JP5418871B2 - Charger - Google Patents

Description

  The present invention relates to a charging device for charging a secondary battery such as a lithium ion battery by a constant current / constant voltage charging control system, and particularly, it is sufficient for the type of internal resistance of the secondary battery to be charged. The present invention relates to a charging device capable of securing a charging capacity.

  In general, a rechargeable secondary battery is used as a power source for portable devices such as electric tools, and is removed from the device whenever it runs out of capacity and charged with a charging device, and then attached to the portable device again. Repeatedly, it can be used many times. As this type of secondary battery, a lithium ion battery having a high output density is being widely used.

  For charging a lithium ion battery, a constant current / constant voltage charging control system in which a constant voltage is applied after a constant current is applied to a secondary battery to be charged is used. In the constant current / constant voltage charging control method, as shown in Patent Document 1 below, after the constant current charging period is over, the constant voltage charging control is started. Since the charging current drops from the constant current value, a method is generally adopted in which the secondary battery is determined to be fully charged when the charging current reaches a predetermined end current value or less.

Japanese Patent Laid-Open No. 2-192670

  However, in the constant current / constant voltage charging control system, the secondary battery exhibits different charging characteristics depending on the material, structure, manufacturing method, etc. of the battery, so the end current is simply set to a predetermined value according to the battery type. If only the full charge is determined by setting and determining whether or not the charging current has dropped to the set predetermined value, there is a case where appropriate charging is not performed due to the difference in charging characteristics depending on the type of the secondary battery.

For example, when charging a lithium ion battery with constant current / constant voltage charging control, when charging a secondary battery with a high internal resistance, the rate of increase in battery voltage is higher than that with a relatively low internal resistance. Because it becomes high, it reaches a constant voltage at an early point. In this case, after the battery voltage reaches a constant voltage by constant current charging, when the charging current drops every moment and decreases below a predetermined current value (end current value), it is determined that the battery is fully charged and the charging is terminated. On the other hand, when charging a secondary battery having a relatively low internal resistance, since the rate of increase in battery voltage is low, charging is performed at a constant current for a relatively long time. When it further decreases to the end current value set to be the same as the case, it is determined that the battery is fully charged and charging is terminated. As a result, as shown in the charging characteristic diagram of FIG . 4 , the charging time tc2 at the constant current Ic in the battery with the small internal resistance RS becomes longer than the constant current charging time tc1 in the battery with the large internal resistance RL.

As described above, according to the study of the present inventor, since the charging characteristics are different based on the difference in the internal resistance of the secondary battery, as shown in FIG. 4 , the charging at the constant voltage charging after the constant current charging is performed. If the end-of-current current is uniformly set to the predetermined value Ir and full charge is determined, when charging a secondary battery with a large internal resistance, sufficient charge is not performed and the charge capacity is insufficient. I found out that That is, it has been found that the conventional full charge discrimination method may not be able to secure a sufficient nominal capacity of the secondary battery.

  Accordingly, an object of the present invention is to solve such a problem by using a charging device for charging a secondary battery such as a lithium ion battery by a constant current / constant voltage charging control method. There is to charge.

  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.

The present invention is a charging device for charging a secondary battery by a constant current / constant voltage charging control method, a charging current control circuit for energizing the constant current, and a charging voltage control for applying the constant voltage And a control circuit device for controlling the charge current control circuit and the charge voltage control circuit, wherein the charge current drops from a predetermined constant current value (Ic) to a first end current value (Iq) When the battery voltage (Vx) when a predetermined time (td) has elapsed since the start of charging is determined, the control circuit device performs charging when the battery voltage (Vx) exceeds a predetermined value. When the time from the start to the constant current charging and the end of the constant current charging to the transition to the constant voltage charging is equal to or shorter than a predetermined time (tc), the end current of the full charge determination is set as the first end current. The second terminal power smaller than the value (Iq) Has one of the features to detect the full charge is set to a value (Ip).

According to another feature of the present invention, the charging device includes a cell number determination circuit for determining the number of cells of the secondary battery, and the control circuit device is configured such that the number of cells is equal to or greater than a predetermined number (a). The first end current value is set to a current value Iq ′ (Iq ′> Iq) larger than the first end current value Iq, and the second end current value is set from the second end current value Ip. The purpose is to set a large current value Ip ′ (Ip ′> Ip) .

