Abstract:
An OPU burnout protection circuit and a optical drive utilizing the same. The OPU burnout protection circuit monitors power status of an OPU driver of the optical drive to prevent burnout of an OPU when an application specific integrated circuit (ASIC) chip or central processing unit (CPU) chip malfunctions.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an optical drive, and in particular to an optical pickup unit (OPU) burnout protection circuit and an optical drive utilizing the same.  
           [0003]    2. Description of the Related Art  
           [0004]    When fabricating an optical drive, i.e. a CD-ROM, CD-RW, DVD-RW, burnout of an optical pickup unit (OPU) thereof due to failure or malfunction of an application specific integrated circuit (ASIC) chip or central processing unit (CPU) chip is a common problem. Unlike a computer crash, wherein damage to internal components can be prevented by a simple restart, burnout of the OPU in the optical drive is unrecoverable. The OPU has an acrylic rather than glass optical lens. When an optical drive malfunctions continuously, large current passes through coils of an actuator, thus overheating the coils.  
           [0005]    As shown in FIG. 1, Focus+, Focus−, Track+, and Track− are pins of an OPU driver  1  for controlling an OPU  100  to move upward, downward, leftward, and rightward for reading or writing data on a compact disc. Coils are coupled with the pins near the OPU  100 . When an optical drive malfunctions, large current flows through the coils generating excessive heat therein. The continuous heat alters the chemical properties of the coils and internal resistance thereof. Additionally, the overheated coils affect the actuator causing the acrylic optical lens of the OPU  100  to melt.  
           [0006]    Currently, an ASIC chip has neither a protection mechanism nor detection function. Therefore, a detection circuit is necessary for generating a reset signal to restart the optical drive when a malfunction is detected, thus preventing damage thereto.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention provides a circuit for generating a reset signal to restart an optical drive when the optical malfunctions, preventing burnout of an optical pickup unit (OPU) thereof due to overheated coils nearby.  
           [0008]    The present invention provides an OPU burnout protection circuit and an optical drive utilizing the same, monitoring power status of an OPU driver of the optical drive to prevent burnout of an OPU when an application specific integrated circuit (ASIC) chip or central processing unit (CPU) chip malfunctions.  
           [0009]    The optical drive has a driver integrated circuit (IC) driving a motor and an actuator thereof. One pin of the driver IC is connected with a power source supplying the necessary power to the actuator. In the present invention, a resistor is connected between the power source and the pin of the driver IC, and a protection circuit monitors power at both ends of the resistor. The protection circuit comprises a monitoring impedance, a malfunction detector, and a malfunction identifier.  
           [0010]    The monitoring impedance is coupled with a first power source and a power input end of the OPU driver for monitoring the power status thereof when using the first power source. When a malfunction occurs in the first power source, such as high current in the Focus and Track coils shown in FIG. 1, a sudden voltage drop of the first power source causes an obvious voltage difference V diff  at the monitoring impedance.  
           [0011]    The malfunction detector is coupled with the first power source and the power input end of the OPU driver. When the optical drive and the OPU driver thereof using the first power source malfunction, the malfunction detector detects the voltage difference V diff  and outputs a notification signal.  
           [0012]    The malfunction identifier receives and processes the notification signal output from the malfunction detector for determining whether the notification signal is temporary, if so, the malfunction identifier stays in standby mode. If not, the malfunction identifier outputs a warning signal to direct the optical drive to execute a specific operation for preventing burnout of the OPU due to overheated coils nearby.  
           [0013]    A detailed description is given in the following embodiments with reference to the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
         [0015]    [0015]FIG. 1 is a block diagram of a conventional OPU.  
         [0016]    [0016]FIG. 2 is a block diagram of an optical drive with OPU burnout protection.  
         [0017]    [0017]FIG. 3 is a block diagram of a protection circuit in detail.  
         [0018]    [0018]FIG. 4 shows circuits of a malfunction identifier.  
