JPH058598Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a charge motor drive circuit for a camera.

In cameras that electrically control shutter charging, shutter release, and other operations, when the battery used as a power source becomes exhausted, the operation stops due to voltage drop.Especially when charging the mirror and shutter, the charging motor etc. It is well known that because a large current needs to be passed through the battery, the voltage drop is significant and operation is likely to stop during charging.

Therefore, even if the operation stops during charging due to a drop in the power supply voltage, there is a need for a camera that can continue the charging operation when the power supply voltage is restored. In cameras that start charging with a recording completion signal generated from the control system upon completion, if the operation stops during charging due to a drop in power supply voltage, the camera will not start charging unless the recording completion signal is generated again after the voltage is restored. It becomes impossible.

The present invention was developed in view of the above points, and in a camera that starts the charge motor with a recording completion signal, even if the operation stops during charging due to a drop in power supply voltage, the power supply can be turned off once.
It is an object of the present invention to provide a charge motor drive circuit for a camera that is capable of continuously performing a charge operation by turning it off and turning it on again after the power supply voltage is restored.

Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, numeral 1 is a control system, which generates a pulse-like signal when recording to a recording medium (not shown) is completed.
The control system 1 outputs a high level recording completion signal, and when the recording completion signal is not output, the output state of the control system 1 is low level.

2 is a restart signal output circuit, and the control system 1
It also has the function of integrating the recording completion signal generated from the charge motor 5, and also outputs a restart signal for restarting the charge motor 5 when the charge motor 5 stops operating due to a drop in power supply voltage and then the power is restored. This is what is output.

3 is a restart signal output circuit 2 from the control system 1;
This is a charge signal holding circuit that latches the recording completion signal inputted via the restart signal output circuit 2 and the restart signal inputted from the restart signal output circuit 2.

Connected to the charge signal holding circuit 3 are a switch 4 for switching the circuit between an operable state and an inoperable state, and the aforementioned charge motor 5 for performing a charging operation of the shutter.

When the switch 4 detects that recording on a recording medium (not shown), such as a film, is completed, the switch 4 becomes the contact a side, that is, the closed state (second state), and when the charging operation of the shutter (not shown) is completed. Then, the contact b side becomes the open state (first state).

Next, the operation of the charge motor drive circuit of this embodiment will be briefly explained based on the block diagram of FIG. 1 explained above.

When the release operation is completed, the switch 4 changes from the open state (first state) to the closed state (second state).
The charge signal holding circuit 3 becomes operational. Therefore, when recording on the recording medium is completed, a recording completion signal is generated from the control system 1, and when the recording completion signal integrated by the restart signal output circuit 2 is input to the charge signal holding circuit 3, a charge signal is generated. The holding circuit 3 is activated and the charge motor 5 is started. When charging is completed, the switch 4 returns to the first state, so the charge signal holding circuit 3 stops operating and the charge motor 5 stops.

Also, if the operation stops during charging due to a drop in power supply voltage, switch 4 will remain in the second state, so either replace the battery with a new one or turn off the power and wait for the battery to recover. If the recording completion signal is not generated from the control system 1, a restart signal will be generated from the restart signal output circuit 2, so this initial pulse will cause the charge signal holding circuit 3 to operate again. The charge motor 5 is started to continue charging.

Next, a specific circuit example of the charge motor drive circuit of this embodiment shown as a block in FIG.
This will be explained with reference to the figures.

First, the operation in steady state will be explained.

When the release operation is performed, the switch 4 moves from the contact b side, that is, the open state (first state) to the contact a side, that is, the closed state (second state), as the mirror (not shown) rises.
state). When recording on the recording medium is completed, a pulse-like Hi-level recording completion signal is generated from the control system 1 and is input to the restart signal output circuit 2 composed of a resistor 6, a capacitor 7, and a resistor 8. The recording completion signal integrated by the restart signal output circuit 2 is inputted via a resistor 9 to a charge signal holding circuit 3 composed of a PNP transistor 10 and an NPN transistor 11. The NPN transistor 11 is turned on because a base current flows through the switch 4, and the PNP transistor 10 is also turned on because a base current flows therethrough. In this case, even if the recording completion signal goes to Lo level, the PNP
Since the base current continues to be supplied from the transistor 10 to the NPN transistor 11, the NPN transistor 11 maintains the ON state. While the NPN transistor 11 is ON, the base current flows through the PNP transistor 12 via the resistor 13.
The charge motor 5 continues to be in the ON state, and the charge motor 5 is energized to perform charging. When charging is completed, the switch 4 is activated and becomes the contact b side (first state), so the base current of the transistor 11 is cut off.
OFF, the PNP transistor 12 is also turned OFF, and the charge motor 5 is stopped. In addition, LED14 is NPN
While the transistor 11 is on, that is, while the charge motor 5 is in operation, the resistor 15
It lights up because current flows through it.

