JP2004071428A - Capacitor charging device and strobe charging device for camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to speedily detect abnormalities in a circuit without increasing the number of parts. <P>SOLUTION: The device is provided with a main capacitor 107, secondary current detecting means 103a, 122, 121 equipped with flyback type DC/DC converters 104, 105, 103a charging the main capacitor and detecting a state of a secondary current flowing in a secondary winding of the DC/DC converters in operation, and a determinination means 103f for determining whether a detection time of the secondary current detected by the secondary current detecting means is over a prescribed time, and a charging operation of the capacitor charging device is controlled (103a) from the determination result of the determination means. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an improvement in a capacitor charger having a flyback type DC / DC converter and a strobe charger for a camera.
[0002]
[Prior art]
Conventionally, as a configuration for detecting an abnormality of a circuit provided in a strobe device, as disclosed in Japanese Patent Application Laid-Open No. 08-008089, a timer started at the start of a boosting operation is used to store a charging voltage after a fixed time. After that, a battery check is performed, and when the charge level is low even though there is a sufficient battery, the charge boosting operation is stopped and a warning is issued.
[0003]
[Problems to be solved by the invention]
However, in the above conventional example, it is for detecting an abnormality in the circuit of the forward type DC / DC converter, and it is necessary to wait for a certain time as described above in order to detect an abnormality in the circuit. For this reason, there has been a problem that the detection of the abnormality of the circuit is delayed by the predetermined time.
[0004]
(Object of the invention)
SUMMARY OF THE INVENTION An object of the present invention is to provide a capacitor charging device and a strobe charging device for a camera that can quickly detect an abnormality in a circuit or immediately stop a charging operation that is not performed normally without increasing the number of components. It is assumed that.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claims 1 to 4 is directed to a capacitor charging apparatus having a main capacitor and a flyback DC / DC converter for charging the main capacitor. Secondary current detecting means for detecting the state of the secondary current flowing through the secondary winding during the operation of, and whether the detection time of the secondary current detected by the secondary current detecting means is a predetermined time or more Determination means for determining whether or not the capacitor charging device controls the charging operation of the capacitor charging device based on the determination result of the determination means.
[0006]
According to the above configuration, after the current drive of the primary winding of the transformer and the drive stop thereof are performed by the primary current drive unit, the time from the drive stop to the secondary current dropping to the predetermined current or the stop of the secondary current. Is longer than a predetermined time. Then, based on the result of this determination, control is performed to continue and stop the charging operation.
[0007]
Similarly, in order to achieve the above object, an invention according to claim 5 is a capacitor charging device having a main capacitor and a flyback DC / DC converter for charging the main capacitor, wherein the DC / DC converter Secondary current detection means for detecting a state of a secondary current flowing through the secondary winding during operation; and whether or not a detection time of the secondary current detected by the secondary current detection means is a predetermined time or more. And a determination unit that determines that there is an abnormality in a circuit of the capacitor charging device when the determination unit determines that the time is less than the predetermined time.
[0008]
According to another aspect of the present invention, there is provided a strobe charging device for a camera having the capacitor charging device according to any one of the first to fifth aspects.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on illustrated embodiments.
[0010]
FIG. 1 is a block diagram showing a circuit configuration of a main part of a camera including a strobe device including a flyback type DC / DC converter according to an embodiment of the present invention.
[0011]
In the figure, reference numeral 101 denotes a battery serving as a power supply, and 101a denotes a battery internal resistance. A capacitor 102 is connected in parallel with the battery 101. Reference numeral 103 denotes a control circuit including an IC, which controls a camera sequence such as photometry, distance measurement, lens driving, and film feeding of a camera, and controls a flash device. Reference numeral 103c denotes a D / A converter, which arbitrarily outputs a voltage according to a setting signal of the microcomputer 103a. An A / D converter 103b digitizes the input voltage. A comparator 103d detects whether or not the current of the primary winding of the transformer 104 described later has reached a set current based on the voltage generated by the resistor 123. 103e is a resistor, which pulls up the output of the comparator 103d. 103f is a secondary current emission time determination block for determining whether or not the secondary current emission time is a predetermined time, and 103g is a comparator for detecting whether the charging voltage has reached the charging completion voltage. 103h is a resistor that pulls up the output of the comparator 103g. An AND gate 103i outputs a gate signal of the FET 105 described later.
