JP2019165395A - Central processing device - Google Patents

Abstract

To obtain a central processing device which can reduce a required time to detect the short-circuit of a transmission line.SOLUTION: A central processing device 1, which supplies power supply to a terminal through two transmission lines, transmits a control signal in a voltage mode and receives the response signal of a constant width from a terminal in a current mode, includes: a current detection circuit 11 which detects a current flowing through the terminal through the transmission line; a short-circuit detection circuit 12 which, based on the detection result by the current detection circuit 11, determines the existence or non-existence of a short-circuit in the two transmission lines; and a current cutoff circuit 13 which, when the short-circuit detection circuit 12 detects a short-circuit, cuts off the current flowing through the transmission line. The short-circuit detection circuit 12 includes: a filter circuit 121 which, when a detection result input from the current detection circuit 11 does not indicate a response signal from the terminal, outputs the detection result; and a comparison circuit which compares a detection result after filtering, which is output from the filter circuit 121, with a threshold.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a central processing unit that transmits a control signal while supplying power to a controlled device via two transmission lines.

  A signal transmission method in which a control device that controls a controlled device transmits a control signal while supplying power to the controlled device via two transmission lines is used for controlling lighting devices (for example, patents). Reference 1). When controlling a lighting device using such a signal transmission method, a control device that controls the lighting device transmits a control signal to the lighting device in a voltage mode. On the other hand, when the lighting device transmits a signal to the control device, the lighting device transmits the signal to the control device in the current mode.

  In the above signal transmission system, there is a problem that a large current flows when the transmission lines are short-circuited, and if this state continues for a long time, the parts are burnt. Therefore, when a short circuit occurs, a protection function is provided to detect this and interrupt the current.

  In the signal transmission system described in Patent Document 1, a bit for short-circuit detection is provided in a signal transmitted from a terminal device as a controlled device to a central control device as a control device, and the central control is performed by checking the state of this bit. The device detects a short circuit in the transmission line.

JP-A-3-285429

  In the invention described in Patent Document 1, a short-circuit detection bit is arranged at the head of a signal section, thereby reducing the time required from when the transmission line is short-circuited until the short-circuit is detected. However, from the viewpoint of component protection, it is desired to further shorten the time required until the occurrence of a short circuit is detected. Further, in the invention described in Patent Document 1, since a short circuit is detected in a section where a short circuit detection bit is allocated, depending on the timing at which the short circuit occurs, the time until the next short circuit detection bit becomes longer. There was a problem of slow detection.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a central processing unit capable of shortening the time required to detect a short circuit of a transmission line.

  In order to solve the above-described problems and achieve the object, the invention according to the present invention supplies power to the terminal device via two transmission lines and transmits a control signal in a voltage mode, so that a constant signal from the terminal device can be obtained. A central processing unit for receiving a response signal of width in a current mode. The central processing unit includes a current detection circuit that detects a current flowing through the transmission line via the transmission line, a short-circuit detection circuit that determines whether or not the two transmission lines are short-circuited based on a detection result by the current detection circuit, When the short circuit detection circuit detects a short circuit, a current interrupt circuit that interrupts the current flowing through the transmission line is provided. The short-circuit detection circuit includes a filter circuit that outputs a detection result when the detection result input from the current detection circuit does not indicate a response signal from the terminal, and a detection result after filtering output from the filter circuit. A comparison circuit for comparing with a threshold value.

  According to the present invention, there is an effect that a central processing unit capable of shortening the time required to detect a short circuit of a transmission line is obtained.

The figure which shows an example of the signal transmission system comprised including the intermediate | middle processing apparatus concerning Embodiment 1. FIG. The figure which shows the structural example of the central processing unit concerning Embodiment 1. The figure which shows the 1st example of the communication operation of the central processing unit concerning Embodiment 1, and a terminal device. The figure which shows the 2nd example of the communication operation of the central processing unit concerning Embodiment 1, and a terminal device. The figure which shows an example of the circuit structure of the central processing unit concerning Embodiment 1. The figure which shows an example of the circuit structure of the central processing unit concerning Embodiment 2.