According to the above feature of the present invention, in a charging device for charging a secondary battery by a constant current / constant voltage charging control method, it is determined that the battery is fully charged based on the battery voltage, battery temperature, etc. of the secondary battery to be charged. Therefore, the end current value can be changed according to the characteristics of the secondary battery, and charging can be performed so as to have an appropriate battery capacity.
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.

  First, a circuit configuration of a charging device according to an embodiment of the present invention will be described with reference to the circuit diagram shown in FIG.

  In FIG. 1, a battery pack (secondary battery) 2 to be charged by a charging device 300 detects a single or a plurality of rechargeable lithium ion battery cells 2 a and a battery temperature in the battery pack 2. Therefore, it comprises a temperature sensitive element 2b functioning as a temperature detection sensor such as a thermistor disposed in contact with or in proximity to the battery cell 2a. Furthermore, the battery pack 2 has a battery type discriminating means 2c for discriminating the number of battery cells 2a. In the present embodiment, the battery type discriminating means 2c is composed of the resistor 2c having a resistance value that differs depending on the battery type. However, the battery type may be displayed by a type code and the code may be read out. For example, the battery pack 2 includes a battery cell 2a in which four lithium ion batteries (cells) having a nominal voltage of 3.6V are connected in series (4 cells), and its output voltage is 14.4V.

  A charging power supply circuit (first power supply circuit) 200 for supplying charging power to the battery pack 2 includes a first rectifying / smoothing circuit 10, a switching power supply circuit 20, and a second rectifying / smoothing circuit 30. The

  The first 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 power supply circuit 20 includes a high-frequency transformer 21, a MOSFET (switching element) 22 connected in series to a primary coil of the transformer 21, and PWM control for modulating the pulse width of a drive pulse signal applied to the gate electrode of the MOSFET 22. IC (switching control IC) 23. The PWM control IC 23 controls the start and stop of the charging operation of the MOSFET 22 based on the control input signals input from the charge control signal transmission means 4 and the charge feedback signal transmission means 5 made of a photocoupler, and is applied to the gate electrode of the MOSFET 22. By changing the drive pulse width to be supplied, the ON time of the MOSFET 22 is controlled, and the output voltage of the rectifying and smoothing circuit 30 and the charging current of the battery pack 2 are adjusted. The second rectifying / smoothing circuit 30 includes diodes 31 and 32 connected to the secondary coil side of the transformer 21, a choke coil 33, a smoothing capacitor 34, and a discharging resistor 35.

  A battery pack 2 for charging is connected to the output side 30a of the charging power supply circuit 200. On the other hand, charging current control circuit 60 and constant voltage control circuit 80 are electrically connected to charging power supply circuit 200.

  The charging current control circuit 60 includes operational amplifiers (operational amplifiers) 61a and 61b, input resistors 62 and 64 of the operational amplifiers 61a and 61b, feedback resistors 63 and 65 of the operational amplifiers 61a and 61b, and a resistor 66 constituting a charging current setting circuit. And an operational amplifier multistage connection circuit comprising a resistor 67 and an output circuit comprising a diode 69 and a diode current limiting resistor 68. An output voltage (Vcc) of a constant voltage power supply 100 (described later) that supplies power to the drive power supply Vcc of the microcomputer 50 or the like is applied to the voltage dividing resistors 66 and 67 that provide a set potential corresponding to the set charge current. The input side of the charging current control circuit 60 is connected to the current detecting means 3 comprising a resistor for detecting the charging current of the battery pack 2. Further, as described above, the output side controls the PWM control IC 23 via the charging feedback signal transmission means 5 comprising a photocoupler. Based on such a configuration, the charging current control circuit 60 controls the charging current supplied to the battery pack 2 to a constant current value. The output of the operational amplifier 61a is input to an A / D converter (A / D port) 52, and the value is taken as a current value in the microcomputer 50.

  The constant voltage control circuit 80 includes an operational amplifier 81, an input resistor 82 on the inverting input terminal (−) side, a feedback resistor 84, an input resistor 83 on the non-inverting input terminal (+) side, a diode 89, and a diode current limiter. And an output circuit composed of a resistor 85. The input side of the constant voltage control circuit 80 is connected to the output voltage detection circuit 40 of the charging power source composed of the resistor 41 and the resistor 42, and the feedback detection voltage on the output side 30a of the charging power source circuit 200 described above is input. The output side controls the PWM control IC 23 via the charge feedback signal transmission means 5 formed of a photocoupler, similarly to the output side of the charging current control circuit 60. Therefore, the PWM control IC 23 is controlled by the output signal (feedback signal) of the charging current control circuit 60 or the constant voltage control circuit 80.

