JP2008187790A - Charger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable setting a charging voltage mode for maintaining the long lifetime of a secondary battery such as a lithium ion secondary battery, in a charger for charging the secondary battery at a constant current and constant voltage. <P>SOLUTION: The charger 200 is provided with a charging current control circuit 60, a charging voltage control circuit 100 and a charging voltage setting circuit 100b provided in connection with the charging voltage control circuit 100 and used to set the charging voltage. The charger 200 is constituted so that the charging voltage setting circuit 100b is provided with a first voltage dividing resistor means R1 and a second voltage dividing resistor means R2, and a voltage dividing ratio between a resistance value R1 of the first voltage dividing resistor means R1 and a resistance value R2 of the second voltage dividing resistor means R2 is varied so that either a first setting voltage mode (usual mode) or a second setting voltage mode (long lifetime mode) can be selected for the charging voltage. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a charging device for constant current / constant voltage charging of a secondary battery such as a lithium ion secondary battery, and more particularly to a charging device capable of setting a charging voltage mode.

  As a power source for driving the cordless electric tool, a secondary battery having a relatively high capacity such as a nickel metal hydride battery or a nickel-cadmium battery is used. In addition, lithium ion batteries have been put into practical use as secondary batteries with high capacity and light weight. The nominal voltage of a lithium ion battery has a characteristic that it is relatively high, about three times as large as that of nickel-metal hydride batteries and nickel-cadmium batteries that are widely used in practice, and is small and lightweight. Furthermore, it has good discharge efficiency, can be discharged even in a relatively low temperature environment, and can obtain a stable voltage over a wide temperature range.

  In a charging device that charges a battery pack such as a nickel metal hydride battery or a nickel cadmium battery that is used as a power source for a cordless power tool or the like, a quick charging mode that charges in a short time with a large charging current when it is desired to complete the charging quickly. Patent Document 1 proposes a charging device that employs a long-time charging mode in which charging is performed over a long period of time with a small charging current.

Japanese Patent Laid-Open No. 2005-73434

  In the conventional charging device, when charging in the long-time charging mode giving priority to extending the life of the battery, charging is performed with a small charging current. In particular, nickel-metal hydride batteries and nickel-cadmium batteries employ a constant-current charge control method, and in order to extend the battery life, heat generation during charging, which is one of the factors affecting the battery life, is suppressed. In general, charging is performed for a long time by reducing the charging current.

  On the other hand, lithium-ion batteries are generally charged using a constant-current / constant-voltage charging control method, so that they generate relatively little heat during constant-current charging, so they do not affect the battery life. . In particular, it is the charging voltage value during constant voltage charging that greatly affects the battery life. Generally, the charging voltage of a lithium ion battery is set to 4.2 V per cell. However, when charging is performed at a value exceeding this value, the life of the lithium ion battery is greatly deteriorated. Conversely, when the battery is set to 4.2 V or less, for example, 4.1 V, the battery capacity slightly decreases. It has been found that the battery life is improved.

  Therefore, the object of the present invention is to pay attention to the fact that the life of the lithium battery depends on the magnitude of the charging voltage during constant voltage charging after constant current charging, and is effective in improving the battery life without taking charging time. An object of the present invention is to provide a charging device that can select a certain charging method.

  Among the inventions disclosed in accordance with the present invention in order to solve the above problems, the characteristics of typical ones will be described as follows.

  According to one aspect of the present invention, there is provided a charging device for charging a secondary battery, the constant current / constant voltage charging control for applying a constant voltage after energizing the secondary battery with a constant current. A charging current control circuit for energizing the constant current, a charging voltage control circuit for applying the constant voltage, and a charging voltage provided in association with the charging voltage control circuit And a setting voltage value in a plurality of modes including at least a first setting voltage value and a second setting voltage value lower than the first setting voltage value. A charging voltage selection means for selecting one of the charging voltage, and the charging voltage control circuit compares the input voltage corresponding to the charging voltage with a reference voltage to control the charging voltage. Output voltage comparison The charging voltage setting circuit includes first voltage dividing resistor means and second voltage dividing resistor means connected in series with each other for setting the input voltage or the reference voltage of the voltage comparator. And the divided voltage divided by the second voltage dividing resistor means is applied as the input voltage or the reference voltage of the voltage comparator, and the charging voltage selecting means is configured to apply the first voltage to the first voltage dividing resistor means. By changing the input voltage or the reference voltage based on the voltage dividing ratio between the resistance value of the voltage dividing resistor means and the resistance value of the second voltage dividing resistor means, the charging voltage is set to the set voltage of the plurality of modes. Select one of the values.

  According to another feature of the present invention, the first voltage dividing resistor means of the charging voltage setting circuit includes a first resistor for setting the first set voltage value, and the first resistor. And a second resistor connected in parallel via the first switching element for setting the second set voltage value, wherein the charging voltage selection means turns on or off the first switching element. It comprises switch means for making it happen.

  According to still another aspect of the present invention, when the charging voltage selecting means sets the second set voltage value by connecting the second resistor in parallel to the first resistor, the charging voltage is The display means for displaying that the voltage is the second set voltage value is turned on.

