JP2005275108A - Apparatus equipped with flash - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus equipped with a flash capable of preventing a brightness change on a display screen due to a brightness change of a back light during charging. <P>SOLUTION: The duty ratio of a pulse train power is controlled in accordance with a voltage monitored by a battery voltage monitoring part, and instead of DC power, the pulse train power is supplied to the back light 130, and the back light 130 is poorly lighted with the brightness lower than that when the DC power is supplied. The brightness change on the display screen due to the brightness change of the back light at the time of charging is prevented in such the way. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a device equipped with a flash that is equipped with a battery and operates by receiving power from the battery.

  Some devices equipped with a battery and operated by receiving power from the battery include a flash that emits a flash. The flash is provided with a main capacitor. Electric power stored in the main capacitor is discharged, and flash light is emitted. When the flash light is emitted in this manner, the power of the main capacitor is discharged, so that the main capacitor is charged by the charging device in response to the supply of power from the battery. However, if a large charging current is applied when the voltage of the battery is low, a large load is applied to the battery, and the device may malfunction.

  Therefore, a technique for controlling the magnitude of the charging current according to the battery voltage is disclosed in order to prevent malfunction of the device due to a decrease in the battery voltage (see, for example, Patent Document 1 and Patent Document 2).

  By the way, recently, many devices equipped with such a flash have a liquid crystal panel as a display screen in order to inform the user of the operation explanation and the selected photographing mode. In order to make the display screen of the liquid crystal panel easier to see, many backlights are provided on the back side of the liquid crystal panel, and power from the battery is also supplied to the backlight.

In such a device, charging may be performed while the backlight is turned on after flashing with a flash. At this time, even if the charging current is controlled by the above technique, the battery voltage may fluctuate at the start of charging, the backlight luminance may fluctuate, and the panel surface may become darker or brighter. Also, if the battery is used for a long time, the battery voltage itself will decrease, and it will not stay bright or dark, the power supply from the power supply will be cut off, and the display screen will turn black. It may even end up.
JP 2000-347255 A Japanese Patent Laid-Open No. 2-93442

  An object of the present invention is to solve the above-described problems and to provide a device including a flash that prevents a change in luminance of a display screen due to a change in luminance of a backlight during charging.

An apparatus equipped with a flash of the present invention that achieves the above object is an apparatus equipped with a flash that is equipped with a battery and operates by receiving power supply from the battery.
A flash having a main capacitor, a charging circuit that boosts the voltage from the battery to charge the main capacitor, and a light emitting unit that emits a flash by receiving the power stored in the main capacitor;
A display unit having a display screen and a backlight for illuminating the display screen from the back, and performing display on the display screen;
A battery voltage monitoring unit that monitors the voltage of the battery, and when the main capacitor is scheduled to be charged when the backlight is turned on, supply power corresponding to the voltage of the battery to the backlight. The lighting control unit for lighting the backlight is provided.

  According to the device including the flash of the present invention, when the main capacitor is scheduled to be charged, the lighting control unit supplies power according to the voltage of the battery to light the backlight.

  In this way, when it is assumed that a large current flows through the main capacitor due to charging and the voltage of the battery fluctuates, by supplying power according to the voltage of the battery in advance and turning on the backlight, Changes in the brightness of the backlight during charging are prevented.

Here, a charging voltage monitoring unit for monitoring the voltage of the main capacitor is provided,
The lighting control unit supplies power to the backlight in accordance with the voltage of the battery and the voltage of the main capacitor when the main capacitor is scheduled to be charged when the backlight is turned on. Thus, the backlight is preferably turned on.

  In this way, when the backlight is turned on by supplying power corresponding to the charging voltage detected by the charging voltage monitoring unit in addition to the voltage of the battery, the current flowing through the main capacitor increases and the voltage drop of the battery decreases. Even if it becomes larger, the luminance change of the backlight during charging is prevented. For this reason, the brightness of the display screen does not change, and the display screen is easy to see.

  Further, the backlight is lit by receiving power supplied from a pulse train, and the lighting control unit supplies the backlight by controlling the duty ratio of the pulse train power supplied to the backlight. It is preferable that the power to be controlled is controlled.

  When the duty ratio is controlled in this way, the backlight lighting control can be easily performed using, for example, a microcomputer.

  As a typical device equipped with such a flash, there is a camera that photographs a subject in accordance with a photographing operation. When the device of the present invention is a camera, the camera is equipped with the display screen, and charging is performed when the lighting control unit detects that charging is performed while the backlight is lit to illuminate the display screen from the back. The brightness of the backlight is dimmed before, and it is difficult for the brightness of the backlight to change even after charging is started.

