Technical Field
The present invention relates to a power failure backup power supply device, and more particularly, to a power failure backup power supply device to be used for an elevator system.
Background Art
A power failure backup power supply device is disposed in an elevator control apparatus as an emergency power supply configured to operate a car in case of a power failure (see, for example, Patent Literature 1 and Patent Literature 2).
[0003] A lead storage battery (hereinafter referred to simply as "battery") is used for the power failure backup power supply device. The battery is disposed in every elevator control apparatus as standard equipment. Therefore, an inexpensive battery having an optimum capacity is selected.
Further, the battery is also used as a power supply for an emergency light inside a car and a power supply for an intercom in case of a power failure. In case of a power failure, a passenger inside the car can communicate with a building manager or a maintenance office through the intercom.
[0005] The battery can be repeatedly used through charging and discharging by a chemical reaction. Therefore, with duration of

use, an internal resistance continues to increase. As a result, an electric charge of the battery is gradually reduced from an initial electric charge at the start of use of the battery. Therefore, even after a fast charge is performed by a charger in accordance with a discharge amount, a state of charge cannot be recovered to 100%.
[0006] By carrying out a trickle charge for one week or longer after the fast charge, the state of charge of the battery becomes close to 100%. The trickle charge refers to charging at a low rate with a current having a current value equal to or smaller than a current value defined in accordance with specifications of a storage battery. Therefore, with the trickle charge, the charging takes long time. Thus, when a power failure occurs again within one week after the occurrence of the previous power failure, the battery starts discharging with the state of charge being smaller than 100%. In this case, power corresponding to a 100% electric charge of the battery cannot be supplied. In view of the fact described above, in order to satisfy constraints on an evacuation operation in case of a power failure, a larger electric charge than required is to be anticipated as a retained electric charge of the battery. [0007] Further, the discharge performed before the battery reaches a full charge accelerates degradation of pole plates being components inside the battery and therefore affects a lifetime of the battery. Therefore, in Patent Literature 1, when a voltage of the battery becomes equal to or smaller than a threshold value while

the evacuation operation is being performed during the power failure, a speed of the evacuation operation is decreased so that the evacuation operation is continued while preventing a voltage drop of the battery.
[0008] Further, in Patent Literature 2, for a quick full charge of the battery, selection of any one of the trickle charge and the fast charge based on a state of charge of the battery at time of recovery from the power failure is proposed.
Citation List Patent Literature
[0009] [PTL 1] JP 08-169658 A [PTL 2] JP 2011-126617 A
Summary of Invention Technical Problem
[0010] As described above, the discharge performed before the battery reaches the full charge accelerates the degradation of the pole plates being the components inside the battery and therefore also affects the lifetime of the battery. Therefore, in Patent Literature 1, when the voltage of the battery becomes equal to or smaller than the threshold value while the evacuation operation is being performed, the speed of the evacuation operation is decreased so that the evacuation operation is continued while preventing the voltage drop of the battery. Therefore, in Patent

Literature 1, there is a problem in that, in a case where, for example, the power failure frequently occurs, the speed of the evacuation operation is constantly low, which prevents a suitable evacuation operation from being performed in case of a power failure. [0011] Further, in Patent Literature 2, any one of the trickle charge and the fast charge is selected based on the state of charge of the battery at the time of recovery from the power failure so that the battery is quickly fully charged. According to the method described in Patent Literature 2, however, when a subsequent power failure occurs earlier than expected, there is a problem in that the battery may fail to be sufficiently charged in time. Further, when the power failure occurs frequently, the fast charge is always performed after the occurrence of each of the power failures. Thus, there is a problem in that so much strain is placed on the battery as to to reduce the lifetime of the battery.
[0012] The present invention has been made to solve the problems described above, and has an object to provide a power failure backup power supply device capable of suitably driving a target to be driven during a power failure even when a plurality of power failures occur within a short period of time.
Solution to Problem
[0013] According to one embodiment of the present invention, there is provided a power failure backup power supply device, including: a power converter configured to convert AC power supplied

