JP2017143682A - Backup storage battery of power supply for controlling industrial machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable and low-cost backup power supply, capable of securing power necessary for controlling to safely halt an industrial machine.SOLUTION: A backup storage battery (8) is adopted as backup power supply to enable charging by a float charging method. The backup storage battery (8) is connected to a positive voltage line (P) and a negative voltage line (N) of a DC voltage line, through a charge/discharge circuit (10). The charge/discharge circuit (10) includes: a chopper circuit (17) connected in series between the positive voltage line (P) and the negative voltage line (N); and a plurality of diode groups (18) connected in series between a positive terminal (8P) of the backup storage battery (8) and the positive voltage line (P). This enables charging the backup storage battery (8) without an overcharge. A voltage monitoring circuit (20) is provided between the positive voltage line (P) and the negative voltage line (N). By this, a voltage reduction due to deterioration of the backup storage battery (8) is monitored.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a backup storage battery for a control power source of an industrial machine such as an injection molding machine. When power supply to the industrial machine is stopped due to a power failure or the like, the control device and the control computer are stably stopped. The present invention relates to a backup storage battery for a control power source of an industrial machine that supplies electric power necessary for the operation.

  Industrial machines are composed of various devices, and these are controlled by a controller, that is, a control computer. For example, an injection molding machine, which is a kind of industrial machine, is composed of an injection device that melts and injects resin, a mold clamping device that clamps a mold, a projection device that projects a molded product from the mold, and the like. Each device is controlled by a control computer provided in the injection molding machine.

  In a general computer, an OS including a file system, various applications, data, and the like are stored in an external storage device, that is, a hard disk. And processed by the CPU. At this time, management information and data of the file system, which is a part of the OS, are temporarily stored in the volatile memory, and when the data is rewritten, it is reflected on the hard disk. However, it is difficult to employ such a general computer in industrial machines. The control computer provided in the industrial machine is driven by a three-phase AC voltage supplied from the factory with a predetermined voltage, for example, a DC voltage of 24 V by an AC / DC converter or the like. This is because the power supplied to the control computer is inevitably stopped when a problem occurs and a problem occurs in the control computer. Specifically, an inconsistency occurs in the OS file system. The file system appropriately manages all information stored in the hard disk, that is, the OS code, application, and data, and reads and writes such information according to instructions from the OS. In the volatile memory, file system management information is temporarily stored. The file system performs writing on the hard disk according to the management information. However, if the control computer stops due to a power failure, the management information of the file system on the volatile memory is lost. This causes inconsistency in the file system and inconsistency in information on the hard disk. This causes a problem that the startup of the OS is delayed or cannot be started at the next startup. There may also be a problem that important data cannot be restored. Therefore, the control computer provided in the industrial machine is configured as follows so that the file system does not become inconsistent even if a power failure occurs. That is, the control computer reads all the OS including the file system, all the applications, and all the data from the hard disk before starting. These are stored in a volatile memory. Then, the volatile memory area in which these pieces of information are stored is treated as a virtual hard disk and activated. Thereafter, the control computer operates without accessing the hard disk. Since the control computer is activated in this way, even if it is stopped by a power failure or the like and all information on the volatile memory is lost, the information on the hard disk is not affected. That is, there is no inconsistency in information on the hard disk. Therefore, no problem occurs at the next start-up.

  Since the control computer is configured as described above, general-purpose hardware cannot be used, and dedicated hardware is required. This is because the OS and all necessary data can be read from the hard disk into the volatile memory before the OS is started. Since dedicated hardware is required, the control computer is expensive. If the problem of stoppage due to a power failure is solved, the OS can be started in the same manner as a general computer. Then, general-purpose hardware with a low cost can be adopted, so that a control computer can be provided at a low cost. The problem of a stop due to a power failure can be solved by preparing a backup power supply that operates in the event of a power failure so that the OS on the control computer can be safely stopped. An electric injection molding machine in which power is supplied to a control computer at the time of a power failure is described in Patent Document 1.

