device and a method used to reduce the power consumed in track following so as to conserve power. 
     2. Description of Related Art 
     In the optical drives used nowadays, track following is an action that consumes an extreme amount of time and power. However, this action must be fast enough to improve access speed. Since this action is performed in many applications, various searching algorithms available on the market have been developed to make this action more efficient. However, the power consumption thereof is still excessive. 
     Reference is made to  FIG. 1 , which illustrates the track-following signals used nowadays. The sinusoidal wave is a carrier control signal  202 . The conventional method is to obtain specific sample voltages  205  at some specific sample times  204  and then output these sample voltages  205  as diphase excitation control signals  206 . Every diphase excitation control signal  206  will maintain its voltage value until the next sampling time  205  to control the rotation direction of the carrier motor or to stop it. 
     In the present invention, a novel track-following method is proposed to replace the conventional one to save power and further promote efficiency. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide a device and method for reducing power consumption of an optical drive. 
     According to an embodiment of the present invention, a device for reducing power consumption of an optical drive is provided. The device comprises a signal controller for producing a carrier control signal; a signal processor for sampling the carrier control signal to produce a first output signal; a comparator for receiving the first output signal of the signal processor, and comparing the first output signal with at least one threshold signal to produce a second output signal; and a waveform generator for producing at least one diphase excitation control signal according to the second output signal, wherein the diphase excitation control signal comprises at least one impulse signal, and a negative edge of the impulse signal is adjusted to a predetermined level during the period of the diphase excitation control signal. 
     According to a second embodiment of the present invention, a method for reducing power consumption of an optical drive is provided. The method comprises inputting a carrier control signal to a signal processor; sampling the carrier control signal to obtain a sampled carrier control signal by using the signal processor; inputting the sampled carrier control signal to a comparator and comparing the sampled carrier control signal with at least one threshold signal by using the comparator; producing an output signal index according to a comparison result provided by the comparator; and outputting at least one diphase excitation control signal according to the output signal index by using a waveform generator, wherein the diphase excitation control signal comprises at least one impulse signal, and a negative edge of the impulse signal is adjusted to a predetermined level during the period of the diphase excitation control signal. 
     Numerous additional features, benefits and details of the present invention are described in the detailed description, which follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and many of the attendant advantages of this invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a diagram for illustrating track-following control signals of an optical drive in the prior art; 
         FIG. 2  is a diagram of a preferred embodiment of a device for reducing power consumption of an optical drive in accordance with the present invention; 
         FIG. 3A  is a diagram of an internal structure of the signal controller in accordance with the present invention; 
         FIG. 3B  is a diagram of an internal structure of the carrier controller in accordance with the present invention; 
         FIG. 4  is a waveform diagram of diphase excitation control signals provided by the waveform generator in accordance with the present invention; 
         FIG. 5  is a waveform diagram of an output signal index provided by the comparator in accordance with the present invention; 
         FIG. 6A  is a waveform diagram of diphase excitation control signals formed by using a group of gain signals in accordance with the present invention; 
         FIG. 6B  is a waveform diagram of diphase excitation control signals formed by using two groups of gain signals in accordance with the present invention; and 
         FIG. 7  is a flowchart of a method for reducing power consumption of an optical drive in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention relates to a device for reducing power consumption of an optical drive and a method for the same. Reference is made to  FIG. 2 , which is an embodiment of the present invention. The device includes a signal controller  100 , an access controller  120 , a signal processor  140 , a comparator  150 , a waveform generator  160 , a power actuator  170  and a carrier motor  180 . After the signal controller  100  receives a track-following error signal (TE) and a central error signal (CSO), it outputs a track-following control signal (TRO), which is sent to the access controller  120  and used to control the pick-up head  130  to read or write the data. 
     The signal controller  100  outputs a carrier control signal  108  to the signal processor  140 , which samples the carrier control signal  108  and send the sampled carrier control signal  144  to the comparator  150 . The comparator compares the sampled carrier control signal  144  with the positive threshold signal (P-th)  152  and the negative threshold signal (N-th)  154  and then sends out an output signal index. If the sampled carrier control signal  144  is larger than the positive threshold signal  152 , the comparator  150  adds one to the output signal index. If the sampled carrier control signal  144  is smaller than the negative threshold signal  154 , the comparator  150  subtracts one from the output signal index. The waveform generator  160  outputs the diphase excitation control signals  162  (FMO and FMO 2 ) periodically with equal time spacing according to the output signal index sent from the comparator  150 . As the output signal index increases or decreases, the phases of the diphase excitation control signals  162  changes accordingly so as to control the power actuator  170 . Then, the power actuator  170  generates the complementary motor control signals to make the carrier motor  180  rotate forward or backward, or make it stop so as to control the pickup head  130  thereby. 
