JP3320250B2 - Electronic flash device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a D
The present invention relates to an electronic flash device for flash having a C-DC converter.

[0002]

2. Description of the Related Art Conventional DC-DC converters for flash include a forward converter and a flyback converter using one oscillation transistor.

FIG. 6A is a block diagram of a conventional DC-DC converter. The oscillation control signal “CGON” from the control circuit 2700 causes the oscillation control transistor 60
0 oscillates the PNP oscillation transistor 300,
The main capacitor 2600 is charged with the current I _S2 boosted by the transformer 1700 and rectified by the rectifier diode 200. After the charge level is confirmed by the detection circuit 2300, the light emitting circuit 2400 is operated. At this time, the main capacitor 26
As shown in FIG. 6B, the charging current I _S2 charged to 00 flows only while the PNP oscillation transistor 300 is on, and does not flow while it is off.

[0004]

However, in the above-described conventional example, the charging current flows only during the period when the PNP oscillation transistor 300 is on, and does not flow when the PNP oscillation transistor 300 is off. Occurs. Therefore, when a battery with a low voltage is used, the charging time is long and it is not possible to shoot until the charging is completed, so that there is a problem that the operability of the camera that performs flash shooting deteriorates.

Accordingly, it is an object of the present invention to provide an electronic flash device which eliminates a loss of charging time, shortens charging time and improves operability of a camera.

It is another object of the present invention to shorten the charging time to improve the operability of the camera, to reduce the number of IC terminals of the control circuit, to reduce the circuit scale, and to reduce the cost of parts. An object of the present invention is to provide an electronic flash device capable of reducing the number of flashes.

[0007]

According to a first aspect of the present invention, a power supply and a transformer comprising two divided primary windings and a power supply voltage booster are provided. Therefore, in an electronic flash device provided with a push-pull type DC-DC converter circuit having two PNP oscillation transistors for performing a switching operation and a switching element for controlling the operation of each PNP oscillation transistor,
An NP oscillation transistor, a first switch element for controlling the base of the first PNP oscillation transistor, and a first diode for connecting the cathode to the first switch element are connected in parallel to the battery. A first oscillation control circuit, a second PNP oscillation transistor, and a second PN
A second oscillation control circuit comprising a second switch element for oscillation control for controlling the base of the P oscillation transistor and a second diode connecting the cathode to the second switch element, and connected in parallel to the battery; , The anodes of third and fourth diodes are connected from one ends of the first and second switch elements, and the respective cathodes are connected to the transformer.
A rectifier circuit connected to one and the other ends of the secondary windings of the transformer , connected to the anodes of the fifth and sixth diodes by the one and the other ends of the secondary windings of the transformer, and having the respective cathodes in common; A control terminal for commonly controlling the first and second switch elements so as to start oscillation when turned on and stop oscillation when turned off .
Electronic flash device.

According to this structure, the push-pull DC
In the DC converter circuit, the first and second oscillation control circuits are respectively connected in parallel to the battery, and the outputs of the first and second oscillation control circuits are rectified by a rectifier circuit having a diode bridge configuration to obtain a charging current, The first for oscillation control
Since the second switch element and the second switch element are controlled by the common control terminal, a sufficient charging current is supplied to eliminate the loss of charging time, and each switch element can be controlled by the common control terminal.

