JP2002023228A - Strobe device and camera having strobe device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high recharging efficiency, without imparing sense of operating a stroboscope device. SOLUTION: A camera control circuit 125 sets (S32) a switching time t1 for the timing of the switching from a first boosting circuit to a second control state, based on the condition of a power supply battery 1 (an open voltage E0 of the battery 1 and an internal resistor Rbat), so that the recharging completion time that is required for the recharging voltage of a main capacitor 18 becomes a recharging completion voltage (a prescribed voltage required for stroboscopic light emission), becomes approximately constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a strobe device and a camera having the same.

[0002]

2. Description of the Related Art Along with miniaturization of a camera, in a camera having a zoom function, a lens on a long focal length side becomes dark, and photographing depending on a strobe device has increased. In addition, the battery used has been reduced in power supply voltage from, for example, the use of two lithium batteries to the use of one lithium battery in terms of portability, and smaller batteries have been employed. In a situation where a small battery has a small electric capacity and a lens is dark on the long focal length side, and thus is highly dependent on a strobe device, a more efficient and easy-to-use strobe device is required.

[0003]

However, the charging of the strobe generally has a tendency that the efficiency of the booster circuit decreases when the charging speed is increased, and the charging time decreases when the efficiency is increased.

[0004] It is an object of the present invention to provide a strobe device with good charging efficiency and a camera having the same without impairing the operational feeling.

[0005]

In order to achieve this object, a strobe device according to a first aspect of the present invention charges a main capacitor by oscillating a booster circuit to boost the voltage of a power supply battery. , A first booster circuit, a second booster circuit that is different from the first booster circuit,
A control circuit for switching from the first booster circuit to the second booster circuit to charge the main capacitor, and the control circuit sets the switching timing according to the state of the power supply battery.

Alternatively, in a strobe device according to a second aspect of the present invention, a boosting circuit oscillates to boost the voltage of a power supply battery, thereby charging a main capacitor. A control circuit that switches the driving operation to a second driving operation that is faster in charging than the first driving operation and charges the main capacitor. The control circuit adjusts the switching timing according to the state of the power supply battery. Set.

Thus, if the control circuit sets the switching timing so that the charging completion time required for changing the charging voltage of the main capacitor to the charging completion voltage becomes substantially constant, the operation feeling of the camera having the strobe device is improved. Does not impair. Further, according to this configuration, the charging efficiency can be improved as compared with the conventional configuration.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIGS. 1 to 4 show the structure and operation of a camera having a flash device according to a first embodiment. FIG. 1 is a circuit diagram showing a configuration of a strobe device according to a first embodiment, FIG. 2 is a block diagram showing a configuration of a camera having a strobe device, FIG. 3 is a flowchart showing a flow of operation of the camera, and FIG. 4 is a flowchart showing a flow of a flash mode shown in FIG.

First, the configuration of the flash device 20 will be described with reference to FIG.

1 is a power supply battery, 2 is a switch element, 3 is a resistor connected as a pull-down resistor of a control terminal of the switch element 2, 4 is an oscillation transformer, 5 is a capacitor, 6
Is a resistor, 7 is an oscillation transistor in which a capacitor 5 and a resistor 6 are connected in parallel between a base and an emitter, 8 is a switch element, 9 is a resistor connected as a pull-down resistor of a control terminal of the switch element 8, and 10 is a battery 1 1 is connected between the negative electrode of FIG. 1 and the switch element 8 with the polarity shown in FIG.

An oscillation transformer 11 has one end of the primary winding P connected to the collector of the oscillation transistor 7 and the other end connected to the negative electrode of the battery 1. The connection point between the secondary winding S and the feedback winding F of the oscillation transformer 11 is connected to the source electrode of the switch element 8. 1
Reference numeral 2 denotes a resistor connected for current limitation of the feedback winding F of the oscillation transformer 11.

Reference numeral 13 denotes a high-voltage rectifier diode connected between the secondary output terminal S of the oscillation transformer 4 and a main capacitor 18 (described later). Reference numeral 14 denotes a high-voltage rectifier diode connected between the secondary output terminal S of the oscillation transformer 11 and a main capacitor 18 (described later).