  Below, the central processing unit concerning embodiment of this invention is demonstrated in detail based on drawing. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating an example of a signal transmission system configured to include the intermediate processing device according to the first exemplary embodiment of the present invention.

  A signal transmission system 100 according to the present embodiment includes a central processing unit 1 and a plurality of terminals 2 to realize an illumination system. The central processing unit 1 and each terminal device 2 are connected via two transmission lines, a transmission line sa and a transmission line sb. The central processing unit 1 is connected to an AC power source 3 and receives supply of AC power from the AC power source 3.

  The central processing unit 1 supplies electric power to each terminal device 2 via the transmission line sa and the transmission line sb, and controls each terminal device 2 by transmitting a control signal. Lighting devices are connected to each terminal device 2, and each terminal device 2 performs lighting and extinguishing of the connected lighting device, adjustment of the light emission amount, and the like according to the content of the control signal received from the central processing unit 1.

  The central processing unit 1 transmits a control signal for controlling the terminal 2 in a voltage mode of ± 24V, for example. Specifically, the central processing unit 1 applies a DC voltage to each transmission line so that the potential difference between the two transmission lines is 24 V, and the polarity of the applied DC voltage is included in each control signal. Invert according to the bit state. For example, when transmitting a bit representing “0”, the central processing unit 1 performs control so that the voltage of the transmission line sb with respect to the transmission line sa becomes + 24V for a predetermined time. When transmitting a bit representing “1”, the central processing unit 1 controls the transmission line sb so that the voltage of the transmission line sb becomes −24 V for a predetermined time. On the other hand, each terminal device 2 responds to the central processing unit 1 by generating a current mode signal having a pulse width of, for example, 100 μs by short-circuiting the transmission line for a certain time. Such a signal transmission method is referred to as a two-wire transmission method in the following description.

  FIG. 2 is a diagram illustrating a configuration example of the central processing unit 1 according to the first embodiment. The central processing unit 1 includes a current detection circuit 11, a short circuit detection circuit 12, a current cutoff circuit 13, a drive circuit 14, a bridge circuit 15, a reception circuit 16, and a control circuit 17. The short circuit detection circuit 12 includes a filter circuit 121. The bridge circuit 15 includes a constant current circuit 151.

  The current detection circuit 11 detects the value of the current flowing from the power source to the terminal device 2 via the central processing unit 1 and the transmission line sa and the transmission line sb. The power supply voltage Vcc1 is generated by a converter (not shown) rectifying AC power supplied from the AC power supply 3 shown in FIG.

  Based on the current value detected by the current detection circuit 11, the short circuit detection circuit 12 detects a short circuit of the transmission line, that is, determines whether or not the transmission line is short-circuited. The filter circuit 121 included in the short circuit detection circuit 12 filters the detection result by the current detection circuit 11 by time, and prevents a detection result that does not satisfy a certain condition from being used in the short circuit detection operation.

  The current interruption circuit 13 is controlled by the control circuit 17, and interrupts the current supply to the terminal device 2 when the short circuit detection circuit 12 detects a short circuit.

  The drive circuit 14 is controlled by the control circuit 17 to generate and output a voltage mode control signal to be transmitted to the terminal device 2. Specifically, the drive circuit 14 switches the polarity of the voltage mode signal output from the bridge circuit 15 by switching the on / off operation of the bridge circuit 15 and generates a control signal.

  The bridge circuit 15 outputs a voltage mode signal and supplies power to the terminal device 2. The constant current circuit 151 of the bridge circuit 15 limits the current supplied from the central processing unit 1 to the terminal device 2 so that no current exceeding a certain value flows.

  The receiving circuit 16 receives a current mode signal output from the terminal device 2. The control circuit 17 controls the output of the voltage mode signal transmitted to the terminal device 2 by controlling the current cutoff circuit 13 and the drive circuit 14. The control circuit 17 receives a response signal from the terminal device 2 via the receiving circuit 16.

  Here, a two-wire transmission system applied to the signal transmission system 100 will be described with reference to FIGS. 3 and 4. FIG. 3 is a diagram illustrating a first example of communication operation between the central processing unit 1 and the terminal device 2 according to the first embodiment, and illustrates an operation in a normal state, that is, an operation in a case where a transmission line short-circuit does not occur. Show. FIG. 4 is a diagram illustrating a second example of the communication operation between the central processing unit 1 and the terminal device 2 according to the first embodiment, and illustrates an operation when a transmission line short circuit occurs.

