JP7449787B2 - Secondary battery charging device - Google Patents

Description

The present invention relates to a charging device for a secondary battery, and particularly to one including a charging stop switch for connecting/disconnecting power supply from the charging circuit to the secondary battery.

Conventionally, as shown in Patent Document 1, charging devices for charging secondary batteries have been designed to prevent overcharging and to prevent the effects of abnormalities on the secondary battery from occurring in the device. To prevent this, a charging stop switch is provided to stop the power supply if the voltage exceeds a predetermined value or such an abnormality occurs.

However, a semiconductor switch is normally used to stop charging in this way, and it is opened and closed each time charging starts and stops, but if it fails in the closed state, that is, in short-circuit mode, it will stop charging. There was a problem in that even if an attempt was made to open the switch, the switch could not be opened and charging to the battery could not be stopped, resulting in overcharging of the battery. In order to cope with such overcharging, it has conventionally been necessary to provide a protection device for each secondary battery to be charged, which has caused issues such as cost.

JP2000-341871

The present invention has been made to solve the above-mentioned problems, and provides a charging method that can reliably stop charging even if the charging stop switch fails, without providing a protective device on the secondary battery side. The purpose is to provide equipment.

The first invention according to the present application includes a secondary battery,
a charging circuit that supplies power to the secondary battery;
a first switch element that opens and closes to connect/disconnect power supply from the charging circuit to the secondary battery;
a control device that controls opening and closing of the first switch element;
Equipped with
The charging circuit includes a constant voltage circuit section that maintains an output voltage applied between both electrodes of the secondary battery at a predetermined charging setting voltage during charging,
The constant voltage circuit section is
a first resistance section that divides the output voltage; and a second resistance section connected in series to the low voltage side of the first resistance section;
a third resistance section that divides the voltage held constant; and a fourth resistance section connected in series to the low voltage side of the third resistance section;
an intermediate voltage defined as a voltage at a connection point between the first resistance section and the second resistance section; and a reference voltage defined as a voltage at a connection point between the third resistance section and the fourth resistance section. A comparator for comparison, and
The output voltage is maintained at the charging setting voltage by performing feedback control so that the difference between the intermediate voltage and the reference voltage compared with the comparator becomes zero,
At least one of the first to fourth resistance sections includes at least two fixed resistances including a first fixed resistance and a second fixed resistance, and a second switch element, and opens and closes the second switch element. It is configured as a resistance value switchable resistor section that can switch the resistance value by
The control device switches the resistance value of the resistance value switchable resistance section by opening or closing the second switch element in synchronization with a signal that opens the first switch element, thereby increasing the output voltage. This is a secondary battery charging device configured to maintain the voltage at a predetermined charge stop setting voltage that is lower than the charge setting voltage.

In addition, in this specification, the expressions described as opening and closing a switch (element) are synonymous with turning on and turning off these switches (elements), respectively.

According to the present invention, the second switch element is opened or closed in synchronization with a signal that opens the first switch element constituting the charging stop switch, and thereby the output voltage is lower than the charging setting voltage. The charging stop switch is configured to be held at a low predetermined charge stop setting voltage, so by setting the predetermined charge stop setting voltage to a low voltage that does not allow charging of the secondary battery, the charge stop switch Even if the secondary battery fails and cannot be opened, the secondary battery will not be charged, and overcharging can be prevented.

Furthermore, the first invention makes it possible to switch the resistance value of at least one of the first to fourth resistor sections constituting the constant voltage circuit section, so that the charging stop setting voltage can be changed at the timing of opening the charging stop switch. The above function can be easily achieved by slightly changing the resistance section of the constant voltage circuit section that is already in use.

As an embodiment of the resistance value switchable resistance section in the first invention, a resistance adjustment section in which a second fixed resistor and the second switch element are connected in series can be connected to the first fixed resistor in parallel. .

In this configuration, when the first resistance section is a resistance value switchable resistance section or when the fourth resistance section is a resistance value switchable resistance section, the second switch element is set to an open state during charging. and is configured to be closed in synchronization with the signal that opens the first switch element, and the second resistance section is a resistance value switchable resistance section, or the third resistance section is a resistance value switchable resistance section. , the charging stop switch is opened by configuring the second switch element to remain closed during charging and open in synchronization with a signal that opens the first switch element. The charging stop setting voltage can be generated depending on the timing.

Another aspect of the resistance value switchable resistance section in the first invention is a resistance adjustment section in which the resistance value switchable resistance section is connected in parallel to the first fixed resistance, the second fixed resistance, and the second switch element. can be configured by connecting them in series.

