JP2021022960A - Charge/discharge control device and battery with the same - Google Patents

Abstract

To provide a charge/discharge control device which eliminates the need of a charge/discharge switching mechanism between a DC bus and a battery and is capable of preventing overvoltage and overcurrent of the battery.SOLUTION: A charge/discharge control device is connected between a DC bus and a battery by first to fourth terminals and controls charge and discharge of the battery. The first and second terminals are connected, and at least a reactor and first and second switch elements which are connected to one end and the other end of the reactor are connected in series between the third and fourth terminals. The device includes a first rectification element which is connected between the one end of the reactor and the first and second terminals, and a second rectification element which is connected between the other end of the reactor and the first and second terminals. The first and second switch elements are connected in such a manner that body diodes thereof are directed reverse to each other, and each of the switch elements includes a control end at which the conduction or cutoff is controlled by a PWM signal.SELECTED DRAWING: Figure 1

Description

The present invention relates to a charge / discharge control device that is arranged between a battery and a DC bus and controls charging / discharging of the battery by a voltage between the DC buses.

A DC power supply and a load device are connected to the DC bus. The voltage of the DC bus fluctuates within the range in which the load device can operate normally. Therefore, when connecting the DC bus and the battery, it is necessary to detect the magnitude relationship between the DC bus and the battery voltage and switch between charging and discharging accordingly.

Further, in charging and discharging the battery, it is necessary to limit the magnitude of the current in order to prevent the deterioration of the battery. For this purpose, for example, in Patent Document 1 and the like, the reactor and the switch element are connected in series between the battery and the DC bus, and the switch element is controlled by PWM (Pulse Width Modulation).

JP-A-2007-259633

However, if the magnetic energy stored in the reactor during the on period of the switch element is released to the outside during the off period of the switch element, for example, if it is consumed by a resistor connected to the DC bus, the energy is wasted.

From the above situation, it is an object of the present invention to provide a charge / discharge control device that does not require a charge / discharge switching mechanism between a DC bus and a battery and does not waste energy. Preferably, it is an object of the present invention to provide a charge / discharge control device capable of preventing the occurrence of overvoltage and overcurrent in the battery.

In order to achieve the above object, the present invention provides the following configurations.
-Aspects of the present invention are connected to a first terminal connected to one potential line of the DC bus, a second terminal connected to one pole of the battery, and the other potential line of the DC bus. In a charge / discharge control device having a third terminal and a fourth terminal connected to the other pole of the battery and controlling charging and discharging of the battery.
The first terminal and the second terminal are connected and
A reactor and first and second switch elements arranged at one end and the other end of the reactor, respectively, connected in series between the third terminal and the fourth terminal.
A first rectifying element connected between one end of the reactor and the first and second terminals,
It has at least a second rectifying element connected between the other end of the reactor and the first and second terminals, and
The first and second switch elements each have a built-in body diode and are connected so that the body diodes are in opposite directions to each other, and each switch element is controlled to conduct or cut off by a PWM signal. It has a control end.
-In the above aspect, the first detection mechanism for detecting the battery voltage of the battery and
A second detection mechanism that detects the charge current or discharge current flowing through the battery, and
A first that controls the control end of the first switch element based on the detection value of the battery voltage detected by the first detection mechanism and the detection value of the current detected by the second detection mechanism. The first PWM signal generation unit that generates the PWM signal of
A second that controls the control end of the second switch element based on the detected value of the battery voltage detected by the first detection mechanism and the detected value of the current detected by the second detection mechanism. It is preferable to have a second PWM signal generation unit that generates the PWM signal of the above.
-In the above aspect, it is preferable that the first detection mechanism comprises two resistors that divide the battery voltage.
-In the above embodiment, it is preferable that the second detection mechanism includes one resistance element through which a charging current and a discharging current flow.
In the above embodiment, when the detected value of the battery voltage approaches the upper limit or the lower limit, or when the detected value of the current approaches the upper limit, the first PWM signal or the second PWM signal is correspondingly. It is preferable to gradually reduce the duty ratio.
-In the above embodiment, when the detected value of the battery voltage reaches the upper limit or the lower limit, or when the detected value of the current reaches the upper limit, the first PWM signal or the second PWM is correspondingly. It is preferable that the duty ratio of the signal is zero.
-Another aspect of the present invention is a battery provided with the charge / discharge control device of any of the above aspects.

