JP2010193629A - Charge control apparatus and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten the charging time in charging a battery at low temperature using a low charge current. <P>SOLUTION: A charge control apparatus includes a control circuit for charging a battery by switching from a constant-current charging mode for charging, by feeding a constant current to a battery from a charging circuit to a constant-voltage charging mode for charging, by applying a constant voltage to the battery from the charging circuit, and a temperature detecting device for detecting the temperature of the battery. The control circuit conducts charging at a predetermined constant current at a high temperature, when the temperature detecting device detects a predetermined high temperature in the constant-current charge mode. When the temperature detecting device detects a predetermined low temperature which is lower than the predetermined high temperature, charging is carried out at a predetermined constant current at low temperature lower than the predetermined current at high temperature, and charging is controlled, in response to the temperature detected by the temperature-detecting device in the constant-voltage charging mode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a battery charge control device and a camera equipped with the charge control device.

  2. Description of the Related Art There is known a charge control device that switches charge control according to temperature.

Japanese Patent Laid-Open No. 05-049184

  However, in the conventional charge control device, when the battery temperature is low, the charging current is simply lowered, so that there is a problem that the charging time becomes long.

(1) The invention of claim 1 is a constant voltage charging mode in which charging is performed by applying a constant voltage from the charging circuit to the battery from a constant current charging mode in which charging is performed by supplying a constant current from the charging circuit to the battery. A control circuit that performs charging by switching to a temperature detector and a temperature detector that detects the temperature of the battery. When the predetermined high temperature is detected by the temperature detector in the constant current charging mode, the control circuit When charging is performed at a constant current and a predetermined low temperature lower than a predetermined high temperature is detected by the temperature detector, charging is performed at a constant current at a low temperature lower than a predetermined current at a high temperature, and a constant voltage charging mode The control according to the temperature detected by the temperature detector is performed.
(2) According to a second aspect of the present invention, in the charge control device according to the first aspect, the reference current for determining the end of charging in the constant voltage charging mode is determined according to the charging current in the constant current charging mode. When the predetermined low temperature is detected by the temperature detector, the control circuit changes the charging current in the constant current charging mode to a value higher than the predetermined current at the low temperature during charging in the constant voltage charging mode.
(3) The invention according to claim 3 is the charge control device according to claim 1 or 2, wherein the control circuit does not end charging even if a predetermined charging time limit has elapsed after starting charging. Is determined to be abnormal, and charging is stopped. However, when a predetermined low temperature is detected by the temperature detector, the predetermined charging time limit is extended.
(4) The invention of claim 4 is a camera that uses a rechargeable battery as a power source, and includes the charge control device according to any one of claims 1 to 3 and is a camera that charges the battery. .

  According to the present invention, it is possible to prevent an unnecessarily long charging time even if a battery in a low temperature state is charged with a low charging current.

The figure which shows the structure of the charge control apparatus of one embodiment. The flowchart which shows the charge control program of one embodiment Timing chart of charge control according to one embodiment The figure which shows the structure of the camera carrying the charge control apparatus of one embodiment.

  FIG. 1 is a diagram illustrating a configuration of a charge control device 1 according to an embodiment. The AC adapter 2 includes a rectifier (not shown), a smoothing capacitor, and the like, and rectifies and smoothes a commercial AC power supply (for example, AC 100 V) for output. The AC adapter 2 may be provided with a step-down function using a transformer or the like. The charging circuit 3 includes a switching transformer (not shown), a switching element, a PWM control circuit, a noise absorption / smoothing circuit, a battery holder, etc., and steps down the DC power output from the AC adapter 2 to a predetermined charging voltage and smoothes the battery 4 Apply to. The battery 4 may be of any kind as long as it can be charged. In this embodiment, a lithium ion battery will be described as an example. The temperature sensor 5 detects the temperature T of the battery 4. The charging control circuit 6 includes a CPU 6a, a memory 6b, and the like, and controls charging start, stop, charging mode, charging voltage, charging current, charging time, and the like by the charging circuit 4 based on the temperature of the battery 4.