  According to still another aspect of the present invention, the charging current control circuit has a plurality of mode setting current values including at least a first setting current value and a second setting current value lower than the first setting current value. A charging current selection means capable of selecting one of them is provided.

  According to the above feature of the present invention, it is possible to provide a charging device having a charging voltage setting means capable of selecting a charging method for a relatively short time which is effective in improving the life of the secondary battery.

  The above and other objects, and the above and other features and advantages of the present invention will become more apparent from the following description of the present specification and the accompanying drawings.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.

  FIG. 1 shows a circuit diagram of a charging device 200 according to an embodiment of the present invention. In FIG. 1, a battery pack (secondary battery) 2 to be charged by a charging device 200 includes a single or a plurality of rechargeable, for example, lithium ion battery cells 2a and a battery cell 2a connected in series. A cell number discrimination resistor 7 for discriminating the number, and a temperature sensing element functioning as a temperature detection sensor such as a thermistor disposed in contact with or close to the battery cell 2a in order to detect the battery temperature in the battery pack 2 8. For example, the battery pack 2 of the present embodiment includes a lithium ion battery (nominal voltage 3.6 V) having one battery cell 2 a, and a thermistor is used as the temperature sensitive element 8. The cell number discrimination resistor 7 divides the DC voltage (stabilized DC voltage) Vcc with the detection resistor 9 constituting the cell number discrimination circuit, and discriminates the cell number based on the detected voltage.

  The temperature sensing element 8 of the battery pack 2 is connected to a battery temperature detection circuit 80 composed of series resistors 81 and 82 to which a DC voltage Vcc is supplied, converts the temperature change of the resistance value into a voltage, and the microcomputer 50 described later / D converter 52 is input. A positive electrode terminal of the battery pack 2 is connected to a battery voltage detection circuit 90 including a voltage dividing circuit of a resistor 91 and a resistor 92.

(Charging power supply circuit 160)
A charging power supply circuit 160 for supplying charging power to the battery pack 2 is a switching power supply circuit including a primary side rectifying and smoothing circuit 10, a switching circuit 20 including a high frequency transformer 21, and a secondary side rectifying and smoothing circuit 30. Composed.

  The primary side rectifying / smoothing circuit 10 includes a full-wave rectifying circuit 11 and a smoothing capacitor 12, and full-wave rectifies the AC power source 1 such as a commercial AC power source.

  The switching circuit 20 includes a high frequency transformer 21, a MOSFET (switching element) 22 connected in series to the primary winding 21 a of the transformer 21, and a PWMIC for modulating the pulse width of the drive pulse signal applied to the gate electrode of the MOSFET 22. (Switching control IC) 23.

  Driving power for the PWMIC 23 is supplied from a rectifying and smoothing circuit (DC power supply circuit) 6. The rectifying / smoothing circuit 6 includes a transformer 6a, a rectifying diode 6b, and a smoothing capacitor 6c. A charge voltage control signal and a charge current control signal are input to the PWMIC 23 via the charge feedback signal transmission means 5 comprising a photocoupler. In addition, a charge control signal for controlling the start and stop of charging is input to the PWMIC 23 via the charge control transmission means 4 comprising a photocoupler.

  The PWMIC 23 controls the start and stop of the charging operation of the MOSFET 22 by the control signal supplied from the microcomputer 50 by the photocoupler (charge control transmission means) 4 and the control signal supplied by the photocoupler (charge feedback signal transmission means) 5. By changing the drive pulse width supplied to the gate electrode of the MOSFET 22 by controlling the ON time of the MOSFET 22, the output voltage of the secondary side rectifying and smoothing circuit 30 and the charging current of the battery pack 2 are adjusted.

  The secondary side rectifying / smoothing circuit 30 includes a rectifying diode 31, a smoothing capacitor 32, and a discharging resistor 33 connected to the secondary winding 21 c of the transformer 21.

  The constant voltage power supply circuit 40 is provided to supply a stabilized DC voltage Vcc to various control circuits (including a detection circuit) such as the microcomputer 50 and the operational amplifiers 61 and 65. The constant voltage power supply circuit 40 is connected to the transformers 41a to 41c, the switching element 42 and the control element 43 constituting the switching power supply, the rectifying diode 44, the three-terminal regulator 46, and the input side of the three-terminal regulator 46. And a smoothing capacitor 47 connected to the output side of the three-terminal regulator 46, and outputs a constant voltage Vcc. A reset IC 48 for outputting a reset signal when the commercial power source 1 is turned on to the charging device 200 is connected to the constant voltage output side of the constant voltage power supply circuit 40.

(Control circuit device 50)
The control circuit device (microcomputer) 50 determines the battery temperature based on the output signal of the battery temperature detection circuit 80, determines the battery voltage based on the output signal of the battery voltage detection circuit 90, outputs a control signal to the charging power supply circuit 160, It is provided to execute output of control signals to a charging current control circuit 60 and a charging voltage control circuit 100 described later. Although not shown, the microcomputer 50 is a read only memory (ROM) that stores a control program of the CPU 51, data related to the battery type of the battery pack 2, and the like, in addition to a CPU (central processing unit) 51 that executes a control program. ), A random access memory (RAM) used as a work area for the CPU 51, a temporary data storage area, and the like, and a timer.

