JP2000066278A - Stroboscopic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stroboscopic device capable of enhancing the efficiency of charge, preventing heat generation and economically utilizing a power supply without using a current limit circuit. SOLUTION: A blocking oscillation circuit consisting of a transistor Q1, an oscillation transformer T1 and a resistance R1 or the like increases and converts the voltage of a power supply of a battery pack 2 to generate a high- voltage power supply. A light emission circuit 5 receives the supply of power and a light emission driving signal from a digital camera circuit 1 and emits strobe light. A voltage detecting element 7 generates a detection signal when the voltage of the power supply of the battery 2 is lower than a voltage value in which the normal action of the circuit 1 is guaranteed. When a transistor Q3 receives the detection signal from the element 7, it stops the oscillation of the blocking oscillation circuit to stop the supply of the power to the circuit 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera strobe device.

[0002]

2. Description of the Related Art When power is supplied to a strobe device built in a camera, the voltage of a battery that supplies power to the camera is converted into a high voltage by a converter circuit and supplied. In the charging circuit of a conventional flash unit, a large current flows in the initial stage of charging, which lowers the power supply voltage of the camera and stops the function of the microcomputer used to control the camera. When the operation is managed by the microcomputer, there is a disadvantage that the camera cannot be operated until the power supply voltage is restored.

[0003] In order to maintain the function of the camera,
In order to prevent a large current from flowing, a current limiting circuit including a resistor, a transistor, and the like is added to a stage preceding the charging circuit of the strobe device.

[0004]

However, when a current limiting circuit including a resistor and a transistor is used, charging efficiency is deteriorated, and heat generation of the resistor and the transistor may adversely affect a microcomputer and other circuits. There was a problem. Furthermore, even when the battery has a sufficient voltage, the charging current is limited by the current limiting circuit, which is uneconomical. SUMMARY OF THE INVENTION It is an object of the present invention to provide a strobe device that can increase charging efficiency and prevent heat generation without using a current limiting circuit, and can use a power supply economically.

[0005]

According to the present invention, there is provided a voltage converting means for generating a second DC power by boosting the voltage of a first DC power supply, and supplying and supplying a light emission drive signal for the second DC power. Strobe light emitting means for emitting strobe light in response to the
Voltage detecting means for generating a detection signal when the voltage of the first DC power supply drops below a predetermined value; and receiving the detection signal from the voltage detecting means, the strobe light is emitted to the voltage conversion means. Power supply stopping means for stopping the supply of the second DC power to the means. According to the present invention, the voltage of the first DC power supply drops below a predetermined value when the second DC power supply generated by boosting the voltage of the first DC power supply is supplied to the strobe light emitting means. In some cases, the second
To stop supplying DC power to the

[0006]

An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a circuit diagram showing a configuration of a digital camera incorporating a strobe device of the present invention. FIG.
1, the digital camera circuit 1 is a circuit including a microcomputer, an operation detection circuit, an outside light detection circuit, and the like (not shown). When the battery pack 2 is mounted on the digital camera and the switch 3 is turned on, the power of the battery 4 is supplied to the camera body from the plus side terminal 2a and the minus side terminal 2b.

On the camera body side, a noise component of the power supply is removed by a capacitor C1 connected in parallel to the power supply supplied from the positive terminal 2a and the negative terminal 2b. The diode D1 has an anode connected to the positive side of the power supply and a cathode connected to the capacitor C2.
, And the other end of the capacitor C2 is connected to the negative side of the power supply. The voltage charged in the capacitor C2 via the diode D1 is applied to the digital camera circuit 1
Supplied to

One end of the capacitor C3 is connected to the positive side of the power supply, the other end is connected to the resistor R1, the base of the NPN type transistor Q1, the starting end of the secondary side of the oscillation transformer T1, and the other end of the resistor R1 is connected to the other end. Connected to the negative side of the power supply. The emitter of the transistor Q1 is connected to the positive side of the power supply. Oscillation transformer T1
Is connected to the negative side of the power supply, and the terminal side is connected to the collector of the transistor Q1.

