JP2012120352A - Programmable controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a programmable controller, which backs up its memory using a main battery and an auxiliary battery in combination with each other, capable of reducing a wasteful consumption of resources by suppressing a replacement of the auxiliary battery conventionally executed at the time of the replacement of the main battery and capable of backing up its memory for a long period even after an alarm that warns a reduced battery residual amount of the main battery.SOLUTION: A main battery is configured so that it is detachable from a programmable controller, while an auxiliary battery is configured using a rechargeable secondary battery and mounted in the programmable controller main unit. The programmable controller is provided with charging means which starts the charging of the auxiliary battery when an output voltage of the auxiliary battery becomes less than a recharging voltage E2, and stops the charging of the auxiliary battery when the output voltage of the auxiliary battery reaches a regulator output voltage E1 by the charging.

Description

  The present invention relates to a programmable controller having a function of backing up a memory holding data with a battery.

  Programmable controllers (hereinafter also abbreviated as PLC) are used for machine control and monitoring in a wide range of fields such as FA (factory automation). In order to save the PLC data, a storage medium such as static RAM (SRAM) is used, and the battery is configured to back up the SRAM when the main power is off. In order to increase the SRAM backup time, It is conventionally known to use a large capacity battery as a backup battery.

  FIG. 4 is a diagram showing an outline of a discharge characteristic curve of a lithium battery widely used as a large capacity battery. FIG. 4B is an enlarged view of the time axis of the voltage drop portion of FIG. As shown in these figures, the lithium battery has a characteristic that a high voltage can be maintained until the battery capacity is almost lost, but the time from when the battery voltage is lowered until the battery capacity is exhausted is extremely short.

  For this reason, in the PLC that detects that the remaining battery level has decreased due to the decrease in the battery voltage and generates a warning, the memory is stored after the battery voltage decreases to the warning level voltage Ewr and generates a warning. It is difficult to extend the time Tbk (backup available time) until the voltage Eth (minimum voltage that can be backed up) is reached. Further, in recent years, since the current consumption during the backup of the SRAM has increased, it has become more difficult to extend the backup possible time Tbk.

  Therefore, for example, even if an alarm is generated due to a battery voltage drop during a PLC stoppage due to, for example, a factory holiday, battery replacement is not performed, and there is a high concern that data will be lost before the operation is restarted. It has become. That is, the backup possible time Tbk from when the warning is generated to when the battery replacement should be completed is shortened, and the memory backup during the PLC stop period cannot be satisfied.

  In order to prevent such data loss, a backup circuit that functions to maintain the backup of the memory instead of the main battery and warns of a decrease in the remaining battery power, and then allows the backup of the memory to be extended. This is disclosed in Japanese Unexamined Patent Publication No. 2008-79438.

JP 2008-79438 A

  However, in the conventional invention described in Japanese Patent Application Laid-Open No. 2008-79438, since the auxiliary battery is built in the battery unit on which the main battery is mounted, the auxiliary battery is replaced together with the main battery every time the battery unit is replaced. To be maintained. That is, there is a problem that, although the auxiliary battery has not expired, the auxiliary battery is replaced together with the replacement of the main battery, and resources are wasted. Further, since the auxiliary battery is a small one built in the battery unit, its battery capacity is small, and there is a limit to the extension time of backup by the auxiliary battery.

  The present invention has been devised in view of the above-mentioned problems, and its purpose is to enable memory backup for a long time even after a warning due to a decrease in the remaining battery capacity, and to prevent useless resources by suppressing replacement of auxiliary batteries. It is to provide a PLC that suppresses the consumption of electricity.

In order to solve the above problems, the present invention is configured as follows.
The programmable controller according to the invention of claim 1 is a programmable controller having a data backup function,
Storage means for holding data, a power supply section for supplying current to the storage means, a backup battery unit for supplying current to the storage means when the power supply section is off, and an output voltage of the backup battery unit An auxiliary battery unit that supplies current to the storage means instead of the backup battery unit when the battery unit is replaced with a first threshold value or less,
The auxiliary battery unit starts charging the auxiliary battery when the auxiliary battery is rechargeable and the output voltage of the auxiliary battery is equal to or lower than a second threshold value for charging the auxiliary battery. And charging means for ending charging of the auxiliary battery when the voltage reaches a third threshold value for ending charging of the auxiliary battery.

