JP2012027640A - Programmable controller and method for detecting programmable controller memory backup battery voltage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a voltage drop of a battery before the battery becomes completely exhausted and urge a user to replace the battery, so as not to cause a battery backup operation for a programmable controller memory to be interrupted due to battery exhaustion.SOLUTION: A backup circuit comprises: a backup continuation means for continuing backup using a battery for a predetermined period after a main power supply is turned on; and a battery voltage detection means for detecting a battery voltage during the continuation period, comparing it with a predetermined threshold value, and outputting the comparison result.

Description

The present invention relates to a backup method for protecting memory data in a programmable controller (hereinafter also abbreviated as PLC).
In the following drawings, the same reference numerals denote the same or corresponding parts.

  FIG. 3 is a block diagram of a conventional memory backup circuit. In the figure, reference numeral 1 denotes a module power source that generates a module voltage S2. Reference numeral 2 denotes a volatile memory that holds data. When the module power supply 1 is in an off state, a voltage is supplied by a battery 5 described later to back up the data. Reference numeral 2 a denotes a voltage (memory power supply voltage) supplied to the memory 2.

  Reference numeral 5 denotes a battery for backing up the memory 2 and outputs 5a as its output voltage. A battery voltage detection circuit 6 monitors the output voltage (battery voltage 5a) of the battery 5. The battery voltage detection circuit 6 monitors the battery voltage 5a with the lower limit voltage necessary for backing up the memory 2 as the threshold voltage Eth, and outputs the battery voltage detection circuit output 6a when the battery voltage 5a becomes lower than the threshold voltage Eth. The display circuit 7 receives the battery voltage detection circuit output 6a, outputs the display circuit output 7a, issues a warning, and prompts the user to replace the battery.

Reference numeral 8 denotes a reset cancellation circuit that monitors the voltage of the module voltage S2, and outputs a reset cancellation signal 8a when the module voltage S2 reaches a predetermined voltage.
Here, the characteristics of the battery will be described. The battery can be regarded as a series connection of an electromotive force source that outputs a substantially constant electromotive force and an internal impedance. Although this electromotive force decreases very little as the battery is consumed, it does not change so much, and reaches the end of the battery life and rapidly decreases. On the other hand, the internal impedance has a property of gradually increasing following the degree of consumption of the battery and increasing more rapidly when reaching the end of the battery life.

  FIG. 4 is a time chart for explaining the operation of the circuit of FIG. The module voltage S2, battery voltage 5a, memory power supply voltage 2a, reset release signal 8a, battery voltage detection circuit output 6a, and display circuit output are arranged in the order of array numbers 1), 2). 7a.

  The operation of the circuit of FIG. 3 will be described with reference to FIG. In FIG. 4, E0 is the output voltage (no-load voltage) of the battery 5 when the module voltage S2 is on. At this time, since the voltage to the memory 2 is supplied from the module voltage S2, the battery 5 is in an unloaded state when viewed from the battery 5, and E0 is a voltage corresponding to the electromotive force of the battery 5 described above.

  E1 is the output voltage of the battery 5 when the battery 5 backs up the memory 2 (sections t0 to t1). That is, E1 is the output voltage (actual load voltage) of the battery 5 in a state where the module voltage S2 is off and the battery 5 is loaded.

  When the external power supply (not shown) is cut off at time t0, the module voltage S2 is turned off. For this reason, the diode 4 is forward biased (ON), the diode 3 is reverse biased (OFF), and the backup battery 5 starts energization to the memory 2, that is, memory backup. At this time, the diode 3 prevents the current of the battery 5 from flowing through the line of the module voltage S2. Thus, the battery voltage 5a shifts from the no-load voltage E0 to the actual load voltage E1 when the module voltage S2 is turned off.

