JPH07193773A - Charge control device for still video camera - Google Patents

Abstract

PURPOSE:To make it possible to use a strobascopic device even in a monitor recording mode. CONSTITUTION:Switches SW1, SW2 are connected to resistors R1, R2 in a charging circuit 60 respectively in parallel. In a normal recording mode, the switches SW1, SW2 are in an ON state. In the ON state, a current supplied from a base driving winding 65b of a transformer 65 is by-passed through the resistors R1, R2 and the base current of a transistor (TR) 66 is relatively increased. Thereby a current supplied from a battery 6 to a primary winding 65a is also increased. Since the switch SW2 is turned off in a monitor recording mode, the current supplied from the winding 65b flows into the resistor R2 and is relatively reduced and a current flowing into the winding 65a is also reduced. When an optical system 12 is driven, the switch SW1 is turned off and the current supplied from the winding 65b is furthermore reduced through the resistors R1, R2 and also the current flowing into the winding 65a is furthermore reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge control device provided in a still video camera for controlling the magnitude of a charge current supplied to a main capacitor of a flash device.

[0002]

2. Description of the Related Art As a conventional still video camera, there is known a still video camera which can be controlled by an operation mode such as a monitor recording mode in addition to a normal recording mode. The monitor recording mode is a mode in which the still image at that time is recorded on the recording medium by pressing the release switch while checking the moving image obtained through the image sensor on the monitor TV, and the moving image is monitored. A large amount of current is constantly being consumed. On the other hand, a large current is consumed when charging the main capacitor of the strobe device.

[0003]

Therefore, in order to reduce the load on the power source, there has been conventionally proposed a still video camera configured to prohibit the use of the strobe device in the monitor recording mode. However, there is a problem that underexposure tends to occur when recording is performed on a dark subject. On the other hand, if the strobe device can be used even in the monitor recording mode, the capacity of the power supply must be increased, which causes a problem that the shape and weight of the power supply are increased.

The present invention solves such a conventional problem, and enables the strobe device to be used even in the monitor recording mode without increasing the shape of the power source or increasing the weight. The purpose is to do.

[0005]

According to the present invention, there is provided a charge control device for a still video camera, which includes an operation control means for controlling the still video camera in a predetermined operation mode, and a means for accumulating charges for causing a strobe device to emit light. And a single power supply for supplying a current to the operation control means and the charge storage means, and a current control means for controlling the magnitude of the current supplied from the power supply to the charge storage means. ,
It is characterized in that when the current consumption by the operation control means is relatively large, the magnitude of the current is relatively small.

[0006]

The present invention will be described below with reference to illustrated embodiments. FIG. 1 is a block circuit diagram of a still video camera provided with a charge control device according to a first embodiment of the present invention.

The system control circuit 10 controls the entire still video camera and includes a microcomputer and the like. An optical system 12 and a diaphragm 13 are provided in front of the light receiving surface of the solid-state image sensor 11, and the diaphragm 13 adjusts the amount of incident light from the subject SB to the solid-state image sensor 11.
The optical system 12 is controlled by a zoom drive circuit 14 and a focus drive circuit 15, whereby the zooming operation and the automatic focus adjusting operation of the optical system 12 are performed. The size of the aperture of the diaphragm 13 is adjusted by the diaphragm drive circuit 16. Zoom drive circuit 14, focus drive circuit 15
The diaphragm drive circuit 16 is controlled by the system control circuit 10.

The image pickup device 11 is driven by a shift pulse or the like generated by the image pickup device drive circuit 17, whereby an image signal generated according to the incident light on the light receiving surface of the image pickup device 11 is output from the image pickup device 11. The signals are sequentially read and input to the signal processing circuit 18. The image signal is converted into a recording signal of a predetermined format in the signal processing circuit 18 and output to the recording circuit 19, and the recording circuit 19
It is recorded on the recording medium M such as a magnetic disk. The image signal processed by the signal processing circuit 18 is displayed on the television monitor T as a moving image. Signal processing circuit 18
The recording circuit 19 is controlled by the system control circuit 10.

The distance measuring circuit 21 measures the distance from the still video camera to the subject SB, and the distance measuring data obtained by the distance measuring circuit 21 is input to the system control circuit 10. That is, the focus drive circuit 15 is controlled based on the distance measurement data, and the automatic focus adjustment is performed as described above.