Reference numeral 15 denotes a voltage detection circuit, 16 denotes a trigger circuit, 17 denotes a discharge tube, 18 denotes a main capacitor, and 125 denotes a camera control circuit (described in detail later). The voltage detection circuit 15 is connected in parallel to the main capacitor 18 to detect the voltage of the main capacitor 18. The trigger circuit 16
As will be described later, a signal for causing the discharge tube 17 to emit strobe light is output to a trigger electrode of the discharge tube 17. Discharge tube 1
7 is connected in parallel with the main capacitor 18 like the voltage detection circuit 15.

Reference numerals a to e denote connection lines connecting the flash device 20 and the camera control circuit 125, respectively. The connection line a is connected to the control electrode of the switch element 2, and the connection line b is connected to the control electrode of the switch element 8.

The connection line c is a line for outputting a voltage detection drive signal from the camera control circuit 125 to the voltage detection circuit 15, and this signal is transmitted from the voltage detection circuit 15 to the camera control circuit 125 via the connection line d. By being input, the charging voltage of the main capacitor 18 is detected. The connection line e is used when the camera control circuit 125 provides a light emission activation for operating the trigger circuit 16 for causing the discharge tube 17 to emit light.

Next, the configuration of a camera having the above-described strobe device 20 will be described with reference to FIG.

Reference numeral 125 denotes a camera control circuit (shown by a broken line) having an I / O control, an A / D converter, a multiplexer, and a microcomputer (hereinafter, referred to as a "microcomputer"). Reference numeral 120 denotes a constant voltage circuit which is controlled by the camera control circuit 125 via the VCCEN terminal and supplies Vcc which is a power supply of each circuit.

Reference numeral 121 denotes a switch detection circuit which is operated by the power supply battery 1 or Vcc power supply and transmits the state or change of each switch to a camera control circuit 125; 122, a temperature detection circuit; 123, information such as film sensitivity and the number of frames. , 124 is a battery check circuit, 126 is a shutter drive circuit for driving a shutter, and 127 is a distance measurement circuit.

A photometric circuit 128 transmits necessary information to the camera control circuit 125 via each terminal.
A display circuit for displaying necessary information on a CD or the like;
Reference numeral 30 denotes a lens driving circuit for driving a lens, 131
Is a film drive circuit for feeding the film, and drives the film under the control of the camera control circuit 125 via a FILMD terminal.

Next, the operation of the camera will be described with reference to FIG.

Here, it is assumed that the power supply of the camera control circuit 125 is already turned on, and in this state, the microcomputer of the camera control circuit 125 is in the low power consumption mode and the operation is stopped.

First, when the power switch in the switch detection circuit 121 is turned on, the camera control circuit 125 starts operating. Next, the camera control circuit 125
By applying a signal to the circuit 20 via the VCCEN terminal, the low voltage block 120 supplies the power supply Vcc to each circuit.

Next, initialization required for the microcomputer of the camera control circuit 125 is performed (S1). Next, the camera control circuit 125 uses the information of the switch detection circuit 121 to
Information necessary for photographing is confirmed (S2). Here, the camera control circuit 125 waits for the switch detection circuit 121 to output the first stroke signal indicating that the release button for preparing for photographing is half-pressed (S3).

When the first stroke signal is not generated,
Return to S2. Alternatively, when the first stroke signal is generated, the camera control circuit 125 sets a predetermined counter to an initial state (S4) and performs a battery check.
(S5), it is determined whether the camera is in a power supply state necessary for photographing (S6).

If the battery is not sufficient, the process returns to S2. Alternatively, if the battery is sufficient, the camera control circuit 125 sends the signal to the distance measuring circuit 12 via the terminal AFEN.
A signal is given to the camera 7 and operated to measure the distance to the subject (S7). The distance measuring circuit 127 gives distance measuring information to the camera control circuit 125 via the AFD terminal.

Next, the camera control circuit 125 sets the AEEN
A signal is supplied to the photometric circuit 128 via the terminal and the signal is actuated to measure the luminance of the subject (S8). Photometric circuit 1
28 gives the luminance information to the camera control circuit 125 via the terminal AED. The camera control circuit 125 determines whether the subject brightness is higher or lower than the predetermined brightness based on the brightness information (S9). If the luminance is higher than the predetermined luminance, S12
Proceed to (described later). Alternatively, if the luminance is lower than the predetermined luminance, the process proceeds to the flash mode (S10).