from a commercial power supply into DC power and supply the DC power to a target to be driven; a battery to be charged with the AC power supplied from the commercial power supply, which is configured to discharge power to the target to be driven when the commercial power supply fails; and a charging/discharging control unit configured to control the charging and the discharging of the battery, the charging/discharging control unit including: a charging section configured to charge the battery with the AC power supplied from the commercial power supply; a current measuring section configured to measure a discharge current value during the discharging of the battery; a timer section configured to measure a discharge time period of the battery; and a voltage measuring section configured to measure a voltage of the battery, in which the charging/discharging control unit is configured to obtain a discharge capacity discharged from the battery during the power failure based on the discharge current value measured by the current measuring section and the discharge time period measured by the timer section when the commercial power supply recovers from the power failure, perform a first charge of the battery with a first charge current value by the charging section based on the discharge capacity, and perform a second charge of the battery with a second charge current value smaller than the first charge current value after the first charge, and in which the charging/discharging control unit is configured to interrupt the charging of the battery for a given time period after an end of the first charge or during

the second charge, obtain a capacity shortage of the battery based on the voltage of the battery, which has been measured by the voltage measuring section, after the interrupting, and perform a third charge of the battery with a third charge current value larger than the second charge current value by the charging section based on the capacity shortage.
Advantageous Effects of Invention
[0014] According to one embodiment of the present invention, the power failure backup power supply device performs the second charge with the second charge current value smaller than the first charge current value after the first charge performed with the first charge current value. After the end of the first charge or during the second charge, the charging of the battery is interrupted for the given time period. After the interruption, the capacity shortage of the battery is obtained based on the voltage of the battery, which has been measured by the voltage measuring section. The third charge of the battery is performed based on the capacity shortage by the charging section with the third charge current value larger than the second charge current value. Therefore, time required for the charging can be reduced. At the same time, the battery can be charged to a fully charged state. Accordingly, even when a plurality of power failures occur within a short time period, the target to be driven can be suitably driven.

Brief Description of Drawings
[0015] FIG. 1 is a configuration diagram for illustrating a configuration of a power failure backup power supply device according to a first embodiment of the present invention.
FIG. 2 is a graph for showing a discharge current from a battery during backup and time in the power failure backup power supply device according to the first embodiment of the present invention.
FIG. 3 is a graph for showing a charge current to the battery after power recovery and time in a related-art charging method.
FIGS. 4A and 4B are graphs for showing an electric charge of the battery during charging and time in the related-art charging method.
FIG. 5 is a graph for showing the electric charge of the battery during the charging and time in the power failure backup power supply device according to the first embodiment of the present invention.
FIG. 6 is a graph for showing the charge current to the battery during the charging and time in the power failure backup power supply device according to the first embodiment of the present invention.
FIG. 7 is a graph for showing an example of a lookup table that defines a correspondence relationship between a state of charge of the battery and a voltage, which is to be used in the power failure backup power supply device according to the first embodiment of the present invention.
FIG. 8 is a block diagram for illustrating a hardware configuration of a control section of a charging/discharging

control unit disposed in the power failure backup power supply device according to the first embodiment of the present invention. FIG. 9 is a flowchart for illustrating a flow of processing performed by the power failure backup power supply device according to the first embodiment of the present invention.
Description of Embodiment
[0016] First Embodiment
FIG. 1 is a view for illustrating a configuration of a power failure backup power supply device according to a first embodiment of the present invention.
[0017] As illustrated in FIG. 1, the power failure backup power supply device according to this embodiment includes an electromagnetic contactor contact 2, a converter 3, a smoothing capacitor 4, an inverter 5, a charging/discharging control unit 11, and a battery 12.
[0018] As illustrated in FIG. 1, the power failure backup power supply device is connected to a commercial power supply 1 through intermediation of the electromagnetic contactor contact 2. The commercial power supply 1 is a three-phase AC power supply. The electromagnetic contactor contact 2 is closed while an elevator is running normally.
[0019] The converter 3 is connected to the electromagnetic contactor contact 2. The converter 3 is a power converter having an AC side connected to the electromagnetic contactor contact 2,

