JP2002315335A - Capacitor charger, light-emitting device and camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of long charging time of a main capacitor in charging by a conventional flyback-type charging circuit, in comparison to charging by the so-called forward-type charging circuit. SOLUTION: This is a capacitor charger provided with a flyback-type charging circuit for charging a main capacitor 109, and has a voltage-increasing capacitor 126 in a circuit for applying voltage to the primary side of a transformer 106 for forming the charging circuit, and a control means 105 for applying a second voltage higher than a first voltage utilizing charge stored in the voltage-increasing capacitor to the primary side of the transformer, after a first voltage has been applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for a main capacitor for storing electric energy used for strobe light emission of a camera, and more particularly to a capacitor charging device using a flyback type charging circuit.

[0002]

2. Description of the Related Art First, an electric circuit of a camera having a conventional flyback type charging (boosting) circuit will be described with reference to FIG. Reference numeral 301 denotes a battery serving as a power supply;
1a is a battery internal resistance. A capacitor 324 is connected in parallel with the battery 301.

[0005] 302 is a shutter coil, and 303 is a transistor. This transistor 303 drives the shutter coil 102. Reference numeral 304 denotes a resistor for detecting a current when the shutter coil 302 is driven with constant current.

A control IC 305 controls a camera sequence such as photometry, distance measurement, lens driving, and film feeding of the camera, and controls a strobe device provided in the camera. 3
A microcomputer 05a in the control IC 305 has a built-in RAM and controls a camera sequence.

Reference numeral 305b denotes a constant current control circuit which controls the constant current drive of the shutter coil 302 via a transistor 303. 305c is a D / A converter (hereinafter, referred to as D / A converter)
Simply called D / A) and the microcomputer 30
An arbitrary voltage corresponding to the setting signal of 5a is output. 305
d is an A / D converter (hereinafter simply referred to as A / D),
Digitizes the input voltage.

Reference numeral 305e denotes a comparator which detects whether or not the current of the primary winding of the transformer 106 described later has reached a set current. A resistor 305f pulls up the output of the comparator 105e to Vcc boosted from the battery voltage by a power supply circuit (not shown). Transformer 306
In this device, energy is accumulated in a core by passing a current through a loop of the positive electrode of the battery 301, the primary winding, and the negative electrode of the battery 301, and a back electromotive force is generated on the secondary side by the energy.

Reference numeral 307 denotes an N-channel FET (field-effect transistor) for driving a current of the primary winding of the transformer 306. Reference numeral 309 denotes a main capacitor, which accumulates electric charges for causing a xenon tube 311 described later to emit light.

Reference numeral 308 denotes a high-voltage rectifier diode. The anode is connected to the winding end of the secondary winding of the transformer 306, and the cathode is connected to the anode of the main capacitor 309. A diode 320 has an anode connected to a cathode of the main capacitor 309, a cathode connected to a winding start end of a secondary winding of the transformer 306, and a back electromotive force generated from the secondary winding of the transformer 306 to the main capacitor 309. The current loop of the accumulated charge is connected to the high voltage rectifier diode 308.
Is formed.

321 is a resistor, one side of which is a diode 3
The other side is connected to the control IC 305 on the cathode of the control unit 20. Reference numeral 322 denotes a resistor, which pulls up the input of the control IC 305 to which the resistor 321 is connected to Vcc.

Reference numeral 310 denotes a trigger circuit, and reference numeral 311 denotes a xenon discharge tube. The xenon tube 311 receives the trigger voltage from the trigger circuit 310 and discharges the electric charge accumulated in the main capacitor 309 to emit light.

Reference numeral 312 denotes a charging voltage detecting circuit,
It is connected to the A / D 305 d in the C 305 and detects a voltage generated by the electric charge stored in the main capacitor 309.
A photometry circuit 313 detects the brightness of the subject. 31
Reference numeral 4 denotes a distance measurement circuit that detects a distance to a subject.

Reference numeral 315 denotes a lens driving circuit which drives a focusing lens (not shown) based on the detection result from the distance measuring circuit 314 to focus the object on the film surface. A film feeding circuit 316 drives a motor (not shown) that performs automatic loading, winding, and rewinding of the film.

Reference numeral 317 denotes an M for turning on the power of the camera.
An AINSW 318 is turned on by a first stroke operation (half-press operation) of a release button by a photographer, and is used to start a photographing preparation operation such as photometry and distance measurement.
It is one. 319 is the second release button by the photographer
SW2 which is turned on by a stroke operation (full-press operation) and generates a start signal of a photographing sequence after the photographing preparation operation such as a film exposure operation.