The zoom switch 22 is provided for the zooming operation of the optical system 12. The release switch 23 performs shutter release to record the image signal obtained by the image pickup device 11 on the recording medium M, and the mode switch 24 is provided to set various operation modes of the still video camera. There is. The zoom switch 22, the release switch 23, and the mode switch 24 are connected to the system control circuit 10, and the system control circuit 10 performs predetermined control based on output signals from these switches.

A strobe device is connected to the system control circuit 10. The strobe device includes a xenon tube 30, an insulated gate bipolar transistor (IGBT) 31,
It has a trigger circuit 40, a charging voltage detection circuit 50, and a charging circuit 60. In the charging circuit 60, the main capacitor 61 is charged by the charging start signal S1 output from the system control circuit 10. Completion of this charging operation is detected by the charging voltage detection circuit 50. At this time,
The charging completion signal S2 is output to the system control circuit 10. The xenon tube 30 can emit light by the output of the charging completion signal S2, and then the system control circuit 10 outputs the light emission trigger signal S3 to turn on the IGBT 31 and cause the xenon tube 30 to emit light.

The structure of the charging circuit 60 will be described. Each electric circuit of the present still video camera is configured to be operated by a single power source. The positive electrode of the battery 62, which is the power source, is connected to the resistor 63, the emitter terminal of the transistor 64, and the primary winding 65a of the transformer 65, respectively. The negative electrode of the battery 62 is connected to the emitter terminal of the transistor 66, the base driving winding 65b and the secondary winding 65c of the transformer 65, and the main capacitor 61.
It is connected to 0.

The base terminal of the transistor 64 has a resistor 6
The voltage of the charging start signal S1 which is connected between No. 3 and 67 and is output from the system control circuit 10 is applied to this base terminal via the resistor 67. The collector terminal of the transistor 64 is connected to the base terminal of the transistor 66 via the resistor 68. Therefore, when the transistor 64 is turned on by the charging start signal S1, a voltage is applied to the base terminal of the transistor 66 and the transistor 66 is turned on, and the primary winding 65a of the transformer 65 is turned on.
A voltage is applied to. At the same time, transformer 6 by induction
A voltage is also generated in the base driving winding 65b of No. 5.

The voltage generated in the base driving winding 65b is applied in the forward direction between the base and emitter of the transistor 66 via the resistors R2, R1 and 69, and becomes a positive feedback voltage which increases the collector current. Therefore, the transistor 66 is rapidly saturated (ON), and the transformer 6
The voltage of the battery 62 is applied to the primary winding 65a of the coil 5, and an exciting current proportional to time flows (reference numeral G in FIG. 2).
1). At this time, the voltage of the secondary winding 65c of the transformer 65 is applied in the reverse direction to the diode (rectifier) 71, so that no current flows in the secondary winding 65c.

When the collector current of the transistor 66 increases and it becomes impossible for the base current to keep the saturation of the transistor 66, the transistor 66 goes out of saturation,
The collector-emitter voltage increases. When the voltage of the primary winding 65a of the transformer 65 decreases due to this voltage increase, the voltage of the base driving winding 65b also decreases, and the collector-emitter voltage further increases. Since this change is positively fed back, the value of the current flowing from the collector terminal to the emitter terminal of the transistor 66 rapidly decreases, and the transistor 66 is turned off (reference numeral F2 in FIG. 2).

At the moment when the transistor 66 changes from the ON state to the OFF state, the direction of the magnetic field in the transformer 65 is also kept the same, so that the voltage of the secondary winding 65c is opposite to the above case and the diode 71 is turned on. Current flows through.

When all the energy stored in the primary side of the transformer 65 is transferred to the secondary side, the current of the diode 71 becomes zero. At this moment, the voltage of each winding of the transformer 65 becomes zero, but since the voltage is applied to the base terminal of the transistor 66 via the transistor 64 and the resistor 68, the transistor 66 is turned on again and the above-described operation is performed. Repeated. In this way, transformer 6
Current flows intermittently in the secondary winding 65c of No. 5 (reference numerals E1, E2, E3, E4 in FIG. 2), and the main capacitor 61
The charge is accumulated in.

That is, the transistor 66, the resistors 68, 6
The ringing choke converter composed of 9, R1, R2, the transformer 65 and the diode 71 constitutes a booster circuit for accumulating charges in the main capacitor 61.

The resistors R1 and R2 provided between the resistor 69 and the base driving winding 65b are the base driving winding 65b.
The switch SW1 is connected in parallel to the resistor R1, and the switch SW2 is connected in parallel to the resistor R2. The on / off state of each of the switches SW1 and SW2 is controlled by the system control circuit 10 and varies depending on the operation mode of the still video camera as described later. The resistance value is
The resistance R2 is larger than the resistance R1.