[0012]
Reference numeral 104 denotes a transformer, which stores a current in a loop of the positive electrode of the battery 101, the primary winding, the FET 105, and the negative electrode of the battery 101, thereby accumulating energy in the core and generating back electromotive force using the energy. An FET 105 drives the current of the primary winding of the transformer 104. Reference numeral 107 denotes a main capacitor that stores electric charges. Reference numeral 106 denotes a high-voltage rectifier diode, whose anode is connected to the end of the secondary winding of the transformer 104 and whose cathode is connected to the anode of the main capacitor 107. 119 is a resistor, which is connected between the base and the emitter of the transistor 120 described later. Reference numeral 120 denotes a transistor, whose base is connected to the cathode of the main capacitor 107 and whose emitter is connected to the beginning of the winding of the secondary winding of the transformer 104, respectively. The counter electromotive force generated from the secondary winding of the transformer 104 is applied to the main capacitor 107. Is formed in a configuration including the high-voltage rectifier diode 106.
[0013]
Reference numeral 121 denotes a resistor, one side of which is connected to the collector of the transistor 120 and the other side of which is connected to the control circuit 103. Reference numeral 122 denotes a resistor, which pulls up the input of the control circuit 103 to which the resistor 121 is connected to the power supply Vcc. 108 is a trigger circuit. Reference numeral 109 denotes a discharge tube which receives a trigger voltage from the trigger circuit 108 and emits light by electric charges accumulated in the main capacitor 107. Reference numeral 110 denotes a charging voltage dividing circuit, which divides the voltage stored in the main capacitor 107 and detects the charging voltage by a comparator 103g in the control circuit 103.
[0014]
A photometric circuit 111 detects the brightness of the subject. Reference numeral 112 denotes a distance measuring circuit that detects a distance to a subject. Reference numeral 113 denotes a lens driving device which drives the photographing lens based on the detection result from the distance measuring circuit 112 and focuses the subject on the film surface. Reference numeral 114 denotes a shutter driving device which performs exposure control based on a detection result from the photometry circuit 111. Reference numeral 115 denotes a film driving device that performs automatic loading, winding, and rewinding of the film. Reference numeral 116 denotes a main switch (MAINSW) for setting the camera in a shooting preparation state, and 117 (SW1) denotes a switch, which activates an electric circuit in the camera by a first stroke of a shutter button to detect photometry, distance measurement, and the like. . Reference numeral 118 (SW2) is a switch, which is turned on by the second stroke of the shutter button, and generates a start signal of a photographing sequence after the switch SW1 is turned on.
[0015]
Further, a is a gate input signal (FETGATE) of the FET 105, b is a primary current flowing through the primary winding of the transformer 104, and c is a secondary current flowing through the secondary winding of the transformer 104. d is a secondary current detection signal in which the resistors 121 and 122 are connected and connected to the control circuit 103.
[0016]
2A and 2B are timing charts at the time of the boosting operation. Specifically, FIG. 2A shows that the charging voltage of the main capacitor 109 is about 50 V, FIG. 2B shows that the charging voltage of the main capacitor 109 is about 150 V, and FIG. c) shows the currents and signals a to d when the charging voltage of the main capacitor 109 is about 320 V.
[0017]
Next, the boosting operation will be described below by taking as an example a case where the charging voltage of the main capacitor 109 in FIG.
[0018]
A predetermined oscillation signal (timing of (1) of FETGATEa) is given from the control circuit 103 to the gate of the FET 105 via the connection terminal. Therefore, when a high-level signal is applied to the control electrode of the FET 105, a current flows through a loop of the battery anode, the primary winding of the transformer 104, the drain / source of the FET 105, the resistor 123, and the battery negative electrode. For this reason, an induced electromotive force is generated in the secondary winding of the transformer 104, but since the polarity of this current is a polarity blocked by the high-voltage rectifying diode 106, no exciting current flows from the transformer 104, Energy is stored in the core in the transformer 104. This energy accumulation (primary current drive) reaches a current at which the output of the comparator 103d is inverted when the voltage generated by the current flowing through the resistor 123 reaches the voltage set by the D / A converter 103c, a so-called predetermined current ( Up to the timing (2) of the primary current b).
