JP2010057247A - Charging device and charging control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly charge a battery pack without decreasing the chargeable capacity of the battery pack even when the necessity of decreasing the charging voltage occurs due to the change in temperature of the battery pack during charging. <P>SOLUTION: The charging device includes a charging voltage switching means for switching a charging voltage to be applied to the battery pack between a first charging voltage and a second charging voltage lower than the first charging voltage; a switch for switching the charging voltage between a state of applying the voltage to the battery pack and a state of not applying; and a voltage measuring means for measuring the voltage of the battery pack. In the charging device, when switching the charging voltage from the first charging voltage to the second charging voltage, the charging voltage switching means causes the switch to bring a state of not applying the first charging voltage to the battery pack and causes the switch to bring a state of applying the second charging voltage after the voltage of the battery pack becomes lower than the second charging voltage. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a charging device and a charging control method for charging a battery pack incorporating a secondary battery cell.

2. Description of the Related Art A charging device that changes a charging voltage and charges a battery pack that incorporates a secondary battery cell is known.
JP-A-11-275772

  As a recent trend of battery packs, miniaturization and high capacity have progressed, and safer charging methods for battery packs have been proposed.

  For example, a charge control method has been proposed in which a temperature measuring element such as a thermistor is provided in a battery pack and an appropriate charging voltage and charging current are set for each charging temperature range.

  In the case of such a control method, if it is necessary to control the charging voltage to be lowered during charging, if charging is performed in a state where the voltage of the battery pack is higher than the charging voltage, a backflow occurs from the battery pack to the charging device. In some cases, the charging device malfunctions.

  Therefore, in order to avoid malfunction of the charging device due to backflow from the battery pack, a method of preventing backflow from the battery pack to the charging device using a backflow prevention element such as a diode has been used.

  However, this method has a problem that the charging efficiency is lowered due to the loss of the backflow prevention element.

  In addition, the thermistor in the battery pack is warmed by the heat generated by the backflow prevention element, which increases the measurement error of the battery pack internal temperature. In addition, the use of the backflow prevention element is disadvantageous in terms of cost.

  There is also a method in which charging is terminated when the voltage of the battery pack is higher than the charging voltage without using the backflow prevention element.

  In this method, when the voltage of the battery pack is measured after stopping charging to switch the charging voltage, the battery pack is charged until just before it, so the voltage of the battery pack is measured high, and it is still charged. Instead, the charging is completed.

  Therefore, there has been a problem that the actual charge capacity is smaller than the chargeable capacity of the battery pack.

  The present invention has been made in view of such problems, and its purpose is to reduce the charge capacity of the battery pack without using a backflow prevention element even when charging is performed by lowering the charging voltage. The object is to provide a charging device that does not decrease.

  To achieve the above object, a charging device of the present invention is a charging device for charging a battery pack, wherein a charging voltage applied to the battery pack is lower than a first charging voltage and the first charging voltage. Charging voltage switching means for switching the charging voltage of the battery pack, a switch for switching the charging voltage to a state in which the charging voltage is applied to the battery pack, a voltage measuring means for measuring the voltage of the battery pack, and the charging voltage in the first state. When switching from one charging voltage to the second charging voltage, the charging voltage switching means does not apply the first charging voltage to the battery pack by the switch, and the voltage of the battery pack is set to the second charging voltage. The second charging voltage is applied to the battery pack by the switch after the charging voltage drops below the charging voltage. Characterized by a state.

  The charge control method of the present invention is a charge control method for charging a battery pack by switching a charge voltage between a first charge voltage and a second charge voltage lower than the first charge voltage, wherein the charge voltage is A step of not applying the first charging voltage to the battery pack when switching from the first charging voltage to the second charging voltage; a step of measuring a voltage of the battery pack; And a state in which the second charging voltage is applied to the battery pack after the voltage of the pack has dropped below the second charging voltage.

  When it is necessary to lower the charging voltage during charging, charging can be started after the voltage of the battery pack drops below the charging voltage, no backflow prevention element is required, and the charging capacity of the battery pack is reduced. It became possible to charge without dropping.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is an example of a charging device according to an embodiment of the present invention. The charging device 5 shown in FIG. 1 is a charging device that charges the battery pack of the present invention.

  The battery pack 1 has a + terminal (+) 2, a temperature terminal (T) 3, and a − terminal (−) 4. The temperature terminal (T) 3 is an output terminal that outputs the temperature of the battery pack 1. The charging device 5 includes a + terminal (+) 6, a temperature terminal (T) 7, and a − terminal (−) 8 as terminals corresponding to the terminals of the battery pack 1.

