JP4257797B2 - Contact input circuit - Google Patents

Description

  The present invention relates to a contact input circuit for capturing an input signal indicating an open / close state of a contact.

  An electronic interlocking device that ensures the safety of train operation in a station premises, etc., receives an input signal indicating its operating state (opening / closing state of a relay contact of the field device) from a remote field device such as a switch or a traffic light. Logic processing for ensuring safety is performed based on the operating state of the field device indicated by the input signal. In such an electronic interlocking device, even if a failure occurs, a fail-safe measure is taken so that passengers do not fall into a dangerous situation due to the failure. Input is required.

  For example, in the fail-safe input circuit disclosed in Patent Document 1 (see FIG. 3), in order to make it difficult to be affected by noise, from a field device via a threshold voltage setting circuit for making a threshold voltage or less undetectable. And a function for inspecting whether or not the threshold voltage setting circuit is operating normally.

  Specifically, when an input condition is established by closing a relay contact (not shown) and a forward voltage is applied between the (+) input terminal 1 and the (−) input terminal 2, the inspection signal input terminal When the first photocoupler P1 is on-controlled by the fail-safe test signal input from 3, the first resistor R1, the second resistor R2, the phototransistor of the first photocoupler P1, and the second photocoupler P2. An input current flows through the photodiode path, and the phototransistor of the second photocoupler P2 is turned on. As a result, a current also flows in the path of the first resistor R1 → the third resistor R3 → the phototransistor of the second photocoupler P2 → the photodiode of the third photocoupler P3, and the phototransistor of the third photocoupler P3 An output signal indicating that the input condition is satisfied is output from the output terminal 4. At this time, if the first photocoupler P1 is controlled to be turned on / off by the fail-safe inspection signal, the output signal is also turned on / off in accordance with this.

  On the other hand, in the threshold voltage setting circuit constituted by the first resistor R1 and the third resistor R3, when a failure occurs due to the open state of the third resistor R3, the threshold voltage setting circuit stops functioning and noise. In this circuit, when the third resistor R3 is opened, in this circuit, a current flows in the path of the third resistor R3 → the phototransistor of the second photocoupler P2 → the photodiode of the third photocoupler P3. Does not flow, and the phototransistor of the third photocoupler P3 is turned off. As a result, the output signal does not change even if the first photocoupler P1 is on / off controlled by the fail-safe inspection signal. Therefore, when the output signal is turned on / off in accordance with the on / off control of the first photocoupler P1 by the fail-safe inspection signal, it is recognized that the input condition is satisfied and the threshold voltage setting circuit is normal. This enables accurate and fail-safe input.

JP-A-8-80851

  However, in the circuit disclosed in Patent Document 1, current does not flow to a contact (not shown) connected to the (+) (−) input terminals 1 and 2 except when the fail-safe inspection signal is pulse-on controlled. . For this reason, it is impossible to obtain the so-called contact wetting effect in which the contact resistance is not increased by constantly flowing an electric current through the contact so as to destroy the oxide film or sulfide film on the contact surface and possible contact failure. There was a problem from the viewpoint of reducing reliability and increasing reliability.

  The present invention is intended to solve the above problem, and a contact input circuit capable of improving contact reliability of a contact while ensuring fail-safety against an open circuit failure of a resistor of a threshold voltage setting circuit. The purpose is to provide.

  The gist of the present invention for achieving the object lies in the inventions of the following items.