[0019]
Here, when the current driving is performed to a predetermined current, the gate of the FET 105 is set to the low level to turn off the FET 105 (timing (2) of the FET GATEa) to cut off the current and make it non-conductive. Thereby, a back electromotive force is generated in the secondary winding of the transformer 104. This back electromotive force flows through the loop of the rectifier diode 106, the main capacitor 107, the resistor 119, and the transistor 120 as a secondary current (timing of the secondary current c in (2) to (3)). Stored. The energy in the transformer 104 is released, the secondary current c is shunted, and the secondary current detection signal d, which has been at a low level, is changed to the time when the secondary current c stops (（3 of the secondary current detection signal d). The timing is inverted from low level to high level. In response to the inversion of the secondary current detection signal d from the low level to the high level, the control circuit 103 outputs a high-level signal to the gate of the FET 105 again, and similarly conducts the FET 105 again ((3) of FETGATEa). At the timing, energy is stored in the transformer 104, and the FET 105 is turned off by the low level signal, the stored energy in the transformer 104 is released, and the electric charge is charged in the main capacitor 107.
[0020]
This operation is repeated, and the discharge time of the secondary current c (the timing of (2) to (3) of the secondary current c) is shortened as shown in FIGS. 2 (a) → (b) → (c). While increasing the voltage of the main capacitor 107. This charging circuit is generally called a flyback system.
[0021]
Hereinafter, the operation of the circuit configuration of FIG. 1 will be described with reference to FIGS.
[0022]
First, the sequence when the main switch 116 is turned on will be described with reference to the flowchart of FIG.
[0023]
At step # 101, it is determined whether or not the main switch 116 is turned on. If the main switch 116 is turned on, the process proceeds to step # 102, where it is determined whether or not the battery voltage is the operable voltage of the camera. A battery check (BC) for detection is performed, and the result is stored in the RAM in the microcomputer 103a. Then, in the next step # 103, it is determined whether or not the result of the battery check performed in the above-mentioned step # 102 is a voltage at which the camera can be operated. The process proceeds to step # 101, but returns to step # 101 if the voltage cannot operate.
[0024]
If it is determined that the battery voltage is the operable voltage of the camera and the process proceeds to step # 104, photometry is performed by the photometry circuit 111 for detecting the luminance of the subject, and the result is stored in the RAM in the microcomputer 103a. Then, in the next step # 105, it is determined from the photometry result obtained in the above step # 104 whether or not strobe light emission is required for photographing. As a result, when it is determined that strobe pre-charging is not required at a luminance that does not require strobe light emission, this sequence is terminated. On the other hand, if it is determined in step # 105 that the brightness requires strobe light emission and strobe preliminary charging is required, the flow advances to step # 106 to perform strobe charging in the flash mode (the details will be described below with reference to FIG. 4). explain). Then, this sequence ends.
[0025]
Next, the operation in the flash mode in step # 106 of FIG. 3 will be described with reference to the flowchart of FIG.
[0026]
First, in step # 301, a charging timer is started. Then, in the next step # 302, a drive signal is output from the control circuit 103 to the gate of the FET 105 by the above-described circuit operation, and charging is started. In the following step # 303, it is determined whether or not the secondary current c generated after the stop of the driving of the primary current b has been detected after the lapse of a predetermined time (a predetermined time or more) (the state in which the secondary current c is flowing). Do. The emission time of the secondary current is the timing of the timings (2) to (3) in FIGS. 2A to 2C described above, and the secondary current is determined by the secondary current emission time determination block 103f. It is determined whether or not the detection has been performed even after a lapse of time. This determination is based on a state in which the count is started in response to the drive signal (FETGATEa) of the FET 105 being turned off (falling), and after a predetermined time has elapsed, the secondary current c disappears (the secondary current detection signal d is at a high level). ) It is performed by detecting whether or not it is in the state. The determination as to whether or not the discharge time of the secondary current is a predetermined time is performed to detect an abnormality in the circuit.
[0027]
Here, for example, the circuit operation when the discharge loop including the secondary winding of the transformer 104, the rectifier diode 106, the main capacitor 107, and the transistor 120 is in an open state (in the case of a circuit abnormality) is shown in FIG. This will be described with reference to the timing chart of FIG.
[0028]
A predetermined oscillation signal (timing (1) of FETGATEa in FIG. 5) is given from the control circuit 103 to the gate of the FET 105 via the connection terminal. Therefore, when a high-level signal is applied to the control electrode of the FET 105, a current flows through the drain / source, the primary winding of the transformer 104, and the loop of the battery negative electrode. For this reason, an induced electromotive force is generated in the secondary winding of the transformer 104, but since the discharge loop is open, no excitation current flows from the transformer 104, and energy is stored in the core inside the transformer 104. This energy accumulation (primary current driving) is performed until the current of the primary winding reaches a predetermined current (timing of (2) of the primary current b).