  These corresponding terminals are connected to each other by mounting the battery pack 1 on the mounting portion 9 of the charging device 5. Electric power for charging by the charging device 5 can be supplied from a home AC power source via the AC cord 10 and the AC plug 11. When the battery pack 1 is attached to the charging device 5, the charging device 5 starts charging the battery pack 1.

  Whether or not the battery pack 1 is connected to the charging device 5 is determined by whether or not the thermistor 133 is connected to the temperature terminal 7.

  The thermistor 133 is connected between the temperature terminal 3 and the minus terminal 4 of the battery pack 1 and functions as temperature measuring means for the battery pack 1 as described later (see FIG. 2).

  The voltage (charging voltage) of the battery pack 1 being charged is detected by a charging control microcomputer 125 (see FIG. 2) built in the charging device 5. The charging control microcomputer 125 controls the charging voltage so that the charging voltage is set for each temperature.

  The value of the charging voltage is stored in advance in a memory in the charging control microcomputer 125 in association with the temperature information (see FIG. 3).

  For example, when the battery pack temperature decreases from the normal charging range to the low temperature charging range, the charging control microcomputer 125 performs an operation of decreasing from the first charging voltage 4.2V to the second charging voltage 4.0V. The charge control microcomputer 125 functions as a charge voltage switching unit.

  At this time, the charge control microcomputer 125 detects the battery pack voltage, compares the battery pack voltage with the low-temperature charging voltage, and resumes charging when the voltage of the battery pack drops below the low-temperature charging voltage. The charge control microcomputer 125 functions as a voltage measurement unit.

  Similarly, when the battery pack temperature rises from the normal charging range to the high temperature charging range, the charging control microcomputer 125 performs an operation of decreasing the first charging voltage 4.2V to the third charging voltage 4.1V.

  At this time, the charging control microcomputer 125 detects the battery pack voltage, compares the battery pack voltage with the charging voltage for high temperature charging, and resumes charging when the voltage of the battery pack drops below the high temperature charging voltage.

  FIG. 2 is a block diagram showing the configuration of the electric circuit of the present invention. In the present embodiment, general configurations that are not necessary for the contents of the present invention are not shown.

  Reference numeral 101 denotes a charging device, 102 denotes an AC input unit, 103 denotes a primary power supply circuit, 104 denotes a transformer, 105 denotes a photocoupler, 106 denotes a secondary smoothing circuit, and 107 denotes a regulator. Reference numerals 108, 111, 112, 114, 116, 118, 121, 122, 123, and 124 denote resistors.

  Reference numerals 109 and 110 denote operational amplifiers, 113 denotes a volume, and 115 and 117 denote switches. Reference numeral 119 denotes a trickle charge switch, and 120 denotes a quick charge switch. Reference numeral 125 denotes a charge control microcomputer. Reference numeral 126 denotes a + terminal of the charging apparatus 101, 127 denotes a temperature terminal of the charging apparatus 101, and 128 denotes a − terminal of the charging apparatus 101.

  129 is a battery pack, 130 is a + terminal, 131 is a temperature terminal, 132 is a − terminal, 133 is a thermistor, and 134 is a secondary battery cell (hereinafter abbreviated as a cell).

  When AC power is input to the AC input unit 102, the AC power is supplied to the transformer 104 via the primary power supply circuit 103. The transformer 104 performs voltage conversion from the primary side high voltage to the secondary side low voltage, and also separates the primary side and secondary side GND lines.

  The secondary output of the transformer 104 is rectified by the secondary smoothing circuit 106 and output to the subsequent charge control circuit. The regulator 107 stabilizes the output voltage of the secondary smoothing circuit 106 to a constant voltage.

  The secondary side voltage of the transformer 104 is divided by a voltage feedback resistor 112 and a volume 113 for adjusting the maximum value of the charging voltage. The secondary voltage of the transformer 104 is controlled via the operational amplifier 109 and the photocoupler 105.

  The output voltage of the regulator 107 is supplied to the temperature terminal 127 of the charging device 101 via the resistor 121. When the battery pack 129 is connected to the charging device 101, a voltage obtained by dividing the output voltage of the regulator 107 by the resistor 121 and the thermistor 133 is generated at the temperature terminal 131 of the battery pack 129.

  The charge control microcomputer 125 detects the mounting of the battery pack 129 by detecting the voltage divided by the resistor 121 and the thermistor 133 via the temperature terminal 127, and starts charging control to the battery pack 129. To do.

