JPH09219809A - Residual battery amount detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent erroneous detection due to load fluctuation by detecting a residual battery amount when loads are stable except the time of stroboscopic light emission and exposure or the like. SOLUTION: When a shutter button 1 is pressed, an analog system power supply circuit 5 starts power supply to an analog processing part by the command of a system controller 4. Thus, the analog processing part 6 drives a CCD imager and starts the exposure and a digital processing part 8 decides a shutter speed for exposure adjustment and a parameter for white balance correction based on obtained video signals. In this case, the loads of analog and digital system power supply circuits 5 and 7 become high. Successively, a stroboscopic device 10 emits light, the analog processing part 6 performs the exposure, and when it is ended, current supply is stopped. In such a period when the loads are stable, the system controller 4 instructs residual amount detection to a battery voltage detection part 3 and a residual amount display part 9. Thus, the erroneous detection due to the load fluctuation is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery-remaining amount detection method used in an image pickup apparatus such as an electronic still camera or a video camera which uses a battery as a power source.

[0002]

2. Description of the Related Art In electronic devices that use batteries such as various batteries as a power source, for example, electronic still cameras and video cameras, the remaining battery level is always known and the user is informed of the remaining battery level. If the volume is low, a means to encourage battery replacement is essential.

In order to accurately execute this remaining amount notification,
It can be realized by constantly detecting the power supply voltage of the battery. Specifically, the output voltage of the battery is constantly compared with a predetermined threshold value, and when
The fact that the remaining amount is low is displayed on the display element provided in the camera or the electronic viewfinder.

[0004]

Generally, in electronic equipment,
Various operation modes are prepared, the state of the load through which the output current from the battery flows changes according to these operation modes, and the voltage of the battery also changes considerably in conjunction with this. For example, in the case of an electronic still camera, a state in which a strobe is emitted, a state in which a capacitor is charged in preparation for the next strobe emission, a state in which an analog processing unit including a drive circuit for a CCD imager is driven, CCD
There are various states such as a state in which a digital processing unit that digitally processes an image read from an imager is driven, a standby state in which none of the strobe, analog processing unit, and digital processing unit is inoperative. In the standby state, the load is light and the output voltage of the battery is kept high.On the contrary, during flash discharge, a large amount of current flows from the battery to the strobe at the same time as the discharge of the precharged capacitor, causing a high load state. The voltage drops sharply. Also, while the strobe capacitor is being charged, the capacitor acts as a load on the battery and the battery voltage drops.

As described above, when the battery voltage, which greatly varies depending on the operating state, is constantly compared with a predetermined threshold value, the voltage drops below the threshold value due to a temporary voltage drop even though the battery capacity is sufficient. Therefore, there is a fear of misjudging that the remaining amount is low.

[0006]

As a first means of the present invention, the output voltage of the battery is monitored only when the image pickup device is in a specific load state, and particularly during this specific load state. Is characterized by a period from the time when the shutter button is operated to instruct the start of shooting to the time when the strobe starts emitting light in synchronization with the shutter button. A second means is characterized in that the battery voltage is constantly monitored over the entire period except the strobe light emission period and the strobe capacitor charging period. Further, as a third means, when comparing the output voltage of the battery with a threshold value and notifying the comparison result, only when the comparison result by the comparison means is the same result continuously for a predetermined number of times, the comparison result is obtained. Is notified to the notification means.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is a block diagram of the essential parts of a digital still camera that is the device of this embodiment.

In the figure, 1 is a shutter button for a user to instruct the camera to take a picture, 2 is a battery which is detachably attached to the camera, and 3 is A / D by detecting a voltage value at an output stage of the battery. A battery voltage detection circuit 4 for converting and outputting receives an instruction from the shutter button 1 and an output of the battery voltage detection circuit 3, and controls driving of an analog power supply circuit 5 and a digital power supply circuit 6 described later and a battery. A system controller (syscon) that issues a display command to the remaining amount display unit 9.

