JP2007181034A - Input circuit of controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably provide an ON signal to a controller even when variation of ON current of a photo coupler is large. <P>SOLUTION: A transistor Tr1 performs switching so as to energize input of the photo coupler 4 on condition that it is assumed that input current Ia to the photo coupler 4 exceeds predetermined fourth current exceeding an upper limit value of the ON current of the photo coupler 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an input circuit of a control device in which a photocoupler is provided on the output side.

2. Description of the Related Art Conventionally, as an input circuit provided at the input of a control device, there is one that uses a circuit configuration in which a photocoupler is provided on the output side and the primary side and the secondary side are insulated (for example, Patent Document 1). reference). According to the configuration described in Patent Document 1, an input current of the photocoupler is converted and an output signal is given from the photocoupler to the control device.
JP-A-8-292806

  Recently, for example, a control device such as a programmable controller has a demand for high-speed response, and it has become necessary to change the photocoupler to an element capable of high-speed response as compared with the related art. If the photocoupler is changed to an element capable of high-speed response, a large difference occurs in the operation level of the input current among many photocouplers, and the input current value (on-current) varies when the output of the photocoupler is turned on. Tend to be larger. At this time, for example, even if the circuit configuration disclosed in Patent Document 1 is applied, variation in on-current cannot be reduced, and an on-signal cannot be stably given to the control device.

  Further, for example, in the case of a control device such as a programmable controller, it is generally necessary that the voltage-current characteristics of the input circuit satisfy the provisions of a predetermined standard. In this case, it has been confirmed that even if the circuit configuration disclosed in Patent Document 1 is applied, an output signal cannot be properly given to the control device.

  The present invention has been made in view of the above circumstances, and a first object of the present invention is to stably provide an ON signal to a control device even when there is a large variation in the ON current of a photocoupler. A second object of the present invention is to provide an input circuit for a control device that can properly supply an on / off signal to the control device.

  The first aspect of the present invention is directed to a photocoupler provided on the output side that outputs an ON signal to a control device when the input current level of the photocoupler exceeds a predetermined level set to exceed the operation level. It is a thing. According to this configuration, the photocoupler is switched to be energized on the condition that the input current of the photocoupler exceeds a predetermined level. On the other hand, an ON signal can be stably given.

  The invention described in claim 2 is directed to an input circuit of a control device in which a photocoupler is provided on the output side and an on / off signal is output to the control device in accordance with the level of the input current of the photocoupler. The first input voltage current region is defined as the operation region of the input voltage current with respect to the input circuit body that is defined so that the output of the input circuit body is turned on, and the input circuit body outputs the second input voltage current region. It is defined as the operating region of the input voltage and current for the input circuit body that is defined to be off. In this case, the switching circuit is an input voltage current in the third input voltage current region in which the input voltage current applied to the input circuit body is defined to be indefinitely output between the first and second input voltage current regions. On condition that there is, the input current to the photocoupler is switched on and off.

  For this reason, when the input voltage current applied to the input circuit satisfies the condition of the third input voltage current region, the switching circuit switches on the input current to the photocoupler. In this case, when a current is stably supplied to the input of the photocoupler and a voltage current defined in the first input voltage current region is applied to the input circuit, the photocoupler outputs an on signal as an output signal. Will be output as. Therefore, the output of the input circuit is properly guaranteed to be on.

  On the contrary, when the input voltage / current applied to the input circuit satisfies the condition of the third input voltage / current region and the switching circuit switches off the input to the photocoupler, the input side of the photocoupler No current is supplied. In this case, the photocoupler always outputs an off signal as an output signal. Therefore, the output of the input circuit is properly guaranteed to be off. As a result, an on / off output signal can be given to the control device appropriately.

  According to the third aspect of the present invention, when the switching circuit switches the input current to the photocoupler, even if the current flowing through the photocoupler increases, for example, the current flowing through the resistor element increases, Even if the heat generation amount increases, the current suppression circuit suppresses the input current to the photocoupler, so that the heat generation amount of the product can be suppressed as compared with the conventional case.

