JPS5838773B2 - Dengenchietsuka - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power source battery checker for cameras, etc., and particularly to a power source checker that can accurately check the usage limit of a built-in battery.

Conventional power supply checkers of this type check the power supply voltage by blinking a display element such as a lamp using a circuit specially provided for supplying a reference voltage for the power supply checker.

However, in this method, the reference voltage for the photometric circuit and the reference voltage for the checker are obtained from separate voltage circuits, which not only complicates the circuit configuration and is inconvenient for devices with limited space such as cameras, but also In order to resolve the effects of temperature on each circuit, a temperature compensation element is required in each circuit, and variations in each element, including variations in the characteristics of the temperature compensation element, result in variations in each voltage circuit. Adjustment means had to be provided for correction, which complicated the assembly process.

Furthermore, even if the variation is adjusted by the adjustment means, the variation in the voltage circuits due to temperature changes cannot be prevented because the characteristics of the changes in each voltage circuit with respect to temperature changes are different.

Therefore, when considering the operation of a checker that takes into account variations in temperature, it is necessary to assume the case where the variation between the reference voltage of the photometric circuit and the reference voltage for the checker is the greatest. The checker issues a warning even when the power supply voltage is available, forcing the user to replace the battery, thereby wasting the battery.

In particular, when using mercury batteries, the voltage drop due to consumption is very slow, so the battery can be used for a very long time after the checker issues a warning (until it becomes unusable). Considering this, it would be extremely uneconomical to waste this.

In view of the above-mentioned circumstances, the present invention is configured so that the reference voltage for the photometric circuit and the reference voltage for the checker are obtained from the same constant voltage circuit, unlike the conventional method in which separate reference voltage circuits are provided for the photometric circuit and the checker. This aims to eliminate the complication of structure and adjustment caused by the use of batteries, and to prevent the checker from issuing a warning while the batteries are still usable, thereby allowing the batteries to be utilized to the maximum extent possible.

A power checker circuit according to the present invention will be explained.

FIG. 1 is a circuit diagram showing an embodiment of the power checker according to the present invention. B is a power supply, So is a power switch, S2 is a release switch, FO is a film drive circuit, FV is a constant voltage IC, and CdS is a light source for subject light. A photoconductive element that receives light, V
Rl is a variable resistor for inputting information such as film sensitivity, M
e is an EE meter that controls the aperture in conjunction with an aperture control mechanism (not shown), and the photoconductive element CdS and the variable resistor VR,
Together with this, a photometric circuit (2) is formed.

R7 and R2 are resistors, D is a light emitting diode, and Trl is a switching transistor, which is turned on when the checker switch S1 is pressed when the power source has sufficient voltage to drive the camera.

R3 is a resistance that simulates the resistance of a motor (not shown) that drives the camera, and is used to perform an accurate battery check.

Next, the operation of one embodiment of the power checker shown in FIG. 1 according to the present invention will be described.

If power supply B has a voltage above the operating limit, switch power switch S.

When the checker switch S1 is pressed and turned on, the output voltage of the constant voltage IC is applied to the base potential of the transistor Trl, the transistor Tr is turned on, a current flows to the light emitting diode D1 via the resistor R2, it emits light, and the power source is turned on. is above the usage limit.

If the voltage limit B is below the operating limit, the transistor Tr1 will not turn off even if the checker switch S1 is pressed.
The base potential of the transistor Tr1 is low, and the light emitting diode D, which can conduct the transistor Tr1, does not emit light and informs the photographer that the power supply is below the usable limit.

As mentioned above (in the power supply checker of the present invention, the output of the constant voltage IC that is the power supply for the photometry circuit is directly used as the reference voltage of the power supply checker, so that accurate power supply checks can be performed and it is also possible to check the power supply even during shooting. Become.

FIG. 2 shows another embodiment of the power supply checker according to the present invention, and circuit components that are essentially the same in configuration and operation as those in the embodiment shown in FIG. The difference is that an EE meter Me is used instead of a light emitting diode as an element.

Next, the operation of the embodiment shown in FIG. 2 will be explained. If power supply B has a voltage above the operating limit, switch power switch S.

When the checker switch S1 is pressed and turned on, the selector switch S3 is switched from the movement N side to the BC side in conjunction with the checker switch S1, and the EE meter Me is connected to the collector side of the transistor Tr, and the low voltage IC Since the output of is applied to the base of the transistor Tr, it turns on and the pointer of the EE meter swings, indicating that the power supply is above the usable limit.

If the voltage of power supply B is below the operating limit, the transistor Tr will not turn off even if checker switch S1 is pressed.
, does not turn on, and the EE meter pointer does not move, informing the photographer that the power is below the operating limit.

FIG. 3 is a circuit diagram showing another embodiment of the power supply checker according to the present invention, and the same symbols are given to circuit components whose configuration and operation are essentially the same as those of the embodiment shown in FIG. 2. However, by connecting a diode D2 to the base side of the transistor Tr1 and further providing a resistor R5, the transistor Tr1
The voltage VBE between the base and emitter of diode D2
By using the forward bias voltage characteristic Vf, they cancel each other out, thereby greatly reducing errors due to temperature.

The operation of the embodiment shown in FIG. 3 is the same as that of the embodiment shown in FIG. 1, so a description thereof will be omitted.

FIG. 4 is a circuit diagram showing another embodiment of the power supply checker according to the present invention, and the difference from the embodiment in FIG. 1 is the transistor T.
The difference is that a variable resistor vR3 is connected between the base and collector of r, so that the reference voltage of the power warning circuit can be adjusted.

The operation of the embodiment of FIG. 4 is the same as that of the embodiment of FIG. 1, so a description thereof will be omitted.

In the above-described embodiment, the switching transistor is turned on and the light emitting diode or lamp is turned on when the power supply voltage is above the limit voltage. It may be possible to turn on the light.

As mentioned above, in the power supply checker according to the present invention, the output voltage of the common constant voltage circuit is used as the reference voltage for the photometry circuit and the power supply checker, so the circuit configuration is simplified, and the photometry circuit and the power supply checker are separated from each other. Since there is no need to adjust variations between the respective voltage circuits that occur when two reference voltage circuits are provided, the assembly process is greatly simplified.

Furthermore, if separate reference voltage circuits were provided for each, it would be necessary to set the checker with a certain margin in consideration of variations caused by temperature changes, resulting in wasted battery power. Since a reference voltage circuit is used, this problem does not occur, and the power supply voltage is accurately checked, so the battery can be used to the maximum extent, making it very economical.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of a power supply checker according to the present invention, FIG. 2 is a circuit diagram showing another embodiment of the present invention, and FIG. 3 is a circuit diagram showing another embodiment of the present invention. , FIG. 4 is a circuit diagram illustrating an exemplary embodiment of the present invention. B...Power supply, FV...Constant voltage IC1■
...Photometering circuit, R1-R3...Resistance,
Trl...Transistor, Dl...
・Light-emitting diode, Sl...Checker switch.

Claims (1)

[Claims] 1. A power supply battery, a constant voltage circuit that receives the output of the power supply battery as input, a photometry circuit that operates based on the output of the constant voltage circuit, and an output of the power supply battery and the output of the constant voltage circuit that operates the photometry circuit. a comparison circuit that changes the output state when the potential difference falls below a predetermined value; a display means that displays the output state of the comparison circuit; and when the power supply battery reaches the operating limit voltage of the photometry circuit, A camera comprising an adjustment circuit that adjusts the output of the power supply battery or the output of the constant voltage circuit so that the potential difference between the output of the power supply battery and the output of the constant voltage circuit becomes the predetermined value. power checker.