  The invention according to claim 2 is the programmable controller according to claim 1, wherein the second threshold value is a minimum data retention voltage of the storage means as a reference voltage, and the auxiliary battery backs up the storage means for a predetermined time. In this case, the falling voltage of the auxiliary battery is configured to be equal to or higher than the voltage value added to the reference voltage.

  The invention according to claim 3 is the programmable controller according to claim 1 or 2, wherein the auxiliary battery unit is mounted on the programmable controller body together with the storage means, and the battery unit is separable from the programmable controller body. Configured.

  The invention according to claim 4 is the programmable controller according to any one of claims 1 to 3, wherein the auxiliary battery unit further includes a counting means for counting the number of times of charging of the auxiliary battery, and the programmable controller The controller is further configured to further include a charging number alarm unit that issues an alarm when the number of times of charging by the counting unit reaches a limit number of times that the auxiliary battery can be charged.

  The invention according to claim 5 is the programmable controller according to any one of claims 1 to 4, wherein the programmable controller is configured such that when the output voltage of the backup battery unit falls below the first threshold value, the backup battery unit. A voltage drop warning means for issuing a voltage drop warning is further provided.

  According to the present invention, in addition to the main battery that backs up the memory during the non-operation period of the PLC, the secondary battery that can be charged by the charging means is a secondary battery that starts memory backup when the main battery voltage falls below the alarm generation voltage level. A secondary battery was provided. In addition, the present invention provides a voltage obtained by adding a lower voltage of the secondary battery when the secondary battery backs up the memory during the maximum non-operating time of the PLC as a threshold value for charging the secondary battery. Value. With this configuration, the present invention can provide a highly reliable PLC in which data in the memory is not lost during the non-operation period of the PLC.

  Further, in the present invention, after the secondary battery is charged, it is not recharged until the voltage of the secondary battery is equal to or lower than the charging start threshold value, so that frequent charging is prevented and the life of the secondary battery is extended. be able to.

  Therefore, even when the secondary battery is used as an auxiliary battery, the present invention can reduce maintenance (substantially maintenance-free) and suppress wasteful resource consumption.

1 is a configuration diagram of a memory backup circuit showing an embodiment of the present invention. The figure which shows one Example of the internal structure of the secondary battery charging circuit in FIG. FIG. 1 is a time chart showing an embodiment of the operation of FIG. Diagram showing an example of battery discharge characteristics The figure explaining the module configuration of a programmable controller and the power supply method

Next, an embodiment of the present invention will be described with reference to FIGS.
FIG. 5 is a configuration diagram showing a basic configuration of a PLC to which the present invention is applied and an example of a PLC power feeding method. In the figure, reference numeral 200 denotes a system power supply, which supplies a predetermined voltage to various modules by supplying commercial power from the outside during operation of the PLC. Reference numerals 301 and 302 are CPU modules (common code is 300) that performs overall control of the entire PLC while communicating with the input / output module 400 described below. The memory backup circuit of the present invention is incorporated as described below. ing.

  Reference numerals 401, 402,..., 406 denote input / output modules (common reference numeral 400), which are used to input signals from switches and sensors attached to a monitoring control target device (not shown) and to monitor and control actuators. A control output signal is output to the target device. Reference numeral 100 denotes a base board on which these various modules and a system power supply are mounted.

  The system power supply 200 supplies a base board voltage (DC 24 V in this example) S1 to each of the CPU module 300 and the input / output module 400 via the base board 100. Receiving this voltage S1, each module 300, 400 generates a power supply voltage Es for driving a circuit in the module by a power supply circuit 1 described later provided in each module.

  FIG. 1 is a configuration example of a memory backup circuit to which the present invention is applied. This memory backup circuit is incorporated in the CPU module 300. The memory backup circuit includes a power supply circuit 1. The power supply circuit 1 receives a base board voltage S1 and generates a power supply voltage Es that drives a circuit in the CPU module 300. The control unit 12 includes a microprocessor (CPU), a program memory, a working memory, and the like (not shown), and is configured to control an external device via the input / output module 400 by executing a sequence program. Yes.

