CN113824171B - Charging device for rechargeable batteries - Google Patents

Abstract

The application provides a charging device for a rechargeable battery, which can reliably stop charging without providing a protection device on the side of the rechargeable battery even if a charging stop switch fails. The constant voltage circuit unit (2) has first to fourth resistor units (R1, R4), and the fourth resistor unit (R4) is composed of two fixed resistors (R4 a, R4 b) and a switch (S2), and when the charge stop switch (S1) is turned off, the switch (S2) is turned on in synchronization therewith, so that the output voltage (Vout) of the constant voltage circuit unit (2) is reduced.

Description

Charging device for rechargeable batteries

technical field

The present invention relates to a charging device for a rechargeable battery, and more particularly to a charging stop switch for turning off and on the power supply from the charging circuit to the rechargeable battery.

Background technique

Conventionally, as shown in Patent Document 1, in a charging device for charging a rechargeable battery, in order to prevent overcharging and to prevent the influence of the device from affecting the rechargeable battery when an abnormality occurs in the device, when the voltage exceeds a specified value or occurs In case of such an abnormality, a charge stop switch is provided to stop the power supply.

However, a semiconductor switch is usually used for such a charging stop, and is used for opening and closing each time charging is started and stopped. However, when a failure occurs in the closed state, that is, in the short-circuit mode, there is a problem that even if you want to open the switch to stop charging, it cannot be opened. Unable to stop charging the battery, causing the problem of overcharging the battery. In order to cope with such overcharging, conventionally, it was necessary to sequentially install protection devices on the rechargeable battery side to be charged, and cost and the like became a problem.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2000-341871

Contents of the invention

The technical problem to be solved by the invention

The present invention was made to solve the above problems, and an object of the present invention is to provide a charging device capable of reliably stopping charging without providing a protection device on the rechargeable battery side even if a charging stop switch fails.

Technical means used to solve technical problems

The first invention involved in this application is a charging device for a rechargeable battery, comprising: a rechargeable battery;

a charging circuit, which supplies power to the rechargeable battery;

a first switching element that switches to turn off and on the power supply from the charging circuit to the rechargeable battery; and

a control device that controls the opening and closing of the first switching element,

The charging circuit has a constant voltage circuit section that maintains an output voltage applied between both electrodes of the rechargeable battery at a predetermined charging-time set voltage during charging,

The constant voltage circuit unit is configured to include:

a first resistance part for dividing the output voltage, and a second resistance part connected in series with a low-voltage side of the first resistance part;

a third resistance part for dividing the voltage to be kept constant, and a fourth resistance part connected in series to the low-voltage side of the third resistance part;

a comparator pair defined as an intermediate voltage of a voltage at a connection point between said first resistive portion and said second resistive portion, and defined as an intermediate voltage between said third resistive portion and said fourth resistive portion The voltage at the connection point between the resistive parts is compared with the reference voltage,

and the difference between the intermediate voltage obtained by comparison with the comparator and the reference voltage becomes zero through feedback control, thereby maintaining the output voltage at the set voltage during charging,

At least one of the first to fourth resistor parts is configured as a resistance value switchable resistor part, and the resistance value switchable resistor part includes at least two fixed resistors including a first fixed resistor and a second fixed resistor. and a second switching element, and the resistance value can be switched by turning the second switching element on and off,

The control device is configured to open or close the second switching element synchronously with a signal to open the first switching element to switch the resistance value of the resistance value switchable resistor portion, thereby maintaining the output voltage. The set voltage at the time of charging is lower than the set voltage at the time of charging.

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

According to the present invention, the second switching element is opened or closed synchronously with a signal to open the first switching element constituting the charging stop switch, so that the output voltage is kept lower than the charging-time set voltage. Therefore, by presetting the specified voltage when the charge is stopped to such a low voltage that the rechargeable battery cannot be charged, even if the charge stop switch fails, it cannot be Open, the rechargeable battery will not be charged, can prevent overcharging.

In addition, in the first invention, by setting at least one of the first to fourth resistors constituting the constant voltage circuit unit as a switchable resistance value, the charging stop setting voltage is generated at the timing of turning on the charging stop switch, The above functions can be easily maintained by only slightly changing the resistance part of the already used constant voltage circuit part.

As an aspect of the resistance value switchable resistance unit in the first invention, a first fixed resistance may be configured to be connected in parallel to a resistance adjustment unit obtained by connecting a second fixed resistance and the second switching element in series.

In this configuration, in the case where the first resistance part is a resistance value switchable resistance part, or in the case where the fourth resistance part is a resistance value switchable resistance part, the second switching element is configured to be kept open during charging. state, and is closed synchronously with the signal to open the first switching element, in the case where the second resistance part is a resistance value switchable resistance part, or in the case where the third resistance part is a resistance value switchable resistance part, the The second switching element is configured to maintain a closed state during charging and to be opened in synchronization with a signal to open the first switching element, so that a charge stop setting voltage can be generated at the timing of opening the charge stop switch.

