JP2004364418A - Power circuit and camera device equipped with the power circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power circuit that can prevent an adverse effect such as an operation stop of a device caused by a load variation at the start of motor drive while sharing a power supply in a control means and in a motor, and can achieve power saving, and to provide a camera device equipped with the power circuit. <P>SOLUTION: The power circuit comprises a DC-DC converter 86 that feeds power to both a zoom drive motor 31 and a system controller 50, and a drive-voltage control means that controls a motor drive voltage applied to the zoom drive motor 31 from the DC-DC converter 86 when power is fed to the zoom drive motor 31. The drive-voltage control means sets the motor drive voltage at the start of voltage application lower than a motor drive voltage value at a normal time after a prescribed time elapses from the start of the application, and suppresses the lowering of the control means drive voltage applied to the system controller 50 from the DC-DC converter 86. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power supply circuit having power supply means for supplying power to both a motor and a control means, and to a camera device provided with the power supply circuit.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there has been known an apparatus using a power supply circuit having a function of transforming an input voltage according to each unit supplied when power is supplied (for example, Patent Document 1). In the digital camera described in Patent Document 1, camera power (power) is input from a battery to a DC / DC converter and supplied to the inside of the digital camera.
[0003]
On the other hand, a digital camera usually monitors the voltage input from the DC / DC converter to the system controller in order to stop the operation of the digital camera when the battery becomes low. And a power supply voltage monitoring unit for outputting a reset signal.
[0004]
[Patent Document 1]
JP 2003-87642 A
[Problems to be solved by the invention]
In a digital camera, for example, when a zoom operation is instructed by a user, a constant motor drive voltage is applied to the zoom drive motor. At this time, the current consumption of the zoom drive motor is as shown in FIG. A large peak is generated at the start of the zoom operation (at the start of application) due to a change in the load of the motor, and after that, it goes down to a steady state after a certain period of time.
[0006]
On the other hand, in a digital camera, it is necessary to supply power to each unit such as a DC motor such as a zoom drive motor, a system controller as control means, a CCD, and a monitor. Of the power supplied to these units, In some cases, the power supplied to the DC motor and the power supplied to the system controller are shared to reduce the cost.
[0007]
In a digital camera using a common power supply for such a DC motor and a system controller, when a large current consumption peak occurs in the motor as described above, unnecessary power is consumed and the voltage input to the system controller is reduced. There is a problem that the operation of the digital camera is stopped when the power supply voltage monitoring unit detects the drop.
[0008]
Also, in a DC motor such as a zoom drive motor, ripple occurs in the current. That is, as shown in FIG. 6, the DC motor includes a coil 91 that rotates around a shaft (not shown) and a commutator (not shown) connected to the coil 91 at an end of the shaft. Further, two magnets 93 such as a permanent magnet and an electromagnet are provided outside the coil 91 to generate a magnetic field, and a brush (not shown) is fixed so as to be in contact with the commutator in order to flow the current i. Is provided.
[0009]
In the DC motor having such a configuration, when a current i flows through the coil 91 via the commutator in the magnetic field generated by the magnet 93, a force F is generated according to Fleming's left-hand rule. Due to this force F, the coil 91 rotates about the axis and acts as a motor. However, when the coil 91 is at a position perpendicular to the magnet 93, the rotation stops, so that the coil 91 is moved to the vertical position. At one time, the direction of the current i is reversed by the commutator and the brush so that the coil 91 always rotates in the same direction. As described above, in the DC motor, it is necessary to switch the direction in which the current i flows, and at the time of the switching, ripple occurs in the current i as shown in FIG.
[0010]
When such a ripple overlaps with the peak current consumption at the start of the zoom operation, the current consumption of the motor further increases, and in the conventional digital camera, the problem of stopping the operation is more likely to occur.
[0011]
SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and uses a common power source for the control means and the motor, but also for stopping the operation of the apparatus due to a load change at the start of motor drive (at the start of application). It is an object of the present invention to provide a power supply circuit capable of preventing adverse effects and saving power, and a camera device including the power supply circuit.