  3 and 4, the downlink transmission section described as “downlink transmission” is a section in which the central processing unit 1 as the control device transmits a voltage mode control signal to the terminal device 2 as the controlled device. The uplink transmission section described as “uplink transmission” is a section in which the terminal 2 transmits a current mode response signal to the central processing unit 1. A signal transmission section, also called a control frame, composed of a downlink transmission section and an uplink transmission section is repeated across a trailer section described as “trailer”. That is, a downstream transmission section of the next control frame appears after the illustrated trailer section.

  As shown in FIG. 3, in the downlink transmission section, the central processing unit 1 determines the polarity of the potential difference between the two transmission lines in a time corresponding to the value of each bit of the control information transmitted to the terminal 2. Is reversed. In the upstream transmission section, the central processing unit 1 performs two transmissions so that the potential of one transmission line becomes +24 V with respect to the potential of the other transmission line for a predetermined period of time at a constant period. A synchronization signal is generated by controlling the potential difference between the lines. The central processing unit 1 controls the terminal 2 corresponding to the identification information, for example, by transmitting the identification information of the terminal 2 and the control information indicating the instruction content in the downlink transmission section.

  When transmitting a response signal to the central processing unit 1, the terminal device 2 generates a response signal at a timing based on the synchronization signal. Note that the pulse width of each response signal is constant. However, as shown in FIG. 4, when the transmission line is short-circuited, the current continues to flow, and thus the central processing unit 1 cannot detect the response signal from the terminal device 2. In addition, as described above, since the current continues to flow, there is a possibility that the parts are burned out. Note that the value of the current that flows when a short circuit occurs is limited so as not to exceed a certain value by the action of the constant current circuit 151 shown in FIG. FIG. 4 shows an example in which a short circuit occurs in the downstream transmission section, but the same is true when a short circuit occurs in the upstream transmission section and the trailer section.

  FIG. 5 is a diagram illustrating an example of a circuit configuration of the central processing unit 1 according to the first embodiment. In addition, the circuit element which comprises each circuit with which the central processing unit 1 is provided, and the connection relation of each circuit element are not limited to what was shown in FIG. As long as the operation of each circuit described below can be realized, the types, number, and connection relationships of circuit elements constituting the circuit may be different.

  Next, the operation of the central processing unit 1 having the configuration shown in FIG. 5 will be described. In the present embodiment, each of an operation at a steady state where the transmission line is not short-circuited and an operation when the transmission line is short-circuited where the transmission line is short-circuited will be described.

(Operation of the central processing unit 1 during normal operation)
The control circuit 17 is realized by a microcontroller, for example, and performs on / off control of the terminal a and the terminal b of the drive circuit 14 by port control. Specifically, the control circuit 17 performs control so that one of the terminal a and the terminal b of the drive circuit 14 is in a high state and the other is in a low state. Thereby, the bridge circuit 15 switches between positive and negative of the transmission line output voltage.

  For example, the control circuit 17 controls the terminal a of the drive circuit 14 to High and controls the terminal b to Low. As a result, the transistor Q1 of the bridge circuit 15 is turned on and the transistor Q2 is turned off. Further, the transistor Q4 is turned off and the transistor Q5 is turned on. That is, the output terminal of the transmission line sa (hereinafter sometimes referred to as the output terminal sa) has a voltage of + 24V with respect to the potential of the output terminal of the transmission line sb (hereinafter sometimes referred to as the output terminal sb). The current flows from the power supply voltage Vcc1 to the transmission line sa via the resistor R7, the transistor (FET: Field Effect Transistor) Q8, and the transistor Q1. The current flowing through the transmission line sa flows through the terminal 2 and then through the transistor Q5 and the resistor R14 to GND.