  Further, the microcomputer 50 includes an A / D converter 52 for converting an analog input signal detected by the cell number detection resistor 9, the battery voltage detection circuit 90, the battery temperature detection circuit 80, and the like into a digital output signal, which will be described later. An output port 51b for outputting a control signal to the charging voltage control circuit 100, an output port 51a for outputting a control signal for the display circuit, and an input port 53 for inputting an output signal of the charging mode selection circuit 150. And a reset input port 54 for inputting a reset signal of the reset IC 48.

(Charging current control circuit 60 and charging current setting circuit 70)
The charging current control circuit 60 includes operational amplifiers (operational amplifiers) 61 and 65, input resistors 62 and 64 of the operational amplifiers 61 and 65, feedback resistors 63 and 66 of the operational amplifiers 61 and 65, a diode 68, and a current limiting resistor 67. And an operational amplifier circuit composed of an output circuit. The input stage of the charging current control circuit 60 is connected to the charging current detection resistor 3 for detecting the charging current of the battery pack 2. Further, as described above, the output stage controls the PWMIC 23 via the charge feedback signal transmission means 5 comprising a photocoupler. A charging current setting circuit 70 is connected to one input terminal (+) of the operational amplifier (voltage comparator) 65. On the other hand, the output voltage of the operational amplifier 61 is input to the A / D converter 52 to monitor the charging current value, and the charging current value is measured by the microcomputer 50. The microcomputer 50 also measures a decrease in the current value at the time of full charge, based on the output of the operational amplifier 61.

  The charging current setting circuit 70 is provided to alternatively set the charging current between the “first charging current mode”, the “second charging current mode”, and the “third charging current mode”. . The setting circuit 70 includes a series circuit (voltage dividing circuit) of a resistor 71 and a resistor 72 connected to the stabilized DC voltage Vcc, and a resistor 73 and a resistor 74 connected in parallel to the resistor 72. A desired charging current is set by supplying a reference voltage corresponding to a different charging current to the input terminal (+) of the voltage comparator 65. According to the present embodiment, three charging current modes are set by connecting the resistor 73 or the resistor 74 in parallel to the resistor 72 based on the operation of the microcomputer 50.

  For example, when the resistance connected in series with the resistor 71 is controlled by the microcomputer 50 as the resistance 72 alone, the first charging current mode is set, and the resistance connected in series with the resistance 71 is a parallel connection of the resistance 72 and the resistance 73. When the connection resistance is controlled, the “second charging current mode” is set. Furthermore, when the resistance connected in series to the resistance 71 is controlled as a parallel connection resistance of the resistance 72 and the resistance 74, the “third charging current mode” is set. In this case, it is assumed that the charging current value decreases in the order of “first charging current mode”, “second charging current mode”, and “third charging current mode”.

  The charging current control circuit 60 inverts and amplifies the voltage drop based on the charging current flowing through the charging current detection resistor 3 by the resistors 62 and 63 and the operational amplifier 61, and the output voltage and the charging current value set by the charging current setting circuit 70. The operational amplifier 65 functioning as a voltage comparator amplifies the difference from the set voltage value (set charge signal) corresponding to, and feeds back to the PWMIC 23 via the charge feedback signal transmission means 5 to control the switching operation of the MOSFET 22. That is, the MOSFET 22 gives an output pulse with a narrowed pulse width to the high-frequency transformer 21 when the charging current flowing through the current detection means 3 is larger than the predetermined charging current, and conversely when the charging current is smaller than the predetermined charging current. A pulse having a wider width is applied to the high-frequency transformer 21. As a result, the secondary side rectifying and smoothing circuit 30 smoothes the DC voltage corresponding to the predetermined charging current, and holds the charging current of the battery pack 2 at the predetermined current set by the charging current setting circuit 70. In other words, the current detection unit 3, the charging current control circuit 60, the charging feedback signal transmission unit 5, the switching circuit 20 and the secondary side rectifying / smoothing circuit 30 have the set charging current value set by the charging current setting circuit 70. The charging current flowing through the battery pack 2 is controlled.

(Charge voltage control circuit 100)
The charging voltage control circuit 100 is a circuit for controlling the charging voltage of the battery pack 2, and is connected to a known shunt regulator 109 having an anode terminal a, a cathode terminal k, and a reference terminal r, and a reference terminal r of the shunt regulator 106. Charge voltage setting circuit 100b. As shown in FIG. 2, the equivalent circuit of the shunt regulator 109 includes an operational amplifier (voltage comparator) Op, a current path transistor Tr, and a reference voltage source Vref including a Zener diode and the like.

  As shown in FIG. 2, a first voltage dividing resistor means configured by resistors 101 to 103 and 105 is provided between the reference terminal (comparison input terminal) r of the shunt regulator 109 and the positive terminal of the battery pack 2. R1 is connected. In addition, a second voltage dividing resistor means R2 constituted by resistors 110, 111, 112, and 113 is connected between the negative terminal (ground terminal) of the battery pack 2. A current limiting resistor 123 and a diode 124 are connected to the cathode terminal k of the shunt regulator 109, and a phase compensation resistor 107 and a capacitor 108 are connected between the reference terminal r and the cathode terminal k of the shunt regulator 109. The

  The shunt regulator 109 has a combined resistance value R1 of the first voltage dividing resistor means R1 connected to the reference terminal (voltage comparison input terminal) r, a combined resistance value R2 of the second voltage dividing resistor means R2, and a shunt. If the internal reference voltage source (zener diode) of the regulator is Vref (for example, 2.5 V), the output charging voltage Vo adjusted by the function of the shunt regulator 109 is Vo≈Vref * (1 + R1 / R2). Therefore, the charging voltage Vo can be adjusted by making the voltage dividing ratio R1 / R2 variable.

