JPH0933991A - Electronic flash device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic flash device provided with a push-pull type DC-DC converter constituted so that an oscillating action can be executed without dividing a feedback coil and the number of terminals of an oscillation transformer is reduced. SOLUTION: This device is equipped with the transformer 17 provided with a first PNP transistor for oscillation 3, a first switch, element 6 controlling the transistor 3, a second PNP transistor for oscillation 10, a second switch element 13 controlling the transistor 10, divided primary coils 17a and 17b and the feedback coil 17c used in common by connecting one end thereof to one end of the element 13 and connecting the other end thereof to one end of the element 6, a first resistance 31 connected between one end of the element 6 and the other end of a battery 1, a second resistance 18 connected between one end of the element 13 and the other end of the battery 1, high-voltage rectifier diodes 19-22 constituted to be like a bridge and a control circuit 27 executing a common oscillation control action by a signal CGON inputted from one terminal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flash electronic flash device having a DC-DC converter for boosting a power supply voltage.

[0002]

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

FIG. 9A is a block diagram of a conventional DC-DC converter.

An oscillation control signal "C" from the control circuit 2700
GON "causes the oscillation PNP transistor 300 to oscillate through the oscillation control transistor 600, and the main capacitor 2600 is charged with the current I _S2 boosted by the transformer 1700 and rectified by the rectifier diode 200. The charge level detection circuit After confirming with 2300, light emitting circuit 2
400 is operated.

At this time, the charging current I _S2 charged in the main capacitor 2600 is PN for oscillation as shown in FIG. 9B.
Since the P-transistor 300 flows only during the ON period and does not flow the charging flow during the OFF period, a charging time loss corresponding to the OFF period occurs and in the case of a low voltage battery, it takes a long charging time to complete the charging. The camera cannot be shot and the operability of the camera for flash photography is poor.

As a means for eliminating such inconvenience,
Japanese Patent Application No. 7-103211 filed by the present applicant has been filed.

6 and 7 are circuit block diagrams of the electronic flash device.

The electronic flash device shown in FIG. 6 is divided into two parts.
One primary winding 17a, 17b and a split feedback winding 1
A first oscillation PNP transistor 3 having 7c and 17d and controlled by the first oscillation control NPN transistor 6 and a second oscillation PNP transistor 10 controlled by the second NPN transistor 13. It is configured by a push-pull type DC-DC converter circuit having a.

The oscillation control signal "CGO" from the control circuit 27
Under the common control by N ″, the first and second oscillation control transistors 6 and 13 are simultaneously controlled to alternately output the first and second oscillation outputs, and the outputs are fridge-type rectified by the diodes 19 to 22. Rectify with the circuit, the main capacitor 26
To charge.

FIG. 8 is a diagram for explaining the operation of the circuit of FIG. 6, and FIG. 8A shows the flow of current when the oscillation transistor 3 is on.
FIG. 8B shows a current flow when the oscillation transistor 10 is turned on. First, when the oscillation transistor 3 in FIG. 8A starts to oscillate, as shown by the arrow, a part of the current flows from the oscillation transistor 3 through the emitter of the oscillation control transistor 6 to the resistor 18 through the feedback winding 17d. The rectified current I _S1 flows to the secondary side to charge the main capacitor 26. Then, the oscillation transistor 3 by oscillating transistor 10 is turned on and off, the current through the person of the feedback winding 17c flows through resistor 18, continue charging rectified current I _'S1 on the secondary side of the main capacitor 26 flows To do. As described above, the alternating outputs of the first and second oscillation controls are rectified by the rectifier circuit having the bridge configuration to be the charging current, and the first and second oscillation control transistors 6 and 13 are controlled from the common control terminal. As a result, the off time as shown in FIG. 9B is eliminated, a sufficient charging current can be supplied to eliminate the loss of the charging time, and the control by the common one terminal becomes possible.
The circuit shown in FIG. 7 has the same configuration and operation, except that the first and second oscillation control transistors 6 and 13 shown in FIG. 6 are replaced with FETs 60 and 130.