  FIG. 2 is a flowchart showing a charge control program according to an embodiment, and FIG. 3 is a timing chart of the charge control according to the embodiment. The charge control operation of the embodiment will be described with reference to these drawings. When a power switch (not shown) is turned on, the CPU 6a of the charge control circuit 6 executes a charge control program (see FIG. 2) stored in the memory 6b every predetermined time. In step 1 of FIG. 2, the temperature sensor 5 detects the temperature T of the battery 4 to be charged attached to the battery holder (not shown). In subsequent step 2, it is determined whether or not the detected battery temperature T is within a predetermined allowable charging temperature range (in this embodiment, for example, 0 ° C. ≦ T ≦ 50 ° C.). When the temperature is not within the allowable charging temperature range, that is, when the temperature is lower than 0 ° C. or higher than 50 ° C., the charging is not started, and the process returns to step 1 to detect the battery temperature again.

  If it is determined that the battery temperature T is within the allowable charging temperature range, the process proceeds to step 3, and whether or not the battery temperature T is in a predetermined low temperature state (for example, 0 ° C. ≦ T ≦ 10 ° C. in this embodiment). Is determined. If it is in a low temperature state, the process proceeds to step 6; otherwise, the process proceeds to step 4. If the detected battery temperature T is within the allowable charging temperature range but is not in a low temperature state (10 ° C. <T ≦ 50 ° C.), a predetermined charging current at a high temperature in step 4 (in this embodiment) For example, charging according to 1C) is started. On the other hand, if the detected battery temperature T is within the allowable charging temperature range and is in a low temperature state (0 ° C. ≦ T ≦ 10 ° C.), the timer (software timer by the CPU 6a) is extended in step 6 (details) In a subsequent step 7, charging at a predetermined charging current (for example, 0.5 C in this embodiment) at a low temperature lower than the predetermined charging current at the high temperature is started. Here, the current value for charging and discharging the entire capacity of the battery over 1 hour is referred to as 1C rate.

  FIG. 3 shows a change (a) in the voltage VBAT [V] of the battery 4 and a change (b) in the charging current Icharge [C] during charging by the charging control according to the embodiment. The charging control apparatus 1 according to the embodiment performs charging by switching three kinds of charging modes in the order of trickle charging mode, high-speed charging mode, and constant voltage charging mode. The trickle charging mode (also referred to as a preliminary charging mode) is a charging mode for performing charging with a small charging current and confirming whether the battery 4 is normal before performing full-scale charging. Then, charging is performed by limiting the charging current to 1/10 of the charging current Icharge in the high-speed charging mode. Therefore, when the battery temperature T is in a high temperature state, it is limited to 0.1C which is 1/10 of 1C, and when it is in a low temperature state, it is limited to 0.05C which is 1/10 of 0.5C. Charge the battery.

  If the voltage VBAT of the battery 4 rises to a predetermined voltage (for example, 2.9 V in this embodiment) within a predetermined time from the start of trickle charging, it is determined that the battery 4 is normal and a transition is made to the next high-speed charging mode. To do. If the voltage VBAT of the battery 4 does not rise to the predetermined voltage even after a predetermined time has elapsed since the start of charging in the trickle charge mode, the charged battery 4 is abnormally charged and a warning is given.

  In the fast charge (constant current charge) mode, the battery 4 is charged with a constant charge current Icharge. In this embodiment, charging is performed at a constant charging current Icharge corresponding to the temperature T of the battery 4. When the temperature T of the battery 4 is in a high temperature state (10 ° C. <T ≦ 50 ° C.), for example, charging is performed at a constant 1 C, and when the temperature T of the battery 4 is in a low temperature state (0 ° C. ≦ T ≦ 10 ° C.) The battery is charged at a constant 0.5 C, for example, lower than the charging current 1 C in the high temperature state. The charging current in the high-speed charging mode is not limited to the value of this embodiment, but a lower charging current is set when the battery temperature T is in the low temperature state than in the high temperature state.

  After charging is started at a constant charging current Icharge corresponding to the battery temperature T in the fast charging (constant current charging) mode, the voltage VBAT of the battery 4 reaches a predetermined voltage (4.2 V in this embodiment). Transition to constant voltage (constant voltage charge) mode. In the charging characteristics shown in FIG. 3A, the voltage VBAT of the battery 4 reaches the predetermined charging voltage 4.2V at time t3. In the constant voltage mode, charging is performed at a predetermined charging voltage, here, constant 4.2 V, and control according to the temperature T of the battery 4 is performed.

