JP2005278334A - Uninterruptible power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an uninterruptible power supply in which deterioration in lifetime of a lithium ion secondary battery due to overcharge is prevented over the entire use period. <P>SOLUTION: At the time of starting use of a lithium ion secondary battery 22, charging voltage is set at a relatively low level. The charging voltage increases as the lithium ion secondary battery 22 approaches the end of lifetime. Since a charge control means 37 sets the charging voltage of the lithium ion secondary battery variably such that the discharge time slightly exceeds the request backup time over the entire use period of the lithium ion secondary battery 22, deterioration in lifetime of the lithium ion secondary battery 22 due to overcharge is prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an uninterruptible power supply provided with a chargeable / dischargeable lithium ion secondary battery as a backup power supply for a power supply body incorporating a main power supply unit.

In general, this type of uninterruptible power supply supplies a required DC or AC voltage to a load from a main power supply unit of a power supply body when an input voltage from a commercial AC power supply is normally generated. While the secondary battery is charged through the power supply unit, when the input voltage is significantly reduced or a power failure occurs, the secondary battery as a backup power supply is discharged and power is continuously supplied from the main power supply unit to the load. ing. Secondary batteries used here are mainly lead storage batteries that are cheap and easy to charge and discharge, but lead storage batteries have to secure a lot of battery storage space. The weight is extremely heavy, and there are various problems due to the use of lead in terms of environment. In order to eliminate such drawbacks, for example, Patent Document 1 proposes an uninterruptible power supply apparatus using a lithium ion secondary battery as a backup power supply instead of a lead storage battery. The lithium ion secondary battery here is composed of a battery module in which a plurality of battery cells are connected in series, and a battery protection circuit for preventing overcharge and overdischarge is also incorporated.
JP 2002-58170 A

  In the uninterruptible power supply of the above-mentioned prior art, the backup time that can continue to supply power to the load at the time of the input voltage drop or power outage depends on the discharge capacity of the secondary battery, but this discharge capacity is It gradually decreases as the secondary battery is used for a long time. FIG. 6 shows the characteristics of the charging voltage V1 and the discharge capacity P1 during the use period of the secondary battery. Conventionally, the discharge capacity at the end of the life of the secondary battery is predicted and required at the end of the life. The charging voltage V1 supplied from the main power supply unit to the secondary battery is set so as to maintain the discharge capacity P1 that is longer than the backup time (requested backup time).

  However, since the charging voltage V1 is set to a fixed value in the main power supply unit regardless of the usage time of the secondary battery, the discharge capacity of the secondary battery with respect to the required backup time at the initial use of the secondary battery. Charging is performed in a state where P1 has a sufficient margin (see “oversetting” shown in FIG. 6). In other words, the charging voltage V1 to the secondary battery is set to be high in advance in anticipation of deterioration due to the time change of the secondary battery, so in the case of a lithium ion secondary battery whose life is significantly reduced particularly when excessive charging is performed. There is a problem that the life of the secondary battery and thus the uninterruptible power supply is significantly reduced.

  The present invention has been made paying attention to the above problems, and provides an uninterruptible power supply device capable of preventing the deterioration of the life of a lithium ion secondary battery due to excessive charging over the entire period of use. Is the purpose.

  In the uninterruptible power supply that charges the lithium ion secondary battery when the input voltage is normal and supplies the power to the load by discharging the lithium ion secondary battery when the input voltage is reduced or the power failure occurs. It comprises time measuring means for counting the elapsed time from the start of use, and charge control means for increasing the charging voltage to the lithium ion secondary battery as the elapsed time advances.

  In this case, the charging voltage is set to be relatively low at the start of use of the lithium ion secondary battery, but the charging voltage becomes higher as the lithium ion secondary battery approaches the end of its life. In other words, the charging control means variably sets the charging voltage of the lithium ion secondary battery so that the discharge time is slightly over the required backup time of the device over the entire period of use of the lithium ion secondary battery. It becomes possible to prevent life deterioration of the lithium ion secondary battery due to excessive charging.

  ADVANTAGE OF THE INVENTION According to this invention, the uninterruptible power supply device which can prevent the lifetime deterioration of the lithium ion secondary battery by excessive charge over the whole period to use can be provided.

  Hereinafter, preferred embodiments of the uninterruptible power supply according to the present invention will be described with reference to the accompanying drawings.

