JPH11235032A - Apparatus for feeding power to monitor and flash provided in camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the configuration of a power supply for both the monitor and flash of a camera and make it very advantageous to reductior of the size and production cost of the camera, by configuring through only one booster means both the inverter power supply circuit for lighting the backlight of the monitor and the converter power supply circuit for charging the flash. SOLUTION: In an apparatus for feeding a power to a monitor and flash provided in a camera, there are provided an inverter circuit for boosting a low DC voltage by the oscillating operation of a booster transformer 10, a lighting circuit for lighting a backlight 17 by the output voltage of the inverter circuit, a charging circuit for charging a main capacitor 19 of the flash by rectifying the output voltage of the inverter circuit via a diode 18, and an IGBT element 20 brought into its non-continuity by the voltage of the main capacitor 19 exceeding a predetermined charging voltage which interrupts thereby the charging circuit. The apparatus feeds power to the charging circuit by the continuity of the IGBT element 20 and to the lighting circuit by the non- continuity of the IGBT element 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for a camera in which power supply to a monitor backlight and charging of a flash device are performed by a single power supply circuit.

[0002]

2. Description of the Related Art Cameras that electrically convert a subject image and store it as still image information in a storage medium such as a semiconductor memory or a magnetic disk and shoot the image are widely known as so-called electronic still cameras and digital video cameras.

[0003] Some cameras of this type include a monitor display device for displaying a subject image on a screen, in addition to a camera having an electronic viewfinder for observing a subject to be photographed.

The monitor / display device (hereinafter simply referred to as a monitor) includes, for example, a liquid crystal display device for supplying a subject image signal, and a backlight (cold cathode discharge tube) provided on the back side of the liquid crystal display device. And an object image is projected on the screen of the liquid crystal display device by the illumination of the backlight.

[0005] In addition to displaying a subject image to be photographed, such a monitor can read subject image information once stored in a storage medium and display the subject image.

[0006] The above-mentioned camera includes a camera provided with a flash device for illuminating and photographing a subject when the field of view is dark and the brightness of the subject is insufficient.

This flash device (hereinafter simply referred to as flash) triggers according to a shutter release.
The xenon discharge tube is configured to emit light upon receiving the charge of the main capacitor.

[0008]

The above-mentioned camera is provided with a power supply circuit for turning on the backlight of the monitor and a power supply circuit for charging the main capacitor of the flash in advance. Specifically, an inverter for boosting a DC low voltage and outputting an AC voltage as a backlight power supply circuit.
A DC-DC converter is provided as a power supply circuit of the flash device for boosting and outputting a low DC voltage.

As a result, the number of components for such a power supply circuit and the work of assembling the components are increased, which is not desirable for lowering the cost of camera production. Therefore, there is a problem that it is difficult to miniaturize the camera.

Therefore, in the present invention, in consideration of the fact that the above-mentioned conventional camera has an inverter as a power supply circuit for a monitor backlight and a converter as a power supply circuit for a flash, these cameras can be shared. It is an object of the present invention to solve the above problems as much as possible as one power supply circuit.

[0011]

In order to achieve the above object, the present invention comprises a monitor means for projecting an image of a subject to be photographed by using illumination of a backlight, and a flash means for illuminating the subject. A voltage booster for boosting a DC low voltage by an oscillating operation to output an alternating voltage; a first power supply for supplying an output voltage of the voltage booster as a backlight lighting voltage; A second power supply unit that includes a rectification unit that rectifies an output voltage of the boosting unit and supplies the output voltage as a charging voltage of the flash unit; and a power supply that causes the first and second power supply units to alternately supply power. The present invention proposes a monitor and flash power supply device provided in a camera, which is constituted by control means.

[0012]

In the power supply device configured as described above, when the power supply control means causes the first power supply means to perform a power supply operation, the backlight is turned on and the subject image is displayed on the monitor means. At this time, charging of the flash unit is stopped.

