JP2001306109A - Programmable controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a surge and, at the same time, minimize delay in response time, which is the most important for users of a programmable controller, thus providing a balanced surge suppression. SOLUTION: The programmable controller is provided with a plurality of delay circuits with different CR constants which make speed of voltage change given to a gate of a driving element to drive a load variable, detects the surge level and, when the surge level is lower than a predetermined value, selects, for connection, the delay circuit which has the CR constant with the least delay of output signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a programmable controller suitable for driving an inductive load that generates a large surge.

[0002]

2. Description of the Related Art A conventional system will be described below with reference to FIGS. FIG. 1 shows a circuit configuration example of an output circuit of a programmable controller and an example in which an inductive load such as a solenoid valve is connected to the output circuit. An output signal 1 for controlling a control target by a program controller from an arithmetic control unit (not shown) is applied to a photocoupler 2 which insulates the output signal and transmits the output signal to the outside. The output signal from the photocoupler 2 is amplified by a current and supplied to a transistor 3 for driving an external load ON / OFF. Transistor 3 drives an external load. Outside, an inductive load 4 to be driven and a power supply 5 for moving the inductive load 4 are connected.

FIG. 2 shows a time chart of a waveform A of an output signal 1 from the arithmetic control unit and a waveform B of a signal 6 for turning on / off an inductive load. As shown in the figure, when the signal 1 changes from OFF to ON, the inductive load operates from OFF to ON without any particular disturbance of the waveform.
When changing from N to OFF, when an inductive load is connected, back electromotive force is generated, and a large surge 7 is generated. This means that the greater the inductance of the inductive load, the greater the surge and the greater the noise.

[0004] Noise caused by this surge enters the inside of the programmable controller from the output terminal of the output circuit, and if the control circuit inside the programmable controller is in the worst case, it may malfunction. At this time, noise is reduced by the photocoupler 2, but is not sufficient. In addition, this noise is output to the outside or the power supply 5 of the load.
Entering or causing adverse effects.

As a countermeasure against this, conventionally, a surge killer 8 having a capacitor and a resistor connected in series is connected in parallel with the inductive load 4 to absorb and suppress the surge generated from the inductive load 4, or to provide a method for controlling the output section. There is known a method in which a diode is provided in an output terminal portion and surge is cut here.

However, as the inductance of the inductive load increases, the surge level and the energy increase, and the absorption and cutoff of the surge are limited in the conventional method. Intrusion cannot be suppressed and there is a possibility of malfunction.

Further, as described in Japanese Patent Application Laid-Open No. 6-291631, a resistor is selectively inserted into the gate of the driving element to change the resistance value, and the speed at which the gate voltage is increased or decreased is reduced, so that noise and surge are reduced. There is a method of suppressing the voltage. Although this method has an effect of suppressing a surge voltage, it has a characteristic that the response speed of a signal is reduced.

[0008]

In the conventional insertion of a surge killer, the surge generated due to ON / OFF driving of a relatively large inductive load cannot be suppressed, and its effect is not sufficient.

Various loads are connected to the programmable controller, and even if the loads are inductive loads, the magnitude of the inductance varies. On the other hand, it is not sufficient if the surge is suppressed, and it is the most important for the user of the programmable controller that the delay of the signal response speed (hereinafter simply referred to as delay) is as small as possible. In the above-described method of connecting a resistor to a drive element and changing the resistance, the balance with delay is not taken into account, and only reduction of surge is described. Further, depending on the use environment of the user of the programmable controller, the degree of noise suppression of the device, and the like, depending on the user, delay may be emphasized, or noise due to surge may be emphasized. The conventional technology cannot reflect such a user's design concept.

Accordingly, an object of the present invention is to provide a programmable controller that suppresses a surge generated from an inductive load while considering the balance with delay.

[0011]

A plurality of circuits having different CR constants for varying the rate of change of the voltage applied to the gate of a driving element for driving a load are provided. The circuit having the smallest CR constant with a certain value or less is selected and connected.
Further, information for designating a circuit having a CR constant in a control program of the programmable controller by a user can be incorporated.