(Charging voltage mode setting circuit R1)
According to the present invention, the “charging voltage mode” is switched by changing the resistance value R1 of the first voltage dividing resistor means R1. That is, by changing the resistance value R1, the normal first charging voltage mode (for example, referred to as “normal charging mode”) for relatively quick charging or lower than the first charging voltage mode. It is configured such that at least two charging voltage modes of a second charging voltage mode (for example, referred to as “eco charging mode”) for the purpose of charging for maintaining a long life by the charging voltage can be set. Further, a third charging voltage mode (for example, referred to as “super eco-charging mode”) for the purpose of charging for maintaining a longer life can be set as required. That is, the third charging voltage mode is set to a lower charging voltage than the second charging voltage mode, and the second charging voltage mode is set to a lower charging voltage than the first charging voltage mode.

  In order to switch between these “charge voltage modes”, the resistor 102 constituting the first voltage dividing resistor means R1 is connected in parallel to the resistor 101 via the switching element (P-channel MOSFET) 104, and the resistor 105 is The resistor 101 is connected in parallel via a switching element (P channel MOSFET) 106. Each switching element 104, 106 is controlled from an off state to an on state alternatively by a control signal of the output port 51b of the microcomputer 50. Thereby, when the first charging voltage mode is selected, the switching elements 104 and 106 are turned off, and only the resistor 101 is selected. When the second charging voltage mode is selected, only the switching element 104 is turned on and the resistor 102 is connected in parallel to the resistor 101. Further, when the third charging voltage mode is selected, the switching element 106 is alternatively turned on and the resistor 105 is connected in parallel to the resistor 101. The combined resistance value R1 decreases in the order of the first charging voltage mode, the second charging voltage mode, and the third charging voltage mode, and each output charging voltage Vo decreases in order.

(Charge voltage setting circuit R2 depending on the number of cells)
On the other hand, according to the present embodiment, the adjustment of the charging voltage corresponding to the difference in the number of cells of the battery pack 2 to be charged is performed by varying the combined resistance value (R2) of the second voltage dividing resistor means R2. That is, when it is desired to increase the charging voltage when the number of cells is large, the combined resistance value R2 is set smaller. For this purpose, the resistor 111 constituting the second voltage dividing resistor means R2 is connected in parallel to the resistor 110 via the switching element (N-channel MOSFET) 114. Similarly, the resistor 112 is connected in parallel to the resistor 110 via a switching element (N channel MOSFET) 115, and the resistor 113 is connected in parallel to the resistor 110 via a switching element (N channel MOSFET) 116. The gate terminals of the switching elements 114, 115, and 116 are connected to the output port 51b of the microcomputer 50 via the resistors 118, 120, and 122, respectively. Bias resistors 117, 119, and 121 are connected to the gate terminals of the switching elements 114, 115, and 116, respectively.

  Each of the switching elements 114, 115, 116 is controlled to be turned on alternatively from the off state by a control signal from the microcomputer 50. The microcomputer 50 automatically takes in the output voltage of the voltage dividing circuit by the resistor 7 indicating the number of cells and the cell number detecting resistor 9 from the A / D converter input port 52, and the switching elements 114, 115 corresponding to the number of cells. 116 are alternatively controlled to be in an on state.

  For example, the voltage division ratio R1 / R2 determined by the series combined resistance value R1 of the resistor 101 and the potentiometer 103 and the resistance value R2 of the resistor 110 is a set value of the “2-cell” lithium ion battery. The set value R2 for charging the “3-cell” lithium ion battery is a combined resistance value in which the MOSFET (switching element) 114 is turned on and the resistor 111 is connected in parallel to the resistor 110. Similarly, the set value R2 for charging the “4-cell” lithium ion battery is a combined resistance value in which the MOSFET 115 is turned on and the resistor 112 is connected in parallel to the resistor 110. Further, the set value R2 for charging the “5-cell” lithium ion battery is a combined resistance value in which the MOSFET 116 is turned on and the resistor 113 is connected in parallel to the resistor 110. Thus, according to the present embodiment, the adjustment of the charging voltage corresponding to the difference in the number of cells is performed by varying the combined resistance value R2 of the second voltage dividing resistor means R2.

(Charge mode selection circuit 150)
The charging mode selection circuit 150 is provided to selectively select the “first charging voltage mode” to the “third charging voltage mode”. Further, it is provided to selectively select the “first charging current mode” to the “third charging current mode”.

  The charging mode selection circuit 150 includes a first mode input switch circuit 150a including a push button switch 152 and a resistor 151, and a second mode input switch circuit 150b including a push button switch 154 and a resistor 153. The push button switches 152 and 154 are normal off switches that are in an off state in a normal state, and are constituted by a momentary on switch that is turned on only when the switch is pressed.