  Further, an output voltage setting circuit 80 a is connected to the non-inverting input terminal of the operational amplifier 81 through a resistor 83. The output voltage setting circuit 80a includes resistors 86 to 88. The set voltage supplied from the output voltage setting circuit 80a to the non-inverting input (+) of the operational amplifier 81 connects one end of the resistor 88 to an output port 53b of the microcomputer 50, which will be described later, and outputs a high or low signal from the output port 53b. Thus, it is controlled whether or not the resistor 88 is connected to the resistor 87 in parallel. As a result, charging voltage values with different numbers of cells are set. The output voltage of the second rectifying and smoothing circuit 30 (voltage of the output terminal 30a) is controlled to a predetermined output voltage value by the feedback action of the constant voltage control circuit 80 according to the set voltage value.

  Therefore, the constant voltage control circuit 80 and the output voltage setting circuit 80a constitute an output voltage control circuit for setting the output voltage of the charging power supply circuit 200.

The operations of the charging power supply circuit 200, the charging current control circuit 60, the constant voltage control circuit 80, the output voltage setting circuit 80a, the battery temperature detection circuit 70, and the like are controlled by a microcomputer (control circuit device) 50.
In addition to a CPU (Central Processing Unit) 51 that executes a control program, the microcomputer 50 is a control program for the CPU 51, data related to the battery type of the battery pack 2, and a secondary that serves as a reference as shown in FIGS. For the battery, the set value of the end current required for full charge determination, the reference value of the battery voltage (Vo) before charging, the reference value of the battery temperature (To) before charging, the discriminating value of the constant current charging time (tc) , A read-only memory (ROM) 55 for storing a relationship with the detection time discrimination value (Vx) and the like, and a random access memory (RAM) 56 used as a work area of the CPU 51, a temporary data storage area, and the like. , And a timer 57 used for measuring charging time and the like. Further, the microcomputer 50 converts the analog input signal detected by the battery type discrimination resistor 2c and resistor 6, the battery voltage detection circuit 7 and the battery temperature detection circuit 70 into a digital output signal. An output port 53b for outputting a control signal to the output voltage setting circuit 80a, an output port 53a for outputting a control signal for controlling start or stop of charging to the charge control signal transmitting means 4, and power-on And a reset input port 54 for inputting a reset signal.

  The temperature sensing element 2b of the battery pack 2 is connected to a battery temperature detection circuit 70 composed of series resistors 71 and 72 to which the drive power supply voltage Vcc is fed, and converts the temperature change of the resistance value into a voltage. Input to the D converter 52.

  Since the battery type discrimination resistor 2c of the battery pack 2 has a resistance value corresponding to the number of cells of the battery pack 2 as described above, a voltage dividing circuit is configured with the resistor 6 having one end connected to the drive power source Vcc. The divided voltage is input to the A / D converter 52 of the microcomputer 50, and the microcomputer 50 determines the type of battery (number of cells) of the battery pack 2.

  The battery voltage of the battery pack 2 is divided as a detection voltage by the battery voltage detection circuit 7 including the voltage dividing resistors 7 a and 7 b and is input to the A / D converter 52 of the microcomputer 50.

  A control signal for starting or stopping charging of the battery pack 2 is supplied from the output port 53a to the control input of the PWM control IC 23 via the charge control signal transmission means 4 in accordance with the control program of the microcomputer 50. If a charge start control signal is received from the charge control signal transmission means 4, the PWM control IC 23 causes the MOSFET 22 to start a switching operation. Conversely, if a charge stop control signal is received, the MOSFET 22 stops the switching operation.

  The constant voltage power supply 100 includes a driving power supply voltage Vcc for the microcomputer 50, the charging current control circuit 60, the charging voltage control circuit 80 (including the charging voltage setting circuit 80a), the battery temperature detection circuit 70, the battery type discrimination detection resistor 6 and the like. Provided to supply. The power source 100 is branched from a first rectifying / smoothing circuit 10 that rectifies the commercial AC power source 1 and is provided as a second power source circuit that is different from the charging power source circuit 200 that is the first power source circuit.

