Abstract:
An external optical disc drive, connected to a bus from which a supplying voltage and a supplying current are outputted, includes: a voltage detector connected to the bus for receiving and detecting the supplying voltage; a digital signal processor connected to the voltage detector; a motor driver connected to the digital signal processor; and a spindle motor connected to the motor driver; wherein a speed-control signal, for informing the digital signal processor to lower the speed of the spindle motor via the motor driver, is outputted to the digital signal processor from the voltage detector while the supplying voltage is detected lower than a threshold voltage.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a universal serial bus (USB) external optical disc drive, and more particularly to a USB external optical disc drive can be dynamically operated at various speeds based on a detected supplying voltage. 
       BACKGROUND OF THE INVENTION 
       [0002]    USB specification is developed by Microsoft and Intel. In the USB specification, the standard supplying voltage and the supplying current outputted from a USB port are 5V and 0.5 A, respectively. 
         [0003]      FIG. 1  is a block diagram illustrating a system of a USB external device connected to a computer host via a USB port. The system comprises a computer host  10  and a USB external device  12 , where the USB external device  12  is a low-power-consumption device. The computer host  10  further comprises a USB port  102 . In a standard interface of USB specification, there are four terminals including a positive-data terminal (D+), an negative-data terminal (D−), a positive-power terminal (V+), and a ground terminal (GND). The positive-data terminal (D+) and the negative-data terminal (D−) are used for the data transmission between the computer host  10  and the USB external device  12 ; the positive-power terminal (V+) is used for providing the driving powers (supplying voltage and supplying current) to the USB external device  12  from the computer host  10 ; and the ground terminal (GND) is connected to ground. The USB external device  12  also comprises a positive-data terminal (D+), a negative-data terminal (D−), a positive-power terminal (V+), and a ground terminal (GND). The positive-data terminal (D+), negative-data terminal (D−), positive-power terminal (V+), and ground terminal (GND) of the USB external device  12  are connected to the positive-data terminal (D+), negative-data terminal (D−), positive-power terminal (V+), and ground terminal (GND) of the USB port  102 , respectively. 
         [0004]    Because the USB external device  12  is a low-power-consumption device, such as a USB thumb drive or a MP3 device, the power consumption (or supplying current) demanded by the USB external device  12  is lower than the standard supplying current (0.5 A) provided by the USB port  102 , so as the USB external device  12  can work properly if the USB external device  12  is directly connected to the host  10  via one USB port  102 . 
         [0005]    However, once the USB external device is a high-power-consumption device, such as a USB external hard drive, the USB external device may not work properly while the USB external device is connected to the host via only one USB port.  FIG. 2  is a block diagram illustrating a system of a USB external device connected to a computer host via two USB ports. The system comprises the computer host  10  and a USB external device  14 , where the USB external device  14  is a high-power-consumption device. The computer host  10  further comprises a first USB port  104  and a second USB port  106 . Each of the first USB port  104  and the second USB port  106  comprises a positive-data terminal (D+), a negative-data terminal (D−), a positive-power terminal (V+), and a ground terminal (GND). Because the USB external device  14  is a high-power-consumption device and the supplying current demanded by the USB external device  14  is relative high (say, 1 A), the USB external device  14  must be connected to the host  10  via both the first USB port  104  and the second USB port  106 , so as a full supplying current can be provided to the USB external device  14 . That is, the positive-power terminal (V+) of the USB external device  14  is coupled in parallel to both the positive-power terminals (V+) of the first USB port  104  and the second USB port  106 ; the ground terminal (GND) of the USB external device  14  is coupled in parallel to both the ground terminals (GND) of the first USB port  104  and the second USB port  106 ; the positive-data terminal (D+) and the negative-data terminal (D−) of the USB external device  14  are connected to either the positive-data terminal (D+) and the negative-data terminal (D−) of the first USB port  104  or the second USB port  106 . Because both the first USB port  104  and the second USB port  106  can provide the standard supplying current (0.5 A), the USB external device  14  can get full supplying current (1 A) while the USB external device  14  is connected to the host  10  via both the first USB port  104  and the second USB port  106  coupled in parallel, so as the high-power-consumption USB external device  14  can work properly. 