In this configuration, when the first resistance section is a resistance value switchable resistance section or when the fourth resistance section is a resistance value switchable resistance section, the second switch element is set to an open state during charging. and is configured to be closed in synchronization with the signal that opens the first switch element, and the second resistance section is a resistance value switchable resistance section, or the third resistance section is a resistance value switchable resistance section. , the second switch element is configured to remain closed during charging and to be opened in synchronization with the signal that opens the first switch element, so that the charging stop switch can be similarly activated. The charging stop setting voltage can be generated at the timing of opening.

The second invention of the present application is a secondary battery,
a charging circuit that supplies power to the secondary battery;
a first switch element that opens and closes to connect/disconnect power supply from the charging circuit to the secondary battery;
a control device that controls opening and closing of the first switch element;
Equipped with
The charging circuit includes a constant voltage circuit section that maintains an output voltage applied between both electrodes of the secondary battery at a predetermined charging setting voltage during charging,
The constant voltage circuit section is
a first resistance section that divides the output voltage; and a second resistance section connected in series to the low voltage side of the first resistance section;
a comparator that compares an intermediate voltage defined as a voltage at a connection point between the first resistance section and the second resistance section with a predetermined reference voltage;
The output voltage is maintained at the charging voltage by performing feedback control so that the difference between the intermediate voltage and the reference voltage compared with the comparator becomes zero,
At least one of the first and second resistance sections includes at least two fixed resistances including a first fixed resistance and a second fixed resistance, and a second switch element, and opens and closes the second switch element. It is configured as a resistance value switchable resistor section that can switch the resistance value by
The control device switches the resistance value of the resistance value switchable resistance section by opening or closing the second switch element in synchronization with a signal that opens the first switch element, and thereby switches the resistance value of the resistance value switchable resistance section. This is a secondary battery charging device configured to maintain an output voltage at a predetermined charge stop setting voltage that is lower than the charge setting voltage.

According to the present invention, similarly to the first invention, the second switch element is opened or closed in synchronization with the signal that opens the first switch element constituting the charge stop switch, and thereby the output voltage is Since it is configured to maintain a predetermined charging stop setting voltage that is lower than the charging setting voltage, by setting the predetermined charging stop setting voltage to a low voltage that does not allow charging of the secondary battery. Even if the charge stop switch fails and cannot be opened, the secondary battery will not be charged and overcharging can be prevented.

Moreover, this second invention also allows the resistance value of at least one of the first or second resistor section constituting the constant voltage circuit section to be changed, so that the charging stop setting voltage can be changed at the timing of opening the charging stop switch. The above function can be easily achieved by simply changing the resistance section of the constant voltage circuit section that is already in use.

As an embodiment of the resistance value switchable resistance section in the second invention, a resistance adjustment section in which a second fixed resistor and the second switch element are connected in series can be connected in parallel to the first fixed resistor. .

In this configuration, when the first resistance section is a resistance value switchable resistance section, the second switch element is held open during charging and is closed in synchronization with the signal that opens the first switch element. and when the second resistance section is a resistance value switchable resistance section, the second switch element is held in a closed state during charging and synchronized with a signal that opens the first switch element. By configuring the charging stop switch to be opened, the charging stop setting voltage can be generated at the timing when the charging stop switch is opened.

Another aspect of the resistance value switchable resistance unit in the second invention is a resistance adjustment unit in which the resistance value switchable resistance unit is connected in parallel to the first fixed resistor, the second fixed resistance, and the second switch element. can be configured by connecting them in series.

In this configuration, when the first resistance section is a resistance value switchable resistance section, the second switch element is held open during charging and is closed in synchronization with the signal that opens the first switch element. When the second resistance section is a resistance value switchable resistance section, the second switch element is held in a closed state during charging and is synchronized with a signal that opens the first switch element. By configuring the switch to be opened, it is possible to generate the charging stop setting voltage at the timing when the charging stop switch is opened.

Preferably, the charging circuit includes a constant current circuit section. This allows charging at a constant voltage and constant current.

Further, it is preferable that the set voltage at the time of charging stop is set to be equal to or lower than the overdischarge battery voltage so as not to charge the secondary battery.

FIG. 1 is a schematic circuit diagram showing a first embodiment of a secondary battery charging device according to the present disclosure. FIG. 2 is a diagram showing the opening/closing timing of the first switch element and the second switch element, as well as the time change of the output voltage and the time change of the charging current, in the first embodiment. FIG. 3 is a schematic circuit diagram showing a constant voltage circuit section of the third embodiment. FIG. 4 is a schematic circuit diagram showing a constant voltage circuit section of the fourth embodiment. FIG. 5 is a diagram showing the opening/closing timing of the first switch element and the second switch element, as well as the time change of the output voltage and the time change of the charging current, in the third embodiment. FIG. 6 is a schematic circuit diagram showing a constant voltage circuit section of the fourth embodiment. FIG. 7 is a schematic circuit diagram showing a secondary battery charging device according to the fifth embodiment. FIG. 8 is a schematic circuit diagram showing a constant voltage circuit section of the sixth embodiment.