  On the other hand, when the control circuit 17 controls the terminal a of the drive circuit 14 to Low and the terminal b to High, the logic is opposite to that when the terminal a is High and the terminal b is Low. That is, the transistor Q1 of the bridge circuit 15 is turned off and the transistor Q2 is turned on. Further, the transistor Q4 is turned on and the transistor Q5 is turned off. In this case, since the potential of the output terminal sa is −24 V with respect to the potential of the output terminal sb, the direction of the current flowing through the transmission line sa and the transmission line sb is also when the terminal a is High and the terminal b is Low. The opposite is true.

  In this way, the control circuit 17 transmits the control signal to each terminal device 2 in the voltage mode while changing the timing for switching the terminal voltages of the output terminal sa and the output terminal sb. The terminal device 2 operates by rectifying the voltage applied via the transmission line sa and the transmission line sb to generate an internal power supply, and takes a time for switching the potential difference between the transmission line sa and the transmission line sb. The control signal by voltage mode is received by monitoring.

  When returning a response to the control signal received from the central processing unit 1, the terminal device 2 transmits the transmission line sa in a predetermined section of the control frame (corresponding to the upstream transmission section shown in FIGS. 3 and 4). Further, the transmission line sb is short-circuited by a switching element such as a transistor for a certain time such as 100 μs. As a result, a current larger than that in the steady state is caused to flow on the transmission line for a fixed time, and a response in the current mode is made to the central processing unit 1. The central processing unit 1 receives the response signal from the terminal device 2 by the receiving circuit 16. The receiving circuit 16 monitors the amount of current flowing through the resistor R14 by the comparator Comp2, and when it detects that a certain amount or more of current flows through the resistor R14 in a predetermined section of the control frame, the receiving circuit 16 A signal indicating that the response is received is output to the control circuit 17.

(Operation of central processing unit 1 when transmission line is short-circuited)
The constant current circuit 151a included in the bridge circuit 15 includes a transistor Q3 and a resistor R2. When a current equal to or greater than a certain value flows through the resistor R2, the transistor Q3 is turned on and limits a current that can be passed through the transistor Q1. The constant current circuit 151b included in the bridge circuit 15 includes a transistor Q6 and a resistor R5. When a current exceeding a certain value flows through the resistor R5, the transistor Q6 is turned on, and the current that can be passed through the transistor Q4 is limited. To do. Thereby, even if the transmission line is short-circuited, the peak current of the current flowing out to the transmission line is limited to be constant.

  The current detection circuit 11 monitors the amount of current flowing through the resistor R7 with the detection circuit 111 for current detection, and outputs the detected current value to the short circuit detection circuit 12. The detection circuit 111 can be realized using, for example, a current detection IC (Integrated Circuit).

  The short circuit detection circuit 12 includes a filter circuit 121 and a comparator Comp1 that is a comparison circuit. The filter circuit 121 includes a resistor R8 and a capacitor C1. The signal output from the filter circuit 121 is input to the non-inverting input terminal of the comparator Comp1. Further, a voltage Vref1, which is a threshold value for determining whether or not a transmission line short circuit has occurred, is input to the inverting input terminal of the comparator Comp1. The output terminal of the comparator Comp1 is connected to the power supply Vcc2 via the pull-up resistor R9.

  In the short circuit detection circuit 12, the filter circuit 121 filters the detection result output from the current detection circuit 11 by time. Specifically, when the detection result input from the current detection circuit 11 shows a current value larger than a certain value for a certain period of time, the filter circuit 121 controls the high-level signal indicating that the comparator Comp1 indicates the occurrence of a short circuit. The detection result in the current detection circuit 11 is filtered so as to be output to the circuit 17. That is, the filter circuit 121 determines the level of the input signal to the non-inverting input terminal of the comparator Comp1 when a state in which a current having a value larger than a predetermined constant value continues to flow through the resistor R7 continues for a predetermined time. Is filtered so that the voltage Vref1 exceeds the threshold voltage Vref1. The time for filtering by the filter circuit 121 is set to be longer than the response time of the terminal device 2. For example, when the response time of the terminal 2, that is, the pulse width of the response signal shown in FIG. 3 is 100 μs, the time for filtering by the filter circuit 121 is set to 100 μs. In this case, the filter circuit 121 starts outputting a value exceeding the voltage Vref1 when the detection result by the current detection circuit 11 continues for 100 μs or more. Thereby, the erroneous detection of a short circuit can be prevented. That is, the state where the current is flowing through the transmission line due to the response operation of the terminal at the above-described steady state is not determined as the occurrence of a short circuit in the transmission line. As described above, the filter circuit 121 outputs the detection result when the detection result input from the current detection circuit 11 does not indicate the response signal from the terminal device 2. The constants of the resistor R8 and the capacitor C1 of the filter circuit 121 are set based on the pulse width of the response signal transmitted by the terminal device 2 and the input voltage Vref1 to the inverting input terminal of the comparator Comp1.