According to another configuration for realizing the object of the invention according to the present invention, a power supply and a transformer including two divided primary windings and a switch operation for boosting a power supply voltage are performed. In an electronic flash device provided with a push-pull type DC-DC converter circuit having two PNP oscillation transistors and an NPN oscillation control transistor for controlling the operation of each PNP oscillation transistor, the first P
An NP oscillation transistor, a first NPN transistor for oscillation control for controlling the bases of the first PNP oscillation transistor, and a first diode having a cathode connected to the emitter of the first NPN transistor, and arranged in parallel with the battery. A first oscillation control circuit to be connected; a second PNP oscillation transistor; a second NPN transistor for oscillation control for controlling a base of the second PNP oscillation transistor;
A second oscillation control circuit comprising a second diode having a cathode connected to the emitter of the NPN transistor and connected in parallel with the battery; and a first and a second NP.
The anodes of the third and fourth diodes are connected to the emitter of the N transistor, and the respective cathodes are connected to one and the other ends of the secondary winding of the transformer. A rectifier circuit in which the anodes of the fifth and sixth diodes are connected to each other and whose cathodes are common, and a rectifier circuit connected to the bases of the first and second NPN transistors, respectively.
The anode of the diode further comprising one of the oscillation control terminal stops oscillating by stopping the supply of starts oscillation current by supplying electric current by a common single terminal control
It is an electronic flash device characterized by the following.

According to this configuration, the push-pull type DC-
In a DC converter circuit, first and second oscillation control circuits are connected in parallel to batteries, respectively, and the first and second oscillation control circuits are connected in parallel.
The output of the oscillation control circuit is rectified by a rectifier circuit having a diode bridge configuration to generate a charging current, and the first and second NPN transistors for oscillation control are controlled by one terminal from a common control terminal. Supply becomes possible and the first and second oscillation circuits can be started by current control from the common terminal.

Still another configuration for realizing the object of the invention according to the present application is a transformer comprising a power supply and two divided primary windings and a switch operation for boosting a power supply voltage. FE for controlling the operation of two PNP oscillation transistors to be operated and each PNP oscillation transistor
Push-pull DC-DC converter circuit with T
In the electronic flash device provided with the first PNP oscillation transistor, a first FET for oscillation control for controlling a base of the first PNP oscillation transistor, and a first diode for connecting a cathode to a source of the first FET. A first oscillation control circuit configured and connected in parallel to the battery;
An NP oscillation transistor, a second FET for controlling the base of the second PNP oscillation transistor, and a second diode having a cathode connected to the source of the second FET and connected in parallel to the battery. A second oscillation control circuit, and a third source connected to the first and second FETs.
And the anodes of the fourth diodes are connected to each other, and the respective cathodes are connected to one and the other ends of the secondary winding of the transformer, and the fifth and sixth diodes are connected to the one and the other ends of the secondary windings of the transformer. A rectifier circuit in which the respective anodes are connected and the respective cathodes are connected in common, and oscillation is started and turned off by being connected to the respective gates of the first and second FETs and turned on by common one-terminal control. That there is one oscillation control terminal that stops oscillation at
The electronic flash device is a feature.

According to this configuration, the push-pull DC-
In a DC converter circuit, first and second oscillation control circuits are connected in parallel to batteries, respectively, and the first and second oscillation control circuits are connected in parallel.
The output of the oscillation control circuit is rectified by a rectifier circuit having a diode bridge configuration as a charging current, and the first and second FETs for oscillation control are controlled by one terminal from a common control terminal, so that a sufficient charging current is supplied. In addition, the activation of the first and second oscillation circuits can be controlled by turning on and off a common control terminal.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit block diagram of an electronic flash device according to a first embodiment of the present invention. The present embodiment shown in FIG. 1 has a battery 1 as a power supply, and a power supply unit of a power stabilizing capacitor 2 connected to both ends of the battery 1, and boosts the voltage of the battery 1 as a first oscillation control circuit. The first PNP oscillation transistor 3 has an emitter connected to one end of the battery 1, a collector connected to the oscillation transformer 17a, and a capacitor 4 and a resistor 5 connected in parallel between the emitter and the base. The first oscillation control NPN transistor 6 has a collector connected to the first PNP transistor.
Connected to the base of the oscillation transistor 3, the first PNP
On / off of the oscillation transistor 3 is controlled. A resistor 7 is connected between the base and the emitter of the NPN transistor 6.
The cathode of the first diode 8 is connected to the emitter, and the anode of the diode 8 is connected to the other end of the battery 1. The above constitutes the first oscillation control circuit.