  According to the fourth aspect of the invention, the voltage detection circuit detects the voltage on the input side of the photocoupler, and the switching circuit switches on / off energization of the input current to the photocoupler according to the detection voltage of the voltage detection circuit. Therefore, it is possible to switch the energization of the photocoupler in accordance with the detection voltage of the voltage detection circuit, and it is possible to configure the circuit according to the above-described invention simply by providing a configuration for detecting the voltage on the input side. It can be configured with a circuit. At this time, it is desirable that the voltage detection circuit is configured to detect the input terminal side voltage of the input circuit, as in the fifth aspect of the invention. In this case, the voltage between the input terminals can be accurately measured, and a simpler circuit can be configured.

  As in the sixth aspect of the present invention, it is desirable that a current suppression circuit be provided between the voltage detection circuit and the switching circuit. According to such a configuration, a more practical circuit can be configured.

Hereinafter, an embodiment in which a control device of the present invention is applied to a programmable controller will be described with reference to FIGS. 1 and 2.
FIG. 1 is a detailed electrical configuration diagram showing an example of a control device and its input circuit. FIG. 3 is a schematic block diagram showing the electrical configuration of the programmable controller.

  As shown in FIG. 1, a programmable controller (hereinafter referred to as a PC) 1 includes an input circuit main body 2 and a PC main body 3 as a control device. As shown in FIG. 3, the PC main body 3 includes a logical operation unit 9 to which an output signal of the input circuit 2 is given, an output circuit 8 as an output interface for outputting a logical operation result of the logical operation unit 9, And a communication unit 7 for communicating a logical operation result of the logical operation unit 9 to the outside.

  A photocoupler 4 is provided on the output side of the input circuit 2. The photocoupler 4 includes a photodiode on the input side and a phototransistor on the output side.

  A logical operation unit 9 is incorporated in the PC main body 3, and a predetermined logical operation is performed by the logical operation unit 9. In recent years, high-speed input is required for the PC body 3, and it is necessary to use a high-speed photocoupler 4 on the output side of the input circuit 2. Specifically, the period of the pulse signal applied to the input terminals IN and COM of the input circuit 2 has been shortened to several μs to several tens μs, compared to several hundred μs to several ms. .

  The high-speed photocoupler 4 has a large variation in on-current compared to the low-speed photocoupler. For example, in a certain device, a low-speed photocoupler has an on-current variation of about 0.1 to 1.5 mA, whereas a high-speed photocoupler 4 has an on-current variation of about 0.1 to 5 mA. is there. Therefore, it is necessary to configure the photocoupler 4 for high speed so that it can be used stably and properly, and the circuit configuration shown in FIG. 1 is adopted.

  As shown in FIG. 1, resistors R1 and R2 and a diode D1 are connected in series between the input terminals IN and COM of the input circuit 2, and a closed loop is configured on the input side of the input circuit 2.

  The resistors R1 and R2 are configured as a voltage dividing circuit 5 (corresponding to a voltage detection circuit) that divides the voltage applied to the input terminals IN and COM. The divided voltage V1 of the voltage dividing circuit 5 is an NPN transistor. It is given to the base of Tr1. The transistor Tr <b> 1 is provided in a current-carrying path between the collector and the emitter that communicates with the diode on the input side of the photocoupler 4. Between the voltage dividing circuit 5 and the photocoupler 4, a current suppressing circuit 6 and a harmonic noise removing capacitor C1 are provided for the energization path. The output of the photocoupler 4 is input to the PC main body 3 via the pull-up resistor R6.

  The current suppression circuit 6 is configured, for example, by connecting a resistor R5 in series to the output side of the constant voltage circuit 6a. The constant voltage circuit 6a is configured by connecting an NPN transistor Tr2, a resistor R4, and a constant voltage diode D2 in the illustrated form. A resistor R3 is connected in parallel to the input side of the photocoupler 4.