JP 2013-18152 A

  The electric injection molding machine described in Patent Document 1 includes a power storage device that can store DC voltage power. The electric injection molding machine is provided with a converter that converts a three-phase AC voltage supplied from a factory into a DC voltage, and this DC voltage is supplied to the servo amplifier of the servo motor that drives each device. . The power storage device is connected to the DC voltage supply line. When the power supply from the factory is normal, the power storage device acts to smooth the power required by the servo amplifier. That is, when the power consumption of the servo amplifier is small, the power storage device takes in the DC voltage and boosts it and stores it in the internal capacitor. When the power consumption of the servo amplifier is large, the stored power is supplied to the DC voltage. ing. However, if a power failure occurs in the factory, the power stored in the power storage device is stepped down to a predetermined voltage, for example, 24 V by the DC / DC converter, and supplied to the control computer. As a result, the control computer can execute the processing necessary to safely stop the electric injection molding machine, and can also stop itself safely.

  Since the electric injection molding machine described in Patent Document 1 includes an electric power storage device, electric power that can be safely stopped by the control computer can be secured. In addition, it is possible to secure electric power necessary to stop each device in a safe state. Then, general-purpose hardware used for a general computer can be adopted as the control computer. That is, a control computer can be provided at low cost. However, there are problems. In order to safely stop the control computer, it is necessary to supply power for about 15 seconds. Although the DC voltage to be supplied may be relatively low, the amount of power required is relatively large because power must be supplied for such a long time. In addition, if an industrial device is to be stopped safely, a large amount of power is required in a relatively short time. The power storage device described in Patent Document 1 stores power from a DC voltage in a capacitor, but generally the amount of power that can be stored in a capacitor is relatively small. To secure the required amount of power, a large capacity capacitor is required. This increases the cost of the power storage device. There are other problems. The power storage device described in Patent Document 1 targets not only a control computer but also a servo amplifier as a power supply destination during a power failure. In this case, it is necessary to supply a relatively high DC voltage, and it is necessary to step down and supply the voltage to the control computer using a DC / DC converter. If it does so, the apparatus for supplying electric power to the computer for control will become a big scale, and cost will increase.

  Therefore, for example, it is conceivable to supply power to the control computer from an uninterruptible power supply, that is, a UPS. This is because the UPS always stores electric power by a storage battery and secures a sufficient amount of electric power. However, the UPS generally employs a trickle charging method, and the storage battery is disconnected when the power supply of the factory is normal, and the storage battery is connected by a relay or the like only when a power failure is detected. It is supplied to the control computer. Although it is necessary to detect this reliably at the time of a power failure and operate the relay in a short time, there is a drawback that the cost increases when an uninterruptible power supply device with high reliability is obtained. There are other problems when using storage batteries. This is because the storage battery is liable to be deteriorated due to overcharge, or the voltage is lowered due to a sulfation phenomenon. If protection from overcharge and voltage drop detection are not properly performed, there is a problem in reliability.

  An object of the present invention is to provide a backup power supply for an industrial machine control power supply that solves the above-described problems. Specifically, the control computer is a general-purpose computer that is used in a general computer. When such a control computer is adopted, the control computer can be stopped safely even in the event of a power failure, and industrial machinery can be stopped safely. It is an object of the present invention to provide a backup power source that can secure power necessary for the control and is low in cost and high in reliability.