  In FIG. 1 showing a schematic configuration of the entire apparatus, reference numeral 1 denotes a power supply circuit as a main power supply unit to which an AC input voltage Vi from a commercial power supply 51 (see FIG. 4) is applied. One or a plurality of loads 3 to which the output voltage Vo is applied are connected. Reference numeral 21 denotes a secondary battery pack attached to the apparatus as a backup power source. Here, in addition to the lithium ion secondary battery 22 as a secondary battery, preferably the lithium ion secondary battery 22 is prevented from being overdischarged. Both an overdischarge protection circuit 23 and an overcharge protection circuit 24 for preventing overcharge are incorporated. The power supply circuit 1 includes a charging circuit 5 for charging the lithium ion secondary battery 22 when the input voltage Vi is normal, and discharging the lithium ion secondary battery 22 to supply power to the load 3 when the input voltage Vi decreases or when a power failure occurs. Each of the discharge circuits 6 to be supplied is incorporated.

  The power supply circuit 1 includes an AC / AC converter 11 that converts the AC input voltage Vi into a required AC output voltage Vo to the load 3, and AC / DC conversion that converts the AC input voltage Vi into a DC voltage that is stepped up or down. A DC / DC converter 13 for converting the DC voltage obtained by the unit 12 and the DC voltage obtained by the AC / DC converter 12 into a required DC output voltage Vo to the load 3 is appropriately incorporated.

  31 is a novel voltage exchange unit in the present invention, and this voltage exchange unit 31 is connected between the lithium ion secondary battery 22 and the power supply circuit 1 which is a main power supply unit. Here, it is noted that the internal functions of the power supply circuit 1 are not changed by any function built in the voltage conversion unit 31 regardless of what secondary battery pack 21 is attached to the apparatus. The

  The voltage conversion unit 31 is provided as an independent module that is separate from the power supply circuit 1 and the secondary battery pack 21. In the example shown in FIG. 1, the voltage conversion unit 31 is incorporated together in a main body case 7 as a main body power source that accommodates the power supply circuit 1. For example, as shown in FIG. The voltage conversion unit 31 may be incorporated in the secondary battery pack 21 having the shape. In any case, a space for accommodating the voltage conversion unit 31 is provided in the main body case 7 and the secondary battery pack 21. Further, when such a space cannot be secured, as shown in FIG. 3, the voltage conversion unit 31 can be connected independently between the main body case 7 and the secondary battery pack 21 using, for example, an external connector. Is preferred. Further, in the examples shown in FIGS. 1 to 3, the secondary battery pack 21 is separately provided outside the main body case 7, but the secondary battery pack 21 can be accommodated inside the main body case 7. You may comprise. Also in this case, the voltage conversion unit 31 may be provided inside the main body case 7 or the secondary battery pack 21, otherwise, the main body case is separated from the main body case 7 with the built-in secondary battery pack 21. 7 may be provided outside the voltage conversion unit 31. Thus, the voltage conversion unit 31 in the present embodiment can adopt an optimal arrangement according to the dimensions and the like of the main body case 7 and the secondary battery pack 21.

  As shown in FIGS. 1 to 3, the voltage conversion unit 31 in the present embodiment is optimal for charging the lithium ion secondary battery 22 with a power supply voltage applied from the power supply circuit 1 to the lithium ion secondary battery 22. Step-up / step-down unit 32 that steps up or down to an appropriate voltage (optimum charging voltage), a discharge circuit 33 that discharges the lithium ion secondary battery 22 when the input voltage Vi drops or a power failure occurs, and the lithium ion secondary battery 22 is fully charged Is detected, the full-charge detection unit 34 that stops the power supply to the lithium ion secondary battery 22 and self-discharges the lithium ion secondary battery 22, and the terminal voltage of the lithium ion secondary battery 22 reaches the required value. When detecting the decrease, the low voltage detection unit 35 for starting the power supply to the lithium ion secondary battery 22, the time measuring means 36 for counting the elapsed time from the start of use of the lithium ion secondary battery 22, With the lapse time counted by the clock means 36 advances the comprises respectively a charging control means 37 to increase the charge (feed) voltage to the lithium ion secondary battery 22. The configuration of each part will be described in detail below.