  A first mode input switch circuit 150a including a push button switch 152 and a resistor 151 is provided to switch the “charging voltage mode”. When the button switch 152 is pressed, the input port 53 of the microcomputer 50 is connected. A low signal is inputted and a low signal for turning on the MOSFET 104 or 106 is outputted to the output port 51b of the microcomputer 50 according to a predetermined number of times pressed, or a high signal for turning off both the MOSFETs 104 and 106 is outputted. To do. If the MOSFET 104 or the MOSFET 106 is turned on, the resistor 102 or the resistor 105 is connected in parallel to the resistor 101, the combined resistance value R1 is set smaller than that of the resistor 101 alone, and the charging voltage can be set low. Also, the resistor 101 can be used alone by turning off both the MOSFETs 104 and 106. Thus, for example, the number of pressing times is “first charging voltage mode”, the number of pressing times is “second charging voltage mode”, and the number of pressing times is “third charging voltage mode”. The switching element (MOSFET) 104 or 106 described above can be controlled to an on state or an off state according to the number of times of determination.

  On the other hand, the second mode input switch circuit 150b composed of the push button switch 154 and the resistor 153 has charging currents of “first charging current mode”, “second charging current mode”, and “third charging current”. It is provided to set the “mode” alternatively. Similar to the setting of the charging voltage mode, when the microcomputer 50 detects the number of times the push button switch 154 is pressed, the resistor 73 or 74 is connected in parallel to the resistor 72 from the output port 51b of the microcomputer 50, or both resistors By disconnecting 73 and 74, three charging current modes are set. For example, it is determined that the number of pressing times is “first charging current mode”, the number of pressing times is “second charging current mode”, and the number of pressing times is “third charging current mode”. Either one of the resistor 73 or the resistor 74 is selected according to the different number of determinations, and is connected in parallel with the resistor 72.

(Mode switching display circuit 130 and mode setting display circuit 140)
The mode switching display circuit 130 includes display means 131 composed of a red LED (R) and a green LED (G), and current limiting resistors 132 and 133 for each LED. Similarly, the mode setting display circuit 140 includes a red LED (R) and a green LED (G). The display unit 141 includes an LED (R) and a green LED (G), and current limiting resistors 142 and 133 of the LEDs. Both display circuits 130 and 140 are integrated to display a charging mode.

  That is, the mode switching display circuit 130 displays the mode switching type. For example, the mode switching display circuit 130 displays “charging voltage mode switching” by lighting the red LED (R), displays “charging current mode switching” by lighting the green LED (G), and further displays the red LED (R). R) and the green LED (G) are turned on simultaneously to indicate that “charging voltage / charging current mode switching” is indicated.

  On the other hand, the mode setting display circuit 140 displays the magnitude relationship between the modes in cooperation with the mode switching display circuit 130. For example, when the mode switching display circuit 130 displays “charging voltage mode switching” by lighting the red LED (R), “first charging voltage mode” is displayed by lighting the red LED (R), When the green LED (G) is turned on, the “second charging voltage mode” is displayed, and further, when the red LED (R) and the green LED (G) are turned on simultaneously, the color is “third charging voltage mode”. Is displayed.

  Similarly, when the mode switching display circuit 130 displays “charging current mode switching” by lighting of the green LED (G), the mode setting display circuit 140 displays “first” by lighting of the red LED (R). "Charging current mode" is displayed, "Second charging current mode" is displayed when the green LED (G) is lit, and "3rd charging current mode" is displayed when the red LED (R) and the green LED (G) are simultaneously lit. "Charging current mode" is displayed.

  Further, when the mode switching display circuit 130 displays “charging voltage / current mode switching” by turning on the red LED (R) and the green LED (G), the mode setting display circuit 140 displays the red LED (R). The first charging voltage / current mode (for example, “rapid charging mode”) is displayed by orange when the LED and the green LED (G) are simultaneously turned on, and the second charging voltage / current is displayed by turning on the red LED (R). “Current mode” (for example, “eco-charging mode”) is displayed, and further, the green LED (G) is turned on to indicate that it is “third charging voltage / current mode” (for example, “super-eco charging mode”). indicate.

  In the present embodiment, nine types of modes can be set by the charging mode selection circuit 150, but only the charging voltage may be set.

(Charging characteristics of battery pack by charging device 200)
1. Charging voltage mode switching method (constant charging current)
FIG. 3 is a characteristic diagram showing changes over time in battery voltage and charging current when the battery pack 2 of the lithium ion battery is charged at a constant current / constant voltage by the charging device 200 according to the present invention. In particular, for three battery packs (lithium ion batteries) having a constant charging current and the same discharge capacity, three types of a first charging voltage mode V1, a second charging voltage mode V2, and a third charging voltage mode V3 are used. The characteristic figure when each is applied is shown.