  When the input signal from the short circuit detection circuit 12 becomes High level and receives a notification of occurrence of a short circuit, the control circuit 17 outputs a control signal to the current interrupt circuit 13 to interrupt the current. That is, when the input signal from the short circuit detection circuit 12 changes from the Low level to the High level, the control circuit 17 switches the output signal to the current interrupt circuit 13 from the Low level to the High level. As a result, the transistor (FET) Q7 of the current cut-off circuit 13 is turned on and the transistor Q8 is turned off, so that no current flows from the power supply voltage Vcc1 to the bridge circuit 15, and the current flowing from the central processing unit 1 to the transmission line is supplied. Blocked.

  As described above, the central processing unit according to the present embodiment includes a current detection circuit that detects a current flowing in a transmission line used for communication with a terminal and power supply to the terminal, and a detection result by the current detection circuit. A short circuit detection circuit that detects a short circuit of the transmission line based on the current detection circuit, and a current interrupt circuit that interrupts a current flowing through the transmission line when the short circuit detection circuit detects the short circuit. The short circuit detection circuit filters the detection result by the current detection circuit so that the detection result by the current detection circuit when the terminal transmits a response signal is not used for short circuit detection of the transmission line. Thereby, the central processing unit can shorten the time required from the occurrence of the short circuit to the detection while preventing the transmission of the response signal from the terminal device from being determined as the occurrence of the short circuit of the transmission line. In the signal transmission system according to the present embodiment, it is not necessary to provide a section for the central processing unit to detect a short circuit in the control frame. Therefore, no matter what timing the short circuit occurs, the short circuit occurs. The required time from detection to detection is constant. In addition, the control frame can be prevented from becoming longer than necessary.

  In addition, since the central processing unit according to the present embodiment includes a constant current circuit that limits a current exceeding a certain value from flowing through the transmission line, the bridge circuit includes a current amount that continues to flow when the transmission line is short-circuited. The amount of heat generated by the component on the path through which the current flows can be suppressed, and the component can be protected.

Embodiment 2. FIG.
FIG. 6 is a diagram of an example of a circuit configuration of the central processing unit according to the second embodiment. The central processing unit 1a according to the second embodiment is obtained by replacing the short circuit detection circuit 12 of the central processing unit 1 according to the first embodiment with a short circuit detection circuit 12a. Since the configuration of the central processing unit 1a is the same as that of the central processing unit 1 except for the short circuit detection circuit 12a, the description of the configuration other than the short circuit detection circuit 12a is omitted.

  The short circuit detection circuit 12a includes a filter circuit 121a and a comparator Comp1 that is a comparison circuit. A detection result output from the current detection circuit 11 is input to the non-inverting input terminal of the comparator Comp1, and a threshold for determining whether or not a transmission line short-circuit has occurred at the inverting input terminal of the comparator Comp1. A voltage Vref1, which is a value, is input. A signal output from the comparator Comp1 is input to the filter circuit 121a, and a signal output from the filter circuit 121a is input to the control circuit 17.

  The operation of the short circuit detection circuit 12a will be described. The comparator Comp1 of the short circuit detection circuit 12a compares the detection result by the current detection circuit 11 with the voltage Vref1, and determines whether or not the current value detected by the current detection circuit 11 is larger than a predetermined value. To do. For example, the comparator Comp1 outputs a High level signal when the current value detected by the current detection circuit 11 is larger than a predetermined value, and outputs a Low level signal otherwise. The comparator Comp1 outputs a low level signal when the current value detected by the current detection circuit 11 is larger than a predetermined value, and outputs a high level signal otherwise. It may be.