  When the external power supply is turned on at time t1, the module voltage S2 is turned on. When the module voltage S2 is turned on, the voltage S2 is set higher than the voltage 5a of the battery 5, so that the diode 3 is forward biased (on) and the diode 4 is reverse biased (off). Power is supplied from the voltage S2 line. For this reason, the backup battery 5 is disconnected from the module voltage S2 line and the memory 2 side. Thus, when the module voltage S2 is turned on, the battery voltage 5a shifts from the actual load voltage E1 to the no-load voltage E0.

  At time t1, the reset release circuit 8 turns on the reset release signal 8a when the module voltage S2 reaches a predetermined voltage. The reset release signal 8a that is turned on is supplied to the battery voltage detection circuit 6. The battery voltage detection circuit 6 detects the battery voltage 5a after a predetermined time has elapsed from the rising timing of the reset release signal 8a. That is, the reset release signal 8a is output at the timing of t1, and the battery voltage 5a is detected at the timing of tc after a predetermined time has elapsed since then.

  The battery voltage detection circuit 6 compares the battery voltage 5a with the threshold voltage Eth at the timing tc. If the battery voltage 5a is less than the threshold voltage Eth, the battery voltage detection circuit output 6a indicated by the broken line is given to the display circuit 7 to output the display circuit output 7a (broken line) from the display circuit 7, and the battery voltage 5a is the threshold voltage. If it is equal to or higher than Eth, the battery voltage detection circuit output 6a and the display circuit output 7a are not output as indicated by the solid line. The threshold voltage Eth is defined as a value that does not fall below the lower limit voltage for backing up the memory 2. Specifically, when the lower limit voltage for backing up the memory 2 is 1V, it is desirable not to fall below the voltage obtained by adding the forward voltage of the diode 4 to 1V.

  In such a conventional example, the module power supply 1 is turned on, the supply voltage to the memory 2 is supplied from the module power supply 1 side, and the voltage of the backup battery 5 is detected thereafter. That is, the above-described conventional example does not detect the voltage (actual load voltage E1) when the backup battery backs up the memory 2, but detects the voltage when the battery 5 is in a no-load state. Therefore, the actual load voltage E1 when the memory 2 is backed up cannot be detected accurately.

  If the battery voltage is detected and the alarm is output in such a no-load state as described above, the battery is consumed significantly, and the battery voltage when the memory is loaded on this battery, that is, the actual load Naturally, the voltage E1 is lower than the threshold voltage Eth, and there is a high possibility that the battery has already been in a state where the memory cannot be backed up. Therefore, in the conventional battery voltage detection method described above, there is a high possibility that an alarm will not be output in spite of running out of the battery, or the output of the alarm will be delayed and the battery will not be replaced in time, and the battery will run out.

  In order to solve such a problem, the CPU temporarily switches the power supply line of the memory from the main power supply side to the battery side, creates an actual load state of the battery, and detects the battery voltage at that time. A battery backup circuit is disclosed (for example, Patent Document 1).

JP-A-2-12316

  However, since the battery has a characteristic of outputting a voltage higher than the voltage immediately before the interruption for a while when the continuous use state is temporarily interrupted and restarted, the backup battery that was in the memory backup state is put into a no-load state. When the load is applied again in the backup state, the battery voltage 5a slightly approaches the actual load voltage E1 from the no-load voltage E0, but for a while until reaching the stable true actual load voltage E1 (decrease). It takes a long time.

  For this reason, in the invention described in Patent Document 1, the battery voltage slightly higher than the stable true actual load voltage E1 is measured, and the measured battery life is actually almost exhausted when there is still life expectancy. There is a possibility that the detection of battery consumption will be delayed and the battery will run out. Furthermore, since the invention described in Patent Document 1 temporarily switches from the normal read / write operation state when the main power is turned on to the battery backup state, the entire apparatus or a part of the functions must be interrupted.

  The present invention solves such a conventional problem, and an object of the present invention is to accurately detect a voltage drop of the battery before the battery is completely consumed and to prompt the user to replace the battery. It is an object of the present invention to provide a memory backup battery voltage detection method capable of preventing a backup operation from being interrupted by battery consumption.

