JPS63246081A - Still video camera - Google Patents

Abstract

PURPOSE:To realize a camera of a power supply circuit with small sized space and low power consumption by using a DC/DC converter subject to on/off control in response to the status signal of a power switch from a power supply of a still video camera. CONSTITUTION:With a power switch SW turned off, a system control circuit 22 keeps giving an operation control signal Ct to stop the oscillation of a DC/DC converter 21. Thus, the power supply of the circuit 22 is energized directly from a battery Ba. Since CMOS active element is used for the circuit component, the power consumption is not a problem. In turning on the switch SW, the circuit 22 gives a signal Ct to start the oscillation to the converter 21. Thus, the converter 21 starts the oscillation to supply power to electronic circuits 23, 24. Since no power control transistor is required, the camera use power supply circuit with small size and low power consumption is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a still video camera having a power supply circuit consisting of a DC/DC converter and a control circuit for controlling the converter.

(Conventional technology) In recent years, with the advancement and development of electronics technology, cameras, which used to consist mostly of mechanical parts, have been replaced with electronic circuits to a large extent, including the exposure control circuit. Oops. FIG. 1 is a block diagram showing the configuration of an electronic camera currently on the market. The figure shows the configuration until the video input from the lens is recorded on the film. The video input from the first lens 1 enters the shutter 6 via the aperture 2, the second lens 3, the box 4, and the mirror 5, and when the shutter 6 is momentarily opened, the video signal is is recorded on film 7.

Even now, the parts that make up the main flow as described above are mostly made up of mechanical parts. however,
A considerable portion of the parts that do not constitute the main flow have been digitized.

For example, an aperture control device 8 that controls the aperture 2. A control device 9 and the like that control the mirror 5 and shutter 6 are composed of electronic circuits. These control devices are controlled by a processor 10, and the processor 10 itself is configured with an electronic circuit using a microcomputer or the like. For example, the aperture control mechanism will be explained as follows. A portion of the reflected light from the mirror 5 is converted into an electrical signal by the optical sensor 11 and then enters the processor 10 . processor 10
receives this photoelectric conversion signal, calculates the amount of light received, and sends a control signal to the diaphragm control circuit 8 so as to obtain the optimum light reception m. The aperture control circuit 8 receives this control signal and sets the aperture 2 to the optimum aperture amount. Although not shown in the figure, a still video camera that uses a solid-state AM element such as a COD in its image carrier system and is even more electronically advanced also has 51 pixels.

As described above, most of the components of recent cameras are electronic. Therefore, the electronic part (
A power source is required to operate (mainly electronic circuits). Reference numeral 12 in FIG. 1 is a power supply circuit for this purpose, and power is supplied to each circuit. Since cameras are generally portable, batteries are also used as a power source. As for the types of batteries, in addition to induced manganese batteries, alkaline batteries, mercury batteries, lithium batteries, etc., rechargeable secondary batteries are also used. By the way, in a still video camera, the voltage values used by each system, such as the aperture control system and the processor system, are different, so it is necessary to convert the battery (source) output to a power supply circuit with multiple outputs. Generally, a method using a DC/DC converter is adopted.

FIG. 2 is a block diagram showing an example of a power supply circuit portion of a conventional still video camera. In the figure, 3a is the battery, 21G; tDc/DC=+inverter, Tr is the battery 3
22 is a system control circuit that receives power supply from the DC/DC converter 21 and performs various controls; 23 and 24 are DC /DC converter 21 and receives power from the IDC/DC converter 21; 25 is a motor whose rotation is controlled by the system control circuit 22; 26;
is a solenoid whose operation is similarly controlled by the system control circuit 22, and SW is a normally open power switch. The power switch SW is connected between the base of the power supply control circuit transistor T" and ground. For example, a microcomputer is used as the system control circuit 22. The number of electronic circuits is limited to those shown in 23.24. The motor 25 is used to drive the magnetic disk of a still video camera, and the solenoid 26 is used to move the position of the head that records image signals on the magnetic disk of the still video camera. used for purposes.

In the power supply circuit section configured in this way, when the power switch SW is turned on, the power supply control transistor T'
The base of the transistor T is grounded through the resistor R1, and a forward voltage is supplied to the base from the bias resistor R2, so the transistor T is turned on. When the power supply control transistor Tr is turned on, the DC/DC A battery [3a is connected to the converter 21 via the transistor Tr. As a result, the DC/DC converter 21 starts operating, and power supplies with different voltage values are supplied to the system control circuit 22, electronic circuits 23, 24, etc. supply.

The system control circuit 22 detects the state of, for example, a release switch (not shown), and keeps the power supply control transistor Tr in the on state as necessary.