An analog power supply circuit 5 receives an output of the battery 2 and performs processing of a video signal in an analog stage, such as a drive circuit of a CCD imager.
And a DC / DC converter for changing the battery voltage of 6 V to a plurality of DC voltage levels required for each part of the analog processing unit 6. This DC / DC converter Operation is system controller 4
Is controlled by

The digital power supply circuit 7 receives the output of the battery 2 and performs signal processing at a stage after digital conversion of the video signal taken in from the analog processing section 6 such as a color separation circuit and a signal compression circuit. It supplies a necessary drive voltage to the digital processing unit 8 to be executed, and is composed of a DC / DC converter for changing to a plurality of DC voltage levels required for each unit of the processing unit, like the analog power supply circuit 5.
The operation of this DC / DC converter is also controlled by the syscon 4.

The battery remaining amount display section 9 compares the battery voltage value detected by the battery voltage detection circuit 3 with a plurality of preset threshold values by the system controller 4, and is issued based on the comparison result. The display command is received and a corresponding display is performed. Once the display command is input and the corresponding state is displayed, the previous state is maintained until a new display command is input.

Reference numeral 10 denotes a strobe device having a strobe which emits light upon receiving a current supply from the battery-2 and a strobe drive circuit for controlling the drive of the strobe. The strobe device is supplied with current from the battery 2. In addition, a capacitor is provided in the drive circuit to enable a large current to be supplied when the flash fires, and when the flash fires, a light emission command is supplied from the syscon 4 to the drive circuit, and a current is supplied from the battery 2. The current discharged from the capacitor flows to the strobe, and the capacitor is charged according to an instruction from the syscon 4 when no light is emitted.

Next, the operation of each part of the block diagram of FIG. 2 and the change of the battery voltage will be described with reference to the timing chart of FIG. When the shutter button 1 of the camera in the standby state is pressed at the timing a, the analog system power supply circuit 5 starts supplying power to the analog processing unit 6 according to the command from the syscon 4, and at the same time, the digital system power supply circuit 7 performs digital processing. Power supply to the unit 8 is started.

By this power supply, the analog processing unit 6 is C
The CD imager is driven to start exposure, the video signal is taken out over a three-field period, and the digital processing unit 8 determines the shutter speed for exposure adjustment and white balance correction based on the obtained video signal. R
Various parameters necessary for photographing such as determination of gain of (red) and B (blue) signals are set. In this state, since the power is supplied to both the analog and digital power supply circuits 5 and 7 and the load becomes high, the battery voltage becomes lower than that in the standby state.

Next, when the timing b is reached, the syscon 4 issues a light emission command to the strobe device 10 to start the strobe light emission, and this light emission ends at the timing c.
In the analog processing unit 6, the CCD imager is exposed during the period from b to c, and subsequently the output by this exposure is read out as a formal video signal for one screen until the timing d, and the digital processing unit 8 reads it. At this point, the work of the analog processing unit 6 is completed, so that the analog power supply circuit 5 is deactivated and the current supply to the analog processing unit 6 is cut off.

Here, at the timings b to c, a large current required for light emission flows to the strobe device, so that the battery voltage drops significantly when the strobe device becomes extremely heavy and the strobe light emission ends. Then, when the timing d is reached again, the analog power supply circuit 5 is deactivated and the analog processing unit 6 is removed from the load, so the battery voltage rises by this amount.

Between timing d and g, 1
Video signals for the screen are subjected to known digital signal processing such as color separation, signal compression, and recording in a memory in the digital processing unit 8. However, during timing e to f, the current from the battery-2 is changed. In this way, the capacitor existing in the flash device 10 is charged in preparation for the next flash emission. Therefore, at timings d to e and f to g, only the digital processing unit 8 serves as a load and the battery voltage is kept relatively high. However, since the capacitor is added as a load at the start of charging at the timing e, the battery voltage suddenly increases. The charge gradually rises while the charge progresses.

When the timing g is reached, the digital processing unit 8 completes writing the video signal for one screen in the memory,
Since the work in the digital processing unit 8 is also completed, the digital power supply circuit 7 is deactivated and the current supply to the digital processing unit 8 is cut off, and the digital processing unit 8 is removed from the load, so that the battery is removed. The voltage returns to the standby state. After that, each time the shutter button 1 is pressed, the series of processes described above are repeated, and the battery voltage also repeats the fluctuation shown in FIG.