Here, the operation of the flyback type charging circuit will be described. First, the output timing and the like of each signal will be described with reference to the timing chart shown in FIG.

In FIG. 2B, a2 is an FET 307.
, And b2 indicates the battery voltage. e2
Indicates a current flowing through the secondary winding of the transformer 306, and f2
Indicates a current flowing through the primary winding of the transformer 306. g1
Is connected to the resistor 321 and the resistor 322 and is connected to the control IC 30
5 shows the detection signal of the secondary current connected to 5.

Next, the circuit operation will be described. First, the control IC
When a predetermined oscillating signal (timing of a2) is applied from the 305 to the gate of the FET 307 via the connection terminal, a high-level signal is applied to the control electrode of the FET 307, and the drain = source, the primary winding of the transformer 306, Current flows in the loop of the battery negative electrode.

As a result, an induced electromotive force is generated in the secondary winding of the transformer 306. Since the polarity of this current is such that it is blocked by the high-voltage rectifier diode 308, an exciting current flows from the transformer 306. Instead, energy is stored in the core in the transformer 306. This energy accumulation (energization drive) is performed until the comparator 305e detects that the current has reached the predetermined current (f2 timing).

When energization driving is performed to a predetermined current in this manner,
The gate of the FET 307 is set to a low level to
Is turned off (at the timing of a2) to cut off the current,
No conduction. As a result, a back electromotive force is generated in the secondary winding of the transformer 306. This back electromotive force is equal to the secondary current (e
2), the rectifier diode 30
8. The electric current flows through the loop of the main capacitor 309 and the diode 320, and the electric charge is accumulated in the main capacitor 309.

The energy in the transformer 306 is released, and the secondary current is shunted to a low level.
The signal of No. 2 is inverted from the low level to the high level when the secondary current is substantially stopped (at the timing of g2). In response to the inversion of the secondary input signal from the low level to the high level, the control IC 305 again generates a high level signal at the gate of the FET 307, and similarly, the FET3 again.
07 is turned on (at the timing of a2) and the transformer 3
At 06, energy is stored.

Further, the FET 307 is supplied by a low level signal.
Is turned off, the energy stored in the transformer 306 is released, and the main capacitor 309 is charged.

By repeating the above operation, the voltage of the main capacitor 39 increases. This charging circuit is generally called a flyback type charging circuit.

[0022]

However, in the above-mentioned conventional flyback type charging circuit, the charging time tends to be longer than that of a so-called forward type charging circuit, and the device such as a camera using the same is not easy to use. There is a problem of doing.

Accordingly, an object of the present invention is to provide a capacitor charging device capable of shortening the charging time of a main capacitor by a flyback type charging circuit.

[0024]

In order to achieve the above object, the present invention provides a capacitor charging apparatus having a flyback type charging circuit for charging a main capacitor. A voltage boosting capacitor is provided in a circuit for applying a voltage to the primary side, and after applying a first voltage to the primary side of the transformer, the charge stored in the voltage boosting capacitor is used to reduce the voltage from the first voltage. Control means for applying a high second voltage is provided.

As described above, when the boosting capacitor is included in the circuit for applying the voltage to the primary side of the transformer, the first voltage such as the power supply voltage is applied to the primary side of the transformer in the initial stage of charging. By applying a higher second voltage at an appropriate timing, the boosting effect of the booster capacitor can be reduced as compared with a conventional charging device or a charging device that applies a high second voltage from the beginning of charging. The main capacitor can be charged efficiently and in a short time.

Specifically, for example, when applying the first voltage to the primary side of the transformer, a booster capacitor is connected in parallel to the power supply, and when applying the second voltage to the primary side of the transformer. May be connected in series with a power supply capacitor.

The switching from the first voltage to the second voltage is performed, for example, by applying the first voltage until the current flowing to the primary side of the transformer reaches the first current value from the start of energization. After reaching the current value of 1, the second voltage may be applied until the current value reaches the second current value higher than the first current value. Alternatively, the switching from the first voltage to the second voltage is performed, for example, by applying the first voltage to the primary side of the transformer from the start of energization until the first predetermined time is reached, and after the elapse of the first predetermined time. The second voltage may be applied until the second predetermined time is reached.

By using this capacitor charging circuit in a light emitting device mounted on a camera or the like, it becomes possible to realize a convenient camera or the like having a short charging time for enabling light emission.

