JPH07104174A - Driving circuit for light emitting diode for camera - Google Patents

Abstract

PURPOSE:To commonly use the external connecting terminals of a control circuit and driving circuit with other actuators in the light emitting diode driving circuit for controlling the light emitting diode used in a camera by the integrated control circuit. CONSTITUTION:A motor 2 for opening and closing a shutter and a motor 3 for feeding a film are biclirectionally driven by transistors Q1 to Q6 controlled by the external connecting terminals P1 to P6 of the integrated control circuit 4 as the driving circuit. For example, the TR Q5 among the TRs constituting the driving circuit is built onto a current loop for supplying a driving current to the light emitting diode 5. The light emitting diode 5 is made to emit light without operating the other actuators 2, 3 if the TR Q5 is made conducting while the other TRs are held nonconducting. The driving of the light emitting diode 5 is thus controlled by commonly using the external connecting terminal P5 and the TR Q5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for a light emitting diode for a camera which generates near infrared light for distance measuring operation, and particularly to a film winding motor and a shutter opening / closing motor. The present invention relates to a drive circuit for a camera light emitting diode in which a drive circuit used for driving the camera actuator and a control output terminal for controlling the drive circuit can be used also as these camera actuators.

[0002]

2. Description of the Related Art For example, in the case of a camera equipped with an active triangulation type automatic focus adjustment mechanism, an infrared light emitting diode which emits near infrared light for distance measurement toward a subject and a drive current to the light emitting diode are provided. It is equipped with a drive circuit that supplies the light-emitting diode and the drive circuit.
Similar to various actuators such as a film winding motor and a shutter opening / closing motor, and a drive circuit thereof, a so-called external circuit is provided for the integrated control circuit.

FIG. 3 is a circuit diagram showing an example of a conventional drive circuit. Reference numeral 21 is a power supply, 22 is an IC control circuit, 23 is a light emitting diode for generating near infrared light, and 24 is an operation of the light emitting diode 23. A resistor for stabilizing the point potential, 25 is a capacitor for accumulating charges for causing the light emitting diode 3 to emit light, and 26 and 27 are motors for opening and closing a shutter and a film winding motor, which are examples of actuators. The motors 26 and 27 are supplied with a drive current by the switching operation of the transistors Q1 to Q6 which function as a drive circuit. Further, the light emitting diode 23 emits light while discharging the electric charge of the capacitor 25 by the conduction of the transistor Q7 which also functions as a drive circuit. Then, these various drive circuits are controlled by the external connection terminals P1 to P7 of the control circuit 22 which is formed as an IC.

[0004]

As is well known, I
The number of external connection terminals of C is practically limited, and an increase in the number of terminals leads to an increase in size of the IC package. on the other hand,
Although the number of objects to be controlled such as actuators and various indicators tends to increase with the recent computerization and multi-functionalization of cameras, there are great demands for downsizing the entire camera. The conventional light emitting diode drive circuit as shown in FIG. 3 requires an independent drive circuit for supplying a drive current to the light emitting diode and an external connection terminal of the control IC package 22. However, there is a problem in that the size of the entire camera is increased.

[0005]

The present invention has been made in view of the above problems, and provides a drive circuit for a light emitting diode which does not require a drive circuit dedicated to the light emitting diode or an external connection terminal on the IC package side. By providing, IC
The purpose is to reduce the size of the package and the entire camera. In summary, the driving circuit of a light emitting diode for a camera according to the present invention is used in an IC control circuit having an external connection terminal for providing a control signal to a controlled circuit element provided outside the IC package. A light emitting diode and an actuator to which a drive current is supplied by a pair of drive circuits that can be controlled independently from the control circuit at a timing different from the timing of causing the light emitting diodes to emit light. A driving current is supplied to the light emitting diode through the drive circuit in the conductive state when one drive circuit is in the non-conductive state and the other drive circuit is in the conductive state. Is.

[0006]

In general, among actuators for cameras, an actuator that is bidirectionally driven, such as a motor for opening and closing a shutter or a motor for film feeding, is so-called bipolar driven by a pair of drive circuits to form a pair. When only one drive circuit is in a conductive state, the drive current is not supplied to the target actuator. Therefore, in the present invention, one drive circuit forming a pair is placed in a non-conducting state while the other drive circuit is placed in a conducting state, and a drive current is supplied to the light emitting diode by the drive circuit in the conducting state. The light emitting diode can be driven without requiring a dedicated drive circuit or a dedicated external connection terminal of the control IC package.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 1, 1 is a power source such as a dry battery, 2 is a motor for opening and closing a shutter, 3 is a motor for winding a film, and 4 is a control circuit integrated into an IC. Also, 5
Is a light emitting diode that generates near-infrared light for distance measurement operation, 6 is a capacitor that stores electric charges for emitting light from the light emitting diode 5, 7 is a resistor that sets the operating point potential of the light emitting diode 5, 8 and 9 Are resistors that provide a virtual load when the power supply voltage is checked.