[0011]

However, in the above-mentioned conventional example, when the oscillation for charging is started, the starting is facilitated and the oscillation stop (halfway stop) is prevented when the charging load becomes light, so that stable oscillation is achieved. In order to maintain the current, the transformer 17 is provided with feedback windings 17c and 17d, one end of which is connected to the emitter of the second oscillation control transistor 13 and the other end of which is connected to one end of the resistor 18. ing. One feedback winding 17d has one end connected to one end of the resistor 18,
The other end is connected to the emitter of the first oscillation control transistor 6, and the resistor 18 is connected to the battery 1 at the other end. With the above-described structure, the feedback winding is divided into 17d for the first oscillation control circuit and 17c for the second oscillation control circuit, and these are operating independently.

Therefore, since the primary winding of the oscillating transformer is divided for the first and second oscillating circuits and the feedback winding is also divided to provide the terminals, the number of terminals of the oscillating transformer is increased and the winding method is increased. However, there is a problem that the transformer becomes complicated and the transformer becomes large.

Therefore, the object of the present invention is to provide a transformer consisting of a divided primary winding and feedback winding, two oscillating transistors for boosting the power supply voltage, and the operation of each oscillating transistor. A push-pull DC-DC converter having a switching element to control, enables oscillation operation without dividing the feedback winding, reduces the number of terminals of the transformer and downsizes the circuit scale, and reduces component cost. An object is to provide an electronic flash device.

[0014]

In order to achieve the above object, the present invention reduces the number of terminals of an oscillating transformer and enables miniaturization, and also reduces the circuit scale and component cost. Is.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION A structure for realizing the object of the invention according to the present application is, as described in claim 1, a power supply, a transformer having two divided primary windings and a feedback winding, and a power supply voltage. Two oscillating PNs that switch operation for boosting
Push-pull DC-D having a P-transistor and a switch element for controlling the operation of each oscillation PNP transistor
In the C converter circuit, a first oscillation PNP transistor, a first switching element for controlling oscillation that controls the base of the first oscillation PNP transistor, and a first diode that connects a cathode to the first switching element. A first oscillation control circuit configured to be connected in parallel to the battery; a second switching element for oscillation control that controls the bases of the second oscillation PNP transistor and the second oscillation PNP transistor; and a second oscillation control circuit. A second oscillation control circuit configured by a second diode having a cathode connected to the switch element and connected in parallel to the battery; and one end connected to one end of the second switch element and the other end connected to the first switch element. A feedback circuit including a feedback winding connected to one end of one switch element and a first and a second resistor connected in parallel to the first and second diodes, respectively. , The anodes of the third and fourth diodes are connected to one ends of the first and second switching elements, and the anodes of the fifth and sixth diodes are connected to one and the other ends of the secondary winding of the transformer. A rectifier circuit having common cathodes, and 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 And the electronic flash device.

According to this structure, in the electronic flash device including the push-pull type DC-DC converter circuit in which the first and second oscillation transistors are controlled by the switching elements for controlling the first and second oscillations, feedback is provided. Oscillation is possible without splitting the winding.

A specific configuration for achieving the object of the invention according to the present application is, as described in claim 2, a power supply, a transformer having two divided primary windings and a feedback winding, and a boosting of the power supply voltage. 2 oscillation PNs for switch operation
In a push-pull DC-DC converter circuit having a P-transistor and an NPN oscillation control transistor for controlling the operation of each oscillation PNP transistor, an oscillation for controlling a first oscillation PNP transistor and a base of the first oscillation PNP transistor A first oscillation control circuit configured by a first NPN transistor for control and a first diode having a cathode connected to the emitter of the first NPN transistor and connected in parallel to a battery; and a second oscillation PN.
A P-transistor and a second oscillating PNP transistor that control the bases of the second NPN transistor for oscillation control and a second diode whose cathode is connected to the emitter of the second NPN transistor and are connected in parallel to the battery. A second oscillation control circuit connected to the
A feedback winding connected to the emitter of the PN transistor and the other end thereof connected to the emitter of the first NPN transistor and shared by the first and second resistors connected in parallel to the first and second diodes, respectively. The feedback circuit is connected to the anodes of the third and fourth diodes from 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. A rectifier circuit in which the anodes of the fifth and sixth diodes are connected to one and the other ends of the secondary windings of each of the secondary windings, and the respective cathodes are common;
And oscillation of the seventh and eighth diodes connected to the respective bases of the second and NPN transistors starts by supplying a current under common one-terminal control and stops by stopping the supply of the current. The electronic flash device is characterized by having one oscillation control terminal.