As shown in FIG. 1, the charging device 10 of the first embodiment has a charging circuit 1 that supplies power to a secondary battery 20, and a charging circuit 1 that opens and closes to connect and disconnect the power supply from the charging circuit 1 to the secondary battery 20. It includes a first switch element S1 and a control device 5 that controls opening and closing of the first switch element S1. The charging circuit 1 includes a constant voltage circuit section 2 that maintains the output voltage Vout applied between both poles of the secondary battery 20 at a predetermined charging setting voltage Vcg during charging. Further, the constant voltage circuit section 2 is provided with a second switch element S2 as described later.

The secondary battery 20 is usually configured by connecting a plurality of cells in series, and can thereby generate a predetermined voltage. Further, the first switch element S1 and the second switch element S2 are configured of semiconductor switches, for example. The first switch element S1 is configured to keep the voltage of the secondary battery 20 at a predetermined level in order to prevent overcharging and to prevent the influence from reaching the secondary battery 20 when an abnormality occurs in the charging device 10. If the value is exceeded or an abnormality occurs, it functions as a charging stop switch to stop the power supply. Opening and closing of the first switch element S1 is controlled by outputting a signal from the control device 5.

The control device 5 controls the entire charging device 10, and has a function of inputting voltage and temperature signals of the secondary battery 20 and determining and detecting an abnormality.Based on the determination, the control device 5 controls the first switch. A signal is output to each part of the charging device 10 including the element S1 and the second switch element S2 to control them.

Further, the charging process is preferably performed under a constant current, and therefore, the charging device 10 preferably includes a constant current circuit section 3 in addition to the constant voltage circuit section 1. In this embodiment, although details are not shown, a constant current circuit section 3 is provided, and its control is performed, for example, by detecting a voltage proportional to the charging current during charging and performing feedback control so that this voltage becomes a predetermined voltage. It is done by doing.

Next, the constant voltage circuit section 2 of this embodiment will be explained in detail. The constant voltage circuit section 2 is of a feedback type, and includes a first resistor R1 that divides the output voltage Vout, a second resistor R2 connected in series to the low voltage side of the first resistor R1, and a constant voltage Vout. A comparator 4 is provided.

The comparator 4 has an intermediate voltage Vm defined as the voltage at the connection point P1 between the first resistance section R1 and the second resistance section R2, and a voltage at the connection point P2 between the third resistance section R3 and the fourth resistance section R4. The reference voltage Vb is compared with the reference voltage Vb defined as . The constant voltage circuit section 2 is subjected to feedback control so that the intermediate voltage Vm and the reference voltage Vb are equal to each other, and as a result, the output voltage Vout is controlled to be constant.

Therefore, in the equilibrium state, the following equation (1) holds true.

Vout=V0*r4*(r1+r2)/(r2*(r3+r4)) (1)

In Equation (1), r1 to r4 represent the values of the resistances of the first to fourth resistance parts R1 to R4 (if they are composed of a plurality of fixed resistances, their combined resistance), respectively.

Here, the first resistance section R1 to the third resistance section R3 are composed of a single fixed resistance R1 to R3, but the fourth resistance section R4 is composed of a first fixed resistance R4a and a single fixed resistance section R4, as shown in FIG. It comprises two fixed resistors R4b and a second switch element S2, and is configured by connecting in parallel a resistance adjustment unit Raj1 in which the second fixed resistor R4b and the second switch element S2 are connected in series to the first fixed resistor R4a. be done. Here, the resistance values of the first fixed resistor R4a and the second fixed resistor R4b are assumed to be r4a and r4b.

The resistance value r4 of the fourth resistance section R4 configured in this way is r4a when the second switch element S2 is in an open state. On the other hand, the resistance value r4 of the fourth resistor R4 when the second switch element S2 is in the closed state is the combined resistance value of the first fixed resistor R4a and the second fixed resistor R4b connected in parallel, so r4a It has a smaller resistance value of r4a*r4b/(r4a+r4b). That is, the fourth resistance section R4 is configured as a resistance value switchable resistance section whose resistance value changes by opening and closing the second switch element S2, and when the second switch element S2 is closed, the resistance value of the fourth resistance section R4 is changed. The resistance value r4 is switched to decrease from the resistance value r4a when it is open to r4a*r4b/(r4a+r4b).