Transistors Q1 to Q6 respectively supply drive currents to the motors 2 and 3 constituting the actuator by switching operation, and form a pair of drive circuits in the crossing direction with the motors 2 and 3 serving as the actuators at the center. More specifically, when the transistors Q1 and Q4 conduct, one current is supplied to the motor 2 and the transistor Q1
When 2 · Q3 becomes conductive, the other current is supplied to the motor 2. When the transistors Q3 and Q6 are turned on, the motor 3
Is supplied with one current, and when the transistors Q4 and Q5 conduct, the other current is supplied to the motor 3.

Each of these transistors Q1 to Q6 is I
A switching operation is performed by supplying a control signal from the external connection terminals P1 to P6 of the C-shaped control circuit 4. A feature of this embodiment is that the transistor Q5 for supplying a drive current to the motor 3 and the external connection terminal P5 for the transistor Q5 are also used for drive control of the light emitting diode 5, and other transistors are non-conductive. By making only the transistor Q5 conductive in this state, the light emitting diode 5 can be operated without affecting the motors 2 and 3 which are actuators.

Next, P0 is an external connection terminal to which the level of the power supply 1 is applied at the time of checking the power supply voltage, which is added to the positive phase input of the comparator 10 in the control circuit 4 and to the negative phase input of the comparator 11. The reference power source 11 is connected.

Next, the operation of the above embodiment will be described with reference to the above matters and the time chart shown in FIG. The time chart shows H and L of the control signals led to the corresponding external connection terminals P1 to P6. The odd-numbered transistors Q1, Q3, Q5 become conductive when the corresponding external connection terminals P1, P3, P5 are at L level, and the even-numbered transistors Q2, Q4, Q6 have corresponding external connection terminals P2, P4, P6. Conducts when is at H level. First, the time region A of the time chart shown in FIG. 2 shows the initial state of the device, and all the transistors Q1 to Q6 are off. Therefore, the motors 2, 3 and the light emitting diode 5
No drive current is supplied to the capacitor 6, and the capacitor 6 is charged to the level of the power supply 1.

Next, the time region B of the time chart is the timing for performing the voltage inspection of the power supply 1, and the external connection terminal P
1 becomes L level, the external connection terminal P2 becomes H level, and the transistors Q1 and Q2 become conductive. Also, at this timing, the other transistors Q3 to Q6 are non-conductive. Therefore, in the time region B of the time chart, a current flows through the transistor Q1-resistor 8-resistor 9-transistor Q2. In this embodiment, the combined load generated by the resistors 8 and 9 is the same as the transistor Q1-resistor 8-motor 2 for the motor 2 for opening and closing the shutter.
-Load when energized via transistor Q4, and
Transistor Q3-Motor 2-Resistor 9-Transistor Q
Resistor 8, so that it becomes equal to the load when energized via 2.
The resistance value of 9 is preset. When the resistors 8 and 9 are added as a load, a voltage drop occurs in the power source 1,
The level of the external connection terminal P0 is lowered. The level of the external connection terminal P0 is applied to the comparator 10, and the comparator 10 is applied to the negative phase input
When the level of the external connection terminal P0 becomes lower than the level of 1, the output of itself is set to the L level to issue a voltage drop warning and the like.
That is, in this embodiment, the power supply voltage is inspected under the condition that a load equivalent to that under the actual load is applied.

Next, the time region C of the time chart has the same logic state as the initial state, and the capacitor 6 is charged. Subsequently, the time region D of the time chart is the timing for causing the light emitting diode 5 to emit light, and the L pulse is generated at the external connection terminal P5, so that the transistor Q5 becomes conductive. Therefore, the charge accumulated in the capacitor 6 is discharged through the transistor Q5 and the light emitting diode 5, and the light emitting diode 5 emits light to perform the distance measuring operation. At this time, the other transistors Q1 to
Since Q4 and Q6 are all non-conductive, the conduction of the transistor Q5 does not affect the motors 2 and 3.