[1] In a contact input circuit for inputting an input signal indicating an open / close state of a contact,
A (+) input terminal and a (−) input terminal to which the input signal is input;
An inspection signal input terminal to which an inspection signal to be turned on / off is input;
An output terminal for outputting an output signal indicating the open / closed state of the contact;
A first resistor and a first circuit unit connected in series between the (+) input terminal and the (−) input terminal;
A second circuit part connected in parallel to the first circuit part,
The second circuit unit includes a second resistor, a photodiode of a first photocoupler, a phototransistor of a second photocoupler, and a phototransistor of a third photocoupler, the (+) input terminal and (−) An output circuit configured to output the output signal to the output terminal by a phototransistor of the first photocoupler, and further connected to the test signal; An input circuit for causing a forward current to flow through the photodiode of the second photocoupler in response to the inspection signal input from an input terminal; a photodiode of the first photocoupler; and a phototransistor of the second photocoupler; A first diode connected in parallel and in the opposite direction to the phototransistor of the third photocoupler connected in series. And a diode,
The first circuit unit includes a third resistor and a photodiode of the third photocoupler connected in series with respect to the polarities of the (+) input terminal and the (−) input terminal. together with, have a second diode connected in parallel and opposite directions with respect to the photodiode of the third opto-coupler,
The contact input circuit according to claim 1, wherein the output signal is input to a host device operating on a safe side when the output signal indicates opening of the contact.

  In the above invention, the first resistor and the third resistor constitute a threshold voltage setting circuit for eliminating the influence of noise. When the contact is closed and a forward voltage (input signal) is applied between the (+) and (−) input terminals, the first resistor and the third resistor connected in series between the (+) and (−) input terminals. A current always flows through a path formed by the device and the photodiode of the third photocoupler, and contact wetting is performed to maintain contact reliability.

  Further, when the current flows through the photodiode of the third photocoupler, the phototransistor of the third photocoupler is turned on, and in this state, when the on / off control of the phototransistor of the second photocoupler is performed by the inspection signal. The output signal output from the output circuit constituted by the phototransistor of the first photocoupler to the output terminal changes on / off according to the on / off of the inspection signal. On the other hand, when no forward voltage (input signal) is applied between the (+) and (−) input terminals, or when a failure occurs due to the open state of the third resistor, the phototransistor of the third photocoupler is turned off. Even if the signal is on / off controlled, the output signal does not change.

  Therefore, when the output signal changes on / off in response to the on / off control of the inspection signal, there is no open failure in the third resistor, and the forward voltage (input) is input between the (+) and (−) input terminals. Signal) is applied, and a fail-safe input is ensured even when an open failure of the resistor of the threshold voltage setting circuit occurs. The order of arrangement of the first resistor and the first circuit part connected in series, and the order of elements and resistors connected in series within the first circuit part and the second circuit part may be arbitrary.

[2] The contact input circuit according to [1], wherein an optical semiconductor element such as a photo moss relay is used instead of the photo coupler.

  In the above invention, a contact input circuit is configured in which one or more of the first, second, and third photocouplers are replaced with an optical semiconductor element such as a photo-moss relay.

  According to the contact input circuit according to the present invention, fail-safety against an open failure of the resistor constituting the threshold voltage setting circuit is ensured, and when the input condition is satisfied, the inspection signal is turned on / off. Regardless, since current always flows through the contacts, the contact reliability of the contacts can be improved by the effect of contact wetting.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a circuit diagram showing a configuration of a contact input circuit 10 according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a connection state of the contact input circuit 10 according to an embodiment of the present invention. It is.

  As shown in FIG. 2, the contact input circuit 10 receives an input signal indicating the open / closed state of the contact 22 of the remote relay device 21 from a remote field device (remote relay device) 21 such as a switch or a signal device. The (+) input terminal 11 and the (−) input terminal 12, the inspection signal input terminal 13 to which the inspection signal is input from the electronic interlocking device 30, and the output signal indicating the open / closed state of the contact 22 are sent to the electronic interlocking device 30. An output terminal 14 for output is provided. The (+) input terminal 11 and the (−) input terminal 12 are connected to a remote relay device 21 through an input line 23, and the inspection signal input terminal 13 and the output terminal 14 are electronic. Connected to interlocking device 30.

  The contact point 22 is a contact point such as a relay contact point that is actually brought into contact with the contact point 22 for electrical connection. The external circuit connected between the (+) input terminal 11 and the (−) input terminal 12 includes one or more contacts 22 and a DC power source, and the contact 22 is closed and the input condition is established. At this time, a forward voltage is applied between the (+) input terminal 11 and the (−) input terminal 12.