When the power supply control means causes the second power supply means to perform a power supply operation, the flash means is charged.
In this case, the backlight is turned off.

The above-mentioned power supply control means is provided with switching means in the second power supply means for charging the flash means,
The switching means can be controlled to be in a charging mode of the flash means, and the switching means can be controlled to be non-conductive to be in a lighting mode of the backlight. That is, since the output voltage of the voltage booster drops due to the charging of the flash unit, the backlight is turned off, and the output voltage rises due to the stoppage of charging of the flash unit, so that the backlight is turned on.

Further, the first and second switching means provided in the second power supply means are turned on by a detection signal output when the flash means is sufficiently charged, for example, a ready signal. Switching of the power supply means can be automated.

That is, the switching means is turned on until the ready signal is output, and the flash means is charged by the second power supply means. When the ready signal is output and the switching means is turned off, the charging of the flash means by the second power supply means stops, and the output voltage of the voltage boosting means rises. As a result, the backlight supplied by the first power supply unit is turned on.

When the flash photography is performed and the flash unit is charged again, the output voltage of the voltage boosting unit drops, the backlight is automatically turned off, and the charging mode is stopped.
And

Further, the power supply device can change the brightness of the backlight by operating the operation section of the light control means. That is, the output voltage level of the voltage booster changes according to the setting of the operation unit of the dimmer, and the backlight is dimmed.

The dimming means is configured to shift to an operating state as the power supply control means causes the first power supply means to perform a power supply operation. Further, the dimming means includes a step-up transformer for intermittently oscillating the input current as a voltage step-up means, and an input current control means for intermittently controlling the input current at predetermined time intervals according to the setting of the operation unit. Can be configured by

Further, the flash means is provided with a light control means for automatically controlling the flash light emission, so that the flash light emission amount can be determined according to the distance to the subject, the reflection state, and the like.

[0021]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a first embodiment of the power supply device. This drawing shows a monitor and a flash power supply circuit provided in a camera having a configuration in which photographed subject image information is stored in a storage medium such as a semiconductor memory or a magnetic disk.

In FIG. 1, reference numeral 10 denotes a step-up transformer, which is a flyback transformer having an input coil 10P, an output coil 10S, and a feedback coil 10F. This step-up transformer 10 includes an oscillation transistor 11, a starting resistor 12, a resistor 13 and a capacitor 14,
An inverter is formed together with the 15 time constant circuits, and the DC voltage of the battery power supply 16 is boosted to output a high voltage.

The output coil 10S of the step-up transformer 10 is provided with a power supply circuit (first power supply means) to which a backlight 17 of a liquid crystal display device is connected, and the output voltage of the output coil 10S (inverter output) is used to control the backlight 17. Is turned on. The backlight 17 is a cold cathode fluorescent discharge tube.

The output coil 10 of the step-up transformer 10
S is provided with a power supply circuit (second power supply means) composed of a series connection of a rectifying diode 18, a flash main capacitor 19, and an IGBT element 20. The main capacitor 19 forms a known flash circuit together with the xenon discharge tube 21 and the trigger circuit 22. IG
Capacitor 23 and resistor 24 connected in parallel with BT element 20
Are operated as a noise killer.

That is, the output voltage of the step-up transformer 10 is rectified by the rectifying diode 18 to operate as a converter circuit for charging the flash.
The trigger circuit 22 includes a trigger capacitor 25, a trigger transformer 26, a charging resistor 27, and a trigger switch 28.
It is composed of

IG connected in series to the main capacitor 19
The BT element 20 forms a mode switching means for switching between charging and non-charging of the flash. The IGBT element 20 becomes a flash charging mode when the IGBT element 20 conducts, and the non-conducting IGBT element 20 becomes a backlight lighting mode. Switch. IGBT which is a silicon N channel field effect transistor
Since the element 20 is a high-impedance semiconductor switching element, it can be replaced with another switching element that operates similarly.