[0029]
Here, when the current drive is performed to a predetermined current, the gate of the FET 105 is set to the low level to turn off the FET 105 (timing of the primary current b (2)), cut off the current to make it non-conductive, and release the secondary current. The time determination block 103f starts measuring a predetermined time. At about the same time when the FET 105 is turned off, a back electromotive force is generated in the secondary winding of the transformer 104. If the circuit is normal, the rectifier diode 106 and the main capacitor 107 are used as the secondary current (timing of (2) to (3) c in FIGS. 2A to 2C) as described above if the circuit is normal. , A current flows through the loop of the diode 120, and the electric charge is accumulated in the main capacitor 107.
[0030]
However, when the secondary-side discharge loop is in the open state (timing (2) of the secondary current c in FIG. 5), the secondary current c is not generated. Therefore, no voltage is generated across the resistor 119 for detecting the secondary current c. Also, since the transistor 120 for generating the secondary current detection signal d naturally remains off, the gate of the FET 105 is set to low level to turn off the FET 105 (timing (2) of the FET GATEa in FIG. 5) to cut off the current. Thus, even if the secondary current detection signal d does not conduct, the secondary current detection signal d does not change to the low level (at timing (2) of the secondary current detection signal d in FIG. 5) and is always at the high level. Therefore, the secondary current emission time determination block 103f determines that the secondary current c has disappeared (the secondary current detection signal d is at a high level) when the predetermined time has elapsed (less than the predetermined time). . Thereby, it can be detected that there is a trouble in the circuit.
[0031]
As an example of a different circuit trouble, a circuit operation when the primary winding or the secondary winding of the transformer 104 is short-circuited will be described with reference to a timing chart of FIG.
[0032]
A predetermined oscillation signal (timing (1) of FETGATEa in FIG. 6) is given from the control circuit 103 to the gate of the FET 105 via the connection terminal. Therefore, when a high-level signal is applied to the control electrode of the FET 105, a current flows through the drain / source, the short-circuited primary winding of the transformer 104, and the loop of the battery negative electrode. Then, the current drive is performed until the predetermined current is reached (the timing of (2) of the primary current b in FIG. 6). At this time, the current of the short-circuited primary winding quickly reaches a predetermined current. Here, when the current drive is performed to a predetermined current, the gate of the FET 105 is set to the low level, the FET 105 is turned off (timing (2) of the FET GATEa in FIG. 6), and the current is cut off to be non-conductive. As a result, if the circuit is normal, a back electromotive force is generated in the secondary winding of the transformer 104.
[0033]
However, if the primary winding is short-circuited, no energy is stored in the transformer 104. Therefore, similarly to the above-described secondary discharge loop opening, the gate of the FET 105 is set to the low level, the FET 105 is turned off (the timing of (2) of the FET GATEa in FIG. 6), the current is cut off, and the FET 105 is turned off. As described above, no voltage is generated across the resistor 119 that detects the secondary current c. Also, since the transistor 120 that generates the secondary current detection signal d naturally remains off, the secondary current detection signal d does not change to a low level (the timing of the secondary current detection signal d in FIG. ) Is always at the high level. Accordingly, the secondary current release time determination block 103f determines that the secondary current c has disappeared (the secondary current detection signal d is at a high level) when a predetermined time has elapsed. Thereby, it can be detected that there is a trouble in the circuit.
[0034]
When the secondary winding is short-circuited, the timing chart is the same as when the primary winding is short-circuited, and it can be detected that there is a trouble in the circuit.
[0035]
As described above, in a normal circuit state, the emission of the secondary current c is detected even after a predetermined time, whereas the secondary winding of the transformer 104, the rectifier diode 106, the main capacitor 107, and the loop of the diode 120 The secondary current detection signal d goes high when a predetermined time has elapsed when a circuit trouble occurs, such as a discharge loop composed of an open state or a short circuit of the primary winding or the secondary winding of the transformer 104. In the level state, the secondary current c is not detected.