According to the present invention, a charge / discharge switching mechanism between the DC bus and the battery is unnecessary, and the occurrence of overvoltage and overcurrent in the battery can be prevented. More preferably, a charge / discharge control device that does not waste energy is realized.

FIG. 1 schematically shows an example of a circuit configuration of a charge / discharge control device according to an embodiment of the present invention. FIG. 2 shows the operation when the battery is charged. FIG. 3 shows the operation when the battery is charged. FIG. 4 shows the operation when the battery is discharged. FIG. 5 shows the operation when the battery is discharged. FIG. 6 is a diagram illustrating a voltage and current limiting operation during charging of the charge / discharge control device. FIG. 7 is a diagram illustrating a voltage and current limiting operation during discharging of the charge / discharge control device.

Hereinafter, embodiments of the present invention will be described with reference to the illustrated drawings. The battery to which the present invention is applied is, for example, a lead-acid battery in which six cells of about 2 V per cell are connected in series to obtain an output voltage of 12 V. However, the present invention is also applicable to batteries other than such lead-acid batteries, and the range of battery voltage is not limited.

(1) Circuit Configuration FIG. 1 schematically shows an example of the circuit configuration of the charge / discharge control device 10 according to the embodiment of the present invention. FIG. 1 also shows a DC bus to which the charge / discharge control device 10 is connected and a battery B.

The DC bus is represented by a high potential line LH and a low potential line LL. The voltage between the high potential line LH and the low potential line LL is indicated by Vdc. A DC power supply and a load device (not shown) are connected to the DC bus, and the voltage Vdc of the DC bus fluctuates within a range in which the load device can normally operate. Further, the battery B has a positive electrode and a negative electrode, and the battery voltage, which is a voltage between the two electrodes, is indicated by Vb.

The charge / discharge control device 10 is arranged between the DC bus and the battery B. The charge / discharge control device 10 is connected to a first terminal 1 connected to the high potential line LH of the DC bus, a second terminal 2 connected to the positive electrode of the battery B, and a low potential line LL of the DC bus. It has a third terminal 3 and a fourth terminal 4 connected to the negative electrode of the battery B. Here, as an example, the terminal 4 which is the negative electrode of the battery B is used as the grounding end, and this point is used as the reference potential.

The charge / discharge control device 10 may be connected / disconnected from the DC bus by providing an appropriate switch between the terminals 1 and 3 and the DC bus. Alternatively, the charge / discharge control device 10 may be detachable from the DC bus at terminals 1 and 3 by being connected to the DC bus via an appropriate connector. Further, the charge / discharge control device 10 and the battery B may be detachably attached to each other, or the charge / discharge control device 10 and the battery B may be integrated to form one device.

Whether the battery B is charged or discharged by the DC bus voltage Vdc is naturally determined by the magnitude relationship between the battery voltage Vb and the DC bus voltage Vdc. That is, in the case of the circuit of FIG. 1, it is determined by the mutual high-low relationship between the potential of the terminal 1 and the potential of the terminal 2 with respect to the terminal 4 which is the ground end (usually, the potential difference between the terminal 4 and the terminal 3 is compared with the voltage Vdc. Can be ignored).

First, the configuration of the main circuit through which the charge / discharge current actually flows in the charge / discharge control device 10 will be described. Terminal 1 and terminal 2 are directly connected. On the other hand, a plurality of elements are connected in series between the terminal 3 and the terminal 4.

Although not shown, in another embodiment, the terminal 3 and the terminal 4 may be directly connected, and a plurality of similar elements may be connected in series between the terminal 1 and the terminal 2.

The plurality of elements connected in series between the terminal 3 and the terminal 4 include at least the reactor L, the first switch element Q1, and the second switch element Q2. Further, in the circuit of FIG. 1, resistors Rs are connected in series between the terminals 3 and 4.

A switch element Q1 is arranged at one end of the reactor L, and a switch element Q2 is arranged at the other end of the reactor L. The switch elements Q1 and Q2 are semiconductor switch elements each having a control end. The switch elements Q1 and Q2 can conduct or cut off their respective current paths by driving the control ends with a predetermined control signal. The control signal is preferably a PWM signal. The switch element Q1 and the switch element Q2 are connected so that the directions of the main currents flowing in the conductive state are opposite to each other.

In the circuit of FIG. 1, as an example, the switch elements Q1 and Q2 are n-channel MOSFETs (field effect transistors). In the switch element Q1, the drain is connected to one end of the reactor L and the source is connected to the terminal 3. In the switch element Q2, the drain is connected to the other end of the reactor L, and the source is connected to one end of the resistor Rs.