[0029]

(First Embodiment) FIG. 1 shows an electronic strobe device (light emitting device) according to a first embodiment of the present invention.
1 shows a circuit configuration of a camera including a camera. Note that the camera is configured as shown in FIG. 10, and 1 is a camera body. 2 is a lens barrel including a photographing lens, 3 is a viewfinder, 4 is a release button for turning on SW1 and SW2 at the time of photographing, 5 is a strobe light emitting unit which emits light at the time of strobe photographing, 6 is a photometric lens which detects subject brightness, 7 is a distance measurement for detecting a distance to a subject, 8 is display means for displaying camera information, and 9 is an MAI for setting the camera in a shooting preparation state.
It is composed of NSW buttons.

In FIG. 1, reference numeral 101 denotes a battery serving as a power supply, and 101a denotes an internal resistance of the battery 101.

Reference numeral 124 denotes a capacitor, which is connected in parallel with the battery 101. A diode 125 has an anode connected to the positive electrode of the battery 101 and a cathode connected to a transformer 106 described later.

Reference numeral 126 denotes a voltage-doubling (voltage-increasing) capacitor. One electrode is connected to the cathode of the diode 125 and the primary winding of the transformer 106.

Reference numeral 127 denotes a P-channel FET (field-effect transistor). The drain is connected to the other electrode of the voltage-doubling capacitor 126, the source is connected to the positive electrode of the battery 101, and
The gates are connected to the control IC 105, respectively.

A resistor 128 is connected between the gate and the source of the FET 127. Reference numeral 129 denotes an N-channel type FET. The drain is connected to the drain of the FET 128 and the voltage increasing capacitor 126, the source is connected to the negative electrode of the battery 101, and the gate is connected to the control IC 105.

A resistor 130 is connected between the gate and the source of the FET 129. Diode 125, doubler capacitor 126, FET 127, resistor 128, F
The ET 129 and the resistor 130 constitute a pseudo voltage doubler circuit that makes the voltage applied to the transformer 106 approximately twice the voltage of the battery 101.

Reference numeral 102 denotes a shutter coil;
Is a transistor. This transistor 103 drives a shutter coil (102). Reference numeral 104 denotes a resistor, which is provided to detect a current when the shutter coil 102 is driven with constant current.

Reference numeral 105 denotes a control IC, which is a photometer for a camera,
It controls a camera sequence such as distance measurement, lens driving, and film feeding, and a strobe device provided in the camera.

Reference numeral 105a denotes a microcomputer in the control IC 105, which has a built-in RAM and controls a camera sequence. Reference numeral 105b denotes a constant current control circuit, which controls the shutter coil 102 via the transistor 103 so as to drive the shutter coil 102 at a constant current.

Reference numeral 105c denotes a D / A, which outputs an arbitrary voltage according to a setting signal of the microcomputer 105a. A / D 105d digitizes the input voltage.

Reference numeral 105e denotes a comparator which detects whether or not the current of the primary winding of the transformer 106 described later has reached a set current. Reference numeral 105f denotes a resistor, which pulls up the output of the comparator 105e to Vcc boosted from the battery voltage by a power supply circuit (not shown).

Reference numeral 106 denotes a transformer, which is connected from the positive electrode of the battery 101 to a diode 125 or a voltage doubling capacitor 126.
, Energy is accumulated in the core by flowing a current through the loop of the primary winding and the negative electrode of the battery 101, and a back electromotive force is generated by the energy.

Reference numeral 107 denotes an N-channel type FET (field effect transistor), which drives a current of a primary winding of the transformer 106. A resistor 123 is connected to the FET 107 and the negative electrode of the battery 101, and serves as a detection resistor when detecting the current of the primary winding of the transformer 106.

Reference numeral 109 denotes a main capacitor, which accumulates electric charges for causing a xenon tube 111 described later to emit light.

Reference numeral 108 denotes a high-voltage rectifier diode. The anode is connected to the winding end of the secondary winding of the transformer 106, and the cathode is connected to the anode of the main capacitor 109.

Reference numeral 120 denotes a diode, the anode of which is the cathode of the main capacitor 109, and the cathode of which is the transformer 106.
It is connected to the winding end of the secondary winding. Transformer 1
A current loop that accumulates electric charge in the main capacitor 109 by the back electromotive force generated from the secondary winding 06 is formed including the high-voltage rectifier diode 108.

Reference numeral 121 denotes a resistor, one of which is a diode 1
The other side is connected to the control IC 105 at the cathode 20. Reference numeral 122 denotes a resistor, which pulls up the input of the control IC 105 to which the resistor 121 is connected by Vcc.