A decrease in the resistance value r4 of the fourth resistor R4 means that the voltage at point P2 obtained by dividing the constant voltage V0 by the ratio of r3 and r4, that is, the reference voltage Vb, decreases. Since the intermediate voltage Vm at the connection point P1 between the first resistor R1 and the second resistor R2 is controlled to be equal to the reference voltage Vb, as the resistance value r4 decreases, the intermediate voltage Vm also decreases. Furthermore, since the output voltage Vout is the intermediate voltage Vm multiplied by a constant (r1+r2)/r2, the output voltage Vout is switched to decrease as the resistance value r4 decreases due to closing the second switch element S2. become. This is also clear from equation (1).

Next, the operations of the first switch element S1 and the second switch element S2 in the first embodiment will be explained.

FIG. 2 is a diagram showing the opening/closing timing of the first switch element S1 and the second switch element S2, the time change of the output voltage Vout from the charging device, and the time change of the charging current Icg, with elapsed time plotted on the horizontal axis. . 2(a) shows the opening/closing timing of the first switch element S1, FIG. 2(b) shows the opening/closing timing of the second switching element S2, FIG. 2(c) shows the temporal change in the output voltage Vout, and FIG. 2(d) shows the opening/closing timing of the first switching element S1. shows the change in charging current Icg with time.

The control device 5 also outputs a signal to the second switch element S2 to open and close it in accordance with the timing of the signal for opening and closing the first switch element S1. Here, in the first embodiment, as shown in FIG. 2(b), the second switch element S2 closes (that is, turns ON) at the timing when the first switch element S1 opens (that is, turns OFF), so-called Operates in reverse phase.

As a result of the above operation, if the output voltage Vout is controlled to be the charging setting voltage Vcg when the first switch element S1 is closed (that is, ON and charging), then the first switch element When S1 changes from ON to OFF and the second switch element S2 switches from OFF to ON in synchronization with this, the resistance value r4 of the fourth resistor R4 decreases as described above, so the output voltage Vout descend. Then, by adjusting the resistance values of the first fixed resistor R4a and the second fixed resistor R4b of the fourth resistor R4, the output voltage Vout at the time of drop becomes the predetermined charging stop setting voltage Vnc. You can leave it there. Note that the charging stop setting voltage Vnc is naturally lower than the charging setting voltage Vcg.

When the first switch element S1 is opened (turned OFF) to stop charging, the charging current is cut off by the first switch element S1 under normal conditions, so the secondary The charging current Icg to the battery 20 becomes zero. However, at this timing, there is a possibility that the first switch element S1 cannot be opened in short mode.

To deal with this problem, according to the charging device of the first embodiment, if the first switch element S1 cannot be opened (does not turn OFF) due to a failure or the like at the timing when the first switch element S1 should be opened to stop charging, the charging Even if it becomes impossible to shut off the battery, by setting the charging stop setting voltage Vnc to be lower than the actual battery voltage in steady state, no current flows to the secondary battery 20, and the charging current Icg becomes zero. Therefore, overcharging can be prevented.

FIG. 3 is a schematic diagram showing a constant voltage circuit section 2A of the charging device of the second embodiment. In the constant voltage circuit section 2 of the first embodiment, the first resistance section R1 to the third resistance section R3 are each composed of a single fixed resistance R1 to R3, and only the fourth resistance section R4 is a resistance value switchable resistance section. In contrast, in the constant voltage circuit section 2A of the second embodiment, the second resistor section R2 to the fourth resistor section R4 each consist of a single fixed resistor R2 to R4, and the first resistor The second embodiment differs from the first embodiment in that only the portion R1 is configured as a resistance value switchable resistance portion, and the other points are configured similarly to the first embodiment.

In the second embodiment, as shown in FIG. 3, the first resistance section R1 includes a first fixed resistance R1a, a second fixed resistance R1b, and a second switch element S2, similar to the fourth resistance section R4 in the first embodiment. The first fixed resistor R1a is configured by connecting in parallel a resistance adjustment unit Raj in which a second fixed resistor R1b and a second switch element S2 are connected in series.

Therefore, in the second embodiment as well, when the second switch element S2 is closed, the resistance value r1 of the first resistance part R1 decreases from the resistance value r1a when it is opened to r1a*r1b/(r1a+r1b). (r1a and r1b are the resistance values of the first fixed resistor R1a and the second fixed resistor R1b, respectively).

When the resistance value r1 of the first resistance section R1 decreases, if the output voltage Vout is constant, the voltage at the connection point P1 between the first resistance section R1 and the third resistance section R3, that is, the intermediate voltage Vm, is the same as the resistance value r1. However, since the intermediate voltage Vm is controlled to take the same value as the constant value Vb, in the second embodiment, Vm is increased by the amount that the resistance value r1 of the first resistance section R1 has decreased. The output voltage Vout is controlled to decrease to keep it constant. This can also be seen from equation (1). In this way, in the second embodiment as well, when the second switch element S2 is closed, the output voltage Vout is also switched to decrease as in the first embodiment.