[0012]
[Means for Solving the Problems]
In order to solve such a problem, an invention according to claim 1 is a power supply that supplies power to both a motor that drives a driven member and a control unit that outputs an instruction signal based on an external input. Supply means, and drive voltage control means for controlling a motor drive voltage applied to the motor from the power supply means when power is supplied to the motor, wherein the drive voltage control means is constant from the start of application. The value of the motor drive voltage at the start of application is set lower than the value of the motor drive voltage in a steady state after a lapse of time, and the control means drive voltage applied to the control means from the power supply means is set. It features a power supply circuit that suppresses the drop.
[0013]
According to the present invention, it is possible to prevent the control means and the motor from using the same power supply, and to prevent an adverse effect such as an operation stop of the apparatus due to a load change at the start of motor drive (at the start of application), and to save power. Electricity can be achieved.
[0014]
According to a second aspect of the present invention, in the first aspect, the motor is a power supply circuit that is a DC motor.
[0015]
ADVANTAGE OF THE INVENTION According to this invention, even if the ripple overlaps the peak current consumption of the motor at the start of application and the load fluctuation on the motor increases, it is possible to prevent adverse effects such as operation stop of the device and to save power. be able to.
[0016]
According to a third aspect of the present invention, in the first or second aspect, the value of the motor drive voltage at the start of the application is a voltage value corresponding to the electric power required for operating the motor. It is characterized by a certain power supply circuit.
[0017]
ADVANTAGE OF THE INVENTION According to this invention, the electric current which flows into a motor decreases and the torque which rotates a motor weakens, and as a result, the problem that a motor itself does not move or the speed of motor operation can be prevented can be prevented. .
[0018]
According to a fourth aspect of the present invention, there is provided a camera device including the power supply circuit according to any one of the first to third aspects.
[0019]
According to this invention, the effects of the invention described in any one of claims 1 to 3 can be obtained in a camera device.
[0020]
The invention according to claim 5 is the camera device according to claim 4, wherein the driven member is a zoom lens, and the motor is a zoom drive motor for driving the zoom lens.
[0021]
According to this invention, the same effect as that of the fourth aspect can be obtained.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0023]
FIG. 1 shows a digital camera as a camera device according to an embodiment of the present invention. At the center of the front 2 of the digital camera 1, there is provided a lens barrel unit 3 for inputting photographing light. Above the lens barrel unit 3, a strobe light emitting unit 4 for emitting light toward a subject and an auto focus (AF) In this case, there are provided a distance measuring unit 5 for measuring the distance to the subject and an optical finder 6 for allowing the user to visually check the photographing range and the like. Further, below the optical finder 6, a remote control light receiving unit 7 for receiving an optical signal from a remote control not shown is provided.
[0024]
On an upper surface 8 of the digital camera 1, a release shutter 9, a mode dial 10 for switching a shooting mode, and a sub LCD 11 for displaying the number of shootable images and the like are provided. Also, on the back surface 12 of the digital camera 1, an LCD 13 for displaying a photographed image and the like, an AF-LED 14 for indicating an AF state at the time of photographing, a strobe LED 15 for indicating a strobe charging state, and a switch for turning on / off a power supply. A power switch 16 and an operation button unit 17 for externally performing operation instructions and various settings are provided. The operation button unit 17 includes zoom buttons 18a and 18b for performing zoom settings. The AF-LED 14 and the strobe LED 15 are also used for other display purposes such as indicating that the external extended memory 21 is being accessed. Note that the release shutter 9, the mode dial 10, the power switch 16, and the operation button unit 17 are collectively referred to as an operation unit 19.
[0025]
Further, on the side surface 20 of the digital camera 1, there is provided an external expansion memory mounting portion 22 to which an external expansion memory 21 (see FIG. 2) such as a memory card is removably mounted. The digital camera 1 also has a battery loading unit (not shown) in which a battery 23 (see FIG. 2) is set detachably.
[0026]
FIG. 2 is a block diagram illustrating a schematic configuration of the digital camera 1.
[0027]
The lens barrel unit 3 includes a zoom optical system 32 including a zoom lens 30 as a driven member for capturing an optical image of a subject and a zoom drive motor 31 as a motor, and a focus optical system including a focus lens 33 and a focus drive motor 34. A system 35, an aperture unit 38 having an aperture 36 and an aperture motor 37, a mechanical shutter unit 41 having a mechanical shutter 39 and a mechanical shutter motor 40, and a zoom drive motor 31, a focus drive motor 34, an aperture motor 37, And a motor driver 42 for driving a DC motor 43 such as a mechanical shutter motor 40.
