JPH0132030Y2 - - Google Patents

Description

[Detailed explanation of the idea] This invention relates to a power supply holding device for a camera.

Generally, in order to prevent unnecessary power consumption, the power supply holding device that supplies power to the camera's electronic circuit is connected to the power supply by the mirror up, for example in the case of a single-lens reflex camera, and the power supply is connected to the power supply when the shutter rear curtain starts running. be separated from Further, this power supply holding device includes a determination unit that compares the power supply voltage with a reference voltage, and when the power supply voltage becomes lower than the reference voltage, it is disconnected from the power supply so as not to operate.

However, in a single-lens reflex camera, after photographing is completed, the mirror that has been raised lowers and returns to the state where it reflects the incident light and sends it to the viewfinder. At this time, when the mirror bounces, the switch will chatter and the power holding device will be connected to the power supply again.
It may become operational. Therefore, there is a possibility that the power supply voltage is wasted.

For example, there is a technique disclosed in Japanese Patent Application Laid-Open No. 13773/1983 to prevent the power from being wasted due to repeated opening and closing operations of the switch. This conventional technology includes a first switch that is turned on when film winding is completed and turned off when the leading shutter curtain ends, and a second switch that is turned on when the shutter release button is pressed to the second stage. The power is maintained only when both switches are turned on.

According to this conventional technology, even if the shutter release button is pressed in the second step by mistake after the front shutter curtain has run but before the film is wound, the power is not retained and there is no needless power consumption. There is.

However, in order to prevent power consumption, a first switch must be provided, which makes the camera complicated and increases costs.

This invention was made in order to deal with the above-mentioned circumstances, and the purpose is to provide a camera power holding device that has a simple configuration and prevents wasteful power consumption without the need to install a new switch. It is.

Hereinafter, one embodiment of the camera power holding device according to this invention will be described with reference to the drawings. Note that this embodiment shows a case where the present invention is applied to, for example, an aperture-priority automatic exposure single-lens reflex camera.

In the figure, the positive terminal of a power supply battery 10 is connected to one end of a capacitor 14 via a mirror switch 12 as a first switch means. The other end of the capacitor 14 is connected to the negative terminal of the power supply battery 10 via resistors 16 and 18 in series. The connection point between the mirror switch 12 and the capacitor 14 is connected to a resistor 20.
It is connected to the negative terminal of the power supply battery 10 via. A connection point between the resistors 16 and 18 is connected to the base of an NPN transistor 22 as a first semiconductor switching element, and is also connected to the negative terminal of the power supply battery 10 via a resistor 24.

The positive terminal of the power supply battery 10 is connected in series through a switch 26 as a second switch means and a resistor 28.
Connected to the collector of the NPN transistor 30. The connection point between the switch 26 and the resistor 28 is the second
It is connected to the base of an NPN type transistor 32 as a semiconductor switching element. The emitter of transistor 32 is connected to the collector of transistor 22, and the collector of transistor 32 is connected to the collector of NPN type transistor 36 and the collector of PNP transistor 38 via resistor 34. Transistor 36 has its base
The collectors are short-circuited, and the bases are connected to the bases of PNP transistors 40, 42, 44, 46, and 48, respectively.

The emitter of transistor 38 is connected to the collector of NPN transistor 50. The base of transistor 38 is connected to the collector of transistor 40 and to the negative terminal of power supply battery 10 via resistors 52 and 54 in series. The connection point between the resistors 52 and 54 is connected to the transistors 30 and 5.
0 and the base of NPN type transistor 56. NPN type transistor 22,
Emitters 30, 50, and 56 are connected to the negative terminal of the power battery 10. PNP type transistor 36,
Each emitter of 40, 42, 44, 46, 48 is
Each is connected to the positive terminal of the power supply battery 10.

Of the above-mentioned parts, the transistors 36, 3
8, 40, 50 and resistors 52, 54 constitute a power supply holding circuit 57. Further, the transistors 36, 40, 42, 44, 46, and 48 constitute a current mirror circuit.

