JPH10333225A - Feeding device for monitor and flashing device of camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the constitution of the power source parts of a monitor and a flashing device, to make a camera compact and to reduce the producing cost by constituting the inverter power source circuit turning on the back light of the monitor and the converter power source circuit charging the flashing device of one voltage boosting means. SOLUTION: This device is provided with one voltage boosting circuit boosted by the oscillating action of a boosting transformer 10, the turning-on circuit turning on the back light 16 by a voltage outputted from the transformer 10, the charging circuit charging a main capacitor 18 by the voltage outputted from the transformer 10 and an SCR 24 alternately switching the turning-on circuit and the charging circuit. Besides, it is provided with a light control circuit 31 actuated according as a mode is switched to the turning-on mode of the back light from the charging mode of the flashing device. Then, the brightness of the back light 16 can be adjusted according to a light control pulse signal outputted from the control circuit 31 on a condition that an objective image is projected on the monitor.

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 (fluorescent 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 is provided as a power supply circuit of the backlight, and a converter is provided as a power supply circuit of the flash device.

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 a subject image to be photographed by using illumination of a backlight, and a flash means for illuminating the subject. In a camera that stores the subject image in a storage medium, a DC boost voltage is boosted by an oscillating operation to output an alternating voltage, and an output voltage of the voltage booster is used as a lighting voltage of the backlight. Circuit means for supplying the output voltage as the charging voltage of the flash means, and mode switching means for switching the circuit means to alternately switch between a lighting mode of the backlight and a charging mode of the flash means. The operation mode is shifted to the operation mode in the backlight lighting mode, and the output voltage level of the above-described voltage boosting means is changed according to the setting of the operation unit to perform the backlight. Suggest camera monitor and flash of the feed device, characterized in that more structure and light dimming means of a brightness dimming lights.

[0012]

In the power supply apparatus constructed as described above, when the mode is switched to the power supply circuit means for the backlight by the mode switching means, 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 mode is switched to the power supply circuit of the flash unit by the mode switching unit, the main capacitor of the flash unit is charged. In this case, the backlight is turned off.

The above-mentioned mode switching means is provided with switching means only in the power supply circuit of the flash means, and controls the conduction of the switching means to charge the flash means.
And a non-conductivity control of the mode, thereby providing a backlight lighting mode.

If a flyback transformer is provided as a boosting transformer of the voltage boosting means, the mode switching means can be automated. In other words, when charging the flash means, the load becomes heavy, so that the output voltage of the flyback transformer drops. With this output voltage in the charged state, the backlight does not turn on and the charging mode is set.

Accordingly, by connecting the power supply circuit means of the backlight and the power supply circuit means of the flash means in parallel to the output side of the flyback transformer, the charging of the flash means is completed and the output voltage of the flyback transformer rises. When the backlight is turned on, the backlight is automatically turned on and the lighting mode is set.

When the flash photography is performed and the flash unit is charged again, the output voltage of the flyback transformer drops as described above, and the backlight is automatically turned off to enter the charging mode.

Further, in this power supply device, when the mode is switched to the lighting mode of the backlight, the dimming means is operated, and
The brightness of the backlight can be changed by operating the operation unit 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 shifts to the operating state in accordance with the switching operation of the mode switching means. The dimming means includes a voltage step-up transformer for intermittently oscillating an 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 a setting of an operation unit. Can be configured by

[0020]

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 forms an inverter together with an oscillating transistor 11, a starting resistor 12, a base resistor 13 and a capacitor 14.
And outputs a high voltage.

A power supply circuit to which a backlight 16 of a liquid crystal display device is connected is provided in the output coil 10S of the step-up transformer 10, and the output voltage (inverter) of the entire output coil 10S is provided.
The backlight 16 is turned on by the data output. The backlight 16 is a cold cathode fluorescent discharge tube.