  FIG. 4 shows the configuration of the uninterruptible power supply in more detail. In the figure, reference numeral 51 denotes a commercial power source as a supply source of the AC input voltage Vi connected to the input terminals 52 and 52 of the power supply circuit 1, and this input voltage Vi is generated by a filter 53 including a rectifier bridge and a boost chopper circuit. The PFC (power factor correction) circuit 54 is converted to a boosted DC voltage VDC1. That is, the filter 53 and the PFC circuit 54 here correspond to the aforementioned AC / DC converter 12. A DC / DC converter 55 converts the DC voltage VDC1 into one or more DC output voltages Vo1 and Vo2 suitable for the load 3, which corresponds to the DC / DC converter 13. These DC output voltages Vo1 and Vo2 are supplied to the load 3 from an output terminal (not shown) provided in the main body case 7. Note that the number of the DC / DC converter 55 and the DC output voltages Vo1 and Vo2 that can be extracted from the DC / DC converter 55 are not limited to those in the embodiment.

  The DC / DC converter 55 outputs a power supply voltage VCHG for charging the lithium ion secondary battery 22 in addition to the DC output voltages Vo1 and Vo2. On the other hand, a battery converter 56 is connected so as to bypass the DC / DC converter 55 that outputs the power supply voltage VCHG. This is a power supply voltage from the lithium ion secondary battery 22 when the input voltage Vi decreases or when a power failure occurs. Is boosted and the DC voltage VDC2 is supplied to the input side of each DC / DC converter 55. As described above, the power supply circuit 1 shown here functions as an AC / DC unit that converts the AC input voltage Vi into the DC output voltages Vo1 and Vo2, but as an AC / AC unit that supplies an AC output voltage to the load 3. It may be one having the function.

  The secondary battery pack 21 is equipped with a lithium ion secondary battery 22 composed of a plurality of battery cells, detects a voltage generated between the battery cells, and the lithium ion secondary battery 22 A battery protection circuit 61 for monitoring whether or not an overcharged state is reached is incorporated. That is, the battery protection circuit 61 corresponds to the overdischarge protection circuit 23 and the overcharge protection circuit 24. In addition, both ends of the lithium ion secondary battery 22 are connected to the battery connection terminals 62 and 62 of the voltage conversion unit 31, but in the voltage line from the lithium ion secondary battery 22 to the battery connection terminals 62 and 62, When the overcharge protection circuit 24 detects overcharge of the lithium ion secondary battery 22 when the overcharge protection circuit 24 detects overcharge of the lithium ion secondary battery 22 from the voltage conversion unit 31, the lithium ion secondary battery 22 is disconnected from the voltage conversion unit 31 at the time of overcurrent. When the first switch element 65 having a diode 64 connected to both ends of the first switch element 65 and the overdischarge protection circuit 23 detects overdischarge of the lithium ion secondary battery 22, the lithium ion secondary battery is detected. A second switch element 67 having a diode 66 connected to both ends thereof is connected to each other while preventing current supply from 22 to the voltage conversion unit 31.

  In addition to the battery connection terminals 62 and 62 for connecting the secondary battery pack 21, the voltage conversion unit 31 is connected to a voltage supply line for generating a power supply voltage VCHG of the power supply circuit 1 as a terminal exposed to the outside. In addition to the terminals 71 and 71 and the load 3 to which the DC output voltages Vo1 and Vo2 are applied, a discharge terminal 72 to which an arbitrary load 3A is directly connected is provided. The step-up / step-down unit 32 has a function as a charging circuit for charging the lithium ion secondary battery 22 and is DC / DC in accordance with the specifications of the secondary battery in the secondary battery pack 21 incorporated as a backup power source. The power supply voltage VCHG from the converter 55 is designed and adjusted so as to step up or step down. Specifically, when it is known in advance that the optimum charging voltage of the secondary battery is lower than the power supply voltage VCHG from the DC / DC converter 55, a step-down chopper power supply (step-down chopper power supply (step down) that reduces the power supply voltage VCHG to the optimum charging voltage. In contrast, when it is known in advance that the optimum charging voltage of the secondary battery is higher than the feeding voltage VCHG from the DC / DC converter 55, the feeding voltage VCHG is boosted to the optimum charging voltage. A step-up chopper power supply (step-up unit) is incorporated.