The collector of the transistor 56 is connected to a resistor 58,6.
0 in series to the positive terminal of the power supply battery 10. A connection point between the resistors 58 and 60 is connected to a non-inverting input terminal (+) of a comparator 62. A first reference voltage terminal 63 is connected to the inverting input terminal (−) of the comparator 62 . A power supply terminal of the comparator 62 is connected to the collector of the transistor 42 and the negative terminal of the power supply battery 10 . The output terminal of the comparator 62 is connected to the AND
It is connected to one input terminal of gate 66.

The connection point between the switch 26 and the resistor 28 is AND
The other input terminal of gate 66 and AND gate 68
is connected to one input end of the Pulse generation circuit 70
The output terminal of is connected to the other input terminal of AND gate 68. Each output terminal of the AND gates 66 and 68 is
They are connected to the first and second input terminals of the NOR gate 72, respectively. The output terminal of the NOR gate 72 is connected to the base of the transistor 50 of the power supply holding circuit 57.

Of the above-mentioned parts, the circuit consisting of the NOR gate 72 and the transistor 50 constitutes a power hold/release circuit. Note that the transistor 50 is also used as a power holding circuit 57 and a power holding release circuit.

On the other hand, a photodiode 74 as a light receiving element
The anode of is connected to the non-inverting input terminal (+) of the operational amplifier 76 and the second reference voltage terminal 78 .
The cathode of the photodiode 74 is connected to the inverting input terminal (-) of the operational amplifier 76 . A power supply terminal of the operational amplifier 76 is connected to the collector of the transistor 44 and the negative terminal of the power supply battery 10 . The output end of operational amplifier 76 is connected to one end of capacitor 79 and the non-inverting input end (+) of comparator 80 . The other end of the capacitor 79 is connected to the inverting input terminal (-) of the operational amplifier 76. A switch 82 as a switching element for starting integration is connected in parallel to the capacitor 79. switch 8
The control end of No. 2 is connected to the connection point between the switch 26 and the resistor 28.

The collector of the transistor 46 is connected to a variable resistor 84.
and a constant current source 86 in series to the negative terminal of the power supply battery 10. The variable end of the variable resistor 84 is
It is connected to the inverting input terminal (-) of the comparator 80. A power supply terminal of comparator 80 is connected to the collector of transistor 48 and the negative terminal of power supply battery 10 . The output terminal of comparator 80 is NOR
connected to the third input terminal of the gate 72, and
It is connected to the base of a PNP transistor 90 via a resistor 88. The transistor 90 has its base and emitter short-circuited via a resistor 92.
Also, the emitter is the shutter rear curtain locking magnet 9.
4 to the positive terminal of the power supply battery 10.
The collector of transistor 90 is connected to the negative terminal of power supply battery 10 .

Among the above-mentioned parts, the photodiode 74,
Operational amplifier 76, capacitor 79, switch 8
2. A circuit consisting of a comparator 80, a variable resistor 84, and a constant current source 86 constitutes an exposure control circuit.

Next, the operation in such a configuration will be explained. Here, the aperture has already been narrowed down. A mirror switch 12 serving as a first switch means is controlled to open and close in conjunction with the up and down movement of the mirror, and is opened when the mirror is lowered (second state) and closed when the mirror is raised (first state). The switch 26, which serves as a second switch means, is closed when the film is wound (first state), and opened in response to the start of travel of the leading shutter curtain (second state). The switch 82, which serves as a switching element for starting integration, is closed when the control terminal is at the "H" level, and opened when the control terminal is at the "L" level. The pulse generating circuit 70 is activated in response to the shutter operation, for example, in response to the rise of the mirror, and outputs an "H" level signal after 50 msec.

In the initial state when the film is wound, the switches 12 and 26 are in the state shown. That is, the mirror switch (first switch means) 12 is in the second state, and the switch (second switch means) 26 is in the first state. Here, since the mirror switch 12 is open, the transistor 22 is in a non-conducting state, and even if the switch 26 is closed, the transistor 32 is not in a conducting state. Therefore, the transistors 36, 38, and 50 do not become conductive, and the power supply holding circuit 57 is not energized, so that there is no wasteful power consumption.