The output coil 10 of the step-up transformer 10
The intermediate tap Q provided at S is provided with a power supply circuit to which a flash main capacitor 18 is connected via a rectifying diode 17. The main capacitor 18 forms a known flash circuit together with the xenon discharge tube 19 and the trigger circuit 20.

That is, the output voltage of the step-up transformer 10 is rectified by the rectifying diode 17 to operate as a converter circuit for charging the flash.
The trigger circuit 20 includes a trigger capacitor 21, a trigger transformer 22, and a charging resistor 23.

The SC connected in series to the main capacitor 18
R24 is a mode for switching between charging and non-charging of the flash.
A mode switching means is formed. When the SCR 24 is turned on, a flash charging mode is set, and when the SCR 24 is turned off, the mode is switched to a backlight lighting mode.

The SCR 24 is a controller 25
The high-level mode switching signal S1 output by the
When the mode switching signal S1 attains a low level, it becomes non-conductive. Note that the controller 25 has a control circuit configuration including a CPU and the like.

The zener connected to the main capacitor 18
The diode 26, the resistors 27 and 28 connected in series to the zener diode 26, and the FET 29 connected to the connection point a of the resistors 27 and 28 form a charge detection circuit for the main capacitor 18. doing. In addition, FET2
Reference numeral 9 denotes an N-channel MOS field effect transistor. That is, while the main capacitor 18 is being charged, the high level charge detection signal S2 is supplied from the controller 25 to the drain of the FET 29.

When the main capacitor 18 is charged to a predetermined voltage, the Zener diode 2
6 conducts, and as a result, the voltage generated at the resistor 28 becomes FE.
In addition to the gate of T29, the FET 29 conducts, and the conduction causes the charge detection signal S2 to change to a low level, which is input to the controller 25 as a charge stop signal.

The controller 25 receives the low-level charge detection signal S2, changes the high-level mode switching signal S1 to a low level, and controls the SCR 24 to turn off. Since a half-wave rectification charging current for charging the main capacitor 18 flows through the SCR 24, the anode-cathode voltage is applied while the low-level mode switching signal S1 is being gated. Becomes non-conductive when the voltage becomes zero.

The SCR 30 gates and inputs the trigger signal S0 output from the controller 25 in accordance with the shutter release, and the SCR 30 is turned on to operate the trigger circuit 20. Note that the trigger circuit 20 is SCR3
The conduction of 0 causes the trigger transformer 22 to operate, and the xenon discharge tube 19 is activated to emit light by the high excitation voltage output from the trigger transformer 22.

Further, the above-described power supply device includes a dimming circuit (dimming IC) 31 that can change the brightness of the backlight 16 by operation setting. The dimming circuit 31 is supplied with power by the charging voltage of the capacitor 33 charged via the diode 32, and enters the operating state by inputting the dimming control signal S3 sent from the controller 25.

The dimming control signal S3 is at the high level during the charging mode in which the flash is charged, but the charging detection signal S2 is low due to the conduction of the FET 29.
By changing to the level, the controller 25 changes the dimming control signal S3 to the low level, and the dimming circuit 31 shifts to the operation state by the low-level dimming control signal S3.

That is, when the charge detection signal S2 goes low, the mode switching signal S1 goes low and the SCR 24 becomes non-conductive, switching from the flash charging mode to the backlight lighting mode. However, when the dimming control signal S3 changes to the low level of the charge detection signal S2,
Since the level becomes the low level, the dimming circuit 31 switches to the lighting mode of the backlight and shifts to the operation state.

The dimming circuit 31 is configured to oscillate in the range of 500 Hz to 10 KHz by setting the capacitor 34 and the variable resistor 35, and according to the operation setting of the variable resistor 36 serving as an operation section. A dimming pulse signal S4 having a duty ratio of 100% is supplied to the transistor 37.
Is output from ON and OFF.