As another form of the resistance value switchable resistance unit in the first invention, a resistance value changeable resistance unit can be configured by connecting the first fixed resistance in series with a resistance adjustment unit obtained by connecting the second fixed resistance and the second switching element in parallel. Switch the resistor section.

In this configuration, in the case where the first resistance part is a resistance value switchable resistance part, or in the case where the fourth resistance part is a resistance value switchable resistance part, the second switching element is configured to be kept open during charging. state, and is closed synchronously with the signal to open the first switching element, in the case where the second resistance part is a resistance value switchable resistance part, or in the case where the third resistance part is a resistance value switchable resistance part, the The second switching element is configured to maintain a closed state during charging, and is configured to be opened in synchronization with a signal that opens the first switching element, thereby similarly opening the charge stop switch.

It is possible to set the voltage when charging is stopped at regular intervals.

The second invention of the present application is a charging device for a rechargeable battery, comprising: a rechargeable battery;

a charging circuit, which supplies power to the rechargeable battery;

a first switching element that switches to turn off and on the power supply from the charging circuit to the rechargeable battery; and

a control device that controls the opening and closing of the first switching element,

The charging circuit has a constant voltage circuit section that maintains an output voltage applied between both electrodes of the rechargeable battery at a predetermined charging-time set voltage during charging,

The constant voltage circuit unit is configured to include:

a first resistance part that divides the output voltage and a second resistance part connected in series to a low voltage side of the first resistance part; and

a comparator that compares an intermediate voltage defined as a voltage at a connection point between said first resistance portion and said second resistance portion with a prescribed reference voltage,

and the difference between the intermediate voltage obtained by comparison with the comparator and the reference voltage becomes zero through feedback control, thereby maintaining the output voltage at a set voltage during charging,

At least one of the first resistor part and the second resistor part is configured as a resistance value switchable resistor part, and the resistance value switchable resistor part includes at least two fixed resistors including a first fixed resistor and a second fixed resistor. and a second switching element, and the resistance value can be switched by turning the second switching element on and off,

The control device is configured to open or close the second switching element synchronously with a signal to open the first switching element to switch the resistance value of the resistance value switchable resistor portion, thereby maintaining the output voltage. The set voltage at the time of charging is lower than the set voltage at the time of charging.

According to the present invention, similarly to the first invention, the second switching element is opened or closed in synchronization with a signal that turns on the first switching element constituting the charging stop switch, so that the output voltage is maintained at a ratio higher than the specified value. Therefore, by presetting the predetermined set voltage at the time of charging to such a low voltage that the charging of the rechargeable battery cannot be performed, even if charging is stopped If the switch fails to turn it on, the rechargeable battery will not be charged, preventing overcharging.

In addition, in the second invention, by setting at least one of the first resistor unit and the second resistor unit constituting the constant voltage circuit unit to a switchable resistance value, the set voltage at the time of charging stop is generated at the timing when the charging stop switch is turned on. Therefore, the above-mentioned function can be easily maintained only by changing the resistance part of the constant voltage circuit part already used.

As an aspect of the resistance value switchable resistance unit in the second invention, a first fixed resistance may be configured to be connected in parallel to a resistance adjustment unit obtained by connecting a second fixed resistance and the second switching element in series.

In this configuration, when the first resistance part is a resistance part whose resistance can be switched, the second switching element is configured to maintain an open state during charging and to be closed in synchronization with a signal that opens the first switching element. When the second resistance part is a resistor part whose resistance value can be switched, the second switching element is configured to maintain a closed state during charging and to be opened in synchronization with a signal to open the first switching element, so that charging can be performed when the second switching element is turned on. The timing of the stop switch produces a set voltage when charging stops.

As another form of the resistance value switchable resistance unit in the second invention, a resistance value changeable resistance unit can be configured by connecting the first fixed resistance in series to a resistance adjustment unit obtained by connecting the second fixed resistance and the second switching element in parallel. Switch the resistor section.

In this configuration, when the first resistance part is a resistance part whose resistance can be switched, the second switching element is configured to maintain an open state during charging and to be closed in synchronization with a signal that opens the first switching element. When the second resistance part is a resistor part whose resistance value can be switched, the second switching element is configured to maintain a closed state during charging and to be opened in synchronization with a signal to open the first switching element, so that the charging stop switch can be turned on. The timing produces a set voltage when charging stops.

Preferably, the charging circuit includes a constant current circuit unit. Thus, charging at a constant voltage and a constant current can be performed.

In addition, the set voltage at the time of charging stop is preferably set to be equal to or lower than the overdischarged battery voltage in order not to charge the rechargeable battery.