The FET has a built-in body diode. Therefore, the switch elements Q1 and Q2 are connected so that their body diodes are opposite to each other. Even in the cut-off state of the FET, a current can flow in the direction opposite to the main current by the body diode.

The other end of the resistor Rs is connected to the terminal 4. The resistors Rs are shunt resistors for detecting the charge current or discharge current flowing through the battery B. The voltage Vs at one end of the resistor Rs is used as a current detection value. The resistors Rs are not limited to the positions shown in the figure as long as the charge / discharge current can be detected by the voltage across the resistors Rs.

Further, a diode D1 is connected between one end of the reactor L and the terminal 1 and the terminal 2, and a diode D2 is connected between the other end of the reactor L and the terminal 1 and the terminal 2. The anode of the diode D1 is connected to one end of the reactor L, the anode of the diode D2 is connected to the other end of the reactor L, and the cathodes of the diodes D1 and D2 are connected to the terminals 1 and 2. The diodes D1 and D2 are examples of rectifying elements, and other rectifying elements or rectifying circuits may be used instead.

Further, a resistor R1 and a resistor R2 are connected in series between the terminal 2 and the terminal 4. The voltage Vb1 at the connection point between the resistor R1 and the resistor R2 is a voltage divider of the battery voltage Vb. The voltage division ratio is set by the values of the resistors R1 and R2. The voltage Vb1 is used as a detection value of the battery voltage Vb.

Next, the control circuit of the charge / discharge control device 10 will be described. The control circuit includes a first detection unit 20, a second detection unit 30, and a control signal generation unit 40. Although only the principle of the control circuit will be described here, the control circuit can be realized by various circuit configurations, and can also be configured by an analog circuit or a digital circuit using a DSP or the like.

The first detection unit 20 has a first operational amplifier 21 including a non-inverting input end, an inverting input end, and an output end. The operational amplifier 21 is input with a charge current or discharge current detection value Vs at its non-inverting input end, and a battery voltage Vb detection value Vb1 is input with the inverting input terminal. The output voltage V1 at the output end of the operational amplifier 21 is given to the control signal generation unit 40.

The second detection unit 30 has a second operational amplifier 31 including a non-inverting input end, an inverting input end, and an output end. The operational amplifier 31 is input with the detection value Vb1 of the battery voltage Vb at its non-inverting input end, and is input with the detection value Vs of the charging current or the discharging current at the inverting input terminal. The output voltage V2 at the output end of the operational amplifier 31 is given to the control signal generation unit 40.

The shunt resistor Rs arranged in the main circuit is an example of a detection mechanism for detecting the detected value of the charging current or the discharging current. Similarly, the voltage dividing resistors R1 and R2 arranged in the main circuit are an example of a detection mechanism for detecting the detected value of the battery voltage Vb. The mechanism for detecting the current flowing through the main circuit and the battery voltage is not limited to these, and known mechanisms can be used.

The control signal generation unit 40 includes a first PWM signal generation unit 41, a second PWM signal generation unit 42, and a triangular wave generation unit 43.

The first PWM signal generation unit 41 generates and outputs a first PWM signal Vg1 having a predetermined duty ratio corresponding to the output voltage V1 of the first detection unit 20. Therefore, when the output voltage V1 changes, the duty ratio of the PWM signal Vg1 also changes. The output PWM signal Vg1 drives the control end of the first switch element Q1 in the main circuit. Here, as an example, in order to generate the PWM signal Vg1, a triangular wave having a constant frequency generated by the triangular wave generating unit 43 is used. By inputting the triangular wave and the output voltage V1 (or a voltage obtained by appropriately converting the triangular wave) into the comparator, a PWM signal Vg1 having a duty ratio corresponding to the output voltage V1 can be obtained. The method of generating the PWM signal is well known, and the dedicated IC for generating the PWM signal is also well known.

The second PWM signal generation unit 42 generates and outputs a second PWM signal Vg2 having a predetermined duty ratio corresponding to the output voltage V2 of the second detection unit 30. Therefore, when the output voltage V2 changes, the duty ratio of the PWM signal Vg2 also changes. The output PWM signal Vg2 drives the control end of the second switch element Q2 of the main circuit. Also in the generation of the PWM signal Vg2, the triangular wave generated by the triangular wave generation unit 43 is used as in the generation of the PWM signal Vg1 described above.