The seventh diode 9 has a cathode connected to the base of the NPN transistor 6 and an anode connected to one end of the resistor 28 and the anode of the eighth diode 16 to perform one-terminal control.

Next, as a second oscillation control circuit, the battery 1
The second PNP oscillating transistor 10 for boosting the voltage is connected with an emitter connected to one end of the battery 1, a collector connected to the oscillation transformer 17b, and a capacitor 11 and a resistor 12 connected in parallel between the emitter and the base. I have. The second oscillation controlling NPN transistor 13 has a collector connected to the second PPN transistor 13.
It is connected to the base of the NP oscillation transistor 10 to control on / off of the second PNP oscillation transistor 10. A resistor 14 is connected between the base and the emitter of the NPN transistor 13, and a second diode 15 is connected to the emitter.
The anode of the diode 15 is connected to the other end of the battery 1. The above constitutes the second oscillation control circuit. These first and second oscillation control circuits are both connected to the battery 1 in parallel.

The eighth diode 16 has a cathode connected to the base of the second NPN transistor 13 and an anode connected to one end of the resistor 28 and the anode 9 of the seventh diode to perform one-terminal control.

The primary winding of the transformer 17 for boosting the oscillation is divided into 17a and 17b.
Is connected to the collector of the first PNP oscillation transistor 3, and the other end is connected to the other end of the battery 1.

One end of the primary winding 17b is connected to the collector of the second PNP oscillation transistor 10, and the other end is connected to the other end of the battery 1 and the other end of the primary winding 17a. The connection between the primary winding 17a and the collector of the first PNP oscillation transistor 3 and the connection between the primary winding 17b and the collector of the second PNP oscillation transistor 10 are based on the former: the winding start (black dot mark side) In the latter, the polarity is different as if they were connected at the end of winding.

The feedback winding 17 c has one end connected to the emitter of the second oscillation control NPN transistor 13 and the other end connected to one end of the resistor 18. The feedback winding 17d has one end connected to one end of the resistor 18 and the other end connected to the first oscillation control NP.
Connected to the emitter of N transistor 6. Resistance 18
Is connected to the other end of the battery 1. In this case, the feedback windings 17c and 17d are provided for facilitating the start-up of the oscillation and for preventing the oscillation from being stopped when the charging load by the booster circuit becomes light, and for performing the stable oscillation. .

Next, the cathode of the high voltage rectifier diode 19 is connected to one end of the secondary winding 17e of the oscillation transformer 17,
Its anode is the second oscillation control NPN transistor 1
3 is connected to one end of the feedback winding 17c of the oscillation transformer 17. The anode of the high voltage rectifier diode 20 is connected to one end of the secondary winding 17 e and the high voltage rectifier diode 19.
Connected to the cathode. The cathode of the high voltage rectifier diode 21 is connected to the other end of the secondary winding 17e, and its anode is connected to the emitter of the first oscillation control NPN transistor 6 and the other end of the feedback winding 17d. The other end of the secondary winding 17e and the cathode of the high voltage rectifier diode 21 are connected to the anode of the high voltage rectifier diode 22. The cathode of the diode 22 is connected to one end of the main capacitor 26 in common with the cathode of the high voltage rectifier diode 20. are doing.

A bridge rectifier circuit is constituted by the four high-voltage rectifier diodes. Further, the configuration from the first PNP oscillation transistor 3 to the high-voltage rectifier diode 22 described above is a push-pull DC-DC converter circuit that operates as a booster circuit.

A detecting circuit 2 for detecting the charging voltage when the voltage of the battery 1 is boosted by the boosting circuit and the main capacitor 26 is charged.
Reference numeral 3 denotes a circuit composed of, for example, a zener diode and a divided resistor. The detected charge level is input to the control circuit 27 as a signal CGUP. The light emitting circuit 24 is a circuit including a known trigger capacitor and a trigger coil for generating a high-voltage trigger pulse for discharging the electric charge charged in the main capacitor 26 to the flash discharge tube 25.
In response to a pulse signal output from the RG signal terminal, a high voltage trigger signal is given to the flash discharge tube 25 to emit light. Both the detection circuit 23 and the light emitting circuit 24 are connected to both ends of the main capacitor 26.

