JP2002058170A - Uninterruptible power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized, lightweight uninterruptible power supply by employing a lithium-ion secondary battery. SOLUTION: A plurality of battery modules 30 formed by series-connecting the cells 31 of a plurality of lithium-ion secondary batteries are series-connected to form a battery power supply 20. The battery modules 30 incorporate a charging circuit 32 for charging the cells 31 in series, a battery protection circuit 33 provided with a function of detecting the voltages of the cells 31 for prevention of overcharging and overdischarging, and a cell balance circuit for detecting the voltages of the cells 31 and discharging the cells 31 whose voltage exceeds a prescribed value through a discharging circuit 37.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uninterruptible power supply provided with a secondary battery.

[0002]

2. Description of the Related Art An uninterruptible power supply is configured to supply power stored in a secondary battery to a load when a power failure occurs in a commercial AC power supply, and a lead storage battery has been conventionally used as the secondary battery. It is used. This is because it is inexpensive and the charge / discharge management is simple.

[0003]

However, in this type of device, the backup time is generally short, so that a high-rate discharge for supplying a large current to the secondary battery in a relatively short time is required. Required. However, since the capacity of a lead storage battery cannot be secured during high-rate discharge, it is necessary to mount a battery with a large rated capacity. For this reason, the conventional uninterruptible power supply has the drawback that it is large due to the space for accommodating the battery and that the weight is extremely heavy.

In order to solve such a disadvantage, it is conceivable to use a lithium ion battery capable of high-rate discharge. According to this, even if the discharge rate is high, the battery capacity can be reduced because the capacity decrease is small, and the energy density is considerably higher than that of the lead storage battery, so that a significant reduction in size and weight can be achieved. . However, lithium-ion secondary batteries are very susceptible to overcharge and overdischarge, so charge / discharge control is very complicated.Moreover, if many cells are connected in series to secure a high voltage, imbalance between cells occurs. Had problems such as safety problems.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a small and lightweight uninterruptible power supply which enables use of a lithium ion secondary battery.

[0006]

According to a first aspect of the present invention, there is provided an uninterruptible power supply comprising: a plurality of battery modules each having a plurality of lithium ion secondary cells connected in series; A battery circuit configured to obtain a required output voltage, wherein the battery module includes a charging circuit connected to a series circuit of the cells for charging the cell group;
It is characterized in that a battery protection circuit having a function of preventing overcharging and overdischarging of each cell is provided.

In this case, the battery module may further include a cell balance circuit for discharging cells having a voltage equal to or higher than a predetermined voltage (the invention according to claim 2). The protection circuit may be configured to stop the charging operation of the charging circuit when a temperature equal to or higher than a predetermined temperature is detected by the temperature sensor (the invention of claim 5). Also, a configuration may be provided that includes an inverter circuit that converts a DC output of a battery power supply into an AC (the invention according to claim 3). In this case, the battery protection circuit of the battery module can detect the voltage of each of the cells. The operation of the inverter circuit may be stopped when it is detected that the voltage has dropped below a predetermined value (the invention of claim 4).

[0008]

According to the present invention, since a lithium ion battery is used as a battery power source, a battery with a small rated capacity can be used even at a high discharge rate, and the energy density is high. Can be achieved. Also, the battery power supply is modularized by connecting a plurality of lithium ion secondary battery cells in series,
Since each battery module has a charging circuit and a battery protection circuit, if the voltage of one cell rises to a predetermined value or more during charging, charging is stopped to prevent overcharging, and the voltage of even one cell has a predetermined value. When the voltage drops below, the discharge is stopped to prevent overdischarge. Furthermore, when a cell balance circuit is provided in each battery module, when there is a cell that detects a voltage of each cell and exceeds a predetermined voltage,
Since the discharge of the cells is performed, the balance between the cells can be balanced, and the occurrence of local overvoltage can be reliably prevented.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to an uninterruptible power supply of a constant inverter power supply system will be described below with reference to the drawings. The AC input terminal 10 is connected to the converter 1 via an input transformer 11 and a choke coil 12.
3 where the AC power is converted to DC and supplied to the inverter 14. An output transformer 15 of the inverter 14 is connected to an AC output terminal 17 via an AC switch 16. A battery power supply 20 according to the present invention is connected between the converter 13 and the inverter 14 so that the battery power is charged from an AC line (not shown) and DC power can be supplied to the inverter 14 via the backflow prevention diode 18. I have.

The battery power source 20 is configured to obtain a required voltage by connecting a plurality of (for example, seven) battery modules 30 in series, and all of the battery modules 30 have the same standardized configuration. This is shown in detail in FIG. 2, which will be described. Each battery module 30 includes a cell 31 of a lithium ion secondary battery.
Are connected in series, and the rated output voltage is, for example, 14.4.
V is set. A charging circuit 32 is provided for the series circuit of each cell 31 so that float charging can be performed. The charging circuit 32 is configured by, for example, a switching power supply that inputs AC 100 V and outputs DC 16.4 V.