The gate of the IGBT element 20 is connected to the electric circuit on the positive electrode side of the battery power supply 16 so that the power supply voltage is supplied to the gate when the power switch 29 is closed so as to conduct the gate. . Further, the gate of the IGBT element 20
A bias resistor 30 and a switching transistor 31 are connected between the emitters.

The transistor 31 is connected to the main capacitor 1
When the battery 9 is charged to a predetermined charging voltage (the charging voltage when the flash is ready to emit light), the conduction current of the neon lamp 32 that is turned on is input as a base and turned on. That is, when the main capacitor 19 reaches a predetermined charging voltage, the neon lamp 32 conducts and the main capacitor 1
9, the lighting current of the neon lamp flows through the neon lamp 32, the base to the emitter of the transistor 31, and the diode 33, and the transistor 31 is turned on. The resistor 34 connected between the base and the emitter of the transistor 31 is a bias resistor.

The transistor 31 is turned on by its ON operation.
The gate-emitter voltage of the IGBT element 20 is extinguished, the IGBT element 20 is switched from conduction to non-conduction, and charging of the flash circuit is stopped.

In this embodiment, the step-up transformer 1
0, a series circuit of a diode 35 and a capacitor 36 connected in parallel to the feedback coil 10F, and a Zener diode connecting a connection portion a of the series circuit and the base of the oscillating transistor 11. There is provided a constant voltage circuit for an output voltage composed of a discharge resistor 38 connected in parallel with a capacitor 36.

In this constant voltage circuit, since the capacitor 36 is charged to the illustrated polarity by the flyback voltage generated in the feedback coil 10F,
When the charging voltage of the battery becomes large, the Zener diode 37 becomes conductive and the oscillation transistor 11 is turned off.

That is, if the output voltage of the step-up transformer 10 increases, the flyback voltage generated in the feedback coil 10F also increases, and the capacitor 36 is charged according to the flyback voltage. From now on, Tsuena
Since the diode 37 conducts according to the charged voltage of the capacitor 36, the ON time of the oscillation transistor 11 is controlled to be shortened, and the output voltage of the step-up transformer 10 is suppressed from increasing.

Therefore, the output voltage value of the step-up transformer 10 can be determined by the constant voltage value of the Zener diode 37. In this embodiment, a zener diode 37 capable of making the output voltage of the step-up transformer 10 generated in the lighting mode of the backlight 17 constant voltage.
Is used.

The constant voltage circuit described above is a battery power source 1
6, the power supply voltage of the backlight 17 can be made constant. In addition, a capacitor 39 shown in FIG. 1 is a capacitor for stabilizing a low DC voltage, 40 is a pilot lamp, and 41 is a ballast capacitor for limiting current. The switch 42 connected between the base and the emitter of the oscillating transistor 11 is temporarily closed in synchronization with the trigger switch 28, and the inverter oscillates temporarily when the flash is started. It is to stop. The trigger switch 28 and the switch 42 are turned ON and OFF by a control signal sent from the camera.
F can be replaced by a solid state switch,
The neon lamp 32 can be replaced by a zener diode which is a constant voltage element.

Next, the operation of the above-described power supply device will be described. When the power switch 29 is turned on, the starting resistor 12
The power supply current passing through the oscillation transistor 1 serves as a starting current.
1 and the transistor 11 is turned on.
As a result, the power supply current flows into the input coil 10P of the step-up transformer 10.

When the power switch 29 is turned on,
A power supply voltage is applied to the gate of the IGBT element 20, and this I
The GBT element 20 enters a conduction transition state. At this time, since the neon lamp 32 is off, the transistor 31 is off.

At this time, the output voltage generated in the output coil 10S of the step-up transformer 10 is a square wave voltage, and the output voltage is several tens volts to several hundred volts. Volts), the backlight 17 does not light up.

The output current flowing due to the output voltage is opposite to the rectifying diode 18 and is blocked by the rectifying action and does not flow to the flash circuit. Therefore, magnetic energy is stored by the input coil current flowing through the step-up transformer 10.