which is configured to convert an AC voltage supplied from the commercial power supply 1 into a DC voltage. The smoothing capacitor 4 is connected to a DC side of the converter 3. The smoothing capacitor 4 is configured to smooth an output voltage from the converter 3.
[0020] The inverter 5 is connected to both ends of the smoothing capacitor 4. The inverter 5 is configured to convert the output voltage smoothed by the smoothing capacitor 4 into three-phase AC voltages each having a variable voltage and a variable frequency.
[0021] An electric motor 6 for driving the elevator is connected to an AC side of the inverter 5. The electric motor 6 is constructed of a three-phase induction electric motor. A drive sheave 7 is coupled to the electric motor 6. The three-phase AC voltages output from the inverter 5 are applied to the electric motor 6. The electric motor 6 drives the drive sheave 7 by the three-phase AC voltages. A hoisting rope 8 is looped over the drive sheave 7. A car 9 of the elevator is coupled to one end of the hoisting rope 8. A counterweight 10 is coupled to another end of the hoisting rope 8. The car 9 and the counterweight 10 are suspended by the hoisting rope 8 inside a hoistway. The electric motor 6 drives the drive sheave 7 to raise and lower the car 9 and the counterweight 10 in the hoistway.
[0022] The battery 12 is connected to the DC side of the converter 3 through intermediation of the charging/discharging

control unit 11. The battery 12 is constructed of a lead storage battery. While power is being supplied to the battery 12 from the commercial power supply 1, the battery 12 is charged with the power. Meanwhile, when the commercial power supply 1 fails, the battery 12 supplies power for driving the car 9 to the electric motor 6. [0023] The charging/discharging control unit 11 includes a charging section 13, a current measuring section 14, a control section 15, a voltage measuring section 16, a normally closed contact 17, and a normally open contact 18.
The normally closed contact 17 is closed during a normal operation, specifically, while the power is being supplied from the commercial power supply 1. Meanwhile, when the commercial power supply 1 fails, the normally closed contact 17 is disconnected.
The normally open contact 18 is disconnected during the normal operation, specifically, while the power is being supplied from the commercial power supply 1. Meanwhile, when the commercial power supply 1 fails, the normally open contact 18 is closed.
While the power is being supplied from the commercial power supply 1, the charging section 13 charges the battery 12 with the power through intermediation of the normally closed contact 17.
The current measuring section 14 is configured to measure a discharge current value during discharge of the battery 12.
The control section 15 is configured to control the charging section 13, the normally closed contact 17, and the normally open

contact 18. The control section 15 includes a timer section 15a therein. The timer section 15a is configured to measure a time period of discharge of the battery 12. The timer section 15a is also configured to measure a time period of charging of the battery 12, which is performed by the charging section 13.
The voltage measuring section 16 is configured to measure a voltage of the battery 12.
The battery 12 discharges power for driving the car 9 through intermediation of the normally open contact 18 so as to apply the three-phase AC voltages to the electric motor 6 through intermediation of the smoothing capacitor 4 and the inverter 5 during a power failure of the commercial power supply 1. [0024] The charging/discharging control unit 11 is configured as described above. When the commercial power supply 1 recovers from the power failure, a discharge capacity discharged from the battery 12 during the power failure is obtained based on the discharge current value measured by the current measuring section 14 and the discharge time period measured by the timer section 15a. Then, in order to charge the battery 12 so as to compensate for the discharge capacity, as shown in FIG. 6, a first charge of the battery 12 is performed with a first charge current value. A charging method used in the first charge is a fast charge. After an end of the first charge, the charging/discharging control unit 11 performs a second charge of the battery 12 with a second charge current value smaller than the first charge current value. A

charging method used in the second charge is a trickle charge. In this embodiment, after the end of the first charge or during the second charge, the charging of the battery 12 is interrupted for a given time period, and, after the interruption, a third charge of the battery 12 is performed with a third charge current value larger than the second charge current value, as shown in FIG. 6.
[0025] FIG. 8 is an illustration of a hardware configuration of the control section 15 of the charging/discharging control unit 11. As illustrated in FIG. 8, the control section 15 includes an input device 100 to which a signal is input, a processor 101, a memory 102, and an output device 103 configured to output a signal. The control section 15 is achieved by the processor 101 executing a program stored in the memory 102. Alternatively, a plurality of processors and a plurality of memories may execute the above-mentioned functions in cooperation with each other.
[0026] An operation of the charging/discharging control unit
11 is now described in detail.
[0027] FIG. 2 is a graph for showing a state of the battery
12 during the power failure of the commercial power supply 1. In
FIG. 2, a relationship between the discharge current value of the
battery 12 and time exhibited while the discharge is being performed
during the power failure is shown. In FIG. 2, a horizontal axis
represents time, and a vertical axis represents the discharge
current value.
[0028] As shown in FIG. 2, the battery 12 discharges with a