  The constant voltage power supply 100 includes a power supply transformer 102, a switching power supply IC (including a PWM control IC and FET) 101 provided in a closed circuit of the primary coil 102a of the power supply transformer 102, and a pulse generated by the switching power supply IC101. It comprises a rectifier diode 103 and a smoothing capacitor 104 for rectifying the voltage on the secondary coil 102b side of the power transformer 102, a feedback circuit device 105, a shunt regulator 106, voltage dividing resistors 107 and 108 for setting an output voltage, and a smoothing capacitor 109. The circuit includes a constant voltage circuit, a constant voltage output circuit that outputs a constant voltage Vcc composed of a three-terminal regulator 110 and a smoothing capacitor 111, and a reset IC 112 provided on the constant voltage output side. The reset IC 112 of the constant voltage power supply 100 has a function of outputting a reset signal to the reset input port 54 of the microcomputer 50 in order to put the microcomputer 50 in an initial state when the power is turned on.

  The DC power supply circuit 90 is a power supply circuit for driving the PWM control IC 23, and includes a rectifying diode 91 and a smoothing capacitor 93 connected to the second secondary coil 92 of the power transformer 102. The charging power supply circuit 200 is configured as a separate power supply circuit.

  The display circuit 120 is provided to display the state of charge of the battery pack 2, and includes, for example, a display circuit 121 including a red LED (R) and a green LED (G), and a resistor 122 that limits the current of the display circuit 121. 123. The display circuit 120 turns on the red LED (R) or green LED (G) in response to an output signal from the output port 53b of the microcomputer 50, and further causes both LEDs (R) and (G) to emit light simultaneously. To light up orange. In this embodiment, the microcomputer 50 controls the red light before charging, the orange light during charging, and the green light when charging ends.

As shown in FIG. 4 , according to the conventional charging characteristic diagram, the termination current Ir is uniformly set, and the charging time of the constant current Ic or the rate of increase of the battery voltage is determined according to the internal resistance (RL or RS) of the battery. Changes significantly. That is, the battery (RL) having a large internal resistance has a shorter charging time tc of the constant current Ic than the battery (RS) having a small internal resistance (tc1 <tc2). On the other hand, the battery voltage (detection voltage) Vx after the predetermined time td has elapsed. At this time, conventionally, regardless of the internal resistance of the secondary battery (RL or RS), the end current for determining full charge is determined to be uniformly set to Ir. As a result, there was a problem that sufficient charge capacity could not be secured.

In the present invention, focusing on such charging characteristics, as shown in the charging characteristics diagram of FIG. 2, the time tc during which charging is performed with this constant current Ic is caused by the magnitude (RL or RS) of the internal resistance. For example, the magnitude of the charging time tc of the constant current Ic is detected, and a plurality of end current values (Ip or Iq) for determining full charge are set according to the magnitude of the charging time tc.

  On the other hand, as shown in the charging characteristic diagram of FIG. 2, the battery (RL) having a large internal resistance has a higher battery voltage increase rate than the battery (RS) having a small internal resistance. A later battery voltage Vx is detected, and a plurality of end current values according to the battery type are set according to the magnitude of the battery voltage Vx.

Here, attention is paid to the fact that the length of the constant current charging time tc or the degree of increase of the battery voltage Vx differs depending on the battery voltage Vo (remaining capacity) before charging and the battery temperature (To) before charging. Determine the magnitude of the end current. That is, as shown in FIG. 2, the battery voltage Vo before charging, i.e. the larger the remaining battery capacity, or because the degree of rise of the battery temperature To lower the battery voltage Vx is large, in the present invention, the battery voltage Depending on the value of Vx, the set value (Ip or Iq) of the end current for full charge determination is properly used.

The a ROM (storage unit) 55 of the microcomputer 50, the lithium-ion battery as a reference (2), the reference value of the battery voltage Vo before charging (battery voltage per cell) and (comparison value), the pre-charging the battery A correlation between a reference value of temperature (To), a discriminating value of constant current charging time (tc), and an end current setting value (Ip or Iq) for full charging determination is stored . When charging the secondary battery, the battery voltage Vo before charging, the battery temperature To before charging, the charging voltage Vx after elapse of time td, the charging time tc of constant current, etc. are measured by the CPU 51 and timer 57 of the microcomputer 50, Record and compare with reference value or discriminant value.