When the release button is pressed to take a photograph, the mirror moves up and the mirror switch 12 is closed.
That is, the mirror switch (first switch means)
12 changes from the second state to the first state. This causes the capacitor 1 to connect to the base of the transistor 22.
A trigger pulse is supplied from 4 through a resistor 16. Since switch 26 is closed, transistors 22 and 32 are conductive and current flows from transistor 32 through resistor 34 to the base of transistor 36.

As a result, transistor 40 becomes conductive, transistors 38 and 50 also become conductive, and transistors 42, 44, 46, and 48 also become conductive. Here, if the supply of the trigger pulse is stopped, the transistors 22 and 32 return to the non-conducting state, but the transistors 36, 38, 40, 5
Since the circuit 0 forms a thyristor structure, it continues to be in a conductive state, and the power supply holding circuit 57 is energized and becomes an operating state. Further, in response to the rise of the mirror, the pulse generating circuit 70 starts a timing operation.

When the power supply holding circuit 57 becomes operational, the transistor 56 also becomes conductive, and a divided voltage of the power supply voltage is generated at the connection point between the resistors 60 and 58. A comparator 62 compares this voltage with a first reference voltage;
If the voltage is below the reference voltage, the comparator 62 outputs an "H" level signal. Since this "H" level signal is supplied to one input terminal of AND gate 66 via inverter 64, the output terminal of AND gate 66 is at "L" level. Since the output signal of the pulse generating circuit 70 is still at the "L" level, the output terminal of the AND gate 68 is at the "L" level. In addition, since the output terminal of the comparator 80 is also at the "L" level, the output terminal of the NOR gate 72 as a power hold release circuit, that is, the base of the transistor 50 is at the "H" level, and the transistor 50 is kept in a conductive state. , the power supply holding circuit 57 maintains the operating state.

Here, when the power supply voltage decreases, the output signal of the comparator 62 becomes "L" level. Before the shutter operation, the switch 26 is still closed, so both input terminals of the AND gate 66 are at the "H" level, and its output terminal is at the "H" level. When even one input terminal of the NOR gate 72 serving as a power supply release circuit becomes "H" level, its output terminal becomes "L" level. Therefore, the transistor 50 becomes non-conductive, and the power supply holding circuit 57 does not operate. Therefore, when the power supply voltage drops, the shutter operation is not performed, and it is possible to prevent a photograph from being taken without proper exposure control.

The actual shutter operation begins after this mirror rises.
This is done after a short period of time (several milliseconds) has elapsed. First, the leading shutter curtain starts running. At this time, the output signal of the comparator 80 is still at the "L" level, the transistor 90 is kept conductive, and the shutter rear curtain is locked to the magnet 94. As a result, the switch 26 is opened, so that one input terminal of each of the AND gates 66 and 68 goes to the "L" level, and the output terminal goes to the "L" level. While the shutter is operating, the output terminal of the comparator 80 is still at the "L" level, so the NOR gate 72 acts as a power hold release circuit.
All three input terminals are at "L" level, the output terminal thereof is kept at "H" level, and the power supply holding circuit 57 maintains the operating state.

On the other hand, even if the mirror rises due to mechanical failure,
If the front shutter curtain cannot move, turn switch 2.
6 is not opened, AND gates 66, 68
One input terminal of each remains at H level. When 50 msec elapses after the mirror rises, the output signal of the pulse generation circuit 70 goes to the "H" level, and both input terminals of the AND gate 68 go to the "H" level, so its output terminal goes to the "H" level. .
As a result, the output terminal of the NOR gate 72 serving as the power hold release circuit goes to "L" level, the power hold circuit 57 becomes inactive, and wasteful power consumption is prevented.

On the other hand, if the front shutter curtain runs normally, the switch 26 is opened and the AND gates 66 and 68 are opened.
One input terminal of each becomes "L" level.
Therefore, even if the output signal of the pulse generating circuit 70 goes to the "H" level, the output terminal of the AND gate 68 remains at the "L" level. In addition, the power supply voltage decreases and the output signal of the comparator 62 becomes “L”.
Even if the output terminal reaches the "L" level, the output terminal of the AND gate 66 remains at the "L" level. While the shutter is operating,
Since the output terminal of the comparator 80 is also at "L" level, the NOR gate 7 functions as a power hold release circuit.
The output terminal of the power supply holding circuit 57 is at "H" level, and the operation of the power supply holding circuit 57 is not stopped. Even if the power supply voltage drops, the power supply holding circuit 57 remains in operation while the shutter is operating.
The reason for continuing the operation is that the determination voltage for determining the power supply voltage is set to a large value with some margin in mind. After the exposure has started,
Stopping the shutter operation wastes the film.