Reference numeral 110 denotes a trigger circuit, and reference numeral 111 denotes a xenon discharge tube, which is a strobe light emitting unit 5 of the camera shown in FIG.
It is assembled inside. Upon receiving a trigger voltage from the trigger circuit 110, the xenon tube 111 emits light by reporting and discharging the charge accumulated in the main capacitor 109.

Reference numeral 112 denotes a charging voltage detection circuit,
It is connected to A / D 105 d in C 105 and detects the voltage stored in main capacitor 109.

Reference numeral 113 denotes a photometric circuit, which detects the luminance of the object from the light received by the photometric lens 6 in FIG. 114
Is a distance measuring circuit, which detects the distance to the subject from the image received by the distance measuring lens 7 in FIG. Reference numeral 115 denotes a lens driving circuit which performs focusing driving of the photographing lens 2 in FIG. 10 based on a detection result from the distance measuring circuit 114, and focuses an object on a film surface. A film feeding circuit 116 drives a motor for performing automatic loading, winding and rewinding of the film.

Reference numeral 117 denotes a MAINSW for turning on the power of the camera which is turned on by the MAINSW button in FIG. 10. Reference numeral 118 denotes a MAINSW which is turned on by a first stroke operation (half-press operation) of the release button 4 in FIG. SW1 for starting a shooting preparation operation such as distance measurement. Reference numeral 119 denotes a switch SW2 which is turned on by a second stroke operation (full press operation) of the release button by the photographer, and generates a start signal of a photographing sequence after the photographing preparation operation such as a film exposure operation.

Next, the operation of the flyback type charging circuit will be described. First, the output timing and the like of each signal will be described with reference to the timing chart shown in FIG.

A1 indicates the gate input signal of the FET 107, and b1 indicates the voltage of the battery 101. Further, c1 indicates a gate input signal of the FET 130 on the circuit, and d1 indicates FE.
T1 indicates the gate input signal of T128.
6 shows the current flowing through the secondary winding, which is the current at the position of e1 on the circuit. Further, f1 is a current flowing through the primary winding of the transformer 106, and indicates a current at a position of f1 on the circuit. Further, g1 indicates a secondary current detection signal in which the resistors 121 and 122 are connected and connected to the control IC 105.

Next, the circuit operation will be described. Control IC
A predetermined oscillation signal (a1) is supplied from the microcomputer 105 (microcomputer 105a) to the gate of the FET 107 via the connection terminal.
Is applied, a high-level signal is applied to the control electrode of the FET 107, and a current flows through the drain = source, the primary winding of the transformer 106, and the negative loop of the battery 101. For this reason, an induced electromotive force is generated in the secondary winding of the transformer 106. However, since the polarity of this current is a polarity blocked by the high-voltage rectifying diode 108, no exciting current flows from the transformer 106, Is stored in the core in the transformer 106.

This energy storage (energization driving) is performed until the current flowing through the primary winding of the transformer 106 reaches the first predetermined current (timing f1).

Next, when the current flowing through the primary winding of the transformer 106 reaches the first predetermined current, the control IC 105 operates so that the voltage applied to the transformer 106 becomes about twice the voltage of the battery 101. The drive signal to the FET 128 is set to a low level signal (timings of b1 and d1),
The drive signal to the ET 129 is switched from high level to low level (timing of c1).

By controlling the driving of the FET 128 and the FET 129 in this manner, the voltage-doubling capacitor 126, which has been connected in parallel to the battery 101 and has accumulated the charge up to the voltage of the battery 101, is connected to the battery 101. Connect in series. This allows the transformer 106
A voltage approximately twice the voltage of the battery 101 is applied to the primary winding.

Therefore, the current flows through the primary winding of the transformer 106 more steeply until it reaches the second predetermined current than it does before it reaches the first predetermined current.

Thus, the time required for the current flowing through the primary winding of the transformer 106 to reach the second predetermined current from the start of energization (the timing of f1) is the conventional primary energization drive time T shown in FIG. 2A is earlier than the time T2 shown in FIG.

Here, if energization driving is performed until the current flowing through the primary winding of the transformer 106 reaches the second predetermined current, the microcomputer 105a sets the gate of the FET 107 to low level and turns off the FET 107 (at the timing of a1). ) And cut off the current to make it non-conductive. At the same time, the gate of the FET 127 is switched from the low level to the high level to stop the driving of the FET 127 (at the timing of d1) to stop the voltage doubling, and the gate of the FET 129 is changed from the low level to the high level. Is performed, and the voltage-doubling capacitor 126 is charged to the battery voltage in preparation for the voltage-doubling drive performed at the next energization drive.