  The characteristic diagram shown in FIG. 3 shows the first charge voltage mode V1 for the first battery pack by varying the combined resistance value R1 (see FIG. 2) of the voltage comparator Op of the charge voltage setting circuit 100b. Was applied to set the charging voltage per cell to 4.20 V / cell. For the second battery pack, the second charging voltage mode V2 is applied to set the charging voltage per cell to 4.15 V / cell, and for the third battery pack, When the charging voltage mode V3 is applied, the charging voltage per cell is set to 4.10 V / cell, respectively. By selecting the charging voltage modes V1 to V3, the characteristics of the charging current change from I1 to I3, and the charging time can be shortened from T1 to T3 (T3 <T1).

  According to this charging voltage mode, by setting the charging voltage in the charging voltage mode low, a charging mode (characteristic V3 and characteristic I3) for maintaining a relatively long life can be achieved, and the charging time can be shortened. can do. In this case, the setting of the charging voltage mode can be easily realized by changing the voltage dividing ratio (R1 / R2) of the voltage dividing resistor circuit (100b) of the voltage comparator Op (see FIG. 2).

2. FIG. 4 and FIG. 5 show changes over time in battery voltage and charging current when the battery pack 2 of the lithium ion battery is charged with constant current / constant voltage by the charging device 200 according to the present invention. FIG. In particular, it is a characteristic diagram when both the charging voltage mode and the charging current mode are set for charging. As described above, the charging voltage mode is set by changing the resistance value (R1) of the voltage dividing resistor means R1 of the charging voltage setting circuit 100b. The charging current mode is set by switching the connection of the voltage dividing resistors 72, 73 and 74 of the charging current setting circuit 70 connected to the voltage comparator 65 as described above.

  4 and 5, the “rapid charging mode” (first charging mode) indicates a case where the charging current I4 is set to 9 A and the charging voltage V4 is set to 4.20 V / cell. In this case, as shown in FIG. 5, the charging time is 20 minutes. Similarly, in the “eco-charging mode” (second charging mode), when the charging current I5 is set to 6 A and the charging voltage V5 is set to 4.15 V / cell, the “super-eco mode” (third charging mode) ) Shows a case where the charging current I6 is set to 4 A and the charging voltage V6 is set to 4.10 V / cell. The charging time was 30 minutes in the “eco charging mode” and 45 minutes in the “super eco mode”.

  As is apparent from FIGS. 4 and 5, by making the set charging voltage and the set charging current variable, rapid charging (I4 / V4 characteristics) that shortens the charging time is enabled. In addition, super-eco charging (I6 / V6 characteristics) capable of maintaining a long life as required is also possible.

3. Charging current mode switching method (constant charging voltage)
FIG. 6 shows a charge characteristic diagram when the set charge current is decreased to I7, I8, and I9 with the charge set voltages (V7, V8, V9) being constant. In FIG. 6, a charging voltage characteristic V7 indicates a characteristic when the charging current is I7, a charging voltage characteristic V8 indicates a characteristic when the charging current is I8, and a charging voltage characteristic V9 indicates a characteristic when the charging current is I9. In this charging mode, the charging voltage is set constant, so that rapid charging is possible. However, in terms of eco-mode charging for maintaining a long life, the charging mode shown in FIG. 4 (the charging voltage mode is variable). ) Is more effective.

(Constant current / constant voltage charging operation flowchart)
FIG. 7 shows an operation flowchart of constant current / constant voltage charging of the charging apparatus 200 according to the present invention. In particular, an operation flowchart according to the charging voltage / charging current mode switching method shown in FIGS. 4 and 5 is shown. Hereinafter, the charging operation according to the charging device 200 of the present invention will be described with reference to the flowchart shown in FIG.

  First, it is determined whether or not the selection buttons 152 and 154 of the charging mode selection circuit 150 have been pressed before mounting the battery pack 2 to be charged on the charging device 200 (step 201). Whether or not the selection buttons 152 and 154 have been pressed is determined by whether or not a low signal has been input to the input port 53 of the microcomputer 50.

  If it is determined in step 201 that the selection buttons 152 and 154 have been pressed (in the case of YES), it is determined whether or not the display on the display means (LED) 141 is red (R) (step 202a). If the display means 141 is a red LED (R), the green LED (G) of the display means 141 is turned on to turn the display means 141 orange (step 203). With this setting, the FET 104 of the charging voltage setting circuit 100b is turned off (step 204), and the FET 106 is also turned off (step 205). Thus, the charging voltage is set to V4 (4.20 V / cell) shown in FIGS. Further, the charging current at that time is set to I4 (9A) (step 206).

  When it is determined in step 202a that the display unit 141 is not a red LED (R) (in the case of NO), the process proceeds to step 202b, and the red LED (R) and the green LED (G) of the display unit 141 are turned on and turn orange. It is determined whether or not (step 202b). If the red LED (R) and the green LED (G) are lit, only the red LED (R) is lit (step 207). With this setting, the FET 104 of the charging voltage setting circuit 100b is turned on (step 208) and the FET 106 is turned off (step 209). As a result, the charging voltage is set to V5 (4.15 V / cell) shown in FIGS. Further, the charging current at that time is set to I5 (6A) (step 210).

  In step 202b, when the red LED (R) and the green LED (G) of the display means 141 are turned on simultaneously and are not orange (in the case of NO), the green LED (G) is turned on (step 211). With this setting, the FET 104 is turned off (step 212) and the FET 106 is turned on (step 213). As a result, the charging voltage is set to V6 (4.10 V / cell) shown in FIGS. Further, the charging current at that time is set to I6 (4A) (step 214).