 According to the camera of the present invention, it is possible to provide a device including a flash that prevents a change in luminance of a display screen due to a change in luminance of a backlight during charging.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 1 is a diagram showing a configuration of a camera according to an embodiment of the present invention.

  A lens barrel 11 is provided at the center of the camera body 1a, and a finder objective window 13a is provided above the lens barrel 11. Further, a flash emission window 12 is provided beside the finder objective window 13a. A flash is emitted from the light emitting window 12 by a flash provided in the camera 1. Further, a release button 15 is provided on the upper part of the camera body 1a, and photographing is performed by operating the release button 15.

  FIG. 2 is a view showing the back of the camera.

  As shown in FIG. 2, an eyepiece window 13b of the finder 13 and an LCD 14 are provided on the back of the camera. The LCD 14 corresponds to the display screen according to the present invention. A backlight for illuminating the display screen from the back is provided inside the camera, and the LCD and the backlight constitute a display unit.

  FIG. 3 is a control block diagram showing an internal control configuration.

  As shown in FIG. 3, a battery BT is loaded in the camera, and electric power necessary for camera operation is supplied from the battery BT. The power supply from the battery BT is received, and the CPU 100, the battery voltage monitor unit 101, the temperature measuring unit 102, the shutter unit 103, the lens barrel unit 104, the LCD 106, the EERPOM 107, the charge voltage monitor unit 108, the AF unit 109 shown in FIG. Electric power is supplied to each unit such as the flash 110, and each unit is controlled and operated by the CPU 100 in an integrated manner. Since the backlight 130 has to be supplied with a voltage higher than the output voltage of the battery BT in order to illuminate with a stable brightness, power is supplied after the voltage is boosted by the booster circuit 120. The backlight 130 brightens the display screen of the LCD 106.

  In the camera 1, since it is necessary for the CPU 100 to detect the operation signal of the camera 1, a large number of switches are provided. In response to the operation signals from these switches 105, the CPU 100 causes each unit to appropriately perform an operation in accordance with the operation signals.

  Further, when the release button 15 shown in FIG. 1 is operated, the CPU 100 causes the AF unit 109 to perform in-focus detection, and based on the in-focus detection result, the lens barrel 104 is moved back and forth, and the in-focus position is detected. After the photographing lens is arranged, the shutter is driven to open the shutter at a predetermined shutter speed.

  Further, when the object luminance is detected by a photometry circuit (not shown) and the object luminance is equal to or lower than a predetermined value, or when the forced flash emission mode is set, flash light is emitted from the flash 110. . The flash 110 is provided with a main capacitor, and the charging voltage of the main capacitor is monitored by the charging voltage monitor 108. The voltage monitored by the charging voltage monitor 108 is detected by the CPU 100, and the charging current described later is controlled by the CPU 100.

  Here, the relationship between the CPU 100, the flash 110, the booster circuit 120, and the backlight 130 is shown, and their operations will be described.

  FIG. 4 is a diagram illustrating the configuration of the charging voltage monitor 108, the booster circuit 120, the backlight 130, the flash 110, and the battery voltage monitor unit 101.

  As shown in FIG. 4, the voltage from the battery BT is input, and the voltage boosted to 5 V by the booster circuit 120 is supplied to the backlight 130. Here, the backlight 130 is indicated by a diode symbol. The input lower limit voltage of the booster circuit 120 is a voltage that can hold the boost (assuming 2 V). If a voltage that is higher than the voltage that can hold the boost is input, a voltage of 5 V is output and the current is changed. A stable current is supplied to the backlight 130. A resistor R1 is connected in series to the backlight 130, and a constant current flows when 5V is applied to one end of the backlight 130. The other end of the backlight 130 is connected to the CPU 100, and when the connection point reaches the ground level by the CPU, a current flows through the backlight 130 and the backlight 130 is turned on. Further, when the CPU 100 performs control such as opening the connection point so as to disconnect the connection point, the backlight 130 is turned off. In this camera, normally, the connection point is set to the ground level, and the backlight is turned on with DC power. However, when the battery voltage drops and falls below 2V on the input side, the backlight may be turned on, but it may turn off. Therefore, here, in order to reduce the load of the battery when the battery voltage drops, the power supply to the backlight is turned on so that the backlight brightness is lowered and the power supply from the DC power is supplied to the power supply by the pulse train power. It has been switched to. As a result, the power supplied to the backlight is reduced, and the luminance is reduced. By doing so, the load on the battery is reduced.

  Further, the configuration of the flash 110 is shown in the lower part of FIG.

  The flash 110 includes a main capacitor MC, a charging circuit that boosts the voltage from the battery BT and charges the main capacitor MC, 1100, and a light emitting unit that emits flash light by receiving the power stored in the main capacitor MC. Have. The light emitting unit includes a light emitting circuit, a xenon tube Xe, and an IGBT, and emits flash light in response to a flash light emission instruction from the CPU 100.