The main capacitor 61 includes a charging voltage detecting circuit 50, a trigger circuit 40, a xenon tube 30, and an IGBT 31.
It is connected to the. That is, the positive electrode of the main capacitor 61 has one terminal of the neon tube 51 of the charging voltage detection circuit 50, the resistor 41 of the trigger circuit 40, and the xenon tube 30.
Connected to the anode terminal of. The negative electrode of the main capacitor 61 is connected to the neon tube 5 via the resistors 52 and 53.
1 is also connected to the other terminal, the emitter terminal of the transistor 54, the common terminal of the transformer 42 of the trigger circuit 40, and the emitter terminal of the IGBT 31. Between the resistors 52 and 53, the base terminal of the transistor 54 is connected, and the collector terminal of the transistor 54 is connected to the system control circuit 10.

The charging voltage detection circuit 50 includes a neon tube 51,
The neon tube 51 has resistors 52 and 53 and a transistor 54, and the voltage applied to the neon tube 51 exceeds a predetermined value.
That is, the light is turned on when the electric charge accumulated in the main capacitor 61 exceeds a predetermined value. Further, in this state, the transistor 54 is turned on according to the voltage applied to the base terminal of the transistor 54, and the charging completion signal S2 is output to the system control circuit 10.

The trigger circuit 40 has a resistor 41, a trigger transformer 42 and a capacitor 43. The low-voltage side coil of the transformer 42 is connected to the resistor 4 via the capacitor 43.
1 and one end of the resistor 41 is connected to the cathode terminal of the xenon tube 30. The coil on the high voltage side of the transformer 42 is connected to the trigger electrode of the xenon tube 30.

The base terminal of the IGBT 31 is connected to the system control circuit 10, and the light emission trigger signal S3 output from the system control circuit 10 turns on the IGBT 31 and a current flows from the collector terminal to the emitter terminal of the IGBT 31. As a result, the electric charge of the capacitor 43 is discharged, a current flows through the low voltage side coil of the transformer 42, and a trigger pulse is induced in the high voltage side coil. This trigger pulse is applied to the trigger electrode of the xenon tube 30, whereby the electric charge of the main capacitor 61 is discharged, and the xenon tube 30 emits strobe light.

FIG. 2 shows the relationship between the primary winding current supplied from the battery 62 to the primary winding 65b of the transformer 65 and the charging current supplied to the main capacitor 61 in various operation modes of the still video camera. Shows.

The normal recording mode is a mode for recording a still image on a recording medium without monitoring the moving image by the television monitor T, and the monitor recording mode is for recording the still image while monitoring the moving image on the monitor television. A mode for recording on a recording medium.

In the normal recording mode, the steady state refers to a state in which circuits such as the image pickup device 11 are not activated but can immediately shift to the photographing operation, and is a state in which the current consumption is the smallest. That is, the steady current is supplied from the battery 62 to the circuit (not shown) through the lead wire L,
The current value is the smallest as compared with other operation modes described later. When the normal recording mode is stationary, the switch SW1,
Both SW2 are turned on. Therefore, the charging circuit 6
At 0, the base current of the transistor 66 supplied by the voltage generated in the base driving winding 65b bypasses the resistors R2 and R1 and then flows to the base of the transistor 66 through the resistor 69. Larger than the operating mode of. Therefore, the collector current value at which the saturation of the transistor 66 cannot be maintained is also larger than in other operation modes. That is, the peak value of the primary winding current is the maximum, as indicated by the symbol G1. Further, as indicated by the symbol E1, the peak value of the charging current to the main capacitor 61 is also the maximum.

In the normal recording mode, when zoom drive or focus drive is performed, that is, when the optical system 12 is zooming or focusing via the zoom drive circuit 14 or the focus drive circuit 15, these are performed. A driving current for operating the circuits 14 and 15 is required in addition to the steady current. Therefore, when the optical system is driven in the normal recording mode, the switch S
W1 is turned off and switch SW2 is turned on. Therefore, the base drive winding 6 of the transformer 65
The current supplied from 5b bypasses the resistor R2, then flows through the resistors R1 and 69 to the base of the transistor 66, and its current value is smaller than that in the steady state. Therefore, the collector current value at which the saturation of the transistor 66 cannot be maintained is also smaller than in the steady state. That is, as indicated by the symbols G2 and E2, the primary winding current and the main capacitor 6
The peak value of the charging current of 1 is smaller than that in the steady state.