Next, the detection and display of the remaining battery level in the system controller 4 will be described with reference to the flowchart of FIG. When the shutter button 1 is turned on in the standby state, the process proceeds from step 60 to step 61, both power supply circuits 5 and 7 are activated, and power supply to both processing units 6 and 8 is started. As described above, various parameters are actually set by using the output obtained by imaging several fields of the CCD imager. At the same time, the syscon 4 reads the battery voltage value from the battery voltage detection circuit 3 ( In step 62), the remaining battery amount is calculated by comparing with a preset threshold value (step 63).

Here, as the threshold value, a value that can be taken under the same load condition of the battery voltage when the remaining amount is 50% is taken as the threshold value R1, and under the same load condition of the battery voltage when the remaining amount is 10%. The obtained value is set in advance as a threshold value R2, and the value that the battery-voltage can take in the same load state when the remaining amount is 5% is set in advance as an actual measurement value, and in the relationship between the battery-voltage value V and each threshold value. , R1 ≦ V, it is determined that the first remaining amount state has a sufficient remaining amount, and if R2 ≦ V <R1, it is determined that the second remaining amount state is less than half, and R
When 3 ≦ V <R2, it is determined that the remaining amount is less than 10% and the remaining amount is considerably small, and when V <R3, the remaining amount is close to zero and the fourth remaining amount state. judge.

When it is determined in any of the four types of remaining amount states in this manner, whether or not the result of the first determination, that is, the determination result obtained when the shutter button 1 is pressed one time before, coincides. Is judged (step 64), and if both match, the judgment is regarded as accurate and valid, and the remaining amount state corresponding to this judgment result is instructed to the remaining amount display section 9 and the result is received. Then, the remaining amount display section 9 identifies and displays the corresponding remaining amount state (step 65). If the result of the previous determination does not match, the new determination result is considered to be unreliable and invalid, and no new display instruction is given.

When a series of judgments are completed in this way, it is effective,
The previous determination result is updated with the new determination result regardless of invalidity. Then, it is determined whether or not it matches the new determination result obtained when the shutter button 1 is pressed next time.

Therefore, when the battery voltage temporarily fluctuates and an error occurs in the determination result, the same determination result cannot be obtained continuously, and therefore the remaining amount is displayed due to this incorrect determination result. Not done.

Then, in the above-mentioned order, the strobe lights are emitted (step 66), and when the image acquisition by the CCD imager is completed, the power supply to the analog processing section is blocked (step 67), and all digital signals are further supplied. When the signal processing is completed, the photographing is completed, and the recording of the video signal for one screen in the memory is completed, the power supply to the digital processing unit 8 is blocked (step 68).

Thus, the detection timing of the battery-voltage value used in the calculation of the battery-remaining amount is the timing a in consideration of the fact that the voltage greatly changes depending on the load state of the supply destination of the battery output current. Since it is executed only from the timing to the timing b, the load is kept constant when the battery-voltage is detected, and the voltage is constantly detected in the same state, so that there is no influence of load fluctuation. Further, the remaining amount state is not considered valid unless the two consecutive determination results match, so even if an erroneous detection occurs due to a temporary voltage fluctuation, If it is a proper one, it is invalidated.

In the above embodiment, the battery-voltage detection timing is set between the timings a and b.
The present invention is not limited to this, and the same effect can be obtained at timings c to d, d to e, and f to g as long as the load is constant. a ~
It takes a shorter time than b, and f to g vary in time depending on the charging status of the capacitor. Considering these things, it is optimal to execute a to b.

Further, in the above embodiment, in order to recognize the determination result as valid, the determination result is valid only when the determination results are the same twice consecutively, but it is not particularly limited to two times. Of course, if the response is delayed three times or four times, for example, a response delay occurs, but it goes without saying that more accurate determination can be performed.

In the first embodiment, the operation of the shutter button 1 digitally processes a still image for one screen and stores it in a memory such as a flash memory. When the storage of one still image data is completed, the shutter is released. Until the button is operated again, the description has been given of the camera in which both the analog processing unit 6 and the digital processing unit 8 are in the inactive standby state.
In recent years, a method in which an LCD monitor is attached to the electronic still camera itself, an image pickup screen is displayed on the monitor, and the LCD monitor is used as an electronic viewfinder has been favored.

In such a camera with an LCD monitor, the analog and digital processing sections continue to capture images and perform signal processing and display still images sequentially obtained on the LCD monitor one after another even in a standby state where the shutter button 1 is not operated. Therefore, even in this standby state, the analog power supply circuit and the digital power supply circuit always consume power, and the remaining battery level is constantly reduced.