Description of drawings

FIG. 1 is a schematic circuit diagram showing a first embodiment of a charging device for a rechargeable battery according to the present disclosure.

2 is a diagram showing switching timings of a first switching element and a second switching element, and temporal changes of an output voltage and a temporal change of a charging current in the first embodiment.

FIG. 3 is a schematic circuit diagram showing a constant voltage circuit unit according to a third embodiment.

4 is a schematic circuit diagram showing a constant voltage circuit unit according to a fourth embodiment.

FIG. 5 is a diagram showing opening and closing timings of a first switching element and a second switching element, and temporal changes of an output voltage and a temporal change of a charging current according to a third embodiment.

FIG. 6 is a schematic circuit diagram showing a constant voltage circuit unit according to a fourth embodiment.

7 is a schematic circuit diagram showing a charging device for a rechargeable battery according to a fifth embodiment.

8 is a schematic circuit diagram showing a constant voltage circuit unit according to a sixth embodiment.

Detailed ways

As shown in FIG. 1 , a charging device 10 according to the first embodiment includes a charging circuit 1 that supplies power to a rechargeable battery 20 , and a first switch that opens and closes the power supply from the charging circuit 1 to the rechargeable battery 20 . element S1, and a control device 5 for controlling the opening and closing of the first switching element S1. The charging circuit 1 has a constant voltage circuit unit 2 that maintains an output voltage Vout applied between both electrodes of the rechargeable battery 20 at a predetermined charging setting voltage Vcg during charging. In addition, as will be described later, the second switching element S2 is provided in the constant voltage circuit section 2 .

The rechargeable battery 20 is usually configured by connecting a plurality of cells in series, thereby being able to generate a predetermined voltage. In addition, the first switching element S1 and the second switching element S2 are constituted by semiconductor switches, for example. In order to prevent overcharging, and in order to prevent its influence from affecting the rechargeable battery 20 when an abnormality occurs in the charging device 10, when the voltage of the rechargeable battery 20 exceeds a specified value or an abnormality occurs, the first switching element S1 acts as a charging device for stopping power supply. function by stopping the switch. Opening and closing of the first switching element S1 is controlled by outputting a signal from the control device 5 .

The control device 5 controls the entire charging device 10, inputs the signal of the voltage or temperature of the rechargeable battery 20, has the function of judging and detecting the abnormality, and outputs a signal to the circuit board including the first switching element S1 and the second switching element S2 based on the judgment. The various parts of the device 10 are charged to control them.

In addition, it is preferable that the charging process is performed at a constant current, and therefore, the charging device 10 preferably includes a constant current circuit portion 3 in addition to the constant voltage circuit portion 2 . In this embodiment, although not shown in detail, a constant current circuit unit 3 is provided, and this control is performed, for example, by detecting a voltage proportional to the charging current during charging and performing feedback control so that the voltage becomes a predetermined voltage. .

Next, the constant voltage circuit unit 2 of this embodiment will be described in detail. The constant voltage circuit part 2 uses a feedback circuit and includes a first resistor part R1 that divides the output voltage Vout and a second resistor part R2 connected in series with the low-voltage side of the first resistor part R1. The third resistance part R3 for dividing the voltage V0 of the third resistance part R3 , the fourth resistance part R4 connected in series with the low voltage side of the third resistance part R3 , and the comparator 4 .

The comparator 4 compares the intermediate voltage Vm defined as the voltage at the connection point P1 between the first resistor part R1 and the second resistor part R2 to the voltage defined as the connection between the third resistor part R3 and the fourth resistor part R4. The reference voltage Vb of the voltage at point P2 is compared. Then, the constant voltage circuit unit 2 performs feedback control so that the intermediate voltage Vm and the reference voltage Vb become equal, and as a result, the output voltage Vout is controlled so that the output voltage Vout becomes constant.

Therefore, in a balanced state, the following formula (1) holds.

Vout＝V0*r4*(r1+r2)/(r2*(r3+r4)) (1)

In Equation (1), r1 to r4 represent the values of the resistances of the first resistor part R1 to the fourth resistor part R4 (combined resistance when composed of a plurality of fixed resistors), respectively.

Here, the first resistor part R1 to the third resistor part R3 are composed of single fixed resistors R1 to R3, but as shown in FIG. The second switching element S2 is connected in parallel to the first fixed resistor R4a and the resistance adjustment part Raj1 obtained by connecting the second fixed resistor R4b and the second switching element S2 in series. Here, let the resistance values of the first fixed resistor R4a and the second fixed resistor R4b be r4a, r4b.

