JP2003241265A - camera - Google Patents

Abstract

(57) [Problem] To shorten an imaging sequence while preventing both a reduction in power supply voltage below a predetermined value and a reduction in autofocus accuracy. SOLUTION: A separately excited flyback type charging circuit, and a signal generation for supplying a pulse control signal to a primary side of a transformer which is a component of the charging circuit to generate a pulse signal for exciting the transformer And a power supply unit for supplying power to a drive unit other than the charge control unit and the charge control unit, wherein the signal generation unit includes, as a load on the power supply unit, The power supply voltage of the power supply unit is not limited to the charging control unit, but also in a state in which the driving means other than the lens driving for automatic focusing (lens AF driving load) is applied as a load (MPU load, feeding driving load). The pulse signal is generated and charge control is performed so that the load (l- (n + m), l-m) of the charge control unit does not decrease below a predetermined value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a camera having a charge control unit having a separately-excited flyback charging circuit capable of controlling an input current.

[0002]

2. Description of the Related Art Conventionally, strobe charging, lens AF drive (meaning distance measurement (focus detection) operation and lens drive for autofocus based on the result), AE drive,
In a series of camera shooting sequences such as shutter drive and feeding drive, strobe charging takes a very long time. Strobe continuous shooting, FEB (Flash Exposure Bracketin
g) Reducing this charging time during continuous shooting using a strobe device such as shooting (meaning shooting with one frame by changing the light control level every 1/3 step) It is desired to plan. However, strobe charging requires a large amount of load current at one time, so it was difficult to drive it simultaneously with other modules.

On the other hand, in Japanese Patent Application Laid-Open No. 11-87082, when a separately-excited flyback charging circuit whose current control is relatively easy is used and a load other than strobe charging is applied to a power supply common to the system. Also in the above, a system is constructed in which the pulse width of the charge control is narrowed or the pulse cycle is extended to reduce the load current of the strobe charge and the strobe charge can be performed simultaneously with other modules.

[0004]

However, in the above-mentioned Japanese Patent Application Laid-Open No. 11-87082, charging control is switched only by detecting whether or not power supply to a specific load other than strobe charging is performed, and in fact, This is different from shortening the shooting sequence (including flash charging) during continuous shooting in. In other words, just by performing the charging in parallel with the modules other than the strobe charging always functioning does not mean that the ideal shooting sequence is shortened. For example, there is a feeding sequence in which the film is wound after the stroboscopic light is emitted. However, performing strobe charging in parallel with this leads to shortening and does not electrically hinder the feeding sequence. However, if charging is attempted in parallel while the lens AF drive is being performed immediately after the feeding sequence, the sequence will be shortened, but it will be automatic from the aspect of electrical noise caused by the oscillating operation of the step-up transformer. This is not preferable because it may affect the focusing accuracy. In that case, it would be more ideal to shorten the shooting sequence by setting the common power supply to a no-load state other than strobe charging, ending the charging sequence in that no-load state, and then performing the lens AF drive. Be done.

(Object of the Invention) An object of the present invention is to shorten the photographing sequence while preventing both the power supply voltage from dropping below a predetermined value and the autofocus accuracy from falling. The aim is to provide a camera that can do this.

[0006]

In order to achieve the above object, the present invention provides a separately-excited flyback type charging circuit for charging a main capacitor that stores electric charges for causing a discharge tube to emit light. A charging control unit having a signal generation unit for supplying a pulse control signal to a primary side of a transformer which is a constituent element of the charging circuit to generate a pulse signal for exciting the transformer; In a camera having a power supply unit that supplies power to a driving unit other than a charging control unit, the signal generation unit may drive not only the charging control unit but also a lens drive for autofocus as a load to the power supply unit. Even when the driving means other than the above is applied as a load, the power supply voltage of the power supply unit is set to a load of the charging control unit so as not to drop below a predetermined value. It generates a scan signal, and a camera for charging control.

More specifically, the allowable load for the charging control unit is calculated from the open circuit voltage of the power supply unit and the load of the driving means (there may be a plurality) other than the charging control unit, which is assumed in advance. Then, a pulse signal having a pulse width and a pulse cycle is generated, and the flyback type charging circuit in the charging control unit is operated by the pulse signal to perform charging control.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail based on the illustrated embodiments.

FIG. 1 is a block diagram showing an electrical configuration of a silver salt single lens reflex camera according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a common power source for the camera, which is DC / DC for each of a lens AF driving circuit 3, a feeding driving circuit 4, a shutter driving circuit 5, an MPU 6, and a strobe charging circuit 7, which will be described later. Power is supplied directly without going through a converter or the like. Reference numeral 3 denotes a lens AF drive circuit for autofocusing the lens, which controls a motor for driving the focus lens. Four
Is a feeding drive circuit that winds the film, and is a circuit that drives the shutter after driving it. Reference numeral 5 denotes a shutter drive circuit, which is a shutter drive circuit for controlling the shutter magnet. Reference numeral 6 denotes an MPU, which is a microcomputer that controls the entire camera, and controls the lens AF drive circuit 3, the feed drive circuit 4, the shutter drive circuit 5, and the strobe charging circuit 7 here. .