  Since the resistance value of the thermistor 133 varies depending on the internal temperature of the battery pack 129, the thermistor 133 is also used as a temperature sensor for the battery pack 129. The charging device 101 determines a charging voltage for charging the battery pack 129 based on the internal temperature of the battery pack 129 detected by the thermistor 133.

  The charge control microcomputer 125 measures the charge voltage via the resistors 122 and 123. The charging control microcomputer 125 measures the charging voltage of the battery pack 129 when detecting the mounting of the battery pack 129 based on the voltage at the temperature terminal 127.

  The trickle charging is performed by supplying a charging current limited by the resistor 118 to the battery pack 129. This trickle charge is performed when the voltage of the battery pack 129 is less than the voltage at which quick charge is possible, and is terminated when the voltage at which quick charge is possible is reached.

  The quick charge is performed by turning on the quick charge switch 120. In the quick charge, in the initial stage of charging, constant current charging for supplying a constant charging current to the battery pack 129 is performed, and thereafter, constant voltage charging for supplying a constant charging voltage is performed.

  The charging current value is converted into a voltage level via the resistor 124. The charging current value is determined by a voltage value obtained by dividing the output voltage of the regulator 107 by the resistors 108 and 111.

  The charging current value is controlled via the operational amplifier 110 and the photocoupler 105.

  The charging control microcomputer 125 stores an appropriate charging voltage value of the battery pack 129 in a built-in memory (not shown). That is, the charging control microcomputer 125 detects the internal temperature of the battery pack 129 during the rapid charging, and determines the charging voltage value according to the detected internal temperature.

  When the temperature of the battery pack 129 detects the normal charging range, the charging control microcomputer 125 sets the charging voltage to the normal charging voltage of 4.2 V (first charging voltage). When the charging control microcomputer 125 sets the charging voltage to the normal charging voltage of 4.2 V, the switch 115 and the switch 117 are turned off.

  The charging control microcomputer 125 turns on the switch 120 to perform quick charging. For example, when the charge control microcomputer 125 detects a change in the temperature of the battery pack 129 from the normal charging range to the low temperature charging range, the quick charging switch 120 is turned off and the voltage of the battery pack 129 is measured.

  The charge control microcomputer 125 starts a timer. The timer value is set to such a time that the voltage of the battery pack 129 is stabilized after the quick charge switch 120 is turned off. The charge control microcomputer 125 functions as a time measuring means for measuring the elapsed time since the charging was interrupted.

  Rapid charging is not resumed when the battery pack 129 exceeds the charging voltage for low-temperature charging. If the voltage of the battery pack 129 does not drop to the low-temperature charging voltage even after the timer time (predetermined time) has elapsed, the charging is terminated.

  When the voltage of the battery pack 129 is lower than the charging voltage for low-temperature charging, the charging control microcomputer 125 sets the charging voltage for low-temperature charging to 4.0 V (second charging voltage).

  For example, in the case of low-temperature charging, the charging voltage value is set by a resistor 114 and a switch 115 connected to the middle point of the resistor 112 and the volume 113.

  When the charging control microcomputer 125 sets the charging voltage to the low temperature charging voltage, the switch 115 is turned on to connect the resistor 114 and the volume 113 in parallel.

  The charge control microcomputer 125 turns on the quick charge switch 120 to restart the quick charge. Similarly, when the charge control microcomputer 125 detects a change in the temperature of the battery pack 129 from the normal charge range to the high temperature charge range, the quick charge switch 120 is turned off and the voltage of the battery pack 129 is measured.

  The charge control microcomputer 125 starts a timer (not shown). When the battery pack 129 is equal to or higher than the charging voltage for high-temperature charging, rapid charging is not resumed.

  If the voltage of the battery pack 129 does not drop to the high-temperature charging voltage even after the timer has elapsed, the charging is terminated.

  When the voltage of the battery pack 129 is less than the charging voltage for high temperature charging, the charging control microcomputer 125 sets the charging voltage for the high temperature charging to 4.1V.

  The charging voltage value in the case of high-temperature charging is set by a resistor 116 and a switch 117 connected to the middle point of the resistor 112 and the volume 113.

  When the charging control microcomputer 125 sets the charging voltage to high temperature charging, the switch 117 is turned on to connect the resistor 116 and the volume 113 in parallel.

  The charge control microcomputer 125 turns on the quick charge switch 120 to restart the quick charge.

  The charging control microcomputer 125 measures the charging current by detecting the potential difference of the resistor 124 that converts the charging current value into a voltage level.