When the second switching element S2 is in the open state, the resistance value r4 of the fourth resistance portion R4 thus constituted is r4a. On the other hand, the resistance value r4 of the fourth resistance part R4 when the second switching element S2 is in the closed state is the combined resistance value of the first fixed resistance R4a and the second fixed resistance R4b connected in parallel, and therefore has a value smaller than r4a. The resistance value of r4a*r4b/(r4a+r4b). That is, the fourth resistance portion R4 is configured as a resistance value switchable resistance portion whose resistance value is changed by opening and closing the second switching element S2, and when the second switching element S2 is closed, the resistance value r4 of the fourth resistance portion R4 is switched to Let it drop from the resistance value r4a when it is turned on to r4a*r4b/(r4a+r4b).

The reduction of the resistance value r4 of the fourth resistance unit R4 means that the voltage at the 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 resistance part R1 and the second resistance part R2 is controlled to be equal to the reference voltage Vb, as the resistance value r4 decreases, the intermediate voltage Vm also decreases, and the output voltage Vout is a value obtained by multiplying the intermediate voltage Vm by a constant (r1+r2)/r2, and the resistance value r4 decreases as the second switching element S2 is closed, and the output voltage Vout also switches to decrease. This fact can also be clearly seen from the formula (1).

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

2 is a graph showing the timing of opening and closing of the first switching element S1 and the second switching element S2 , and the temporal change of the output voltage Vout from the charging device and the temporal change of the charging current Icg by using the elapsed time on the horizontal axis. Fig. 2 (a) shows the opening and closing timing of the first switching element S1 matched with time, Fig. 2 (b) shows the opening and closing timing of the second switching element S2 matching with time, Fig. 2 (c) shows the timing of opening and closing of the second switching element S2 matching with time The temporal change of the output voltage Vout is shown in accordance with time, and FIG. 2( d ) shows the temporal change of the charging current Icg in accordance with time.

The control device 5 also outputs a signal to the second switching element S2 in accordance with the timing of the opening and closing signal of the first switching element S1, and opens and closes the second switching element S2. Here, in the first embodiment, as shown in FIG. 2(b), at the timing when the first switching element S1 is opened (ie, off), the second switching element S2 is closed (ie, turned on) to perform a so-called inversion. phase action.

As a result of the above actions, if the first switching element S1 is controlled so that the output voltage Vout when it is closed (that is, turned on, charging) becomes the set voltage Vcg during charging, the first switching element S1 is turned from on to off. When the second switching element S2 is switched from off to on synchronously with this, since the resistance value r4 of the fourth resistance part R4 decreases as described above, the output voltage Vout decreases. Then, by adjusting the resistance values of the first fixed resistor R4a and the second fixed resistor R4b of the fourth resistor unit R4, the output voltage Vout at the time of reduction can be set to the preset voltage Vnc at the time of charging stop. In addition, the set voltage Vnc at the time of charging is naturally lower than the set voltage Vcg at the time of charging.

If the first switching element S1 is turned on (turned off) to stop charging, the charging current is cut off by the first switching element S1 under normal conditions, so as shown in FIG. 2(d), the charging current Icg flowing to the rechargeable battery 20 becomes zero. However, at this timing, there is a possibility that the first switching element S1 cannot be turned on in the short-circuit mode.

With respect to such a problem, according to the charging device of the first embodiment, even if the first switching element S1 is turned on and the charging should be stopped at the timing when it is supposed to be turned on (unable to be turned off) due to a failure or the like, and the charging cannot be cut off, Setting voltage Vnc when charging is stopped is set in advance to be lower than the actual battery voltage during normal time, so that no current flows in rechargeable battery 20 and charging current Icg becomes zero, thereby preventing overcharging.

FIG. 3 is a schematic diagram showing a constant voltage circuit unit 2A of a charging device according to the second embodiment. In the constant voltage circuit part 2 of the first embodiment, the first resistor part R1 to the third resistor part R3 are composed of individual fixed resistors R1 to R3, respectively, and only the fourth resistor part R4 is constituted as a resistance value switchable resistor part, On the other hand, in the constant voltage circuit section 2A of the second embodiment, instead, the second resistor section R2 to the fourth resistor section R4 are composed of individual fixed resistors R2 to R4, and only the first resistor section R1 serves as It is different from the first embodiment in that the resistance value can be switched and configured as a resistor unit, but the configuration is the same as that of the first embodiment in other respects.

In the second embodiment, as shown in FIG. 3 , the first resistor portion R1 is configured to include a first fixed resistor R1a, a second fixed resistor R1b, and a second fixed resistor R1 similarly to the fourth resistor portion R4 in the first embodiment. The switching element S2 is connected in parallel to the resistance adjustment unit Raj obtained by connecting the second fixed resistor R1b and the second switching element S2 in series to the first fixed resistor R1a.