         [0006]    However, an extra power adapter may be necessary if the supplying current demanded by a high-power-consumption USB external device is over than 1 A which is the maximum supplying current can be provided by two USB ports coupled in parallel.  FIG. 3  is a block diagram illustrating a system of a USB external device connected to a computer host via a USB port and powered by a power adapter. The system comprises the computer host  10 , a USB external device  16 , and a power adopter  17 . The USB external device  16  is a high-power-consumption device, such as a USB external optical disc drive, and the maximum supplying current demanded by the USB external device  16  is higher than 1 A. The computer host  10  further comprises a USB port  108 . The power adapter  17  further comprises a plug  18  to which an AC power is transmitted. Because the USB external device  16  is a high-power-consumption device and the supplying current demanded by the USB external device  16  is higher than 1 A, the USB external device  16  must be powered by the power adapter  17 , so as the high-power-consumption USB external device  16  can work properly. 
         [0007]      FIG. 4  is a functional block diagram illustrating a conventional USB external optical disc drive. The optical disc drive  20  mainly comprises an optical pickup head  210 , a spindle motor  220 , a sled motor  230 , a radio-frequency amplifier  250 , a first motor driver  260 , a second motor driver  265 , and a DSP (Digital Signal Processor)  270 . The spindle motor  220  is used for spinning an optical disc  22 . The optical pickup head  210  is driven by the sled motor  230  and an actuator including a tracking coil  240  and a focusing coil  245 . The sled motor  210  is used for a long-distance movement of the optical pickup head  210 ; the tracking coil  240  and the focusing coil  245  are used for a small-distance movement of the lens  1  of the optical pickup head  210 . 
         [0008]    An electric signal is generated and transmitted to the radio-frequency amplifier  250  while the data stored on the optical disc  22  is retrieved by the optical pickup head  210 . Afterwards, three output signals including radio-frequency signal (RF), tracking error signal (TE), and focusing error signal (FE) are outputted to the DSP  270  from the radio-frequency amplifier  250  after the electric signal is received and processed by the radio-frequency amplifier  250 . Afterwards, DSP  270  controls the first motor driver  260  to generate a sled-motor driving signal, a tracking-coil driving signal, and a focusing-coil driving signal. Also, DSP  270  controls the second motor driver  265  to generate a spindle-motor driving signal. 
         [0009]    As known in the art, the sled-motor driving signal, the tracking-coil driving signal and the focusing-coil driving signal are capable of moving the optical pickup head  210  and lens  1  to a correct track and a correct focus position. Also, the spindle-motor driving signal is capable of controlling the spindle motor  220  to spin the optical disc  22  at a proper speed. Moreover, the process of moving the lens  1  to a correct disc position at a proper speed can be defined as tracking action. 
         [0010]    Generally, the speed of the optical disc drive  20  means the rotating speed of the spindle motor  220 . That is, if the speed of the optical disc drive  20  is relative high, the rotating speed of the spindle motor  220  is relative high, so as the speed of retrieving data from (or writing data to) the optical disc  22  is relative high. For example, it will take about 57 minutes to completely burn a DVD disc if the optical disc drive  20  is an one-speed optical disc drive (1×-speed); it will take about 28 minutes to completely burn a DVD disc if the optical disc drive  20  is a two-speed optical disc drive (2×-speed); and it will take about 14 minutes to completely burn a DVD disc if the optical disc drive  20  is a four-speed optical disc drive (4×-speed). Moreover, it is understood that a higher supplying current is demanded by the optical disc drive  20  if the spindle motor  220  is operated at a higher speed. 
         [0011]    A USB external optical disc drive is implemented via introducing a USB port in an optical disc drive. Because the spindle motor  220 , the sled motor  230 , and the actuator (the tracking coil  240  and the focusing coil  245 ) are all in action while the USB external optical disc drive is executing the tracking action, the supplying current demanded by the USB eternal optical disc drive is higher than 1 A, so as the USB external optical disc drive must be powered via the power adapter  17  as depicted in  FIG. 3 . However, using a USB external optical disc drive via a power adapter is quite inconvenient to a user. Because the user needs to carry the power adapter to use the USB external optical disc drive. 