given discharge current I1 for a discharge time period T1. In this case, the discharge capacity from the battery 12 is obtained by: I1×T1(A•sec).
[0029] FIG. 3 is a graph for showing a state of the battery 12 after the recovery of the commercial power supply 1 from the power failure. In FIG. 3, a relationship between a charge current value of the battery 12 and time exhibited while the battery 12 is being charged is shown. In FIG. 3, a horizontal axis represents time, and a vertical axis represents the charge current value.
[0030] FIG. 3 is a graph to be compared with the charging method in this embodiment shown in FIG. 6. FIG. 3 is a graph for showing a case in which the battery 12 is charged by a general related-art method. In FIG. 3, the battery 12 is charged with a given specified charge current I2 for a specified time period T2. The specified charge current I2 has a value determined from a battery capacity of the battery 12. Specifically, when the battery capacity is C, the specified charge current I2 is generally set to about 0.3×C
(A). The specified charge current I2 is a maximum charge current for the battery 12. When the battery 12 is charged with a current equal to or smaller than the maximum charge current, strain on the battery 12 is small and therefore the battery 12 is unlikely to degrade.
[0031] As described above with reference to FIG. 2, it is supposed that the discharge capacity from the battery 12 during the power failure is I1×T1(A•sec). At this time, by dividing the

discharge capacity (I1×T1) by the specified charge current I2 as expressed in Expression (1), the specified time period T2 required for the amount of charging corresponding to the discharge capacity is obtained.
[0032] T2=(I1×T1)/I2 (1)
[0033] As described above, in FIG. 3, the fast charge is performed with the specified charge current I2 for the specified time period T2. In this case, a charged electric charge of the battery 12 is expressed as: I2×T2=I1×T1(A•sec). Thus, the battery 12 is theoretically in a fully charged state. However, the battery 12 self-discharges, and hence, a state of charge of the battery 12 has a shortage to achieve a full charge. Therefore, the shortage is required to be compensated for by the trickle charge. Thus, as shown in FIG. 3, at the end of the specified time period T2, the charging method is switched from the fast charge to the trickle charge. In the trickle charge, the charging is continued with a trickle charge current It until the battery 12 is fully charged. The trickle charge current It has a value determined from the battery capacity of the battery 12. Specifically, when the battery capacity is represented by C, the trickle charge current It is generally set to about (I/1000)×C(A). The trickle charge generally requires one week or longer to achieve a full charge.
[0034] FIG. 4A is a graph for showing a transition of the state of charge of the battery 12 exhibited while the charging is being performed by the related-art method shown in FIG. 3. FIG. 3 is a

graph for showing an initial state in which the battery 12 has not degraded, while FIG. 4A is a graph for a case in which the battery 12 has degraded. Therefore, for comparison to FIG. 3, FIG. 4B corresponding to FIG. 3 is given.
[0035] In FIGS. 4A and 4B, the battery 12 is charged by the same method as the general charging method described with reference to FIG. 3. Specifically, the battery 12 is charged with the specified charge current I2 for the specified time period T2. Because of the degradation of the battery 12, it is supposed that the battery is charged only at about 80% of the battery capacity C at the end of the specified time period T2, as shown in FIGS. 4A and 4B. In this case, when the charging method is switched from the fast charge to the trickle charge at the end of the specified time period T2, the battery 12 has not been fully charged yet. Therefore, a time period required to achieve the full charge may be one month or longer.
[0036] Therefore, in the power failure backup power supply device according to this embodiment, the battery 12 is charged by the charging method shown in FIG. 5 and FIG. 6.
[0037] FIG. 5 and FIG. 6 are graphs each for showing a case in which the battery 12, which has degraded, is charged by the charging method in this embodiment.
[0038] FIG. 6 is a graph for showing a relationship between a charge current to the battery 12 and time in a case where the battery 12 is being charged after the power recovery of the