  Subsequently, reference numeral 3 denotes an SRAM that holds PLC setting data and the like, and is a memory to be backed up. 2 is a main battery (lithium battery) that backs up the SRAM 3 when the PLC is stopped, that is, when it is not in operation, and 2a is the output voltage value. A battery unit 10 that accommodates the main battery 2 is configured to be separable from the main body of the CPU module 300 (to facilitate replacement of the main battery). Reference numeral 4 denotes a warning generation circuit that inputs an output voltage of the main battery 2 and issues a warning when this voltage reaches the warning level voltage Ewr. The warning generation circuit 4 is a circuit that operates using the power supply voltage Es as a power supply. The warning generation circuit 4 compares the output voltage of the main battery 2 with the warning level voltage Ewr, and gives a warning when the output voltage of the main battery 2 falls below the warning level voltage Ewr. (Voltage drop warning means).

  Reference numeral 11 denotes an auxiliary battery unit that backs up the SRAM 3 instead of the main battery 2 when the output voltage of the main battery 2 decreases. The auxiliary battery unit 11 includes a rechargeable secondary battery 8 and a secondary battery charging circuit 9 that charges the secondary battery 8. The secondary battery charging circuit 9 uses the power supply voltage Es as a power source, and charges the secondary battery 8 when the output voltage of the secondary battery 8 falls below a recharge voltage E2 of FIG. Each of the diodes 5, 6, and 7 is a backflow prevention diode. Among the power supply circuit 1, main battery 2, and secondary battery 8, the highest voltage source supplies current to the SRAM 3 through a backflow prevention diode. The power supply voltage Es when the power supply circuit 1 is on is set higher than the output voltage of the main battery 2 and the output voltage of the secondary battery 8.

  FIG. 2 is a diagram illustrating an example of an internal configuration of the secondary battery charging circuit 9. In the figure, reference numeral 93 denotes a three-terminal regulator (also simply referred to as a regulator). The regulator 93 is turned on when the power supply voltage Es is input via the transistor 92 and the diode 94 and outputs the regulator output voltage E1, while it is turned off when the power supply voltage Es is not input. When the regulator 93 is off, the internal resistance of the regulator 93 becomes almost infinite, so that the current of the secondary battery 8 is not discharged to the regulator 93 side. The resistor Rs is a current limiting resistor that limits the output current of the regulator 93.

  A comparator 91 compares the output voltage of the secondary battery 8 input to its (−) input terminal with the voltage Ecpp applied to the (+) input terminal, and outputs the output from the “L” level to “ Switch to "H" level or from "H" level to "L" level. A transistor 92 is turned on / off in accordance with the output of the comparator 91 and functions as a switch for supplying the power supply voltage Es to the regulator 93. Reference numeral 94 denotes a diode that prevents reverse current flow from the secondary battery 8 side to the transistor 92 side.

  The resistors R1 and R2 are voltage dividing resistors that divide the power supply voltage Es and determine the voltage Ecpp. The resistor Rf is a feedback resistor that changes the voltage Ecpp in accordance with the output of the comparator 91, and gives hysteresis characteristics to the input of the comparator 91. These resistors are such that when the comparator 91 outputs an “H” level, the voltage Ecpp is substantially equal to a regulator output voltage E1 of FIG. Is outputting the “L” level, the resistance value is determined so that the voltage Ecpp becomes a recharge voltage E2 in FIG.

  Note that, as will be described later, the regulator output voltage E1 is a threshold value (charging end threshold value) for ending the charging of the secondary battery 8. On the other hand, the recharge voltage E2 is a threshold value (charging start threshold value) at which charging of the secondary battery 8 is started.

Next, the operation of the secondary battery charging circuit 9 of FIG. 2 will be described with reference to FIG.
When the output voltage of the secondary battery 8 falls below the recharge voltage E2 when the power supply voltage Es is being output, that is, the voltage of the (−) input terminal of the comparator 91 becomes the comparator (+) input terminal voltage Ecpp (= When the voltage drops below the recharge voltage E2), the comparator 91 outputs an “H” level. In accordance with this “H” level output, the transistor 92 is turned on, and the regulator 93 outputs the regulator output voltage E1. Then, the regulator 93 starts charging the secondary battery 8 via the charging current limiting resistor Rs (charging starting means). At this time, with the output of the comparator 91 at the “H” level, the comparator (+) input terminal voltage Ecpp is set to a voltage that is substantially equal to the regulator output voltage E1 and slightly lower than the voltage E1.