  When a signal is input from the comparator Comp <b> 1, the filter circuit 121 a filters the input signal by time and outputs the filtered signal to the control circuit 17. Specifically, the filter circuit 121a enters a short-circuit detection state in which the input signal from the comparator Comp1 indicates that the current value detected by the current detection circuit 11 is greater than a predetermined value, and then the short circuit is detected. When the detection state continues for a certain time, output of a signal indicating that the transmission line is short-circuited is started. The signal in the short circuit detection state is a signal indicating that the transmission line is short-circuited. That is, the filter circuit 121a receives the input signal so as to start outputting the signal indicating that the transmission line is short-circuited when the input of the signal indicating that the transmission line is short-circuited continues for a predetermined time. Filter for. The filter circuit 121a filters the time for filtering, that is, the output of the signal indicating that the transmission line is short-circuited after the input of the signal indicating that the transmission line is short-circuited to the filter circuit 121a is started. The time until the start of 121a is set to be equal to or longer than the response time of the terminal device 2 in the same manner as the filter circuit 121 described in the first embodiment. That is, the constants of the resistor R81 and the capacitor C11 of the filter circuit 121a are set based on the pulse width of the response signal transmitted by the terminal device 2.

  The central processing unit 1a according to the present embodiment can achieve the same effects as the central processing unit 1 according to the first embodiment.

  The configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

  DESCRIPTION OF SYMBOLS 1 Central processing unit, 2 Terminal device, 3 AC power supply, 11 Current detection circuit, 12 Short circuit detection circuit, 13 Current interruption circuit, 14 Drive circuit, 15 Bridge circuit, 16 Reception circuit, 17 Control circuit, 100 Signal transmission system, 111 Detection circuit, 121 filter circuit, 151, 151a, 151b constant current circuit.

Claims (7)

A central processing unit that feeds power to a terminal through two transmission lines, transmits a control signal in a voltage mode, and receives a response signal of a certain width from the terminal in a current mode,
A current detection circuit for detecting a current flowing through the terminal via the transmission line;
Based on the detection result by the current detection circuit, a short circuit detection circuit for determining the presence or absence of a short circuit of the two transmission lines;
When the short circuit detection circuit detects the short circuit, a current interrupt circuit that interrupts a current flowing through the transmission line;
With
The short circuit detection circuit is:
A filter circuit that outputs the detection result when the detection result input from the current detection circuit does not indicate a response signal from the terminal;
A comparison circuit for comparing the detection result after filtering output from the filter circuit with a threshold value;
A central processing unit. The comparison circuit outputs a signal indicating that the short circuit has occurred when the detection result after filtering is larger than the threshold value.
The central processing unit according to claim 1. The filter circuit has a current value exceeding the threshold value when a state in which a detection result output from the current detection circuit shows a current value larger than a predetermined constant value continues for a time corresponding to the predetermined width. Start outputting detection results indicating
The central processing unit according to claim 1 or 2. A central processing unit that feeds power to a terminal through two transmission lines, transmits a control signal in a voltage mode, and receives a response signal of a certain width from the terminal in a current mode,
A current detection circuit for detecting a current flowing through the terminal via the transmission line;
Based on the detection result by the current detection circuit, a short circuit detection circuit for determining the presence or absence of a short circuit of the two transmission lines;
When the short circuit detection circuit detects the short circuit, a current interrupt circuit that interrupts a current flowing through the transmission line;
With
The short circuit detection circuit is:
A comparison circuit for comparing a detection result input from the current detection circuit with a threshold value;
When the comparison result inputted from the comparison circuit becomes a short-circuit detection state indicating a state where the two transmission lines are short-circuited, and the short-circuit detection state continues for a predetermined time, the comparison circuit inputs the result. A filter circuit for outputting a comparison result;
A central processing unit. The comparison circuit outputs a comparison result corresponding to the short-circuit detection state when the detection result is greater than the threshold value.
The central processing unit according to claim 4. The fixed time is set as a time corresponding to the fixed width,
The central processing unit according to claim 4 or 5. A constant current circuit for limiting the current exceeding a certain value from flowing through the transmission line;
A central processing unit according to claim 1, comprising:

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