Therefore, in the second embodiment, when the second switching element S2 is turned on, the resistance value r1 of the first resistance portion R1 is switched so as to decrease from the resistance value r1a at the time of opening to r1a*r1b/(r1a+r1b)( r1a, 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 part R1 decreases, if the output voltage Vout is constant, the voltage at the connection point P1 between the first resistance part R1 and the third resistance part R3, that is, the intermediate voltage Vm will be reduced by 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, the output voltage Vout is controlled to decrease by an amount corresponding to only the resistance value r1 of the first resistance portion R1. , so that Vm is constant. This fact is also known from formula (1). As described above, in the second embodiment, when the second switching element S2 is turned on, the output voltage Vout is switched to decrease as in the first embodiment.

Thus, as described in the first embodiment, in the second embodiment, the charging voltage Vcg and the charging current Icg also change as shown in FIG. 2 as the first switching element S1 turns on and off. As a result, even if the charging stop switch constituted by the first switching element S1 fails and cannot be turned off, the rechargeable battery 20 is not 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 unit 2B of the charging device according to the third embodiment. In this constant voltage circuit part 2B, the first resistor part R1, the second resistor part R2, and the fourth resistor part R4 are composed of single fixed resistors R1, R2, and R4, respectively, and only the third resistor part R3 is used as a resistance value switchable resistor. part to form.

As shown in FIG. 4, the third resistance part R3 is composed of a first fixed resistor R3a, a second fixed resistor R3b, and a second switch element S2, and the first fixed resistor R3a is combined with the second fixed resistor R3b and the second switch element S2. The resistance adjustment unit Raj2 obtained by connecting the elements S2 in parallel is connected in series. It should be noted that the structure of this resistance value switchable resistance portion is different from that of the first embodiment or the second embodiment described above.

In the third embodiment, in the state where the second switching element S2 is closed, the bypass of the resistance adjustment part Raj2 is short-circuited, so the resistance value r3 of the third resistance part R3 is equal to the resistance value r3a of the first fixed resistance R3a ( r3a, r3b are the resistance values of the first fixed resistor R3a and the second fixed resistor R3b respectively). On the other hand, in the state where the second switching element S2 is turned on, the first fixed resistor R3a and the second fixed resistor R3b are connected in series so that r3a+r3b. Thus, when the state of closing the second switching element S2 is released, the resistance value r3 of the third resistance portion R3 will increase.

The increase of the resistance value r3 of the third resistance part R3 refers to the voltage of the connection point P2 between R3 and R4 obtained by dividing the constant voltage V0 by the ratio of r3 and r4, that is, the reference voltage Vb is the same as that of the first embodiment. similarly lowered. As a result, as in the first embodiment, since the resistance value r3 increases as the second switching element S2 is turned on, the output voltage Vout switches to decrease.

5 is a graph showing the timing of opening and closing of the first switching element S1 and the second switching element S2 , and the temporal change of the output voltage Vout from the charging device and the temporal change of the charging current Icg using the elapsed time on the horizontal axis. Fig. 5(a) shows the opening and closing timing of the first switching element S1 matched with time, Fig. 5(b) shows the opening and closing timing of the second switching element S2 matching with time, Fig. 5(c) shows the timing of opening and closing of the second switching element S2 with time The temporal change of the output voltage Vout is shown in accordance with time, and FIG. 5( d ) shows the temporal change of the charging current Icg in accordance with time.

The control device 5 also outputs a signal to the second switching element S2 in accordance with the timing of the opening and closing signal of the first switching element S1, and opens and closes the second switching element S2. Here, in the third embodiment, as shown in FIG. 5( b ), at the timing when the first switching element S1 is turned on (ie, off), the second switching element S2 is also turned on (ie, off). In this regard, in the third embodiment, it should be noted that the operation of the second switching element S2 with respect to the first switching element S1 is opposite to that of the first and second embodiments.

As a result of the above actions, the output voltage Vout when the first switching element S1 is closed (that is, turned on, charging) is controlled to be the set voltage Vcg during charging, and the first switching element S1 changes from on to off, and accordingly Simultaneously, when the second switching element S2 is also switched from on to off, as described above, the resistance value r3 of the third resistor part R3 will increase, and the output voltage Vout will decrease and be controlled to be lower than the set voltage Vcg during charging. Set the voltage Vnc at the time of low charging stop. The ratio of the set voltage Vcg during charging to the set voltage Vnc when charging is stopped is determined by setting the first fixed resistor R3a and the second fixed resistor R3b of the third resistor section as described in the first embodiment. adjusted.

In this way, in the charging device of the third embodiment, like the first embodiment or the second embodiment, even if the charging stop switch fails and cannot be turned off, the charging voltage can be made lower than the battery voltage, and the rechargeable battery 20 will not be charged. being charged, it is possible to prevent overcharging.