  By the way, a predetermined standard is defined for the PC 1. FIG. 2 schematically shows the input voltage and input current characteristics of this standard. A pulse signal is given to the input terminals IN and COM. This pulse signal is a signal having a period of about several μs to tens of μs, and its amplitude also varies. At this time, the standard is determined so that the output of the input circuit body 2 is turned on when the input voltage / current characteristic is in the region X1 in FIG. 2, and the input voltage / current characteristic is in the region X2 in FIG. The standard is set so that the output is turned off.

  The region X2 corresponds to the second input voltage current region of the present invention, and the region is, for example, an input voltage of 0 V or more and a predetermined first voltage V1 or less, and an input current of 0 A or more and a predetermined first voltage. An input voltage current region that satisfies a condition of 5 current I5 or less, or an input voltage that satisfies a condition of an input voltage of 0 V or more and a predetermined second voltage V2 or less, and an input current of 0 A or more and a predetermined second current I2 or less. It is a current region. When a voltage / current characteristic signal in the region X2 is given, the output of the input circuit body 2 must be turned off before being output. In FIG. 2, there is a relationship of the first voltage V1 <the second voltage V2, and the first current I1 <the second current I2 <the third current I3 <the fourth current I4 <the fifth current I5.

  The region X1 corresponds to the first input voltage current region of the present invention, and the region has, for example, an input voltage that is equal to or higher than the predetermined second voltage V2 and equal to or lower than the predetermined third voltage V3, and the input current. Is an input voltage current region that satisfies the condition of the predetermined third current I3 or more and the predetermined fifth current I5 or less. When a voltage-current characteristic signal in this region X1 is given, the output of the input circuit body 2 must be turned on for output.

  A region X3, which is an input voltage current region provided between these regions X1 and X2, is defined as a region where indefinite output is possible, and on-off output is possible according to the standard. Specifically, the region X3 is an input voltage that exceeds the predetermined first voltage V1 and that is less than the predetermined second voltage V2, a current that exceeds the predetermined second current I2, and a predetermined fifth current I5. This is an input voltage current region that satisfies the following input current conditions. When a signal having a voltage-current characteristic in the region X3 is given, the output of the input circuit body 2 is not necessarily defined as on or off.

  Under such conditions, it is necessary to make a design that can withstand variations in mass production. Therefore, in the present embodiment, an embodiment that can satisfy the standard under such conditions will be described.

The operation of the above configuration will be described.
As described above, pulse signals are input to the input terminals IN and COM. This pulse signal is a signal having a period of about several μs to several tens of μs, and its amplitude also varies. Therefore, in this embodiment, the on / off characteristics when the input voltage current fluctuates transiently will be described. Characteristics A1 to A3 shown in FIG. 2 indicate characteristics according to the present embodiment, and characteristic B indicates characteristics according to the related art.

  When the input voltage Vin and the input current Iin are both 0 V and 0 A, the current Ia does not flow to the input side of the photocoupler 4, so the output of the photocoupler 4 is turned off. In this case, the above-mentioned standard is satisfied. When the input voltage Vin and the input current Iin are gradually increased, the applied voltage and current to the node N1 are also gradually increased. Then, although the capacitor C1 is charged, the current Ia does not flow to the input side of the photocoupler 4 while the transistor Tr1 is off.

  When the input voltage Vin and the input current Iin further increase and the divided voltage V1 of the voltage dividing circuit 5 becomes the base-emitter voltage of the transistor Tr1, the transistor Tr1 transitions from the off state to the on state. At this time, the setting state of each circuit element of the input circuit body 2 when shifting to the ON state is such that the current Ia flowing on the input side of the photocoupler 4 is equal to or greater than a predetermined fourth current I4. desirable. The predetermined fourth current I4 is a predetermined current value determined in advance in consideration of the upper limit value (for example, 5 mA) of the on-current level (operation level) of the photocoupler 4, and at least the upper limit value. It is a current value set at a level exceeding. FIG. 2 shows an ON current variation range H2 (for example, a lower limit value of 0.1 mA and an upper limit value of 5 mA) for each element of the photocoupler 4.

