JP5576849B2 - Digital output circuit with failure detection function - Google Patents

Description

  The present invention relates to a digital output circuit, for example, a digital output circuit constituting a railway system that requires high reliability and high availability, and can detect a failure with a simple configuration without erroneous output to a load. The present invention relates to a digital output circuit.

  Railway systems, which are the backbone of social infrastructure, are required to have high reliability and availability, and even in the event of a sudden accident or failure, it is required to quickly restore the system.

  In order to realize the high reliability and high availability of this railway system, the system components are constantly monitored for failures, and if a failure of a component is discovered, the failed component is quickly replaced with a new component. It is essential to design the system so that the downtime of the entire system is minimized.

  In addition, a digital output circuit that is used in a railway signal control system and plays a role of actually controlling field devices such as traffic lights and switches is required to promptly detect a faulty part.

  As a means for realizing such a digital output circuit, a configuration in which a voltage detection circuit is connected to the output side of a switch element constituting a DC output circuit is generally used.

  For example, in a DC output circuit in which a plurality of switch elements are connected in series and a voltage sensor is connected to the output side of each switch element to detect a failure of the switch element, a common system switch is connected to the negative output of the DC output circuit This is a DC output circuit having a failure detection function configured to detect a failure switch element even when the elements are connected and one switch element fails (Patent Document 1).

  In this DC output circuit, if the voltage detection circuit detects the presence of voltage when the switch element is turned on, and the voltage detection circuit detects no voltage when the switch element is turned off, the switch element is normal, and conversely When the voltage detection circuit detects that there is no voltage when ON is controlled, and when the voltage detection circuit detects the presence of voltage when the switch element is OFF control, it is determined that the switch element has failed.

  According to such a DC output circuit, it is possible to reliably detect a failure of the switch element by the control state of the switch element and the DC detection voltage of the voltage detection circuit, which is an extremely effective means.

JP 2000000822620 A

  However, on the other hand, a procedure is required for controlling the switch elements, and the control means for the control is complicated such that a large number (three) of the switch elements are required, resulting in an economical problem.

  The present invention has been made in view of the above points, and an object thereof is to provide a digital output circuit that has a simple configuration, does not erroneously output a load, and can detect a failure of a switch element at an arbitrary timing. It is in.

  In order to achieve the above object, the present invention provides a digital output circuit that applies a DC voltage to a load, for example, by turning on a switch element disposed between a DC power source and a load, and outputs the switch element on the output side of the switch element. A capacitor is connected in parallel with the load, and a resistor and an AC power supply series circuit on the input side of the switch element and a voltage detection circuit for detecting the AC voltage of the AC power supply are detected to detect the presence or absence of the switch element failure. This is a digital output circuit to which a failure detection circuit is connected.

  In the present invention, for example, when the voltage detection circuit determines whether the voltage detection unit for detecting the voltage of the AC power supply and the detection voltage of the voltage detection unit are higher or lower than a threshold voltage, The digital output circuit includes an abnormality / normality determination unit that determines that the switch element is normal and determines that the switch element is abnormal when it is determined to be low.

  The present invention further includes, for example, a second voltage detection circuit that detects a DC voltage of the DC power supply on the output side of the switch element, and the second voltage detection circuit detects whether or not the switch element is faulty. A digital output circuit in which a failure detection circuit is connected, a bidirectional blocking Zener diode is connected between the load and the capacitor, and a blocking voltage of the bidirectional blocking Zener diode is set larger than a voltage across the capacitor. is there.

  Further, the present invention provides a digital output circuit that applies a DC voltage to a load by, for example, controlling a switch element disposed between a DC power supply and a load in parallel with the load at the output terminal of the switch element. A capacitor is connected to the input side of the switch element, and a series circuit of a resistor and an AC power source is constituted by a first voltage detection circuit for detecting an AC voltage of the AC power source, and the DC side is connected to the output side of the switch element. A second voltage detection circuit for detecting a DC voltage of the power supply; and a failure detection circuit for detecting the presence or absence of a failure of the switch element is connected by the first and second voltage detection circuits; and the load and the capacitor A bidirectional blocking Zener diode is connected between them, and the blocking voltage of the bidirectional blocking Zener diode is set larger than the voltage across the capacitor. A digital output circuit.