The flash tube 25 has an anode as a main condenser 26
And the cathode is connected to the other end of the main capacitor 26 and is triggered by the light emitting circuit 24. The main capacitor 26 is a capacitor for charging energy required for flash emission, and is connected to both ends of the flash discharge tube 25.

The control circuit 27 is constituted by a one-chip microcomputer or the like, and is a one-chip IC circuit built in a microcomputer including a CPU, a ROM, a RAM, an input / output control circuit, a multiplexer, a timer circuit, etc., and can control the camera system by software. thing. The power supply uses the output Vcc of the constant voltage circuit 29.

The signal terminals related to the flash of the control circuit 27 include a CGON terminal, a CGUP terminal, and a TRG terminal. The CGON terminal is a resistor for supplying a drive current to the first and second oscillation control NPN transistors 6 and 13. 28
The oscillation control signal is a one-terminal control oscillation signal that starts oscillation by changing from Lo Level (hereinafter, referred to as LL) to Hi Level (hereinafter, referred to as HL), and stops oscillation by changing to LL. . Thus, it is not necessary to provide two oscillation control terminals separately.

The CGUP terminal detects an input signal from the detection circuit 23, monitors the charging voltage of the main capacitor 26, performs level detection, and determines by the CPU of the control circuit 27 to inhibit the boosting circuit from oscillating. This is a charge detection signal for controlling release.

The TRG terminal is an output signal terminal connected to the light emitting circuit 24, sends a one-shot signal pulse to the light emitting circuit 24, outputs a high-voltage pulse signal by a trigger capacitor and a trigger transformer, and triggers the flash discharge tube 25. This is a light emission output terminal for emitting light. The constant voltage circuit 29 outputs a constant voltage Vcc even if the voltage of the battery 1 changes, and 30 is a switch circuit such as a release switch.

FIG. 2 is a flowchart of the operation of the embodiment shown in FIG. FIG. 3 is an operation explanatory diagram of the embodiment shown in FIG.

Next, the operation will be described with reference to the drawings. First, initialization is performed (S1). That is, the control circuit 2
7 clears the program flag of the microcomputer and resets the contents of the memory.

A charge level of the main capacitor 26 is detected from a detection circuit 23 for detecting a voltage of the main capacitor 26 by a CGUUP signal, and a predetermined charge completion level (hereinafter referred to as a charge completion level) for emitting light sufficient for photographing by a camera. (Abbreviated as level)
Is determined (S2). If the result is not equal to or higher than the satisfaction level, the process proceeds to S3.

By changing the output signal of the CGON terminal of the control circuit 27 from LL to HL (for example, from 0 V to 5 V), the first NPN transistor 6 and the second NPN transistor 6 are connected via the resistor 28, the diode 9 and the diode 16. A current flows to the base of the transistor 13 to turn on (S3).

In this case, the first and second NPs for oscillation control
When the N transistors 6 and 13 are turned on, the first and second P
Although the base currents of the NP oscillation transistors 3 and 10 are pulled and turned on, the current amplification factor h _FE is large due to variations in the elements of the PNP oscillation transistor 3 and the PNP oscillation transistor 10 (variations in the current amplification factor h _FE ). The PNP oscillation transistor starts oscillating first. For example, assuming that h _{FE of} the first oscillation transistor 3 is larger than that of the second PNP oscillation transistor 10, first, when the first PNP oscillation transistor 3 is turned on, the battery 1 passes through the emitter and the collector via the collector. Transformer 1
7, a current I _P1 flows through the primary winding 17a.