The oscillation transistor 11 goes from ON to OFF due to magnetic saturation of the core of the step-up transformer 10 and saturation of the transistor. At this time, a voltage is generated in each coil of the step-up transformer 10 in the direction indicated by the arrow.

That is, the oscillating transistor 11 which receives the feedback voltage generated in the feedback coil 10F at its base is reliably turned off. The output coil 10
A high voltage (several thousands of volts) flyback voltage is generated at S, and the rectifying diode 1 is generated by the flyback voltage.
8, a forward output current flows.

Therefore, since the IGBT element 20 becomes conductive, the output coil 10S, the rectifying diode 18, the main capacitor 19, the IGBT element 20, the output coil 10
The charging current flows in the loop of S, and the main capacitor 19 is charged. The output voltage of the output coil 10S drops due to the charging current flowing as described above, and as a result, does not reach the lighting voltage of the backlight 17, and the backlight 17 remains off.

Since the flyback voltage disappears due to the decrease in the magnetic energy of the step-up transformer 10, and the feedback voltage of the feedback coil 10F also disappears, a starting current flows through the base of the oscillating transistor 11. The transistor 11 turns on again.

Therefore, the step-up transformer 10 stores magnetic energy by the input coil current, and outputs a flyback voltage by turning off the oscillation transistor 11 to charge the main capacitor 19.

When the step-up transformer 10 oscillates as described above, the main capacitor 19 is charged by the operation of the converter circuit. When the charged voltage reaches a predetermined value, the neon lamp 32 is turned on as described above. I do.
As a result, the transistor 31 that inputs the lighting current of the neon lamp 32 as a base is turned on, and the IGBT element 20 switches off so that the charging of the main capacitor 19 is stopped.

When the charging operation of the flash circuit stops,
The output voltage of the step-up transformer 10 rises rapidly, and the backlight 17 is turned on by this output voltage. By turning on the backlight 17, the subject image is displayed on the monitor. The backlight 17 is turned on when the charging of the flash circuit is stopped. In this case, the inverter circuit operates. In addition, the backlight 17 thus illuminated.
Unless the oscillation operation of the step-up transformer 10 is stopped, the operation continues until the flash circuit is charged again.

When performing flash photography, the subject image displayed on the monitor is confirmed by turning on the backlight 17, and if the shutter is released in that state, the excitation voltage is applied by closing the trigger switch 28. The xenon discharge tube 21 emits light. As a result, shooting can be performed with flash emission.

In addition, since the charge of the main capacitor 19 is discharged by flash photography in this manner, the neon lamp 32 is turned off and the transistor 31 is turned off.
It turns off from N. For this reason, the IGBT element 20 becomes conductive again, and shifts to the charging operation of the flash circuit.

As described above, the backlight 17 is turned off until the charging of the flash circuit is stopped.
The backlight 17 is turned on, and the subject image is displayed on the monitor. The backlight 17 continues to be lit until the flash photography is performed. When the flash photography is performed, the backlight 17 is turned off and the flash circuit is charged.

FIG. 2 is a circuit diagram of a power supply device shown as a second embodiment. The power supply device according to the second embodiment has a circuit configuration including a dimming circuit for the backlight 17 and an automatic dimming circuit for flash emission with respect to the power supply device according to the first embodiment. Therefore, the same components as those of the circuit section and the circuit members shown in FIG.

As shown in the figure, the power supply circuit inputs a power supply voltage signal SO when the power supply switch 29 is closed.
A control operation circuit 50 for outputting a gate control signal S1 of the IGBT element 20 is provided. The control arithmetic circuit 50 controls the trigger signal of the trigger switch 51 which closes in synchronization with the shutter operation, the light receiving signal of the light receiving device 52 which receives the subject reflected light by the flash light emission, and the dimming operation of the backlight 17. A dimming operation signal of the unit (variable resistor) 53 and a charge stop signal by operating the operation switch 54 are input, and control signals S2 to S6 are output.