  The contact input circuit 10 is connected in parallel with the first resistor R1 and the first circuit unit connected in series between the (+) input terminal 11 and the (−) input terminal 12, and the first circuit unit. And a second circuit unit. The second circuit unit includes (+) a second resistor R2, a photodiode Pd1 of the first photocoupler P1, a phototransistor Pt2 of the second photocoupler P2, and a phototransistor Pt3 of the third photocoupler P3. An output circuit for outputting an output signal to the output terminal 14 is provided by a phototransistor Pt1 of the first photocoupler P1 while being connected in series in the forward direction with respect to the polarities of the input terminal 11 and the (−) input terminal 12. And an input circuit for causing a forward current to flow through the photodiode Pd2 of the second photocoupler P2 in accordance with the inspection signal input from the inspection signal input terminal 13, and the photodiode Pd1 of the first photocoupler P1 and the first The phototransistor Pt2 of the second photocoupler P2 and the phototransistor Pt3 of the third photocoupler P3 And a first diode D1 for reverse current blocking connected in parallel and opposite direction to those connected to the column.

  The first circuit unit connects the third resistor R3 and the photodiode Pd3 of the third photocoupler P3 in the forward direction with respect to the polarities of the (+) input terminal 11 and the (−) input terminal 12 in series. And a second diode D2 for blocking a reverse current connected in parallel and in the reverse direction to the photodiode Pd3 of the third photocoupler P3.

  More specifically, in the circuit example shown in FIG. 1, one end of the first resistor R1 is connected to the (+) input terminal 11, the second resistor R2 is connected to the other end of the first resistor R1, One end of the third resistor R3 is connected to a connection point between the first resistor R1 and the second resistor R2. The anode of the photodiode Pd1 of the first photocoupler P1 is connected to the other end of the second resistor R2. The collector of the phototransistor Pt1 of the first photocoupler P1 is connected to the power supply via the output terminal 14 and the resistor R4, and the emitter is grounded to form an output signal output circuit. The collector of the phototransistor Pt2 of the second photocoupler P2 is connected to the cathode of the photodiode Pd1 of the first photocoupler P1. The anode of the photodiode Pd2 of the second photocoupler P2 is connected to the power supply via the resistor R5, and the cathode is connected to the inspection signal input terminal 13, and the photodiode Pd2 of the second photocoupler P2 according to the inspection signal. An input circuit for flowing a forward current is provided.

  The anode of the photodiode Pd3 of the third photocoupler P3 is connected to the other end of the third resistor R3, and the cathode is connected to the (−) input terminal 12. The collector of the phototransistor Pt3 of the third photocoupler P3 is connected to the emitter of the phototransistor Pt2 of the second photocoupler P2, and the emitter of the phototransistor Pt3 of the third photocoupler P3 is connected to the (−) input terminal 12. ing. Further, the cathode of the first diode D1 is connected to the anode of the photodiode Pd1 of the first photocoupler P1, and the anode of the first diode D1 is connected to the (−) input terminal 12. The cathode of the second diode D2 is connected to the anode of the photodiode Pd3 of the third photocoupler P3, and the anode of the second diode D2 is connected to the (−) input terminal 12.

  The second resistor R2, the photodiode Pd1 of the first photocoupler P1, the phototransistor Pt2 of the second photocoupler P2, and the phototransistor Pt3 of the third photocoupler P3 are the (+) input terminal 11 and the (−) input terminal. What is necessary is just to connect in series so that it may become a forward direction with respect to 12 polarity, and the arrangement | sequence order of series connection may be arbitrary. Similarly, the arrangement order of the third resistor R3 connected in series and the photodiode Pd3 of the third photocoupler P3 may be changed. Furthermore, the arrangement order of the first resistor R1 and the first circuit unit connected in series may be changed.