[0028]
The CCD 45 is a solid-state imaging device that photoelectrically converts (converts an analog signal) an optical image captured from the lens barrel unit 3. The F / E (front end) -IC 46 includes a CDS 47 that performs correlated double sampling for removing image noise, an AGC (Auto Gain Controller) 48 that performs gain adjustment, an A / D 49 that performs digital signal conversion, and And a TG 52 that receives a vertical synchronizing signal (VD signal) and a horizontal synchronizing signal (HD signal) from the CCD1 signal processing block 51 of the system controller 50 and generates a drive timing signal.
[0029]
The system controller 50 as a control means performs white balance setting and gamma setting on digital image data input from the CCD 45 via the F / E-IC 46 and controls the CCD 1 which outputs the VD signal and the HD signal as described above. A block 51, a CCD2 signal processing block 53 that converts the data into luminance data and chrominance data by filtering, and a control program stored in a ROM 65, which will be described later, based on signals input from the remote control light receiving unit 7 and the operation unit 19. A CPU block 54 for controlling the operation of each part of the digital camera 1 such as the motor driver 42 and the CCD 45; a local SRAM 55 for temporarily storing data and the like necessary for this control; and a USB for performing USB communication with an external device such as a PC. Block 56 and a serial device such as a PC. Block 57 for performing JPEG compression and decompression, a JPEG-CODEC block 58 for performing JPEG compression and decompression, a RESIZE block 59 for enlarging / reducing the size of image data by interpolation, and an external display device such as the LCD 13 or TV for displaying image data. A TV signal display block 60 for converting a video signal to a video signal to be displayed on a TV, and an external expansion memory block 61 for controlling the external expansion memory 21 such as a memory card for recording captured image data.
[0030]
The ROM 65 stores a control program described in a code readable by the CPU block 54, data necessary for controlling the CPU block 54, and the like. Here, as the data necessary for the control, the value of the initial drive voltage V1, the value of the steady drive voltage V2, and the value of the fixed time T are already recorded in the ROM 65. The initial drive voltage V1 is a motor drive voltage lower than usual applied to the zoom drive motor 31 at the start of the zoom operation (at the start of application), and the steady drive voltage V2 is after a lapse of a predetermined time T from the start of the zoom operation (at the start of application). Is a normal motor drive voltage applied to the zoom drive motor 31 at the time of steady state. The initial drive voltage V1 is lower than the steady-state drive voltage V2, but at least within a range in which the zoom drive motor 31 can operate, that is, within a range of voltage values corresponding to the power required for the zoom drive motor 31 to operate. Is set to If the initial drive voltage V1 is too low, the current flowing through the zoom drive motor 31 decreases, and the torque for rotating the zoom drive motor 31 becomes weak. As a result, the zoom drive motor 31 itself does not move or the speed of the zoom operation is reduced. This is because there is a problem that the operation is delayed.
[0031]
Further, although the fixed time T is set in advance, the time required for the zoom operation can be changed by arbitrarily changing the fixed time T.
[0032]
When the power of the digital camera 1 is turned on by operating the power switch 16, the control program stored in the ROM 65 is loaded into a main memory (not shown), and the CPU block 54 controls the operation of each unit of the digital camera 1 according to the control program. In addition to the control, data necessary for the control is temporarily stored in the RAM 66 and the local SRAM 55. If a rewritable flash ROM is used as the ROM 65, it is possible to change a control program, parameters necessary for control, and the like, and it is possible to easily upgrade functions.
[0033]
The SDRAM 67 temporarily stores image data when various processes are performed in the system controller 50. The image data to be stored is, for example, “RAW-RGB image data” or a CCD2 signal in a state where white balance setting and gamma setting are performed by the CCD1 signal processing block 51 from the CCD 45 via the F / E-IC 46. “YUV image data” in a state where conversion into luminance data / color difference data has been performed in the processing block 53, “JPEG image data” in a state where JPEG compression or the like has been performed in the JPEG-CODEC block 58, and the like.
[0034]
The built-in memory 68 can store captured image data even when the external expansion memory 21 such as a memory card is not mounted on the external expansion memory mounting section 22.
[0035]
The LCD driver 69 drives the LCD 13 and converts a video signal output from the TV signal display block 60 into a signal to be displayed on the LCD 13. Thus, the LCD 13 allows the user to monitor the state of the subject before shooting, check the shot image, and view the image data recorded in the external extended memory 21 or the built-in memory 68. Has become.