At the secondary terminal of the oscillation transformer T1,
The anode of the capacitor C4 and the diode D2 are connected, and the other of the capacitor C4 is connected to the negative side of the power supply. The cathode of the diode D2 is connected to the capacitor C
5, and the other end of the capacitor C5 is connected to the negative side of the power supply.

Light emitting circuit 5 constituting strobe light emitting means
Has one electrode of the strobe tube 6 connected to the positive side of the power supply, and the other electrode connected to the negative side of the power supply. The pulse transformer T2 has its secondary end connected to the negative side of the power supply and its end connected to a transparent conductive coating 6a applied to the outer surface of the flash tube 6. The primary terminal side of the pulse transformer T2 is connected to the resistor R2 and the capacitor C6. The other end of the resistor R2 is connected to the positive side of the power supply, and the other end of the capacitor C6 is connected to the negative side of the power supply.

The primary end of the pulse transformer T2 is connected to the anode of the thyristor Q2, and the cathode of the thyristor Q2 is connected to the negative side of the power supply. The gate of the thyristor Q2 is connected to the light emission control terminal of the digital camera circuit 1. In the light emitting circuit 5, the resistor R3 is connected to the positive side of the power supply, the other of the resistors 3 is connected to the neon light emitting element NL1, and the other of the neon light emitting element NL1 is connected to the negative side of the power supply.

Next, a characteristic circuit of the present invention will be described. The power supply terminal of the digital camera circuit 1, that is, the cathode of the diode D1, is connected to the positive terminal VDD of the voltage detection element (voltage detector) 7, and the negative terminal VSS of the voltage detection element 7 is connected to the negative side of the power supply. I have. Then, the detection output terminal OUT of the voltage detection element 7 is connected to the base of the transistor Q3 and the resistor R5 via the resistor R4. The other end of the resistor R5 is connected to the positive side of the power supply. The emitter of the transistor Q3 is connected to the emitter of the transistor Q1 (that is, the positive side of the power supply), and the collector is connected to the base of the transistor Q1.

Next, the operation of the circuit shown in FIG. 1 will be described. When the switch 3 of the battery pack 2 is turned on,
A blocking oscillation circuit is configured by the transistor Q1, the capacitor C3, the resistor R1, and the oscillation transformer T1. Then, a charging current flows to the capacitor C5 through the diode D2, and the terminal voltage of the capacitor C5 is supplied to the light emitting circuit 5. That is, the voltage of the battery power supply (first power supply) is boosted by the blocking oscillation circuit and charged in the capacitor C5, and a high-voltage power supply (second power supply) is supplied to the light emitting circuit 5 by the capacitor C5.
At this time, a high voltage is applied to the neon light emitting element NL1 via the resistor R3, the neon light emitting element NL1 emits light, and the user is notified that strobe light emission is possible.

In this state, when the shutter of the camera is pressed and a light emission drive signal is supplied from the digital camera circuit 1 to the gate of the thyristor Q2 of the light emitting circuit 5, the thyristor Q2 is turned on and is turned on via the pulse transformer T2. Then, a trigger voltage is applied to the transparent conductive coating 6a of the strobe tube 6, and the strobe tube 6 conducts to emit strobe light. The electric charge stored in the capacitor C5 at the time of this light emission becomes a current consumed by the strobe tube 6. Therefore, after the strobe light emission, a charging current flows from the secondary side of the oscillation transformer T1 to the capacitor C5.

This charging current flows for 5 to 10 seconds, but has a considerably large current value for the first few seconds because the input impedance seen from the oscillation transformer T1 is small. For this reason, a phenomenon occurs in which the voltage of the battery power supply that supplies the current decreases. If this voltage drop is too large, the power supply voltage supplied to the digital camera circuit 1 will also drop. In this case, if the voltage drops below a voltage value that guarantees normal operation of the digital camera circuit 1, the function of the digital camera circuit 1 stops or malfunctions.

Therefore, the voltage of the power supply of the digital camera circuit 1 is monitored by the voltage detecting element 7, and it is detected that the voltage has dropped below a predetermined value (a voltage value that guarantees the normal operation of the digital camera circuit 1). At this time, a low-level detection signal is output from the detection output terminal OUT. This detection signal is input to the base of the transistor Q3 via the resistor R4. Therefore, transistor Q3 is turned on.

