JPH0527845B2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a power supply circuit for a camera with a built-in strobe, and particularly to a power supply circuit that prevents the battery from being completely exhausted when using a strobe. be.

(Prior Art) In recent years, not only strobes but also cameras with built-in film winding and rewinding devices using motors have become popular. Furthermore, cameras that use long-life batteries that make it difficult for the camera user to replace the batteries, or that require the camera back to be opened to replace the batteries, have also been put into practical use. There is. For cameras like this, where it is difficult for the user to replace the battery, or where the battery cannot be replaced without opening the back cover, and which has a built-in film winding/rewinding device and a strobe, there is no strobe. If the battery runs out during synchronized flash photography, you will not be able to wind or rewind the film, which is inconvenient. This is extremely inconvenient as it is necessary to take out the loaded film and replace the battery.

(Purpose) The purpose of the present invention is to prevent the battery from being completely exhausted during synchronized flash photography using a strobe.
For example, even if the camera has a film winding and rewinding device, at least the film winding and rewinding device
To provide a power supply circuit for a camera with a built-in strobe, which allows a user to take out a loaded film by leaving energy necessary for rewinding.

(Configuration) The power supply circuit of the camera with a built-in strobe according to the present invention includes a light emission enable signal output section that outputs a signal when the main capacitor is charged to a voltage that enables light emission, and a power supply circuit that outputs a signal when the main capacitor is charged to a voltage that enables light emission, and a power supply circuit that outputs a signal when the main capacitor is charged to a voltage that allows light emission, and a power supply circuit that outputs a signal when the main capacitor is charged to a voltage that enables light emission, and a power supply circuit that outputs a signal when the main capacitor is charged to a voltage that enables light emission. a strobe having a charging completion signal output section that outputs a signal when the main capacitor is charged; a first reference time setting section that sets a predetermined time from the start of charging of the main capacitor as a first reference time; A second reference time that sets a predetermined time from the time when the light emission enable signal is output from the light emission enable signal output section as a second reference time, and sets the end of the second reference time later than the end of the first reference time. It has a setting section and an arithmetic control section that turns off the power of the strobe when the light emission enable signal is not output within the first reference time or when the charging completion signal is not output within the second reference time.

The invention will now be described with reference to illustrated embodiments.

In FIG. 1, E is a power supply battery, and S1 is a main switch. When the main switch S1 is turned on, power is supplied from the battery E to the power terminal Vcc of the central processing unit 1 consisting of a microcomputer, etc. It's getting old. Power is also supplied to the strobe unit 2 from the battery E.

The circuit configuration of the strobe unit 2 is as shown in FIG. 2, for example. In FIG. 2, the power applied to the power supply terminal Vcc of the strobe unit is applied to the DC/DC converter 3 when the switching transistor TR1 is turned on, and the converter 3 starts operating. Furthermore, by turning on the transistor TR1, power is applied to the series branch of the transistor TR3 and the resistor R4, the series branch of the transistor TR5 and the resistor R12, and the series branch of the resistor R10 and the transistor TR4, respectively. It's summery.
The transistor TR1 is turned on when the transistor TR2 is turned on by a power supply control signal SPC from the central processing unit 1 shown in FIG.
The DC voltage boosted by the converter 3 is charged into the main capacitor C.
The terminal voltage is applied to the light emitting/trigger circuit 4, and also to the light emitting display circuit which is made up of a resistor R5, a neon tube NE, a resistor R6, and a resistor R7 connected in series. The connection point between the resistor R6 and the resistor R7 of this display circuit capable of emitting light is connected to the base of the transistor TR3, and the resistor R8 is connected to the base of the transistor TR3.
The base of the transistor TR4 is connected to the base of the transistor TR4 through a resistor R9. Further, the collector of the transistor TR4 is connected to the base of the transistor TR5 via a resistor R11. The emitter of the transistor TR3 is connected to the light emission enable signal input terminal of the central processing unit 1 shown in FIG. 1 as an output portion of the light emission enable signal RL. This light emission enable signal RL indicates that the charging curve a of the main capacitor shown in Fig. 3 has reached the voltage at which the strobe can emit light (e.g., 250 V, at which a light intensity of about 1 EV below the specified light emission level can be obtained). At this time, the neon tube NE discharges and the transistor TR3 turns on, thereby producing an output.
Further, the collector of the PNP type transistor TR5 is connected to the charge completion signal input terminal of the central processing unit 1 shown in FIG. 1 as an output portion of the charge completion signal FC. This charging completion signal FC is generated when the main capacitor C is sufficiently charged and the charging curve a of the main capacitor shown in FIG. The signal is output when TR4 and transistor TR5 are turned on.

In FIG. 1, the central processing unit 1 includes a first reference time setting section that sets a predetermined time from the start of charging of the main capacitor C as a first reference time, and a predetermined time from the time when the light emission enable signal RL arrives. It has a second reference time setting section that sets the time as a second reference time, and if the flash unit 2 does not output the light emission enable signal RL within the first reference time, or even if the light emission enable signal RL is output within the first reference time. Even if the strobe unit 2 is output, the strobe unit 2
It has an arithmetic control section that turns off the power to the strobe using the power supply control signal SPC when the charge completion signal FC is not output from the controller.