As a method for solving the above problems, the present invention is configured as follows.
The invention according to claim 1 is a programmable controller having a backup circuit that backs up the storage means with a battery when the main power is off. The backup circuit continues to back up with the battery for a predetermined period after the main power is turned on. Backup continuation means, and a battery voltage detection means for comparing the voltage of the battery with a predetermined threshold value during a predetermined period and outputting the comparison result.

The invention according to claim 2 is the programmable controller according to claim 1,
The predetermined threshold is a voltage value set in advance based on a lower limit voltage necessary for the storage means to hold data.

The invention according to claim 3 is the programmable controller according to claim 1,
The storage means is configured to hold setting data for determining the operation mode of the programmable controller.

The invention according to claim 4 is the programmable controller according to claim 1,
When a new threshold value is transferred to the threshold value by a support device that can be attached to and detached from the programmable controller, the threshold value is further provided with an updating unit that updates the preset threshold value to the new threshold value.

The invention according to claim 5 is a battery voltage detection method of a programmable controller having a backup circuit that backs up the storage means with a battery when the main power is off.
The backup by the battery is continued until the first timing generated after elapse of a predetermined time from the start of the main power supply, and the second generated during the predetermined time from the start of the main power supply. The battery voltage is detected at the timing.

  According to the present invention, the memory backup state by the battery is continued for a while after the external power source to the programmable controller is turned on, and the battery voltage in this state is detected. It becomes possible to accurately detect the battery voltage (actual load voltage E1), and it is possible to prevent the memory backup battery from running out, that is, data loss in the memory.

1 is a circuit diagram showing a configuration of a memory backup circuit as one embodiment of the present invention. Time chart for explaining the operation of FIG. Circuit diagram showing a configuration example of a conventional memory backup circuit Time chart for explaining the operation of FIG. The figure explaining the supply method of the power supply of a programmable controller (PLC)

Hereinafter, a preferred embodiment of the present invention will be described based on the drawings of FIGS. 1, 2, and 5. These drawings are for explaining one embodiment of the present invention, and the present invention is not limited by these drawings. Also, the same components as those in FIGS. 3 and 4 for explaining the prior art are denoted by the same reference numerals.

  An apparatus to which the memory backup circuit of the present invention is applied is a programmable controller (hereinafter referred to as PLC). The PLC is a device that monitors and controls a device to be monitored and controlled connected to the PLC by calculating and executing an application program, and is widely used in factory automation (FA) and the like.

  FIG. 5 is a diagram showing an example of the configuration of various modules, which are basic functional parts of the PLC, and an example of a power feeding method for each module. A system power supply 200 supplies a predetermined voltage to various modules when commercial power is supplied from the outside.

  Reference numerals 301 and 302 denote CPU modules (common code is 300) that performs overall control of the entire PLC. 401, 402,..., 406 are inputs / outputs for inputting signals such as switches and sensors attached at appropriate positions of various types of monitoring control target devices and for outputting control output signals to actuators of the monitoring control target devices. A module (common reference numeral is 400), and 100 is 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. Each of the modules 300 and 400 that has received this voltage S1 generates a module voltage S2 for driving a circuit in the module by a module power supply 1 provided in each module.

  FIG. 1 is a configuration diagram of the memory backup circuit 01 of the present invention provided in the CPU module 300. 3 differs from the conventional configuration example of FIG. 3 in that a control unit 9, a delay circuit 10, and a transistor 11 are added.

  In FIG. 1, the control unit 9 is equipped with a microprocessor (CPU), a program memory, a working memory, etc., not shown, and an external device is connected via the input / output module 400 by executing the application program described above. Control.

  The transistor 11 is inserted in series in a line from the module voltage S2 to the anode of the diode 3, and serves as a switch that opens and closes a power supply path to the memory 2 for the module voltage S2. The memory 2 holds parameters (setting data) for determining the operation mode of the PLC.