Reference numeral 2 denotes a charging control section, which is a section for supplying a pulse signal from the MPU 6 to the strobe charging circuit 7 to control the strobe charging. 8 is a strobe charging circuit 7
This is a strobe light emission circuit that converts the charge energy charged in to light energy by a discharge tube and emits strobe light.

Next, the detailed circuit configuration in the charging control unit 2 will be described with reference to FIG.

The strobe charging circuit 7 is a separately-excited flyback charging circuit. A switch 25 permits power supply to the strobe charging circuit 7, and a charge EN signal 26 sent from the MPU 6 controls whether charging is permitted or not. Charge control signal 28 is MPU6
A signal generated by (a signal generation unit that generates a pulse signal). By supplying the signal to the oscillation transistor 11, the oscillation transistor 11 controls the current on the primary side of the transformer 10. In this way, by pulse-driving the current on the primary side of the transformer 10, a flyback voltage (back electromotive force) is excited on the secondary side. Further, the flyback voltage energy generated on the secondary side is rectified by the rectifier diodes 13, 1
8, the main capacitor 24 is charged through the charging backflow prevention diode 23.

Reference numeral 27 is a monitoring signal for monitoring the supply state of the flyback voltage generated on the secondary side to the main capacitor 24. The flyback voltage is generated and the main capacitor 2
When the current supply to 4 is started, the diode 14 outputs Low, and when the current supply to the main capacitor 24 is completed, the current is pulled up to the power supply 17 via the pull-up resistor 16. Reference numeral 15 is a capacitor for alleviating ripples, overshoots and the like of the monitor signal 27. Further, 29 is a charging voltage monitor signal, and the value obtained by dividing the charging voltage by the resistors 19 and 20 is A of the MPU6.
/ D port. Further, 21 and 22 are capacitors for alleviating noise of the divided voltage of the charging voltage.
Reference numeral 8 denotes a strobe light emitting circuit which changes the charge energy accumulated in the main capacitor 24 into light energy and emits light. Reference numeral 30 is a light emission control signal for controlling the start and stop of light emission of the flash light emission circuit 8.

Next, a simple operation principle of the separately-excited flyback charging circuit shown in FIG. 2 will be described.

When the oscillation transistor 11 is turned on for a predetermined time with the switch 25 connected, a current flows through the primary side of the transformer 10 and the transformer 10 is excited. After that, by turning off the oscillation transistor 11, the flyback voltage (back electromotive force) is applied to the secondary side of the transformer 10.
Occurs, and in the OFF period of the oscillation transistor 11,
The electric energy generated by the flyback voltage is accumulated in the main capacitor 24 via the diodes 18 and 23. The larger the instantaneous current flowing to the primary side (the longer the ON time (the larger the pulse width)) and the shorter the pulse cycle, the larger the average energy supplied from the secondary side to the main capacitor 24. , Charging speed becomes faster. On the other hand, the average load current also increases.

Next, the charge control according to the load condition will be described with reference to FIGS. 3 and 4.

FIG. 3 shows the charging control according to the conventional system, in which the modules other than the strobe and the strobe charging circuit are sequentially driven so that the loads on the common power source are not overlapped. Further, as described in the circuit of FIG. 2, the charging circuit in the flyback system has a characteristic that the average load current is determined by the ON time (pulse width) and the pulse period for the oscillation transistor 11. The charging control signal 28 at this time determines the pulse width and pulse period of the charging control signal so that the average load current takes into consideration the voltage drop due to only strobe charging, and the charging control is performed.

In FIG. 4, charging is performed in a state in which a module other than the strobe is functioning (first charging section) and charging is performed in a state in which a module other than the strobe is stopped (second charging). This is a description of the charge control signal 28 in the (section).

In the case where charging is performed in a state where a module other than the strobe is functioning (charging first section), the allowable load on the strobe is small and the average load current of the strobe is set accordingly. In this case, the pulse width is reduced to control the oscillation transistor 11 to reduce the average load current of the strobe. On the other hand, in the state where the modules other than the strobe are stopped (second charging section), the oscillation transistor 11 is controlled with the pulse width extended more than the above pulse width, and the average load current of the strobe becomes higher than that in the above state. The control is as follows.

In FIGS. 5, 6 and 7, the lens A
The timings of F drive, feed drive, shutter drive, MPU operation and strobe charge operation, the total allowable load other than strobe charge on the common power supply in each state, and the load limit thereof are shown. Further, the load limit depends on the open circuit voltage of the common power supply, and here, the load limit (total allowable load) for a certain open circuit voltage is indicated by l.

FIG. 5 shows a conventional method, in which the lens AF drive, shutter drive, feed drive, and strobe charge are performed in series (time series) during the photographing sequence. Therefore, during strobe charge. With respect to the total allowable load 1, a load of lm, which is a load other than the MPU load m, is allowed, and the charging sequence is performed in the shortest time (d). However, since it is performed in series (time series) with other modules, as a result, the imaging sequence indicated by a becomes long (a).