As a result, as described in the first embodiment, in the second embodiment as well, the charging voltage Vcg and the charging current Icg change as shown in FIG. 2 as the first switch element S1 turns ON and OFF. Even if the charge stop switch constituted by the first switch element S1 fails and cannot be turned off, the secondary battery 20 will not be charged and overcharging can be prevented.

Next, a third embodiment will be described with reference to FIGS. 4 and 5. FIG. 4 is a schematic circuit diagram showing a constant voltage circuit section 2B of the charging device of the third embodiment. In this constant voltage circuit section 2B, the first resistance section R1, the second resistance section R2, and the fourth resistance section R4 are each composed of single fixed resistances R1, R2, and R4, and only the third resistance section R3 is a resistor. It is configured as a value-switchable resistance section.

As shown in FIG. 4, the third resistance section R3 includes a first fixed resistance R3a, a second fixed resistance R3b, and a second switch element S2. It is constructed by connecting in series a resistance adjustment unit Raj2 in which the second switch element S2 is connected in parallel. It should be noted that the configuration of this resistance value switchable resistance section is different from the above-described first embodiment and second embodiment.

In the third embodiment, the resistance value r3 of the third resistance part R3 is different from the resistance value r3a of the first fixed resistance R3a because the bypass of the resistance adjustment part Raj2 is shorted when the second switch element S2 is closed. are equal (r3a and r3b are the resistance values of the first fixed resistor R3a and the second fixed resistor R3b, respectively). On the other hand, when the second switch element S2 is open, the first fixed resistor R3a and the second fixed resistor R3b are connected in series, so that r3a+r3b. In this way, when the second switch element S2 is released from the closed state, the resistance value r3 of the third resistance portion R3 increases.

An increase in the resistance value r3 of the third resistor R3 means that the voltage at the connection point P2 between R3 and R4, which is obtained by dividing the constant voltage V0 by the ratio of r3 and r4, that is, the reference voltage Vb is , will decrease as in one embodiment. As a result, as in the first embodiment, the output voltage Vout is switched to decrease due to an increase in the resistance value r3 as the second switch element S2 is opened.

FIG. 5 is a diagram showing the opening/closing timing of the first switch element S1 and the second switch element S2, the time change of the output voltage Vout from the charging device, and the time change of the charging current Icg, with elapsed time plotted on the horizontal axis. . 5(a) shows the opening/closing timing of the first switch element S1, FIG. 5(b) shows the opening/closing timing of the second switching element S2, FIG. 5(c) shows the temporal change in the output voltage Vout, and FIG. 5(d) shows the opening/closing timing of the first switch element S1. shows the change in charging current Icg with time.

The control device 5 also outputs a signal to the second switch element S2 to open and close it in accordance with the timing of the signal for opening and closing the first switch element S1. Here, in the third embodiment, as shown in FIG. 5(b), the second switch element S2 also opens (i.e., turns OFF) at the timing when the first switch element S1 opens (i.e., turns OFF). . In this respect, it should be noted that the operation of the second switch element S2 relative to the first switch element S1 is reversed in the third embodiment compared to the first and second embodiments.

As a result of the above operation, assuming that the output voltage Vout when the first switch element S1 is closed (that is, ON and charging) is controlled to be the charging setting voltage Vcg, the first switch element S1 changes from ON to OFF, and the second switch element S2 also switches from ON to OFF in synchronization with this, as mentioned above, the resistance value r3 of the third resistor R3 increases and the output voltage Vout decreases. The voltage is controlled to be the charging stop setting voltage Vnc which is lower than the charging setting voltage Vcg. As described in the first embodiment, the ratio between the set voltage Vcg during charging and the set voltage Vnc when charging is stopped is adjusted by the settings of the first fixed resistor R3a and the second fixed resistor R3b of the third resistance section. That's right.

In this way, with the charging device of the third embodiment, as in the first and second embodiments, even if the charging stop switch fails and cannot be turned off, the charging voltage can be lowered below the battery voltage. Therefore, the secondary battery 20 is not charged and overcharging can be prevented.

Next, a fourth embodiment will be described with reference to FIG. 6. FIG. 6 is a schematic circuit diagram showing a constant voltage circuit section 1C of the charging device of the fourth embodiment. In the constant voltage circuit section 2C of the fourth embodiment, the first resistance section R1, the third resistance section R3, and the fourth resistance section R4 are each composed of a single fixed resistance R1, R3, and R4, and the second resistance section R2 Only one of the resistors is configured as a resistance value switchable resistor section.