In this example, since the triangular wave generation unit 43 is shared by the PWM signal generation units 41 and 42, the configuration of the control circuit can be simplified. According to this configuration, the PWM signal Vg1 and the PWM signal Vg2 are PWM signals whose frequencies and phases match, but the duty ratio, that is, the ratio of the pulse to one cycle of the H period is independently set.

(2) Charging / Discharging Operation The charging / discharging operation of the circuit of FIG. 1 will be described with reference to FIGS. 2 to 5. As described above, the charge / discharge control device of the present invention does not include a special detection mechanism or switching mechanism for switching between the charging operation and the discharging operation of the battery. In the following, the charging operation and the discharging operation will be described, respectively, but the switching between these operations is naturally performed according to the magnitude relationship between the DC bus and the battery voltage.

(2-1) Charging Operation The operation of charging the battery B will be described with reference to FIGS. 2 and 3. When the potential of the terminal 1 is higher than the potential of the terminal 2, a charging current flows from the DC bus to the battery B.

Here, the switch element Q1 and the switch element Q2 may be constantly driven by predetermined PWM signals Vg1 and Vg2 regardless of whether charging or discharging is currently performed. That is, it is not necessary to stop the driving of the other switch element when one of the switch elements is being driven in the initiative.

FIG. 2 shows the operation of the PWM signal Vg1 in the H period (on). At this time, the switch element Q1 becomes conductive, and the charging current i1 flows through the following path.
・ Terminal 1 → Terminal 2 → Battery B → Terminal 4 → Resistor Rs → Switch element Q2 → Reactor L → Switch element Q1 → Terminal 3

The charging current i1 flows in the forward direction of the body diode of the switch element Q2. Therefore, the switch element Q2 can flow the charging current i1 regardless of the presence or absence of the PWM signal Vg2 that drives the control end thereof.

The charging current i1 supplies power to the battery B from the DC bus. The reactor L suppresses the sudden rise of the charging current i1. Further, magnetic energy is accumulated in the core of the reactor L due to the flow of the charging current i1. Since the diodes D1 and D2 are both reverse biased, no current flows.

FIG. 3 shows the operation of the PWM signal Vg1 in the L period (off). When the switch element Q1 is cut off, the charging current i1 in FIG. 2 is cut off. As a result, a counter electromotive force is generated in the reactor L, the diode D1 becomes a forward bias, and the current i2 flows in the following path.
・ Reactor L → Diode D1 → Terminal 3 → Battery B → Terminal 4 → Resistor Rs → Switch element Q2

The current i2 corresponds to a commutation current in which the reactor L tries to maintain the current i1 flowing in the H period as it is. The diode D1 acts as a commutation diode. As a result, the magnetic energy stored in the reactor L is released and given (charged) to the battery B. Therefore, the electric power from the DC bus is supplied to the battery B without waste.

(2-2) Discharge Operation The operation of the battery B during discharge will be described with reference to FIGS. 4 and 5. When the potential of the terminal 1 is lower than the potential of the terminal 2, a discharge current flows from the battery B to the DC bus. As described above, the switch element Q1 and the switch element Q2 may be constantly driven at the control end by the predetermined PWM signals Vg1 and Vg2, respectively.

FIG. 4 shows the operation of the PWM signal Vg2 in the H period (on). At this time, the switch element Q2 becomes conductive, and the discharge current i3 flows through the following path.
・ Terminal 3 → Switch element Q1 → Reactor L → Switch element Q2 → Resistor Rs → Terminal 4 → Battery B → Terminal 2 → Terminal 1

The discharge current i3 flows in the forward direction of the body diode of the switch element Q1. Therefore, the switch element Q1 can flow the discharge current i3 regardless of the presence or absence of the PWM signal Vg1 that drives the control end thereof.

Power is supplied from the battery B to the DC bus by the discharge current i3. The reactor L suppresses the sudden rise of the discharge current i3. Further, magnetic energy is accumulated in the core of the reactor L due to the flow of the discharge current i3. Since the diodes D1 and D2 are both reverse biased, no current flows.

FIG. 5 shows the operation of the PWM signal Vg2 in the L period (off). When the switch element Q2 is cut off, the discharge current i3 in FIG. 4 is cut off. As a result, a counter electromotive force is generated in the reactor L, the diode D2 becomes a forward bias, and the current i4 flows in the following path.
・ Reactor L → Diode D2 → Terminal 1 → DC bus → Terminal 3

The current i4 corresponds to a commutation current in which the reactor L tries to maintain the current flowing in the H period as it is. The diode D2 acts as a commutation diode. As a result, the magnetic energy stored in the reactor L is released and given (discharged) to the DC bus. Therefore, the electric power from the battery B is supplied to the DC bus without waste.