The dimming pulse signal S4 limits the base current of the oscillating transistor 11 according to the duty ratio and intermittently controls the ON and OFF times of the transistor 11, so that the step-up transformer is controlled by this intermittent control. The output voltage level of the backlight 10 changes, and the brightness of the backlight 16 is adjusted.

Next, the operation of the above-described power supply device will be described with reference to a time chart shown in FIG. When the power switch 38 is turned on, the controller 25 outputs the High level signals S1, S2, S3 in response to the turning on of the power switch 38. (FIG. 2 (A), (B),
(See (C) and (E).) From this, the SCR 24 shifts to the conductive state and the charging mode is started.
And Further, the dimming circuit 31 is kept in a non-operating state.

When the power switch 38 is turned on, the power supply current passing through the starting resistor 12 flows as a starting current to the base of the oscillation transistor 11, and the transistor 11 is turned on. Thus, the input coil 1 of the step-up transformer 10
The power supply current flows to 0P.

At this time, the output coil 1 of the step-up transformer 10
Since the output voltage generated at 0S is a square voltage and the output voltage is several tens volts to several hundred volts, the output voltage does not reach the lighting voltage (thousands of volts) for lighting the backlight 16; Does not light. Also, the output current flowing by the output voltage becomes opposite to the diode 17 and is blocked by the rectifying action.
Does not flow to flash. Therefore, the step-up transformer 1
0 stores magnetic energy as the input coil current flows.

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, the step-up transformer 1
Each of the 0 coils generates a voltage 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 a forward output current flows through the diode 17 due to the flyback voltage.

That is, charging current flows through the loop of the output coil portion 10S1, the diode 17, the main capacitor 18, and the SCR 24, and the main capacitor 18 is charged. The entire output voltage of the output coil 10S drops due to the charging current flowing as described above, and as a result, the backlight 16 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.

Accordingly, 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 18. In the charging mode in which the main capacitor 18 is charged as described above,
Since the light control circuit 31 is in the non-operation state, the light control pulse signal S4 is not output. As a result, since the ON / OFF operation of the oscillation transistor 11 is not restricted, a full flyback voltage is generated in the output coil portion 10S1, and flash charging is performed efficiently.

When the step-up transformer 10 oscillates as described above, the main capacitor 18 is charged by the function of the converter circuit. When the charged voltage reaches a predetermined value, the Zener diode 26 becomes conductive. I do.

As a result, the charge detection signal S2 changes to the low level due to the conduction of the FET 29, and this signal S2 is sent to the controller 25. (See FIGS. 2D and 2E.) The controller 25 changes the mode switching signal S1 and the dimming control signal S3 to Low level in response to the charging detection signal S2. (See FIGS. 2B and 2C.) That is, the mode switching signal S1 is changed to the Low level, the SCR 24 is turned off, and the flash charging mode is changed.
Mode is switched to the backlight lighting mode. Further, the controller 25 changes the dimming control signal S3 to a low level to shift the dimming circuit 31 to the operating state.

As a result, the charging of the flash is stopped, so that the output voltage of the output coil portion 10S1 increases,
Output coil portions 10S1, 10S2 of step-up transformer 10
, The output voltage suddenly rises, and the backlight 16 is turned on by this output voltage. By this lighting, the subject image is displayed on the monitor. (Refer to FIG. 2 (F).) The backlight 16 is turned on when the charging of the flash is stopped. In this case, the inverter circuit operates.

The backlight 1 thus lit is
The light 6 can be adjusted by manipulating the variable resistor 36. In the lighting mode of the backlight 16, the variable resistor 36
Is variably operated to control the O of the transistor 37 of the light control circuit 31.
The duty ratio of the dimming pulse signal S4 output from the transistor 37 can be changed by changing N and the OFF time.