The time region E of the time chart is in the same logical state as the initial state, and during this period, the lens system (not shown) is driven to perform the focusing operation in accordance with the result of the above distance measurement. Note that the focusing operation is not directly related to the present application, and a description thereof will be omitted. In the time region F of the time chart, the shutter blade opening operation (not shown) is performed. More specifically, in the time region F of the time chart, the L level is led to the external connection terminal P1 of the control circuit 4, and the H level is led to the external connection terminal P4. Therefore, transistors Q1 and Q4
Are conducted, and the motor 2 has a transistor Q1-resistor 8-
A drive current flows through the motor 2-transistor Q4.
The load state at this time is substantially equal to the load state when current is supplied to the resistors 8 and 9 which are virtual loads. And
When the drive current flows through the motor 2 through the above path, the motor 2 is driven in the direction in which the shutter blade (not shown) is opened.

The shutter blade (not shown) is driven to close in the time region G of the subsequent time chart. More specifically, the H level is guided to the external connection terminal P2 of the control circuit 4, and the L level is guided to the external connection terminal P3. Therefore, the transistor Q
2. Q3 conducts, and the motor 2 has a transistor Q3-
A drive current flows through the motor 2-resistor 9-transistor Q2. The load state at this time is substantially equal to the load state when the drive current is supplied to the resistors 8 and 9 which are virtual loads. Then, when a drive current flows through the motor 2 through the above path, the motor 2 is driven in a direction to close the shutter blade (not shown). At this time, the L level is introduced to the external connection terminal P5 of the control circuit 4 and the transistor Q5 is also turned on. However, if the transistor Q3 is simply turned on, the transistor Q3-motor 3-light emitting diode 5-
Since a current flows through the resistor 7 and the film feeding motor 3 rotates, the potential difference across the film feeding motor 3 is reduced to 0 by turning on the transistor Q5.
This is to prevent the rotation of the motor 3.

In the time region H of the subsequent time chart, the film is advanced by one frame. More specifically, the L level is guided to the external connection terminal P3 of the control circuit 4, and the H level is guided to the external connection terminal P6. Therefore, the transistor Q
3. Q6 conducts, and motor 3 has transistor Q3-
A drive current flows through the motor 3-transistor Q6, and the motor 3 operates a film feeding mechanism (not shown) to feed one frame of film.

In the time region I of the following time chart, braking is applied to the film feeding mechanism (not shown). That is, the H level is introduced to both the external connection terminals P4 and P6 of the control circuit 4, and the transistors Q4 and Q6 become conductive. Further, the H level is introduced to the external connection terminals P3 and P5 of the control circuit 4, and the transistors Q3 and Q5 are both cut off. Therefore, the transistor Q is connected to both ends of the film feed motor 3.
A short-circuit is applied to the motor 3 via so-called "short brake" via 4.Q6, and the motor 3 applies a braking force to a film feed mechanism (not shown). Then, in the time region J of the time chart, the same logical state as the initial state is set, and the shooting operation for one frame is completed.

In the above description, an example in which a near infrared light emitting diode for active triangulation is used as a light emitting diode for a camera is shown. However, as the light emitting diode other than this, for example, a light emitting diode for various indicators is used. It goes without saying that the present invention can also be applied to this. In the above, as an example of the actuator, the example in which the light emitting diode also serves as the drive circuit of the motor 3 for film feeding and the external connection terminal for control is shown, but the operation timing is different from that of the light emitting diode, and As long as the actuator is bi-directionally driven by a pair of drive circuits, the actuator for opening and closing the shutter, which is the other example of the above embodiment, or a zoom lens (not shown) for zooming, for example, is used as the actuator. It goes without saying that the present invention can be applied to other actuators such as a motor and a focusing motor.

[0019]

As described above, according to the present invention, an actuator driven by a pair of drive circuits and a light emitting diode can share an external connection terminal of a drive circuit or a control IC package. Since it is not necessary to provide a dedicated drive circuit or a control external connection terminal for the light emitting diode, it is possible to contribute to the miniaturization of the IC package and the miniaturization of the entire camera.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a time chart of the circuit shown in FIG.

FIG. 3 is a circuit diagram showing a conventional circuit example.

[Explanation of symbols]

1 power supply 2 motor 3 motor 4 control circuit P0, P1, P2, P3, P4, P5, P6 external connection terminal 5 light emitting diode 6 capacitor Q1, Q2, Q3, Q4, Q5, Q6 transistor

Claims (1)

[Claims] 1. An IC having an external connection terminal for applying a control signal to a control target circuit element provided outside the IC package.
An actuator to which a drive current is supplied by a pair of a control circuit, a light-emitting diode used in a camera, and a drive circuit that can be controlled independently from the control circuit at a timing different from the timing at which the light-emitting diode emits light. When one of the drive circuits forming the pair of drive circuits is made non-conductive and the other drive circuit is made conductive, a drive current is supplied to the light emitting diode via the drive circuit in the conductive state. A driving circuit for a light emitting diode for a camera, which is characterized by being supplied.