According to this configuration, in the electronic flash device including the push-pull type DC-DC converter circuit in which the first and second oscillation transistors are controlled by the first and second oscillation control transistors, the feedback winding is used. Oscillation operation is possible without dividing.

A specific configuration for realizing the object of the invention according to the present application is, as described in claim 3, a power supply, a transformer having two split primary windings and a feedback winding, and boosting of the power supply voltage. 2 oscillation PNs for switch operation
In a push-pull DC-DC converter circuit having a P-transistor and an FET for controlling the operation of each oscillation PNP transistor, an oscillation control circuit for controlling a first oscillation PNP transistor and a base of the first oscillation PNP transistor is provided. A first oscillation control circuit configured by a first FET and a first diode having a cathode connected to the source of the first FET and connected in parallel to a battery; a second oscillation PNP transistor; and a second oscillation PNP transistor. A second oscillation control circuit configured by a second FET for oscillation control for controlling the base of the oscillation PNP transistor and a second diode for connecting a cathode to the source of the second FET and connected in parallel to the battery. And a feedback winding shared by connecting one end to the source of the second FET and the other end to the source of the first FET and the first and the second windings. A feedback circuit composed of first and second resistors connected in parallel to the second diode and the anodes of the third and fourth diodes are connected from the sources of the first and second FETs, and the cathodes of the respective diodes are connected. Rectifier circuit connected to one and the other ends of the secondary winding of the transformer, and connected to the anodes of the fifth and sixth diodes from one and the other ends of the secondary winding of the transformer, and having common cathodes And the first and second FEs
An electronic flash device is provided with one oscillation control terminal which is connected to each gate of T to turn on under common one-terminal control to start oscillation and to turn off to stop oscillation. .

According to this structure, the feedback is provided in the electronic flash device including the push-pull type DC-DC converter circuit in which the first and second oscillation transistors are controlled by the first and second oscillation control FETs. Oscillation is possible without splitting the winding.

[0021]

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 power source unit composed of a battery 1 as a power source and a power source stabilizing capacitor 2 connected to both ends of the battery 1, and the voltage of the battery 1 is used as a first oscillation control circuit. First oscillation PN for boosting
In the P-transistor 3, the emitter is connected to one end of the battery 1, the collector is connected to the oscillation transformer 17a, and the capacitor 4 and the resistor 5 are connected in parallel between the emitter and the base. First
The NPN transistor 6 for controlling the oscillation of the
Is connected to the base of the oscillating PNP transistor 3 to control ON / OFF of the first oscillating PNP transistor 3. A resistor 7 is connected between the base and the emitter of the NPN transistor 6, and the first diode 8 is connected to the emitter.
The cathode of the diode 8 is connected, 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 its cathode connected to the base of the NPN transistor 6, and its anode connected to one end of the resistor 28 and the anode of the eighth diode 16 for one-terminal control.

Next, as a second oscillation control circuit, the battery 1
The second oscillating PNP transistor 10 for boosting the voltage of is connected with the emitter at one end of the battery 1, the collector connected to the oscillating transformer 17b, and the capacitor 11 and the resistor 12 connected in parallel between the emitter and the base. There is. The second oscillation control NPN transistor 13 has a collector connected to the base of the second oscillation PNP transistor 10,
The ON / OFF of the oscillation PNP transistor 10 is controlled. A resistor 14 is connected between the base and the emitter of the NPN transistor 13, the cathode of a second diode 15 is connected to the emitter, and 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 2
The two oscillation control circuits are both connected in parallel to the battery 1.

The eighth diode 16 has its cathode connected to the base of the second NPN transistor 13, and its anode connected to one end of the resistor 28 and the anode of the seventh diode 9 for 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 oscillation PNP transistor 3 and the other end is connected to the other end of the battery 1.