  According to the present invention, it is possible to provide a digital output circuit having a simple configuration and capable of detecting a switch element failure at an arbitrary timing without erroneous output to a load.

FIG. 1 is a circuit diagram showing a basic configuration of a digital output circuit of the present invention. FIG. 2 is a functional block diagram showing a configuration example of the voltage detection circuit of the present invention. FIG. 3 is a flowchart for explaining a control procedure for determining whether the digital output circuit is normal or faulty. FIG. 4 is an electronic circuit diagram showing a specific example of a digital output circuit using the present invention. FIG. 5 is a functional block diagram showing a configuration example of the voltage detection circuits 5 and 11 of FIG. FIG. 6 is a flowchart for explaining the operation control procedure of the digital output circuit.

  Embodiments of the present invention will be described below with reference to the drawings, taking a digital output circuit applied to a railway control system as an example.

  FIG. 1 is a circuit diagram showing a basic configuration of a digital output circuit of the present invention, FIG. 2 is a functional block diagram showing a configuration example of a voltage detection circuit of the present invention, and FIG. 3 judges whether the digital output circuit is normal or faulty. It is a flowchart for demonstrating a control procedure.

  In FIG. 1, 1 is a DC power supply, 2 is an AC power supply, 3 is a resistor, 4 is a changeover switch for connecting / disconnecting the AC power supply 2 to / from the digital output circuit, 5 is a voltage detection circuit, and 6 is a load. A switch element for controlling whether or not to apply a voltage to 8, 7 is a capacitor, and 8 is a load.

  A changeover switch 4 and a switch element 6 are connected in series between the DC power supply 1 and the load 8. Moreover, the voltage detection circuit 5, the capacitor 7, and the AC power supply 2 and the series circuit of the resistor 3 are connected in parallel.

  The capacitor 7 is located on the rear side of the switch element 6 and is connected in parallel to the load. The series circuit of the AC power source 2 and the resistor 3 is arranged on the front side, and the voltage detection circuit 5 is arranged between them. .

  One end of the series circuit of the AC power supply 2 and the resistor 3 is connected to one fixed terminal of the changeover switch 4, and the other end is connected to the negative electrode side of the DC power supply 1.

  One end of the voltage detection circuit 5 is connected to the switch 4 on the positive side of the DC power source 1 and the movable contact side of the switch element 6, and the other end is connected to the negative side of the DC power source 1. The other end of the changeover switch 4 is connected to the positive electrode side of the DC power source 1, and the fixed terminal of the switch element 6 is connected to one end side of the load 8.

  The voltage detection circuit 5 detects the voltage of the DC power supply 1 or the AC power supply 2 when an abnormality or failure occurs in the switch element 6, and determines the abnormality or failure of the switch element 6 by detecting the voltage. As shown in FIG. 2, a voltage detection unit 51 that detects a voltage, and a failure determination that determines whether or not the detection voltage of the voltage detection unit exceeds a predetermined threshold and determines abnormality / failure of the switch element 6, etc. A portion 52 is provided.

  Here, the AC circuit 2 and the DC circuit of the resistor 3 and the voltage detection circuit 5 constitute a failure detection circuit for detecting whether or not the switch element 6 has failed. The operation of the failure detection circuit will be described later.

  As in this configuration, when a failure occurs in the switch element 6 in the circuit state, that is, in the state where the changeover switch 4 is switched to the DC power supply 1 or the AC power supply 2 side, the failure can be detected accurately. This failure detection can be performed, for example, by determining whether the voltage of the DC power supply 1 or the AC power supply 2 is higher or lower than the threshold voltage when the switch element 6 is turned off due to an abnormality.

  Hereinafter, the failure detection operation and procedure of the switch element 6 will be described. First, the changeover switch 4 is switched to the AC power supply 2 side.