The dimming pulse signal S4 is applied to the base of the oscillating transistor 11, and this transistor 11 is turned on and off.
To intermittently control the OFF repetition time, a step-up transformer 1
The output voltage level of 0 changes according to the operation setting of the variable resistor 36, and the brightness of the backlight 16 changes. (See Fig. 2 (G))

More specifically, the oscillation transistor 11 is repeatedly turned on and off at a frequency of 30 KHz, for example.
Control is performed according to a light control pulse signal S4 of 0 Hz to 10 KHz.

Therefore, by adjusting the operation of the variable resistor 36 and dimming the backlight 16, it is possible to adjust the brightness to a level suitable for monitor observation.

When flash photography is performed, the subject image displayed on the monitor is checked by turning on the backlight 16, and when the shutter is released in that state, the SCR3 is output by the release signal S0 output from the controller 25.
0 conducts, and the xenon discharge tube 19 emits light. (Figure 2
(See (H))

By performing flash photography in this way, the charge and discharge of the main capacitor 18 is discharged.
The Zener diode 26 and FET 29 become non-conductive,
The charge detection signal S2 returns to a high level. (Figure 2
(See (D) and (E).) From this, the controller 25 responds to the high-level charge detection signal S2 and responds to the high-level mode switching signal S2.
1 is output, and the SCR 24 is turned on to start the flash charging operation. (See FIGS. 2B and 2E)

As a result, the backlight 16 is turned off until the charging of the flash is stopped, and then, as described above, the backlight 16 is turned on, and the subject image is displayed on the monitor.

As described above, the flash charging mode is set by the high-level mode switching signal S1, and the backlight lighting mode is set by the low-level mode switching signal S1. Is configured to change the mode switching signal S1 to a low level by inputting the switch signal of the operation switch 39, the mode switching signal S1 is operated in accordance with the operation of the operation switch 39 even while the flash is being charged. The backlight 16 is turned on from the High level to the Low level, and the subject image can be displayed on the monitor.

The low level charge detection signal S2
Is a charge stop signal indicating that the flash is ready to emit light, that is, a ready signal. Therefore, means for shifting the camera to the flash photographing mode in response to the charge detection signal S2 is provided. Can be.

FIG. 3 is a circuit diagram of a power supply device shown as the second embodiment. In the second embodiment, the high-level signals S1, S2, and S3 are supplied from the battery power supply 15, and the charge detection signal S2 goes low, thereby causing the mode switching signal S1 and the dimming control signal. S3 changes to the low level and disappears, and the charging mode is switched to the lighting mode. The resistors 41, 4
2 is a current limiting resistance.

In the second embodiment, a series circuit of a diode 43 and a capacitor 44 connected in parallel to a feedback coil 10F of a step-up transformer 10, a connection portion b of the series circuit and an oscillation transistor A zener diode 45 connected to the base 11 and a capacitor 4
4 is provided with a constant voltage circuit of an output voltage composed of a discharge resistor 46 connected in parallel.

In this constant voltage circuit, since the capacitor 44 is charged to the polarity shown in the figure by the flyback voltage generated in the feedback coil 10F,
When the charging voltage of the battery becomes large, the Zener diode 45 conducts 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 44 is charged according to the flyback voltage. From now on, Tsuena
Since the diode 45 conducts according to the charged voltage of the capacitor 44, the ON time of the oscillation transistor 11 is controlled to be shortened, and an increase in the output voltage of the step-up transformer 10 is suppressed.

Therefore, the output voltage value of the step-up transformer 10 can be determined by the constant voltage value of the Zener diode 45. In this embodiment, a zener diode 45 is used which can make the output voltage of the step-up transformer 10 generated in the backlight lighting mode constant.

The above-described constant voltage circuit is connected to the battery power source 1
5, the power supply voltage of the backlight 16 can be made constant. Further, since the other configuration of the second embodiment is the same as that of the first embodiment shown in FIG. 1, the same components are denoted by the same reference numerals.

In this embodiment, when the power switch 38 is turned on, the power supply voltage is applied to each circuit as signals S1, S2, and S3. That is, the high-level mode switching signal S1 is applied to the gate of the SCR 24, and the dimming control signal S3 becomes high and is supplied to the dimming circuit 31.