One end of the primary winding 17b has a second oscillation PN.
Connected to the collector of P-transistor 10, the other end is battery 1
To the other end of the primary winding 17a. In addition,
The connection between the primary winding 17a and the collector of the first oscillating PNP transistor 3, and the primary winding 17b and the second oscillating PN
The collectors of the P-transistors 10 have different polarities such that the former is connected to the winding start (black dot mark side) and the latter is connected to the winding end.

The feedback winding 17c has one end connected to the emitter of the second oscillation control NPN transistor 13 and the resistor 18, and the other end connected to the emitter of the first oscillation control NPN transistor 6 and the resistor 31. . Moreover, the first resistor 31 which is connected in parallel with the first diode 8 and the second resistor 18 which is connected in parallel with the second diode 15 have their other ends connected to the other end of the battery 1. ing. As described above, the feedback winding 17c in the present embodiment is not the split type as in the conventional example, but is shared by the first oscillation control circuit and the second oscillation control circuit.

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,
The 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 17e 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 the anode thereof is connected to the emitter of the first oscillation control NPN transistor 6 and the other end of the feedback winding 17c. The other end of the secondary winding 17e and the cathode of the high voltage rectification diode 21 are connected to the anode of the high voltage rectification diode 22, and the cathode of this diode 22 is connected to one end of the main capacitor 26 in common with the cathode of the high voltage rectification diode 20. are doing.

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

Detecting circuit 2 for detecting the charging voltage when the voltage of the battery 1 is boosted by the boosting circuit to charge the main capacitor 26
Reference numeral 3 denotes a circuit composed of, for example, a Zener diode and a dividing resistor, and the detected charge level is input to the control circuit 27 by a signal CGUP. The light emitting circuit 24 is a circuit including a known trigger capacitor or trigger coil that generates a high voltage trigger pulse to discharge the electric charge charged in the main capacitor 26 to the flash discharge tube 25.
A high-voltage trigger signal is applied to the flash discharge tube 25 by the pulse signal output from the RG signal terminal to cause it 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 discharge tube 25 has an anode as a main capacitor 26.
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 that charges the energy required for flash emission, and is connected to both ends of the flash discharge tube 25.

The control circuit 27 is composed of a one-chip microcomputer or the like, and is a one-chip IC circuit with a built-in 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 relating 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 NPN transistors 6 and 13 for oscillation control. 28
The oscillation control signal is a one-terminal control that starts oscillation by changing from Lo Level (hereinafter referred to as LL) to Hi Level (hereinafter referred to as HL), and stops when LL is connected. .

The CGUP terminal detects the input signal from the detection circuit 23, monitors the charging voltage of the main capacitor 26, detects the level, and judges by the CPU of the control circuit 27 to inhibit the oscillation operation of the booster circuit. It is a charge detection signal that controls the release.

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

FIG. 2 is a flow chart 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, initial setting is performed (S1). That is, the control circuit 2
It clears the program flags of the microcomputer in 7 and resets the memory contents.

The detection circuit 23 for detecting the voltage of the main capacitor 26 detects the charge level of the main capacitor 26 with the CGUP signal, and a predetermined charge completion level (hereinafter referred to as charge completion level) is detected in order to emit sufficient light for photographing by the camera. (Abbreviated as level)
It is determined whether or not has reached (S2). When the result is not equal to or higher than the filling 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 0V to 5V), 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 through the base of the transistor 13 to turn it on (S3).

In this case, the first and second NPs for controlling oscillation
When the N-transistors 6 and 13 are turned on, the base currents of the first and second oscillation PNP transistors 3 and 10 are drawn and turned on. However, there are timing variations in the elements of the oscillation PNP transistor 3 and the oscillation PNP transistor 10. the (variations in the current amplification factor h _FE), the current amplification factor h _FE
The oscillating PNP transistor having a large oscillation starts oscillating first. For example, assuming that h _{FE of} the first oscillating transistor 3 is larger than that of the second oscillating PNP transistor 10, first, the first oscillating PNP transistor 3 is turned on, so that the emitter and collector of the battery 1 are increased. A current I _{P1 is} passed through the primary winding 17a of the transformer 17 via.

FIG. 3A is a diagram showing a current flow when the first oscillation PNP transistor is turned on.