  In the present embodiment, the mode selection by the charging mode selection circuit 150 can be performed only before the battery pack 2 is mounted. If it is determined in step 201 that the push button 152 or 154 is not pressed, it is determined whether or not a battery is mounted (step 215). This determination is made based on the outputs of the battery temperature detection circuit 80, the cell number determination circuit 9, and the battery voltage detection circuit 90.

  If it is determined in step 215 that the battery pack 2 is mounted, the number of cells is determined by the cell number determination circuit 9 (step 216), and a charging voltage corresponding to the number of cells is set (step 217).

  In the present embodiment, it is assumed that the battery pack 2 can charge a battery pack that is a lithium ion battery including two cells, three cells, four cells, and five cells. That is, when the FET (switching element) 114 is turned on, it can be set to a charging voltage corresponding to a three-cell battery pack. When the switching element 115 is turned on, a charging voltage corresponding to a 4-cell battery pack can be set, and when the switching element 116 is turned on, a charging voltage corresponding to a 5-cell battery pack can be set. When none of the switching elements is turned on, a charging voltage corresponding to a two-cell battery pack can be set.

  Next, a low signal is output from the output port 51a of the microcomputer 50 to the photocoupler 4 in order to start charging, and the PWMIC 23 is put into an operating state. As a result, charging is started (step 218).

  After the start of charging, the potential detected by the current detection circuit 3 is inverted and amplified by the operational amplifier 61 and taken into the A / D port 52 of the microcomputer 50 to control the charging current (constant current). As shown in FIG. 4, the battery voltage of the battery pack 2 rises with charging and shifts to a constant voltage charging section, and then the charging current decreases. When the current decrease reaches a predetermined value or less, it is determined that the battery is fully charged (step 219). After determining that the battery is fully charged, a high signal is output from the port connected to the photocoupler 4 in the output port 51a, and the PWMIC 23 is stopped (step 220). Thereafter, when the battery pack 2 is removed from the charging device 200 (step 221), the process returns to step 201.

  In this embodiment, the case where both the charging voltage and the charging current are switched as shown in FIGS. 4 and 5 has been described. However, the charging current is not switched in steps 206, 210, and 214, and the switching is performed as shown in FIG. Thus, the charging current may be made constant and only the charging voltage may be switched.

  As is apparent from the above description, according to the present invention, the charging voltage mode can be set to a predetermined mode with a relatively simple circuit, and therefore a charging device that can easily select a charging method effective in improving the battery life. Can be provided.

  In the above embodiment, the series resistance circuit (voltage dividing circuit) constituted by the first voltage dividing resistor means R1 and the second voltage dividing resistor means R2 of the charging voltage setting circuit 100b is used for voltage comparison of the shunt regulator 109. Although the output voltage Vo of the charging device 200 applied as the input voltage of the comparator Op is divided, this series resistance circuit (series circuit of R1 and R2) generates the reference voltage Vref of the voltage comparator Op. Alternatively, a voltage dividing circuit for dividing the DC voltage (stabilized DC voltage) Vcc may be used. That is, by applying the DC voltage Vcc to the series resistance circuit (R1, R2), using the voltage generated in the second voltage dividing resistor means R2 by the resistance ratio as the reference voltage Vref, and varying the reference voltage Vref. Alternatively, different charging voltages may be selected.

  Further, the charging voltage control circuit 100 may use a voltage comparator Op configured by a normal operational amplifier as shown in FIG. 8 without using the voltage comparator Op of the shunt regulator 109 as described above. In the charging voltage control circuit 100 shown in FIG. 8, the output voltage Vo of the charging device 200 divided by the voltage dividing ratio of the resistor 86 and the resistor 87 is input to one input terminal (−) of the voltage comparator Op. The DC voltage Vcc is applied to the other input terminal (+) of the voltage comparator Op according to the voltage division ratio of the first voltage dividing resistor means R1 including the resistor 89 and the second voltage dividing resistor means R2 including the resistor 88. A configuration in which the divided voltage is input as the reference voltage Vref is shown.

  In this example, the DC voltage Vcc is configured such that the reference voltage Vref can be varied by setting the resistance ratio of the first voltage dividing resistor means R1 and the second voltage dividing resistor means R2, and charging voltages having different magnitudes can be selected. How to vary the resistance values (R1, R2) of the first voltage dividing resistor means R1 and the second voltage dividing resistor means R2 is the same as the charging voltage setting circuit 100b of the above embodiment shown in FIG. The resistor 89 or the resistor 88 constituting the voltage dividing circuit (series circuit of the resistor 89 and the resistor 88) is varied depending on whether another resistor (not shown) is connected in parallel by the switching element. In this case, when only the charge voltage mode is desired to be varied, the resistance value of one of the first voltage dividing resistor means R1 and the second voltage dividing resistor means R2 may be varied. Further, when it is desired to vary the charging voltage corresponding to the number of cells of the battery pack 2, the resistance values of both the voltage dividing resistor means R1 and R2 may be varied. With the configuration shown in FIG. 8, the same effect as described above can be obtained.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. is there.