By stopping the energization of the primary winding, a counter electromotive force is generated in the secondary winding of the transformer 106. This back electromotive force flows as a secondary current in a loop of the rectifier diode 108, the main capacitor 109, and the diode 120 (timing of e1), whereby electric charge is accumulated in the main capacitor 109.

The energy in the transformer 106 is released, the secondary current is shunted, and the low level g1
Is inverted from a low level to a high level at the time when the secondary current is substantially stopped (timing of g1). Then, in response to the inversion of the secondary input signal from the low level to the high level, the control IC 105 generates a high-level signal again at the gate of the FET 107, and similarly outputs the F-level signal again.
The ET 107 is made conductive (timing of a1), and the energy including the above-described voltage-double driving is stored in the transformer 106. Further, the FET 107 is turned off by the low level signal, the energy stored in the transformer 106 is released, and the electric charge is charged in the main capacitor 109. By repeating this operation, the voltage of the main capacitor 109 increases.

As described above, in this embodiment, the transformer 1
First, the voltage of the battery 101 is applied to the primary winding of the battery 06, and thereafter, a voltage approximately twice the battery voltage is applied. Therefore, the energy storage of the transformer 106 is faster than in the past, and the charging time can be reduced.

Here, it is considered that if a high voltage is applied to the transformer 106 from the initial stage of driving the primary current, charging can be performed in a shorter time.

However, if the double voltage application to the transformer 106 is performed from the initial drive of the primary current, a drive voltage to the transformer 106 is required (the voltage applied to the transformer 106 is increased due to an increase in the circuit resistance due to an increase in the drive current). In the later stage of the driving, the voltage of the voltage-doubling capacitor already drops, and a sufficient voltage-doubling effect cannot be obtained.

For this reason, by performing the double voltage application during the driving of the primary current, it is possible to perform the energizing drive that is effective for reducing the charging time.

Next, the operation of the camera of this embodiment will be described with reference to the flowcharts of FIGS.

First, the MAINSW 118 is turned on in FIG.
The sequence at the time of this is described. Step (S in the figure)
The microcomputer 105a includes:
It is determined whether or not the MAINSW 118 has been turned ON. MA
Step 102 when ON of the INSW 118 is detected
To read the battery voltage of the camera and store it in the RAM (battery check BC).

Next, in step 103, the microcomputer 105a determines whether the battery voltage stored in the RAM is
It is determined whether or not the voltage is such that the camera is operable. If the voltage is equal to or higher than the operable voltage, the process proceeds to step 104;

In step 104, the microcomputer 105a measures the luminance of the object through the photometric circuit 114, and stores the photometric result in the RAM in the microcomputer 105a. Next, in step 105, it is determined whether or not the photometric result stored in the RAM in the control IC 105 in step 104 is a photometric result that requires strobe light emission for photographing. If the photometry result does not require strobe light emission and the strobe preliminary charge is not required, the MAINSW ON sequence ends.
On the other hand, if the photometry result requires a strobe and precharge of the strobe is necessary, the process proceeds to step 106, where the strobe is charged.

Here, the flash charging in step 106 is performed according to the flowchart shown in FIG.

First, in step 301, the microcomputer 105a starts a charging timer. Next, in step 302, charging is started by the above-described circuit operation.

Then, the process proceeds to a step 303, wherein the control IC 1
The detection voltage of the main capacitor 109 is detected by the A / D 105d in the microcomputer 05 via the charging voltage detection circuit 112, and the detection result is stored in the RAM in the microcomputer 105a. It is determined whether the detected charging voltage is equal to or higher than a predetermined charging completion voltage (whether charging is completed). If charging completion is not detected, the process proceeds to step 306.

In step 306, it is determined whether or not the charging timer started in step 301 has elapsed a predetermined time. If the predetermined time has elapsed, the process proceeds to step 305 to stop charging and terminate the charging sequence.

If the predetermined time has not elapsed from the charging timer, the flow returns to step 303 to detect the charging voltage. The charging is performed while repeating the steps 303, 304 and 306. When completion is detected, the process proceeds to step 304, where charging is stopped and the charging sequence is terminated. Then, the sequence at the time of MAINSW ON in FIG. 3 ends.

Next, the release sequence will be described with reference to the flowchart of FIG. First, step 20
In step 1, when the microcomputer 105a detects that the SW1 (118) is turned on by the first stroke operation of the release button, the process proceeds to steps 202 and 203.