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

When the NPN transistor 6 is turned on,
Current flows from the battery 1 along the current path indicated by the arrow in FIG. 3A to the emitter of the oscillation PNP transistor 3,
Through the base, through the collector and emitter of the NPN transistor 6, and through the feedback winding 17c, a part of the resistor 18
However, an induced current flows through the secondary winding 17e due to I _P1 flowing through the primary winding 17a, and the current flowing through the emitter of the NPN transistor 6 flows through the diode 21 to the secondary winding 17e of the transformer 17. Flow and charges the main capacitor 26 via the diode 20. This secondary current is 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 blocked and does not flow rapidly, and the polarity of the transformer 17 is reversed. To do.

At this time, the secondary winding 17e and the feedback winding 17c
Both polarities are reversed. Therefore, the secondary current I _{S1 stops} flowing, the first oscillation control NPN transistor 6 is turned off, and the first oscillation PNP transistor 3 is turned off.
The first oscillation control circuit stops oscillation.

However, since the CGON signal is HL, the second oscillation controlling NPN transistor 13 is in the ON state,
A current flows through the resistor 31 through the feedback winding 17c of the transformer 17, draws the base current of the second oscillation PNP transistor 10, and when the oscillation PNP transistor 10 is turned on, the primary winding is passed from the battery 1 through the emitter and collector. 17b, the current I'as shown in FIG.
_P1 flows.

[0047] Similarly by I _'P1 through the primary winding 17b flows induced current in the secondary winding 17e, the second oscillation PN
NPN via the emitter and base of the P-transistor
The current flowing through the emitter of the transistor 13 passes through the secondary winding 17e via the diode 19, and charges the main capacitor 26 via the diode 22. This secondary current is shown in FIG.
_{Let I'S1} as in (b).

Then, the primary current is similarly cut off due to magnetic saturation, the polarity of the transformer 17 is reversed, and the same operation is repeated. In this way, the main capacitor 26 is repeatedly charged by the first and second oscillator circuits.

Now, comparing the difference between the charging of the main capacitor 26 and the conventional example, in the conventional example, the feedback winding has the first and second oscillation control circuits as shown in FIGS. Separately, it is divided into 17c and 17d respectively, and NPN
When the transistor 6 is turned on, the current flows from the battery 1 to the oscillation P along the current course indicated by the arrow in FIG.
When the NPN transistor 13 is turned on, the operation such that a part of the current flows through the emitter / base of the NP transistor 3 and the collector / emitter of the NPN transistor 6 and the feedback winding 17d is performed. 8B, the current flows from the battery 1 through the emitter / base of the PNP transistor 10 and the collector / emitter of the NPN transistor 13 along the current path indicated by the arrow in FIG. It operates so as to flow to the resistor 18 via the. As described above, in the conventional example, the first oscillation control circuit and the second oscillation control circuit each have the independent feedback windings 17c and 17d.

In the present invention, such division of the feedback winding is stopped, and one end of the feedback winding 17c is connected so that the first oscillation control circuit and the second oscillation control circuit can operate with one feedback winding. The emitter of the second oscillation control NPN transistor 13 is connected to the resistor 18, and the other end is connected to the emitter of the first oscillation control NPN transistor 6 and the resistor 31.
And the other end of the resistor 31 is connected to the other end of the battery 1.

With this configuration, the NPN
When the transistor 6 is on, a current flows through the feedback winding 17c to the resistor 18, and when the NPN transistor 13 is on, the current flows through the feedback winding 17c to the resistor 31 to be shared.

In addition, as in the timing chart of the charging current of the circuit of FIG. 3 shown in FIG. 4, in the case of the circuit shown in FIG. 9B, since no current flows during the off period of the oscillation transistor 300, charging is performed. had become a time loss, in the present embodiment the secondary current I _S1 of the first oscillation circuit, since charged by the secondary current I _'S1 of the second oscillation circuit, always the main capacitor 26 Is supplying the charging current,
As compared with the circuit of FIG. 9 and the like, the charging time is shortened, and the number of terminals is reduced by using both oscillation circuits as one-terminal control of CGON.

Now, returning to the flowchart of FIG. 2 again,
When the charge completion level is reached, the CGON terminal of the control circuit 27 is changed from HL to LL, and the base currents of the first NPN transistor 6 and the second NPN transistor 13 are cut off via the resistor 28, the diode 9 and the diode 16. (S4).