First, the trigger switch 51 triggers
When a signal is input, a light emission start signal (High level signal) S2 is output to turn on the IGBT element 55, and an oscillation stop signal S3 is output to temporarily stop the oscillation operation of the step-up transformer 10. In this embodiment, the switch 42 of FIG. 1 is a semiconductor switch element,
The switch element is turned on by the oscillation stop signal S3 to temporarily stop the oscillation.

The light receiving signal of the light receiver 52 outputs a light emission stop signal (Low level signal) S4 when the integrated value of the light receiving signal reaches a predetermined value. The light emission stop signal S4 causes the light emission start signal S2 to disappear and the IGBT element 55
Is turned off.

When a dimming operation signal is input from the dimming operation section 53, a dimming signal (pulse signal) S5 is output, and the brightness of the backlight 17 is changed according to the operation of the dimming operation section 53. .

When an operation signal of the operation switch 54 is input, a charge stop signal (High level signal) S6 is output to turn on the transistor 31. That is, by operating the operation switch 54 at any time when the main capacitor 19 is in the charging process, the transistor 31 is turned off.
N, the IGBT element 20 is turned off, the charging of the main capacitor 19 is stopped, and the mode shifts to the lighting mode of the backlight 17.

The control operation circuit 50 is provided by
When the diode 56 conducts and the transistor 31 is turned on by the conduction signal, the ON signal (Low level signal) S7 is inputted to switch from the flash charging mode to the backlight 17 lighting mode. In this lighting mode, a dimming signal S5 is output.

On the other hand, the block 57 shown in the figure comprises the oscillation transistor 11 and the time constant circuit (13, 1) shown in FIG.
4, 15), and an oscillation starter circuit including a constant voltage circuit (35, 36, 37).

In this power supply device circuit, the diode 58 and the IGBT element 55 are connected to the discharge current path of the xenon discharge tube 21, the IGBT element 55 is made conductive, the trigger circuit 22 is operated, and the IGBT is operated. The element 55 is made non-conductive so that the xenon discharge tube 21 stops emitting light.

In the power supply device of this embodiment, when the power switch 29 is closed, the Zener diode 56 is non-conductive and the charge stop signal S6 is at the low level, so that the transistor 31 is turned off. Yes, the control arithmetic circuit 50 shifts to the flash charging mode.

Therefore, the control operation circuit 50 outputs the gate control signal S1 in accordance with the closing of the power switch 29, and makes the IGBT element 20 conductive. Also,
When the power switch 29 is closed, the boosting transformer 10 oscillates, and the flyback voltage output charges the main capacitor 19.

When the main capacitor 19 is charged to a predetermined charging voltage, the Zener diode 56 conducts, and the conduction current turns on the transistor 31. When the transistor 31 is turned on, the IGBT element 20 is turned off, and the charging of the main capacitor 19 is stopped. When the charging of the main capacitor 19 is stopped, the output voltage of the step-up transformer 10 increases, and the backlight 17 is turned on.

Although the above operation is the same as that of the first embodiment, when the transistor 31 is turned on,
The ON signal S7 is input to the control operation circuit 59, and the control operation circuit 50 shifts to the lighting mode of the backlight 17, and outputs the dimming signal S5.

The dimming signal S5 is a pulse signal, and controls the base current of the oscillation transistor so as to intermittently control ON and OFF of the transistor. Therefore,
The pulse duty ratio of the light control signal S5 is adjusted by the light control operation unit 5
If it is changed by the operation setting of 3, the output voltage level of the step-up transformer 10 changes according to the operation setting, and the backlight 17 can be dimmed.

On the other hand, in the case of flash photography, the trigger switch 51 is closed by shutter release, and the control arithmetic circuit 50 outputs a light emission start signal S2. As a result, the IGBT element 55 conducts, the charging voltage of the main capacitor 19 and the charging voltage of the capacitor 23 are added and applied to the xenon discharge tube 21, and the charge of the trigger capacitor 25 is transferred to the IGBT element 55 and the trigger. Discharge through the transformer 26 and trigger circuit 22
, The xenon discharge tube 21 is triggered, so that the xenon discharge tube 21 starts discharging.