  As shown in FIG. 4, when the flash emission instruction is given from the CPU 100 to the light emitting circuit 1101, the IGBT is turned on, the charge accumulated in the main capacitor is discharged to the xenon tube Xe, and the flash light is emitted from the xenon tube Xe. The light emitting circuit 1101 also supplies a trigger signal to the trigger electrode of the xenon tube Xe. The trigger signal excites the xenon tube Xe and further turns on the IGBT to turn the main capacitor MC, xenon tube Xe, and IGBT on the main path. The electric charge stored in the capacitor MC is discharged. When the flash emission instruction is given in this way and the electric charge is discharged from the main capacitor MC to the xenon tube Xe, the charging voltage of the main capacitor MC decreases. Therefore, when the charging voltage of the main capacitor MC is monitored by the charging voltage monitor and the charging voltage of the main capacitor MC is lowered, the charging instruction is given from the CPU 100 to the charging circuit 1100, and the main capacitor MC is charged. .

  FIG. 5 is a diagram illustrating an internal configuration of the charging circuit 1100.

  As shown in FIG. 5, electric power is supplied from the battery BT to the chopper circuit 1100a, and the electric power is intermittently transmitted to the transformer T1 side by the switching signal. When electric power is intermittently supplied in this way, a magnetic flux is generated in the transformer T1 by the current flowing through the primary winding W1 of the transformer T1. Due to this magnetic flux, a current also flows through the secondary winding W2, and this current is supplied to the main capacitor MC as a charging current.

  At this time, the voltage generated in the main capacitor MC is monitored by the charging voltage monitoring unit 108 formed of a resistance dividing circuit, and the charging voltage is detected by the CPU 100. In the camera of this embodiment, the power supply by the pulse train power is also supplied to the charging circuit. Thus, by adjusting the duty ratio of the pulse train by the CPU 100, not only the backlight is turned on but also the control of the charging current. Has also been carried out.

  Flashing is performed by the flash as described above, and charging is performed by the charging circuit when the main capacitor is discharged. However, after the flashing is performed, the main capacitor is discharged, so the charging voltage is considerably reduced. To do. As described above, when the main capacitor charging voltage is considerably reduced, if the main capacitor is charged, the battery voltage drop becomes large, and the voltage input to the booster circuit of FIG. May fall below (2V). Then, 5V is not output from the booster circuit, and a sufficient current is not supplied to the backlight, and the display screen configured by the LCD becomes dark or disappears.

  Therefore, the CPU 100 supplies the pulse train power to the backlight 130 as shown in FIG. 4 while monitoring the battery voltage and the charging voltage of the main capacitor so that the backlight is lit darker than when the backlight is lit with DC power. In this case, charging is performed after reducing the load on the battery. This CPU corresponds to the lighting control section referred to in the present invention.

  FIG. 6 is a flowchart showing a processing procedure of backlight lighting control performed by CPU 100 of FIG.

  In step S601, it is determined whether or not the main capacitor is charged. If the main capacitor is scheduled to be charged, the process proceeds to the next step S602 to detect the battery voltage. Here, when the charging voltage of the main capacitor MC decreases and it is determined that charging of the main capacitor is scheduled, the process proceeds to the Y side, and the battery voltage is detected in the next step S602. The duty ratio of the backlight is determined according to the detected battery voltage, and the backlight is turned on with the pulse train power of the duty ratio in the next step S604. In this way, when the main capacitor is scheduled to be charged when the backlight is turned on, power is supplied to the backlight according to the voltage of the battery, and the backlight is lit darker than when the backlight is turned on with DC power. By doing so, it is possible to prevent a change in luminance of the backlight during charging. If it is determined in S602 that there is no plan to charge the main capacitor, there is no possibility that the luminance of the backlight will change, so that the process proceeds to step S605 and the backlight is turned on by DC power.

  In the example of FIG. 6, pulse train power corresponding to the battery voltage is supplied to the backlight. However, if the charging voltage of the main capacitor is reduced, a large charging current flows and the voltage drop of the battery increases. Even if the lighting control 5 is performed, the voltage drop of the battery becomes large, and the luminance of the backlight may change.

  Therefore, if the duty ratio is controlled according to the charging voltage of the main capacitor by using the monitoring of the charging voltage of the main capacitor in addition to the battery voltage, the change in the brightness of the backlight is further suppressed. Is done.

  FIG. 7 is a flowchart showing a processing procedure in the case of performing control for changing the duty ratio depending on the charging voltage of the main capacitor MC in addition to the voltage of the battery BT.