[0036]
Returning to FIG. 4, in the next step # 304, the detection result of whether or not the secondary current c is detected after the lapse of a predetermined time, which is performed in the secondary current emission time determination block 103 f in the above step # 303, It is determined whether or not the charging is normal. As described above, when the secondary current generated after the stop of the primary current drive is detected after the elapse of a predetermined time, the circuit is normal. Therefore, in this case, the process proceeds from step # 304 to step # 307. However, if the secondary current generated after the stop of the primary current drive is not detected after the lapse of a predetermined time, there is an abnormality in the circuit. Therefore, in this case, the process proceeds from step # 304 to step # 305 to stop charging, and in the next step # 306, an abnormality flag of the circuit is set, and the charging sequence ends.
[0037]
As described above, when the secondary-side discharge loop is in an open state or when the primary winding of the transformer 104 or the secondary winding is short-circuited, the primary winding is determined based on the determination result of the secondary current emission time determination block 103f. Circuit abnormality can be detected at the first current drive to the line, and the circuit can be detected at a very early timing from the start of charging without waiting for a certain period of time and without adding a special circuit configuration as in the past. Abnormalities can be detected.
[0038]
When the process proceeds to step # 307 assuming that the circuit is normal in step # 304, the comparator 103g in the control circuit 103 determines whether or not the voltage of the charging voltage has reached the charging completion voltage by the voltage via the charging voltage dividing circuit 110. Is detected. Here, if the completion of charging has not been detected, the process proceeds to step # 310, and it is determined whether or not the charging timer started in step # 301 has passed a predetermined time. Then, the process proceeds to step # 311 to stop the charging started in step # 302, and in the next step # 312, sets a flag of charging NG and ends the charging sequence.
[0039]
On the other hand, if the charging timer has not passed the predetermined time in step # 310, the process returns to step # 302 to continue charging. Then, the operations of steps # 303 → # 304 → # 307 → # 310 are repeated, and in step # 307, the comparator 103g in the control circuit 103 is charged by the voltage via the charging voltage dividing circuit 110 to the charging completion voltage of the charging voltage. When it is detected that the charging has been reached, the process proceeds to step # 308, the charging started in step # 302 is stopped, and in the next step # 309, a charging OK flag is set, and the charging sequence is ended. Then, the sequence when the main switch of FIG. 3 is turned on ends.
[0040]
Further, here, the main capacitor of the charging voltage dividing circuit 110 for detecting the charging voltage of the main capacitor 107, which can be detected in the repeating sequence of the operations of steps # 302 → # 303 → # 304 → # 307 → # 310. A case where there is an abnormality in the connection to 110 or the connection to the control circuit 103 will be described with reference to the timing chart of FIG.
[0041]
Before that, first, the relationship between the charging voltage and the secondary current emission time will be described with reference to FIG.
[0042]
When a certain energy (primary current) is stored in a certain transformer, and when the charging voltage of the main capacitor is about 20 V, the discharge time of the secondary current is about 25 μS from FIG. At 50 V, the secondary current emission time is about 10 μS, at a charging voltage of 100 V, the secondary current emission time is about 5 μS, and at a charging voltage of 200 V, the secondary current emission time is about 3 μS. When the charging voltage is 320 V, the secondary current emission time varies with the charging voltage, for example, the secondary current emission time is about 2 μS. The relationship between the charging voltage and the discharge time of the secondary current differs for each transformer depending on the size of the transformer and the number of turns of the winding. However, if the size and the number of turns of the winding are the same, the characteristics will be the same.
[0043]
Here, assuming that the charge completion voltage is 320 V, the discharge time of the secondary current is 2 μS. For example, the connection of the charging voltage dividing circuit 110 for detecting the charging voltage of the main capacitor 107 to the main capacitor 110 or the connection to the control circuit 103 has a disconnection abnormality, and the charging voltage of the main capacitor 109 is the charging completion voltage of 320 V Suppose you have reached the above. Then, the discharge time of the secondary current is further shorter than the secondary current discharge time of 2 μS of the charge completion voltage shown in FIG. That is, by setting the determination time (predetermined time) of the secondary current emission time determination block 103f to 2 μS or less, for example, about 1.5 μS, the main capacitor of the charging voltage dividing circuit 110 for detecting the charging voltage of the main capacitor 107 is set. A disconnection abnormality can be detected in the connection to the control circuit 107 or the control circuit 103. That is, the charging abnormality can be detected without waiting for step # 310, which is the counting up of the charging timer started in step # 301.