  In a charge control IC generally used for a charge control device, a charge current Icharge that is a criterion for determining whether to end charging in the constant voltage mode is automatically set at a predetermined ratio to a set value of the charge current Icharge in the fast charge mode. For example, as described above, when the charging current Icharge in the high-speed charging mode is 1C, it is set to 0.1C which is 1/10. Therefore, the smaller the current value is set for the charging current Icharge in the fast charge mode, the smaller the charging current Icharge that becomes the reference for determining the end of charging, and therefore the time required to reach the reference current for determining the end of charging becomes unnecessarily long. Therefore, in this embodiment, the battery temperature T is in a low temperature state (0 ° C. ≦ T ≦ 10 ° C.), and constant current charging is performed by setting a small charging current Icharge, for example, 0.5 C, in the fast charge mode. In the subsequent constant voltage charging mode, the set value of the charging current Icharge in the fast charging mode is changed to a large value. In the above example, the setting is changed from 0.5C to 1C. As a result, it is possible to prevent the charging current from being changed from 0.05 C to 0.1 C in the constant voltage charging mode, thereby preventing the charging time from becoming unnecessarily long.

  Further, in this embodiment, when the completion of charging is not determined within a predetermined time from the start of charging, it is determined that charging is abnormal, and charging is terminated and a warning is issued. In this case, when the battery 4 is in a low temperature state, there is a case where a low value is set for the charging current Icharge that is a reference for the charging end determination. Therefore, even if the charging current setting change in the above-described fast charging mode is performed There is a possibility that the time until is issued becomes longer. Therefore, as shown in FIG. 3, when the battery temperature T is in a low temperature state, the charge limit time set to 4 hr by normal charge control is extended to, for example, 6 hr, and from the start of charging at time t1 to time t6 after 6 hr. If it is not determined that the charging is complete, the charging is terminated and a warning of abnormal charging is issued.

  After starting charging with the charging current 1C assuming that the battery temperature T is not in a low temperature state, it is determined in step 5 of FIG. 2 whether or not the charging current Icharge has become 0.1 C or less. Complete charging. In the charging completion determination in step 5, it is determined that the charging current Icharge has become 0.1 C or less after a predetermined time has elapsed since the start of charging at 1 C, assuming that the battery is not in a low temperature state, and the charging is determined to be complete after the predetermined time has elapsed. Note that a current sensor that detects the charging current Icharge that flows through the battery 4 may be installed, and the charging current Icharge that actually flows through the battery 4 may be measured and determined.

  On the other hand, after the battery temperature T is in a low temperature state and charging with a charging current of 0.5 C is started, it is determined in step 8 of FIG. When the charging voltage VBAT of the battery 4 reaches a predetermined voltage, that is, 4.2 V in this case and shifts to the constant voltage mode, the process proceeds to step 9. In step 9, the charging current Icharge in the fast charging mode is changed from 0.5C to 1C, for example. Next, in step 10, as described above, it is determined whether or not the charging current Icharge has become 0.1 C or less based on the elapse of a predetermined time.

  As shown in FIG. 3, as the setting value of the charging current Icharge in the high-speed charging mode is changed to a large value (here, 0.5C → 1C), the charging current that is a criterion for determining the end of charging is automatically set. When the setting is not changed, the charging time required until time t6 is shortened to time t4. In addition, when charging is performed until time t6 without changing the setting of the charging current, the charging capacity increases by that amount, but the increase is slight, and the advantage is that charging is performed until the charging time is extended. Is smaller than the advantage of shortening the charging time.

  You may mount the charge control apparatus 1 of one Embodiment mentioned above in various cameras. FIG. 4 is a diagram showing the configuration of the camera 10 equipped with the charge control device according to the present invention. The accumulation control circuit 11 controls charge accumulation of the image sensor 12, reading of an image signal, and the like. The image sensor 12 is composed of an image sensor such as a CCD or a CMOS, and outputs an image signal of a subject image formed on an imaging surface by a photographing optical system (not shown). The signal processing circuit 13 performs various processes on the image signal of the subject image read from the image sensor 12. The operation member 14 is a member for operating the camera, such as a camera power switch, a shutter release switch, a shooting mode selector, a direction key switch, and the operation signal of each member is input to the controller 16 via the input circuit 15. . The controller 16 includes a CPU 16a and a memory 16b, and performs charging control of the battery 23 in addition to various calculation control and sequence control of the camera. The display control circuit 17 displays an image and various information on the monitor 18, and the recording control circuit 19 records the image on a removable recording medium 20 such as a memory card. The lens drive control circuit 21 adjusts the focus by driving a focusing lens (not shown) of the photographing optical system.