  In addition, an input given to the voltage conversion unit 31 to set / adjust the voltage given to the secondary battery in the secondary battery pack 21 from the boost / buck unit 32 to the optimum charging voltage of the lithium ion secondary battery 22 A means for detecting the voltage (feed voltage VCHG) may be provided, or a means for detecting the terminal voltage of the secondary battery with respect to a predetermined input voltage may be provided. Further, the voltage conversion unit 31 may be provided with battery discrimination means for physically discriminating the type of the secondary battery, and either the step-down unit or the step-up unit may be operated according to the secondary battery to be used. . In this way, the optimum voltage can be supplied from the voltage conversion unit 31 to the secondary battery pack 21 for any secondary battery.

  The full charge detection unit 34 is connected to both ends of a resistor 74 that detects a charging current supplied from the boost / buck unit 32 to the lithium ion secondary battery 22. The resistor 74 as the current detection element may be composed of other elements. The full charge detection unit 34 here is based on the charging current to the lithium ion secondary battery 22 detected by the resistor 74, and when the lithium ion secondary battery 22 is fully charged, A charge stop signal for stopping the operation is output to the step-up / step-down unit 32. Further, when the low voltage detection unit 35 detects a low voltage state in which the terminal voltage of the lithium ion secondary battery 22 has decreased to a required value due to self-discharge, the low voltage detection unit 35 outputs a charge start signal for starting the operation of the step-up / step-down unit 32. -It outputs to the step-down unit 32. The full charge detection level by the full charge detection unit 34 is configured to be easily variably set according to the specifications of the secondary battery to be used and the power supply circuit 1.

  The discharge circuit 33 bypasses the series circuit composed of the step-up / step-down unit 32 and the resistor 74, and from one battery connection terminal 62, which is the output terminal of the voltage conversion unit 31, to one input terminal of the voltage conversion unit 31. A discharge line 76 is connected to the main body power connection terminal 71 via a diode 75. The diode 75 has a function of preventing the power supply voltage VCHG from the power supply circuit 1 from being directly supplied to the secondary battery pack 21 without passing through the boost / buck unit 32. Preferably, a changeover switch 77 is provided in the middle of the discharge line 76 as switching means for supplying the terminal voltage of the lithium ion secondary battery 22 to either the main body power connection terminal 71 or the discharge terminal 72. Thereby, according to the product (load) to be used, it can be selected whether the electric power supply from the lithium ion secondary battery 22 is via the power supply circuit 1 or not.

  Note that when the power supply voltage VCHG is lower than the optimum charging voltage of the secondary battery and the boost / buck unit 32 performs boosting, the diode 75 from the secondary battery even when the AC input voltage Vi is normally supplied. The current flows into the main body power connection terminal 71 via the, and the mode is not shifted to the mode for charging the secondary battery. Therefore, in this case, it is desirable to connect the cathode of the diode 75 directly to the discharge terminal 72 and separate the charging line and the discharging line separately.

  Further, the voltage conversion unit 31 here includes a time measuring means 36 and a charge control means 37. The time measuring means 36 starts counting the elapsed time with the start of use of the lithium ion secondary battery 22, but in order to recognize the start of use of the lithium ion secondary battery 22, for example, the secondary battery pack 21 is mechanically operated. May be provided with a detecting means for detecting that the battery is mounted on the voltage exchange unit 31, or a switch means capable of manual operation. Electrically, the resistor 74 may be used so that the time counting means 36 counts the elapsed time while a charging current flows through the resistor 74. In any case, it is preferable to provide a reset means that can reset the count of elapsed time when the secondary battery pack 21 is replaced. By so doing, it is possible to continue supplying a suitable charging voltage to the secondary battery pack 21 even after the secondary battery pack 21 has been replaced.

  Further, the charge control means 37 is a boost chopper circuit for setting and adjusting a charge voltage to be optimally applied to the lithium ion secondary battery 22 based on the elapsed time of the lithium ion secondary battery 22 counted by the time measuring means 36. Alternatively, the voltage is output to the step-up / step-down unit 32 including a step-down chopper circuit.

  Next, the operation of the above configuration will be described. When the AC input voltage Vi from the commercial power supply 51 is normally supplied into the power supply circuit 1, the AC input voltage Vi is converted by the filter 53 and the PFC circuit 54. It is converted into a boosted DC voltage VDC1. The DC voltage VDC1 from the PFC circuit 54 is applied to the DC / DC converter 55, and the DC output voltages Vo1 and Vo2 obtained by the DC / DC converter 55 are applied to the load 3 connected to the main body case 7. A power supply voltage VCHG for charging the lithium ion secondary battery 22 is generated from the DC / DC converter 55. The DC output voltages Vo1 and Vo2 and the feeding voltage VCHG are stabilized by a feedback circuit (not shown) built in the DC / DC converter 55.