  In order to achieve the above object, the present invention employs a backup storage battery as a backup power source for a control power source for an industrial machine. The backup storage battery is charged by a so-called float charging method and discharged at the time of a power failure. Specifically, the configuration is as follows. That is, the backup storage battery is connected to the positive voltage line and the negative voltage line of the DC voltage line via the charging / discharging circuit. The charge / discharge circuit is connected positively to the reactor and switching element connected in series between the positive voltage line and the negative voltage line, and to the intermediate line drawn from the middle of the reactor and switching element and connected to the positive terminal of the backup storage battery. Consists of an intermediate line diode provided so that the terminal direction is the forward direction, and a plurality of diode groups connected in series so that the positive voltage line direction is the forward direction between the positive terminal and the positive voltage line To do. The negative terminal of the backup storage battery is connected to the negative voltage line. Since it is configured in this way, the backup storage battery can be charged without being overcharged, and a DC voltage is supplied from the backup storage battery to the DC voltage line even if a power failure occurs. The present invention also provides a voltage monitoring circuit for monitoring a DC voltage. The voltage monitoring circuit includes first to third resistors, a shunt regulator, a Zener diode, and a transistor. The first and second resistors are connected in series between the positive voltage line and the negative voltage line in this order, and the third resistor and the Zener diode are connected in series between the positive voltage line and the base of the transistor in this order. The collector and the emitter of the transistor have one of them connected to a predetermined positive voltage line and the other to the negative voltage line, and the shunt regulator has a reference in the middle of the first and second resistors and an anode to the negative voltage line. A cathode is connected between the third resistor and the Zener diode. Since the voltage monitoring circuit is configured in this way, when the voltage of the backup storage battery decreases, no current flows between the collector and the emitter of the transistor, and the deterioration of the backup storage battery can be detected.

Thus, in order to achieve the above object, the invention according to claim 1 is provided in an industrial machine and supplies a DC voltage to a control computer and a control board provided in the industrial machine via a DC voltage line. A backup storage battery at the time of a power failure of the control power supply, wherein the backup storage battery is connected to a positive voltage line and a negative voltage line of the DC voltage line via a predetermined charging / discharging circuit, The charging / discharging circuit is connected in series between the positive voltage line and the negative voltage line, the reactor and the switching element, and is drawn from the middle of the reactor and the switching element and connected to the positive terminal of the backup storage battery An intermediate line diode provided on the intermediate line so that the direction of the positive terminal is a forward direction, and the positive voltage line between the positive terminal and the positive voltage line. A plurality of diode groups connected in series so that the direction is the forward direction, and the negative terminal of the backup storage battery is connected to the negative voltage line, and is configured as a backup storage battery. The
According to a second aspect of the present invention, in the backup storage battery according to the first aspect, a voltage monitoring circuit for monitoring a DC voltage is provided on the DC voltage line, and the voltage monitoring circuit includes first to third resistors. A shunt regulator, a Zener diode, and a transistor, wherein the first and second resistors are connected in series from the positive voltage line to the negative voltage line in this order, and the third resistor and the Zener diode Is connected in series in this order from the positive voltage line to the base of the transistor, and the direction of the positive voltage line of the Zener diode is forward, and one of the collector and emitter of the transistor is predetermined. And the other is connected to the negative voltage line, and the shunt regulator has a reference in the middle of the first and second resistors. In the over de said negative voltage line, the cathode is configured as a backup storage battery, characterized in that is connected to an intermediate of the third resistor and the Zener diode.

  As described above, the present invention provides a control power supply that is provided in an industrial machine and supplies a DC voltage to a control computer or control board provided in the industrial machine via a DC voltage line. Configured as a backup storage battery during a power failure. The backup storage battery is connected to the positive voltage line and the negative voltage line of the DC voltage line via a predetermined charging / discharging circuit. This charging / discharging circuit includes a reactor and a switching element connected in series between a positive voltage line and a negative voltage line, and an intermediate line drawn from the middle of the reactor and the switching element and connected to the positive terminal of the backup storage battery And a plurality of diodes connected in series so that the positive voltage line direction is the forward direction between the positive terminal and the positive voltage line. It consists of a group of diodes. The negative terminal of the backup storage battery is connected to the negative voltage line. Since it is comprised in this way, in a charging / discharging circuit, a closed circuit is formed from a reactor, an intermediate line diode, and a diode group. This closed circuit can suppress the charging voltage to a safe voltage without charging the backup storage battery to an excessively high voltage. This can protect the backup storage battery. Further, since the backup storage battery is connected to the DC voltage line through the diode group, overcharge is also prevented. In the present invention, since the charging / discharging circuit is composed only of inexpensive electronic elements, it can be provided at low cost.