Next, a fourth embodiment will be described with reference to FIG. 6 . 6 is a schematic circuit diagram showing a constant voltage circuit unit 2C of a charging device according to a fourth embodiment. In the constant voltage circuit section 2C of the fourth embodiment, the first resistor section R1, the third resistor section R3, and the fourth resistor section R4 are composed of single fixed resistors R1, R3, and R4, respectively, and only the second resistor section R2 is used as a resistor. The value can be configured by switching the resistance part.

As shown in FIG. 6 , the second resistor unit R2 of the fourth embodiment is configured to include a first fixed resistor R2a, a second fixed resistor R2b, and a second switching element S2, and the first fixed resistor R2a and the second fixed resistor R2b are combined. The resistance adjusting unit Raj 1 connected in series with the second switching element S2 is connected in parallel, which is the same as the fourth resistance unit R4 of the first embodiment.

Therefore, in the fourth embodiment, as in the first embodiment, when the second switching element S2 is closed from the open state, the resistance value r2 of the second resistance part R2 is switched so as to decrease from r2a to r2a*r2b/( r2a+r2b). Conversely, when the second switching element S2 is released from the closed state, the resistance value r2 of the second resistor portion R2 increases from r2a*r2b/(r4a+r2b) to r2a. At this time, as described above, since the intermediate voltage Vm of the connection point P1 is controlled to be the same value as the constant value Vb, when the resistance value r2 of the second resistance part R2 increases, the output voltage Vout also decreases, thereby reducing Vm. constant. This fact is also known from formula (1). As described above, even in the fourth embodiment, when the second switching element S2 is opened from the closed state, the resistance value r2 increases, so that the output voltage Vout is switched to decrease as in the third embodiment.

Here, the operation timing of the second switching element S2 in the fourth embodiment is the same as the operation timing described in the third embodiment using FIG. The timing is also disconnected.

As a result, the charging current Icg and the charging voltage Vcg also change in the same manner as in the third embodiment. Even if the charging stop switch fails and cannot be turned off, by making the charging voltage lower than the battery voltage, the rechargeable battery 20 will not be damaged. is 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 a fifth embodiment. The charging device 10A of the first embodiment is the same as the first embodiment, and includes a charging circuit 1A that supplies power to the rechargeable battery 20 , and a first circuit that switches on and off the power supply from the charging circuit 1A to the rechargeable battery 20 . The switching element S1 and the control device 5 that controls the opening and closing of the first switching element S1, the charging circuit 1A includes a constant voltage circuit part 2D, and the constant voltage circuit part 2D applies an output between the two poles of the rechargeable battery 20 during charging. The voltage Vout is maintained at a predetermined charge-time set voltage Vcg. In addition, reference numeral 3 denotes a constant current circuit section.

The constant voltage circuit part 2D includes a first resistance part R1 for dividing the output voltage Vout, a second resistance part R2 connected in series to the low-voltage side of the first resistance part R1, and a connection between the first resistance part R1 and the first resistance part R1. The comparator 4 compares the intermediate voltage Vm, which is the voltage at the connection point P1 between the second resistance parts R2, with a predetermined reference voltage Vb. Then, the constant voltage circuit unit 2D performs feedback control so that the intermediate voltage Vm and the reference voltage Vb become the same, thereby controlling the output voltage Vout to be constant.

Therefore, also in the fifth embodiment, the following formula (2) holds true in a balanced state.

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

In the formula (1), r1 and r2 represent the values of the resistances of the first resistance part R1 and the second resistance part R2 (combined resistances when composed of a plurality of fixed resistances), respectively.

Here, the first resistor part R1 is composed of a single fixed resistor R1, and the second resistor part R2 includes a first fixed resistor R2a, a second fixed resistor R2b, and a second switching element S2, and is configured as a resistance value switchable resistor part. The resistance value switchable resistance unit is obtained by connecting in parallel a first fixed resistance R2a and a resistance adjustment unit Raj 1 obtained by connecting a second fixed resistance R2b and the second switching element S2 in series. Here, let the resistance values of the first fixed resistor R2a and the second fixed resistor R2b be r2a, r2b.

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

Furthermore, in the fifth embodiment, the operation timing of the second switching element S2 is also the same as that of the fourth embodiment. As shown in FIG. The timing of opening is also disconnected (S1 and S2 are in phase). With such a configuration, in the charging device 10A of the fifth embodiment, even if the charging stop switch fails to be turned on, the rechargeable battery 20 is not charged, and overcharging can be prevented.

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

In this embodiment, the second resistance part R2 is composed of a single fixed resistance R2, and the first resistance part R1 includes a first fixed resistance R1a, a second fixed resistance R1b and a second switching element S2, and is used as a resistance value switchable resistance part. In this configuration, the resistance value switchable resistor unit is obtained by connecting in series the first fixed resistor R1a and the resistance adjustment unit Raj2 obtained by connecting the second fixed resistor R1b and the second switching element S2 in parallel. Here, let the resistance values of the first fixed resistor R1a and the second fixed resistor R1b be r1a, r1b.