  In the past, since a good output characteristic can be obtained even if the response characteristic is relatively slow, a photocoupler with a small on-current variation (see variation range H1 in FIG. 2) has been used. With the demand for speeding up the characteristics, it is necessary to use the photocoupler 4 having the characteristics of the on-current variation range H2.

  In this case, referring to the characteristic B obtained by using the photocoupler 4 without providing the transistor Tr1, in particular, the current that satisfies the condition that the input current Iin is equal to or higher than the predetermined sixth current I6 and lower than the fourth current I4. In some cases, the output of the photocoupler 4 may not be turned on despite the input voltage / current characteristics in the region X1. Therefore, the standard that the output of the input circuit body 2 must be turned on cannot be satisfied. As shown in FIG. 2, the sixth current I6 is a current value when the input voltage straddles the second voltage V2 in the case where the transistor Tr1 is not provided.

  Therefore, in the present embodiment, when it is assumed that the current Ia exceeds the preset current value I4 so as to exceed the upper limit value of the operation level of the input current of the photocoupler 4, the input side of the photocoupler 4 The transistor Tr1 is switched to energize. That is, the transistor Tr1 is instantaneously switched so as to energize the input side of the photocoupler 4. The characteristics at this time are shown as characteristics A1 to A3 in FIG. The characteristic A2 shows an example of the characteristic when the current suppression circuit 6 is not provided, and the characteristic A3 shows an example of the characteristic when the current suppression circuit 6 is provided.

  When the input current Iin exceeds the fourth current I4, the transistor Tr1 is turned on, and the slope of the voltage-current characteristic changes (see characteristics A1, A2, and A3). When the current is less than or equal to the fourth current I4, the current Ia does not flow to the input side of the photocoupler 4, and the output of the photocoupler 4 can be stably held off. On the other hand, when the current value exceeds the fourth current I4, the current Ia flows on the input side of the photocoupler 4, and the energization current can flow on the input side of the photocoupler 4. Since the output can always be turned on if the current Ia flowing to the input side of the photocoupler 4 exceeds the fourth current I4, in this case, the output can be stably turned on.

Therefore, even if the input current Iin is a current that satisfies the condition that the input current Iin is greater than or equal to the predetermined sixth current I6 and less than the fourth current I4, no current flows on the input side of the photocoupler 4 and the input circuit body 2 The problem that the output is turned on can be prevented.
Further, when the current suppression circuit 6 is provided, the current flowing through the input circuit body 2 can be suppressed as shown by the characteristic A3, and in particular, the current flowing through the resistor R5 can be suppressed. The calorific value can be suppressed.

It is also preferable to configure the circuit of the input circuit main body 2 so that the transistor Tr1 is switched when the input voltage-current characteristics in the region X3.
If the transistor Tr1 is switched to turn on the input current Ia for the photocoupler 4 when the input voltage Vin and the input current Iin satisfy the input voltage current characteristics in the region X3, the photocoupler 4 is energized. become. In this case, the current Ia is stably supplied to the input of the photocoupler 4, and the voltage current defined in the region X1 is input to the input circuit body 2 as the input voltage currents Vin and Iin. Accordingly, for example, a current exceeding the fourth current I4 exceeding the upper limit value of the operation level of the photocoupler 4 is applied to the input of the photocoupler 4. Then, the photocoupler 4 always outputs an ON signal as an output signal. Therefore, the output of the input circuit body 2 is properly guaranteed to be on.

  Thereafter, when the input voltage Vin and the input current Iin are reduced and the input voltage current Vin and Iin applied to the input circuit body 2 satisfy the conditions in the region X3, the transistor Tr1 is moved to the input side of the photocoupler 4. When the flowing current Ia is switched off, no current is supplied to the input side of the photocoupler 4. In this case, the output of the photocoupler 4 is always kept off. Therefore, the output of the input circuit body 2 is properly guaranteed as being off. As a result, an on / off output signal can be given to the PC main body 3 appropriately.