  According to another invention, the DC voltage line is provided with a voltage monitoring circuit for monitoring the DC voltage. The voltage monitoring circuit includes first to third resistors, a shunt regulator, a Zener diode, and a transistor, and the first and second resistors are connected in series from the positive voltage line to the negative voltage line in this order. The third resistor and the Zener diode are connected in series in this order from the positive voltage line to the base of the transistor, and the Zener diode has the positive voltage line oriented in the forward direction, and either the collector or emitter of the transistor is One is connected to a predetermined positive voltage line and the other is connected to a negative voltage line. The shunt regulator has a reference in the middle of the first and second resistors, an anode in the negative voltage line, a cathode in the third resistor and a Zener diode. Are connected in the middle of each. With this configuration, when no current flows between the collector and emitter of the transistor, a decrease in the voltage of the backup storage battery can be detected, and the replacement time of the backup storage battery can be reliably determined.

It is a circuit diagram which shows the backup storage battery system of the power supply for control of the industrial machine which concerns on embodiment of this invention. It is a circuit diagram which shows the charge / discharge circuit of the backup storage battery system of the power supply for control of the industrial machine which concerns on embodiment of this invention. It is a circuit diagram which shows the voltage monitoring circuit of the backup storage battery system of the power supply for control of the industrial machine which concerns on embodiment of this invention.

  Embodiments of the present invention will be described below. The backup storage battery system 1 according to the present embodiment is configured as a backup power source for a control power source of an industrial machine such as an injection molding machine, and supplies power to a control computer or a board provided in the industrial machine at the time of a power failure To do. In general, industrial machines use a control power supply to convert a three-phase AC voltage supplied from a factory into a DC voltage of a predetermined control voltage and supply it to a load such as a control computer or a board. FIG. 1 shows such a control power source 2, a DC voltage line 3 to which a DC voltage is supplied from the control power source 2, and a load 4 such as a control computer. In the present embodiment, the DC voltage line 3 is composed of a positive voltage line P and a negative voltage line N, and the negative voltage line N is composed of a grounded common. The backup power supply system 1 according to the present embodiment is provided on such a DC voltage line 3.

  The backup power supply system 1 according to the present embodiment includes a backup storage battery 8, a charging / discharging circuit 10 that charges the backup storage battery 8 with power and discharges power from the backup storage battery 8 to the DC voltage line 3, and the backup storage battery 8. And a voltage monitoring circuit 20 for monitoring the voltage of the current.

  The charging / discharging circuit 10 according to the present embodiment is composed of a plurality of electronic elements. First, a line connected from the positive voltage line P to the negative voltage line N includes a first auxiliary resistor 11 that is an auxiliary resistor for ensuring the safety of the circuit, a reactor 12 that boosts the voltage, and an FET. The switching elements 13 are connected in series in this order. An intermediate line 14 is drawn from the middle of the reactor 12 and the switching element 13 and connected to the positive terminal 8P of the backup storage battery 8. To be precise, the intermediate line 14 is not directly connected to the positive terminal 8P, but is connected via a second auxiliary resistor 15 which is an auxiliary resistor. Such an intermediate line 14 is provided with a diode whose forward direction is the direction of the positive terminal 8P, that is, an intermediate line diode 16. The negative terminal 8N of the backup storage battery 8 is connected to the negative voltage line N. A circuit composed of these electronic elements constitutes a so-called chopper circuit 17 that is conventionally known. When the switching element 13 is repeatedly turned ON / OFF, the DC voltage flowing through the DC voltage line 3 is boosted and can be stored in the backup storage battery 8. It is like that.