Here, the operation of the flash mode S10 will be described with reference to FIG.

First, the camera control circuit 125 obtains the open-circuit voltage E0 of the battery 1 and the battery voltage E1 by flowing the constant current I0 (S30). Then, the camera control circuit 125 obtains the internal resistance Rbat of the battery by the following equation: Rbat = (E0−E1) / I0 (1), and determines the state of the battery 1 (S31). The internal resistance Rbat includes a contact resistance of a battery contact piece or the like.

Next, the camera control circuit 125 charges the charging voltage of the main capacitor 18 based on the state of the power battery 1 (the open voltage E0 of the battery 1 and the internal resistance Rbat obtained by the above equation (1)). The switching timing for switching from the first booster circuit to the second booster circuit is set such that the heavy-current completion time required until the completion voltage (a predetermined voltage required for strobe light emission) becomes substantially constant.

Here, the first booster circuit is a flyback booster circuit, and the second booster circuit is a forward booster circuit. Further, the camera control circuit 125 sets the switching timing based on the charging time of the main capacitor 18 (S32). The charging time of the main capacitor 18 at the time of switching is referred to as switching time.

Next, a charging prohibition timer (a timer for stopping charging when the charging time becomes long) is set to a time of, for example, about 10 to 15 seconds and started (S3).
3) to control the flyback type booster circuit (S3
4).

Here, a control method of the flyback type booster circuit will be described with reference to FIG.

First, the camera control circuit 125 supplies a predetermined oscillation signal (high-level and low-level repetition signals) to the control electrode of the switch element 2 via the connection terminal a. When the control electrode of the switch element 2 becomes high level,
The switch element 2 conducts, and a current flows from the battery 1 to the primary winding P of the oscillation transformer 4.

As a result, an induced electromotive force is generated in the secondary winding S of the oscillation transformer 4, but the polarity of this current is such that it is blocked with respect to the high-voltage rectifier diode 13. In this case, no excitation current flows and energy is stored in the oscillation transformer 4.

Next, when the control electrode of the switch element 2 becomes low level, the switch element 2 becomes non-conductive, and a back electromotive force is generated in the secondary winding of the oscillation transformer 4. The rectifier diode 13 and the main capacitor 18 are generated by the back electromotive force.
And charge is accumulated in the main capacitor 18.

When a high-level signal is generated again from the terminal a at the time when the energy in the oscillation transformer 4 is released, the switching element 2 is turned on again to accumulate energy in the oscillation transformer 4 in the same manner. As a result, the oscillation element 2 becomes non-conductive, the energy stored in the oscillation transformer 4 is released, and the electric charge is charged in the main capacitor 18.
By repeating this operation, the voltage of the main capacitor 18 increases.

During this time, the camera control circuit 125 supplies a drive signal to the voltage detection circuit 15 via the connection line c as described above. Upon receiving the drive signal, the voltage detection circuit 15 measures the charging voltage between the main capacitors 18 and
The signal is output to the camera control circuit 125 via the connection line d. The camera control circuit 125 detects this charging voltage by the A / D converter, and checks whether or not this charging voltage has reached a predetermined charging completion voltage (S35). If the charging voltage has reached the predetermined charging completion voltage, a charging OK flag is set (S40), and the process proceeds to S41 described later.

If the charging voltage has not reached the predetermined charging completion voltage, it is checked whether the charging time has reached the above-mentioned switching time (S36). If the charging time has not reached the switching time, the process proceeds to S38 described later. When the charging time has reached the switching time, the camera control circuit 125 switches from the flyback type boosting circuit to the forward type boosting circuit.

In the forward step-up circuit, first, the camera control circuit 125 stops the output of the oscillation signal flowing to the oscillation switch 1 via the connection line a, and turns off the switch element 2. Next, the camera control circuit 125
A high-level signal is given to the control electrode of the switch element 8 via the connection line b (S37). The switch element 8 is
When a high-level signal is input, it becomes conductive.

When the switch element 8 conducts, the base of the oscillation transistor 7 = emitter, the switch element 8, and the feedback winding F of the oscillation transformer 11 are applied from the positive electrode of the battery 1.
In addition, a base current of the oscillation transistor 7 flows through the resistor 12. Thereby, the collector current of hfe times flows through the primary winding P of the oscillation transformer 11 in the negative loop of the battery 1.