  Subsequently, the output voltage of the secondary battery increases with charging, and when this voltage reaches and exceeds the regulator output voltage E1, the comparator (−) input terminal voltage exceeds the voltage of the comparator (+) input terminal. In this case, the comparator 91 outputs “L” level. When the comparator 91 outputs the “L” level, the transistor 92 is turned off, and the regulator 93 is also turned off accordingly, and the charging of the secondary battery 8 is ended (charging end means). The comparator (+) input terminal voltage Ecpp is set to the recharge voltage E2 along with the “L” level output of the comparator 91, and the voltage is until the output voltage of the secondary battery 8 falls below the recharge voltage E2. Maintained. Therefore, according to the present invention, frequent charging by the secondary battery charging circuit 9 can be avoided and overcharging can be prevented, so that deterioration of the secondary battery 8 can be suppressed. The auxiliary battery unit 11 includes the above-described charging start means and charging end means, and these two means are also simply referred to as charging means.

  FIG. 3 is a time chart that simulates the operating state of the PLC, and is a diagram for explaining charging and discharging of the secondary battery. In FIG. 3, 3a is the SRAM terminal voltage (thick solid line), 2a is the output voltage of the main battery 2 (thick broken line), and 8a is the output voltage of the secondary battery 8 (one-dot chain line). T (T1, T2,... T14) is an operation period of the PLC, that is, an ON period of the power supply circuit 1. On the other hand, τ (τ1, τ2,... Τ14) is a non-operation period of the PLC, that is, an off period of the power supply circuit 1. In the off period τ, the power supply voltage Es is not supplied, so that the main battery 2 backs up the SRAM 3 through the diode 6 or the secondary battery 8 through the diode 7. Only the non-operation period τ14 is intentionally extended to explain the setting method of the recharge voltage E2.

  In this example, alarm level voltage Ewr> regulator output voltage E1 (charge end threshold)> recharge voltage E2 (charge start threshold). Further, the output voltage 8a of the secondary battery 8 is selected to be lower than the warning level voltage Ewr.

  Further, at time t0 when the operation period T1 starts, the main battery 2 and the secondary battery 8 are in a fully charged state. Further, it is assumed that the main battery 2 and the secondary battery 8 are not self-discharged. In the operation period T, the output voltage of the main battery 2 is unchanged, and the output voltage 8a of the secondary battery 8 is also generated by the secondary battery charging circuit 9. It shall remain unchanged except during the charging period.

  First, the period A from time t0 to t2 will be described. The output voltage 2a of the main battery 2 maintains substantially the initial voltage E0 until it reaches τ3 through the non-operation periods τ1, τ2, but starts to decrease from the non-operation period τ4 and further decreases in the non-operation period τ5. The warning level voltage Ewr is reached at time t1 within the non-operation period τ6. The output voltage 2a of the main battery 2 decreases after time t1, and is substantially equal to the secondary battery output voltage 8a at time t2. As described above, the backup of the memory 3 is performed only by the main battery 2 until the output voltage of the main battery 2 becomes substantially equal to the output voltage of the secondary battery.

  Subsequently, the time t2 and after will be described. In a period B from time t2 to time t4, the output voltage 2a of the main battery 2 is substantially equal to the output voltage 8a of the secondary battery 8 at the start time of the non-operation period τ7. In this case, the main battery 2 and the secondary battery 8 both back up the SRAM 3 while following the same voltage drop curve until the end of the non-operation period τ9, that is, the time point t4, but the remaining amount of the main battery 2 becomes extremely small. Therefore, the current supply capability is in the secondary battery 8, and the backup of the memory 3 is mainly performed by the secondary battery 8.

  Next, a period C from time t4 to time t9 will be described. At the start time (time t4) of the operation period T10, both output voltages of the main battery 2 and the secondary battery 8 have reached the voltage E21, and the voltage E21 is slightly below the recharge voltage E2. When the power supply circuit 1 is turned on at this time, the secondary battery charging circuit 9 immediately starts charging the secondary battery 8, and as a result of this charging, the output voltage 8a of the secondary battery 8 is restored to the regulator output voltage E1. (Period T10).