In the monitor recording mode, the image pickup device 11 and the signal processing circuit 18 are driven in order to monitor a moving image in a steady state. Therefore, these circuits 1
A driving current for 1 and 18 is required in addition to the steady current, and this driving current is larger than the driving current for the zooming operation or the focusing operation. In the steady state of the monitor recording mode, the switch SW1 is turned on and the switch SW2 is turned off. Therefore,
The current supplied from the base driving winding 65b of the transformer 65 passes through the resistor R2, then bypasses the resistor R1, and further flows through the resistor 69 to the base of the transistor 66.
The current value becomes smaller than that when the optical system is driven in the normal recording mode. Therefore, the collector current value at which the saturation of the transistor 66 cannot be maintained is smaller than that in the normal recording mode when the optical system is driven. That is, as indicated by the symbols G3 and E3, the primary winding current and the main capacitor 6
The peak value of the charging current of 1 is smaller than that when the optical system is driven in the normal recording mode.

When the optical system is driven in the monitor recording mode, in addition to the current for driving the image pickup device 11 and the signal processing circuit 18, the driving current for operating the zoom driving circuit 14 or the focus driving circuit 15 is a steady current. Others are needed. Therefore, when the optical system is driven in the monitor recording mode, the switches SW1 and SW2 are both turned off, and the current supplied from the base driving winding 65b of the transformer 65 passes through the resistors R2, R1 and 69, and is supplied to the transistor 66. It flows to the base, and its current value becomes minimum compared to other operation modes. Therefore, the transistor 66
Also, the collector current value at which saturation cannot be maintained becomes smaller than in other operation modes. That is, as indicated by the symbols G3 and E4, the primary winding current and the main capacitor 6
The peak value of the charging current of 1 is the minimum.

When the diaphragm drive circuit 16 is driven,
When the distance measuring circuit 21 is driven, the drive current becomes even larger than that in each operation mode described above, so that the supply of the strobe charging current is stopped.

FIG. 3 shows a flow chart for controlling the above-mentioned strobe charging current, and this control is performed by the system control circuit 10. In step 101, it is determined whether the operation mode is the normal recording mode. When the normal recording mode is set, the switch SW2 is set to the ON state in step 102, and when the normal recording mode is not set, that is, when the monitor recording mode is set, the switch SW2 is set to the OFF state in step 103. In step 104, it is determined whether the optical system is driven. When the optical system is driven, step 10
In step 5, the switch SW1 is set to the off state, and when the optical system is not driven, the switch SW1 is set to the on state in step 106.

As a result, the on / off state of the switches SW1 and SW2 in each operation mode is determined, and the magnitude of the strobe charging current is controlled as described above.

As described above, in this embodiment, the magnitude of the strobe charging current is set smaller in the monitor recording mode than in the normal recording mode, and in the normal recording mode and the monitor recording mode, when the optical system is driven, It is smaller than usual. That is, the magnitude of the strobe charging current is reduced when the electric current consumption in the electric circuits other than the strobe device is large. Therefore, the current consumed at one time is reduced, the load on the power source is reduced, and even with a single power source, the strobe device can be used in the monitor recording mode. That is, it is possible to prevent insufficient exposure even when recording is performed on a dark subject. Further, according to the present embodiment, it is not necessary to increase the capacity of the power supply, so that the power supply is not upsized or the weight is not increased.

FIG. 4 is a block circuit diagram of a still video camera equipped with a charge control device according to a second embodiment of the present invention. This embodiment has the same configuration as the first embodiment except that the current detection circuit 73 is provided.

That is, in this embodiment, the magnitude of the strobe charge current is not controlled by the operation mode of the still video camera, but by the output current Im of the battery 62 obtained by the current detection circuit 73. The current detection circuit 73 detects the magnitude of the supply current of the battery 62 using, for example, a magnetic sensor, and outputs a signal S4 according to the magnitude of the supply current to the system control circuit 10. The system control circuit 10 checks the charging state of the main capacitor 61, controls the on / off state of the switches SW1 and SW2 of the charging circuit 60 based on the signal S4, that is, the current value Im, and supplies the strobe charging current to the transformer 65. To be done.