  Processing will be described with reference to the flowchart of FIG.

  As in step S601 in FIG. 6, it is determined in step S701 whether the main capacitor is charged. If the main capacitor is scheduled to be charged, the process proceeds to the next step S702 to detect the battery voltage. Here, when the charging voltage of the main capacitor MC decreases and it is determined that charging of the main capacitor is scheduled, the process proceeds to the Y side, and the battery voltage is detected in step S702. In the next step S703, it is determined whether or not the detected battery voltage is equal to or lower than a set level. If the battery voltage detected in step S703 is less than or equal to the set level, the process proceeds to the Y side, and if greater than the set level, the process proceeds to the N side.

  If it is below the set level in step S703, the process proceeds to the Y side. In the next step S704, the first duty ratio of the pulse train power to be supplied to the backlight is determined, and the process proceeds to the next step S705, where the charging voltage is set to the set level. Detects if: If the charging voltage is equal to or lower than the set level, the process proceeds to the Y side, and a second duty ratio that is smaller than the first duty ratio is determined in the next step S506. The process proceeds to the next step S707, and the backlight 130 is turned on by the pulse train power having the second duty ratio.

  Further, if it is equal to or higher than the set level in step S705, the process proceeds to the N side. In step S707, the backlight is turned on by pulse train power having the first duty ratio.

  As described above, when the main capacitor MC is scheduled to be turned on when the backlight is turned on, the backlight 130 is supplied with electric power according to the voltage of the battery BT and the charging voltage of the main capacitor MC. The light is turned on darkly to prevent a change in the brightness of the backlight 130 when charging is performed. In addition, when it progresses to N side by step S701 and step S703, since there is no possibility that a brightness | luminance will change, the backlight is lighted by DC electric power.

  If it does in this way, according to a battery voltage and the presence or absence of charge, supply of suitable electric power to a backlight can be performed.

  In the present embodiment, since the temperature measuring unit is provided, the temperature inside the camera can be monitored. If the lighting control of the backlight is performed according to the monitored temperature, a further excellent effect can be obtained.

  In the present embodiment, the camera is described as an example, but the present invention can be applied to any device provided with a battery and a flash.

It is a figure which shows the structure of the camera which is embodiment of this invention. It is a figure which shows the back surface of a camera. It is a control block diagram which shows the control structure inside a camera. FIG. 3 is a diagram showing the configuration of a charge voltage monitor 108, a booster circuit 120, a backlight 130, a flash 110, and a battery voltage monitor unit 101. FIG. 5 is a diagram illustrating an internal configuration of the charging circuit 1100. It is a flowchart which shows the process sequence of the lighting control which CPU100 of FIG. 5 performs. It is a flowchart which shows another embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Camera 1a Camera body 11 Lens barrel 11a Shooting lens 12 Flash emission window 13 Finder 13a Finder objective window 13b Finder eyepiece window 14 LCD
15 Release button 100 CPU
DESCRIPTION OF SYMBOLS 101 Battery voltage monitor part 102 Temperature measuring part 103 Shutter drive part 104 Lens barrel drive part 105 Switches 106 LCD
107 EEPROM
108 charging voltage monitor unit 109 AF unit 110 flash 1100 charging circuit 1100a chopper circuit 1101 light emitting circuit 120 boosting circuit 130 backlight BT battery MC main capacitor IGBT transistor

Claims (4)

In a device equipped with a flash that is equipped with a battery and operates by receiving power from the battery,
A flash having a main capacitor, a charging circuit that boosts the voltage from the battery to charge the main capacitor, and a light-emitting unit that emits a flash upon receiving the supply of electric power stored in the main capacitor;
A display unit having a display screen and a backlight for illuminating the display screen from the back, and performing display on the display screen;
A battery voltage monitor for monitoring the voltage of the battery; and when the backlight is turned on, when the main capacitor is scheduled to be charged, the backlight is supplied with power corresponding to the voltage of the battery. A device equipped with a flash, characterized by comprising a lighting control unit for lighting the backlight. A charging voltage monitor unit for monitoring the voltage of the main capacitor;
The lighting control unit supplies power to the backlight in accordance with the voltage of the battery and the voltage of the main capacitor when the main capacitor is scheduled to be charged when the backlight is turned on. The apparatus having a flash according to claim 1, wherein the backlight is turned on.   The backlight is lit by receiving power supplied from a pulse train, and the lighting control unit controls power supplied to the backlight by controlling a duty ratio of pulse train power supplied to the backlight. 3. A device equipped with a flash according to claim 1, wherein the device is controlled. 3. The device having a flash according to claim 1, wherein the device is a camera that photographs a subject in accordance with a photographing operation.

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