The resistance value r1 of the first resistance unit R1 configured in this way is switched from the resistance value r1a+r2b at the time of opening when the second switching element S2 is closed as described above for the third resistance unit of the third embodiment. For lowering to r1a. As a result, in the constant voltage circuit section 2E, since the intermediate voltage Vm is controlled to be equal to the reference voltage Vb, as long as the second switching element S2 is closed, Vout is switched to decrease as described in the second embodiment.

As a result, in the sixth embodiment, as shown in FIG. 2 , by synchronizing the operation timing of the second switching element S2 with the opening and closing of the first switching element S1, the second switch is turned on when the first switching element S1 is turned on. The element S2 is closed, and the second switching element S2 is opened when the first switching element S1 is closed, so that the charging voltage Vcg and the charging current Icg can be changed as shown in FIG. 2 . Therefore, according to the sixth embodiment, even if the charging stop switch fails to be turned on, the rechargeable battery 20 is not charged, and overcharging can be prevented.

As mentioned above, six representative embodiments have been shown and described, and various embodiments other than these are also conceivable. However, any of the embodiments is characterized in that by opening or closing the second switching element S2 in synchronization with the opening and closing of the first switching element S1, the output voltage Vout is lowered from Vcg when charging to Vcg when charging is stopped. Vnc.

In order to achieve this purpose, various means can be considered, but as an example, these means can be classified and organized as follows.

As the first type of mode, the first resistance part R1 or the fourth resistance part R4 is constituted by a resistance value switchable resistance part, and the first switching element S1 is switched from closed (ON: connected) to released (OFF: disconnected). ) to reduce these resistance values.

As the second type of mode, the second resistance part R2 or the third resistance part R3 is formed by a resistance value switchable resistance part, and the first switching element S1 is switched from closed (ON: connected) to released (OFF: disconnected). ) to increase these resistance values.

The first type of method can also be classified into the following method: the first fixed resistors R1a, R4a are connected in series with the second fixed resistors R1b, R4b and the second switching element S2. Connecting in parallel to form a resistance value switchable resistance part, and as shown in FIG. 2 , making the second switching element S2 and the first switching element S1 act anti-phase synchronously; and

The first fixed resistors R1a, R4a are connected in series with the resistance adjustment part Raj2 obtained by connecting the second fixed resistors R1b, R4b and the second switching element S2 in parallel to form a resistance value switchable resistor part, and as shown in FIG. Shown is a method of synchronizing the actions of the second switching element S2 and the first switching element S1 in phase.

The methods of the second category can also be classified into the following methods:

The first fixed resistors R2a, R3a are connected in parallel to the resistance adjustment part Raj 1 obtained by connecting the second fixed resistors R2b, R3b and the second switching element S2 in series to form a resistance value switchable resistor part, and as shown in FIG. 2 As shown, the way of synchronizing the actions of the second switching element S2 and the first switching element S1 in phase; and

The first fixed resistors R2a, R3a are connected in series with the resistance adjusting part Raj2 obtained by connecting the second fixed resistors R2b, R3b and the second switching element S2 in parallel to form a resistance value switchable resistor part, and as shown in FIG. 5 Shown is a way to synchronize the operations of the second switching element S2 and the first switching element S1 in anti-phase.

In addition, in the first to sixth embodiments, only one of the plurality of resistance parts of the constant voltage circuit part is configured as a resistance value switchable resistance part, but it is also possible to configure all of the plurality of resistance parts as a resistance value switchable resistance part. Resistor section.

Label description

1. 1A charging circuit

2, 2A, 2B, 2C, 2D, 2E constant voltage circuit part

3Constant current circuit part

4 comparators

5 control device

10. 10A charging device

20 rechargeable batteries

S1 first switching element

S2 is the second switching element.

Claims (8)

