Patent Publication Number: US-2006012819-A1

Title: Imaging device power management system and method

Description:
BACKGROUND  
      Imaging devices are generally powered by a conventional alternating current (AC) external power source (i.e., 100-120 volts or, for some countries, 200-240 volts). Recently, a data interface bus (e.g., a universal serial bus (USB)) has become a widely used medium for providing power to various types of imaging devices, thereby enabling the device to obtain power from another electronic device (e.g., a desktop or notebook computer) and alleviating a need for a separate conventional AC power source or outlet. However, because of the generally low power level available via a data interface bus (e.g., approximately 2 watts), scanning operations performed by the imaging device using power supplied by a data interface bus are generally very slow.  
     SUMMARY OF THE INVENTION  
      In accordance with one embodiment of the present invention, an imaging device power management system comprises a control circuit adapted to vary a duty cycle of a scanning module of an imaging device during a scanning operation performed by the scanning module based on a source of energy coupled to the imaging device for operating the scanning module.  
      In accordance with another embodiment of the present invention, an imaging device power management method comprises varying a duty cycle of a scanning module of an imaging device during a scanning operation performed by the scanning module based on the type of energy source coupled to the imaging device for performing the scanning operation.  
      In accordance with another embodiment of the present invention, an imaging device power management system comprises a light source adapted to illuminate an object during a scanning operation and a storage device adapted to store energy received from a data interface bus. The system also comprises a control circuit adapted to vary a duty cycle of the light source during the scanning operation corresponding to the energy stored in the storage device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following descriptions taken in connection with the accompanying drawings in which:  
       FIG. 1  is a diagram illustrating an embodiment of an imaging device power management system in accordance with the present invention;  
       FIG. 2  is diagram illustrating an embodiment of a control circuit of the imaging device power management system of  FIG. 1 ; and  
       FIG. 3  is a flow diagram illustrating an embodiment of an imaging device power management method in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
      The preferred embodiments of the present invention and the advantages thereof are best understood by referring to  FIGS. 1-3  of the drawings, like numerals being used for like and corresponding parts of the various drawings.  
       FIG. 1  is a diagram illustrating an embodiment of an imaging device power management system  10  in accordance with the present invention. In the embodiment illustrated in  FIG. 1 , system  10  comprises an imaging device  12  adapted to receive power or energy from any of a plurality of different types of energy sources. For example, in the embodiment illustrated in  FIG. 1 , imaging device  12  is configured to receive energy from an external energy source  16 , represented as V W , and a data interface bus energy source  18 , represented as V I . Data interface bus energy source  18  may comprise any type of bus or data communication medium for supplying power or energy to imaging device  12  such as, but not limited to, a universal serial bus (USB). External energy source  16  may comprise any type of energy source for providing energy or power to imaging device  12  such as, but not limited to, a conventional AC power supply (e.g., 100-120 volts or, in some countries, 200-240 volts). It should be understood that additional and/or other types of energy sources may also be used to provide power or energy to imaging device  12 .  
      Imaging device  12  may comprise any type of device for capturing or otherwise generating a scanned image of an object such as, but not limited to, a scanner, facsimile machine, or copier. Briefly, system  10  enables operation of imaging device  12  using any one of a plurality of different types of energy sources and, depending on the type of energy source providing power for operating imaging device  12 , imaging device  12  is configured to variably control a duty cycle of imaging device  12  components to efficiently manage power consumption by imaging device  12  and enable operation of imaging device  12  with a reduced scanning time based on the type of power supply providing power to scanning device  12  for the scanning operation.  
      In the embodiment illustrated in  FIG. 1 , imaging device  12  comprises a power control circuit  20  and a power management control application specific integrated circuit (ASIC)  22  for controlling the operation of a scanning module  30 . In the embodiment illustrated in  FIG. 1 , scanning module  30  comprises a light source  40  for illuminating an object during a scanning operation, a drive motor  42  for either driving or moving scanning module  30  relative to an object during a scanning operation or moving the object relative to scanning module  30 , and a photosensitive sensor  44  for capturing light reflected from the object and generating a scanned image of the object. However, it should be understood that scanning module  30  may comprise other components used during a scanning operation for generating a scanned image of an object.  
       FIG. 2  is a diagram illustrating an embodiment of circuit  20  of system  10  in accordance with the present invention. In the embodiment illustrated in  FIG. 2 , circuit  20  comprises a current limiter  50  disposed between a diode  52  and an input for receiving power or energy, represented as V I , from data interface bus energy source  18  for limiting or controlling an amount of energy or power drawn or otherwise received from data interface bus energy source  18 . Energy or power received from external energy source  16  is represented in  FIG. 2  as V W . In operation, diode  52  prevents energy received from external energy source  16  from flowing through a port associated with data interface bus energy source  18 . Circuit  20  also comprises a voltage regulator  54  disposed between diode  52  and scanning module  30  to regulate a voltage level supplied to scanning module  30 . In the embodiment illustrated in  FIG. 2 , circuit  20  also comprises a storage device  60  for storing energy or power received from data interface bus energy source  18 , represented as V C . In the embodiment illustrated in  FIG. 2 , storage device  60  comprises a capacitor  62 . As illustrated in  FIG. 2 , ASIC  22  is coupled to circuit  20  having inputs corresponding to V I , V W , V C , and V R , where V C  represents a voltage level stored by storage device  60 , and V R  represents a voltage level necessary for operating scanning module  30 . Measurement of voltage levels corresponding to locations of circuit  20  identified as V I , V W , V C , and V R  may be obtained using any type of voltage measurement device.  