  In the contact input circuit 10, the first resistor R 1 and the third resistor R 3 form a threshold voltage setting circuit, and the (+) input terminal 11 and the (−) input terminal 12 are caused by noise induced in the input line 23. The forward voltage drop (VF≈1.2V) of the photodiode Pd1 of the first photocoupler P1 and the collector of the phototransistor Pt2 of the second photocoupler P2 so as not to malfunction due to the noise voltage (N) generated between them. -Functions to divide the noise voltage (N) into R3 / (R1 + R3) to the threshold voltage (VH = VF + VCE≈1.4V) of the circuit due to the saturation voltage between emitters (VCE≈0.2V).

  Further, when a predetermined rated voltage (E) is applied between the (+) input terminal 11 and the (−) input terminal 12, a specified current (I = E) necessary for stable operation of the contact input circuit 10. / (R1 + R3)) functions as a load for flowing.

  The second resistor R2 is provided so that the current flowing through the first resistor R1 when the second photocoupler P2 is turned on is almost equally divided between the third resistor R3 and the second resistor R2. That is, if the second resistor R2 is not provided, only a current equal to the voltage drop caused by VCE (≈0.2V) of the second photocoupler P2 flows through the third resistor R3 and the photodiode Pd3 of the third photocoupler P3. As a result, the sink current of the phototransistor Pt3 of the third photocoupler P3 is reduced, and a specified current cannot be supplied to the photodiode Pd1 of the first photocoupler P1, so that the circuit operation becomes unstable. R2 is provided.

  Next, the operation of the contact input circuit 10 will be described.

  When the contact 22 of the remote relay device 21 is closed (the contact is made and the input condition is established), the contact input circuit 10 is connected between the (+) input terminal 11 and the (−) input terminal 12 via the input line 23. A forward voltage (input signal) is applied to. At this time, the first resistor R1, the third resistor R3, and the photodiode Pd3 of the third photocoupler P3 are connected in series between the (+) input terminal 11 and the (−) input terminal 12. A current always flows through the path, and contact wetting is performed to maintain contact reliability of the contact 22.

  Further, when the current flows through the photodiode Pd3 of the third photocoupler P3, the phototransistor Pt3 of the third photocoupler P3 is turned on. In this state, when the phototransistor Pt2 of the second photocoupler P2 is turned on by the inspection signal, the first resistor R1 → the second resistor R2 → the photodiode Pd1 of the first photocoupler P1 → the second photocoupler P2. Current flows through the phototransistor Pt2 → the phototransistor Pt3 of the third photocoupler P3, the phototransistor Pt1 of the first photocoupler P1 is turned on, and a low-level output signal is output to the output terminal 14.

  Further, when the phototransistor Pt2 of the second photocoupler P2 is turned off by the inspection signal, no current flows through the photodiode Pd1 of the first photocoupler P1, and the phototransistor Pt1 of the first photocoupler P1 is turned off. A high level output signal is output from the output terminal 14. Accordingly, when the phototransistor Pt2 of the second photocoupler P2 is controlled to be turned on / off by the inspection signal, the output signal is set to the low level and the high level corresponding to the on (low level) / off (high level) of the inspection signal. Change.

  On the other hand, when the input condition is not satisfied and a forward voltage is not applied between the (+) input terminal 11 and the (−) input terminal 12, or when the third resistor R3 is broken down, the third photo Since no current flows through the photodiode Pd3 of the coupler P3, the phototransistor Pt3 of the third photocoupler P3 is turned off. Even if the second photocoupler P2 is controlled to be turned on / off by the inspection signal, the phototransistor of the first photocoupler P1 is turned off. The current does not always flow through the diode Pd1, the phototransistor Pt1 of the first photocoupler P1 is always turned off, and the output signal is fixed at a high level.