The battery module 30 is provided with a battery protection circuit 33, and a voltage signal for each cell 31 and a temperature signal disposed at the center of a group of four cells 31, for example, two cells arranged in two rows. A temperature signal from the sensor 34 is provided. The battery protection circuit 33 is provided when the voltage of any one of the four cells 31 falls below a predetermined voltage, or when the series voltage of the group of four cells 31 falls below a predetermined voltage. The operation of the inverter 14 is stopped by outputting a discharge stop signal Ss to the inverter 14, so that overdischarge of each cell 31 is prevented. In addition, the battery protection circuit 33 is provided when the voltage of any one of the four cells 31 rises above a predetermined voltage, when the series voltage of the group of four cells 31 rises above a predetermined voltage, or when the temperature rises. When the temperature of the cell 31 rises above a predetermined temperature by the sensor 34, the operation of the charging circuit 32 is stopped to prevent the cell 31 from being overcharged.

On the other hand, each cell 31 has a resistor 35 and a switching element 36 composed of, for example, an FET in parallel with them.
Are connected in series. Then, the battery protection circuit 33 monitors the voltage of each cell 31, and when any one of the cells 31 rises to a predetermined voltage or more, stops the charging operation as described above and switches the switching corresponding to the cell 31. The element 36 is turned on to cause discharge. As a result, when the voltage of the cell 31 decreases, the switching element 36 returns to off. Thus, it is possible to prevent any one of the four cells 31 from being locally overcharged and to balance the cells 31, and a part of the battery protection circuit 33 and the discharge The circuit 37 forms a cell balance circuit.

Further, as described above, by arranging seven 4-cell battery modules 30 in series, as many as 28 lithium-ion secondary battery cells 31 are connected in series. Each is a battery protection circuit 3
3, the charge and discharge are monitored and protected, and the balance between the cells 31 is maintained by the cell balance circuit, so that the voltage can be safely increased. With such a configuration in which battery protection and charging of each battery module 30 are ensured, a lithium ion secondary battery can be used for the first time, and a significant reduction in size and weight can be achieved.

The present invention is not limited to the above-described embodiment. For example, the following embodiments also belong to the technical scope of the present invention. (1) In the above embodiment, the configuration in which the state of the cell 31 is detected by detecting the voltage of each cell 31 in the battery module 30 is not limited thereto. In other words, it is only necessary to have a function of detecting the state of the cell to prevent overcharge and overdischarge. (2) In the above embodiment, the example of the AC output uninterruptible power supply including the inverter 14 has been described, but a DC output may be used. (3) In the above embodiment, the battery module 30 is configured by connecting the four cells 31 in series, and connecting the seven battery modules 30 in series to configure the battery power source 20. Of course, the number of series connections is not limited to this.

[Brief description of the drawings]

FIG. 1 is an overall block diagram of an uninterruptible power supply according to an embodiment of the present invention.

FIG. 2 is a block diagram of a battery module.

[Explanation of symbols]

 13 Converter 14 Inverter 20 Battery power supply 30 Battery module 31 Cell 32 Charge circuit 33 Battery protection circuit 34 Temperature sensor 36 Discharge circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02J 7/00 302 H02J 7/00 302C 302D 7/04 7/04 L 7/10 7/10 L 9 / 06 503 9/06 503A 503B 504 504B F-term (Reference) 5G003 AA01 BA03 CA14 CB01 CB04 CC04 DA13 GA01 5G015 FA08 GA06 GA07 HA04 JA09 JA36 JA53 JA55 5H030 AA03 AA04 AS03 BB01 BB21 FF22 FF42 FF43 FF43 FF43 FF43 FF43 FF43 FF43 FF43 FF43 FF43 FF43 FF43 FF43 FF43 FF43 FF43 FF43 FF43

Claims (5)

[Claims] 1. A battery power source comprising a plurality of lithium ion secondary battery cells connected in series to obtain a required output voltage by connecting a plurality of battery modules in series. The battery module comprises: An uninterruptible power supply, comprising: a charging circuit connected to the series circuit of the cells for charging the cell group; and a battery protection circuit having a function of preventing overcharging and overdischarging of each cell. apparatus. 2. The uninterruptible power supply according to claim 1, wherein the battery module further includes a cell balance circuit for discharging cells having a voltage equal to or higher than a predetermined voltage. 3. A battery power supply in which a plurality of lithium ion secondary battery cells are connected in series to obtain a required output voltage by connecting a plurality of battery modules in series, and a DC output of the battery power supply. An inverter circuit that converts the current into an alternating current and supplies the load to a load.The battery module includes a charging circuit that is connected to a series circuit of the cells and charges the cell group, and detects a state of each of the cells. An uninterruptible power supply device comprising: a battery protection circuit having a function of preventing overcharge and overdischarge; and a cell balance circuit that detects a voltage between the cells and discharges a cell having a predetermined voltage or more. 4. The battery protection circuit of the battery module is capable of detecting the voltage of each cell, and stops the operation of the inverter circuit when detecting that the voltage drops below a predetermined value. The uninterruptible power supply according to claim 3, wherein 5. The battery module is provided with a temperature sensor for detecting a temperature of the cell, and the battery protection circuit performs a charging operation of the charging circuit when a temperature equal to or higher than a predetermined temperature is detected by the temperature sensor. The uninterruptible power supply according to any one of claims 1 to 4, wherein the power supply is stopped.