JP2004343968A - Charging circuit device - Google Patents

Charging circuit device Download PDF

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Publication number
JP2004343968A
JP2004343968A JP2003140815A JP2003140815A JP2004343968A JP 2004343968 A JP2004343968 A JP 2004343968A JP 2003140815 A JP2003140815 A JP 2003140815A JP 2003140815 A JP2003140815 A JP 2003140815A JP 2004343968 A JP2004343968 A JP 2004343968A
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JP
Japan
Prior art keywords
charging
driving frequency
converter transformer
voltage
battery
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP2003140815A
Other languages
Japanese (ja)
Inventor
Toshio Nito
登志男 仁藤
Original Assignee
Tokyo Coil Engineering Kk
東京コイルエンジニアリング株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Tokyo Coil Engineering Kk, 東京コイルエンジニアリング株式会社 filed Critical Tokyo Coil Engineering Kk
Priority to JP2003140815A priority Critical patent/JP2004343968A/en
Publication of JP2004343968A publication Critical patent/JP2004343968A/en
Application status is Pending legal-status Critical

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Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging circuit device capable of improving a charging efficiency for a charging capacitor and charging characteristics. <P>SOLUTION: This charging circuit device comprises a converter transformer 13, a battery 11, a FET14 for switching on and off electric current passing through a primary coil of the converter transformer from the battery, the charging capacitor C2 connected to a secondary coil of a converter transformer through a rectification element, and a controller 15 for varying a driving frequency for switching the FET14 according to the charging voltage of the charging capacitor. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a charging circuit device that charges a charging capacitor used for a strobe flash, for example.
[0002]
[Prior art]
Recently, digital cameras have rapidly become widespread. This digital camera is equipped with a strobe flash as standard. This strobe flash is driven by a charging voltage of about 300 V charged in a charging capacitor.
[0003]
When the strobe flash is used, the charging voltage of the charging capacitor is reduced. Therefore, a charging circuit for charging the charging capacitor is provided in the apparatus. As the charging circuit, in a recent digital camera or the like, a flyback oscillation method is selected because current consumption from a battery is limited. Further, as a circuit system, a separate excitation system is employed because its configuration is simple (for example, see Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Application No. 63-245264
[Problems to be solved by the invention]
When the separately excited system is employed as the charging circuit, it is necessary to determine the driving frequency or the duty ratio. Conventionally, the driving frequency and the duty ratio are constant regardless of the magnitude of the charging voltage of the charging capacitor.
[0006]
However, since the charging efficiency of the charging capacitor changes according to the driving frequency, even if the charging voltage of the charging capacitor changes, the charging characteristics such as charging efficiency and charging time are constant if the driving frequency and the duty ratio are constant. There was a problem that was not improved.
[0007]
The present invention has been made in view of the above points, and an object of the present invention is to provide a charging circuit device that can improve charging efficiency and charging characteristics of a charging capacitor.
[0008]
[Means for Solving the Problems]
The invention according to claim 1 is connected to a converter transformer, a battery, switching means for opening and closing a current flowing from the battery to a primary coil of the converter transformer, and a rectifier to a secondary coil of the converter transformer. It is characterized by comprising a charging capacitor and control means for varying a drive frequency for opening and closing the switching means according to a charging voltage of the charging capacitor.
[0009]
According to a second aspect of the present invention, the control means according to the first aspect controls opening and closing of the switching means by increasing the driving frequency in an early stage of charging, decreasing the driving frequency in a middle stage of charging, and increasing the driving frequency in a final stage of charging. It is characterized by doing.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment in which the present invention is applied to a circuit for charging a charging capacitor, which is a driving source of a strobe flash of a camera.
[0011]
In FIG. 1, reference numeral 11 denotes a battery for supplying a DC voltage E. The anode of this battery 11 is connected to one end of a primary coil of a converter transformer 13 via a charging switch 12. The other end of the primary coil is connected to the cathode of the battery 11 via an FET (field effect transistor) 14 as switching means. Note that a protection capacitor C1 is connected to both ends of a series connection body composed of the battery 11 and the charging switch 12.
[0012]
One end of a secondary coil of the converter transformer 13 is connected to one end of a charging capacitor C2 via a rectifying diode D1. The other end of the charging capacitor C2 is connected to the other end of the secondary coil of the converter transformer 13 and to the cathode of the battery 11. The charging voltage V charged in the charging capacitor C2 is supplied as a drive source of a flash (not shown) of the camera. In this embodiment, the winding ratio and the like of the converter transformer 13 are determined so that the charging capacitor C2 is charged to, for example, 300 V when fully charged.
[0013]
The charging voltage V charged in the charging capacitor C2 is input to the controller 15. The controller 15 is mainly composed of, for example, a microprocessor, and includes a voltage detection circuit 15a for detecting a charging voltage V, a ROM (Read Only Memory) and a RAM (Random Access Memory), as shown in FIG. A map 15b for determining the driving frequency f with respect to the charging voltage V is provided. Further, the controller 15 determines the driving frequency f of the charging voltage V charged in the charging capacitor C2 detected by the voltage detecting circuit 15a with reference to the map of FIG. 2, and controls the opening and closing of the FET 14 at the driving frequency f. It has control means.
[0014]
Next, the operation of the embodiment of the present invention configured as described above will be described. First, when charging the charging capacitor C2, the charging switch 12 is closed. The charging voltage V of the charging capacitor C2 is detected by the voltage detection circuit 15a. The controller 15 determines the driving frequency f of the charging voltage V charged in the charging capacitor C2 detected by the voltage detecting circuit 15a with reference to the map of FIG. 2, and controls the opening and closing of the FET 14 at the driving frequency f.
[0015]
When the FET 14 is controlled to open and close at the drive frequency f, a current flows intermittently at the drive frequency f in the primary coil of the converter transformer 13. Accordingly, an induced voltage having a drive frequency f is generated at both ends of the secondary coil of the converter transformer 13. This induced voltage is rectified via the diode D1 and supplied to the charging capacitor C2. As a result, the charging capacitor C2 is charged. The charging voltage V of the charging capacitor C2 rises with time and rises to 300V.
[0016]
The charging voltage V of the charging capacitor C2 is detected by the voltage detection circuit 15a. The controller 15 determines the drive frequency f from the charge voltage V with reference to the map of FIG. 2 and controls the opening and closing of the FET 14 at the drive frequency f.
[0017]
Therefore, the controller 15 increases the driving frequency f at the beginning of charging when the charging switch 12 is closed because the charging voltage V is low, increases the driving frequency f during the middle period of charging, and increases the driving frequency f at the end of charging. To control.
[0018]
As described above, the driving frequency f is controlled in accordance with the charging voltage V of the charging capacitor C2. Therefore, in the initial stage of charging, the charging efficiency can be understood from the relationship between the driving frequency f and the charging efficiency as shown in FIG. Can be improved.
[0019]
Further, in the middle period of the charging, the driving frequency f is lowered, thereby suppressing the charging loss in the charging capacitor C2, thereby shortening the charging time. This is because, as shown in FIG. 3, when the driving frequency f decreases from 135 kHz to 105 kHz, the charging loss is suppressed, and the charging time is shortened. Therefore, charging characteristics such as charging time can be improved. Further, in the latter half of the charging, the charging efficiency can be improved by increasing the driving frequency f.
[0020]
In the above-described embodiment, the driving frequency f with respect to the charging voltage V is changed stepwise as shown in FIG. 2, but the present invention is not limited to this. For example, it may be changed in a curved line as shown by a broken line in FIG. The point is that the drive frequency f may be changed according to the charging voltage V so as to improve the charging efficiency.
[0021]
Further, in the above-described embodiment, the drive frequency f is determined with reference to the map 15b. However, in the controller 15, the charging voltage V is compared with a reference charging voltage range. Software processing may be performed to set a predetermined drive frequency f. Also in this case, as in the above-described embodiment, the driving frequency f is high in the early stage of charging when the charging switch 12 is closed, the driving frequency f is low in the middle period of charging, and the driving frequency f is high in the last stage of charging. It should be set as follows.
[0022]
In the above-described embodiment, the FET 14 is used as the switching means. However, the present invention is not limited to this, and an IGBT may be used.
[0023]
Further, in the above-described embodiment, the drive frequency f is controlled. However, the present invention is not limited to this, and the duty ratio in the case of controlling the opening and closing of the FET 14 may be controlled. That is, in the initial stage of charging when the charging switch 12 is closed, the on-duty ratio of the signal for controlling the opening and closing of the FET 14 is set small, the on-duty ratio is increased in the middle stage of charging, and the on-duty ratio is decreased in the end stage of charging. Good.
[0024]
Further, in the above embodiment, the voltage detection circuit 15a is provided in the controller 15, but may be provided outside the controller 15. If the function of the controller 15 is mounted on a microcomputer provided in a digital camera or the like, a charging circuit device with improved charging efficiency without adding a special hardware configuration other than the voltage detection circuit 15a is provided. can do.
[0025]
【The invention's effect】
As described above in detail, according to the present invention, there is provided a charging circuit device capable of improving the charging efficiency and charging characteristics of the charging capacitor because the driving frequency is changed according to the charging voltage of the charging capacitor. be able to.
[0026]
In particular, the charging efficiency and the charging characteristics can be further improved by controlling the driving frequency f to be high in the early stage of charging, lowering the driving frequency f in the middle stage of charging, and increasing the driving frequency f in the last stage of charging.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a charging circuit device according to one embodiment of the present invention.
FIG. 2 is a map showing a relationship between a charging voltage V and a driving frequency f according to the embodiment.
FIG. 3 is a diagram showing a relationship between a driving frequency f and charging efficiency according to the embodiment.
[Explanation of symbols]
11: battery, 12: charging switch, 13: converter transformer, 14: FET, 15: controller, 15a: voltage detection circuit, 15b: map.