Next, the operation of the charging apparatus 300 according to the above embodiment will be described with reference to the control flowchart shown in FIG .
When the power is turned on, the microcomputer 50 initially sets the output ports 53a and 53b. Next, the display circuit 120 indicates that the battery is not charged by lighting in red. In this embodiment, a high signal is output from the output port 53b of the microcomputer 50 connected to the resistor 122 of the display circuit 120, and the display circuit 120 is lit in red to indicate that it is before charging (step 301).

  Next, it is determined whether or not the secondary battery 2 is connected to the output terminal 30a of the charging device 300 (step 302). The connection of the secondary battery 2 is detected, for example, when the value of the A / D converter 52 of the microcomputer 50 input via the battery temperature detection circuit 70 is changed, to which the secondary battery 2 is connected. do it. When the secondary battery 2 is connected, the microcomputer 50 stores the battery voltage Vo before the start of charging from the value of the A / D converter 52 input via the battery voltage detection circuit 7, and the battery temperature detection circuit The value of battery temperature To before charging is stored from the value of A / D converter 52 input via 70 (step 303).

  Next, the number of cells is discriminated from the value of the A / D converter 52 of the microcomputer 50 inputted through the cell number discriminating means 6 composed of a resistor, and the resistance 88 of the charging voltage control circuit 80 is applied to the determined number of cells. A high or low signal is output from the output port 53b of the continuous microcomputer 50, and the output voltage is set (step 304). For example, if it is determined in step 304 that there are 3 cells, a low signal is output from the output port of the microcomputer 50 connected to the resistor 88, and if it is determined that there are 4 cells, each cell number is output by outputting a high signal. Set the output voltage according to.

  Next, a high signal is output from the output port 53a, and charging is started by transmitting the output signal to the PWM control IC (switching power supply IC) 23 via the charging control signal transmitting means 4 (step 305). . When charging is started, the display circuit 120 displays that charging is in progress. In the present embodiment, a high signal is output from the output port 53b connected to the resistor 123 and the resistor 122 of the display circuit 120 to light up orange to indicate that charging is in progress (step 306).

  Next, in order to check whether or not a predetermined time has elapsed since the start of charging, it is determined whether or not a predetermined time elapsed flag is 1 (step 307). If the predetermined time elapsed flag is not 1, it is determined whether or not a predetermined time has elapsed since the start of charging (step 308). When it is determined in step 308 that the predetermined time has elapsed (in the case of YES), the process proceeds to step 309, where the predetermined time elapsed flag is set to 1, and it is determined whether or not the battery voltage is equal to or higher than a predetermined value (step 310). In step 310, it is determined whether or not the internal resistance of the secondary battery 2 is large from the value of the battery voltage Vx detected after the lapse of the predetermined time td.

As described above with reference to FIG. 2, the battery having a large internal resistance increases the battery voltage Vx after the predetermined time td has elapsed, compared to the battery having a small internal resistance. The magnitude of the internal resistance is determined from the degree of increase of the battery voltage Vx. Further, the degree of increase in the battery voltage Vx varies depending on the battery voltage (remaining capacity) Vo before charging and the battery temperature To. The higher the battery voltage Vo before charging or the lower the battery temperature To, the greater the increase in the battery voltage Vx. As a result, the internal resistance of the secondary battery is determined according to the magnitude of the battery voltage Vx as well as the magnitude of the battery voltage before charging, and the full charge end current discriminating value is determined according to the magnitude of the internal resistance. Set. In step 310, it is determined whether or not the battery voltage Vx is equal to or higher than a predetermined value. If it is determined that the internal resistance Ri is large, the large internal resistance flag is set to 1 in step 311. In this embodiment, the battery voltage Vx is detected in a state where a charging load is applied to the battery. However, at the time of detection, the charging may be temporarily stopped and the battery voltage may be detected in a no-load state.

  If the predetermined time has not elapsed since the start of charging in Step 308 (in the case of No), or if the predetermined time elapsed flag is 1 in Step 307 (in the case of Yes), the process proceeds to Step 312 and whether constant voltage is being charged. It is determined whether or not the constant voltage charging flag is 1 (step 312).

  If the constant voltage charging flag is not 1 in Step 312 (No), it is determined whether or not constant current charging is in progress (Step 313). Whether or not the constant current charging is being performed may be determined based on whether or not the charging current is equal to or less than a predetermined constant current value. For example, if 4A is a constant current setting value, it may be determined whether or not the current value has decreased by a predetermined value from 4A. If it is not determined in step 313 that constant current charging is being performed (in the case of No), it is determined that constant voltage charging is being performed, and the constant voltage charging flag is set to 1 (step 314).