  In this case, when the voltage detection unit 51 of the voltage detection circuit 5 detects the voltage of the AC power source 2, and the abnormality (failure) / normality determination unit 52 is turned off (step S401) as shown in FIG. If it is determined that the detection voltage of the voltage detection circuit 5 is higher than the predetermined threshold voltage (step S402), it is determined to be normal, and if it is determined to be lower than the threshold voltage, it is determined to be abnormal (S403). .

  When the switch element 6 is turned on (step S404), conversely, when it is determined that the detected voltage is lower than the threshold voltage (step S405), it is determined normal (step S406) and is higher than the threshold voltage. If it is determined (step S405), it is determined as abnormal (step S403).

  In a series of failure detection operations and control procedures, only a voltage determined by the ratio of the impedance of the resistor 3 and the capacitor 7 is applied to the load 8. For this reason, if the resistance value of the resistor 3, the capacitance of the capacitor 7, and the frequency of the AC power supply 2 are appropriately selected, the voltage applied to the load 8 can be prevented from malfunctioning. Thereby, the load 8 does not malfunction due to the failure of the relay 10.

  4 is an electronic circuit diagram showing a specific example of a digital output circuit using the present invention, FIG. 5 is a functional block diagram showing a configuration example of the voltage detection circuits 5 and 11 of FIG. 3, and FIG. 6 is an operation of the digital output circuit. It is a flowchart for demonstrating a control procedure.

  4, reference numerals 9 and 10 denote relays, which control the output to the load 8 and correspond to the changeover switch 4 and the switch element 6 in FIG. The relays 9 and 10 may be semiconductor relays or mechanical contact relays.

  The relays 9 and 10 are controlled by a relay control circuit 13 including an excitation on / off control unit of the CPU. This relay control circuit 13 is used to control devices such as traffic lights and crossings in a system called an interlocking device. For example, when this relay control circuit 13 is used for signal lamp control, the CPU shown in the figure receives an instruction transmitted via the communication network from the control unit (interlocking logic unit) of the interlocking device, and excites the relays 9 and 10. Control the lighting of the signal. A series of operations is automatically executed according to the operation logic of the interlocking device (for example, a red signal is turned on when an intruding train is detected).

  Reference numeral 11 denotes a voltage detection circuit that is connected in parallel to the position before the capacitor 7 at the subsequent stage of the relay 10. The voltage detection circuit 11 detects the presence / absence of a DC voltage of the DC power supply 1 and, as shown in FIG. An abnormality (failure) / normality determination unit 111 for determining and determining an element abnormality / failure is provided. The operation will be described later.

  A bidirectional blocking Zener diode 12 is connected in series with the load 8. The other parts are the same as those in FIG. 1 and FIG.

Here, the bidirectional blocking type Zener diode 12 has a circuit constant of, for example, a resistance of 3: 100 kΩ.
Capacitor 7: 1μF
AC power supply 100V 50Hz
If the voltage is set to, the voltage across the capacitor 7 is about 3V (effective value). Considering the peak voltage at this time, the Zener diode 12 is selected with a margin of 5V.

  The operation and control procedure of this digital output circuit will be described below with reference to FIG.

  First, when the digital output circuit is turned off, the relays 9 and 10 are not excited. The relays 9 and 10 are excited by a relay control circuit 13 (CPU excitation on / off control unit).

  In this state, the voltage detection unit 51 of the voltage detection circuit 5 detects the voltage of the AC power supply 2, and the abnormality (failure) / normality determination unit 52 detects that the detection voltage is a predetermined threshold voltage in step S502 shown in FIG. If it is determined that the value is higher than that, the circuit is determined to be normal.

  When the abnormality (failure) / normality determination unit 52 of the voltage detection circuit 5 determines that the voltage is lower than the predetermined threshold voltage in step S shown in FIG. 6, the relays 9 and 10, the AC power supply 2, the resistance 3. It is determined that one or more of the voltage detection circuits 5 are abnormal.