  On the other hand, when it is desired to supply power to the load 3 for a certain period of time even when the AC input voltage Vi drops or a power failure occurs, the secondary battery pack 21 shown in FIGS. The power supply circuit 1 here is designed with specifications suitable for charging and discharging the lead storage battery 4 in the conventional example. Specifically, the power supply voltage VCHG output from the DC / DC converter 55 is set to 27 VDC which is the optimum charging voltage for the lead storage battery, and when the AC input voltage Vi is applied to the input terminals 52 and 52. The power supply voltage VCHG is always output from the DC / DC converter 55. Therefore, when the lead storage battery 4 having an optimum charging voltage of 27V DC is used, both ends of the lead storage battery 4 may be directly connected to the voltage line of the power supply voltage VCHG of the power supply circuit 1 without using the voltage exchange unit 31.

  On the other hand, when the lithium ion secondary battery 22 which is a secondary battery other than the lead storage battery 4 is used in consideration of environmental factors, the optimum charging voltage of the lithium ion secondary battery 22 is approximately DC 24.6. Since it is V, when directly connected to the power supply circuit 1, the DC 27V feeding voltage VCHG is always supplied to the lithium ion secondary battery 22, and the life of the lithium ion secondary battery 22 is significantly reduced. Therefore, when using a secondary battery with different specifications, a voltage conversion unit 31 designed according to the specification of the secondary battery is interposed between the power supply circuit 1 and the lithium ion secondary battery 22. Then, the power supply voltage VCHG from the DC / DC converter 55 is DC 24.6V which is the optimum charging voltage of the lithium ion secondary battery 22 by the step-up / step-down unit (in this case, only the step-down function is required) 32. The reduced DC voltage is supplied to the lithium ion secondary battery 22. Therefore, the lithium ion secondary battery 22 can be charged with an optimum voltage by simply incorporating the voltage conversion unit 31 corresponding to the secondary battery pack 21 without modifying the power supply circuit 1.

  Further, the full charge detection unit 34 provided in the voltage conversion unit 31 monitors whether or not the lithium ion secondary battery 22 is in a fully charged state by reducing the charging current flowing through the resistor 74. When the fully charged state of the ion secondary battery 22 is detected, a charge stop signal for stopping the operation is output to the step-up / step-down unit 32 including the step-down chopper circuit. As described above, when the lithium ion secondary battery 22 is fully charged, the power supply from the step-up / step-down unit 32 to the lithium ion secondary battery 22 is stopped, so the lithium ion secondary battery 22 is excessively charged. Can be prevented. In this case, the terminal voltage of the lithium ion secondary battery 22 gradually decreases due to self-discharge, but when the terminal voltage decreases to a required value corresponding to the backup guarantee time of the load 3, the voltage conversion unit 31 is now turned on. The low voltage detection unit 35 provided in the inside outputs a charge start signal that causes the boost / buck unit 32 to start its operation. Therefore, even when the AC input voltage Vi drops or a power failure occurs during the self-discharge of the lithium ion secondary battery 22, it is possible to continue supplying power to the load 3 for a length longer than the backup guarantee time.

  When a lead storage battery having an optimum charging voltage other than DC 27 V is used as the secondary battery, a voltage conversion unit 31 with a different specification that does not incorporate the full charge detection unit 34 or the low voltage detection unit 35 may be attached. That is, it is preferable that a plurality of types of voltage conversion units 31 are prepared according to the specifications of the secondary battery to be used (optimum charging voltage, self-discharge characteristics, etc.).