The circuit diagram which shows one Embodiment of the charging device which concerns on this invention. The equivalent circuit schematic of the shunt regulator used for the charging device shown in FIG. The characteristic view which shows the time change of the battery voltage and charging current at the time of carrying out constant current and constant voltage charge with the charging device which concerns on this invention (charging current constant). The characteristic view which shows the time change of the battery voltage and charging current at the time of carrying out constant current and constant voltage charge with the charging device which concerns on this invention (charge current variable). The characteristic view which shows the setting battery voltage and setting charging current at the time of carrying out constant current and constant voltage charge with the charging device which concerns on this invention. The characteristic view (charge voltage constant) which shows the time change of the battery voltage and charging current at the time of carrying out constant current and constant voltage charge with the charging device which concerns on this invention. The operation | movement flowchart which performs constant current and constant voltage charge by the charging device shown in FIG. The circuit diagram which shows the other Example of the charging voltage control circuit which comprises the charging device shown in FIG.

Explanation of symbols

1: Input commercial power supply 2: Battery pack 2a: Battery cell 3: Current detection resistor 4: Charge control transmission means (photocoupler) 5: Charge feedback signal transmission means (photocoupler)
6: Rectification smoothing circuit 6a: Transformer 6b: Rectifying diode 6c: Smoothing capacitor 7: Cell number discrimination resistor 8: Temperature sensing element 9: Detection resistor 10: Primary side rectification smoothing circuit 11: Full wave rectification circuit 12: Smoothing capacitor 20: Switching circuit 21: High frequency transformer 21a: Primary winding of transformer 21c: Secondary winding of transformer 22: MOSFET 23: PWMIC (switching control IC)
30: Secondary side rectifying and smoothing circuit 31: Rectifying diode 32: Smoothing capacitor 33: Discharge resistor 40: Constant voltage power supply circuit 41a, 41b, 41c: Transformer 42: Switching element 43: Control element 44: Rectifying diode 45: smoothing capacitor 46: three-terminal regulator 47: smoothing capacitor 48: reset IC 50: microcomputer 51: CPU 51a: input port 51b: output port 52: A / D converter port 53: input port 54: reset input port 60 : Charging current control circuit 61, 65: operational amplifiers 62, 63, 64, 66, 67: resistor 68: diode 70: charging current setting circuit 71-73: resistor 80: battery temperature detection circuit 81, 82: detection resistor 83- 89: Resistance 90: Battery voltage detection circuit 91, 92: Resistance for detection 10 : Charge voltage control circuit 100b: charging voltage setting circuit 101,102,103,105 (R1): first voltage dividing resistance unit 104: switching elements (P-channel MOSFET)
107: resistor 108: capacitor 109: shunt regulator 110, 111, 112, 113 (R2): second voltage dividing resistor means 114, 115, 116: switching element (N-channel MOSFET)
117 to 123: Resistance 124: Diode 130: Mode switching display circuit 131: Display means (LED) 131R: Red LED 131G: Green LED
132, 133: Resistance 140: Mode setting display circuit 141: Display means (LED) 141R: Red LED 141G: Green LED
142, 143: Resistor 150: Charging mode selection circuit 151, 153: Resistor 152, 154: Push button switch 160: Charging power supply circuit 200: Charging device

Claims (4)

A charging device for charging a secondary battery, in which a constant current is applied to the secondary battery, and then a constant current / constant voltage charging control system charging device that applies a constant voltage,
A charging current control circuit for energizing the constant current; a charging voltage control circuit for applying the constant voltage; and a charging voltage setting for setting a charging voltage provided in association with the charging voltage control circuit A setting voltage of the circuit and the charging voltage setting circuit to one of a setting voltage value of a plurality of modes including at least a first setting voltage value and a second setting voltage value lower than the first setting voltage value Charging voltage selection means for selecting,
The charging voltage control circuit includes a voltage comparator that outputs a control signal for controlling a charging voltage by comparing an input voltage corresponding to the charging voltage with a reference voltage;
The charging voltage setting circuit includes first voltage dividing resistor means and second voltage dividing resistor means connected in series to set the input voltage or the reference voltage of the voltage comparator, and A divided voltage divided by the second voltage dividing resistor means is applied as the input voltage or the reference voltage of the voltage comparator;
The charging voltage selecting means varies the input voltage or the reference voltage based on a voltage dividing ratio between a resistance value of the first voltage dividing resistor means and a resistance value of the second voltage dividing resistor means, The charging device, wherein the charging voltage is selected as one of the set voltage values in the plurality of modes.   The first voltage dividing resistor means of the charging voltage setting circuit includes a first resistor for setting the first set voltage value and a parallel connection to the first resistor via a first switching element. And a second resistor for setting the second set voltage value, and the charging voltage selecting means comprises switch means for turning on or off the first switching element. The charging device according to claim 1.   The charging voltage selection unit displays that the charging voltage is the second setting voltage value when the second resistance is connected in parallel to the first resistance and the second setting voltage value is set. The charging device according to claim 1, wherein display means for lighting is turned on.   The charging current control circuit is capable of selecting one of a plurality of mode setting current values including at least a first setting current value and a second setting current value lower than the first setting current value. The charging apparatus according to claim 1, further comprising a current selection unit.

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