At this time, a high potential is generated in the emitter of the PN transistor 6 or the NPN transistor 13 by the feedback winding 17c, but since it is bypassed by the diode 8 or the diode 15, the NPN transistor 6 or 13 is not destroyed. . When the NPN transistor 6 or 13 is turned off, the oscillation PNP transistor 3 or 10 is also turned off and the oscillation is stopped.
Determine whether the release switch 30 is on (S
5). If it is on, the operation of the known shutter diaphragm drive circuit (not shown) is started according to the shutter speed diaphragm determined by the known photometry circuit (not shown) (S6). Trigger output is made from the TRG signal terminal of the control circuit 27 at the light emission timing determined by a known photometry circuit and distance measurement circuit (not shown) (S7). By the trigger output, the light emitting circuit 24 outputs a trigger pulse to the flash discharge tube 25 to emit light (S
8). When the amount of light reaches an appropriate amount, the light emission is stopped (S9). The shutter diaphragm drive operation is stopped (S10). Then, the operation regarding the flash is completed.

As described above, according to this embodiment, the oscillation operation can be performed in a shared manner without dividing the feedback winding in the first and second oscillation control circuits, and the charging time can be reduced. It is also possible to shorten the number, and the common control can reduce the number of control terminals.

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 second embodiment shown in FIG. 5 is different from the previous embodiment in that the oscillation control NPN transistor circuit in the previous embodiment is replaced with a FET (field effect transistor) circuit, and the first NPN transistor 6 is used. Is F
In ET60, the second NPN transistor 13 is FET1
Has been replaced by 30.

The FET 60 has a drain for the first PN for oscillation.
It is connected to the base of the P-transistor 3, and a protection resistor 70 and a capacitor 90 are connected in parallel between the gate and the source. The FET 130 has a drain connected to the base of the second oscillation PNP transistor 10, a protection resistor 140 and a capacitor 160 are connected in parallel between the gate and the source, and the FET 60 and the FET 130 have both gates of the CGON terminal of the control circuit 27. It is connected to and has one terminal control.

Since the other configurations of the first and second oscillation PNP transistor circuits, the feedback circuit, the rectifier circuit, the light emitting circuit, etc. are the same as those in the previous embodiment, the same reference numerals are given and redundant description will be omitted.

In operation, the FET 60 controls the first oscillating PNP transistor 3 instead of the NPN transistor 6 of the previous embodiment, and the FET 130 replaces the NPN transistor 13 and the second oscillating PNP transistor 1.
It is exactly the same except that 0 is controlled.

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

As described above, in the second embodiment, the oscillation operation can be performed by sharing the feedback winding 17c between the first oscillation control circuit and the second oscillation control circuit, as in the previous embodiment. Since the main capacitor is always charged with the secondary current of both sides, the charging time is shortened, and the number of parts can be reduced by one-terminal control.

[0062]

As described above, according to the first aspect of the present invention, the power supply, the transformer having the two divided primary windings and the feedback winding, and the switch operation for boosting the power supply voltage. In a push-pull DC-DC converter circuit having two oscillating PNP transistors for controlling the oscillation and a switching element for controlling the operation of each oscillating PNP transistor, the oscillation control for controlling the first oscillating PNP transistor and its base A first oscillating control circuit comprising a first switch element and a first diode having a cathode connected to the switch element and connected in parallel to a battery; and a second oscillating PNP transistor and a base for controlling the second oscillating PNP transistor. A second oscillation control circuit composed of a second switch element and a second diode having a cathode connected to the switch element and connected in parallel with the battery. And one end connected to one end of the second switch element and the other end connected to one end of the first switch element and commonly connected in parallel to the feedback winding and the first and second diodes, respectively. A feedback circuit using the second resistor, and a third to one end of the first and second switch elements,
A rectifier circuit that connects the anode of the fourth diode and connects the anodes of the fifth and sixth diodes from one and the other end of the secondary winding of the transformer to the common cathode and starts oscillation by turning on Since the control terminal for controlling the first and second switching elements in common is provided so as to stop the oscillation when turned off, the first and second oscillation PNP transistors are controlled by the first and second switching elements. In the electronic flash device having the push-pull type DC-DC converter, it is possible to perform the oscillating operation without dividing the feedback winding, and it is possible to reduce the number of terminals of the oscillating transformer and to reduce the circuit size. The cost of parts can be reduced.