(3) Voltage and current limiting operation (3-1) Voltage / current limiting operation during charging The voltage and current limiting operation during charging of the charge / discharge control device 10 will be described with reference to FIG. At the time of charging, it is necessary to control the battery voltage Vs so as not to exceed a predetermined upper limit voltage so that the battery B is not overcharged. Further, it is necessary to control the charging current so as not to exceed a predetermined upper limit current. In the following description, reference numerals will be made to reference numerals in FIG.

6 (a1) to 6 (a3) are schematic views schematically explaining the voltage limiting operation during charging. The vertical axis is an arbitrary unit, and the horizontal axis is time (the same applies to the figure below).

FIG. 6A1 shows an example of fluctuations in the current detection value Vs input to the non-inverting input end of the operational amplifier 21 of the first detection unit 20 and the voltage detection value Vb1 input to the inverting input terminal. There is. For the sake of simplicity, it is assumed here that the current detection value Vs hardly changes. As the voltage detection value Vb1 rises, the potential at the inverting input end rises with respect to the potential at the non-inverting input end, so the output voltage V1 at the output end falls as shown in FIG. 6A2. .. As shown in FIG. 6A3, the PWM signal generation unit 41 is configured to generate the PWM signal Vg1 whose duty ratio gradually decreases as the output voltage V1 decreases.

Then, when the voltage detection value Vb1 reaches the upper limit value Vb1max, the duty ratio of the PWM signal Vg1 is set to be zero. As a result, when the battery voltage Vb reaches the upper limit value, the switch element Q1 is substantially cut off. Therefore, even if the voltage Vdc of the DC bus is larger than the battery voltage Vb, the battery B can be charged. It will be stopped.

6 (b1) to 6 (b3) are schematic views schematically explaining the current limiting operation during charging.
FIG. 6B1 shows an example of fluctuations in the current detection value Vs input to the non-inverting input end of the operational amplifier 21 of the first detection unit 20 and the voltage detection value Vb1 input to the inverting input terminal. There is. For the sake of simplicity, it is assumed here that the voltage detection value Vb1 hardly changes. As the current detection value Vs (which means an absolute value because it is a negative value here) increases, the potential at the non-inverting input end drops with respect to the potential at the inverting input terminal. As shown in b2), the output voltage V1 at the output end decreases. As shown in FIG. 6B, the PWM signal generation unit 41 is configured to generate the PWM signal Vg1 whose duty ratio gradually decreases as the output voltage V1 decreases.

Then, when the current detection value Vs reaches the upper limit value Vsmax, the duty ratio of the PWM signal Vg1 is set to be zero. As a result, when the charging current reaches the upper limit value, the switch element Q1 is substantially cut off, so that charging to the battery B is stopped even if the voltage Vdc of the DC bus is larger than the battery voltage Vb. Will be done.

(3-2) Voltage / Current Limiting Operation at Discharge The voltage / current limiting operation at the time of discharging of the charge / discharge control device 10 will be described with reference to FIG. 7. At the time of discharging, it is necessary to control the battery voltage Vs so as not to drop below a predetermined lower limit voltage so that the battery B does not become over-discharged. Further, it is necessary to control the discharge current so as not to exceed a predetermined upper limit current. In the following description, reference numerals will be made to reference numerals in FIG.

7 (a1) to 7 (a3) are schematic views schematically explaining the voltage limiting operation at the time of discharging.
FIG. 7A1 shows an example of fluctuations in the current detection value Vs input to the inverting input end of the operational amplifier 31 of the second detection unit 30 and the voltage detection value Vb1 input to the non-inverting input end. There is. For the sake of simplicity, it is assumed here that the current detection value Vs hardly changes. As the voltage detection value Vb1 decreases, the potential at the non-inverting input end decreases with respect to the potential at the inverting input end, so the output voltage V2 at the output end decreases as shown in FIG. 7A2. .. As shown in FIG. 7A3, the PWM signal generation unit 42 is configured to generate the PWM signal Vg2 in which the duty ratio gradually decreases as the output voltage V2 decreases.

Then, when the voltage detection value Vb1 reaches the lower limit value Vb1min, the duty ratio of the PWM signal Vg2 is set to be zero. As a result, when the battery voltage Vb reaches the lower limit value, the switch element Q2 is substantially cut off. Therefore, even if the voltage Vdc of the DC bus is smaller than the battery voltage Vb, the discharge to the DC bus will occur. It will be stopped.