When the series of sequences is completed, the power switch SW is turned off after a certain period of time.

(Problems to be Solved by the Invention) As explained above, the power supply circuit of a conventional still video camera employs a method of directly switching the voltage supply to the DC/DC converter, as shown in Figure 2. In the circuit, direct switching is performed by the power supply control transistor 7r. As still video cameras are becoming increasingly electronic, the power supplied to electronic circuits and actuators is also increasing, and for example, a current capacity of several amperes is now required.

When the current capacity increases in this way, the following problems occur in the system in which power supply switching is performed using transistors as shown in FIG.

■Switching large currents requires large-capacity transistors, making it difficult to secure space. Still video cameras are designed to be portable, and increasing the size of the camera is undesirable. Also, when a large current flows,
As the transistor generates more heat, heat dissipation measures are also required. Furthermore, since it is necessary to provide a drive circuit for driving the transistors, the circuit configuration becomes complicated.

(2) As the current increases, the voltage drop VCE between the collector and emitter of the transistor increases, and the power consumption of the transistor increases. This power consumption is wasteful to the power supply circuit itself and accelerates battery consumption. Furthermore,
When the collector-emitter voltage Vcε of the transistor increases, the input voltage of the DC/DC converter decreases by that amount, and the conversion efficiency decreases.

The present invention has been made in view of these points, and an object thereof is to realize a still video camera having an efficient power supply circuit that does not require a power supply control transistor.

(Means for Solving the Problems) The present invention that achieves the above object includes a DC/DC converter to which a power supply power supply is directly connected, and a DC/DC converter that is directly driven by the power supply power supply or another power supply, i! receives the state signal of the power switch and provides an operation control signal for on/off operation to the DC/DC converter; IJ 111
The present invention is characterized by having a power supply circuit consisting of a circuit.

In addition, to turn on and off the DC/DC converter, the operation control signal output from the control circuit is added to the built-in oscillator of the DC/DC converter to control the oscillation operation, or the built-in oscillator of the DC/DC converter is In addition to the control circuit, the on/off of the control circuit may be controlled, or the DC
The present invention is characterized in that it controls the supply of power in addition to the power supply path of the /DC converter.

(Function) In the still video camera according to the present invention, the control circuit outputs an operation control signal for turning on and off the DC/DC converter according to the state signal of the power switch. The on/off of this DC/DC converter is controlled by the built-in oscillator of the DC/DC converter.

This is done by adding an operation control signal to either the built-in control circuit or the power supply path.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a configuration block diagram showing a power supply circuit portion in an embodiment of the present invention. In the figure, the same parts as in FIG. 2 are designated by the same reference numerals. Battery 9a is DC/DCC/
2, the system control circuit 22 is directly driven by the battery 3a, and the power switch SW is directly connected to the system control circuit 22.
and ground. Then, an operation control signal Qt is applied from the system control circuit 22 to the DC/DCC converter 21 to control the DC/DC converter 21.
It is designed to perform on/off control of the operation. The operation of the circuit configured as described above will be explained as follows.

When the power switch SW is in the off state, the system control circuit 22 continues to supply the operation control signal Ct to the DC/DC converter 21 to stop its oscillation operation. That is, in the circuit of the present invention, when the power is turned off, the DC/DCC
Since it is necessary to constantly supply the operation stop signal Ct to the computer 21, the power for driving the system control circuit 22 is taken directly from the battery [3a]. In this case, the amount of power consumed by the system control circuit 22 when the power is turned off becomes a problem, but if the circuit is designed using low power consumption type 0MO8 type active elements as circuit elements,
Power consumption is not a particular problem.

If you need to turn on the power, press the power switch SW.
Turn on. When the system control circuit 22 receives a power-on signal from the power switch Sw, it sends an operation control signal C [D C/D
C converter 21. As a result, D C/D C
Converter 21 starts oscillating operation, and electronic circuit 23.2
Supply power to 4th class. Here, the operation control signal @C given from the system control circuit 22 to the DC/DC converter 21 is "0" level when the oscillation operation of the DC/DC converter 21 is stopped;
When performing an oscillation operation, the signal may be set to a ", 1" level. Or it may be the other way around.

FIG. 4 is a configuration block diagram showing a power supply circuit portion in another embodiment of the present invention. In the figure, the same parts as in FIG. 3 are denoted by the same reference numerals. In the figure, Bb is a battery provided separately from the battery 3a, and the power of the battery Bb is supplied to the system control circuit 22 through a forward connection circuit formed by a diode D. For example, a lithium battery is used as the battery Bb. Furthermore, the output of the DC/DC converter 21 is also connected to the system control circuit 22 so that it can supply power. And DC/DC converter 21
The output of is connected to the cathode side of diode D. The operation of the circuit configured in this way will be explained below.