commercial power supply 1. In FIG. 6, a horizontal axis represents time, and a vertical axis represents the charge current value. In FIG. 6, as in FIG. 3, the first charge and the second charge are performed for the battery 12. In FIG. 6, however, the charging is interrupted after the end of the first charge or during the second charge, and then the third charge is performed. The charging method shown in FIG. 6 differs from the charging method shown in FIG. 3 in the above-mentioned point.
[0039] FIG. 5 is a graph for showing a transition of the state of charge of the battery 12 in a case where the charging is performed with the charging method shown in FIG. 6. In FIG. 5, a horizontal axis represents time, and a vertical axis represents the state of charge of the battery 12.
[0040] As shown in FIG. 5 and FIG. 6, in this embodiment, in the charging/discharging control unit 11, the control section 15 first instructs the charging section 13 to start charging. As a result, the charging section 13 charges the battery 12 with the power supplied from the commercial power supply 1. At this time, the normally closed contact 17 is closed. The charging performed at this time is referred to as the first charge. In the first charge, the charging section 13 performs the fast charge of the battery 12 with the specified charge current I2 for the specified time period T2. When the battery capacity is represented by C, the specified charge current I2 is set to: 0.3×C (A). The specified time period T2 is obtained from the discharge capacity as expressed in

Expression (1). Further, the control section 15 determines whether the specified time period T2 has elapsed or not based on a result of the time measurement performed by the timer section 15a. The battery 12 is supposed to theoretically achieve the fully charged state as a result of the first charge. In the example shown in FIG. 5 and FIG. 6, however, the battery 12 has degraded. Therefore, it is supposed that the battery 12 has been charged only at about 80% of the battery capacity C at a time t1 corresponding to the end of the specified time period T2 from the start of charging. [0041] In this embodiment, the charging is interrupted for a given time period at the end of the specified time period T2, as shown in FIG. 5 and FIG. 6. The given time period is hereinafter referred to as "capacity measurement time period T3". The capacity measurement time period T3 is a preset given time period, and a time period ranging from 12 hours to 24 hours is an index of the capacity measurement time period T3. In FIG. 5 and FIG. 6, a time period from the time t1 to a time t2 corresponds to the electric charge measurement time period T3. In the capacity measurement time period T3, first, at the time t1, the control section 15 of the charging/discharging control unit 11 opens the normally closed contact 17 to disconnect the charging section 13 and the battery 12 from each other. In this manner, the battery 12 is brought into an open state. The "open state" means that the battery 12 is in a non-charging and non-discharging state. The control section 15 determines whether the capacity measurement time period T3 has

elapsed or not from the time t1 based on a result of time measurement performed by the timer section 15a. When it is determined at the time t2 that the capacity measurement time period T3 has elapsed, the control section 15 acquires an open voltage of the battery 12 from the voltage measuring section 16.
[0042] The control section 15 includes the memory 102 illustrated in FIG. 8. In the memory 102, a lookup table that predefines a correspondence relationship between the open voltage of the battery 12 and the state of charge of the battery 12 is stored. In FIG. 7, an example of the lookup table is shown. In FIG. 7, a horizontal axis represents the state of charge (%) of the battery 12. A vertical axis represents the open voltage (V) of the battery 12. The control section 15 can obtain the state of charge (%) corresponding to the open voltage of the battery 12, which has been acquired from the voltage measuring section 16, in accordance with the lookup table of FIG. 7. The control section 15 calculates a capacity shortage Cshortage of the battery 12 to achieve the full charge from a difference from the state of charge (%) of the battery 12 by Expression (2). In Expression (2), C represents the battery capacity of the battery 12. [0043] Capacity Shortage Cshortage
=C×(100(%)-State of Charge (%)) (2)
[0044] The control section 15 calculates a supplementary
charge time period T4 based on the capacity shortage Cshortage by using
Expression (3). The supplementary charge time period T4 is a time