FIG. 3A is a diagram showing a current flow when the first PNP oscillation transistor is turned on. FIG. 3B is a diagram showing a current flow when the second PNP oscillation transistor is turned on. A more detailed operation will be described with reference to the drawings.

When the NPN transistor 6 is turned on,
Along the current path indicated by the arrow line in FIG. 3A, current flows from the battery 1 through the emitter and base of the PNP oscillation transistor 3, passes through the collector and emitter of the NPN transistor 6, and partially returns. Although the current flows through the resistor 18 through the line 17d, an induced current flows through the secondary winding 17e due to the current I _P1 flowing through the primary winding 17a, and the current flowing through the emitter of the NPN transistor 6 passes through the diode 21 through the transformer 17. , And charges the main capacitor 26 via the diode 20. This secondary current is shown in FIG.
Let it be I _S1 as shown in FIG.

The primary current I _P1 flowing through the primary winding 17a flows rapidly, but when a certain current flows and the transformer 17 is magnetically saturated, the primary current I _P1 is stopped and does not flow rapidly, and the polarity of the transformer 17 is inverted. I do.

At this time, the secondary winding 17e and the feedback winding 17d
In both cases, the polarity is inverted. Accordingly, the secondary current I _S1 stops flowing, the first oscillation control NPN transistor 6 is turned off, the first PNP oscillation transistor 3 is turned off, and the first oscillation control circuit stops oscillation.

However, since the CGON signal is HL, the second oscillation control NPN transistor 13 is in the ON state,
A current flows to the resistor 18 via the feedback winding 17c of the transformer 17, draws the base current of the second PNP oscillation transistor 10, and when the PNP oscillation transistor 10 is turned on, the primary winding 17 passes from the battery 1 through the emitter and the collector.
In FIG. 3B, a current I ′ _P1 flows as shown in FIG.

[0038] Similarly flow induced current I _'P1 by the secondary winding 17e through the primary winding 17b, the emitter of the second PNP oscillation transistor 10, through the base, the current flowing through the emitter of the NPN transistor 13 Diode 1
9, through the secondary winding 17e and through the diode 22 to charge the main capacitor 26. This secondary current is shown in FIG.
_Let it be I ' _S1 as in (b).

Then, the primary current is similarly cut off by magnetic saturation, the polarity of the transformer 17 is inverted, and the same operation is repeated. In this manner, the main capacitor 26 is repeatedly charged by the first and second oscillation circuits.

Here, the difference between the charging of the main capacitor 26 and the conventional example will be compared.

FIG. 4 is a timing chart of the charging current of the circuit shown in FIG. In the case of the conventional example of FIG. 6B, no current flows during the off-period of the oscillation transistor 300, resulting in a loss of charging time. In the case of the present example of FIG.
A secondary current I _S1 of the oscillator circuit, so that alternately charged by the secondary current I _'S1 of the second oscillation circuit, always that supplies a charging current to the main capacitor 26, compared with the prior art Thus, the charging time can be shortened, and furthermore, the effect of reducing the number of terminals can be expected by controlling both oscillation circuits by one terminal control of CGON.

Here, returning to the flowchart of FIG.
When the charge completion level is reached, the CGON terminal of the control circuit 27 is changed from HL to LL, and the base current of the first NPN transistor 6 and the second NPN transistor 13 is cut off via the resistor 28, the diode 9, and the diode 16, and is turned off. (S4).

At this time, a high potential is generated at the emitter of the NPN transistor 6 or the NPN transistor 13 by the feedback winding 17c or 17d.
Or, since it is bypassed by the diode 15, N
The PN transistor 6 or 13 is not destroyed. When the NPN transistor 6 or 13 is turned off, the PNP oscillation transistor 3 or 10 is also turned off and oscillation stops.

It is determined whether the release switch 30 is on (S5). If it is turned on, the operation of a known shutter aperture drive circuit (not shown) starts according to the shutter speed aperture determined by a known photometric circuit (not shown) (S6).