The light emission of the xenon discharge tube 21 is based on the fact that the charge stored in the main capacitor 19 is reduced by the xenon discharge tube 21.
This is performed by discharging through the path of the diode 58, the IGBT element 55, and the diode 33. In addition, the light reflected from the subject is reflected by the light receiver 52 by the light emission of the xenon discharge tube 21.
And a light receiving signal is input to the control arithmetic circuit 50.

Thus, when the integration of the light receiving signal reaches a predetermined value, the control arithmetic circuit 50 outputs a low level light emission stop signal S4. The light emission stop signal S4 causes the IGBT
The element 55 becomes non-conductive, interrupts the discharge current of the xenon discharge tube 21, and stops emitting light.

By the above flash emission, the charging voltage of the main capacitor 19 drops, and the Zener diode 5
6 is turned off, so that the transistor 31 is turned off.
Will return to. As a result, the control arithmetic circuit 50 switches to the flash charging mode, outputs the gate control signal S1, and turns on the IGBT element 20 again. Therefore, the main capacitor 19 is charged in the same manner as described above.

On the other hand, when the operation switch 54 is closed while the main capacitor 19 is being charged, the control arithmetic circuit 50 outputs a charge stop signal S6. From this, transistor 3
1 is turned on, the IGBT element 20 is turned off, and
The control operation circuit 50 shifts to the lighting mode of the backlight 17. As a result, even if the flash is charging, if the operation switch 54 is closed, the backlight 17 is immediately turned on.
Lights up, and the subject image on the monitor can be viewed.

[0068]

As described above, in the power supply apparatus of the present invention, the inverter power supply circuit for turning on the backlight of the monitor and the converter power supply circuit for charging the flash are constituted by one voltage booster. The structure of the power supply section of the monitor and flash is simplified, and the camera can be downsized and the production load can be reduced.
This is extremely advantageous for cost reduction.

Also, since the backlight dimming means is provided, the brightness of the monitor can be arbitrarily adjusted. Further, since the flash light dimming means is provided, an appropriate exposure can be obtained in flash photography. be able to.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a power supply device shown as a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a power supply device shown as a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Step-up transformer 11 Oscillation transistor 16 Battery power supply 17 Backlight 18 Rectifier diode 19 Main capacitor 20 IGBT element 21 Xenon discharge tube 22 Trigger circuit 31 Transistor 32 Neon lamp 50 Control operation circuit 51 Trigger switch 52 Light receiver 53 Light control operation unit 55 IGBT element

Claims (4)

[Claims] 1. A camera comprising a monitor means for projecting an image of an object to be photographed by utilizing illumination of a backlight, and a flash means for illuminating the object, the DC low voltage being boosted by an oscillating operation to increase the alternating voltage. A voltage boosting means for outputting, a first power supply means for supplying an output voltage of the voltage boosting means as a lighting voltage of the backlight, and a rectifying means for rectifying an output voltage of the voltage boosting means; A second power supply means for supplying power as a charging voltage of the flash means, and a power supply control means for causing the first and second power supply means to perform a power supply operation alternately. Flash power supply. 2. The device according to claim 1, further comprising a light dimming unit that changes an output voltage level of the voltage boosting unit in accordance with a setting of an operation setting unit and adjusts brightness of a backlight. Power supply for the monitor and flash mounted on the selected camera. 3. The light control device according to claim 1, further comprising a light control unit that receives the subject reflected light by the flash emission and stops the flash emission when the amount of the received light reaches a predetermined value. Monitor and flash power supply for camera. 4. The power supply control means controls power supply and non-power supply of the second power supply means, and the backlight is not lit by the output voltage of the voltage boosting means decreasing by the charging operation of the flash means. The monitor and flash power supply device provided in a camera according to claim 1, wherein the backlight is turned on when the output voltage is increased by a non-charging operation of the flash unit.