  According to the present embodiment, the transistor Tr1 is switched so as to energize the input of the photocoupler 4 on condition that the input current to the photocoupler 4 exceeds the predetermined fourth current I4. Even if the variation in the on-current of the photocoupler 4 is large, an on signal can be stably given to the PC main body 3.

  According to the present embodiment, the transistor Tr1 is switched on and off when the input voltage / current condition of the region X2 is satisfied. Therefore, in the case of the input voltage / current condition of the region X1, the input circuit body 2 The output is properly guaranteed to be on, and the output of the input circuit body 2 is properly guaranteed to be off in the case of the input voltage current condition in the region X2.

According to the present embodiment, since the current suppression circuit 6 is provided, the current flowing to the resistor R5 and the photocoupler 4 can be suppressed, and the amount of generated heat can be suppressed.
According to the present embodiment, since the voltage dividing circuit 5 is provided on the input side of the photocoupler 4 and the transistor Tr1 is switched on and off by the divided voltage V1 of the voltage dividing circuit 5, the circuit is configured with a simpler circuit. be able to.
According to this embodiment, since the voltage dividing circuit 5 detects the voltage between the input terminal IN and COM of the input circuit body 2, the voltage between the input terminal IN and COM can be measured more accurately. It can be configured with a simpler circuit.
According to the present embodiment, since the current suppression circuit 6 is provided between the voltage dividing circuit 5 and the transistor Tr1, a more practical circuit can be configured.

(Other embodiments)
The present invention is not limited to the above embodiment, and for example, the following modifications or expansions are possible.

The constant voltage circuit 6a, the capacitor C1, the diode D1, and the resistors R1 and R2, R3, and R5 may be provided as necessary.
The region X1 is defined as a region in which the input voltage currents Vin and Iin are equal to or higher than the predetermined second voltage V2 and equal to or higher than the predetermined third current I3, but is not limited thereto. Similarly, the region X3 is not limited to this.

The figure which shows schematically the circuit structure of one Embodiment of this invention (the 1) Diagram showing voltage and current characteristics and specifications of the circuit Diagram (2) schematically showing circuit configuration

Explanation of symbols

  In the drawing, 2 is an input circuit body (input circuit of a control device), 3 is a programmable controller body (control device), 4 is a photocoupler, 5 is a voltage dividing circuit (voltage detection circuit), 6 is a current suppression circuit, and 9 is A logical operation unit, Tr1, indicates a transistor (switching circuit).

Claims (6)

In an input circuit of a control device configured to provide a photocoupler on the output side and output an ON signal to the control device when the level of the input current of the photocoupler exceeds the operating level,
The photocoupler is switched to be energized on the condition that it is assumed to exceed a predetermined level that is provided in an energization path that communicates with the input of the photocoupler and is set to exceed the operating level of the input current of the photocoupler. An input circuit for a control device comprising a switching circuit. In an input circuit of a control device configured to provide a photocoupler on the output side and output an on / off signal to the control device in accordance with the level of the input current of the photocoupler,
The operation region of the input voltage current with respect to the input circuit body defined so that the output of the input circuit body is turned on is a first input voltage current region,
When the operation region of the input voltage current with respect to the input circuit body defined so that the output of the input circuit body is turned off is the second input voltage current region,
The condition is that the input voltage current applied to the input circuit body is an input voltage current in a third input voltage current region defined so as to be capable of indefinite output between the first and second input voltage current regions. A control circuit input circuit comprising a switching circuit for switching on / off energization of an input current to the photocoupler.   3. The control device input according to claim 1, further comprising a current suppression circuit for suppressing an input current to the photocoupler when an input current is switched to the photocoupler by the switching circuit. circuit. A voltage detection circuit for detecting the voltage on the input side of the photocoupler;
4. The control circuit input circuit according to claim 1, wherein the switching circuit switches energization to the photocoupler in accordance with a detection voltage of the voltage detection circuit.   The input circuit of the control device according to claim 4, wherein the voltage detection circuit detects an input terminal side voltage of the input circuit.   6. The control circuit input circuit according to claim 4, wherein the current suppression circuit is provided between the voltage detection circuit and the switching circuit.

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