As shown in FIG. 6, the second resistance section R2 of the fourth embodiment includes a first fixed resistance R2a, a second fixed resistance R2b, and a second switch element S2. It is configured by connecting in parallel a resistance adjustment section Raj1 in which two fixed resistances R2b and a second switch element S2 are connected in series, and in this respect, it is similar to the fourth resistance section R4 of the first embodiment.

Therefore, in the fourth embodiment, as in the first embodiment, the resistance value r2 of the second resistor R2 changes from r2a to r2a*r2b/(r2a+r2b) when the second switch element S2 is closed from the open state. Switch to decrease. Conversely, when the second switch element S2 is released from the closed state, the resistance value r2 of the second resistance portion R2 increases from r2a*r2b/(r4a+r2b) to r2a. At this time, as explained earlier, the intermediate voltage Vm at the connection point P1 is controlled to be the same value as the constant value Vb, so when the resistance value r2 of the second resistor R2 increases, Vm is kept constant. Therefore, the output voltage Vout also decreases. This can also be seen from equation (1). In this way, also in the fourth embodiment, when the second switch element S2 is opened from the closed state, the resistance value r2 increases, and therefore the output voltage Vout is switched to decrease as in the third embodiment. Become.

Here, the operation timing of the second switch element S2 of the fourth embodiment is the same as that described for the third embodiment using FIG. 5, and the second switch element The control device 5 controls S2 to also turn off.

As a result, the charging current Icg and the charging voltage Vcg also change in the same way as in the third embodiment, and even if the charging stop switch fails and cannot be turned off, the charging voltage can be lowered below the battery voltage. The next battery 20 is not charged, so overcharging can be prevented.

Next, a fifth embodiment will be described with reference to FIG. 7. FIG. 7 shows a charging device 10A of the fifth embodiment. Like the first embodiment, the charging device 10A of the first embodiment includes a charging circuit 1A that supplies power to the secondary battery 20, and a charging circuit 1A that opens and closes to connect and disconnect the power supply from the charging circuit 1A to the secondary battery 20. The charging circuit 1A includes one switch element S1 and a control device 5 that controls opening and closing of the first switch element S1, and the charging circuit 1A controls the output voltage Vout applied between the two poles of the secondary battery 20 at a predetermined charging time. It includes a constant voltage circuit section 2D that maintains the set voltage Vcg. Note that the reference numeral 3 indicates a constant current circuit section.

The constant voltage circuit section 2D includes a first resistor section R1 that divides the output voltage Vout, a second resistor section R2 connected in series to the low voltage side of the first resistor section R1, and a first resistor section R1 and the second resistor section R1. It includes a comparator 4 that compares an intermediate voltage Vm, which is the voltage at the connection point P1 with the resistor R2, and a predetermined reference voltage Vb. In the constant voltage circuit section 2D, feedback control is performed so that the intermediate voltage Vm and the reference voltage Vb become the same, and thereby the output voltage Vout is controlled to be constant.

Therefore, in the fifth embodiment as well, the following equation (2) holds true in the equilibrium state.

Vout=Vb*(r1+r2)/r2 (2)

In Equation (1), r1 and r2 represent the values of the resistances of the first resistance section R1 and the second resistance section R2 (if they are composed of a plurality of fixed resistances, their combined resistance), respectively.

Here, the first resistance section R1 is composed of a single fixed resistance R1, and the second resistance section R2 includes a first fixed resistance R2a, a second fixed resistance R2b, and a second switch element S2, The first fixed resistor R2a is configured as a resistance value switchable resistor section in which a resistance adjustment section Raj1, in which a second fixed resistor R2b and the second switch element S2 are connected in series, is connected in parallel to the first fixed resistor R2a. Here, the resistance values of the first fixed resistor R2a and the second fixed resistor R2b are assumed to be r2a and r2b.

When the second switch element S2 is released from the closed state, the resistance value r2 of the second resistor R2 configured in this way changes from r2a*r2b/(r4a+r2b) as described in the fourth embodiment. r2a increases, and as a result, the output voltage Vout decreases.

In the fifth embodiment as well, the operation timing of the second switch element S2 is the same as in the fourth embodiment, as shown in FIG. It is controlled by the control device 5 to turn off (S1 and S2 are in phase). With this configuration, even with the charging device 1A of the fifth embodiment, even if the charging stop switch fails and cannot be opened, the secondary battery 20 will not be charged and overcharging will be prevented. be able to.

Finally, a sixth embodiment that is a modification of the fifth embodiment will be described with reference to FIG. 8. FIG. 8 shows a constant voltage circuit section 2E of the sixth embodiment. As in the fifth embodiment, the constant voltage circuit section 2E includes a first resistance section R1 and a second resistance section R2 that divide the output voltage Vout, and a comparator 4 that compares the intermediate voltage Vm with a predetermined reference voltage Vb.