When the power is off, power is supplied from the battery Bb to the system control circuit 22, and the system control circuit 22 continues to provide the operation control signal Ct for stopping the operation to the DC/DC converter 21. Here, when the power switch SW is turned on, the system control circuit 2
2, an operation control signal Ct for operation is given to the DC/DC converter 21. As a result, the DC/DC converter 21 starts oscillating operation, and the electronic circuits 23 and 24
Start supplying power to etc. The DC/DC converter 21 also supplies power to the system control circuit 22. Here, if the voltage applied to the DC/DC converter 21 is made slightly higher than the value of the battery Bb, the diode D will be biased in the opposite direction, so that the power supply from the battery Bb will be automatically cut off. According to the circuit shown in the figure, when the power is turned off, the system control circuit 22 is backed up by the battery Bb, so even if the voltage value of the power supply battery 13a decreases, the system control circuit 22 can operate normally regardless of this. Keep it. For example, normal operation of timer counters and the like is always maintained.

Next, a method of turning on and off the DC/DC converter 21 using the operation control signal Ct will be explained.

FIG. 5 is a block diagram showing the general configuration of the DC/DC converter 21. As shown in FIG. In the figure, 31 is an oscillator that oscillates pulses, 32 is a control element that converts the input voltage into a predetermined voltage output, 33 is a reference voltage source, 34 is a sampling circuit that samples the output voltage, and 35 is supplied from the reference voltage source 33. An error amplifier 36 is a control circuit that receives the outputs of the oscillator 31 and the error amplifier 35 and compares the sampling output of the sampling circuit 34 with the reference voltage. A control signal is given from the control circuit 36 to the control element 32 to control switching of the input voltage.

As a method of stopping the oscillation operation of a DC/DC converter having such a configuration, as shown in the figure, there is a method of giving an operation control signal to the oscillator 31 to stop the oscillation of the oscillator itself, and a method of stopping the oscillation of the oscillator itself, as shown in the figure. There is a method of applying a control signal Ct to stop the switching operation of the control element 32, or a method of applying an operation control signal Ct to the power supply path to bring the entire circuit into a non-voltage state. A method that can cut off the control element 32 with the minimum power may be selected from among these various methods.

In the above explanation, one operation control signal Ct is used to control D.
Although the case where the entire C/DC converter is controlled is taken as an example, it is also possible to control each voltage output at the necessary timing using a plurality of operation control signals.

(Effects of the Invention) As explained in detail above, according to the present invention, D C/
By adopting a configuration that controls the on/off operation of the DC converter, it is possible to realize a still video camera having an efficient M source circuit that does not require a power supply control transistor.

That is, according to the present invention, since a power supply control transistor is not required, it is advantageous in terms of space, power consumption, etc. Further, according to the present invention, the drop in the input voltage of the DC/DC converter is reduced, so that the DC/DC converter can be used efficiently.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an electronic camera, FIG. 2 is a configuration block diagram showing a conventional example of a power circuit section of a conventional still video camera, and FIG. 3 is a block diagram showing a power circuit section in an embodiment of the present invention. FIG. 4 is a configuration block diagram showing a power supply circuit portion in another embodiment of the present invention, and FIG. 5 is a block diagram showing a general configuration of an 0C/DC converter. 21...D C/DC converter 22...System control circuit 23.24...Electronic circuit 25...Motor 26...Solenoid 31.
...departure! Ft device 32...control element 33...
Reference voltage source 34...sampling circuit 35...
Error amplifier 36...control circuit Ba, Bb...
Battery SW...Power switch Rt, R...Resistor R...Power supply control transistor Patent applicant: 2 Ka Co., Ltd.
Ceremony Attorney Patent Attorney Ijima
Fuji Jigai 1 person

Claims (4)

[Claims] (1) A DC/DC converter to which a power supply power supply is directly connected, and a DC/DC converter that is directly driven by the power supply power supply or another power supply and receives a state signal from a power switch.
A still video camera having a power supply circuit including a control circuit that provides an operation control signal for on/off operation to a DC converter. (2) The still video camera according to claim 1, wherein the operation control signal is applied to a built-in oscillator of the DC/DC converter to control the oscillation operation. (3) The still video camera according to claim 1, wherein the operation control signal is added to a built-in control circuit of the DC/DC converter to control on/off of the control circuit. (4) The still video camera according to claim 1, wherein the operation control signal is added to a power supply path of a DC/DC converter to control the supply of power.