  Thus, when the secondary battery output voltage 8a reaches the regulator output voltage E1, the secondary battery charging circuit 9 terminates the charging and prevents the secondary battery 8 from being overcharged. That is, the secondary battery 8 is charged with the regulator output voltage E1 as the upper limit value, and charging is terminated when the output voltage of the secondary battery 8 reaches the regulator output voltage E1, so that overcharging is prevented.

  Therefore, after the operation period T10, until the time point t6, the output voltage 8a of the secondary battery 8 exceeds the output voltage 2a of the main battery 2 (in this case, the voltage E21), so the non-operation periods τ10, τ11 , Τ12 and τ13 until time t6, only the secondary battery 8 backs up the memory 3. Note that the output voltage 8a of the secondary battery 8 becomes substantially equal to the recharge voltage E2 at time t5 within the non-operation period τ13, and drops to voltage E21 at time t6. On the other hand, the main battery 2 maintains the voltage E21 and has reached time t6.

  From time t6 to time t7 at the end of the non-operation period τ13, both the main battery 2 and the secondary battery 8 back up the memory 3, and both the main battery 2 and the secondary battery 8 at the time t7 are backed up. The output voltage of the battery slightly decreases from the voltage E21 and decreases to the voltage E22.

  Subsequently, in the operation period T14, similarly to the operation period T10, the secondary battery 8 is charged, and then enters the subsequent non-operation period τ14. The secondary battery 8 reaches the time point t8 while backing up the memory 3, and at this point The output voltage 8a of the secondary battery 8 has dropped to the recharge voltage E2. Even if the PLC is operated slightly before this time t8, that is, when the output voltage 8a of the secondary battery 8 is slightly higher than the recharge voltage E2, the charging of the secondary battery 8 by this operation is performed. Is not done. Therefore, the output voltage 8a of the secondary battery 8 enters the next non-operation period τ while maintaining the recharge voltage E2. Therefore, the minimum output voltage of the secondary battery 8 when entering the non-operation period is substantially equal to the recharge voltage E2.

  Subsequently, time t9 is reached, and at time t9, the output voltage 8a of the secondary battery 8 drops to the voltage E22. Since the PLC is not operated after time t9 and the power supply circuit 1 is not turned on, the time reaches t10 while the secondary battery 8 mainly backs up the memory 3. The output voltage 8a of the secondary battery 8 at time t10 has dropped to the lowest voltage Eth that can back up the memory 3. If this happens, the data held in the SRAM 3 may be lost. In other words, if the PLC is operated before the time point t10 or the replacement work of the main battery 2 is performed, the data held in the memory 3 can be prevented from being damaged.

  Here, the recharge voltage E2 is determined such that the maximum non-operating time is secured, with the time τD1 from the time t10 to the time t8 going back to the starting point as the maximum time of the non-operating time of the PLC. Has been. For example, in a PLC system with a maximum non-operation time of 480 hours (corresponding to 20 days), it is desirable to determine the recharge voltage E2 so that the interval between the time point t10 and the time point t8 is 480 hours or more. That is, the recharge voltage E2 is a voltage obtained by adding the descending voltage of the secondary battery 8 when the secondary battery 8 backs up the memory 3 during the maximum non-operation time of the PLC to the lowest backupable voltage Eth ( Actually, it is necessary to add the forward voltage of the backflow prevention diode).

  In this way, when the non-operation period τ is entered, the main battery 2 has substantially lost the backup capability, and the output voltage 8a of the secondary battery 8 is substantially equal to the recharge voltage E2. However, the subsequent memory backup can be guaranteed for 480 hours (the time τD1 from the time point t8 to the time point t10 is also called the allowable maximum non-energization time). Therefore, if the period of non-operation is less than 20 days, data in the memory will not be lost.