  The temperature sensor 22 detects the temperature T of the battery 23 mounted on the camera. The battery 23 is a rechargeable battery such as a lithium ion battery, and supplies power to devices and circuits mounted on the camera 10. The charging circuit 24 includes a switching transformer, a switching element, a PWM control circuit, a noise absorption / smoothing circuit, etc., not shown, and steps down the DC power output from the AC adapter 25 to a predetermined charging voltage and applies it to the battery 23. . The AC adapter 25 is an external device connected to the camera 10, and includes an unillustrated transformer, rectifier, smoothing capacitor, and the like. The AC adapter 25 rectifies and smoothes a commercial AC power supply (for example, AC 100 V) and supplies it to the charging circuit 24 of the camera 10.

  The CPU 16a of the controller 16 executes the charge control 1 and charge control 2 programs stored in advance in the memory 16b independently or alternately, and based on the temperature T of the battery 23 detected by the temperature sensor 22, the charging circuit 24, the battery 23 is charged. The operation of this charging control is the same as the operation described with reference to FIGS.

  In the above-described embodiments and their modifications, all combinations of the embodiments and the modifications are possible.

  According to the above-described embodiment and its modifications, the following operational effects can be achieved. First, charging is performed by applying a constant voltage from the charging circuits 3 and 24 to the batteries 4 and 23 from the constant current charging mode in which charging is performed by supplying a constant current from the charging circuits 3 and 24 to the batteries 4 and 23. Charge control circuits 6 and 16 that perform charging by switching to the constant voltage charging mode and temperature sensors 5 and 22 that detect the temperature T of the batteries 4 and 23 are provided. The charging control circuits 6 and 16 are in the constant current charging mode. When a predetermined high temperature is detected by the temperature sensors 5 and 22, charging is performed at a predetermined current at a high temperature, and when a predetermined low temperature lower than the predetermined high temperature is detected by the temperature sensors 5 and 22, the high temperature is detected. In the constant voltage charging mode, charging is performed at a constant current lower than the predetermined current, and control according to the temperature detected by the temperature sensors 5 and 22 is performed. Even when charging the battery at a low charging current can be prevented from charging time unnecessarily longer.

  In addition, according to one embodiment and its modification, when a predetermined low temperature is detected by the temperature sensors 5 and 22, the charging current in the constant current charging mode is changed during the charging in the constant voltage charging mode. Since the current is changed to a value higher than the predetermined current, when the reference current for determining the end of charging is automatically set according to the charging current in the constant current charging mode, the battery in the low temperature state is charged with a low charging current. Even so, it is possible to prevent unnecessarily long charging time.

DESCRIPTION OF SYMBOLS 1; Charge control apparatus, 2,25; AC adapter, 3,24; Charge circuit, 4,23; Battery, 5,22; Temperature sensor, 6: Charge control circuit, 10; Camera, 16;

Claims (4)

A control circuit for charging by switching from a constant current charging mode in which a constant current is supplied to the battery from the charging circuit to a constant voltage charging mode in which a constant voltage is applied from the charging circuit to the battery for charging. When,
A temperature detector for detecting the temperature of the battery,
In the constant current charging mode, the control circuit performs charging at a constant current at a high temperature when a predetermined high temperature is detected by the temperature detector, and performs a predetermined charge lower than the predetermined high temperature by the temperature detector. When a low temperature is detected, charging is performed at a constant current at a low temperature lower than a predetermined current at the high temperature, and control according to the temperature detected by the temperature detector is performed in the constant voltage charging mode. A charge control device characterized by performing. The charge control device according to claim 1,
The reference current for determining the end of charging in the constant voltage charging mode is determined according to the charging current in the constant current charging mode,
When the predetermined low temperature is detected by the temperature detector, the control circuit sets the charging current in the constant current charging mode to a value higher than the predetermined current at the low temperature during charging in the constant voltage charging mode. A charge control device characterized by changing to In the charge control device according to claim 1 or 2,
If the charging does not end even after a predetermined charging time limit has elapsed since the start of charging, the control circuit determines that there is an abnormality and stops charging. However, the temperature detector detects the predetermined low temperature. The charging control device extends the predetermined charging time limit. A camera powered by a rechargeable battery,
A camera comprising the charge control device according to claim 1, wherein the battery is charged.

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