      In operation, ASIC  22  monitors voltage levels of circuit  20 , such as V I , V W , V C , and V R , to determine and control a duty cycle for operating scanning module  30  during a scanning operation. For example, if inputs to ASIC  22  indicate that energy is being received by imaging device  12  by external energy source  16 , for example, based on a voltage measurement of V W , ASIC  22  is configured to operate scanning module  30  at a particular duty cycle, for example, a 100% duty cycle. However, if imaging device  12  is receiving a reduced level of power or energy, for example, from data interface bus energy source  18 , ASIC  22  is configured to vary a duty cycle for operating scanning module  30  during a scanning operation. For example, in operation, when energy is received via data interface bus energy source  18 , energy is stored by storage device  60  such that energy from storage device  60  is used to operate scanning module  30  during a scanning operation. If the energy level of storage device  60  is equal to or decreases to a value within a predetermined threshold or range of V R , ASIC  22  pauses the scanning operation, for example, by turning off light source  40  and suspending movement of scanning module  30 , to enable or otherwise facilitate recharging of storage device  60 . In response to the energy level stored in storage device  60  increasing to a predetermined value or threshold, ASIC  22  resumes the scanning operation by turning on light source  40  and resuming movement of scanning module  30 . Thus, for example, when V C  is equal to or greater than V R  plus a predetermined voltage measurement or threshold, ASIC  22  is configured to resume operation of scanning module  30 . Additionally, as described above, if power or energy is available via external energy source  16 , V C  will be greater than V R , thereby enabling operation of scanning module  30  at a 100% duty cycle. Logic rules for operating scanning module  30  at a variable duty cycle may be expressed by the following: when V C =V R  (or V R +C), where C represents a predetermined or threshold voltage level, ASIC  22  is configured to turn off light source  40  and pause or suspend movement of scanning module  30 ; and when V C =V I +C, ASIC  22  is configured to turn on light source  40  and resume the scanning operation. Thus, ASIC  22  is configured to automatically vary a duty cycle of scanning module  30  (e.g., by varying a duty cycle of light source  40 ) based the type of energy source providing energy to imaging device  12  and/or stored energy level within storage device  60 .  
       FIG. 3  is a flow diagram illustrating an embodiment of an imaging device power management method in accordance with the present invention. The method begins at block  100 , where ASIC  22  controls movement of scanning module  30  to a scanning position. At block  102 , ASIC  22  determines a stored power level of storage device  60 . At decisional block  104 , a determination is made whether the stored energy level of storage device  60  exceeds a predetermined threshold. If the stored energy level of storage device  60  does not exceed a predetermined threshold, the method proceeds to block  102 , where ASIC  22  continues monitoring the stored energy level of storage device  60 . If the stored energy level of storage device  60  exceeds a predetermined threshold, the method proceeds to block  106 , where ASIC  22  turns on light source  40  of scanning module  30 . At block  108 , ASIC  22  performs, or otherwise causes scanning module  30  to perform, a scanning operation. For example, as described above, imaging device  12  may be configured to move scanning module  30  relative to a stationary object, or move the object relative to a stationary scanning module  30 . At block  110 , scanning module  30  generates image data corresponding to the scanned object.  
      At block  112 , ASIC  22  monitors a stored energy level of storage device  60 . At decisional block  114 , a determination is made whether the energy storage level within storage device  60  has decreased or fallen below a predetermined threshold. If the stored energy level within the storage device  60  has not decreased or fallen below a predetermined threshold, the method proceeds to decisional block  116 , where a determination is made whether the scanning operation is complete. If the scanning operation is not yet complete, the method proceeds to block  108 , where the scanning operation continues. If the scanning operation is complete, the method ends.  
      If at decisional block  114  it is determined that the energy level stored within storage device  60  has decreased or fallen below a predetermined threshold, the method proceeds to block  118 , where ASIC  22  suspends movement of scanning module  30  and turns off light source  40 . At block  120 , ASIC  22  pauses the scanning operation to enable recharging of storage device  60 . The method then proceeds to block  102 , where ASIC  22  monitors or otherwise determines the energy level stored by storage device  60 .  
      Thus, embodiments of the present invention enable operation of imaging device  12  at a variable duty cycle based on a source of energy supplying power to the imaging device. Thus, for example, when energy is being supplied to imaging device via a data interface bus, the duty cycle of scanning module  30  is variably controlled to facilitate efficient operation of imaging device  12  and, if power is available from another energy source capable of providing a greater energy level than the data interface bus, the duty cycle is variably controlled to reduce the time necessary for completing the scanning operation.