Patent Application
20070217779
After years of continual improvement and refinement, digital cameras now provide an attractive alternative to photographic film cameras, due primarily to their affordability, ease of use, advanced resolution, large image storage capability, and other factors. Nevertheless, due to increasing competition between digital camera manufacturers, the process of improving upon current digital camera offerings continues unabated. Any potential advantage provided by a digital camera over the competition for the benefit of the customer can result in augmented sales, and hence additional revenue, for the manufacturer.
One particular facet of digital cameras often targeted for improvement is battery life. Since batteries provided for powering digital cameras are often of the rechargeable variety, extending the time between recharging cycles is desirable for most customers. For example, recharging batteries is impractical in a number of circumstances, such as boating trips, mountain hikes, and the like, when accessibility to an external power source is limited.
Many efforts at extending battery life have focused on increasing the charge capacity of batteries, and on enhancing the power efficiency of the camera itself, especially when performing various functions, such as image capture, optical zoom, and others. While such efforts have yielded significant increases in battery life up to this point, further such improvements using these same or similar methods are likely to be less dramatic.
One particular way in which battery life can be further extended is by recapturing electrical charge stored in a capacitor back into the battery when the functionality of the capacitor is no longer immediately required. One embodiment of the invention, an apparatus 100 for performing this task, is depicted in the simplified block diagram of
In the specific embodiment of
Also shown in
Referring to the apparatus 100, the charge recovery controller 120 is configured to generate a signal 108 indicating when electrical charge is to be recovered from the capacitor 4. In one embodiment, the signal 108 is generated when the device in which the apparatus 100 resides, such as a digital camera, is turned off. Typically, as part of a power-up procedure, a digital camera will cause the flash capacitor 4 to be energized by way of the battery 2. Once the camera is turned off, the capacitor 4 need not remain charged, as leakage current will tend to drain the charge from the capacitor 4 over an extended period of time, thus wasting the charge. Thus, transferring at least a portion of the charge from the capacitor 4 back to the battery 2 would be desirable once the camera is turned off.
In another embodiment, the signal 108 is generated when the camera is placed in a “no-flash” mode. Such a mode could occur, for example, when the camera is brought from a dark room to a more brightly-lit location, such as outdoors, thus reducing or eliminating the need for a flash. In another example, a no-flash mode could be employed for long exposure times, time-lapse imaging, and other imaging uses.
The charge recovery controller 120 may take any of a number of forms. In one implementation, the charge recovery controller 120 may be software instructions executable on a processor, such as a microprocessor, microcontroller, or similar algorithmic processing unit. In another example, the charge recovery controller 120 is electronic hardware, such as that found within an application-specific integrated circuit (ASIC) for generating the signal 108. A combination of software and hardware may be employed in yet another embodiment to provide the charge recovery controller 120.
The charge recovery circuit 110 of
One embodiment of the charge recovery circuit 110 is the charge recovery circuit 210 shown in
A switch 214 positioned between the voltage converter 212 with the battery 2 (shown in
When the pulse of the signal 208 begins at tS, the switch 214 is closed, causing charge from the capacitor 4 to be transferred across the voltage converter 212 and the switch 214 to the battery 2, thereby causing the voltage across the battery 2 (at terminal 204) to initially rise above the normal operating voltage VB, thus storing charge into the battery 2. As the charge is transferred from the capacitor 4 to the battery 2, the voltages at the associated terminals 206, 204 decrease until no more charge is yielded from the capacitor 4. At some point thereafter, the pulse of the signal 208 may be terminated, thus once again opening the switch 214.
Given the particular configuration of the charge recovery circuits 110, 210, at least some portion of the charge that would otherwise be wasted through current leakage of the capacitor 4 is transferred back into the battery 4 when the charge in the capacitor 4 is not required. In the specific example of a camera, the charge is not needed in the capacitor when the attached flash tube is not to be operated, such as when the camera is turned off or placed in a no-flash mode. Depending on the use of the camera, such as when the camera is turned off between each image capture over a long series of images, the total amount of charge recovered may be significant.
In another embodiment of the invention, a method 400 for recapturing electrical charge from a capacitor is illustrated in the flow diagram of
In one particular embodiment of the method 400, the transferring of the electrical charge is accomplished by way of converting a first voltage from the capacitor as a result of the electrical charge to a second voltage compatible with the battery, and by electrically coupling the voltage converter with the battery in response to generating the signal. In one specific implementation, the second voltage is higher than a voltage of the battery in a fully-charged state, as described above.
The generating of the signal may occur when a device incorporating the capacitor, such as a camera, is turned off. In another implementation, the signal is generated when the camera is placed in a no-flash mode.
While several embodiments of the invention have been discussed herein, other embodiments encompassed by the scope of the invention are possible. For example, while some embodiments of the invention are described above in conjunction with digital cameras, other types of cameras, such as ordinary photographic film cameras, and other types of portable devices deriving power from a rechargeable battery, may also benefit from application or adaptation of the various embodiments, as presented above. Further, aspects of one embodiment may be combined with those of alternative embodiments to create further implementations of the present invention. Thus, while the present invention has been described in the context of specific embodiments, such descriptions are provided for illustration and not limitation. Accordingly, the proper scope of the present invention is delimited only by the following claims.