7 (b1) to 7 (b3) are schematic views schematically explaining the current limiting operation at the time of discharging.
FIG. 7B1 shows an example of fluctuations in the current detection value Vs input to the inverting input end of the operational amplifier 31 of the second detection unit 30 and the voltage detection value Vb1 input to the non-inverting input end. There is. For the sake of simplicity, it is assumed here that the voltage detection value Vb1 hardly changes. As the current detection value Vs (here, a positive value) increases, the potential at the inverting input end rises with respect to the potential at the non-inverting input end, so the output at the output end is as shown in FIG. 7 (b2). The voltage V2 goes down. As shown in FIG. 7 (b3), the PWM signal generation unit 42 is configured to generate the PWM signal Vg2 whose duty ratio gradually decreases as the output voltage V2 decreases.

Then, when the current detection value Vs reaches the upper limit value Vsmax, the duty ratio of the PWM signal Vg2 is set to be zero. As a result, when the discharge current reaches the upper limit value, the switch element Q2 is substantially cut off, so that even if the voltage Vdc of the DC bus is smaller than the battery voltage Vb, the discharge to the DC bus is stopped. Will be done.

As shown in FIG. 6, the voltage / current limit control during charging is performed by the first detection unit 20 and the first PWM signal generation unit 41, while as shown in FIG. 7, the voltage during discharge. / Current limit control is performed by the second detection unit 30 and the second PWM signal generation unit 42. That is, the voltage and current limits for protecting the battery B are separately applied during charging and discharging.

The specific configuration of the embodiment of the present invention described above is not limited to the illustrated example, and various modifications can be made within a range in line with the gist of the present invention.

1 1st terminal 2 2nd terminal 3 3rd terminal 4 4th terminal 10 Charge / discharge control device 20 1st detection unit 21 1st operational amplifier 30 2nd detection unit 31 2nd operational amplifier 40 Control signal generator 41 First PWM signal generator 42 Second PWM signal generator 43 Triangle wave generator B Battery Q1, Q2 Switch element R1, R2, Rs Resistance D1, D2 Diode L Reactor

Claims (7)

A first terminal connected to one potential line of the DC bus, a second terminal connected to one pole of the battery, a third terminal connected to the other potential line of the DC bus, and a battery. In a charge / discharge control device that has a fourth terminal connected to the other pole of the battery and controls charging and discharging of the battery.
The first terminal and the second terminal are connected and
A reactor and first and second switch elements arranged at one end and the other end of the reactor, respectively, connected in series between the third terminal and the fourth terminal.
A first rectifying element connected between one end of the reactor and the first and second terminals,
It has at least a second rectifying element connected between the other end of the reactor and the first and second terminals, and
The first and second switch elements each have a built-in body diode and are connected so that the body diodes are in opposite directions to each other, and each switch element is controlled to conduct or cut off by a PWM signal. A charge / discharge control device including a control end. The first detection mechanism for detecting the battery voltage of the battery and
A second detection mechanism that detects the charge current or discharge current flowing through the battery, and
A first that controls the control end of the first switch element based on the detection value of the battery voltage detected by the first detection mechanism and the detection value of the current detected by the second detection mechanism. The first PWM signal generation unit that generates the PWM signal of
A second that controls the control end of the second switch element based on the detected value of the battery voltage detected by the first detection mechanism and the detected value of the current detected by the second detection mechanism. The charge / discharge control device according to claim 1, further comprising a second PWM signal generation unit that generates the PWM signal of the above. The charge / discharge control device according to claim 2, wherein the first detection mechanism comprises two resistors that divide the battery voltage. The charge / discharge control device according to claim 2 or 3, wherein the second detection mechanism comprises one resistance element through which a charge current and a discharge current flow. When the detected value of the battery voltage approaches the upper limit or the lower limit, or when the detected value of the current approaches the upper limit, the duty ratio of the first PWM signal or the second PWM signal is gradually reduced accordingly. The charge / discharge control device according to any one of claims 2 to 4, wherein the charge / discharge control device is characterized. When the detected value of the battery voltage reaches the upper limit or the lower limit, or when the detected value of the current reaches the upper limit, the duty ratio of the first PWM signal or the second PWM signal is set accordingly. The charge / discharge control device according to any one of claims 2 to 5, wherein the charge / discharge control device is set to zero. A battery including the charge / discharge control device according to any one of claims 1 to 6.

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