  The charging / discharging circuit 10 according to the present embodiment is provided with not only the chopper circuit 17 but also an electronic element characteristic of the present invention. That is, the diode group 18 is composed of a plurality of diodes. The diode group 18 is provided in series to the line connected to the positive voltage line P from the positive terminal 8P of the backup storage battery 8 via the second auxiliary resistor 15 with the positive voltage line P direction as the forward direction. With such a diode group 18, a closed circuit including the first auxiliary resistor 11, the reactor 12, the intermediate line diode 16, and the diode group 18 is formed in the charging / discharging circuit 10. As will be described in detail later, when the DC voltage is boosted by the chopper circuit 17, the backup storage battery 8 is protected without being boosted to an excessive voltage. The diode group 18 also has an effect of discharging a DC voltage from the backup storage battery 8 to the DC voltage line 3 during a power failure.

  The voltage monitoring circuit 20 will be described. The voltage monitoring circuit 20 is also composed of a plurality of electronic elements. First, the first and second resistors 21 and 22 are connected in series in this order from the positive voltage line P to the negative voltage line N, whereby the DC voltage line 3 The DC voltage is divided. Next, a third resistor 23 and a Zener diode 24 are connected in series from the positive voltage line P in this order, and are connected to the base of an NPN transistor 25 via a third auxiliary resistor 27. The Zener diode 24 is connected so that the direction of the positive voltage line P is the forward direction. The collector of the transistor 25 is connected to the DC positive terminal 26 of 5V via the fourth auxiliary resistor 31, and the emitter is connected to the negative voltage line N. Therefore, when the potential between the third resistor 23 and the Zener diode 24 becomes higher than a voltage exceeding the sum of the breakdown voltage of the Zener diode 24 and the voltage between the base and emitter of the transistor 25, current flows through the Zener diode 24. This flows between the base and emitter of the transistor 25 so that the potential on the collector side becomes zero. On the other hand, when the potential between the third resistor 23 and the Zener diode 24 is low, no current flows between the base and the emitter of the transistor 25, the current is cut between the collector and the emitter, and the potential on the collector side becomes 5V. Become. The potential on the collector side can be monitored by a monitoring terminal 28 provided on the collector side.

  The voltage monitoring circuit 20 is provided with a shunt regulator 29. The reference of the shunt regulator 29 is at an intermediate point between the first and second resistors 21 and 22, the anode is at the negative voltage line N, and the cathode is at the third resistor 23. The intermediate point of the Zener diode 24 is connected via a fifth auxiliary resistor 32. Although the potential at these intermediate points is divided by the first and second resistors 21 and 22, the resistance value of each of the first and second resistors 21 and 22 is determined by the voltage of the DC voltage line 3 being a predetermined voltage. For example, if it is 20V, the potential at the intermediate point is selected to be the reference voltage of the shunt regulator 29, for example, 2.5V. Therefore, when the voltage of the DC voltage line 3 is higher than 20V, the current flows from the cathode of the shunt regulator 29 to the anode because the intermediate point of the first and second resistors 21 and 22, that is, the reference potential exceeds the reference potential. This current causes the voltage to drop at the third resistor 23 and the potential on the cathode side of the Zener diode 24 is low. However, when the voltage of the DC voltage line 3 drops below 20V, the reference potential of the shunt regulator 29 becomes lower than the reference potential and the shunt regulator 29 is insulated. Then, as will be described later, the potential on the cathode side of the Zener diode 24 becomes high. In order to stabilize the reference and cathode potential of the shunt regulator 29, the voltage monitoring circuit 20 is provided with first and second capacitors 33 and 34 between them and the negative voltage line N, respectively.