Claims (2)

  1. A converter transformer,
    Battery and
    Switching means for opening and closing a current flowing from the battery to the primary coil of the converter transformer;
    A charging capacitor connected to a secondary coil of the converter transformer via a rectifying element,
    Control means for varying a drive frequency for opening and closing the switching means in accordance with the charging voltage of the charging capacitor.
  2. 2. The charging device according to claim 1, wherein the control unit controls the switching unit to open and close by increasing the driving frequency in an early stage of charging, lowering the driving frequency in a middle stage of charging, and increasing the driving frequency in a last stage of charging. Circuit device.
JP2003140815A 2003-05-19 2003-05-19 Charging circuit device Pending JP2004343968A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2003140815A JP2004343968A (en) 2003-05-19 2003-05-19 Charging circuit device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2003140815A JP2004343968A (en) 2003-05-19 2003-05-19 Charging circuit device

Publications (1)

Publication Number Publication Date
JP2004343968A true JP2004343968A (en) 2004-12-02

Family

ID=33529426

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2003140815A Pending JP2004343968A (en) 2003-05-19 2003-05-19 Charging circuit device

Country Status (1)

Country Link
JP (1) JP2004343968A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008529471A (en) * 2005-01-25 2008-07-31 パーキンエルマー シンガポール プライベート リミティド Digital pulse controlled capacitor charging circuit

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008529471A (en) * 2005-01-25 2008-07-31 パーキンエルマー シンガポール プライベート リミティド Digital pulse controlled capacitor charging circuit

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