In addition, by setting the recharge voltage E2 as low as possible, the number of times the secondary battery is charged can be suppressed and deterioration of the secondary battery can be prevented.
The output voltage E1 of the regulator 93 is selected to be lower than the warning level voltage Ewr. By doing so, the secondary battery 8 backs up the memory 3 only at the warning level voltage Ewr or less. That is, the secondary battery 8 does not back up the memory 3 above the warning level voltage Ewr. Therefore, the larger the voltage difference between the main battery initial voltage E0 and the alarm level voltage Ewr, the lower the memory backup start voltage of the secondary battery 8 and the more unnecessary discharge of the secondary battery 8 can be avoided. Therefore, since the charging interval of the secondary battery can be extended, the number of times of charging the secondary battery can be suppressed, and the maintenance of the secondary battery due to the overcharge allowable number of the secondary battery is reduced.

  Although not shown, for example, the number of times the three-terminal regulator 93 is turned on is counted by a counting unit, and a charging number alarm unit that outputs an alarm when the counted number exceeds the charging limit number of the secondary battery. It is also possible to promote replacement based on the expected deterioration of the secondary battery. The counting means includes a counter that counts up the rising of the voltage at the input terminal 93i of the three-terminal regulator 93 or the output terminal 93o. The charging frequency alarm means compares the count value counted by the counting means with a preset secondary battery charge limit count, and the count value counted by the count means exceeds the secondary battery charge limit count. As a result, the LED or the like is turned on to notify the outside that the number of times of charging the secondary battery has reached the limit value.

  In the present embodiment, the secondary battery corresponds to the auxiliary battery, the alarm level voltage Ewr is the first threshold, the recharge voltage E2 is the second threshold (charging start threshold), and the regulator output voltage E1. Corresponds to the third threshold (charging end threshold).

  Further, the expression “beyond” includes the above meaning, and the expression “below” includes the following meaning.

DESCRIPTION OF SYMBOLS 1 Power supply circuit 2 Main battery 2a Main battery output voltage 3 Static RAM (SRAM)
3a SRAM terminal voltage 4 Warning generating circuit 5, 6, 7, diode 8 Secondary battery 8a Secondary battery output voltage 9 Secondary battery charging circuit 10 Battery unit 11 Auxiliary battery unit 12 Control unit 91 Comparator 92 Transistor 93 Three-terminal regulator ( regulator)
93i Regulator input terminal 93o Regulator output terminal 94 Diode 100 Base board 200 System power supply 300 CPU module R1-R4 Resistor Rf Feedback resistor Rs Charge current limiting resistor S1 Base board voltage Es Power supply voltage Ecpp Comparator (+) input terminal voltage Ecpo Comparator output voltage Ewr Warning level voltage E1 Regulator output voltage E2 Recharge voltage Eth Minimum voltage that can be backed up T (T1 to T14) PLC operation period τ (τ1 to τ14) PLC non-operation period

Claims (5)

A programmable controller having a data backup function,
Storage means for holding data;
A power supply for supplying current to the storage means;
A backup battery unit for supplying current to the storage means when the power supply is off;
An auxiliary battery unit that supplies current to the storage means instead of the backup battery unit when the output voltage of the backup battery unit is equal to or lower than a first threshold value for replacing the backup battery unit;
The auxiliary battery part is
A rechargeable auxiliary battery,
When the output voltage of the auxiliary battery falls below a second threshold value for charging the auxiliary battery, charging of the auxiliary battery is started, and the output voltage of the auxiliary battery ends charging of the auxiliary battery by the charging. Charging means for terminating charging of the auxiliary battery when a threshold is reached;
A programmable controller comprising: In the programmable controller according to claim 1,
The second threshold value is equal to or higher than a voltage value obtained by adding the falling voltage of the auxiliary battery to the reference voltage when the auxiliary battery backs up the storage means for a predetermined time with the minimum data retention voltage of the storage means as a reference voltage. A programmable controller characterized by being. The programmable controller according to claim 1 or 2,
The auxiliary battery unit is mounted on a programmable controller main body together with the storage means, and the battery unit is configured to be separable from the programmable controller main body. The programmable controller according to any one of claims 1 to 3,
The auxiliary battery unit further includes counting means for counting the number of times the auxiliary battery is charged,
The programmable controller further includes a charge number alarm unit that issues an alarm when the number of times of charging by the counting unit reaches a limit number of times that the auxiliary battery can be charged. The programmable controller according to any one of claims 1 to 4,
The programmable controller further comprises a voltage drop warning means for issuing a warning of a voltage drop of the backup battery unit when the output voltage of the backup battery unit becomes equal to or lower than the first threshold value.