         [0019]    [0019]FIG. 5 shows circuits of a protection circuit of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    [0020]FIG. 2 is a block diagram of an optical drive  30  with OPU burnout protection. The optical pickup unit (OPU) burnout protection optical drive  30  includes an OPU  100 , an OPU driver  1 , and a protection circuit  30   a . The protection circuit  30   a  includes a monitoring impedance  2 , a malfunction detector  5 , and a malfunction identifier  6 . The monitoring impedance  2  is coupled with a first power source V cc  and a power input end of the OPU driver  1 . The malfunction detector  5  is coupled with both ends of the monitoring impedance  2 . The malfunction identifier  6  is coupled with the malfunction detector  5 . The monitoring impedance  2  monitors power status of the OPU driver  1  when the OPU driver  1  uses the first power source V cc . When the OPU driver  1  using the first power source V cc  malfunctions due to, for example, high current in the Focus and Track coils shown in FIG. 1, the power input end of the OPU driver  1  gains high current from the first power source VCC, thus causing a voltage difference V diff  between two ends of the monitoring impedance  2 . When detecting the voltage difference V diff , the malfunction detector  5  outputs a notification signal to the malfunction identifier  6 . The malfunction identifier  6  determines whether the notification signal is temporary, if so, the malfunction identifier  6  stays in standby mode. If not, the malfunction identifier  6  outputs a warning signal to direct the OPU burnout protection optical drive  30  to execute a specific operation for preventing burnout of the OPU  100 .  
         [0021]    [0021]FIG. 3 is a block diagram of the protection circuit  30   a  in detail. The malfunction detector  5  comprises a first voltage divider  7 , a second voltage divider  8 , and a first voltage comparator  9 . The first and the second voltage dividers  7  and  8  are respectively coupled with two ends of the monitoring impedance  2 . The first voltage comparator  9  is coupled with the first and the second voltage dividers  7  and  8 . Normally, the first and the second voltage dividers  7  and  8  respectively generate two fixed voltages, a first voltage V1 and a second voltage V2, and the first voltage V1 is less than the second voltage V2. When occurring between two ends of the monitoring impedance  2 , the voltage difference V diff  causes a drop of the second voltage V2. When the second voltage V2 becomes less than the first voltage V1, the first voltage comparator  9  immediately outputs the notification signal to the malfunction identifier  6 .  
         [0022]    The malfunction identifier  6  includes a temporary state eliminator  10  and a warning output device  11 . The temporary state eliminator  10  is disposed between the first voltage comparator  9  and the warning output device  11 . The temporary state eliminator  10  determines whether the notification signal is temporary, if so, the malfunction identifier  6  stays in standby mode. If not, the malfunction identifier  6  outputs the warning signal to direct the optical drive  30  to execute a specific operation, such as restarting the optical drive  30  or the OPU driver  1 , to prevent burnout of the OPU  100 .  
         [0023]    [0023]FIG. 4 shows circuits of the malfunction identifier  6 . The temporary state eliminator  10  includes a first resistor  14  and a unidirectional conduction device  12  connected in parallel and disposed between the malfunction detector  5  and the warning output device  11 . A capacitor  15  is coupled with the first resistor  14 . A third resistor  16  and a fourth resistor  17  constitute a voltage dividing circuit and supply a reference voltage V ref  to the warning output device  11 . The unidirectional conduction device  12  comprises a diode  13 . The warning output device  11  includes a second voltage comparator  18  coupled with an output end of the temporary state eliminator  10  and a pulse generator  20 . The second voltage comparator  18  comprises a second operational amplifier  19 . The pulse generator  20  comprises a second capacitor  21  and a fifth resistor  22 . When the temporary state eliminator  10  receives the notification signal, an output voltage V3 of the second operational amplifier  19  does not increase rapidly, due to the integrator comprising the first resistor  14  and the capacitor  15 . In addition, because the integrator is connected in parallel with the diode  13 , the integrator has a low charge rate and a high discharge rate. If the malfunction detector  5  continuously outputs high voltage for a considerable period, voltage of the capacitor  15  is charged to exceed the reference voltage V ref , and thus the output voltage V3 of the second operational amplifier  19  becomes high voltage. The period is adjusted by setting various values of the first resistor  14  and the capacitor  15 . When the output voltage V3 of the second operational amplifier  19  is high, the pulse generator  20  outputs the warning signal having a single pulse. The warning signal drives the OPU burnout protection optical drive  30  to execute a specific operation preventing burnout of the OPU  100  due to overheated coils near the OPU.  
         [0024]    [0024]FIG. 5 shows circuits of the protection circuit  30   a  of the present invention. The monitoring impedance  2  comprises a monitoring resistor  3  having a relatively small value, such as 0.5 Ω. The first voltage divider  7  comprises an eighth resistor  26  and a ninth resistor  27 . The second voltage divider  8  comprises a third capacitor  23 , a sixth resistor  24 , and a seventh resistor  25 . The first voltage comparator  9  is a first operational amplifier  28 .  
         [0025]    While the invention has been described by way of example and in terms of the preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.