[0012]

FIG. 4 illustrates the principle of the present invention. Conventionally, as shown in FIG.
When it changed to F, surge 7 was occurring. This is generated by the principle of the back electromotive force of the inductive load.
The higher the switching speed, the higher the surge level. Therefore, if the speed of switching from ON to OFF is gradually reduced (in the example of FIG. 4, SW-1 of A →→
SW-4), the surge level is reduced as shown by the waveform B in FIG.

The present invention detects the surge level generated in the load, and switches and automatically adjusts the switches SW-1 to SW-4 so that the surge is not more than the surge detection level 50 shown in FIG. 4B. Things. It is also possible for the user to designate one of the SWs by a control program of the programmable controller based on the design concept of the user.

An embodiment utilizing this principle will be described below. FIG. 3 shows an embodiment of the present invention. In the figure, the arithmetic control unit 100 includes a general program for control, a control program including a program for designating a switch in the present embodiment, an output IC 9, and a SWIC switching control unit 19 described in detail later. Calculation result 21 of calculation control unit 100
Is output to the output port 22 of the output IC 9
Is output to This output signal 10 is applied to output circuit 200 and output to the outside. Although not shown, the programmable controller also has an input circuit,
An operation is performed by the control program together with information obtained from the output target. Further, the designation of the switch in the present embodiment can be input from the input circuit.

Next, the output circuit 200 will be described in detail.
The switch function built-in IC 12 receives the output signal 10 which is a calculation output output from the port 22 of the output IC 9 as an input,
The output signal 10 is switched to one of a plurality of (four in this embodiment) terminals according to a control signal provided from the port 23 of the output IC. Four is an example, and if more precise control is desired, the number may be increased. These terminals are connected to four types of resistors 13 (R
1 to R4 and R1 have the lowest resistance value, and R4 has the highest resistance value). The other end of the resistor 13 is commonly connected to a capacitor 15, and the resistor 13 and the capacitor 15 form an output delay circuit. FET1
Reference numeral 4 functions to convert the voltage of the capacitor 15 into a current. On the other hand, when the output signal 10 switches from OFF to ON, the signal passes through the diode 11 and has almost no resistance, and is supplied to the FET 14 with no delay time. The FET 14 is further connected to the photocoupler 2, and the output of the photocoupler 2 is applied to the gate of the output transistor 3 as in the prior art, and the output transistor 3
Controls ON / OFF of the external load 4.

In this embodiment, the surge voltage is
4 and the surge peak hold signal 16 is obtained by the capacitor 25. The surge peak hold signal 16 is compared with the voltage of the comparator 17, that is, the voltage corresponding to the surge detection level 50 in FIG. 4, and is “1” when the surge peak hold signal 16 is higher than the surge detection level 50 and “0” when the surge peak hold signal 16 is lower. Is output. The comparator output signal 18 is input to the SWIC switching control unit 19. The output of the SWIC switching controller 19 is provided to the port 23 of the output IC 9.

Next, the operation when the output signal 10 changes from ON to OFF will be described. In the initial state when the load 4 is connected to the programmable controller, the output signal 1 is switched to the terminal R1 having the lowest resistance value in the IC 12 with a built-in switching function. At this time, how large the surge is depends on the inductance of the inductive load to be controlled. According to the surge level at this time, the SWIC switching control unit 19 according to the above-described configuration is used.
Is determined. if,
If this is "0", the surge level is already lower than the surge detection level 50 and has no adverse effect, so that the switching state of the IC 12 with built-in switch function is maintained. The value of the comparator output signal is "1"
If this is the case, it indicates that the surge level exceeds the surge detection level 50, and the SWIC switching control unit 19 sends the switch function built-in IC 1 through the port 23 of the output IC 9.
Then, switching is made to R2 having the second highest resistance value. In this way, the rate of change of the output signal 10 becomes slower, so that the surge level is reduced. In the same manner, the IC 12 with the switch function is caused to switch to a terminal having a higher resistance value until the value of the comparator output signal 18 becomes “0”. When detecting that this signal is “0”,
Switching by the switch function built-in IC 12 is not changed, but is fixed and maintained. With the above operation, control can be performed so that the surge generated in the load becomes equal to or less than the reference value and the delay of the output signal is minimized.