Therefore, the secondary winding S of the oscillation transformer 11
, An induced electromotive force is generated, thereby causing a current to flow through a loop of the high-voltage rectifier diode 14, the main capacitor 18, the battery 1, the base = emitter of the oscillation transistor 7, the switch element 8, and the secondary winding of the oscillation transformer 11. The main capacitor 18 is charged, but at the same time, it becomes the base current of the oscillation transistor 7, so that the base current increases and returns, so that positive feedback is applied. State.

When a current flows for a while, the magnetic flux in the core of the oscillation transformer 11 saturates, a back electromotive force is generated in the oscillation transformer 11, and the back electromotive force generated in the secondary winding of the oscillation transformer 11 is generated. Is a switch element 8, an oscillation transistor 7
A base reverse bias is applied to the oscillation transistor 7 through a loop of the parasitic capacitance of the battery 1, the main capacitor 18, and the high-voltage rectifier diode 14 between the base and the emitter. With this,
The back electromotive force of the feedback winding F is also the switching element 8, the base of the oscillation transistor 7 = emitter, the battery 1, the resistor 1
Since a base reverse bias is applied to the oscillation transistor 7 in the loop 2, the oscillation transistor 7 suddenly becomes non-conductive.

When the magnetic flux saturation in the core of the oscillation transformer 11 is eliminated, the base current of the oscillation transistor 7 flows again, and the oscillation transistor 7 repeats conduction / non-conduction by the same operation to charge the main capacitor 18. As a result, the charging voltage of the main capacitor 18 increases.

Next, the camera control circuit 125 determines whether or not a charge prohibition timer for prohibiting charging when the charging time is delayed has counted up (S3).
8). When the charging prohibition timer has not counted up, the control state is maintained and the process returns to S35.

If the charging prohibition timer has counted up, the camera control circuit 125 sets a charging NG flag (S39) and outputs the oscillation signal output to the switch element 2 via the connection line a, or The oscillation signal output to the switch element 8 via the connection line b is stopped. The oscillation signal output to the switch element 2 via the connection line a (or the switch element 8 via the connection line b as described later) is stopped.

As a result, the switch element 2 or the switch element 8 becomes non-conductive, and charging stops (S41).
Thus, the flash mode (S10) ends,
Returning to the flowchart of FIG.

Next, the camera controller 125 checks the flags of S40 and S39 shown in FIG. 4 (S11),
If the flag is an NG flag, the process returns to S2. If the flag is an OK flag, the camera controller 125 determines whether the first stroke signal is output from the switch detection circuit 121 (S12).

Here, when the first stroke signal has not been input, the camera controller 125 returns to S2,
If a stroke signal is being input, it is determined whether or not a second stroke signal (a signal when the release button is fully pressed) is being output from the switch detection circuit 121 (S13).

Here, the camera controller 125 returns to S12 when the second stroke signal has not been inputted, and when the second stroke signal has been inputted, the lens driving circuit based on the distance measurement data in S7. 129 is controlled to perform focus adjustment (S14).

Next, the camera control unit 125 controls the shutter opening via the shutter drive circuit 124 according to the conditions based on the brightness of the subject and the film sensitivity data obtained in S8, and also requires a low-brightness strobe device. In this case, the shutter is controlled based on the distance measurement data and the film sensitivity, and the flash device emits light with the appropriate aperture value.
S15).

Light emission of the strobe device is performed by giving a high level signal to the connection line e. The camera controller 125 outputs a high-level signal via the connection line e to the trigger circuit 16.
, The trigger circuit 16 generates a high-level pulse voltage and outputs it to the trigger electrode of the discharge tube 1217.

The discharge tube 1217 is excited when a high-voltage pulse voltage is input. The excitation causes the impedance of the discharge tube 1217 to drop at once, discharges the charging energy of the main capacitor 1318, converts it into light energy, and illuminates the subject. When a strobe device is used, the flash flag FAL is set to 1.

Next, when the shutter is closed, the control device 125 returns the lens at the focal position to the initial position (S16), and controls the film drive circuit 131 for one frame of the film on which photography has been completed. Wind up by minutes (S17).

Next, it is confirmed whether or not "1" is set in the flash flag indicating that the flash device has been used (see FIG. 4).
S18). Here, when the flag "1" is set, the flash mode is set, and the main capacitor 18 is set in the same manner as in S10.
Is performed (S19), and a series of sequences is terminated. When the strobe device is not used, S1
After passing through step S9, the process returns to step S2 to end the sequence.