Therefore, when the step-up transformer 10 oscillates, the output coil portion 10 on one side of the intermediate tap Q
The main capacitor 18 is charged by the flyback voltage generated in S1.

Although the flyback voltage is generated in the output coil portion 10S1 on one side of the intermediate tap Q and the output coil portion 10S2 on the other side, the flash coil is charged as described above. Since the flyback voltage of 10S1 drops, the backlight 1
6 remains unlit. In this charging mode, since the dimming control signal S3 is at a high level,
The dimming circuit 31 is in a non-operating state.

When the charged voltage of the main capacitor 18 reaches a predetermined value, the charge detection signal S2 becomes low level,
As a result, the mode switching signal S1 changes to the low level, the SCR 24 inverts to non-conduction, the dimming control signal S3 changes to the low level, and the dimming circuit 31 enters the operating state.

As a result, the charging of the flash is stopped, and the flyback voltage generated in the output coil portion 10S1 of the step-up transformer 10 increases. Therefore, the backlight 16 is turned on in response to the high flyback voltage generated in the output coil portions 10S1 and 10S2, and the subject image is displayed on the monitor.

The brightness of the backlight 16 can be adjusted by operating and setting the variable resistor 36 in the lighting mode. Also, when flash photography is performed in the display state of the monitor, the operation shifts to the charging mode, and the backlight is switched to the backlight mode. The turning off of the lamp 16 and the like are the same as in the first embodiment.
Further, the constant voltage circuit provided in the second embodiment can be provided in the same manner in the first embodiment shown in FIG.

FIG. 4 is a circuit diagram of a power supply device shown as the third embodiment. In the third embodiment, a step-up transformer 1
F that interrupts the power supply current input to the 0 input coil 10P
ET (field effect transistor) 50 and this FET 50
It is characterized by having a control transistor 51 for performing gate control of the second embodiment, and the other configuration is the same as that of the second embodiment shown in FIG.

FIG. 5 is a circuit diagram of a power supply device shown as the fourth embodiment. The fourth embodiment is characterized in that a mode switching means is configured by using a photocoupler including a photo diode 62 and a photo SCR 60.

That is, a photo SCR 60 is provided in place of the rectifying diode 17 of the flash, and a series circuit of a resistor 61, a photo diode 62, and a transistor 63 for switching operation is connected in parallel to the battery power supply 15. It is a mode switching means connected and configured. In other respects, the configuration is the same as that of the second embodiment shown in FIG. 3, but the SCR 24 is not required in the fourth embodiment because the mode switching means is configured as described above.

In the fourth embodiment, when the power switch 38 is turned on, the power supply voltage is applied to the base of the transistor 63 as the mode switching signal S1.
Turns ON. As a result, the photodiode 62 emits light, the photo SCR 60 receives the light emission, conducts, and enters a flash charging mode. The main operation is performed by the flyback voltage of the output coil portion 10S1 generated by the oscillation operation of the step-up transformer 10. The capacitor 18 is charged.

When the main capacitor 18 is charged to a predetermined voltage, the FET 29 is turned on and the H
The high-level charge detection signal S2 goes low, so the mode switching signal S1 goes low, turning off the transistor 63. As a result, the photodiode 62 is turned off, the photo SCR 60 is turned off, the charging of the flash is stopped, and the backlight is turned on.

That is, since the output voltage of the output coil portion 10S1 of the step-up transformer 10 increases, the backlight 16 is turned on in response to the flyback voltage generated in the output coil portions 10S1 and 10S2, and the subject image is displayed on the monitor. It is. Other operations are the same as those of the second embodiment shown in FIG.

FIG. 6 is a circuit diagram of a power supply device shown as the fifth embodiment. In the fifth embodiment, the step-up transformer 70 is a forward-type transformer including an input coil 70P, an output coil 70S, and a feedback coil 70F.