  In particular, when the relay 10 is short-circuited, an alternating current flows through a closed circuit including the AC power source 2, the resistor 3, the capacitor 7, and the relay 10, and the impedance of the resistor 3 and the capacitor 7 is connected to both ends of the capacitor 7. An alternating voltage determined by the ratio is applied.

  At this time, if the blocking voltage of the bidirectional blocking Zener diode 12 is designed to be larger than the voltage across the capacitor 7, it is possible to prevent an AC voltage from being applied to the load 8. The load 8 does not malfunction.

  When the digital output circuit is turned on, the relay 9 is first excited. As a result, the voltage detection unit 51 of the voltage detection circuit 5 detects the DC voltage output from the DC power supply 1. If the voltage detection unit 51 of the voltage detection circuit 5 does not detect a DC voltage, it can be determined that one or more of the DC power supply 1, the relay 9, and the voltage detection circuit 5 are malfunctioning.

  Next, the relay 10 is excited. At this time, the DC voltage presence / absence detection unit 112 of the voltage detection circuit 11 detects the DC voltage, and as shown in FIG. 6, the abnormality (failure) / normality determination unit 111 determines that the digital output circuit has output normally. To do.

  Here, if the DC voltage presence / absence detection unit 112 of the voltage detection circuit 11 does not detect the DC voltage, it is determined that the capacitor 7 or the load 8 side is faulty.

  According to the embodiment of the present invention described above, it is possible to perform output after confirming the soundness of each component constituting the digital output circuit. In addition, it is possible to eliminate a malfunction of the load in the procedure for performing the failure detection.

  If it is a system that needs to determine whether or not each component of the digital output circuit is faulty, it can be applied without being specified as a railway control system.

DESCRIPTION OF SYMBOLS 1 DC power supply 2 AC power supply 3 Resistance 4 Changeover switch 5 Voltage detection circuit 6 Switch element 7 Capacitor 8 Load 9 Relay 10 Relay 11 Voltage detection circuit 12 Bidirectional blocking type Zener diode 13 Relay control circuit

Claims (4)

In the digital output circuit for applying a DC voltage to the load by turning on the control placed the switch element between the DC power supply and the load,
A capacitor is connected in parallel with the load on the output side of the switch element, and a failure detection circuit for detecting the presence or absence of a failure of the switch element is connected on the input side of the switch element. digital output circuit, wherein the benzalkonium consists voltage detection circuit for detecting a series circuit and the AC AC voltage of the power supply of the power supply.   The digital output circuit according to claim 1, wherein the voltage detection circuit determines whether the voltage detection unit detects the voltage of the AC power supply, and whether the detection voltage of the voltage detection unit is higher or lower than a threshold voltage. A digital output circuit comprising an abnormality / normality determination unit that determines that the switch element is normal when it is determined to be high, and that determines that the switch element is abnormal when it is determined as low. 2. The digital output circuit according to claim 1, further comprising a second voltage detection circuit that detects a DC voltage of the DC power supply on an output side of the switch element, and the switch element is provided by the second voltage detection circuit. Connect a failure detection circuit that detects the presence or absence of
A digital output circuit, wherein a bidirectional blocking Zener diode is connected between the load and the capacitor, and a blocking voltage of the bidirectional blocking Zener diode is set larger than a voltage across the capacitor. In the digital output circuit for applying a DC voltage to the load by turning on the control placed the switch element between the DC power supply and the load,
A capacitor is connected in parallel with the load to the output end of the switch element, and a failure detection circuit is connected to the input side of the switch element. The failure detection circuit includes a series circuit of a resistor and an AC power source and the AC power source. a first voltage detection circuit for detecting an AC voltage, is composed of a second voltage detection circuit for detecting a DC voltage of the DC power supply to an output side of the switching element, the first, second voltage detection The circuit detects the failure of the switch element ,
A digital output circuit, wherein a bidirectional blocking Zener diode is connected between the load and the capacitor, and a blocking voltage of the bidirectional blocking Zener diode is set larger than a voltage across the capacitor.

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