  Therefore, when the electronic interlocking device 30 controls the inspection signal to be turned on / off, if the output signal changes between the low level and the high level corresponding to this, there is no failure due to the open state of the third resistor R3. In addition, it can be determined that the input condition is satisfied (the contact is closed). That is, when an open failure of the third resistor R3 occurs and the threshold voltage is not set correctly, the output signal is fixed at a high level. Therefore, the noise generated at the open failure of the third resistor R3 is input conditions. Therefore, it is possible to input the correct true operation information indicating the closing of the contact 22 of the remote relay device 21 (satisfaction of the input condition) to the electronic interlocking device 30.

  The electronic interlocking device 30 is provided with a fail-safe measure so that it operates on the safe side when the input condition is not satisfied (opening of the contact 22), and the contact input circuit 10 has a failure of the third resistor R3. Since the output signal indicating that the input condition is not satisfied is output at the time, the contact input circuit 10 gives the electronic interlocking device 30 a fail-safe input of the operation state of the contact.

  The embodiment of the present invention has been described with reference to the drawings. However, the specific configuration is not limited to that shown in the embodiment, and there are changes and additions within the scope of the present invention. Are also included in the present invention.

  For example, the output circuit composed of the phototransistor Pt1 of the first photocoupler P1 is a collector load type in which the emitter is grounded and the collector side is connected to the power supply via the resistor R4, but the collector is connected to the power supply, An emitter load type in which an emitter is grounded through a resistor and an output signal is output from a connection point between the emitter and the resistor may be used.

  Furthermore, instead of any one or more of the first, second, and third photocouplers P1, P2, and P3, other types of optical semiconductor elements such as a photo moss relay may be used.

1 is a circuit diagram of a contact input circuit according to an embodiment of the present invention. It is a block diagram which shows the connection state of the contact input circuit concerning one embodiment of this invention. It is a circuit diagram of the conventional fail safe input circuit.

Explanation of symbols

D1 ... 1st diode
D2 ... second diode P1 ... first photocoupler Pt1 ... first photocoupler phototransistor Pd1 ... first photocoupler photodiode P2 ... second photocoupler Pt2 ... second photocoupler phototransistor Pd2 ... second photocoupler Photodiode P3 ... Third photocoupler Pt3 ... Phototransistor of third photocoupler Pd3 ... Photodiode of third photocoupler R1 ... First resistor R2 ... Second resistor R3 ... Third resistor R4, R5 ... Resistance 10 ... Contact input circuit 11 ... (+) input terminal 12 ... (-) input terminal 13 ... Inspection signal input terminal 14 ... Output terminal 21 ... Remote relay device 22 ... Contact 23 ... Input line 30 ... Electronic interlocking device

Claims (2)

In a contact input circuit for inputting an input signal indicating the open / close state of a contact,
A (+) input terminal and a (−) input terminal to which the input signal is input;
An inspection signal input terminal to which an inspection signal to be turned on / off is input;
An output terminal for outputting an output signal indicating the open / closed state of the contact;
A first resistor and a first circuit unit connected in series between the (+) input terminal and the (−) input terminal;
A second circuit part connected in parallel to the first circuit part,
The second circuit unit includes a second resistor, a photodiode of a first photocoupler, a phototransistor of a second photocoupler, and a phototransistor of a third photocoupler, the (+) input terminal and (−) An output circuit configured to output the output signal to the output terminal by a phototransistor of the first photocoupler, and further connected to the test signal; An input circuit for causing a forward current to flow through the photodiode of the second photocoupler in response to the inspection signal input from an input terminal; a photodiode of the first photocoupler; and a phototransistor of the second photocoupler; A first diode connected in parallel and in the opposite direction to the phototransistor of the third photocoupler connected in series. And a diode,
The first circuit unit includes a third resistor and a photodiode of the third photocoupler connected in series with respect to the polarities of the (+) input terminal and the (−) input terminal. together with, have a second diode connected in parallel and opposite directions with respect to the photodiode of the third opto-coupler,
The contact input circuit according to claim 1, wherein the output signal is input to a host device operating on a safe side when the output signal indicates opening of the contact. The contact input circuit according to claim 1, wherein an optical semiconductor element such as a photo moss relay is used instead of the photo coupler.

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