  The delay circuit 10 is connected to the line of the module voltage S2, and has a role of keeping the transistor 11 off for a predetermined delay period δ after the module voltage S2 is turned on. Reference numeral 10a denotes a delay circuit output signal as an on / off drive signal which the delay circuit 10 gives to the base of the transistor 11. As described above, the delay circuit 10 and the transistor 11 allow the memory backup circuit 01 to continue the battery backup for a predetermined period after the module voltage S2 is turned on (backup continuation means).

  The reset release circuit 8 and the battery voltage detection circuit 6 are substantially the same as those shown in FIG. 3 except that the reset release signal 8a is supplied to the control unit 9 in addition to the battery voltage detection circuit 6. The output signal battery voltage detection circuit output 6 a is provided to the control unit 9 in addition to the display circuit 7.

  1 is the same as the module power supply 1 shown in FIG. 3 in that the module voltage S2 is generated, and the memory 2, the battery 5, and the display circuit 7 are the same as those in FIG.

  FIG. 2 is a time chart for explaining the operation of FIG. In FIG. 2, in addition to the various signals shown in FIG. 4, the output signal of the delay circuit 10 is added, and in order of array numbers 1), 2),. A module voltage S2, a battery voltage 5a, a memory power supply voltage 2a, a reset release signal 8a, a delay circuit output signal 10a, a battery voltage detection circuit output 6a, and a display circuit output 7a are shown. In FIG. 2, the time axis (horizontal axis) is enlarged from FIG.

Next, a specific operation of the memory backup circuit 01 of FIG. 1 will be described with reference to FIG.
Before time t1, the external power supply to the PLC is cut off, and the module voltage S2 is off. At this time, the memory 2 is backed up by the battery 5. For this reason, the battery voltage 5a at the time point t1 is a stable actual load voltage E1.

  When the external power supply to the PLC is turned on at time t1, the module voltage S2 rises and is turned on. At the beginning of this rise, the reset release circuit 8 is connected to the module as in the prior art described in FIGS. It is detected that the voltage S2 has reached a predetermined voltage, and the reset release signal 8a is turned on. When the reset release signal 8a is turned on, the reset of the control unit 9 is released and the operation is started. The reset release signal 8a is also supplied to the battery voltage detection circuit 6, and the battery voltage detection circuit 6 detects the battery voltage 5a after a predetermined time has elapsed from the rising timing of the reset release signal 8a.

  The delay circuit 10 prevents the transistor 11 from being turned on for a predetermined time after the module voltage S2 reaches a predetermined voltage. Therefore, even after the module voltage S2 is turned on, the delay circuit output signal 10a applied to the base of the transistor 11 is kept at the low level from the rising start time t1 to the time t2 when the delay period δ elapses, and the transistor 11 is turned off. keep. For this reason, the battery 5 continues to back up the memory 2 as it is until time t2, and the battery voltage 5a maintains the actual load voltage E1.

  Subsequently, at time t2, the delay circuit 10 sets the delay circuit output signal 10a to the high level, and turns on the transistor 11. As a result, the memory 2 is supplied with a voltage from the module voltage S2 side instead of the battery 5, the battery 5 is disconnected from the memory 2, and the battery voltage 5a shifts from the actual load voltage E1 to the no-load voltage E0. To do.

  By the way, at the time tc (battery voltage detection point) before the delay period δ elapses from the time t1, the battery voltage detection circuit 6 detects the battery voltage 5a and compares it with the threshold voltage Eth. This is achieved by turning on the reset release signal 8a by the reset release circuit 8 when the module voltage S2 reaches the predetermined voltage, and detecting the battery voltage 5a after a predetermined time has elapsed from this rising timing. That is, the reset release signal 8a is output at the timing of t1, and the battery voltage 5a is compared with the threshold voltage Eth at the timing of tc after a lapse of a predetermined time after counting.