In this embodiment, the second resistance section R2 includes a single fixed resistance R2, and the first resistance section R1 includes a first fixed resistance R1a, a second fixed resistance R1b, and a second switch element S2. , is configured as a resistance value switchable resistance section in which a resistance adjustment section Raj2, in which a second fixed resistance R1b and the second switch element S2 are connected in parallel, is connected in series to a first fixed resistance R1a. Here, the resistance values of the first fixed resistor R1a and the second fixed resistor R1b are assumed to be r1a and r1b.

The resistance value r1 of the first resistance part R1 configured in this way is the resistance value r1 when the second switch element S2 is closed and the resistance value when the second switch element S2 is opened, as described above for the third resistance part of the third embodiment. It switches from the value r1a+r2b to decrease to r1a. As a result, in the constant voltage circuit section 2E, the intermediate voltage Vm is controlled to be equal to the reference voltage Vb, so when the second switch element S2 is closed, the same operation as described in the second embodiment is performed. , Vout switches to decrease.

As a result, in the sixth embodiment as well, as shown in FIG. 2, the operation timing of the second switch element S2 is synchronized with the opening and closing of the first switch element S1, and when the first switch element S1 opens, it closes and the second switch element S2 is closed. By opening one switch element S1 when it is closed, charging voltage Vcg and charging current Icg can be changed as shown in FIG. 2. Therefore, according to the sixth embodiment as well, even if the charging stop switch fails and cannot be opened, the secondary battery 20 will not be charged and overcharging can be prevented.

Although six typical embodiments have been shown and described above, various other embodiments are possible. However, in both embodiments, the output voltage Vout is reduced from Vcg during charging to Vnc when charging is stopped by opening or closing the second switch S2 in synchronization with the opening and closing of the first switch S1. It is said that

Various means can be considered to achieve this objective, and these means can be classified and organized as follows, by way of example.
As the first group of means, the first resistance section R1 or the fourth resistance section R4 is configured with a resistance value switchable resistance section, and when switching the first switch element S1 from closed (ON) to released (OFF), these This is a means for lowering the resistance value.
As a second group of means, the second resistance section R2 or the third resistance section R3 is configured with a resistance value switchable resistance section, and when switching the first switch element S1 from closed (ON) to released (OFF), these This is a means for increasing the resistance value.

The first group of means further includes:
The resistance value switchable resistance unit is configured by connecting in parallel a resistance adjustment unit Raj1 in which a second fixed resistance R1b, R4b and the second switch element S2 are connected in series to the first fixed resistances R1a, R4a, and , means for synchronizing the second switch element S2 in opposite phase with the operation of the first switch element S2, as shown in FIG.
The resistance value switchable resistance unit is configured by connecting in series a resistance adjustment unit Raj2 in which a second fixed resistance R1a, R4a and the second switch element S2 are connected in parallel to the first fixed resistances R1a, R4a, Furthermore, as shown in FIG. 5, the second switch element S2 can be classified into means for synchronizing the operation of the first switch element S2 in the same phase.

The second means further includes:
The resistance value switchable resistance section is configured by connecting in parallel a resistance adjustment section Raj1 in which a second fixed resistance R2b, R3b and the second switch element S2 are connected in series to the first fixed resistances R2a, R3a, and , means for synchronizing the second switch element S2 in phase with the operation of the first switch element S2, as shown in FIG.
The resistance value switchable resistance unit is configured by connecting in series a resistance adjustment unit Raj2 in which a second fixed resistance R2b, R3b and the second switch element S2 are connected in parallel to the first fixed resistances R2a, R3a, In addition, as shown in FIG. 5, the second switch element S2 can be classified into means for synchronizing the operation of the first switch element S2 in an opposite phase.

Further, in the first to sixth embodiments, only one of the plurality of resistance sections of the constant voltage circuit section is configured as a resistance value switchable resistance section, but both of the plurality of resistance sections are configured as a resistance value switchable resistance section. It can also be configured.

1, 1A Charging circuit 2, 2A, 2B, 2C, 2D, 2E Constant voltage circuit section 3 Constant current circuit section 4 Comparator 5 Control device 10, 10A Charging device 20 Secondary battery
S1 First switch element
S2 Second switch element