  When the AC input voltage Vi decreases or a power failure occurs in the state where the voltage conversion unit 31 is incorporated, the power supply voltage VCHG applied from the DC / DC converter 55 to the main body power connection terminal 71 of the voltage conversion unit 31 also decreases. At this time, if the cathode of the diode 75 is connected to the main body power connection terminal 71 by the changeover switch 77, the diode 75 becomes conductive and power is supplied from the lithium ion secondary battery 22 to the battery converter 56 of the power supply circuit 1. . In response to this, the battery converter 56 boosts the power supply voltage from the lithium ion secondary battery 22 to the DC voltage VDC2 at substantially the same level as the DC voltage VDC1 from the PFC circuit 54, and the DC voltage VDC2 is increased to each DC / DC. This is supplied to the input side of the converter 55. Therefore, the load 3 connected to the output side of the DC / DC converter 55 continues to receive power supply from the lithium ion secondary battery 22. If the cathode of the diode 75 is connected to the discharge terminal 72 by the changeover switch 77, power is not supplied to the load 3 connected to the DC / DC converter 55 but to another load 3A connected to the discharge terminal 72. Is supplied. Thus, the combination of the discharge terminal 72 and the changeover switch 77 can selectively supply power from the lithium ion secondary battery 22 to any one of the loads 3 and 3A. However, when the feeding voltage VCHG is lower than the terminal voltage of the lithium ion secondary battery 22, the booster / buck unit 32 has a boosting function, so that the cathode of the diode 75 is directly connected to the discharge terminal 72 as described above. There must be.

  Next, the operation of the time measuring means 36 and the charging control means 37 provided in the power conversion unit 31 will be described with reference to the graph of FIG. In the figure, V1 indicates a charging voltage value from the boost / buck unit 32 to the lithium ion secondary battery 22. The charge control means 37 stores information on the optimum charge voltage that can satisfy the required discharge specification corresponding to the period of use based on the deterioration characteristics of the lithium ion secondary battery 22 over time.

  When the use as an uninterruptible power supply is started, the aging means 36 uses a built-in timer to count the elapsed time from the start of use of the device and the lithium ion secondary battery 22. When a predetermined period of time obtained by the aging means 36 elapses (for example, every several days), the charging control means 37 forcibly increases the charging voltage to the lithium ion secondary battery 22 more than before. The signal is output to the step-up / step-down unit 32. As a result, the charging voltage of the lithium ion secondary battery 22 increases stepwise as the usage time of the apparatus elapses as shown in FIG.

  That is, there is almost no battery deterioration at the start of use of the lithium ion secondary battery 22, and even if the charging voltage to the lithium ion secondary battery 22 is set low, the backup time of the load 3 when the input voltage Vi decreases or during a power failure Can satisfy the required specifications, but battery deterioration occurs as the usage period of the device becomes longer.In this case, the charging voltage to the lithium ion secondary battery 22 is set so that the backup time that satisfies the required specifications can be maintained. Set higher gradually. By performing this every preset time, it becomes possible to regularly maintain the optimum charging voltage according to the backup time, and in particular, the lithium ion secondary battery 22 caused by an excessive charging voltage in the initial stage of use. It is possible to prevent the deterioration of the service life and to exhibit the advantages of using the lithium ion secondary battery 22 as a backup power source for a long period of time.

  As described above, in this embodiment, the lithium ion secondary battery 22 is charged when the input voltage Vi is normal, and the lithium ion secondary battery 22 is discharged to the load 3 when the input voltage Vi decreases or when a power failure occurs. In the uninterruptible power supply for supplying power, the time measuring means 36 for counting the elapsed time from the start of use, and the charging control means for increasing the charging voltage to the lithium ion secondary battery 22 as the elapsed time advances 37.

  In this case, the charging voltage is set to be relatively low at the start of use of the lithium ion secondary battery 22, but the charging voltage becomes higher as the lithium ion secondary battery 22 approaches the end of its life. That is, the charging control means 37 variably sets the charging voltage of the lithium ion secondary battery so that the discharge time slightly exceeds the required backup time of the apparatus over the entire usage period of the lithium ion secondary battery 22. Therefore, it is possible to prevent the life deterioration of the lithium ion secondary battery 22 due to excessive charging.

  In addition, by using the information on the elapsed time counted by the time measuring means 36, for example, a life warning display informing that the lithium ion battery 22 is approaching the end of life, battery display replacement informing battery replacement, and the current backup available time An informing display or the like may be displayed on a display means (not shown). Furthermore, since an excessive charging voltage is not applied to the lithium ion secondary battery 22, the power consumption of the step-up / step-down unit 32 that is a charging circuit of the lithium ion secondary battery 22 can be reduced.