period required to compensate for the capacity shortage Cshortage by charging. In the example of FIG. 5 and FIG. 6, a time period between the time t2 and a time t3 corresponds to the supplementary charge time period T4. In Expression (3), I2 represents the above-mentioned specified charge current.
[0045] T4=Cshortage/I2 (3)
[0046] In the supplementary charge time period T4, the control section 15 first closes the normally closed contact 17 to connect the charging section 13 and the battery 12 to each other. Next, the control section 15 instructs the charging section 13 to start charging. In response to the instruction, the charging section 13 uses the power supplied from the commercial power supply 1 to charge the battery 12. Specifically, the charging section 13 performs the fast charge of the battery 12 with the specified charge current I2 for the supplementary charge time period T4. The charging is referred to as a third charge. As a result of the third charge, the battery 12 reaches the fully charged state at the time t3.
[0047] The control section 15 switches the charging method from the fast charge to the trickle charge at the time t3. In the trickle charge, the charging is continued with the trickle charge current It until the battery 12 is fully charged. The charging is referred to as the second charge. The trickle charge current It is set to (1/1000)×C (A). In the trickle charge, a self-discharge amount of the battery 12 is compensated for.
[0048] FIG. 9 is a flowchart for illustrating a flow of an

operation of the power failure backup power supply device according to this embodiment.
[0049] As illustrated in FIG. 9, in this embodiment, the control section 15 of the charging/discharging control unit 11 determines whether the commercial power supply 1 has recovered from the power failure or not (Step S1).
[0050] When determining that the commercial power supply has recovered, the control unit 15 calculates the discharge capacity discharged from the battery 12 during the power failure based on the discharge current I1 measured by the current measuring section 14 and the discharge time period T1 measured by the timer section 15a (Step S2).
[0051] Next, the control section 15 divides the discharge capacity by the specified charge current I2 to calculate the specified charge time period T2 required to compensate for the discharge capacity by charging. During the specified charge time period T2, the charging section 13 performs the fast charge of the battery 12 with the specified charge current I2 (Step S3). The fast charge is the above-mentioned first charge.
[0052] Next, the control section 15 determines whether the fast charge has been terminated or not (Step S4). Specifically, the control section 15 determines whether the specified charge time period T2 has elapsed or not based on the result of time measurement performed by the timer section 15a. [0053] When determining that the fast charge has been

terminated, the control section 15 opens the normally closed contact 17 to disconnect the charging section 13 and the battery 12 from each other so as to interrupt the charging. In this manner, during the capacity measurement time period T3, the battery 12 is kept in an open state (Step S5).
[0054] The control section 15 determines whether or not the capacity measurement time period T3 has elapsed or not based on the result of time measurement performed by the timer section 15a. When determining that the capacity measurement time period T3 has elapsed, the control section 15 acquires the open voltage of the battery 12 from the voltage measuring section 16 (Step S6).
[0055] Next, the control section 15 obtains the state of charge of the battery 12 based on the value of the open voltage in accordance with the lookup table stored in the memory 102, which is shown in FIG. 7, to calculate the capacity shortage Cshortage required to be compensated for to achieve the full charge (Step S7).
[0056] The control section 15 divides the capacity shortage Cshortage by the specified charge current I2 to calculate the supplementary charge time period T4 required to compensate for the capacity shortage Cshortage by charging. In this manner, the control section 15 closes the normally closed contact 17 again and performs a supplementary charge of the battery 12 with the specified charge current I2 for the supplementary charge time period T4 (Step S8) . The supplementary charge is the above-mentioned third charge.
[0057] The control section 15 determines whether or not the

supplementary charge time period T4 has elapsed or not based on the result of time measurement performed by the timer section 15a. When determining that the supplementary charge time period T4 has elapsed, the control section 15 switches the charging method from the fast charge to the trickle charge so as to perform the trickle charge of the battery 12 with the trickle charge current It (Step S9). The trickle charge is the above-mentioned second charge. [0058] As described above, in this embodiment, the charging is interrupted after the fast charge. After elapse of the given time period, the open voltage of the battery 12 is measured. The capacity shortage of the battery 12 is calculated based on the open voltage. Then, the fast charge is started again to perform the charging to compensate for the capacity shortage. In this manner, even when the battery 12 has degraded, the battery 12 can be charged to be fully charged. Further, the capacity shortage is compensated for not by the trickle charge but by the fast charge. Therefore, time required for the charging can be significantly reduced. Therefore, even when a plurality of power failures occur within a short time period, the state of charge of the battery 12 does not tend to have a shortage. Therefore, a suitable evacuation operation of the elevator in case of a power failure is enabled at any time.
[0059] Although it has been described that the capacity measurement time period T3 and the third charge (supplementary charge time period T4) are provided after elapse of the specified