Next, the operation of the above embodiment will be explained with reference to FIG. Now, when the power control signal SPC is output from the central processing unit 1 based on an operation such as popping up the light emitting part of a strobe, the transistor TR2 shown in FIG. starts operating and charging of the main capacitor C starts.
Simultaneously with the start of charging, a first reference time T1 is set in the first reference time setting section of the central processing unit 1. Then, it is determined whether the light emission enable signal RL has arrived within this first reference time T1, and if the light emission enable signal RL has not come within the first reference time T1, the battery E has been exhausted to the extent that it cannot emit light. Assuming that the battery E is completely exhausted, the power supply control signal
Turn SPC to "L" to turn off transistors TR2 and TR1 in the strobe unit 2, and turn off the power supply to the strobe. On the other hand, in determining whether the light emission enable signal has arrived within the first reference time, if the light emission enable signal RL has come within the first reference time T1, the second reference time setting section of the central processing unit 1: A second reference time T2 is set from the time when the light emission enable signal RL is output. Then, it is determined whether the charge completion signal FC has arrived within this second reference time T2, and if the charge completion signal FC has not come within the second reference time T2, the battery E is prevented from being completely exhausted. In addition, when the charge completion signal FC comes within the second reference time T2, the power supply to the strobe is also turned off to prevent power wastage. .

In the above embodiment, the second reference time setting section sets the second reference time T2 as the time from the time when the light emission enable signal RL is output from the strobe unit 2. It is sufficient that the end period is a predetermined time, and therefore, the second reference time may be set from the time when charging of the main capacitor of the strobe starts. FIG. 5 shows the operation in that case. In the example of FIG. 5, when the strobe power is turned on by the power supply control signal SPC, the first reference time T1 and the second reference time T
2, and then it is determined whether the light emission enable signal RL has arrived within the first reference time T1. If the light emission enable signal RL does not arrive within the first reference time T1, the power supply to the strobe is turned off to prevent the battery E from being completely exhausted, and
If the light emission enable signal RL has arrived within the second reference time T2, it is determined whether the charge completion signal FC has come within the second reference time T2. If the charging completion signal FC does not arrive within the second reference time T2, the power supply to the strobe is turned off to prevent the battery E from being completely exhausted, and charging is completed within the second reference time T2. Even when the signal FC arrives, the power supply to the strobe is turned off to prevent battery E from being consumed.

In both examples, the power supply to the strobe is turned off before the strobe consumes the energy in battery E, so the remaining energy is used to wind the film and It is possible to drive the rewinding device, etc., and the inconvenience of having to take the camera into a darkroom or the like to take out the loaded film can be eliminated.

Note that in the illustrated embodiment, in order to prevent battery consumption, the power supply to the strobe is turned off even if a charge completion signal is received within the second reference time. This configuration is not an essential component of the present invention, and charging may be continued if the charging completion signal is received within the second reference time.

(Effect) According to the present invention, if a light emission enable signal is not received from the strobe within the first reference time, or if a charging completion signal is not received from the strobe within the second reference time, power supply to the strobe is stopped. By turning off the flash, the battery is prevented from being completely exhausted while the flash is in use.Thus, even if the camera has a motor-based film winding and rewinding device, at least the winding and rewinding functions are The energy necessary to drive the return device can be saved, and the camera user can reliably take out the loaded film even in the final stage of battery exhaustion.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a circuit diagram showing an example of the circuit configuration of a strobe that can be used in the present invention, and Fig. 3 is a characteristic diagram showing the charging curve of the main capacitor of the strobe. , FIG. 4 is a flowchart showing the operation of the embodiment of the present invention, and FIG.
The figure is a flowchart showing the operation of another embodiment of the present invention. E... Battery, S1... Main capacitor, RL... Light emission enable signal, FC... Charging completion signal, SPC... Power control signal, 1... Central processing unit, 2... Strobe unit, C... Main capacitor.

Claims (1)

[Claims] 1. Has a light emission enable signal output section that outputs a signal when the main capacitor is charged to a light emission enabled voltage and a charge completion signal output section that outputs a signal when the main capacitor is sufficiently charged beyond the light emission enabled voltage. A strobe, a first reference time setting unit that sets a predetermined time from the start of charging of the main capacitor as a first reference time, and a time point at which charging of the main capacitor starts or a time when a light emission enable signal is output from a light emission enable signal output unit. a second reference time setting section that sets a predetermined time from 2000 to 2000 as a second reference time and sets the end of the second reference time later than the end of the first reference time; A power supply circuit for a camera with a built-in strobe, comprising an arithmetic control unit that turns off the power of the strobe when the strobe is not output or a charge completion signal is not output within a second reference time.