JP2517455Y2 - Battery drain detection circuit for camera - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a battery drain detection circuit for a camera, and in particular, A / D conversion in which the presence / absence of a battery in the main battery housing is effectively operated by a backup battery. The present invention relates to a battery drop detection circuit for a camera, which is detected by an analog voltage of the circuit.

[Problems to be Solved by Conventional Techniques and Inventions] Conventionally, when a battery in a main battery housing of a camera is accidentally removed, a battery mounted in the main battery housing charges a backup battery to various load circuits. Since power is supplied to the backup battery, the backup battery may be discharged and the program logic under execution of the CPU connected to the backup battery may be impaired, resulting in abnormal data such as the number of films stored in RAM. The interrupted metering / distance measurement data becomes abnormal, and the camera does not operate normally even if the battery is installed in the main battery housing.

[Object of the Invention] The present invention has been made in view of the above-mentioned drawbacks. Power is supplied from the constant voltage circuit when the main battery is turned on, and power is supplied from the backup battery when the main battery is not turned on. Even if the battery is removed by providing a CPU that is supplied with power and an A / D conversion circuit that organizes the data of the program executed by the CPU using the voltage generated from the backup battery as the power supply even if the battery is removed It is an object of the present invention to provide a battery drain detection circuit for a camera, which can expect normal operation immediately when a battery is attached without impairing the program logic.

[Means for Solving the Problems] In order to achieve the above object, the battery drain detection circuit for a camera according to the present invention comprises a constant voltage circuit for stabilizing the voltage of a main battery that directly supplies power to a camera load, and A backup battery charged by a stabilized power supply output from a constant voltage circuit, and power is supplied from the constant voltage circuit when the main battery is turned on, and the backup battery when the main battery is not turned on. CPU, which is supplied with power from the backup battery, and the voltage generated from the backup battery as the power source,
A / D conversion circuit that organizes the data of the program executed by the CPU in a digital amount, a variable resistor that changes the analog voltage of the A / D conversion circuit, and the voltage of the main battery is applied to one end and the other end Is a voltage dividing resistor connected to the variable resistor.

[Embodiment] An embodiment of a battery drain detection circuit for a camera according to the present invention will be described in detail below with reference to the drawings.

In the figure, 1 is a main battery housing. When the batteries BUT ₁ and BUT ₂ were mounted between the springs 1a and 1b to which the (+) terminal T _{1 of the} main battery housing 1 and the ground terminal T ₂ were connected, the main battery (+) wire W ₁ was connected. Power is supplied to the (+) terminal 2a of the charging constant voltage circuit 2, the (+) terminal 6a of the general-purpose constant voltage circuit 6, and the (+) terminal 11a of the drive circuit 11.

The constant voltage circuit 2 for charging is composed of a PNP transistor 3 and a reference voltage circuit 4, the emitter of the PNP transistor 3 is a (+) terminal 2a to which the main battery (+) line W ₁ is connected, and the collector is a constant voltage terminal 2c. Then, the base is connected via the reference voltage circuit 4 to the ground terminal 2b whose one end is connected to the reference potential point.

The main battery (+) wire W is connected to the (+) terminal 11a of the drive circuit 11.
₁ is connected and the ground terminal 11b is connected to the reference potential point.
Further, the drive circuit 11 is controlled by the CPU 20 to drive the lens 12a of the lens barrel 12, the shutter 13 and the film winding circuit 14 via the shutter terminal 11d, the AF terminal 11c and the film winding terminal 11e.

The analog voltage generation circuit 10 has a voltage divider resistor R ₁ connected in series.
(+) Terminal 10a connected to one end of the voltage dividing resistor R ₁ and the constant voltage terminal 6c of the general-purpose constant voltage circuit 9
Is connected by a general-purpose (+) wire W ₃ , one end of the variable resistor VR is connected, and the ground terminal 10b is connected to the reference potential point. Also,
The photometric circuit 19 provided with the light receiving element 19a and the capacitor 19b sends out the photometric data corresponding to the incident light to the terminal 20g of the CPU 20.

The CPU 20 is composed of the A / D conversion circuit 16 and the ROM 17, and the γ value correction table M provided in the ROM 17 by the digital output of the A / D conversion circuit 16
Search for Mn (n is 1, 2, ...). When the digital output is "0", the battery drop warning light emitting diode 18 blinks via the driver 16a and the alarm terminal 20f.

A release button 15 is connected to the release terminals 20d and 20e.

[Advantage of the Invention] The main battery housing 1 with the battery removal detection circuit for the camera having the above configuration
When the batteries BUT ₁ and BUT ₂ are attached to the springs 1a and 1b, the (+) terminal 2a of the constant voltage circuit 2 for charging, the emitter and collector of the PNP transistor 3, the constant voltage terminal 2c, the (+) wire for charging W _The backup battery 5 is charged through the route ₂ . CPU20 + V _DD
Terminal 20a is charged voltage equal to the voltage of the (+) terminal 5a and charging (+) line W ₂ in the backup battery 5 because it is connected (+) terminal 5a of the backup battery 5 is applied.