[0044]
The condition of the determination time of the secondary current emission time determination block 103f that makes this circuit normal is arbitrarily set according to the size of the transformer and the number of windings of the winding, and the secondary current at the time of completion of charging is determined. The time is shorter than the release time.
[0045]
As described above, by performing the determination by the secondary current emission time determination block 103f, when the secondary discharge loop is in an open state, or when the primary winding or the secondary winding of the transformer 104 is short-circuited, Each abnormality such as disconnection of the charging voltage detection unit can be detected.
[0046]
Next, the release sequence of the camera will be described with reference to the flowchart of FIG.
[0047]
First, in step # 201, the state of the switch SW1 (117) which is turned on by the first stroke of the release button is checked, and if it is not turned on, the process remains at this step until it is turned on. Thereafter, when the switch SW1 is turned on, the process proceeds to step # 202, and a battery check (BC) is performed to detect whether or not the battery voltage allows the camera to operate, as in step # 102, and the detection result Is stored in the RAM in the microcomputer 103a. Then, in the next step # 203, it is determined from the result of the battery check performed in the above step # 202 whether or not the battery voltage is a voltage at which the camera can be operated. The process proceeds to step # 204, and if the voltage cannot be operated, the process returns to step # 201.
[0048]
When it is determined that the battery voltage is a voltage at which the camera can operate, the process proceeds to step # 204. The distance measurement circuit 112 detects the distance to the subject, and stores the distance measurement result in the RAM in the microcomputer 103a. In the following step # 205, the luminance of the subject is detected by the photometric circuit 111, and the result (photometric result) is stored in the RAM in the microcomputer 103a.
[0049]
Thereafter, the process proceeds to step # 206, and it is determined whether or not strobe light emission is necessary based on the photometry result obtained in step # 205. When the strobe light is required, the photographing situation is dark or the subject is backlit. If the flash emission is required, the process proceeds to step # 207. If the flash emission is not required, the process proceeds to step # 209, where the switch SW2 (118) is turned on.
[0050]
If it is determined in step # 206 that strobe light emission is necessary and the process proceeds to step # 207, the charging sequence shown in the flowchart of FIG. 4 is executed. Since this charging sequence is as described above, its description is omitted here. Thereafter, the process proceeds to step # 208, and it is determined whether or not the charging is completed. This determination is made based on a flag indicating whether or not charging has been completed in the charging sequence in step # 207. If charging has been completed and charging has been completed, the switch SW2 (118) in step # 209 is turned on. Enter the standby state. On the other hand, if the charging is NG and the charging is not completed, the process returns to step # 201.
[0051]
Proceeding to step # 209, in the standby state of turning on the switch SW2 (118), when it is detected that the switch SW2 is turned on, proceeding to step # 210, the lens driving is performed according to the distance measurement result obtained in step # 204. The drive of the taking lens is controlled by the device 113. Then, in the next step # 211, based on the photometry result obtained in step # 205, if strobe light emission is required, the trigger circuit 108 receives a trigger signal from the control circuit 103 and outputs a light emission signal. Performs flash emission. At the same time, shutter drive control by the shutter drive device 114 is performed. Next, in step # 212, a lens reset is performed to return the lens at the in-focus position to the initial position of the lens.
[0052]
In the following step # 213, film feed control to the next photographing frame is performed by the film driving device 115, and in the next step # 214, it is determined whether or not to perform the preliminary flash charging. Here, the case where the strobe pre-charging is not performed is a case where the result determined in step # 206 based on the photometry result performed in step # 205 is not the flash mode. In this case, the process returns to step # 201.
[0053]
When performing the flash preliminary charge, the process proceeds from step # 214 to step # 215 to execute the charging sequence described above with reference to the flowchart of FIG. Thereafter, the flow returns to step # 201.
[0054]
According to the above embodiment, the FET 105 that has the flyback type DC / DC converter that charges the main capacitor 107 and drives the primary winding of the transformer 104 of the DC / DC converter, The microcomputer 103a detects the current flowing through the secondary winding generated by stopping the driving of the current, and the time required for the secondary current to drop to the predetermined current after the driving of the current to the primary winding of the FET 105 is stopped is longer than a predetermined time. A secondary current emission time determination block 103f for determining whether there is a circuit, and detecting an abnormality of the circuit from the time measurement result of the secondary current emission time determination block 103f.