  The operation of the backup storage battery system 1 according to the present embodiment will be described. The operation in normal operation in which a three-phase AC voltage is supplied from the factory and a DC voltage is supplied from the control power supply 2 will be described. During normal operation, the backup storage battery system 1 charges the backup storage value 8 with power by the charge / discharge circuit 10. That is, ON / OFF of the switching element 13 is repeated for a predetermined time. When the switching element 13 is turned on, a current flows from the positive voltage line P to the first auxiliary resistor 11, the reactor 12, the switching element 13, and the negative voltage line N as indicated by the arrow 41 in FIG. When the switching element 13 is turned off, an electromotive force is generated in the reactor 12 due to the current flowing through the reactor 12. Due to this electromotive force, a current flows as indicated by the arrow of reference numeral 42 and the arrow of reference numeral 43. The former current flows through the closed circuit in the order of the reactor 12, the intermediate line diode 16, the diode group 18, the first auxiliary resistor 11, and the reactor 12. As a result, the potential at the reference numeral 44 is slightly higher than the potential of the positive voltage line P, that is, higher than the potential dropped by the diode group 18. When the diode group 18 is composed of four diodes and a voltage drop of 0.6 V is generated per diode, the potential of the positive voltage line P becomes higher by 0.6 V × 4 = 2.4 V. . Then, as indicated by the arrow 43, the current flowing through the first auxiliary resistor 11, the reactor 12, the intermediate line diode 16, and the second auxiliary resistor 15 is a potential close to the potential at the reference numeral 44. Since the backup storage battery 8 reaches the positive terminal 8P, the backup storage battery 8 is charged with a voltage higher than the DC voltage of the DC voltage line 3 by the voltage drop of the diode group 18. Since the backup storage battery 8 is charged with a voltage slightly higher than the direct current voltage, an excessive voltage is not applied and the backup storage battery 8 is reliably protected. When the backup storage battery 8 is charged with power by repeating ON / OFF of the switching element 13, the switching element 13 is stopped. Even if the backup storage battery 8 is temporarily charged with excessive power and the voltage of the backup storage battery 8 increases, the backup storage battery 8 to the second auxiliary resistor 15, as indicated by the arrow 45, Since current flows to the DC voltage line 3 via the diode group 18, the voltage of the backup storage battery 8 quickly recovers to a normal range.

  An operation when the supply of the DC voltage from the control power supply 2 is stopped due to a power failure or the like will be described. When a power failure occurs, the DC voltage of the DC voltage line 3 decreases. Then, the power charged in the backup storage battery 8 is supplied to the DC voltage line 3 via the second auxiliary resistor 15 and the diode group 18 as indicated by the arrow 45. As a result, the DC voltage line 3 is supplied with a DC voltage without lowering the voltage, and the load 4 such as the control computer can operate normally. Therefore, the control computer can be stopped safely.

  In the backup storage battery system 1 according to the present embodiment, the voltage monitoring circuit 20 constantly monitors the DC voltage of the DC voltage line 3. This will be explained. When the DC voltage of the DC voltage line 3 is in a normal range, for example, 20 V or more, the DC voltage is divided by the first and second resistors 21 and 22, and the reference potential of the shunt regulator 29 is shunted. It becomes slightly higher than the reference potential of the regulator 29. Then, current flows from the cathode of the shunt regulator 29 to the anode. As a result, a current flows like the positive voltage line P, the third resistor 23, the fifth auxiliary resistor 32, the shunt regulator 29, and the negative voltage line N as indicated by the arrow 46 in FIG. . As a result, the potential at the position 47 is greatly lowered from the potential of the positive voltage line P due to the voltage drop of the third resistor 23. At this time, the potential at the position of reference numeral 47 is lower than the breakdown voltage of the Zener diode 24. As a result, no current can flow through the Zener diode 24, and the transistor 25 does not operate. That is, the potential detected at the monitoring terminal 28 is 5V. It is determined that the DC voltage of the DC voltage line 3 is normal.