FIG. 5 is a flowchart of the charge control routine. This routine is performed when the power switch is switched from the off state to the on state, when the release switch is pressed halfway to perform the photometry and distance measurement operations, and when the recording operation by the recording circuit 19 is completed. Interrupt processing is performed during execution of a main routine (not shown). Further, this charging control routine is performed periodically (for example, 10 m
interrupt processing is performed every (s).

In step 201, the charging start signal S1 is set to the H (high) state, and the charging circuit 60 is stopped.
This is because the current detected by the current detection circuit 73 must be the current when the charging circuit 60 is not operating. In step 202, the charging completion signal S2 output from the charging voltage detection circuit 50 is read.
In step 203, it is determined whether the charging completion signal S2 is "H" or "L". When the charge completion signal S2 is "L", the charging of the main capacitor 61 has been completed, so this routine ends. However, when the charge completion signal S2 is "H", step 204 and the following steps are executed. Charging control for the main capacitor 61 is performed.

In step 204, the signal S4 corresponding to the current value Im output from the current detection circuit 73 is read. If it is determined in step 205 that the current value Im is less than or equal to the first reference value I ₁ , both switches SW1 and SW2 are set to the on state in step 206, and charging is started from the system control circuit 10 in step 207. The signal S1 is output and the main capacitor 61
Will start charging. This completes this routine. That is, the charging is performed in the same state as in the normal state of the normal recording mode shown in FIG.

On the other hand, when it is determined in step 205 that the current value Im is higher than the first reference value I ₁ , it is determined in step 208 whether the current value Im is the second reference value I ₂ or less. To be done. If the current value Im is less than or equal to the second reference value I ₂ , the switch SW1 is set to the off state and the switch SW2 is determined in step 209.
Is set to an ON state, and charging of the main capacitor 61 is started in step 207. That is, charging is performed in the same state as when the optical system is driven in the normal recording mode shown in FIG.

In step 208, the current value Im becomes the second value.
If it is determined that the value is larger than the reference value I ₂ of, the switches SW1 and SW2 are both set to the off state in step 210, and the charging of the main capacitor 61 is started in step 207. That is, charging is performed in the same state as when the optical system is driven in the monitor recording mode shown in FIG.

The first reference value I ₁ is smaller than the second reference value I ₂ . Therefore, the current consumption in the electric circuits other than the strobe device is the smallest in the case where step 206 is executed among steps 206, 209 and 210,
Most often, step 210 is executed.

As described above, in the second embodiment, the magnitude of the charging current can be selected in three ways, but the same effect as in the first embodiment can be obtained.

[0043]

As described above, according to the present invention, it is possible to use the strobe device even in the monitor recording mode without increasing the shape of the power source or increasing the weight. To be

[Brief description of drawings]

FIG. 1 is a circuit diagram of a still video camera according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a primary winding current and a strobe charging current in various operation modes of a still video camera.

FIG. 3 is a flowchart showing control of a strobe charging current in the first embodiment.

FIG. 4 is a circuit diagram showing a second embodiment of the present invention.

FIG. 5 is a flowchart showing control of a strobe charging current in the second embodiment.

[Explanation of symbols]

 30 Xenon tube 40 Trigger circuit 50 Charge voltage detection circuit 60 Charge circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H04N 5/238 Z

Claims (4)

[Claims] 1. An operation control means for controlling a still video camera in a predetermined operation mode, a means for accumulating charges for causing a strobe device to emit light, and an operation control means for supplying a charging current to the charge accumulating means. A single power supply and a current control means for controlling the magnitude of the charging current supplied from the power supply to the charge storage means are provided, and the current control means, when the current consumption by the operation control means is relatively large, A charge control device for a still video camera, characterized in that the magnitude of a charge current is relatively reduced. 2. The operation mode includes a monitor recording mode in which an image obtained by a still video camera is monitored by a monitor television and a normal recording mode in which an image is recorded on a recording medium without monitoring, and the current control means 2. The charge control device for a still video camera according to claim 1, wherein the charging current in the monitor recording mode is relatively smaller than that in the normal recording mode. 3. The current control means changes the charging current according to the operation mode.
The charge control device for a still video camera described in 1. 4. A means for accumulating charges for causing a strobe device to emit light, a power source for supplying a current to the charge accumulating means, and a magnitude of a charging current supplied from the power source to the charge accumulating means. A current control means for controlling and a means for detecting the magnitude of the current supplied from the power source are provided, and the current control means is such that the magnitude of the charging current when the current value detected by the detection means is relatively large. A charging control device for a still video camera, which is characterized in that it is relatively small.