Claims (8)

a charging circuit that supplies power to a secondary battery;
a first switch element that opens and closes to connect/disconnect power supply from the charging circuit to the secondary battery;
a control device that controls opening and closing of the first switch element;
Equipped with
The charging circuit includes a constant voltage circuit section that maintains an output voltage applied between both electrodes of the secondary battery at a predetermined charging setting voltage during charging,
The constant voltage circuit section is
a first resistance section that divides the output voltage; and a second resistance section connected in series to the low voltage side of the first resistance section;
a third resistance section that divides the voltage held constant; and a fourth resistance section connected in series to the low voltage side of the third resistance section;
an intermediate voltage defined as a voltage at a connection point between the first resistance section and the second resistance section; and a reference voltage defined as a voltage at a connection point between the third resistance section and the fourth resistance section. A comparator for comparison, and
The output voltage is maintained at the charging setting voltage by performing feedback control so that the difference between the intermediate voltage and the reference voltage compared with the comparator becomes zero,
At least one of the first to fourth resistance sections includes at least two fixed resistances including a first fixed resistance and a second fixed resistance, and a second switch element, and opens and closes the second switch element. It is configured as a resistance value switchable resistor section that can switch the resistance value by
The control device switches the resistance value of the resistance value switchable resistance section by opening or closing the second switch element in synchronization with a signal that opens the first switch element, thereby increasing the output voltage. A charging device for a secondary battery configured to maintain the voltage at a predetermined charging stop setting voltage lower than the charging setting voltage. The resistance value switchable resistance section is configured by connecting in parallel a resistance adjustment section formed by connecting the second fixed resistance and the second switch element in series to the first fixed resistance,
When the first resistance section is a resistance value switchable resistance section, or when the fourth resistance section is a resistance value switchable resistance section, the second switch element maintains an open state during charging. and configured to be closed in synchronization with a signal that opens the first switch element,
When the second resistance section is a resistance value switchable resistance section, or when the third resistance section is a resistance value switchable resistance section, the second switch element maintains a closed state during charging. The charging device according to claim 1, wherein the charging device is configured to be opened in synchronization with a signal that opens the first switch element. The resistance value switchable resistance section is configured by connecting in series a resistance adjustment section in which the second fixed resistance and a second switch element are connected in parallel to the first fixed resistance,
When the first resistance section is a resistance value switchable resistance section, or when the fourth resistance section is a resistance value switchable resistance section, the second switch element maintains an open state during charging. and configured to be closed in synchronization with a signal that opens the first switch element,
When the second resistance section is a resistance value switchable resistance section, or when the third resistance section is a resistance value switchable resistance section, the second switch element maintains a closed state during charging. The charging device according to claim 1, wherein the charging device is configured to be opened in synchronization with a signal that opens the first switch element. a charging circuit that supplies power to a secondary battery;
a first switch element that opens and closes to connect/disconnect power supply from the charging circuit to the secondary battery;
a control device that controls opening and closing of the first switch element;
Equipped with
The charging circuit includes a constant voltage circuit section that maintains an output voltage applied between both electrodes of the secondary battery at a predetermined charging setting voltage during charging,
The constant voltage circuit section is
a first resistance section that divides the output voltage; and a second resistance section connected in series to the low voltage side of the first resistance section;
a comparator that compares an intermediate voltage defined as a voltage at a connection point between the first resistance section and the second resistance section with a predetermined reference voltage;
The output voltage is maintained at the charging voltage by performing feedback control so that the difference between the intermediate voltage and the reference voltage compared with the comparator becomes zero,
At least one of the first and second resistance sections includes at least two fixed resistances including a first fixed resistance and a second fixed resistance, and a second switch element, and opens and closes the second switch element. It is configured as a resistance value switchable resistor section that can switch the resistance value by
The control device switches the resistance value of the resistance value switchable resistance section by opening or closing the second switch element in synchronization with a signal that opens the first switch element, thereby increasing the output voltage. A charging device for a secondary battery configured to maintain the voltage at a predetermined charging stop setting voltage lower than the charging setting voltage. The resistance value switchable resistance section is configured by connecting in parallel a resistance adjustment section in which the second fixed resistance and the second switch element are connected in series to the first fixed resistance,
When the first resistance section is a resistance value switchable resistance section, the second switch element maintains an open state during charging and is closed in synchronization with a signal that opens the first switch element. It is configured like this,
When the second resistance section is a resistance value switchable resistance section, the second switch element maintains a closed state during charging and opens in synchronization with a signal that opens the first switch element. The charging device according to claim 4, configured as follows. The resistance value switchable resistance unit is configured by connecting in series a resistance adjustment unit in which the second fixed resistance and a second switch element are connected in parallel to the first fixed resistance,
When the first resistance section is a resistance value switchable resistance section, the second switch element maintains an open state during charging and is closed in synchronization with a signal that opens the first switch element. It is configured like this,
When the second resistance section is a resistance value switchable resistance section, the second switch element maintains a closed state during charging and opens in synchronization with a signal that opens the first switch element. The charging device according to claim 4, configured as follows. The charging device according to claim 1 , wherein the charging circuit includes a constant current circuit section. The charging device according to any one of claims 1 to 7 , wherein the charging stop setting voltage is equal to or lower than an overdischarge battery voltage of the secondary battery.

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