The analog amount of the analog input terminal 20c of the CPU 20 to which the input side of the A / D conversion circuit 16 is connected is converted to the analog voltage generation circuit 10
When the variable resistor VR of is set to a predetermined position by operating, the γ value correction table MMn provided in the ROM 17 is indexed by the program of the CPU20 with a digital amount corresponding to the analog amount, and the indexed γ value correction duffel MMn is corrected. By the value CPU20 drive circuit 11
Control. The drive circuit 11 is controlled by the CPU 20 and is supplied via the (+) terminal 11a to which the main battery (+) line W ₁ is connected. The batteries BUT ₁ and BUT ₂ are powered by the lens 12a of the lens barrel 12, the shutter 13, The film winding circuit 14 is driven.

When the batteries BUT ₁ and BUT ₂ are pulled out from between the springs 1a and 1b of the main battery housing 1, the (+) terminal 2a of the constant voltage circuit 2 for charging is
Is not powered by batteries BUT ₁ and BUT ₂ . However, if the backup battery 5 is charged, the program of the CPU 20 is normally executed, the data such as the RAM is destroyed, and the abnormality such as the program logic is not caused.
In addition, the PNP transistor 3 provided in the constant voltage circuit 2 for charging
Indicates the charging voltage of the backup battery 5 as the main battery (+) line W ₁
The main battery (+) line has the role of not being discharged to the
Discharge due to sneak in by various circuits connected to W ₁ is prevented.

When power has been supplied to the (+) terminal 6a of the universal constant voltage circuit 6 via the main power supply (+) line W ₁ is interrupted, the analog voltage generation universal (+) line W ₃ is connected Circuit 10
The voltage at the (+) terminal 10a becomes 0 potential. Therefore, the voltage of the analog terminal 10c becomes 0 potential, but the A / D conversion circuit 16
Is + VDD of CPU20 from backup battery 5 via W2
Since the voltage applied to the terminal 20a operates effectively as a power source, the CPU 20 determines that the battery is dead according to the A / D conversion result corresponding to 0 potential, and the battery dead alarm light-emitting diode 18 from the alarm terminal 20f via the driver 16a. Blinking.

When the batteries BUT ₁ and BUT ₂ are mounted between the springs 1a and 1b of the main battery housing 1, the digital amount of the A / D conversion circuit 16 which is operating effectively returns to the normal state. At this time, the program logic of the CPU 20 is normal, so the battery drop warning light emitting diode
The blinking of 18 is stopped, the interrupted γ value correction table MMn is indexed, and the CPU 20 can control the driver circuit 11 without a logical contradiction.

The A / D conversion circuit 16 in the above embodiment is not limited to the one incorporated in the CPU 20. When the A / D conversion circuit 16 is provided outside the CPU 20, the reference voltage is generated by the voltage dividing resistor connected to the backup battery 5.

[Effects of the Invention] The battery drain detection circuit for a camera according to the present invention includes a constant voltage circuit that stabilizes the voltage of the main battery that directly supplies power to the camera load, and a stabilized power supply output from the constant voltage circuit. A backup battery to be charged, and a CPU that is supplied with power from the constant voltage circuit when the main battery is turned on and that is supplied with power from the backup battery when the main battery is not turned on, With the voltage generated from the backup battery as a power source, an A / D conversion circuit that organizes the data of the program executed by the CPU in a digital amount,
Since the variable resistor for changing the analog voltage of the A / D conversion circuit and the voltage dividing resistor having the voltage of the main battery applied to one end and the other end connected to the variable resistor, the battery is Even if the battery is removed, the program logic of the CPU is not damaged, and normal operation is immediately performed when the battery is installed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a battery drain detection circuit for a camera according to the present invention. 2 …… Charging constant voltage circuit (constant voltage circuit) 5 …… Backup battery 16 …… A / D conversion circuit 20 …… CPU

Claims (1)

(57) [Scope of utility model registration request] 1. A constant voltage circuit that stabilizes the voltage of a main battery that supplies power directly to a camera load; a backup battery that is charged by a stabilized power supply output from the constant voltage circuit; and the main battery. Is supplied with power from the constant voltage circuit when the main battery is not supplied, and the CPU is supplied with power from the backup battery when the main battery is not supplied, and the voltage generated from the backup battery is supplied as power. An A / D conversion circuit that organizes the data of the program executed by the CPU in a digital amount, a variable resistor that changes the analog voltage of the A / D conversion circuit, and the voltage of the main battery is applied to one end And a voltage dividing resistor having an end connected to the variable resistor.