In steps 202 and 203, similarly to steps 102 and 103 in FIG. 3, the battery voltage is read (battery check BC), and it is determined whether or not the BC result is a voltage at which the camera can operate. If the BC result indicates an operable voltage, the process proceeds to step 204; otherwise, the process proceeds to step 201.

In step 204, the microcomputer 105a causes the distance measuring circuit 114 to measure the distance to the subject, and stores the result in the RAM in the microcomputer 105a.

Next, at step 205, the photometric circuit 11
The luminance of the subject is measured through the step 3, and the result is stored in the RAM in the microcomputer 105a.

Next, in step 206, step 20
In step 5, based on the photometric data stored in the RAM, it is determined whether strobe charging is necessary.

The case where the strobe light is required is when the photographing condition is dark or the subject is backlit. Here, when the flash emission is necessary, the process proceeds to step 207 as the flash emission shooting mode. If it is not necessary, the process proceeds to step 209 as the non-flash emission photographing mode, and waits until SW2 (119) is turned on.

In step 207, the main capacitor 109
It is determined whether or not the charging voltage is equal to or higher than the charging completion voltage (whether or not charging is completed). Step 209 when charging is completed.
And enters a standby state until SW2 (112) is turned on. On the other hand, if the charging is not completed, the process proceeds to step 208, where charging is performed.

The flash charging sequence in step 208 is the same as step 106 after the above-mentioned MAINSW is turned ON, and therefore the description thereof is omitted.

When the charging sequence is completed, step 2
In step 09, a standby state is set until the SW2 (119) is turned on.

In step 209, SW2 (119) is turned on.
Is detected, the microcomputer 105a proceeds to step 210, and controls the driving of the photographing lens through the lens driving circuit 115 based on the distance measurement data obtained in step 204.

Next, in step 211, the microcomputer 105 a uses the shutter coil 102 and the transistor 1 based on the photometric data obtained in step 205.
A drive control of a shutter drive circuit composed of a resistor 03 and a resistor 104 for current detection is performed to perform film exposure. At this time, when strobe light emission is necessary, a trigger signal is output to the trigger circuit 110 and the xenon tube 11 is output.
1 is discharged to emit strobe light.

Next, at step 212, the film driving circuit 116 is made to feed the film to the next photographing frame.
Further, in step 213, it is determined whether or not to perform the preliminary flash charging.

The case where the pre-flash charging is not performed is a case where the result determined in step 206 is the non-flash emission photographing mode.

Also, when performing pre-flash charging,
The result determined in step 206 is the case of the flash emission photographing mode.

If it is determined in step 213 that strobe preliminary charging is not to be performed, the camera sequence ends. If it is determined in step 213 that preflash charging is to be performed, the process proceeds to step 214.

In step 214, the above-mentioned MAINS
The main capacitor 109 is charged in the same manner as in step 106 in the sequence after W is turned on. Thereafter, when the charging is completed, the shooting sequence of the camera ends.

(Second Embodiment) FIG. 6 shows a second embodiment of the present invention.
1 illustrates a circuit configuration of a camera including an electronic strobe device according to an embodiment.

The circuit configuration of this embodiment is the same as the circuit configuration of the first embodiment shown in FIG. 1 except that the D / A 105c, the comparator 105e, the resistor 105f, and the resistor 123 are omitted.

FIG. 2 shows the circuit operation in this embodiment.
This will be described with reference to the timing chart shown in FIG.

FE from the control IC 105 via the connection terminal
When a predetermined oscillation signal (timing of a1) is given to the gate of T107, a high-level signal is given to the control electrode of the FET 107, and the drain = source, the primary winding of the transformer 106, and the negative loop of the battery 101 Electric current flows.

As a result, an induced electromotive force is generated in the secondary winding of the transformer 106. However, since the polarity of this current is such that it is blocked by the high-voltage rectifying diode 108, an exciting current flows from the transformer 106. Instead, energy is stored in the core in the transformer 106. This energy accumulation (energization drive) is performed until t1 (timing of f1), which reaches a first predetermined time set in advance.

Next, when the first predetermined time is reached, the control IC 105 outputs a low-level drive signal to the FET 127 so that the voltage applied to the transformer 106 becomes approximately twice the battery voltage (b1). , D1),
The drive signal of the FET 129 is driven for a predetermined time during a period t2 when the drive signal is switched from the high level to the low level (timing of c1).