  In addition, the uninterruptible power supply according to the present embodiment includes a lithium ion secondary battery 22 as a replaceable secondary battery and a power supply to the lithium ion secondary battery 22 when the input voltage Vi is normal, while the input voltage An uninterruptible power supply comprising a main body case 7 serving as a main power source provided with a power supply circuit 1 as a main power supply unit that receives power from the lithium ion secondary battery 22 in order to continuously supply power to the load 3 when Vi drops or a power failure occurs In the apparatus, a voltage conversion unit 31 including a booster / buck unit 32 that boosts or steps down the power supply voltage VCHG given to the lithium ion secondary battery 22 from the power supply circuit 1 to the optimum charging voltage of the lithium ion secondary battery 22; The power supply circuit 1 and the lithium ion secondary battery 22 are connected.

  In this case, when a lithium ion secondary battery 22 having different specifications is used as a backup power source, the lithium ion secondary battery 22 is not directly connected to the power supply circuit 1, but is converted into a voltage with a boost / buck unit 32. The power supply circuit 1 is connected through the unit 31. In this way, the voltage conversion unit 31 boosts or lowers the power supply voltage VCHG supplied from the power supply circuit 1 to the lithium ion secondary battery 22 to a voltage suitable for charging the lithium ion secondary battery 22. In this way, the lithium ion secondary battery 22 can be optimally voltaged without any modification in the power supply circuit 1 simply by interposing the voltage conversion unit 31 between the power supply circuit 1 and the lithium ion secondary battery 22. Can be charged with. Therefore, it is possible to provide an uninterruptible power supply device that can use secondary batteries of various specifications as a backup power source without any problems without modifying the existing electronic circuit 1.

  In addition, the voltage conversion unit 31 of the present embodiment includes a full charge detection unit 34 that, when detecting the full charge of the lithium ion secondary battery 22, stops power supply to the lithium ion secondary battery 22 and performs self discharge. Yes.

  In this case, for example, when the voltage exchange unit 31 is incorporated together with a secondary battery such as the lithium ion secondary battery 22, the full charge detection unit 34 provided in the voltage exchange unit 31 detects the full charge of the lithium ion secondary battery 22. When this occurs, power supply to the lithium ion secondary battery 22 is stopped and self-discharge is performed. In this way, the life of the lithium ion secondary battery 22 is extended as much as possible by supplying the minimum necessary power to the secondary battery such as the lithium ion secondary battery 22 that does not need to be constantly powered. It becomes possible.

  Furthermore, the voltage conversion unit 31 of the present embodiment, when detecting that the terminal voltage of the lithium ion secondary battery 22 has decreased to a required value, starts a power supply to the lithium ion secondary battery 22 and a low voltage detection unit 35.

  In this case, when the terminal voltage of the lithium ion secondary battery 22 connected to the voltage exchange unit 31 is reduced to a required value corresponding to the backup time of the load 3 guaranteed as the device, for example, the full charge detection unit 34 fully charges. Until the detection, power is supplied to the lithium ion secondary battery 22. By doing so, the power supply to the load 3 can be continued for a certain period of time when the input voltage Vi decreases or when a power failure occurs, regardless of the state of charge of the lithium ion secondary battery 22.

  In addition, this invention is not limited to the said Example, A various deformation | transformation implementation is possible in the range of the summary of this invention. For example, in the embodiment, the charging voltage for the lithium ion secondary battery is increased stepwise, but the charging voltage may be continuously increased as the elapsed time advances.

It is a block block diagram of the uninterruptible power supply which shows one preferable embodiment in this invention. It is a block block diagram of the uninterruptible power supply device which shows the modification of FIG. 1 same as the above. It is a block block diagram of the uninterruptible power supply which shows the further modification of FIG. 1 same as the above. FIG. 2 is a more detailed block diagram of the uninterruptible power supply. It is a graph which showed the characteristic of the charging voltage during the use period of a secondary battery same as the above. It is the graph which showed each characteristic of the charge voltage and discharge time during the use period of the conventional secondary battery.

Explanation of symbols

3 Load
22 Lithium ion secondary battery
36 Timekeeping
37 Charge control means

Claims (1)

In the uninterruptible power supply that charges the lithium ion secondary battery when the input voltage is normal and supplies the power to the load by discharging the lithium ion secondary battery when the input voltage is reduced or a power failure occurs.
A time counting means for counting the elapsed time from the start of use;
An uninterruptible power supply comprising: charge control means for increasing a charging voltage to the lithium ion secondary battery as the elapsed time advances.

Images