Next, the case when the power supply voltage drops will be explained.

If the voltage of the power supply 16 drops, it is expected that the charge motor 5 will stop while charging the shutter or mirror. At this time, switch 4 is at contact a
side (second state) and the NPN transistor 11 is in the ON state, the LED 14 continues to light up, and the release permission signal introduced from the connection point 17 to the control system 1 also remains at Lo (in other words, the state in which release cannot be performed). be. Further, in order to prevent heating of the charge motor 5, which is not sufficiently energized to carry out a charge operation, and consumption of the battery, that is, the power source 16, the PNP transistor 19 is turned ON and the PNP transistor 12 is turned OFF after a certain period of time by a timer 18. As a result, power supply to the charge motor 5 is stopped. The operation of the timer 18 is linked to a trailing magnet signal generated when a trailing magnet (not shown) is turned off, and turns on the PNP transistor 19 after a certain period of time. Turn off the power supply 16 once
Then, the electric charge in the capacitor 7 that was charged when the power supply 16 was turned on is discharged through the resistors 6 and 8 as a discharge circuit. Here, if the battery whose voltage has decreased is replaced with a new one, or if the power supply 16 is turned on again after waiting for the voltage of the battery to recover, the resistor 9 side of the capacitor 7 which is not fully charged due to the discharge will be The potential is at least higher than the Lo level. This increase in potential becomes a restart signal and is input to the resistor 9, and the base current flows to the NPN transistor 11 via the resistor 9. Therefore, even if a new recording completion signal is not generated from the control system 1, the NPN transistor 11 is turned on, and the charging operation continues as in the steady state.

Furthermore, when the power is turned on, the rear curtain magnet is
Since it is OFF, the PNP transistor 19 is turned ON and the PNP transistor 12 is turned OFF after a certain period of time by a timer. Therefore, even if the charge motor 5 is stopped midway through charging again, the charge motor 5 is de-energized. If charging is completed before the PNP transistor 19 turns on, the switch 4 becomes the contact b side (first state), so the charge motor 5 stops, and the pull-up resistor 20 connects the connection point 17.
The release permission signal introduced into control system 1 from
It becomes Hi level and the next release is possible.

As described above, according to this invention, in a camera in which the charge motor is started by a recording completion signal, if operation stops midway through charging due to a drop in power supply voltage, it is possible to continue the charging operation smoothly by turning the power OFF and then turning it ON again after the power supply voltage is restored, which is very effective in practical use.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the outline of the present invention, Figure 2
The figure is a circuit diagram of an embodiment of the present invention. 2... Restart signal output circuit, 3... Charge signal holding circuit, 4... Switch, 5... Charge motor, 6, 8... Resistor (discharge circuit), 7... Capacitor.

Claims (1)

[Claims for Utility Model Registration] A control system that outputs a recording completion signal when recording on a recording medium is completed, and after the control system outputs the recording completion signal,
a restart signal output circuit that outputs a restart signal when the power is turned off and then turned on again; and a restart signal output circuit that outputs a signal for driving the charge motor based on the input of the recording completion signal or the restart signal. A charge signal holding circuit is connected to the charge signal holding circuit, and a first state, which is set when charging by the charge motor is completed, disables the charge signal holding circuit, and a first state, which is set when recording on the recording medium is completed. The restart signal output circuit is charged by the power supply after power is turned on, and discharges the charged charge when the power is turned off. A charge motor drive circuit for a camera, comprising a charging/discharging means.