By controlling the driving of the FET 127 and the FET 129 in this manner, the voltage-doubling capacitor 126, which has been connected in parallel to the battery 101 and has accumulated the charge up to the battery voltage, is connected in series to the battery 101. I do. As a result, a voltage approximately twice the voltage of the battery 101 is applied to the primary winding of the transformer 106.

Therefore, a current flows through the primary winding of the transformer 106 more steeply until the second predetermined time is reached than when it reaches the first predetermined time.

Thus, the time required for the current flowing through the primary winding of the transformer 106 to reach the second predetermined current from the start of energization (the timing of f1) is the conventional primary energization drive time T shown in FIG. 2A is earlier than the time T2 shown in FIG.

Here, when energization driving of the primary winding of the transformer 106 is performed until the second predetermined time is reached, the FET 1
The gate of 07 is set to low level to turn off the FET 107 (at the timing of a1), cut off the current, and turn off. At the same time, the gate of the FET 127 is switched from the high level to the low level to stop the driving of the FET 127 (at the timing of d1) to stop the voltage doubler. Is performed, and the voltage-doubling capacitor 126 is charged to the battery voltage in preparation for the voltage-doubling drive performed at the next energization drive.

By stopping the energization of the primary winding, a counter electromotive force is generated in the secondary winding of the transformer 106. This back electromotive force flows as a secondary current in a loop of the rectifier diode 108, the main capacitor 109, and the diode 120 (at timings of e1), whereby electric charge is accumulated in the main capacitor 109.

The energy in the transformer 106 is released, the secondary current is shunted, and the low level g1
Is inverted from a low level to a high level when the secondary current is substantially stopped (timing of g1). Then, in response to the inversion of the secondary input signal from the low level to the high level, the control IC 105 generates a high-level signal again at the gate of the FET 107, and similarly outputs the F-level signal again.
The ET 107 is made conductive (timing of a1), and the energy including the above-described voltage-double driving is stored in the transformer 106. Also, the FET 107 is turned off by the low level signal, the energy stored in the transformer 106 is released, and the electric charge is charged in the main capacitor 109. By repeating this operation, the voltage of the main capacitor 109 increases.

As described above, in this embodiment, the transformer 1
First, the voltage of the battery 101 is applied to the primary winding of the battery 06, and thereafter, a voltage approximately twice the battery voltage is applied. For this reason, the energy storage of the transformer 106 becomes faster than in the conventional case, and the charging time can be shortened.

Note that the camera sequence according to the present embodiment is the same as the camera sequence according to the first embodiment (FIGS. 3 to 5).
This is the same as the flowchart of FIG.

(Modification) Next, a modification of the first and second embodiments will be described based on the voltage doubler circuit of the power supply shown in FIGS.

In the timing charts shown in FIGS. 7 (b), 8 (b) and 9 (b), each SW signal has a high level indicating SW ON and a low level indicating SW ON.
Indicates FF.

In FIG. 7A, the FET 107 of the first and second embodiments corresponds to SW4, and the FET 127 corresponds to SW1. Further, the FET 129 corresponds to SW2. However, the diode 125 is omitted, and SW3 is provided instead.

In this circuit, SW3 and SW4 are turned on.
7B, driving by the battery voltage and charging of the doubling capacitor C during secondary current emission are performed, and by turning on SW2 with, it corresponds to the primary winding of the transformer 106. Double driving of the inductance I is performed.

According to such a circuit configuration, the voltage loss of VF in the diode 125 used in the first and second embodiments can be improved.

FIG. 8A shows a modification of FIG. 7A, which corresponds to a circuit in which SW4 is removed from the circuit of FIG. 7A.

In this circuit configuration, by performing the driving according to the timing chart of FIG. 8B, the voltage double driving of the inductance I corresponding to the primary winding of the transformer 106 with fewer parts than the circuit configuration of FIG. It can be performed.

FIG. 9 (a) shows a modification of FIG. 7 (a). SW1 to SW4 correspond to SW1 in FIG. 7 (a), respectively.
To SW4.

The circuit configuration of FIGS. 7 to 9 described above and the circuit for performing voltage multiplication described in the first and second embodiments can be appropriately selected according to the peripheral circuit configuration.

The switches SW1 to SW4 may be constituted by FETs or transistors according to the peripheral circuit configuration.

In the above embodiments, the case where the capacitor charging device is used for a flash device of a camera has been described. However, the present invention is also applicable to a capacitor charging device used for a device other than a camera or a flash device. Can be.