     Reference is made to  FIG. 3A , which is a diagram of an internal structure of the signal controller in accordance with the present invention. The signal controller includes a track-following error controller  102 , a carrier controller  104  and amplifiers  114 ,  118 . After the track-following error controller  102  receives the track-following error signal (TE), it outputs the track-following control signal (TRO) accordingly. Then, the track-following control signal is delivered to the access controller  120  and the amplifier  114 . The carrier controller  104  then selectively sends out the track-following control signal (TRO) or the central error signal (CSO). In other words, the carrier control signal  108  can be the track-following control signal (TRO) or the central error signal (CSO). 
     If the track-following control signal (TRO) is selected, the amplifier  114  diminishes the same to avoid signal overflow caused by the carrier controller  104 . Then, the amplifier  118  recovers the amplitude of the track-following control signal (TRO) when the track-following control signal (TRO) is output from the carrier controller  104 . 
     Reference is made to  FIG. 3B . The carrier controller  104  is composed of a first low-pass filter  1041  cascaded with a second low-pass filer  1043 . The first low-pass filter  1041  has a high sample rate while the second low-pass filter  1043  has a low sample rate. 
     Reference is made to  FIG. 4 , which shows the diphase excitation control signals produced by the waveform generator  160 . The vertical axis represents voltage value while the horizontal axis represents time. The sinusoidal wave  301  corresponds to the carrier control signal  108  mentioned above and the periodic signals  303  are the output signals of the waveform generator  160 . The periodic signals  303  are generated by sampling the carrier sample signal  108 , i.e., the sampled carrier control signals  144 , after the comparator  150  processes these sample signals. When compared with the sinusoidal signal used in the prior art, using the periodic signals  303  can reduce the power consumption of the optical drive. The use of the periodic signals  303  will be further illustrated in  FIG. 6A . 
     After receiving the carrier control signal  108 , the signal processor  140  samples the carrier control signal  108  according to the predetermined sample rate and the corresponding time spacing  305 . The sample rate can be the sample rate of the second low-pass filter  1043  mentioned above. The carrier control signal  108  is sampled at the sample time  302  to provide the sampled carrier control signal  144  for the comparator  150 . Then, the comparator  150  compares the sampled control signal  144  with the positive threshold signal  152  and the negative threshold signal  154 . 
     Reference is made to  FIG. 5 , which is an embodiment of the present invention. In the figure, the vertical axis represents the increment of the output signal index output from the comparator  150  while the horizontal axis represents the threshold voltage. If the sampled carrier control signal  144  is larger than the positive threshold signal  152 , the comparator  150  adds one to the output signal index. If the sampled carrier control signal  144  is smaller than the negative threshold signal  154 , the comparator  150  subtracts one from the output signal index. If the sampled carrier control signal  144  is located in the middle between the positive threshold signal  152  and the negative threshold signal  154 , the output signal index is maintained. 
     Reference is made to  FIG. 6A , which is an embodiment of the present invention. The increase of the output signal index means the sampled carrier control signal  144  is larger than the positive threshold signal  152 . At this point, the waveform generator  160  samples the carrier control signal  108  continuously according to the waveform of the carrier control signal  108  and outputs a predetermined number of impulse signals  309  with equal time spacing  307 . These impulse signals  309  are the diphase excitation control signals  162  mentioned above. The increase of the output signal index makes the motor  180  rotate forward. On the other hand, the decrease of the output signal index means the sampled carrier control signal  144  is smaller than the negative threshold signal  154  and makes the motor  180  to rotate backward by the same mechanism described above. 
     The sample rate of the diphase excitation control signals  162  can be the sample rate of the first low-pass filter  1041 . Since the first low-pass filter  1041  has a high sample frequency and the second low-pass filter  1043  has a low sample frequency, the time spacing  305  of the carrier control signal  108  is larger than the time spacing  307  of the diphase excitation control signals  162 . After that, the waveform generator  160  does not produce any signal and the power actuator  170  maintains operations according to the previous diphase excitation control signals  162 . 
     Generally, the power consumption is proportional to the output time of the diphase excitation control signals  162 . In the present invention, the sinusoidal wave  301 , i.e., the carrier control signal, is sampled to provide the periodic signals  303 , which are composed of the impulse signals  309  and can be used as the diphase excitation control signals  162 . Furthermore, the sample number is adjustable. 