A trigger is output from the TRG signal terminal of the control circuit 27 at a light emission timing determined by a known light measuring circuit and a distance measuring circuit (not shown) (S7). In response to the trigger output, a trigger pulse is output from the light emitting circuit 24 to the flash discharge tube 25 to emit light (S8). When the light quantity reaches the appropriate level, the light emission is stopped (S9). The shutter stop driving operation is stopped (S1).
0). Then, the operation for the flash is completed.

Next, a second embodiment of the present invention will be described.

FIG. 5 is a circuit block diagram of an electronic flash device according to a second embodiment of the present invention. The configuration of the second embodiment shown in FIG. 5 which is different from that of the previous embodiment is different from that of the previous embodiment in that the oscillation control N
In this configuration, the PN transistor circuit is replaced by an FET (field effect transistor) circuit, and the first NPN transistor 6 is connected to the FET 60 by the second NPN transistor 13.
Is replaced by the FET 130.

The FET 60 has a drain connected to the base of the first PNP oscillation transistor 3, and a protection resistor 70 and a capacitor 90 connected in parallel between the gate and the source. The FET 130 has a drain connected to the base of the second PNP oscillation transistor 10, a protection resistor 140 and a capacitor 160 connected in parallel between the gate and source, and
Both the gate of the ET 60 and the gate of the FET 130 are connected to the CGON terminal of the control circuit 27 to perform one-terminal control.

The other components such as the first and second PNP oscillation transistor circuits, the rectifier circuit, the light emitting circuit, and the like are the same as those of the previous embodiment.

Regarding the operation, the FET 60 controls the first PNP oscillation transistor 3 instead of the NPN transistor 6 of the previous embodiment, and the FET 130 controls the second PNP oscillation transistor 10 instead of the NPN transistor 13. It is exactly the same except that it is.

In this case, the gates of the FET 60 and the FET 130 are connected to the CGON terminal to perform one-terminal control, and the control is performed by voltage control via the capacitors 90 and 160.

As described above, in the second embodiment, the FET 60
And the first PNP oscillation transistor
Controls the second PNP oscillation transistor 10 by
As in the previous embodiment, the secondary current of the first oscillation control circuit and the secondary current of the second oscillation control circuit are repeated, and the main capacitor is always charged, so that the charging time is shortened. The control makes it possible to further reduce the number of parts.

[0053]

As described above, according to the first aspect of the present invention, a transformer including a power supply and two divided primary windings and two switches for performing a switching operation for boosting the power supply voltage. Electronic flash having a push-pull DC-DC converter circuit having a PNP oscillation transistor and a switch element for controlling the operation of each PNP oscillation transistor
In an optical device , a first PNP oscillation transistor and a first
A first oscillation control circuit comprising an oscillation control first switch element for controlling the base of the PNP oscillation transistor and a first diode connecting the cathode to the first switch element and connected in parallel to the battery A second PNP oscillation transistor, a second switching element for controlling the base of the second PNP oscillation transistor, and a second diode for connecting a cathode to the second switching element; A second oscillation control circuit connected in parallel with the first and second switch elements;
And each connecting the anode of the fourth diode
Are connected to one and the other end of the secondary winding of the transformer.
And a rectifier circuit in which the anodes of the fifth and sixth diodes are connected from one and the other ends of the secondary winding of the transformer and the cathodes of the rectifier circuits are common, and oscillation is started by turning on and off. The electronic flash device further comprises a control terminal for commonly controlling the first and second switch elements so as to stop the oscillation, so that a sufficient charging current is supplied to the main capacitor and the charging time is reduced. And to improve the operability by reducing the camera charging waiting time.