time period T2 as shown in FIG. 6, timing at which the capacity measurement time period T3 and the third charge (supplementary charge time period T4) are provided is not limited thereto. The capacity measurement time period T3 and the third charge
(supplementary charge time period T4) may be provided in a trickle charge time period T5.
[0060] Further, although it has been described that the first charge current value used in the specified time period T2 and the third charge current value used in the supplementary charge time period T4 are set to the same value, the values of the first charge current value and the third charge current value are not limited thereto. The third charge current value may be set smaller than the first charge current value in accordance with the voltage measured by the voltage measuring section 16.
[0061] When the first charge current value and the third charge current value are set to the same value, the charging section 13 is required to have only two kinds of current values, specifically, the specified charge current I2 and the trickle charge current It. Therefore, a configuration of the charging section 13 can be simplified.
[0062] Meanwhile, when the third charge current value is set smaller than the first charge current value, strain on the battery 12 during the third charge can be reduced. Therefore, a lifetime of the battery 12 can be prolonged.
[0063] Further, the interruption of the charging (capacity

measurement time period T3) and the third charge (supplementary charge time period T4) may be set within an elevator out-of-service period. In the elevator out-of-service period, the evacuation operation in case of a power failure is not required to be performed. Therefore, the interruption of the charging and the third charge can be reliably performed. Further, in an office building or other constructions, the elevator is not expected to be frequently used in late night hours. Therefore, the interruption of the charging and the third charge may be set to be performed in the late night hours.
Industrial Applicability
[0064] The power failure backup power supply device according to the present invention can be used as an evacuation operation device having high reliability even when the power failure frequently occurs depending on power conditions. Further, it is to be understood that the present invention is also applicable to apparatus other than the elevator.
Reference Signs List
[0065] 1 commercial power supply, 2 electromagnetic contactor contact, 3 converter, 4 smoothing capacitor, 5 inverter, 6 electric motor, 7 drive sheave, 8 hoisting rope, 9 car, 10 counterweight, 11 charging/discharging control unit, 12 battery, 13 charging section, 14 current measuring section, 15 control section, 16

voltage measuring section, 17 normally closed contact, 18 normally open contact.

We Claim:
[Claim 1] A power failure backup power supply device, comprising:
a power converter configured to convert AC power supplied from a commercial power supply into DC power and supply the DC power to a target to be driven;
a battery to be charged with the AC power supplied from the commercial power supply, which is configured to discharge power to the target to be driven when the commercial power supply fails; and
a charging/discharging control unit configured to control the charging and the discharging of the battery, the charging/discharging control unit comprising:
a charging section configured to charge the battery with the AC power supplied from the commercial power supply;
a current measuring section configured to measure a discharge current value during the discharging of the battery;
a timer section configured to measure a discharge time period of the battery; and
a voltage measuring section configured to measure a voltage of the battery,
wherein the charging/discharging control unit is configured to obtain a discharge capacity discharged from the battery during the power failure based on the discharge current value measured by the current measuring section and the discharge time period

measured by the timer section when the commercial power supply recovers from the power failure, perform a first charge of the battery with a first charge current value by the charging section based on the discharge capacity, and perform a second charge of the battery with a second charge current value smaller than the first charge current value after the first charge, and
wherein the charging/discharging control unit is configured to interrupt the charging of the battery for a given time period after an end of the first charge or during the second charge, obtain a capacity shortage of the battery based on the voltage of the battery, which has been measured by the voltage measuring section, after the interrupting, and perform a third charge of the battery with a third charge current value larger than the second charge current value by the charging section based on the capacity shortage.
[Claim 2] The power failure backup power supply device according to claim 1, wherein the given time period is set within an out-of-service time period of the target to be driven.
[Claim 3] The power failure backup power supply device according to claim 1 or 2, wherein the third charge current value is the same as the first charge current value.
[Claim 4] The power failure backup power supply device according

to claim 1 or 2, wherein the third charge current value is smaller than the first charge current value.