     Comparing the diphase excitation control signals  162  shown in  FIG. 6A  to the diphase excitation control signal  206  shown in  FIG. 1 , it is seen that the diphase excitation control signals  162  of the present invention include several periodic signals  303  each having a predetermined number of impulse signals  309 , which are the samples of the sinusoidal wave  301 . Furthermore, the control signal  206  of the prior art is formed by sampling the carrier control signal  202  and then keeping the sample voltage value until the next sampling time. Since the diphase excitation control signals  162  of the present invention do not need to last for the whole period of the sinusoidal wave  301  to control the rotation of the carrier motor  180 , power consumption is greatly reduced. Thus, the excitation control signals  162  of the present invention only need to last for a small segment of the whole period to control the carrier motor  180 . That not only saves the electric power considerably but also maintains the operation of the carrier motor  180  efficiently. 
     In  FIG. 6A , the waveform generator  160  employs a group of gain signals to adjust the positive edges of the impulse signals  309 . The waveform generator  160  directly drops the amplitude of the negative edges to zero rather than using the gain signals to adjust them. Since the diphase excitation control signal  162  is composed of multiple impulse signals  309 , the stability of the pickup head  160  is affected because the huge variation of the impulse signals  309  makes the motor  180  vibrate easily. 
     Therefore, the present invention also provides another embodiment. As shown in  FIG. 6B , the impulse signals  309  shown in  FIG. 6A  are replaced by the impulse signals  311 . The waveform generator  160  in this embodiment employs two groups of gain signals to adjust the positive and negative edges of the impulse signals  311 , respectively. Hence, the negative edge of the impulse signal  311  does not drop to zero directly but to the middle, between the amplitude of the positive edge and zero. Thus, the vibration problem of the carrier motor  180  caused by the impulse signals  309  is resolved. 
     When the carrier motor  180  moves the pickup head  130  to the correct optical track, the central error signal (CSO) is zero, as is the carrier control signal  108 . Hence, the output signal index sent from the comparator  150  is unchanged and the waveform generator  160  stops producing the diphase excitation control signal  162 . Meanwhile, the power actuator  170  also stops producing the complementary motor control signals  174  so as to stop the carrier motor  180 . Then, the pickup head  130  starts to access data. 
     Reference is made to  FIG. 7 , which is a flowchart of a method for reducing power consumption of an optical drive in accordance with the present invention. The method includes the steps as follows. The location of the pickup head is detected to calculate the distance between the pickup head and the target track ( 600 ). The central error signal, which represents the distance between the pickup head and the target track, is obtained ( 602 ). The carrier control signal is formed, by the carrier controller processing the central error signal, and output ( 604 ). The carrier control signal is sampled to obtain the sampled carrier control signal ( 606 ). The sampled carrier control signal is compared with the positive and negative threshold signals to determine whether the sampled carrier control signal is larger than the positive threshold signal (P-th) or smaller than the negative threshold signal (N-th), or just located between the positive and negative threshold signals ( 608 ). 
     If the sampled carrier control signal is larger than the positive threshold signal, the process jumps to step  610 . If the sampled carrier control signal is smaller than the negative threshold signal, the process jumps to step  620 . If the sampled carrier control signal is located between the positive and negative threshold signals, the process jumps to step  630 . 
     In the case where the sampled carrier control signal is larger than the positive threshold signal, one is added to the output signal index. Then, due to the increase of the output signal index, the waveform generator  160  provides multiple predetermined diphase excitation control signals formed with equal time spacing to the power actuator. After finishing sending the diphase excitation control signals, the waveform generator  160  stops providing the signals to reduce power consumption and wait for the next diphase excitation control signals ( 612 ). Although the waveform generator  160  stops providing the signals, the power actuator keeps outputting the motor control signals to make the carrier motor rotate forward ( 614 ) according to the diphase excitation control signals received last. 
     In the case where the sampled carrier control signal is smaller than the negative threshold signal, one is subtracted from the output signal index ( 620 ). Then, due to the decrease of the output signal index, the waveform generator  160  provides multiple predetermined diphase excitation control signals formed with equal time spacing to the power actuator. When compared with the diphase excitation control signals mentioned in the above paragraph, it is evident that the diphase excitation control signals at this step have an opposite phase. 
     After finishing sending the diphase excitation control signals, the waveform generator  160  stops providing the signals to reduce power consumption and waits for the next diphase excitation control signals ( 622 ). Although the waveform generator  160  stops providing the signals, the power actuator keeps outputting the motor control signals to make the carrier motor rotate backward ( 624 ) according to the diphase excitation control signals received last. 
     In the case where the sampled carrier control signal is located between the positive and negative threshold signals, the output signal index remains unchanged ( 630 ). Hence, the output signal of the waveform generator  160  returns to zero and the power actuator stops outputting motor control signals to the carrier motor so as to stop the carrier motor. The steps above is performed repeatedly ( 650 ) to move the pickup head to the correct access position. 
     Although the present invention has been described with reference to the preferred embodiment thereof, it will be understood that the invention is not limited to the details thereof. Various substitutions and modifications have been suggested in the foregoing description, and other will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are embraced within the scope of the invention as defined in the appended claims.