On the other hand, FIG. 6 shows a first example of the present embodiment, in which FIG. 6 shows an example in which the strobe charging operation is performed during the feeding drive, and during the feeding operation. This is the case when charging is completed. That is, this is a state in which the amount of strobe light emission in the shooting sequence is relatively small.
In this case, since the charging sequence overlaps the feeding sequence, the MPU load m,
A load of "l- (m + n)" that is a load other than the feeding drive load n is allowed for charging, and the charging control is performed within this allowable range.

Therefore, as the charging sequence, charging is performed for the length e, but since the processing is performed in parallel with the feeding drive, the shooting sequence is b (<a), which is different from the conventional method of FIG. Also, the shooting sequence can be shortened.

Further, FIG. 7 shows a second example of the present embodiment, and in FIG. 7, even when the flash emission amount in the photographing sequence is relatively large,
In this example, charging is performed in parallel only during the feeding drive, and strobe charging operation is not performed in parallel during the lens AF drive. In other words, if the strobe charge becomes long, the charging operation will not end during the feeding sequence and will be performed in parallel with the lens AF driving sequence unless some measures are taken. In consideration of this (due to electrical noise), the charging control is performed in parallel only during the feeding drive in the second embodiment.

Specifically, during the feeding, a load of "l- (m + n)" which is a load other than the MPU load m and the feeding drive load n is allowed for charging, and the charging control is performed within this allowable range. ,
For the remaining charge energy, a load of "lm" that is a load other than the MPU load m is allowed for charging, and the charge control is performed within this allowable range.

Therefore, the charging sequence is f (>
d) is relatively long, but the shooting sequence is c (<
As a result, the photographing sequence can be shortened as compared with the conventional method shown in FIG.

According to the above-described embodiment, power is supplied to a plurality of modules (lens AF drive circuit, feed drive circuit, shutter drive circuit) including a strobe charge control unit without a converter such as a DC / DC converter. In a camera having a common power supply (power supply circuit 1) for supplying power, a state in which a load other than the strobe charge control unit is applied to the power supply (state in which strobe charging and other driving means are performed in parallel) Also), the pulse width and pulse period of the charging control signal 28, which is a pulse signal, are set so that the power supply voltage does not drop below a predetermined value (a strobe charging load that does not exceed the load limit). 4) is determined and the strobe charging control is performed, so that the photographing sequence can be shortened without lowering the power supply voltage to a predetermined value or less. It is possible.

Further, since the lens AF drive is excluded from the other driving means that are performed in parallel with the strobe charging, the electrical noise caused by the oscillating operation for boosting does not adversely affect the autofocus control. It is possible to perform accurate autofocus drive while shortening the shooting sequence.

[0030]

As described above, according to the present invention,
While preventing both the power supply voltage from dropping below a specified value and the autofocus accuracy from decreasing,
It is possible to provide a camera that can shorten the shooting sequence.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a main part of a camera according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing details of a charge control unit in FIG.

FIG. 3 is a timing chart including a charge control signal in the conventional method.

FIG. 4 is a timing chart including a charge control signal in the embodiment of the present invention.

FIG. 5 is a load sequence of a camera in the conventional method.

FIG. 6 is a load sequence showing a first example when the amount of charge is small in the embodiment of the present invention.

FIG. 7 is a load sequence showing a second example in the case where the charged charge amount is large in the embodiment of the present invention.

[Explanation of symbols]

1 Power Supply Circuit (Power Supply Unit) 2 Charging Control Unit 3 Lens AF Drive Circuit 4 Feed Drive Circuit (Feed Drive Means) 5 Shutter Drive Circuit (Shutter Drive Means) 6 MPU (Signal Generation Means) 7 Strobe Charge Circuit (External Excitation) Type flyback charging circuit) 28 charging control signal (pulse signal)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 5/232 H04N 5/232 A 5/238 5/238 Z H05B 41/32 H05B 41/32 M

Claims (4)

[Claims] 1. A separately-excited flyback charging circuit for charging a main capacitor that stores electric charges for causing a discharge tube to emit light, and pulse control for a primary side of a transformer which is a constituent element of the charging circuit. A charging control unit including a signal generation unit that supplies a signal to generate a pulse signal for exciting the transformer, and a power supply unit that supplies power to the charging control unit and a driving unit other than the charging control unit. In the camera having and, the signal generation means, as a load to the power supply unit,
Not only the charging control unit, but also the load of the charging control unit such that the power supply voltage of the power supply unit does not drop below a predetermined value even when the driving unit other than the lens driving for autofocus is being applied as a load. The camera is characterized by generating the pulse signal so as to control the charging. 2. The signal generating means calculates an allowable load for the charging control section from the load of the driving means other than the charging control section, which is assumed in advance as the open circuit voltage of the power supply section, and calculates the allowable load within the allowable load. The camera according to claim 1, wherein the pulse signal having a pulse width and a pulse period that satisfies the above is generated. 3. The transformer generates a flyback voltage on the secondary side when the pulse signal generated by the signal generating means is supplied to the primary side, and the main capacitor is charged by the flyback voltage. The camera according to claim 1, wherein the camera is used. 4. The drive means is at least one of a feed drive means for feeding a film and a shutter drive means for driving a shutter. The camera described in Crab.