[0036]
The video AMP 70 is an amplifier that converts the video signal output from the TV signal display block 60 into a 75Ω impedance. The video jack 71 is a jack for connecting to an external display device such as a TV. The USB connector 72 is a connector for making a USB connection with an external device such as a PC. The serial driver circuit 73 is a circuit for converting the output signal of the serial block 57 into a voltage for performing serial communication with an external device such as a PC. The RS-232C connector 74 is a connector for performing serial connection with an external device such as a PC. It is.
[0037]
The sub CPU 75 is a CPU in which a ROM, a RAM, and the like are built in one chip, and outputs an output signal from the remote control light-receiving unit 7 and the operation unit 19 to the CPU block 54 as user operation information. The state of the digital camera 1 is converted into a control signal for the sub LCD 11, the AF-LED 14, the strobe LED 15, the buzzer 76, and the like, and is output. The LCD driver 77 is a drive circuit that drives the sub LCD 11 based on an output signal from the sub CPU 75.
[0038]
The audio recording unit includes a microphone 79 to which the user inputs an audio signal, a microphone AMP 80 to amplify the input audio signal, and an audio recording circuit 81 to record the amplified audio signal. The audio reproduction unit includes an audio reproduction circuit 84 that converts a recorded audio signal into a signal to be output from a speaker 83 described later, and an audio AMP 85 that amplifies the converted audio signal and drives the speaker 83. And a speaker 83 for outputting an amplified audio signal.
[0039]
The power supply circuit of the digital camera 1 includes a DC / DC converter (power supply means) 86 and a system controller (drive voltage control means) 50. The system controller 50 controls the operation of the power supply circuit. Based on the control of the system controller 50, the camera power is supplied from the battery 23 via the DC / DC converter 86 to the zoom drive motor 31, the focus drive motor 34, and the aperture motor 37. , A DC motor 43 such as a mechanical shutter motor 40, and the like, a system controller 50, a CCD 45, an LCD 13, an F / E-IC 46, and other components of the digital camera 1. The DC / DC converter 86 has a function of changing the voltage in accordance with each section that supplies the input voltage from the battery 23. Of the power supplied from the DC / DC converter 86 to each section, the power supplied to the DC motor 43 And those supplied to the system controller 50 are common.
[0040]
A power supply voltage monitoring unit 87 is provided between the DC / DC converter 86 and the system controller 50, and monitors the control unit drive voltage input from the DC / DC converter 86. A reset signal is output to stop the operation of the system controller 50.
[0041]
In the digital camera 1 configured as described above, for example, when a zoom operation instruction is performed by the zoom buttons 18a and 18b of the operation unit 19, the system controller 50 transmits the instruction signal from the operation unit 19 as shown in FIG. First, a control signal is output to the DC / DC converter 86 so that the initial drive voltage V1 recorded in the ROM 65 is applied to the zoom drive motor 31 (S2). Next, a time count is performed from the time of output of the control signal (at the start of application), and based on the time count, the system controller 50 outputs a control signal (the initial drive voltage V1 is applied to the zoom drive motor 31). It is determined whether or not a predetermined time T has elapsed (from the start) (S3). In step S3, when the system controller 50 determines that the predetermined time T has not elapsed, the process returns to step S3 again. On the other hand, when the system controller 50 determines that the predetermined time T has elapsed, the steady drive voltage V2 newly recorded in the ROM 65 is newly stored. Is output to the DC / DC converter 86 so that is applied to the zoom drive motor 31 (S4).
[0042]
By performing such control for the zoom operation, the zoom drive motor 31 is driven by the initial drive voltage V1 lower than usual from the start of the zoom operation to a certain time T, and thereafter (after the certain time T has elapsed). It is driven by a steady driving voltage V2 which is a normal voltage value. As a result, as shown in FIG. 4, the current consumption peak at the start of the zoom operation is suppressed to be low.
[0043]
In the digital camera 1 according to the present embodiment, the initial drive voltage V1 is set lower than the steady drive voltage V2, so that the system controller 50 and the DC motor 43 share the same power supply but have a load at the start of motor drive. It is possible to prevent adverse effects such as a stop of the operation of the digital camera 1 due to the fluctuation (system down). That is, the digital camera 1 can suppress the current consumption peak (abrupt current fluctuation) at the start of the zoom operation lower than in the past, and accordingly suppress the drop of the control unit driving voltage applied to the system controller 50. it can. Therefore, the operation of the system controller 50 is not stopped by the power supply voltage monitoring unit 87 due to the voltage being equal to or lower than the fixed value, and a stable system can be constructed.