According to the second aspect of the present invention, the operation of the power supply and the transformer composed of the two divided primary windings, the two PNP oscillation transistors for switching operation for boosting the power supply voltage, and the operation of each PNP oscillation transistor are described. An electronic flash device including a push-pull type DC-DC converter circuit having an NPN oscillation control transistor for controlling an oscillation control for controlling a first PNP oscillation transistor and a base of the first PNP oscillation transistor First N
A first oscillation control circuit comprising a PN transistor and a first diode having a cathode connected to the emitter of the first NPN transistor and connected in parallel to the battery; a second PNP oscillation transistor and a second PNP oscillation A second oscillation control circuit comprising a second NPN transistor for oscillation control for controlling the base of the transistor, and a second diode connecting the cathode to the emitter of the second NPN transistor, and connected in parallel to the battery; And the anodes of the third and fourth diodes are connected to the emitters of the first and second NPN transistors, and the respective cathodes are connected to one and the other ends of the secondary winding of the transformer. The anodes of the fifth and sixth diodes are connected from one and the other ends of the next winding, and the respective cathodes are commonly used. A rectifier circuit, the first and second
One that starts oscillation by supplying a current to the anodes of the seventh and eighth diodes connected to the respective bases of the NPN transistors under a common one-terminal control and stops the oscillation by stopping the current supply Because it is an electronic flash device characterized by having an oscillation control terminal of, the charging time is shortened, the operability of the camera is improved, and
The oscillation circuit is started by one terminal so that the I
This is to reduce the number of C terminals, reduce the circuit scale, and reduce costs.

Further, according to the third aspect of the present invention, a power supply and a transformer comprising two divided primary windings and two PNPs which perform switching operation for boosting the power supply voltage.
In an electronic flash device including a push-pull DC-DC converter circuit having an oscillation transistor and an FET for controlling the operation of each PNP oscillation transistor, a first PN
A first FET for oscillation control for controlling the bases of the P oscillation transistor and the first PNP oscillation transistor, and a first F
A first oscillation control circuit comprising a first diode having a cathode connected to the source of the ET and connected in parallel to the battery; an oscillation controlling the second PNP oscillation transistor and a base of the second PNP oscillation transistor Second F for control
ET and the second connecting the cathode to the source of the second FET
A second oscillation control circuit, which is composed of a diode and is connected in parallel to the battery, and anodes of third and fourth diodes are connected from the sources of the first and second FETs, and each cathode is A rectifier circuit is connected to one and the other ends of the secondary winding of the transformer, and the anodes of the fifth and sixth diodes are connected from the one and the other ends of the secondary winding of the transformer. ,
One oscillation control terminal is connected to each gate of the first and second FETs and starts oscillation by turning on by a common one-terminal control, and stops oscillation by turning off the oscillation control terminal. Since it is an electronic flash device, the charging time is shortened and the operability of the camera is improved,
The number of components including the number of IC terminals of the control circuit can be reduced to further reduce costs.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of an electronic flash device according to a first embodiment of the present invention.

FIG. 2 is a flowchart of an operation of the electronic flash device shown in FIG.

FIG. 3 is an explanatory diagram of an operation of the electronic flash device shown in FIG.

FIG. 4 is a timing chart of a charging current of the electronic flash device shown in FIG.

FIG. 5 is a circuit block diagram of an electronic flash device according to a second embodiment of the present invention.

FIG. 6 is a view showing a conventional electronic flash device.

[Explanation of symbols]

 Reference Signs List 1 battery 2, 4, 11, 90, 160 capacitor 3 first PNP oscillation transistor 5, 7, 12, 14, 18, 28, 70, 140 resistor 6 first NPN transistor 8, 9, 15, 16 diode 10 Second PNP oscillation transistor 13 Second NPN transistor 17 Transformer 19, 20, 21, 22 High voltage rectifier diode 23 Detection circuit 24 Light emitting circuit 25 Flash discharge tube 26 Main capacitor 27 Control circuit 29 Constant voltage circuit 30 Switch circuit 60 First FET 130 Second FET