[0116]

As described above, according to the present invention,
If the booster capacitor is included in the circuit that applies the voltage to the primary side of the transformer in the flyback charging circuit,
A first voltage such as a power supply voltage is applied to the primary side of the transformer at an initial stage of charging, and a higher second voltage is applied at an appropriate timing. As compared with a charging device that applies the voltage of 2, the boosting effect of the boosting capacitor can be sufficiently obtained, and the main capacitor can be charged efficiently and in a short time.

By using this capacitor charging circuit in a light-emitting device mounted on a camera or the like, it is possible to realize an easy-to-use camera or the like having a short charging time for enabling light emission.

[Brief description of the drawings]

FIG. 1 is a block diagram of an electric circuit of a camera according to a first embodiment of the present invention.

FIG. 2 is a timing chart showing an operation of a charging circuit included in the electric circuit.

FIG. 3 is an operation flowchart of the camera.

FIG. 4 is an operation flowchart of the camera.

FIG. 5 is a flowchart of a main capacitor charging operation in the camera.

FIG. 6 is a block diagram of an electric circuit of a camera according to a second embodiment of the present invention.

FIG. 7 is a modification example and operation timing chart of the voltage doubler circuit in the charging circuits shown in the first and second embodiments.

FIG. 8 is a modification example and operation timing chart of the voltage doubler circuit in the charging circuits shown in the first and second embodiments.

FIG. 9 is a modification example and operation timing chart of the voltage doubler circuit in the charging circuits shown in the first and second embodiments.

FIG. 10 is an explanatory diagram of the camera.

FIG. 11 is a block diagram of an electric circuit of a conventional camera.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Battery 102 Shutter coil 103 Transistor 104 Resistance 105 Control IC 106 Transformer 107 FET 108 High voltage rectifier diode 109 Main capacitor 110 Trigger circuit 111 Xenon discharge tube 112 Charging voltage detection circuit 113 Photometry circuit 114 Distance measurement circuit 115 Lens drive circuit 116 Film drive circuit 117 MAINSW 118 SW1 119 SW2 120 Diode 121 Resistor 122 Resistor 123 Resistor 124 Capacitor 125 Diode 126 Doubler Capacitor 127 FET 128 Resistor 129 FET 130 Resistor

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // H02M 3/07 H02M 3/07 F term (reference) 2H053 BA08 BA09 3K098 AA03 AA04 AA20 AA30 BB01 BB14 BB20 5G003 AA04 BA01 CA04 CC07 DA16 GA01 GB04 GC05 5H730 AS18 BB43 DD02 EE07 FD01 FF09

Claims (11)

[Claims] 1. A capacitor charging device having a flyback type charging circuit for charging a main capacitor, wherein a boosting capacitor is provided in a circuit for applying a voltage to a primary side of a transformer constituting the charging circuit. Control means for applying a first voltage to a primary side of the transformer, and then applying a second voltage higher than the first voltage by using a charge stored in the booster capacitor A capacitor charging device comprising: 2. The capacitor charging device according to claim 1, wherein the first voltage is a voltage of a power supply. 3. The capacitor charging device according to claim 1, wherein the second voltage is substantially twice as large as the first voltage. 4. The control means, when applying the first voltage to the primary side of the transformer, connects the booster capacitor in parallel to a power supply, and connects the second voltage to the primary side of the transformer. 4. The capacitor charging device according to claim 1, wherein when the voltage is applied, the boosting capacitor is connected in series to a power supply. 5. 5. The control unit applies the first voltage until the current flowing to the primary side of the transformer reaches a first current value from the start of energization, and after the current reaches the first current value, The capacitor charging device according to any one of claims 1 to 4, wherein the second voltage is applied until a second current value higher than the first current value is reached. 6. The control means applies the first voltage to the primary side of the transformer until a first predetermined time is reached from the start of energization, and after a lapse of the first predetermined time, a second predetermined time The capacitor charging device according to any one of claims 1 to 4, wherein the second voltage is applied until the voltage of the capacitor is reached. 7. A first switch element, which is operation-controlled by said control means and operates to apply said first voltage to a primary side of said transformer, and said second voltage is applied to a primary side of said transformer. The capacitor charging device according to any one of claims 1 to 6, further comprising a second switch element that operates to apply the voltage. 8. The first and second switch elements,
The capacitor charging device according to claim 7, which is a transistor. 9. The first and second switch elements,
The capacitor charging device according to claim 7, wherein the capacitor charging device is a field effect transistor. 10. A light emitting device, comprising: the capacitor charging device according to claim 1; and light emitting means that emits light using electric charges charged in the main capacitor. 11. A light-emitting device according to claim 10, comprising:
A camera characterized by illuminating a subject with the light emitting device.