Therefore, as in the first embodiment, when the shutter button is operated, the remaining amount is detected during the period until the strobe emits light, and the standby state is continued without operating the shutter button. The remaining amount is not detected during the period, and the remaining amount display actually retains the result detected when the shutter button was last operated, even though the remaining amount is actually decreasing. There will be a gap between the state and the display.

Therefore, in a camera with an LCD monitor, it is preferable that the remaining amount is always detected and the detection result is displayed. However, when the strobe light is emitted and the condenser for the strobe is charged, the load on the battery is temporarily increased. As it gets bigger, the battery voltage drops significantly. Therefore, a second embodiment will be described with reference to FIG. 4, in which the remaining amount is constantly detected during the period excluding these two states.

FIG. 4 is a block diagram of the second embodiment. The same parts as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. FIG.
The difference from the LCD monitor 11 is that an LCD monitor 11 and an LCD power supply circuit 12 are added.
An image obtained by signal processing in the digital processing unit 8 is displayed on the LCD, and the LCD power supply circuit 12 receives the output of the battery 2 and supplies a necessary drive voltage to the LCD monitor 11. The LCD power supply circuit 12 is a DC-D like the analog and digital power supply circuits 5 and 7.
Although it is composed of a C converter, it always maintains an operating state in order to keep the LCD monitor 11 in a display state.

The change in the battery voltage of the LCD monitor camera will now be described with reference to the timing chart of FIG. 5. Even in the standby state before the timing a, which is the pressing timing of the shutter button 1, as described above. Since the analog and digital processing units 5 and 7 maintain the operating state and analog and digitally process the image pickup signal captured from the CCD imager and supply it as image data to the LCD monitor 11, the battery voltage is an analog system. And digital power supply circuits 5 and 7
Acts as a load, and the voltage becomes lower than that in the first embodiment. In this standby state, the image data obtained by the signal processing is created for displaying on the LCD monitor 11, and the image processing as the storage in the flash memory or the image compression as the preprocessing of this storage is performed by the digital processing unit. It is not executed in 8.

When the shutter button 1 is pressed at the timing a, the analog and digital power supply circuits 5 and 7 continue to be in the operating state, and thereafter, the same voltage fluctuation as in the first embodiment is maintained until the timing g. Occurs. That is, the battery voltage greatly drops during the timings b to c at which the strobe device 10 is in the light emitting state and the timings e to f, which are the charging periods of the capacitors for supplying a large current of the strobe device 10, and the analog processing is performed at the timing d. After the image pickup signal for one screen picked up by the unit 6 is supplied to the digital processing unit 8, new image pickup is temporarily performed until the image data based on this signal is image-compressed and stored in the flash memory. Since the analog power supply circuit 5 is deactivated, the load on the analog system becomes lighter, the battery voltage rises, and the storage of the image data in the flash memory is completed.
Until then, this state is continued, and by returning to the standby state at the timing g, the analog power supply circuit 5 is activated again, so that the battery voltage drops slightly. Since most of the time required for the signal processing in the digital processing unit 7 is processing related to image compression, the analog processing unit 6
LCD monitor 1 while new image is not taken by
In 1, the image data for one screen before compression is repeatedly displayed.

When the standby state is resumed at the timing g when the storage of one image data in the flash memory is completed, the image data sequentially captured until the next shutter button 1 is pressed is successively displayed on the LCD monitor 11. It is projected.

The system controller 4 is a battery voltage detection circuit 3
The battery remaining amount detection is performed by comparing the battery voltage from the battery voltage with a threshold value, but the period of b to c during which the strobe device 10 is in the light emitting state and e to f during which the capacitor for the strobe device 10 is in the charging state. The remaining amount detection operation is stopped in the periods, and the remaining amount detection is always continued in all periods except these periods.

Here, whether the strobe device 10 is in the light emission period is determined by the syscon 4 by issuing a light emission control signal, which is a light emission command, a predetermined time after the shutter button 1 is pressed by the syscon 4 itself. It can be easily realized because there is no problem.