According to the invention described in claim 2, a transformer having a power supply, two primary windings and a feedback winding divided from each other, two oscillating PNP transistors for switching operation for boosting the power supply voltage, and each oscillation. In a push-pull type DC-DC converter circuit having an NPN oscillation control transistor for controlling the operation of a PNP transistor for oscillation, a first NPN transistor for oscillation control for controlling a first oscillation PNP transistor and its base and an emitter thereof are provided. A first oscillation control circuit composed of a first diode connecting a cathode and connected in parallel to a battery, and a second oscillation PNP.
Second oscillator control for controlling the transistor and its base
Second NPN transistor connected to the battery in parallel with the second diode connecting the cathode to the NPN transistor
An oscillation control circuit, a feedback winding which has one end connected to the emitter of the second NPN transistor and the other end connected to the emitter of the first NPN transistor, and the first
A first and a second diode respectively connected in parallel
And a feedback circuit using the second resistor, the first and second NPs
The emitters of the N-transistors are connected to the anodes of the third and fourth diodes, the cathodes of which are connected to one end and the other end of the secondary winding of the transformer, and the fifth end is connected to one and the other end of the secondary winding of the transformer. A rectifier circuit in which the anode of the sixth diode is connected and the cathode is common, and the first and second NPN
One oscillation control that starts oscillation by supplying current and stops oscillation by stopping current supply by common one-terminal control to the anodes of the seventh and eighth diodes connected to each base of the transistor Since the terminal is provided, the first and second oscillation PNP transistors are connected to the first and second N
Push-pull type DC-D controlled by PN transistor
With an electronic flash device having a C converter, it is possible to perform oscillating operation without dividing the feedback winding. By reducing the number of oscillation transformer terminals and downsizing, the circuit scale is reduced and the component cost is reduced. Can be planned.

According to the invention described in claim 3, a transformer having a power supply and two divided primary windings and a feedback winding, two oscillating PNP transistors for switching operation for boosting the power supply voltage, and each oscillation. Push-pull DC having FET for controlling operation of PNP transistor
In a DC converter circuit, a first oscillation PNP transistor, a first oscillation control FET that controls the base of the first oscillation transistor, and a first diode that connects a cathode to a source of the first FET and are connected in parallel to a battery. Of the second PNP transistor for oscillation, a second FET for oscillation control for controlling the base of the second oscillation PNP transistor, and a second diode for connecting the cathode to the source thereof and the second diode connected in parallel to the battery. Oscillation control circuit and one end of the second FET
A feedback winding connected to the source of the first FET and the other end thereof connected to the source of the first FET to be shared, and a feedback circuit including first and second resistors connected in parallel to the first and second diodes, respectively. , The anodes of the third and fourth diodes are connected from the sources of the first and second FETs, and the cathodes thereof are connected to one side of the secondary winding of the transformer and one side of the other side of the secondary winding of the transformer. One oscillation control for connecting the anodes of the fifth and sixth diodes from the other end and connecting the cathodes to the common rectifier circuit and each gate of the first and second FETs for one-terminal control Since it has a terminal,
The second oscillation PNP transistor is used as the first and second FETs.
In an electronic flash device having a push-pull type DC-DC converter controlled by the circuit, it becomes possible to perform an oscillating operation without dividing the feedback winding, and the number of terminals of the oscillating transformer is reduced to reduce the circuit size. It is possible to reduce the scale and cost of parts.

[Brief description of 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 the 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 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 circuit block diagram of a conventional electronic flash device.

FIG. 7 is a circuit block diagram of an electronic flash device using a conventional FET.

FIG. 8 is an explanatory diagram of an operation of a conventional electronic flash device.

FIG. 9 is a circuit block diagram of a conventional DC-DC converter.