  When the DC voltage of the DC voltage line 3 decreases, the potential divided by the first and second resistors 21 and 22, that is, the reference potential of the shunt regulator 29 decreases. When the potential decreases and becomes lower than the reference voltage of the shunt regulator 29, no current flows between the cathode and the anode of the shunt regulator 29. Then, since the voltage does not drop in the third resistor 23, the potential of the reference numeral 47 rises. When the potential increases beyond the breakdown voltage of the Zener diode 24, current flows between the Zener diode 24, the third auxiliary resistor 27, and the base-emitter of the transistor 25. As a result, the transistor 25 becomes conductive, and 0 V is detected at the monitoring terminal 28. It is detected that the DC voltage of the DC voltage line 3 has decreased.

  The voltage monitoring circuit 20 is provided to determine whether or not the voltage of the backup storage battery 8 is appropriate when power is supplied from the backup storage battery 8 with the control power supply 2 stopped. The control power supply 2 is periodically stopped and a DC voltage is supplied from the backup storage battery 8 so that the voltage of the backup storage battery 8 is inspected. Thereby, it can be determined whether or not the backup storage battery 8 is deteriorated.

  Various modifications can be made to the backup storage battery system 1 for the power supply for control of the industrial machine according to the present embodiment. For example, in the charging / discharging circuit 10, the number of diodes in the diode group 18 can be modified. To charge the backup storage battery 8 at a relatively high voltage, the number of diodes may be increased, and when charging at a relatively low voltage, the number of diodes may be reduced. The voltage monitoring circuit 20 can also be modified. For example, the transistor 25 can be formed of a PNP type. When the PNP transistor 25 is employed, the emitter side is connected to the positive DC terminal 26 and the collector side is connected to the negative voltage line N.

DESCRIPTION OF SYMBOLS 1 Backup storage battery system 2 Control power supply 3 DC voltage line 4 Load 8 Backup storage battery 8P Positive terminal 10 Charge / discharge circuit 12 Reactor 13 Switching element 14 Intermediate line 16 Intermediate line diode 17 Chopper circuit 18 Diode group 20 Voltage monitoring circuit 21 1st Resistance 22 second resistance 23 third resistance 24 Zener diode 25 transistor 29 shunt regulator P positive voltage line N negative voltage line

Claims (2)

A backup storage battery at the time of a power failure of a control power source provided in an industrial machine and configured to supply a DC voltage via a DC voltage line to a control computer or control board provided in the industrial machine,
The backup storage battery is connected to a positive voltage line and a negative voltage line of the DC voltage line through a predetermined charging / discharging circuit,
The charging / discharging circuit includes a reactor and a switching element connected in series between the positive voltage line and the negative voltage line, and is drawn from the middle of the reactor and the switching element to the positive terminal of the backup storage battery. The intermediate line diode provided so that the direction of the positive terminal is a forward direction on the connected intermediate line, and the direction of the positive voltage line is the forward direction between the positive terminal and the positive voltage line And a plurality of diode groups connected in series,
The backup storage battery, wherein a negative terminal of the backup storage battery is connected to the negative voltage line. The backup storage battery according to claim 1, wherein the DC voltage line is provided with a voltage monitoring circuit for monitoring a DC voltage,
The voltage monitoring circuit includes first to third resistors, a shunt regulator, a Zener diode, and a transistor, and the first and second resistors are serially connected in this order from the positive voltage line to the negative voltage line. The third resistor and the Zener diode are connected in series in this order from the positive voltage line to the base of the transistor, and the direction of the positive voltage line is forward in the Zener diode. One of the collector and emitter of the transistor is connected to a predetermined positive voltage line and the other is connected to the negative voltage line. The shunt regulator has a reference in the middle of the first and second resistors, and an anode connected to the negative voltage line. The negative voltage line has a cathode connected between the third resistor and the Zener diode, respectively. Battery.

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