On the other hand, during the charging period of the capacitor, there is no problem because the charging is started according to the instruction from the system controller, but the charging time is not constant depending on the light emission amount of the strobe device 10. Therefore, the charging voltage of the capacitor of the strobe device 10 is supplied to the syscon 4 side as a digital value of the charging voltage data, and the syscon 4 compares the charging voltage data with a predetermined value. It is possible to determine the charging period by recognizing that the battery is being charged without being fully charged.

Specifically, as shown in FIG. 6, the voltage across the capacitor C is divided by resistors R1 and R2, and then the divided voltage is formed by an A / D converter. It is configured to be digitized by 30 and supplied to the syscon 4 as charging voltage data. In FIG. 6, reference numeral 31 is a trigger circuit for applying a high voltage for starting to the discharge tube 32 in response to a light emission control signal from the syscon 4.
33 is a thyristor connected in series to the discharge tube 32. When the syscon 4 instructs strobe emission, a high voltage is applied to the discharge tube 32 by the trigger circuit 31, and at the same time a gate current is applied to the gate of the thyristor 33. , The output current from the capacitor C conducts the discharge tube 32 and the thyristor 35, and operates so that the discharge tube is in a discharge state. Further, 34 is a switch connected between the output stage of the battery and the capacitor C, which is controlled according to the switching control signal from the syscon 4, and the switching control signal is switched only in the period of timings b to c and e to f. 34 is closed.

As in the first embodiment, the remaining amount detection result is configured to be recognized as correct only when the results of a plurality of times are continuously the same, and the strobe light emission period is as shown in FIG. Although it was described as long for convenience of explanation, it is actually very short, and the detection result is so short that it does not become the same multiple times. It goes without saying that the detection timing interval can be set so that it can be stopped automatically.

[0041]

As described above, according to the present invention, since the detection timing of the battery voltage necessary for detecting the remaining battery amount is set to the period during which the load is stable, erroneous detection due to load fluctuation is prevented.

Further, by omitting from the detection timing only the period during which the battery voltage greatly drops due to the fluctuation of the load related to the strobe, it is possible to suppress the erroneous detection even when the remaining amount detection needs to be constantly executed. Become.

Further, if the measurement results of the remaining amount calculated from the battery voltage do not match continuously for a predetermined number of times, it is considered invalid, so that even if a voltage drop occurs momentarily due to load fluctuation or the like. , The measurement result in this case becomes invalid, and the erroneous detection of the remaining amount can be prevented.

[Brief description of drawings]

FIG. 1 is a timing chart showing changes in battery voltage according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a main part of the first embodiment of the present invention.

FIG. 3 is a flowchart of the first embodiment of the present invention.

FIG. 4 is a block diagram of an essential part of a second embodiment of the present invention.

FIG. 5 is a timing chart showing changes in battery voltage according to the second embodiment of the present invention.

FIG. 6 is a diagram illustrating the structure of a flash device according to a second embodiment of the invention.

[Explanation of symbols]

 1 Shutter Button 2 Battery 3 Battery Voltage Detection Circuit 4 System Controller 9 Remaining Amount Display 10 Strobe Device 11 LCD Monitor

Claims (4)

[Claims] 1. A battery for supplying a current to the image pickup device, and a remaining amount detection means for detecting the remaining amount of the battery based on the output voltage of the battery when the image pickup device is in a specific load state. A battery remaining amount detecting device comprising notifying means for notifying the output of the remaining amount detecting means. 2. The electronic device includes a shutter button for instructing start of photographing, and a strobe that emits light in synchronization with the shutter button, and when in the specific load state, the electronic device is operated after operating the shutter button. 2. The battery remaining amount detecting device according to claim 1, wherein the period is a period until the strobe starts emitting light. 3. A battery for supplying a current to the image pickup device, and a capacitor charged by the battery output,
A strobe that emits light using the capacitor output and the battery output, and the battery that is always based on the output voltage of the battery during a period excluding a period in which the strobe is in a light emitting state and a period in which the capacitor is in a charging state. A battery remaining amount detecting device comprising a remaining amount detecting means for detecting the remaining amount of the remaining amount and a notifying means for notifying the output of the remaining amount detecting means. 4. A battery for supplying a current to the image pickup device, a comparing means for comparing the output voltage of the battery with a threshold value, and an informing means for informing the output of the remaining amount detecting means, and the comparison result by the comparing means. The battery remaining amount detecting device is characterized in that the comparison result is notified to the notifying means only when is continuously the same for a predetermined number of times.