The above is the control of the surge level by the automatic control. Hereinafter, another embodiment using the same output signal delay circuit and switching circuit as the above embodiment will be described.

The importance of the surge level or the importance of the switching speed of the output signal differs depending on the user. When importance is attached to the surge level, there are a case where the device is used in an environment where a device which is sensitive to noise is nearby and a case where a surge killer or the like is not used. Further, when importance is attached to the switching speed of the output signal, there are a case where a control target device which requires strict responsiveness is used and a case where the device is used in an environment where noise countermeasures are less necessary.

A switch function built-in I in the control program
A part for designating switching in C by a user is provided.
This is represented by reference numeral 20. Here, when a certain switching (for example, connection to the terminal 2 connected to R2) is specified, this is given to the port 23 of the output IC, and the specified switching is performed in the switch function built-in IC 12. In the above embodiment, four terminals are selected by two ladder circuits, but one terminal may correspond to one ladder circuit. In the port 23, when the switching is specified from the control program, the switching is specified by the SWIC switching control unit 19.
Give priority to the signal from In the above embodiment, it is possible to realize the delay of the output signal and the magnitude of the surge level which meet the user's request.

[0021]

According to the present invention, it is possible to realize a programmable controller capable of suppressing a surge generated from an inductive load connected to the output of the programmable controller with an appropriate delay of the output signal.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a conventional technique.

FIG. 2 is a timing chart of a conventional circuit.

FIG. 3 is a diagram showing a configuration example of an embodiment of the present invention.

FIG. 4 is a timing chart of the present invention.

[Explanation of symbols]

 1. Output signal 2. 2. Insulating element (photocoupler) 3. Output transistor Inductive load 5. Power supply for load drive 6. 6. Inductive load ON / OFF signal 7. Surge waveform Surge killer 9. Output IC 10. Output IC output signal 11. Diode 12. 12. IC with built-in switch function 13. Resistors (R1 to R4) FET transistor 15. Capacitor 16. Surge peak hold signal 17. 17. Comparator (comparator IC) Comparator output signal 19. SWIC switching control section 20. 50. Output coil in control program Surge detection reference level

Claims (4)

[Claims] An arithmetic control unit for issuing an output signal for controlling a device to be controlled;
An output delay circuit including an element connected to the terminal, an element connected to the terminal for delaying a change speed of the plurality of output signals having different values, and a device to be controlled by the output delay circuit. A load control circuit for controlling the load, a determination circuit for monitoring the surge and determining whether the surge level is within a predetermined range, and receiving the output of the determination circuit so that the surge level falls within a predetermined range. And a switch control circuit for controlling switching of the switching of the switch circuit. 2. The switch control circuit according to claim 1, wherein a surge level of the switch circuit falls within the predetermined range.
2. The programmable controller according to claim 1, wherein control is performed so as to switch to a terminal that minimizes a change speed of the output signal. 3. The output control circuit according to claim 1, wherein the output control circuit includes a resistor having one end connected to each of the terminals of the switch circuit and the other end connected to a capacitor and having different resistance values. Programmable controller. 4. An operation control unit for issuing an output signal for controlling a device to be controlled, and an output control unit for transmitting the output signal to one of a plurality of terminals.
An output delay circuit including an element connected to the terminal, an element connected to the terminal for delaying a change speed of the plurality of output signals having different values, and a device to be controlled by the output delay circuit. A load control circuit for controlling the load of the switch circuit, and a control program in the arithmetic control unit for specifying a terminal to which the switch circuit is connected.