Next, it is determined whether or not the elapsed time from the start of charging to the present, that is, the time during which constant current charging has been performed is equal to or shorter than a predetermined time tc (step 315). As is clear from the characteristic diagram of FIG. 2, the battery (RL) having a large internal resistance Ri has a higher battery voltage Vx than the battery (RS), and the higher the battery voltage Vx, the sooner the battery voltage. Reaches a constant voltage Vc, and constant voltage charging is performed. That is, the smaller the internal resistance Ri, the longer the time tc during which constant current charging is performed, and the larger the internal resistance Ri, the shorter the time tc during which constant current charging is performed. The level of the internal resistance is determined by the time during which this constant current is being performed.

  In this determination, the degree of increase (Vx) of the battery voltage varies depending on the battery voltage (remaining capacity) Vo before charging and the battery temperature To. As described above, the greater the remaining battery capacity (Vo) and the lower the battery temperature (To), the greater the degree of battery voltage increase.

If it is determined in step 315 that the elapsed time from the start of charging is equal to or less than the predetermined value tc, it is determined that the internal resistance Ri is high, and the large internal resistance flag is set to 1 (step 316).

Next, the routine proceeds to step 317, where it is determined whether or not the large internal resistance flag is 1. If a secondary battery having a high internal resistance is charged with the same charge control as that of a secondary battery having a low internal resistance, a capacity shortage occurs. That is, as is clear from the conventional characteristic diagram shown in FIG. 4 , when charging a battery (RL) having a high internal resistance in constant current / constant voltage charging of a secondary battery that is a lithium ion battery, Compared to the case of charging a battery (RS) having a relatively low internal resistance, the battery voltage rises so high that it reaches the constant voltage Vc at an early stage. When the voltage reaches the constant voltage Vc, the charging current of the constant current Ic decreases. When the charging current subsequently decreases to a predetermined current value Ir, it is determined that the battery is fully charged and charging is terminated. On the other hand, in the case of a battery (RS) having a relatively low internal resistance, since the voltage rise is low, charging is performed with a constant current for a relatively long time. When there is such a difference in charging characteristics, when a conventional determination method in which it is determined that the battery is fully charged when it drops to a predetermined current value Ir, a battery (RL) having a high internal resistance is charged. May cause a shortage of capacity. In the present invention, as shown in FIG. 2, in order to obtain an appropriate charge capacity, the end current value Ip for determining full charge when charging a battery (RL) having a high internal resistance is set to a low internal resistance. It is set smaller than the value Iq of the end current of the battery (RS).

  That is, if it is determined in step 317 that the large internal resistance flag is 1, the end current Ip is smaller than the end current Iq when it is not determined that it is 1 (step 319 and step 322).

On the other hand, reducing the end current and performing deeper charging may affect the life of the battery more than when performing shallow charging. In addition, when the number of secondary battery cells is large, it is easy to cause an imbalance in the charge capacity that affects the battery life of each cell, so that the life of the secondary battery should be extended as much as possible in charge control. Control is required. Therefore, according to this embodiment, it is determined whether or not the number of cells is equal to or greater than the predetermined number a (step 318 and step 321). If the number of cells is equal to or greater than the number a (Yes in step 318 and step 321), the termination current is shallower than the end current value Iq (large) end current value Iq '(Iq'> Iq) below drop It is determined whether it has fallen below (step 320) or less than or equal to the termination current value Ip ′ (Ip ′> Ip) shallower (larger) than the termination current value Ip (step 323). When the current reaches the end current value Iq ′ or less or the end current value Ip ′ or less, it is determined that the battery is fully charged, and the charging is terminated. As a result, shallow charging is performed, and life deterioration is suppressed.

  When charging is completed in step 324, a high signal is output from the output port 53b of the microcomputer 50 connected to the resistor 123 of the display circuit 120 in order to display the completion of charging, so that the green is turned on and the charging end is displayed. (Step 325). Thereafter, when the secondary battery 2 is removed from the charging device 300 (step 326), the process returns to step 301.