In this type of step-up transformer 70, the output voltage of the output coil portion 70S1 drops during the flash charging operation, but the degree of the drop is small, so that the flash charging mode and the backlight lighting mode are performed. The winding ratio is changed according to the following.

That is, an intermediate tap P is provided in the input coil 70P of the step-up transformer 70, and a power supply current is input to the coil portion 70P1 at one side of the input from the intermediate tap P, so that the lighting mode, the input coil portions 70P1, 70P2 The turn ratio can be changed so that the power supply current is input to the switch and the charging mode is set.

In this figure, an FET 71 is an oscillation switching element for interrupting a power supply current input to the input coil portions 70P1 and 70P2, and an FET 72 is an oscillation switching device for interrupting a power supply current input to the coil portion 70P1 to one input. Switching element. Note that these F
ETs 71 and 72 are both P-channel MOS field effect transistors.

Transistors 73 and 74 connected to the gates of the FETs 71 and 72 are control switching elements for turning the FETs 71 and 72 on and off.
A starting current flowing through the starting resistors 75 and 76 is input as a base and turned on, and a feedback action is provided by a feedback coil 70F of the step-up transformer 70.

A transistor 77 connected between the base and the emitter of each of the control transistors 73 and 74,
Numeral 78 is for turning ratio switching, which is based on turning ratio switching signals S3 and S4 and is alternately turned on.

That is, the transistor 78 is turned on by the turn ratio switching signals S3 and S4 output from the controller 79.
N: If the transistor 77 is kept OFF, the control transistor 74 remains OFF, and the control transistor 73 repeats ON and OFF.

Therefore, FET 71 repeats conduction and non-conduction, and FET 72 maintains non-conduction. Thus, the step-up transformer 70 oscillates due to the power supply current flowing through the entire input coil 70P, and the turn ratio decreases.

On the contrary, the transistor 77 is turned on.
Then, if the transistor 78 is kept OFF, the FET 71 keeps the non-conductivity and the FET 72 repeats the conduct and the non-conductivity in the same manner as described above. As a result, the step-up transformer 70 oscillates due to the power supply current flowing through the input coil portion 70P1, and the turns ratio increases.

In the fifth embodiment, the winding ratio of the forward type step-up transformer 70 is changed according to the mode switching as described above, but the other structures are the same as those shown in FIG. It has the same configuration as the fourth embodiment.

When the power supply switch 38 is turned on, the power supply apparatus described above has a time chart (A) shown in FIG.
As shown in (B), (C), and (E), the controller 79 outputs the high level switching signals S1 and S4 and the charge detection signal S.
2 is output. At this point, as shown in FIG. 7F, the switching signal S3 is at the low level.

As a result, the transistor 63 is turned on, the photo diode 62 emits light, and the photo SCR 60 conducts, so that the flash charging mode is set. Further, since the transistor 78 is turned on, the FET 72 is kept off, and the FET 71 is repeatedly turned on and off.

Accordingly, the main capacitor 18 is oscillated by the operation of decreasing the winding ratio in which the power supply current flows through the entire input coil 70P of the step-up transformer 70, and charges the main capacitor 18. The backlight 16 does not turn on with the output voltage of the step-up transformer 70 having the reduced winding ratio.

When the main capacitor 18 is charged to a predetermined voltage, the high-level charge detection signal S2 changes to the low level as shown in FIG.
In response to the charge detection signal S2, the switching signal S
1, S4 is changed from High level to Low level, and a High level switching signal S3 is output. (FIG. 7
(See (B), (C) and (F))

As a result, the transistor 63 is turned off, the photodiode 62 is turned off, the photo SCR 60 is turned off, and the backlight is turned on. Further, since the transistor 77 is turned on, the FET 71 keeps off, and the FET 72 repeats on and off.