1. A charging device for a rechargeable battery, comprising: a charging circuit, the charging circuit supplies power to the rechargeable battery; a first switching element that switches to turn off and on the power supply from the charging circuit to the rechargeable battery; and a control device that controls the opening and closing of the first switching element, The charging circuit has a constant voltage circuit section that maintains an output voltage applied between both electrodes of the rechargeable battery at a predetermined charging-time set voltage during charging, The constant voltage circuit unit is configured to include: a first resistance part for dividing the output voltage, and a second resistance part connected in series with a low-voltage side of the first resistance part; a third resistance part for dividing a voltage maintained constant, and a fourth resistance part connected in series to a low-voltage side of the third resistance part; and a comparator pair defined as an intermediate voltage of a voltage at a connection point between said first resistive portion and said second resistive portion, and defined as an intermediate voltage between said third resistive portion and said fourth resistive portion The voltage at the connection point between the resistive parts is compared with the reference voltage, and the difference between the intermediate voltage obtained by comparison with the comparator and the reference voltage becomes zero through feedback control, thereby maintaining the output voltage at the set voltage during charging, At least one of the first to fourth resistor parts is configured as a resistance value switchable resistor part, and the resistance value switchable resistor part includes at least two fixed resistors including a first fixed resistor and a second fixed resistor. and a second switching element, and the resistance value can be switched by turning the second switching element on and off, The control device is configured to open or close the second switching element synchronously with a signal to open the first switching element to switch the resistance value of the resistance value switchable resistor portion, thereby maintaining the output voltage. The set voltage at the time of charging is lower than the set voltage at the time of charging. 2. The charging device according to claim 1, characterized in that, The resistance switchable resistance unit is configured by connecting the first fixed resistance in parallel to a resistance adjustment unit obtained by connecting the second fixed resistance and the second switching element in series, In the case where the first resistance part is a switchable resistance part, or in the case where the fourth resistance part is a switchable resistance part, the second switching element is configured to be kept open during charging. state, and is closed synchronously with the signal that opens the first switching element, In the case where the second resistance portion is a resistance value switchable resistance portion, or in the case where the third resistance portion is a resistance value switchable resistance portion, the second switching element is configured to be kept closed during charging. state, and is turned on synchronously with the signal that turns on the first switching element. 3. The charging device according to claim 1, characterized in that, The resistance switchable resistance unit is configured by connecting the first fixed resistance in series to a resistance adjustment unit obtained by connecting the second fixed resistance and the second switching element in parallel, In the case where the first resistance part is a resistance value switchable resistance part, or in the case where the fourth resistance part is a resistance value switchable resistance part, the second switching element is configured to be kept open during charging. state, and is closed synchronously with the signal that opens the first switching element, In the case where the second resistance portion is a resistance value switchable resistance portion, or in the case where the third resistance portion is a resistance value switchable resistance portion, the second switching element is configured to be kept closed during charging. state, and is turned on synchronously with the signal that turns on the first switching element. 4. A charging device for a rechargeable battery, comprising: a charging circuit, the charging circuit supplies power to the rechargeable battery; a first switching element that switches to turn off and on the power supply from the charging circuit to the rechargeable battery; and a control device that controls the opening and closing of the first switching element, The charging circuit has a constant voltage circuit section that maintains an output voltage applied between both electrodes of the rechargeable battery at a predetermined charging-time set voltage during charging, The constant voltage circuit unit is configured to include: a first resistance part that divides the output voltage and a second resistance part connected in series to a low voltage side of the first resistance part; and a comparator that compares an intermediate voltage defined as a voltage at a connection point between said first resistance portion and said second resistance portion with a prescribed reference voltage, and the difference between the intermediate voltage obtained by comparison with the comparator and the reference voltage becomes zero through feedback control, thereby maintaining the output voltage at a set voltage during charging, At least one of the first resistor part and the second resistor part is configured as a resistance value switchable resistor part, and the resistance value switchable resistor part includes at least two fixed resistors including a first fixed resistor and a second fixed resistor. and a second switching element, and the resistance value can be switched by turning the second switching element on and off, The control device is configured to open or close the second switching element synchronously with a signal to open the first switching element to switch the resistance value of the resistance value switchable resistor portion, thereby maintaining the output voltage. The set voltage at the time of charging is lower than the set voltage at the time of charging. 5. The charging device according to claim 4, characterized in that, The resistance switchable resistance unit is configured by connecting the first fixed resistance in parallel to a resistance adjustment unit obtained by connecting the second fixed resistance and the second switching element in series, In the case where the first resistance part is a resistance value switchable resistance part, the second switching element is configured to maintain an open state during charging and to be closed in synchronization with a signal that opens the first switching element, In the case where the second resistor is a resistance switchable resistor, the second switching element is configured to maintain a closed state during charging and to be opened in synchronization with a signal that opens the first switching element. 6. The charging device according to claim 4, characterized in that, The resistance switchable resistance unit is configured by connecting the first fixed resistance in series to a resistance adjustment unit obtained by connecting the second fixed resistance and the second switching element in parallel, In the case where the first resistance part is a resistance value switchable resistance part, the second switching element is configured to maintain an open state during charging and to be closed in synchronization with a signal that opens the first switching element, In the case where the second resistor is a resistance switchable resistor, the second switching element is configured to maintain a closed state during charging and to be opened in synchronization with a signal that opens the first switching element. 7. The charging device according to any one of claims 1 to 6, characterized in that, The charging circuit includes a constant current circuit section. 8. The charging device according to any one of claims 1 to 6, characterized in that, The charging stop setting voltage is equal to or lower than an overdischarged battery voltage of the rechargeable battery.