[0044]
Further, since the current consumption peak at the start of the zoom operation can be suppressed low, the power consumption of the digital camera 1 as a whole can be reduced, and power saving can be achieved. In particular, since digital cameras are often used outdoors, once power is consumed, it is often difficult to replenish the power during use. Therefore, there is a demand to keep the drive time as long as possible with limited power, and the digital camera 1 according to the present embodiment can meet such a demand.
[0045]
Note that the present invention is not limited to the above-described embodiment. For example, in the present embodiment, the digital camera 1 including the power supply circuit has been described as an example, but the present invention is not limited to this. Any camera device having a power supply circuit may be used.
[0046]
Further, in the present embodiment, the motor drive voltage applied to the zoom drive motor 31 is divided into two, an initial drive voltage V1 and a steady drive voltage V2, and the value of the motor drive voltage applied to the zoom drive motor 31 is determined. Although the increase is performed in two stages, the increase is not limited to two stages, and may be increased in stages from the initial drive voltage V1 to the steady drive voltage V2 in a plurality of stages such as three stages and four stages. Further, instead of stepping up from the initial drive voltage V1 to the steady drive voltage V2 stepwise, the voltage may be gradually increased gradually.
[0047]
In this embodiment, the drive voltage of the zoom drive motor 31 has been described as being increased step by step. However, the present invention is not limited to the zoom drive motor 31, and the focus drive motor 34, the aperture motor 37, the mechanical shutter motor 40 Or the like.
[0048]
【The invention's effect】
Since the power supply circuit according to the present invention and the camera device including the power supply circuit are configured as described above, the control unit and the motor use the same power supply, but the device caused by the load fluctuation at the start of the motor drive. Can be prevented from being adversely affected, such as an operation stop, and power can be saved.
[Brief description of the drawings]
1A and 1B show a digital camera according to an embodiment of the present invention, wherein FIG. 1A is a front view, FIG. 1B is a plan view, and FIG. 1C is a rear view.
FIG. 2 is a block diagram illustrating a schematic configuration of the digital camera in FIG. 1;
FIG. 3 is a flowchart showing a control flow of a system controller regarding a zoom operation in the digital camera of FIG. 1;
4 is a graph showing a relationship between a drive time and a drive voltage and a relationship between a drive time and a current consumption in a zoom drive motor when zoom operation control of the digital camera in FIG. 1 is performed.
FIG. 5 is a graph showing the relationship between drive time and drive voltage and the relationship between drive time and current consumption in a zoom drive motor of a conventional digital camera.
FIG. 6 is a schematic diagram of a DC motor for explaining the operation principle of the DC motor.
FIG. 7 is an enlarged graph showing the relationship between driving time and current consumption of a zoom drive motor at the start of a zoom operation in a conventional digital camera.
[Explanation of symbols]
1 Digital camera (camera device)
30 Zoom lens (driven member)
31 Zoom drive motor (motor)
50 System controller (control means, drive voltage control means)
86 DC / DC converter (power supply means)
V1 Initial drive voltage V2 Steady drive voltage T Constant time

Claims (5)

Power supply means for supplying power to both a motor for driving the driven member and a control means for outputting an instruction signal based on an external input; and when the power is supplied to the motor, the power supply means Drive voltage control means for controlling a motor drive voltage applied to the motor,
The drive voltage control means sets the value of the motor drive voltage at the start of application to be lower than the value of the motor drive voltage at the start of application after a certain time has elapsed from the start of application, and A power supply circuit for suppressing a drop in a control unit drive voltage applied to the control unit. The power supply circuit according to claim 1, wherein the motor is a DC motor. 3. The power supply circuit according to claim 1, wherein the value of the motor drive voltage at the time of starting the application is a voltage value corresponding to electric power required for operating the motor. 4. A camera device comprising the power supply circuit according to any one of claims 1 to 3. The camera device according to claim 4, wherein the driven member is a zoom lens, and the motor is a zoom drive motor that drives the zoom lens.

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