  If the battery voltage 5a (actual load voltage E1) is less than the threshold voltage Eth at the timing tc, the battery voltage detection circuit output 6a is output, and the display circuit 7 receiving this output outputs the display circuit output 6a to give an alarm. To prompt the user to replace the battery. The threshold voltage Eth is a voltage determined from the lower limit voltage necessary for the backup of the memory 2 as described above. Specifically, when the lower limit voltage for backing up the memory 2 is 1V, it is desirable that the voltage be equal to or higher than the voltage obtained by adding the forward voltage of the diode 4 to 1V.

  The threshold voltage Eth can be updated by the control unit 9. When the control unit 9 receives a request for updating the threshold voltage Eth from a programming device (supporting device) that can be attached to and detached from the CPU module 300, the control unit 9 has a function of updating to a new threshold value received simultaneously with the request for updating. (Update means). The battery voltage detection circuit 6 is provided with a D / A conversion function for converting a digital value set by the control unit 9 into a predetermined voltage value, and this D / A converted output voltage is used as a threshold voltage Eth.

  Here, the time points t1, tc, and t2 are defined and the correlation between the respective time points is described. t1 is the time when the module power supply S2 is turned on as described above, that is, the time when the module power supply S2 reaches a predetermined voltage (a voltage at which the control unit 9 can operate). Further, tc is a timing at which the battery voltage 5a is detected after a predetermined time has elapsed with reference to t1. T2 is a timing at which the voltage supply to the memory 2 is switched after a predetermined time has elapsed with reference to t1. That is, t2 is a timing at which the voltage supply of the memory in the backup state by the battery 5 is switched to the supply of the module voltage S2.

  The relationship between tc and t2 is that the reference is t1 and tc <t2. That is, the point of the present invention is to create the timing of tc within the period from t1 to t2 and detect the battery voltage 5a.

  Further, the function of the battery voltage detection circuit 6 and the display circuit 7, that is, while the backup of the memory 2 by the battery is continued after the main power is turned on, the voltage of the battery 5 is compared with the threshold value Eth, The function of outputting the comparison result corresponds to the battery voltage detection means.

  As described above, the present invention maintains the backup state of the memory 2 by extending the time after the main power supply is turned on until the voltage supply from the battery to the memory is switched to the voltage supply by the main power supply. The battery voltage (actual load voltage) was detected. In this way, since the actual load voltage of the battery is accurately detected, a backup circuit and a highly reliable programmable controller are provided that can surely prompt the user to replace the battery before the memory backup capability of the battery 5 is exhausted. be able to.

01 Memory backup circuit 1 Module power supply 2 Memory 2a Memory power supply voltage 3, 4 Diode 5 Battery 5a Battery voltage 6 Battery voltage detection circuit 6a Battery voltage detection circuit output 7 Display circuit 7a Display circuit output 8 Reset release circuit 8a Reset release signal 9 Control Part 10 Delay circuit 10a Delay circuit output signal 11 Transistor S1 Base board voltage S2 Module voltage Eth Threshold voltage

Claims (5)

In a programmable controller having a backup circuit that backs up the storage means with a battery when the main power is off,
The backup circuit is
Backup continuation means for continuing backup by the battery for a predetermined period after the main power is turned on;
A programmable controller comprising: battery voltage detection means for comparing the voltage of the battery with a predetermined threshold value during the predetermined period and outputting the comparison result. The programmable controller according to claim 1,
The programmable controller, wherein the predetermined threshold is a voltage value set in advance based on a lower limit voltage necessary for the storage means to hold data. The programmable controller according to claim 1,
A programmable controller characterized in that the storage means stores setting data for determining an operation mode of the programmable controller. The programmable controller according to claim 1,
The programmable controller further comprising updating means for updating the preset threshold value to a new threshold value when a new threshold value is transferred by a support device attachable to and detachable from the programmable controller. A method for detecting the battery voltage of a programmable controller having a backup circuit that backs up storage means with a battery when the main power is off,
Continue the backup by the battery until the first timing generated after a lapse of a predetermined time from the fact that the main power is turned on,
A battery voltage detection method comprising: detecting a voltage of the battery at a second timing generated during the predetermined time starting from the main power source being turned on.