  The charging control microcomputer 125 detects an increase in charging voltage and a decrease in charging current during the rapid charging, and determines whether or not to terminate the rapid charging based on the degree of the increase and decrease.

  The charge control microcomputer 125 constantly measures the values of the charging voltage and the charging current, and ends the charging of the battery pack 129 when detecting the setting value for the end of charging.

  In the present embodiment, as an example of a method for setting the charging voltage value, the charging control microcomputer 125 sets the charging voltage using a resistor connected in parallel to the volume 113. However, other charging voltages are set. The effect of the present invention can be expected by the setting method.

  Next, a control example of the charging voltage for each temperature will be described with reference to FIG.

When the battery pack temperature is less than 0 ° C., charging is waited until the temperature reaches 0 ° C. or higher (low temperature standby).
When the battery pack temperature is from 0 ° C. to 10 ° C., the charging voltage is 4.0 V (low temperature charging).
When the battery pack temperature is from 10 ° C. to 45 ° C., the charging voltage is 4.2 V (normal charging).
When the battery pack temperature is 45 ° C. to 55 ° C., the charging voltage is 4.1 V (high temperature charging).
When the battery pack temperature exceeds 55 ° C., charging is waited until the temperature becomes 55 ° C. or lower (high temperature standby).

  Next, an outline of the flow of the quick charge control will be described based on the flowchart of FIG.

  In step S2, the charging control microcomputer 125 determines whether or not the battery pack 129 is attached. If the battery pack 129 is not attached, it waits for attachment. If the battery pack 129 is attached, charging is started in step S3.

  In step S4, the temperature of the battery pack 129 is detected. In step S5, a charging voltage value is determined. In step S6, a branch for changing the charging voltage is performed. When the charging voltage is not changed in step S6, the process proceeds to step S8.

  When the charging voltage is increased in step S6, the process proceeds to step S7. In step S7, both the switch 115 and the switch 117 are cut off and set to the normal charging voltage. In step S8, the end of charging is determined. If the charging voltage and the charging current are in the charging end condition in step S8, the charging is ended in step S9. If it is not charge termination conditions at step S8, it will return to step S2 and will continue charge. When the charging voltage is decreased in step S6, the process proceeds to step S10.

  In step S10, the switch 120 is shut off to suspend charging. In step S11, a maximum time timer for comparing the charging voltage and the battery pack voltage is started. In step S12, the battery pack voltage is measured.

  Step S13 is a lapsed branch of the maximum time timer for comparing the charging voltage and the battery pack voltage.

  If the timer has timed out in step S13, charging is terminated in step S9. If the timer has not timed out in step S13, the process proceeds to step S14.

  In step S14, the charging voltage is compared with the battery pack voltage. If the battery pack voltage is equal to or higher than the charging voltage in step S14, the process returns to step S12. If the battery pack voltage is less than the charging voltage in step S14, the process proceeds to step S15.

  Step S15 is a setting of the charging voltage. In step S16, the switch 120 is turned on to resume charging, and the process returns to step S2 to continue charging.

  Next, details of the temperature detection process of the battery pack 129 in step S4 of FIG. 4 will be described in detail based on the sub-flowchart of FIG. In this temperature detection process, the charge control microcomputer 125 first measures the voltage at the temperature terminal 127 (step SS1).

  Then, the charging control microcomputer 125 refers to the temperature / voltage table of the thermistor 133 registered in the memory for the temperature of the battery pack 129 corresponding to the voltage of the temperature terminal 127 (step SS2).

  Next, the charging control microcomputer 125 determines the temperature of the thermistor 133 corresponding to the voltage of the referenced temperature terminal 127 as the temperature of the battery pack 129 (step SS3), and returns to the flow of FIG.

  Next, details of the determination process of the charging voltage value in step S5 of FIG. 4 will be described in detail based on the sub-flowchart of FIG. In the charging voltage value determination process, the charging control microcomputer 125 first refers to the temperature of the battery pack 129 detected in step S4 (step SS5).

  Then, the charge control microcomputer 125 refers to the charge voltage value data for each temperature range registered in the memory in the charge control microcomputer 125 (step SS6).

  The registered data is a charging voltage value corresponding to the temperature range.

  Next, the charging control microcomputer 125 determines a charging voltage value corresponding to the temperature of the battery pack 129 (step SS7), and returns to the flow of FIG.

  Next, details of the charging voltage setting process in step S15 of FIG. 4 will be described in detail based on the sub-flowchart of FIG.