Next, the charging voltage characteristic of the flash device of the first embodiment will be described with reference to FIG. FIG. 5 (a) is a charging voltage curve of a relatively new battery, FIG. 5 (b) is a charging voltage curve of a relatively depleted battery, L1 is a case where only a forward booster circuit is used, and L2 is a flywheel. When only the buck type booster circuit is used, L3 indicates a charging voltage curve according to the present invention. The vertical axis indicates the charging voltage (VCM) of the main capacitor 18, and the horizontal axis indicates the charging time.

In the first embodiment, charging is initially started by the flyback type booster circuit, and is switched to the forward type booster circuit at time t1. At time 0, charging is performed along L2, and at the charging time t1, the charging control state is switched (flyback booster circuit → forward booster circuit), and along L3, which is a charging curve obtained by shifting L1 in the time axis direction. Charging is performed. Thereafter, when the charging voltage rises and reaches the charging completion voltage Vs top, charging stops at the charging time t2.

As is apparent from a comparison between FIGS. 5A and 5B, by changing the switching time t1 between a relatively new battery and a depleted battery, the charging completion voltage Vst is changed.
The time t2 at which op is set is set to be substantially equal.

As described above, the camera control circuit 125 switches from the flyback type booster circuit to the forward type booster circuit at the switching time t1 in accordance with the consumption state of the power supply battery 1 and charges the main capacitor 18, thereby charging. Since the completion time t2 is substantially constant irrespective of the state of consumption of the power supply battery, the usability of the camera having this strobe device is improved.

Next, a method of setting the switching time t1 will be described.

First, the charging characteristics of the flyback booster circuit will be described.

The charge completion time t1 of the forward booster circuit
Is generally qualitatively determined by the following equation (2).

T1 = −α × Cm × (RL + Rbat) × n ² × Ln {1-Vs top / (n × E 0)} (2) where α is the on / off of the oscillation element by the oscillation transformer. / Of
f is a coefficient including a duty, etc., Cm is a main capacitor capacitance, RL is a loop resistance of a charging circuit such as a wiring resistance, n is a primary / secondary winding ratio of an oscillating transformer, and Vstop is a charge completion voltage. It is a known fixed value.

Therefore, the battery open voltage E0, the internal resistance Rb
By measuring at, the completion time of the power-supply of the forward booster circuit can be found from the above equation (2). If a matrix table of the switching time t1 corresponding to the charging completion time t1 is previously installed in the memory of the camera control circuit 125, the camera control circuit 125 determines the switching time t1 using the matrix table. Can be.

For example, the camera control circuit 125 sets the charging completion time t1 when only the forward booster circuit is used.
Is qualitatively determined by the following equation (4).

Alternatively, according to the following equation (3), the camera control circuit 125 determines the current flowing through the oscillation transformer 4 when a predetermined time Ton has elapsed since the switch element was turned on.
Ask for I.

I = E0 / (RL + Rbat) × [1-Exp {-Ton × (RL + Rbat) / L}] (3) where L is the primary inductance of the oscillation transformer 4 and R
L is a loop resistance of a charging circuit such as a wiring resistance.

Next, the camera control circuit 125 calculates the emission energy Q (electric energy charged in the main capacitor 18 by one discharge) by the following equation (4).

[0068] By only being charged emitted energy Q min to ^{Q = L × I 2/2} ··· (4) the main capacitor 18, the charging voltage is gradually increased. Then, the released energy Q, the charging time and the switching time t1
Is stored in the memory of the camera control circuit 125, and the camera control circuit 125 can determine the switching time t1 using this matrix table.

Next, the efficiency η of the strobe device is shown in FIG.
This will be described with reference to FIG. FIGS. 6A and 6B are charging efficiency curves (real time) of the strobe device, in which the vertical axis indicates the efficiency η and the horizontal axis indicates the charging voltage. η1 is a charging efficiency curve when only the forward booster circuit is used, and η2 is a charging efficiency curve when only the flyback booster circuit is used. The thick curve in FIG. 6B is the charging efficiency curve according to the present invention. FIG. 6C shows a charging time curve similarly to FIG. 5, and the charging time on the horizontal axis is shown in FIG.
It corresponds to the charging voltage on the horizontal axis in (a) and (b).
In FIG. 6, the stop is not performed so that the efficiency and charging curves can be easily seen.