As a result, a power supply current is input to the step-up transformer 70 from the intermediate tap P, and the turn ratio in which the power supply current flows to the input coil portion 70P1 is increased. The step-up transformer 70 oscillates with the winding ratio increased in this way, and the backlight 16 is turned on by the output voltage. (Refer to FIG. 7 (G).) Other operations of the fifth embodiment are the same as those of the above-described embodiments. However, when dimming the backlight 16, the operation is switched after switching to the lighting mode. A dimming pulse signal is supplied instead of the signal S3. In the fifth embodiment, a mode switching means of the SCR 24 shown in FIGS. 1 and 3 may be provided instead of the photocoupler.

[0090]

As described above, in the power supply device according to 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. This simplifies the configuration of the power supply for the monitor and the flash, which is extremely advantageous for downsizing the camera and reducing the production cost. In addition, the flash is not operated in the charging mode, and the backlight is turned on. Since the backlight dimming means which shifts to the operating state when the monitor is provided is provided, the brightness of the monitor can be arbitrarily adjusted.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a power supply device according to a first embodiment.

FIG. 2 is a time chart for explaining the operation of the first embodiment.

FIG. 3 is a circuit diagram of a power supply device according to a second embodiment.

FIG. 4 is a circuit diagram of a power supply device according to a third embodiment.

FIG. 5 is a circuit diagram of a power supply device according to a fourth embodiment.

FIG. 6 is a circuit diagram of a power supply device according to a fifth embodiment.

FIG. 7 is a time chart for explaining the operation of the fifth embodiment.

DESCRIPTION OF THE SYMBOLS 10 Step-up transformer of flyback type 11 Oscillation transistor 16 Monitor backlight 18 Main capacitor 19 Xenon discharge tube 24 SCR 25 constituting mode switching means 25 Controller 29 Generates charge detection signal S2 FET 31 Dimming circuit 36 Variable resistor as operation unit 43 Diode forming constant voltage circuit 44 Capacitor forming constant voltage circuit 45 Zener diode forming constant voltage circuit 60 Photo SCR forming photocoupler 62 Photodiode Constituting Photocoupler 70 Forward Type Boost Transformer 71, 72 FET for Oscillation 79 Controller

Claims (4)

[Claims] 1. A camera comprising: a monitor for projecting a subject image to be photographed by utilizing illumination of a backlight; and a flash unit for illuminating the subject, wherein the camera stores the photographed subject image in a storage medium. Voltage boosting means for boosting the voltage by an oscillating operation to output an alternating voltage, and circuit means for supplying an output voltage of the voltage boosting means as a lighting voltage of the backlight and supplying the output voltage as a charging voltage of the flash means. Mode switching means for switching the circuit means and alternately switching between a lighting mode of the backlight and a charging mode of the flash means;
The operation mode is switched to the operation mode in the backlight lighting mode, and the output voltage level of the voltage boosting means is changed according to the setting of the operation unit, and the light dimming means dims the brightness of the backlight. Characteristic camera monitor and flash power supply. 2. The voltage boosting means has a flyback transformer that oscillates, and the output voltage of the transformer drops by the charging operation of the flash means so that the backlight is not lit and the output voltage of the flash means does not change. 3. A power supply device for a monitor and a flash of a camera according to claim 1, further comprising mode switching means configured to turn on a backlight when the battery is raised by a charging operation. 3. A switching means is provided in the circuit means for charging the flash means, and the switching means is operated to conduct, and the charging means of the flash means is turned off, and the non-conductive state is set to the lighting mode of the backlight. The power supply apparatus for a monitor and a flash of a camera according to claim 1, further comprising a mode switching means. 4. The voltage boosting means has a step-up transformer for oscillating the input current repeatedly by intermittently oscillating the input current, and the light dimming means sets the intermittent current input to the step-up transformer at predetermined time intervals according to an operation setting. 3. A power supply device for a monitor and a flash of a camera according to claim 1, wherein the intermittent control is carried out by the following.