[Explanation of symbols]

1 Battery 2, 4, 11, 90, 160 Capacitor 3 First Oscillating PNP Transistor 5, 7, 12, 14, 18, 18, 28, 31, 70, 140
Resistor 6 First NPN transistor 8, 9, 15, 16 Diode 10 Second oscillation PNP 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

Claims (3)

[Claims] 1. A transformer having a power supply and two divided primary windings and a feedback winding, two oscillation PNP transistors that perform a switch operation for boosting the power supply voltage, and the operation of each oscillation PNP transistor. In a push-pull type DC-DC converter circuit having a switch element for controlling, a first oscillation PNP transistor and a first oscillation PNP are provided.
A first oscillation control circuit configured by a first switching element for controlling oscillation of a base of a transistor and a first diode connecting a cathode to the first switching element and connected in parallel to a battery; The second oscillation PNP transistor and the second oscillation PNP transistor for controlling the bases of the second oscillation PNP transistor and the second diode for connecting the cathode to the second switching element are connected to the battery. A second oscillation control circuit connected in parallel, a feedback winding which has one end connected to one end of the second switch element and the other end connected to one end of the first switch element, and the first and second feedback control circuits. A feedback circuit including first and second resistors connected in parallel to a second diode;
And the anodes of the third and fourth diodes are connected to one end of the second switching element, the anodes of the fifth and sixth diodes are connected to one and the other ends of the secondary winding of the transformer, and the cathodes of the respective diodes are connected. An electronic flash device comprising: a common rectifier circuit; and 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. . 2. A transformer having a power supply and two divided primary windings and a feedback winding, two oscillation PNP transistors that perform switching operations for boosting the power supply voltage, and the operation of each oscillation PNP transistor. In a push-pull DC-DC converter circuit having an NPN oscillation control transistor, a first oscillation PNP transistor and a first oscillation PNP are provided.
A first N for controlling oscillation that controls the base of the transistor
A first oscillation control circuit configured by a PN transistor and a first diode having a cathode connected to the emitter of the first NPN transistor and connected in parallel to a battery; a second oscillation PNP transistor and a second oscillation; Oscillation Controlled Second Oscillation Controlling Base of PNP Transistor and Second Oscillation Controlled by Second Diode Connecting Cathode to Emitter of Second NPN Transistor A control circuit, a feedback winding having one end connected to the emitter of the second NPN transistor and the other end connected to the emitter of the first NPN transistor, and shared in common with the first and second diodes, respectively. A feedback circuit including first and second resistors connected to each other and a third to third emitter circuit of the first and second NPN transistors. And the anodes of the fourth diode are connected, and the respective cathodes are connected to one and the other end of the secondary winding of the transformer, and fifth and sixth diodes are connected from one and the other end of the secondary winding of the transformer. Rectifier circuit in which the anodes of the first and second NPN transistors are connected in common and the anodes of the seventh and eighth diodes connected to the respective bases of the first and second NPN transistors are controlled by a common terminal. The electronic flash device is provided with one oscillation control terminal that starts oscillation by supplying the current and stops oscillation by stopping the current supply. 3. A power supply and a transformer having two split primary windings and a feedback winding, two oscillation PNP transistors that are switched to boost the power supply voltage, and the operation of each oscillation PNP transistor. In a push-pull type DC-DC converter circuit having an FET, a first oscillation PNP transistor and a first oscillation PNP are provided.
The first F for controlling oscillation that controls the base of the transistor
First connecting the cathode to the source of ET and the first FET
First diode connected in parallel to the battery
Oscillation control circuit, a second oscillation PNP transistor, a second FET for oscillation control for controlling the base of the second oscillation PNP transistor, and a second diode for connecting the cathode to the source of the second FET. A second oscillation control circuit configured in parallel with the battery, and a feedback winding shared by connecting one end to the source of the second FET and the other end to the source of the first FET. And a feedback circuit including first and second resistors connected in parallel to the first and second diodes, respectively, and the first and second FEs.
The anodes of the third and fourth diodes are connected from the source of T, and the cathodes of the third and fourth diodes are connected to one and the other ends of the secondary winding of the transformer, respectively, and the Oscillation by connecting the anodes of the 5th and 6th diodes and connecting their respective cathodes to a common rectifier circuit, and by connecting them to the respective gates of the 1st and 2nd FETs and turning them on by common one-terminal control. An electronic flash device, comprising one oscillation control terminal for stopping oscillation by starting and turning off.