  In this charge voltage setting process, the charge control microcomputer 125 first determines whether the temperature of the battery pack 129 detected in step S4 is low temperature charge or high temperature charge (step SS9).

  When performing low temperature charging, the charging control microcomputer 125 conducts the switch 115 (step SS10), sets the low temperature charging voltage, and returns at step SS12.

  When performing high temperature charging, the charging control microcomputer 125 conducts the switch 117 (step SS11), sets the high temperature charging voltage, and returns at step SS12.

  By controlling as described above, charging can be resumed after the voltage of the battery pack 129 drops below the charging voltage.

  This makes it possible to perform charging without reducing the charge capacity of the battery pack, as compared with a method in which charging is terminated by measuring the voltage of the battery pack immediately after charging.

  In addition, by setting the maximum charging standby time with a timer, charging can be terminated in an appropriate charging state.

  The switches used in the present invention are generally semiconductor switches such as transistors and FETs, but may be electromagnetic relays or the like. A dedicated IC can be used instead of the charge control microcomputer. For detecting the temperature of the battery pack, a dedicated IC may be used in addition to the thermistor.

  Furthermore, the object of the present invention is also achieved by a computer-readable storage medium that records (stores) software program code (computer-executable program) that implements the functions of the above-described embodiments.

  That is, this storage medium is supplied to a system or apparatus, and a computer (or CPU, MPU, etc.) of the system or apparatus reads and executes the program code stored in the storage medium.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code and the storage medium storing the program code constitute the present invention.

  The following can be used as a storage medium for supplying the program code.

  For example, a floppy (registered trademark) disk, a hard disk, a magneto-optical disk, or the like can be used.

  Further, optical disks such as CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD + RW, magnetic tape, nonvolatile memory card, ROM, and the like can be used.

  Alternatively, the program code may be downloaded via a network.

  The present invention is not limited to the case where the functions of the above-described embodiments are realized by executing the program code read by the computer.

  In addition, for example, on the basis of an instruction of the program code, an OS (operating system) running on the computer performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing. Cases are also included.

  Furthermore, the case where the functions of the embodiment are realized by writing the program code read from the storage medium into a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer is also included. .

  In this case, after the writing, the CPU or the like provided in the function expansion board or function expansion unit performs part or all of the actual processing based on the instruction of the program code.

It is an external view of the charging device which concerns on embodiment of this invention. It is a block diagram which shows the structure of the electric circuit of the charging device shown in FIG. 1, and a battery pack. It is a figure explaining the change of the charging voltage by battery pack temperature. It is a flowchart explaining the charging operation of the charging device shown in FIG. 6 is a sub-flowchart for explaining battery pack temperature detection processing in step S4 of FIG. 5 is a sub-flowchart for explaining a charging voltage value determination process in step S5 of FIG. 5 is a sub-flowchart for explaining a charging voltage setting process in step S15 of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,129 Battery pack 5,101 Charging apparatus 105 Photocoupler 113 Volume 120 Quick charge switch 125 Charge control microcomputer 133 Temperature detection element (thermistor)
134 cells

Claims (4)

A charging device for charging a battery pack,
Charging voltage switching means for switching a charging voltage applied to the battery pack between a first charging voltage and a second charging voltage lower than the first charging voltage;
A switch for switching the charging voltage to a state where the charging voltage is not applied to the battery pack;
Voltage measuring means for measuring the voltage of the battery pack;
When the charging voltage is switched from the first charging voltage to the second charging voltage, the charging voltage switching means does not apply the first charging voltage to the battery pack by the switch, and the battery pack The charging device is characterized in that the second charging voltage is applied to the battery pack by the switch after the voltage drops below the second charging voltage. Temperature measuring means for measuring the temperature of the battery pack;
2. The charging according to claim 1, wherein the charging voltage switching unit switches between the first charging voltage and the second charging voltage based on a temperature of the battery pack measured by the temperature measuring unit. apparatus. Clocking means for timing an elapsed time since the switch does not apply the first charging voltage to the battery pack;
2. A control unit that stops charging when the voltage of the battery pack does not drop below the second charging voltage even if the time measured by the time measuring unit exceeds a predetermined time. 2. The charging device according to 2. A charge control method for charging a battery pack by switching a charge voltage between a first charge voltage and a second charge voltage lower than the first charge voltage,
A step of not applying the first charge voltage to the battery pack when the charge voltage is switched from the first charge voltage to the second charge voltage;
Measuring the voltage of the battery pack;
A charge control method comprising: a state in which the second charge voltage is applied to the battery pack after the voltage of the battery pack has dropped below the second charge voltage.

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