       SUMMARY OF THE INVENTION 
       [0012]    Therefore, the present invention relates to a USB external optical disc drive can work without a power adapter. The USB external optical disc drive can be dynamically operated at various speeds based on an inputted supplying voltage. 
         [0013]    The present invention provides an external optical disc drive, connected to a bus from which a supplying voltage and a supplying current are outputted, comprising: a voltage detector connected to the bus for receiving and detecting the supplying voltage; a digital signal processor connected to the voltage detector; a motor driver connected to the digital signal processor; and a spindle motor connected to the motor driver; wherein a speed-control signal, for informing the digital signal processor to lower the speed of the spindle motor from a first speed to a second speed via the motor driver, is outputted to the digital signal processor from the voltage detector while the supplying voltage is detected to be lower than a threshold voltage. 
         [0014]    The present invention provides a control method for an external optical disc drive connected to a bus from which a supplying voltage and a supplying current is outputted, comprising steps of: detecting the supplying voltage at the bus; operating the external optical disc drive at a first speed while the supplying voltage is not lower than a threshold voltage; and operating the external optical disc drive at a second speed while the supplying voltage is lower than the threshold voltage; wherein the first speed is higher than the second speed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed description and accompanying drawings, in which: 
           [0016]      FIG. 1  is a block diagram illustrating a system of a USB external device connected to a computer host via a USB port; 
           [0017]      FIG. 2  is a block diagram illustrating a system of a USB external device connected to a computer host via two USB ports; 
           [0018]      FIG. 3  is a block diagram illustrating a system of a USB external device connected to a computer host via a USB port and powered by a power adapter; 
           [0019]      FIG. 4  is a functional block diagram illustrating a conventional optical disc drive; 
           [0020]      FIG. 5  is a functional block diagram illustrating a USB external optical disc drive of the present invention; and 
           [0021]      FIG. 6  is a flow chart illustrating a control method to use with the optical disc drive of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0022]      FIG. 5  is a functional block diagram illustrating a USB external optical disc drive of the present invention. Similar to the conventional optical disc drive depicted in  FIG. 4 , the USB external optical disc drive  50  mainly comprises an optical pickup head  510 , a spindle motor  520 , a sled motor  530 , a radio-frequency amplifier  550 , a first motor driver  560 , a second motor driver  565 , and a DSP  570 . The spindle motor  520  is used for spinning an optical disc  52 . The optical pickup head  510  is driven by the sled motor  530  and an actuator including a tracking coil  540  and a focusing coil  545 . The sled motor  530  is used for a long-distance movement of the optical pickup head  510 ; the tracking coil  540  and the focusing coil  545  are used for a small-distance movement of the lens  5  of the optical pickup head  510 . 
         [0023]    As descried above, an electric signal is generated and transmitted to the radio-frequency amplifier  550  while the data stored on the optical disc  52  is retrieved by the optical pickup head  510 . Afterwards, DSP  570  controls the first motor driver  560  to generate a sled-motor driving signal, a tracking-coil driving signal, and a focusing-coil driving signal. Also, DSP  570  controls the second motor driver  565  to generate a spindle-motor driving signal. 
         [0024]    The sled-motor driving signal, the tracking-coil driving signal and the focusing-coil driving signal are capable of moving the optical pickup head  510  and lens  5  to a correct track and a correct focus position. Also, the spindle-motor driving signal is capable of controlling the spindle motor  520  to spin the optical disc  52  at a proper speed. 
         [0025]    To guarantee the optical disc drive of the invention can always work properly without being powered via a power adapter, a voltage detector is introduced in the optical disc drive of the invention. The optical disc drive of the invention can be operated at various speed based on the detected supplying voltage. 