As shown in FIG. 6 (a), in the case of the forward booster circuit, a large current flows at the beginning of charging.
The efficiency η1 at the beginning of charging is not high. On the other hand, in the case of the flyback type booster circuit, the current is almost constant, so that the efficiency η2 has a relatively stable flat value.
When the charging voltage increases, the efficiency η1 becomes higher than the efficiency η2.

In the strobe device of the present invention, FIG.
As shown in the graph, charging is performed along a curve (thick solid line) along the efficiency η2 from time 0 to time t1, and the switching time t1
And the charge completion voltage Vs as a curve (thick solid line) along the efficiency η1
Charging is performed until the charge reaches top, and along the portion of the two efficiency curves η1 and η2 where the charging efficiency is high, the charging efficiency of the strobe device of the present invention is high.

(Second Embodiment) FIG. 7 is a circuit diagram showing a configuration of a strobe device according to a second embodiment. The booster of the second embodiment includes a flyback type booster circuit, and switches from the first control state to the second control state by changing a fixed frequency given to the oscillation transformer 4.
This point is different from the first embodiment.

As shown in FIG. 7, the strobe device of the second embodiment has a configuration in which the forward booster circuit is removed from the strobe device of the first embodiment. The first
The same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment.

Next, the charging voltage characteristic of the strobe device of the second embodiment will be described with reference to FIG.

FIG. 8 (a) shows a charging voltage curve of a relatively new battery, and FIG. 8 (b) shows a charging voltage curve of a relatively consumed battery. L1 indicates the duty ratio of ON / OFF of the oscillation signal. When large, L2 indicates a charging voltage curve according to the present invention when the on / off duty ratio of the oscillation signal is small. The vertical axis represents the charging voltage of the main capacitor 18 (VC
M), the horizontal axis shows the charging time.

When the on / off duty ratio of the oscillation signal is large (L1), the primary current of the oscillation transformer 4 is large, so that the charging speed is also large. On the other hand, when the on / off duty ratio of the oscillation signal is small (L2), the charging current is small because the primary current of the oscillation transformer 4 is small.

In the second embodiment, charging is performed along the curve L2 when the on / off duty ratio of the oscillation signal is small from the start of charging to the switching time t1, and the power receiving completion time t2 (from the switching time t1). At this time, until the switching charge voltage Vstop) is reached, charging is performed along the curve L1 when the on / off duty ratio of the oscillation signal is large. As shown in FIGS. 8A and 8B, by changing the switching time t1, the heavy electric power completion time t2 is substantially constant irrespective of the consumption state of the power battery 1, so that the first embodiment Similar to the embodiment, the usability of the camera having the strobe device is improved.

The method for setting the switching time t1 is the same as that in the first embodiment, and a description thereof will be omitted.

Next, the efficiency η of the strobe device is shown in FIG.
This will be described with reference to FIG. FIGS. 9A and 9B are charging efficiency curves (real time) of the strobe device, in which the vertical axis indicates the efficiency η and the horizontal axis indicates the charging voltage. η1 is a charging efficiency curve when the oscillation frequency is low, and η2 is a charging efficiency curve when the oscillation frequency is high. The thick curve in FIG. 9B is the charging efficiency curve in the present invention.
FIG. 9C shows a charging time curve similarly to FIG.
The charging time on the horizontal axis corresponds to the charging voltage on the horizontal axis in FIGS. 9 (a) and 9 (b). Note that FIG. 9 shows that the stop is not performed so that the efficiency and charging curves are easy to see.

When the camera is new, the efficiency η is high.
It can be seen that the charging time along the curve of No. 1 is long, and as the camera wears out, the charging time along the low efficiency η2 curve becomes longer. As described above, when the camera is new, charging is performed at the efficiency η1, and the charging efficiency is accordingly increased.

The present invention is not limited to the above-described embodiment, and various changes can be made in accordance with the design.

For example, in the above embodiment, the internal resistance Rbat of the battery is obtained by the above equation (1).
The internal resistance Rbat of the battery may be obtained by the following equation (3).