As described above, the emitter and the collector of the transistor Q3 are connected to the emitter and the base of the transistor Q1, respectively.
When the transistor 3 is turned on, the forward bias between the emitter and the base of the transistor Q1 is reduced.
1 turns off. As a result, the oscillation of the blocking oscillation circuit stops, no voltage is generated on the secondary side of the oscillation transformer T1, and the charging current to the capacitor C5 also stops.

As described above, according to the above-described embodiment, the blocking oscillation circuit including the transistor Q1, the oscillation transformer T1, the resistor R1, and the like boosts the voltage of the first DC power supply obtained from the battery power supply to increase the voltage. Voltage second
And a voltage conversion means for generating a DC power supply. The light emitting circuit 5 constitutes a strobe light emitting means for emitting strobe light in response to the supply of the second DC power supply and the light emission drive signal from the digital camera circuit 1 as the light emission drive means. The voltage detecting element 7 detects the diode D1 from the voltage of the first DC power supply, more precisely, the voltage of the first DC power supply.
And a voltage detecting means for generating a detection signal when the voltage obtained by subtracting the conduction voltage of the digital camera circuit falls below a voltage value that guarantees the normal operation of the digital camera circuit 1. When the transistor Q3 receives the detection signal from the voltage detection element 7, the transistor Q3 stops the oscillation of the blocking oscillation circuit and constitutes a power supply stop means for stopping the supply of the second DC power to the light emitting circuit 5. .

With this configuration, the voltage of the first DC power supply falls below a predetermined value when the second DC power supply generated by boosting the voltage of the first DC power supply is supplied to the strobe light emitting means. Then, the supply of the second DC power to the strobe light emitting means is stopped. Therefore, it is possible to provide a strobe device capable of increasing the charging efficiency and preventing heat generation without using a current limiting circuit, and using a power source economically.

In the above embodiment, the voltage detection element 7 is configured to generate a detection signal when the first DC power supply falls below a voltage value that guarantees normal operation of the digital camera circuit 1. A configuration may be adopted in which a predetermined value of the voltage to be compared is set according to the condition of the circuit 5 and a detection signal is generated when the voltage falls below the predetermined value.

[0021]

According to the present invention, when the voltage of the first DC power supply is boosted and the second DC power supply generated is supplied to the strobe light emitting means, the voltage of the first DC power supply is reduced. When the voltage falls below the predetermined value, the supply of the second DC power to the strobe light emitting means is stopped. Therefore, it is possible to provide a strobe device capable of increasing the charging efficiency and preventing heat generation without using a current limiting circuit, and using a power source economically.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a digital camera incorporating a strobe device according to an embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Digital camera circuit 2 Battery pack 4 Battery 5 Light emitting circuit 6 Strobe tube 7 Voltage detection element Q1, Q3 Transistor T1 Oscillation transformer

Claims (4)

[Claims] 1. A voltage converter for boosting the voltage of a first DC power supply to generate a second DC power supply, and emitting strobe light in response to the supply of the second DC power supply and a light emission drive signal. Strobe light emitting means, voltage detecting means for generating a detection signal when the voltage of the first DC power supply falls below a predetermined value, and when receiving the detection signal from the voltage detecting means, the voltage converting means And a power supply stopping means for stopping the supply of the second DC power to the strobe light emitting means. 2. The voltage conversion means has an oscillation circuit for boosting and converting the voltage of the first DC power supply, and the power supply stop means, when receiving the detection signal, activates the oscillation circuit. The strobe device according to claim 1, wherein oscillation is stopped. 3. The method according to claim 2, wherein the voltage detecting means generates the detection signal when a voltage of the first DC power supply supplied to the light emission driving means for generating the light emission driving signal falls below the predetermined value. The strobe device according to claim 1, wherein: 4. The voltage detection means generates the detection signal when a battery voltage supplied to a digital camera circuit that generates the light emission drive signal falls below a voltage value that guarantees normal operation of the digital camera circuit. The strobe device according to claim 3, wherein