  As will be apparent from the above description of the embodiment, according to the present invention, the charging characteristics of the secondary battery are detected in advance, and the end current value for determining full charge is set according to the charging characteristics. More appropriate charging corresponding to different charging characteristics can be performed based on the battery type depending on the constituent material, structure, manufacturing method, and the like inside the battery.

  In the above embodiment, the lithium ion battery has been described as an example of the battery type of the battery pack charged by the constant current / constant voltage control. However, the present invention is applied to the constant current / constant voltage control of other battery types. May be. In addition, the lithium-ion battery can be applied to a charging method in which the charging current is controlled to be small when the battery voltage reaches the charging voltage as only constant current control. The charging time (tc) and charging at the initial charging current are The determination value may be set based on the battery voltage (Vx) after a predetermined time (td) has elapsed since the start.

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

The circuit diagram of the charging device which concerns on one Embodiment of this invention. The charge characteristic figure by the constant current and constant voltage charge by the charging device of this invention. The control flowchart of the charging device which concerns on embodiment of this invention. The charge characteristic figure by the constant current and constant voltage charge by the conventional charging device.

1: Input commercial power source 2: Battery pack 2a: Battery cell 2b: Temperature sensitive element 2c: Battery type discriminating element 3: Current detection resistor 4: Charge control signal transmission means (photocoupler) 5: Charge feedback signal transmission means (photocoupler)
6: detection resistor 7: battery voltage detection circuit 7a, 7b: voltage dividing resistor 10: first rectifying / smoothing circuit 11: full-wave rectifying circuit 12: smoothing capacitor 20: switching power supply circuit 21: high-frequency transformer 22: MOSFET
23: PWM control IC 30: second rectifying / smoothing circuit 30a: output terminal 31, 32: rectifying diode 33: choke coil 34: smoothing capacitor 35: discharging resistor 40: output voltage detecting circuit 41, 42: for voltage division Resistance 50: Microcomputer (control circuit device) 51: CPU
52: A / D port 53a, 53b: output port 54: reset input port 55: ROM 56: RAM 57: timer 60: charge current control circuit 61a, 61b: operational amplifier (operational amplifier)
62, 64: operational amplifier input resistors 63, 65: operational amplifier feedback resistors 66, 67: charge current setting voltage dividing resistors 68: resistors 69: diodes 70: battery temperature detection circuits 71, 72: voltage dividing resistors 80: Charging voltage control circuit 80a: charging voltage control circuit (output voltage control circuit) 81: operational amplifier 82, 83: operational amplifier input resistance 84: operational amplifier feedback resistance 85: output resistance 86-88: detection resistance 89: diode 90: DC power supply circuit 91: Rectifier diode 92: Secondary coil of power transformer 93: Smoothing capacitor 100: Constant voltage power supply 101: IC for switching power supply
102: power transformer 102a: primary coil 102b of the power transformer 102: secondary coil of the power transformer 103: rectifier diode 104: smoothing capacitor 105: feedback circuit device 106: shunt regulator 107, 108: voltage dividing resistor 109: smoothing Capacitor 110: Three-terminal regulator 111: Smoothing capacitor 112: Reset IC 120: Display circuit 121: Display means (LED) 122, 123: Current limiting resistor 200: Charging power supply circuit 300: Charging device

Claims (2)

A charging device for charging a secondary battery with a constant current / constant voltage charging control method,
A charging current control circuit for energizing the constant current;
A charging voltage control circuit for applying the constant voltage;
A control circuit device for controlling the charging current control circuit and the charging voltage control circuit,
In the charging device that determines that the charging current is full when the charging current drops from the predetermined constant current value (Ic) to the first end current value (Iq), and ends the charging.
The control circuit device has a battery voltage (Vx) when a predetermined time (td) has elapsed from the start of charging when a predetermined value or more,
When the time from the start of charging to constant current charging until the end of the constant current charging and the transition to constant voltage charging is equal to or shorter than a predetermined time (tc), the end current of the full charge determination is set as the first end current. A full charge is detected by setting a second end current value (Ip) smaller than the value (Iq). The charging device includes a cell number determination circuit for determining the number of cells of the secondary battery, and the control circuit device has a first end current value when the number of cells is a predetermined number (a) or more. Is set to a current value Iq ′ (Iq ′> Iq) larger than the first end current value Iq, and the second end current value is set to a current value Ip ′ (Ip greater than the second end current value Ip). The charging device according to claim 1, wherein “> Ip) is set .

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