Rbat = R0 × (1−E0 / E2) (5) Here, E2 is a battery voltage when a known resistor R0 is temporarily connected between the power lines of the battery 1.

In the above embodiment, the switching timing is set by the switching time t1.
Switching charging voltage V1 corresponding to this switching time t1
May be set.

In the above-described second embodiment, the frequency of the oscillation signal is switched using the flyback type booster circuit. However, the frequency of the oscillation signal is switched using the forward type booster circuit. good.

Further, in the above-described second embodiment, S in FIG.
Open battery voltage E0 and battery resistance R by 30 battery checks
bat is detected, but instead of this, S in FIG.
Open battery voltage E0 and battery resistance Rb by battery check of 5
at may be detected. In this case, S30 may be deleted.

Further, the strobe device of the present invention can be applied to a digital camera, an optical signal generator for optical communication, and the like.

[0088]

As is apparent from the above description, according to the strobe device of the present invention and the camera having the same,
If the switching timing is set so that the charge completion time required for the control circuit to change the charge voltage of the main capacitor to the charge completion voltage is substantially constant, the operational feeling of the camera having the strobe device is not impaired. Further, according to this configuration, the charging efficiency can be improved as compared with the conventional configuration.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a flash device according to a first embodiment.

FIG. 2 is a block diagram illustrating a configuration of a camera having a strobe device.

FIG. 3 is a flowchart showing a flow of an operation of the camera.

FIG. 4 is a flowchart showing a flow of a flash mode.

FIG. 5 is a graph showing a charging voltage according to the first embodiment.

FIG. 6 is a graph showing the efficiency of the first embodiment.

FIG. 7 is a circuit diagram illustrating a configuration of a strobe device according to a second embodiment.

FIG. 8 is a graph showing a charging voltage according to the second embodiment.

FIG. 9 is a graph showing the efficiency of the second embodiment.

[Explanation of symbols]

 1: Power supply battery 2, 8: Switch element 3, 6, 9, 12: Resistance 4, 11: Oscillation transformer 5: Capacitor 7: Oscillation transistor 10: Diode 13, 14: High voltage rectification diode 15: Voltage detection circuit 16: Trigger Circuit 17: Discharge tube 18: Main capacitor 120: Constant voltage circuit 121: Switch detection circuit 122: Temperature detection circuit 123: Film sensitivity detection circuit 124: Battery check circuit 125: Camera control circuit 126: Shutter drive circuit 127: Distance measurement circuit 128: photometric circuit 129: display circuit 130: lens drive circuit 131: film drive circuit ae: connection line

Claims (10)

[Claims] 1. A strobe device for charging a main capacitor by oscillating a booster circuit to boost a voltage of a power supply battery, comprising: a first booster circuit; and a second booster circuit different in system from the first booster circuit.
A booster circuit, and a control circuit for switching the first booster circuit to the second booster circuit and charging the main capacitor, wherein the control circuit performs the switching timing according to a state of the power supply battery. Strobe device characterized by setting. 2. A strobe device for charging a main capacitor by oscillating a booster circuit to boost a voltage of a power supply battery, wherein the drive operation of the booster circuit is changed from the first drive operation to the first drive operation. A control circuit for charging the main capacitor by switching to a second drive operation that is faster in charge than the drive operation, wherein the control circuit sets the switching timing in accordance with a state of the power supply battery. Characteristic strobe device. 3. The flash device according to claim 1, wherein the first booster circuit is a flyback booster circuit, and the second booster circuit is a forward booster circuit. 4. The flash device according to claim 2, wherein the booster circuit is a flyback type booster circuit. 5. The strobe device according to claim 2, wherein the booster circuit is a forward booster circuit. 6. The flash device according to claim 1, wherein the control circuit sets the switching timing according to a state of an internal resistance of the power supply battery. 7. The flash device according to claim 1, wherein the control circuit sets the switching timing based on a charging time of the main capacitor obtained from a state of the power supply battery. 8. The strobe device according to claim 1, wherein the control circuit sets the switching timing based on a charging voltage of the main capacitor obtained from a state of the power supply battery. 9. The switching circuit according to claim 1, wherein the control circuit sets the switching timing such that a charging completion time required for changing a charging voltage of the main capacitor to the charging completion voltage is substantially constant. Item 3. The strobe device according to item 1 or 2. 10. A camera comprising the strobe device according to claim 1.