         [0026]    As depicted in  FIG. 5 , the supplying voltage (Vdrv) outputted from the positive-power terminal (V+) of a USB port can be detected by the voltage detector  590 . In the embodiment, a speed-control signal with a first level, for informing the DSP  570  to lower the speed of the spindle motor  520 , is outputted from the voltage detector  590  while the detected supplying voltage (Vdrv) is dropped under the threshold voltage (say, 4.5V). Because the spindle motor  520  is the main component to consume the supplying current (Idrv), the required supplying current (Idrv) is decreased if the spindle motor  520  is operated at a lower speed, so as the supplying voltage (Vdrv) will turn to increase. Because the supplying voltage (Vdrv) is increased higher than the threshold voltage (4.5V), the optical pickup head  510  in the invention is guaranteed to always work properly. 
         [0027]    On the other hand, if the supplying voltage (Vdrv) is detected to rise higher than the threshold voltage (4.5V) due to the lower speed of the spindle motor  520  for a while, a speed-control signal with a second level, for informing the DSP  570  to increase the speed of the spindle motor  520 , is outputted from the voltage detector  590 . So that the optical disc drive  50  is operated at the relative high speed and a better performance is obtained. 
         [0028]    For example, the supplying voltage (Vdrv) may drop under the threshold voltage (4.5V) while the required supplying current (Idrv) is instantly raised to 1.1 A when the optical disc drive  50  is operated at a first speed (say, 32×-speed) executing the tracking action. Once the supplying voltage (Vdrv) is detected lower than the threshold voltage (4.5V), a speed-control signal with a first level, for informing the DSP  570  to lower the speed of the spindle motor  520  to a second speed (say, 16×-speed), is outputted from the voltage detector  590 . Then the required supplying current (Idrv) is decreased and the supplying voltage (Vdrv) is increased to the threshold voltage (4.5V). 
         [0029]    It is to be understood that the invention needs not be limited to restrict the speed of the spindle motor  520  either at the first speed (32×-speed) or the second speed (16×-speed). The speed of the spindle motor  520  can be further lowered if necessary. That is, if the supplying voltage (Vdrv) is detected still lower than the threshold voltage (4.5V) after the spindle motor  520  is switched to operate at the second speed (16×-speed) from the first speed (32×-speed) for a while, a speed-control signal with a third level, for informing the DSP  570  to further lower the speed of the spindle motor  520  to a third speed (say, 8×-speed), is outputted from the voltage detector  590 . Then the required supplying current (Idrv) is further decreased and the supplying voltage (Vdrv) is increased to the threshold voltage (4.5V). In the embodiment, the speed of the spindle motor  520  can be lowered to a minimum speed (say, 1×-speed) to guarantee the supplying voltage is maintained higher than the threshold voltage (4.5V), where the optical pickup head  510  can work properly at the minimum speed (1×-speed). 
         [0030]    On the other hand, if the supplying voltage (Vdrv) is detected higher than the threshold voltage (4.5V) due to the spindle motor  520  is switched to operate at the second speed (16×-speed) from the first speed (32×-speed), a speed-control signal with a fourth level, for informing the DSP  570  to increase the speed of the spindle motor  520  at a fourth speed (say, 20×-speed or 32×-speed), is outputted from the voltage detector  590 . 
         [0031]      FIG. 6  is a flow chart illustrating a control method to use with the optical disc drive of the present invention. First, operate the optical disc drive at a first speed, that is, operate the spindle motor to rotate at a first speed (step  41 ). Afterwards, detect the supplying voltage consumed by the optical disc drive (step  43 ). Afterwards, determine the supplying voltage is whether less than the threshold voltage (step  45 ). Operate the spindle motor to rotate at a second speed while the supplying voltage is detected lower than the threshold voltage (step  47 ), where the second speed is lower than the first speed. Or, maintain the spindle motor to rotate at the first speed if the supplying voltage is still higher than the threshold voltage (step  49 ). 
         [0032]    To sum up, when the optical disc drive of the invention may not work properly as a result of the supplying voltage is lower than the threshold voltage, a speed-control signal, for informing the DSP to operate the spindle motor at a lower speed, is outputted to the DSP from the voltage detector. Accordingly, the required supplying current is decreased, so as the supplying voltage is increased and the optical disc drive is guaranteed to have a proper function. 
         [0033]    While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.