[0055]
Specifically, the discharge loop including the secondary winding of the transformer 104, the rectifier diode 106, the main capacitor 107, and the diode 120 is in an open state, or the primary winding or the secondary winding of the transformer 104 is short-circuited. Or when a circuit abnormality such as disconnection of the charging voltage detection unit occurs and the secondary current release time is shorter than a predetermined time (or the same is true when the secondary current is stopped (disappears) and is not detected). , It is determined that the circuit is abnormal.
[0056]
If the discharge loop is in an open state or a circuit abnormality such as a short circuit of the primary winding or the secondary winding of the transformer 104, the result of this secondary current release time is the first occurrence of the primary winding to the primary winding. It can be detected at the time of current driving, and it is possible to detect an abnormality in a circuit at an extremely early timing from the start of charging without waiting for a certain time and adding a special circuit as in the related art.
[0057]
Further, in the case of a circuit abnormality such as a disconnection of the charging voltage detection unit, an abnormality of the circuit can be detected at an early timing without waiting for the timer time of the charging timer.
[0058]
According to the above-described embodiment, the boosting method is performed by the separate excitation control of the flyback DC / DC converter by the control circuit 103. However, the boosting method is not limited to the separate excitation control, and is performed by the self-excitation control. It is needless to say that a circuit trouble can be similarly detected by employing a configuration in which a secondary current is detected even in a boosting method of a flyback type DC / DC converter.
[0059]
Furthermore, in the primary current driving method in the separate excitation control, the driving of the primary current is stopped when the primary current reaches the predetermined current. The primary current is not limited to the current detection type, and the primary current is driven for the predetermined time. Needless to say, a type that can be driven for a predetermined time is also possible.
[0060]
【The invention's effect】
As described above, according to the present invention, without increasing the number of parts, it is possible to quickly detect an abnormality in a circuit or to immediately stop a charging operation that is not performed normally. It is possible to provide a strobe charging device.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a circuit configuration of a camera according to an embodiment of the present invention.
FIG. 2 is a timing chart of the booster circuit in a normal state in one embodiment of the present invention.
FIG. 3 is a flowchart showing an operation of the camera according to the embodiment of the present invention.
FIG. 4 is a flowchart showing an operation during charging according to the embodiment of the present invention.
FIG. 5 is a timing chart of the booster circuit at the time of abnormality in one embodiment of the present invention.
FIG. 6 is a timing chart of the booster circuit when an abnormality occurs.
FIG. 7 is a flowchart showing another operation of the camera according to the embodiment of the present invention.
FIG. 8 is a diagram showing a relationship between a charging voltage and a secondary current emission time according to an embodiment of the present invention.
[Explanation of symbols]
101 Power battery
102 Capacitor
103 control circuit
103a microcomputer
104 transformer
105 FET
106 High voltage rectifier diode
107 Main capacitor
108 trigger circuit
109 discharge tube
110 Charge voltage detection circuit
111 photometric circuit
112 Distance measuring circuit
113 Lens drive
114 Shutter drive
115 Film drive
119 Resistance
120 transistor
121 resistance
122 resistance
123 resistance

Claims (6)

In a capacitor charging device having a main capacitor and a flyback DC / DC converter for charging the main capacitor,
A secondary current detecting means for detecting a state of a secondary current flowing through the secondary winding during the operation of the DC / DC converter; and a detection time of the secondary current detected by the secondary current detecting means is a predetermined time. Determining means for determining whether or not it is the above,
The capacitor charging device controls a charging operation of the capacitor charging device based on a result of the determination by the determining unit. The capacitor charging device according to claim 1, wherein the charging operation is stopped when the determination unit determines that the time is less than the predetermined time. 3. The capacitor charging device according to claim 1, wherein the secondary current detection unit detects stop of the secondary current or a decrease in the secondary current to a predetermined current. 4. The capacitor charging device according to any one of claims 1 to 3, wherein the predetermined time of the determination unit is a time shorter than a secondary current discharge time at the time of completion of charging. In a capacitor charging device having a main capacitor and a flyback DC / DC converter for charging the main capacitor,
A secondary current detecting means for detecting a state of a secondary current flowing through the secondary winding during the operation of the DC / DC converter; and a detection time of the secondary current detected by the secondary current detecting means is a predetermined time. Determining means for determining whether or not it is the above,
A capacitor charging device, wherein when the determination unit determines that the time is less than the predetermined time, it is determined that there is an abnormality in a circuit of the capacitor charging device. A flash charging device for a camera, comprising the capacitor charging device according to claim 1.

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