Switch 26 is activated in response to the start of travel of the front shutter curtain.
When is opened, that is, when the switch (second switch means) 26 changes from the first state to the second state, the switch 82, which serves as the integration start switching element, is opened because the control terminal becomes "L" level. . As a result, the photocurrent of the photodiode 74 is integrated by an integrator consisting of the operational amplifier 76 and the capacitor 79, and the potential at the output end of the operational amplifier 76 gradually increases. The variable resistor 84 is changed according to the film sensitivity, and when the potential at the output end of the operational amplifier 76 exceeds a predetermined potential determined by the variable resistor 84, the output signal of the comparator 80 as the output section of the exposure control circuit becomes "H". become the level.

As a result, the transistor 90 becomes non-conductive, the energization of the shutter trailing curtain locking magnet 94 is stopped, the shutter trailing curtain starts running, and the shutter operation and exposure are completed. When the output signal of the comparator 80 becomes "H" level, the output terminal of the NOR gate 72 as a power hold release circuit goes "L".
level, and the power supply holding circuit 57 stops operating. This also prevents wasteful power consumption after the shutter operation is completed.

When the trailing shutter curtain finishes running, the mirror is lowered and the mirror switch 12 is released. However, for example, the mirror may bounce, causing the mirror switch 12 to chatter and close again. However, since the switch 26 as the second switching means is still open, the transistor 32 is in a non-conducting state, and even if a trigger pulse is supplied to the base of the transistor 22, the power supply holding circuit 57 will not malfunction. . When the next film is wound, the switch 26 is closed and the above-described operation is repeated.

Note that although the above description has been made regarding a single-lens reflex camera, this invention can also be applied to a lens shutter type camera. In that case, a switch that is closed when the release button is pressed is provided in place of the mirror switch 12, and the switch 2
6 may be opened and closed according to the operation of the lens shutter. Further, this invention may be applied to a manual exposure control type camera.

As explained above, according to this invention, the output of the switch (second switch means) that takes the timing of the start of integration, which has been used in the past, is used, so there is no need to provide a new switch.
It is possible to provide a power supply holding device for a camera that has a simple configuration and prevents wasteful power consumption.

[Brief explanation of the drawing]

The figure is a circuit diagram of an embodiment of a power supply holding device for a camera according to this invention. 10...Power supply battery, 12...Mirror switch (first switching means), 22...Transistor (first semiconductor switching element), 26...Switch (second switching means), 32...Transistor (second semiconductor switching element) element), 57...Power supply hold circuit, 72...NOR gate (power supply release circuit), 74...Photodiode, 76...Operation amplifier, 79...Capacitor, 80...Comparator, 82...Switch (integrator) starting switching element), 94...Shutter trailing curtain locking magnet 94.

Claims (1)

[Claims for Utility Model Registration] A power supply terminal, a first switch means that enters a first state in response to shutter release operation and a second state in response to closing of the shutter, and a first switch means that enters a second state in response to film winding. a second switch means that enters the first state and enters the second state in response to the start of opening of the shutter; respective control electrodes are connected to the first and second switch means, and the first and second switch means enter the first state. first and second semiconductor switching elements connected in series are conductive when the first and second semiconductor switching elements are connected to the first and second semiconductor switching elements, and when both the first and second semiconductor switching elements are conductive, a power supply holding circuit that forms a power supply path from the power supply terminal to the camera element and maintains the power supply state; and a power supply holding circuit that is connected to the second switch means and performs an integral operation in response to a second state of the second switch means. The exposure control circuit includes an exposure control circuit having a switching element for starting integration, and a power supply holding release circuit that releases the power supply holding state of the power supply holding circuit in response to the completion of the shutter operation by the output of the exposure control circuit. A power supply holding device for the camera.