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-64-21425 (JP, A) JP-A-47-8977 (JP, A) JP-A-6-302390 (JP, A) JP-A-2- 193131 (JP, A) JP-A-57-205998 (JP, A) JP-A-7-22188 (JP, A) JP-A-54-176813 (JP, U) (58) Fields investigated (Int. ⁷ , DB name) G03B 15/04-15/05

Claims (3)

(57) [Claims] 1. A pusher comprising a power supply, a transformer comprising two divided primary windings, two PNP oscillation transistors for performing a switching operation for boosting a power supply voltage, and a switching element for controlling the operation of each PNP oscillation transistor. Electronic flash with pull-type DC-DC converter circuit
In the device , a first PNP oscillation transistor, a first switch element for oscillation control for controlling a base of the first PNP oscillation transistor, and a first switch element having a cathode connected to the first switch element.
The first diode connected in parallel with the battery
Oscillation control circuit, a second PNP oscillation transistor, a second switch element for oscillation control for controlling the base of the second PNP oscillation transistor, and a second diode connecting the cathode to the second switch element. A second oscillation control circuit connected in parallel to the battery, and anodes of third and fourth diodes connected from one ends of the first and second switch elements, and each cathode is
A rectifier circuit connected to one and the other ends of the secondary windings of the transformer , connected to the anodes of the fifth and sixth diodes by one and the other ends of the secondary windings of the transformer, and having a common cathode. And the first and the second so as to start the oscillation by turning on and stop the oscillation by turning off.
An electronic flash device comprising a control terminal for commonly controlling the switch elements. 2. A pusher comprising a power supply and a transformer comprising two divided primary windings, two PNP oscillation transistors for switching operation for boosting a power supply voltage, and an NPN oscillation control transistor for controlling the operation of each PNP oscillation transistor. Bei the pull-type DC-DC converter circuit
In the electronic flash device obtained above, a first PNP oscillation transistor and a first NPN for oscillation control for controlling a base of the first PNP oscillation transistor.
A first oscillation control circuit comprising a transistor and a first diode connecting the cathode to the emitter of the first NPN transistor and connected in parallel to the battery;
A second oscillation transistor for controlling the bases of the P oscillation transistor and the second PNP oscillation transistor; a second NPN transistor for oscillation control; and a second diode having a cathode connected to the emitter of the second NPN transistor. A second oscillation control circuit connected to the first and second NPN transistors;
The respective cathodes are connected to one and the other ends of the secondary winding of the transformer, and the anodes of the fifth and sixth diodes are connected from the one and the other ends of the secondary winding of the transformer. A rectifier circuit connected to each cathode and having a common cathode, and the first and second N
Oscillation is started by supplying a current to the anodes of the seventh and eighth diodes connected to the respective bases of the PN transistors by a common one-terminal control, and oscillation is stopped by stopping the current supply. An electronic flash device comprising an oscillation control terminal. 3. A push-pull DC having a power supply, a transformer comprising two divided primary windings, two PNP oscillation transistors for performing a switch operation for boosting a power supply voltage, and an FET for controlling the operation of each PNP oscillation transistor. An electronic flash device having a DC converter circuit , wherein: a first PNP oscillation transistor and a first FET for oscillation control for controlling a base of the first PNP oscillation transistor.
A first oscillation control circuit comprising a first diode having a cathode connected to the source of the first FET and connected in parallel with the battery; a second PNP oscillation transistor; and a base of the second PNP oscillation transistor. A second oscillation control circuit comprising a second FET for controlling oscillation, a second diode having a cathode connected to the source of the second FET, and connected in parallel to the battery; The anodes of the third and fourth diodes are connected from the source of the second FET, and the respective cathodes are connected to one and the other ends of the secondary winding of the transformer, and one and the other of the secondary winding of the transformer. The anodes of the fifth and sixth diodes are connected from the end and the respective cathodes are connected in common, and the common rectifier circuit is connected to the respective gates of the first and second FETs. Electronic flash apparatus characterized by comprising one of the oscillation control terminal to stop the oscillation by turning off starts oscillating by turning on the one terminal control.