JP4885153B2 - Analog output terminal - Google Patents

Description

  The present invention relates to an analog output terminal that outputs an analog signal for operating an external device. In particular, the analog output terminal converts an operation amount of the external device input as a digital signal into an analog signal and outputs the analog signal to the external device. It relates to an output terminal.

  As various control systems that centrally control the operation of a plurality of external devices based on detection results from a plurality of detection devices with a single controller, a controller that performs digital processing by a computer in a controller is provided. However, since many external devices require analog input as the operation amount thereof, in such a control system, an analog output terminal that converts a digital signal output from the controller into an analog signal is connected to the controller and the external device. It is installed between.

  As such a control system, there is an air conditioning control system for controlling an air conditioner using cold water or hot water as a heat medium, which is proposed by the present applicant in Patent Document 1. This air conditioning control system will be briefly described below with reference to the block diagram shown in FIG.

  The air conditioning control system shown in FIG. 5 is provided with an air conditioner 101 that adjusts the temperature of supplied outside air, a blower 102 that determines the flow rate of air supplied from the air conditioner 101 to the room, and piping inside the air conditioner 101. Heat exchangers 103 and 104 through which hot water or cold water serving as a heat medium flows, flow rate control valves 105 and 106 that determine the flow rate of the heat medium that flows through the heat exchangers 103 and 104, an inverter 107 that rotationally drives the blower 102, and an indoor temperature The controller 108 calculates the valve opening degree of the flow rate control valves 105 and 106 and the rotation speed by the inverter 107 so that the temperature becomes a desired temperature, and the analog output terminal 109a that converts the digital signal output from the controller 108 into an analog signal. To 109c.

  In the air conditioning control system configured as described above, the air conditioner 101 heats or cools the outside air by performing heat exchange with the heat exchangers 103 and 104 on the outside air taken in from the outside air duct. At this time, the heating temperature or cooling temperature of the outside air is set according to the flow rate of the heat medium determined by the valve opening degree of the flow rate control valves 105 and 106. And the air volume exhausted indoors is set with the rotation speed in the air blower 102 rotationally driven by the inverter 107.

  Therefore, the air heated or cooled by the heat exchangers 103 and 104 inside the air conditioner 101 is supplied indoors at a flow rate determined by the blower 102. By performing these operations, when the air conditioning control system shown in FIG. 5 opens the flow control valve 105 and performs heat exchange using hot water, it operates as a heating facility, and opens the flow control valve 106 and performs heat exchange using cold water. When performing, it operates as cooling equipment.

  Further, temperature information measured by a temperature measuring device (not shown) and an actual rotational speed of the blower 102 are input to the controller 108. Based on the input temperature information, in order to set the room temperature to a desired value, an operation amount corresponding to the valve opening degree of the flow control valves 105 and 106 is calculated, and the rotation speed of the blower 102 is set to a desired value. Therefore, the operation amount for the inverter 107 that rotationally drives the blower 102 is calculated. At this time, since a digital calculation is performed in the controller 108, the operation amounts for the flow control valves 105 and 106 and the inverter 107 are output as operation signals that are digital signals.

In this way, an operation signal indicating the operation amount for the flow rate control valves 105 and 106 and the inverter 107 is output from the controller 108, but the external devices such as the flow rate control valves 105 and 106 and the inverter 107 have a voltage that becomes an analog signal. There are some whose operation is controlled by the value or current value. Therefore, the operation signal based on the digital signal output from the controller 108 is input to the analog output terminals 109a to 109c and converted into analog signals based on the voltage value or the current value, and then the flow rate control valves 105 and 106 and the inverter 107. Input to each.
JP 2002-013783 A

  As represented by the air conditioning control system of FIG. 5, in various control systems in which external devices are centrally controlled by a controller that performs digital arithmetic processing, an analog signal is transmitted to an external device whose operation is controlled by an analog signal. An analog output terminal is used for conversion into an operation signal. However, depending on the external device, there are a current control type device controlled by an analog current signal and a voltage control type device controlled by an analog voltage signal.

  For this reason, an analog output terminal for current control that can be converted into an analog current signal is adopted for an external device that becomes a current control type, and a voltage control type that can be converted into an analog voltage signal is adopted for an external device that becomes a voltage control type. Conventionally, an analog output terminal according to the control method of the external device has to be employed, such as employing an analog output terminal. However, in this case, if the analog output terminal does not support the control method of the external device, the control of the external device becomes impossible and the control system itself does not function.

  Therefore, in order to be applicable to each of current control type and voltage control type external devices, digital-analog conversion operation (hereinafter simply referred to as “DA conversion operation”) according to the control method of the connected external device. An analog output terminal that can be switched is also proposed. However, even an analog output terminal that can switch the DA conversion operation between the current method and the voltage method uses a jumper pin or the like as a means for switching, so the switching work is complicated. there were.

  Furthermore, the dynamic range by the analog voltage signal input to the voltage control type external device is 0 to 10 [V] or 0 to 5 [V], and is in the range having no offset, whereas the current control type. The dynamic range of the analog current signal input to the external device is 4 to 20 [mA], which is a range including an offset. Therefore, in the analog output terminal, it is necessary to include a voltage amplifier for converting to an analog voltage signal and a voltage / current converter for converting to an analog current signal, which hinders downsizing of the apparatus. .

  In addition, only one of the voltage amplifier and the voltage / current converter is selected as the operation unit to be operated according to the control method of the connected external device. At this time, each of the voltage amplifier and the voltage-current converter has a circuit configuration having an operational amplifier. Therefore, in an unnecessary arithmetic unit that is not selected, for example, a structure in which bias to the operational amplifier is not prohibited, wastefully consumes power. May be made.

  In view of such a problem, the present invention proposes an analog output terminal that can be applied to both external devices of voltage control type and current control type and can realize downsizing and low power consumption of the device. With the goal.

  In order to achieve the above object, the analog output terminal of the present invention converts a digital operation signal corresponding to an operation amount of an external device into an analog signal, and outputs the analog output from the output terminal to the external device. When a first external device for voltage control is connected to the output terminal, an analog voltage signal is generated as the analog signal, while a second external device for current control is connected to the output terminal. An output signal generator that generates an analog current signal as the analog signal, supplies the generated analog voltage signal or the analog current signal to the output terminal, and a first external device that performs voltage control outputs the output When connected to the terminal, a second external unit that generates an input voltage signal in accordance with the signal value of the operation signal in the first voltage range and is current controlled Is connected to the output terminal, an input voltage signal corresponding to the signal value of the operation signal is generated in a second voltage range different from the first voltage range, and the generated input voltage signal is generated as the output signal An input voltage signal generation unit for supplying to the unit, and switching the electrical switch of the analog switch provided in the output signal generation unit, the analog voltage signal and the analog current signal from the output terminal Is selectively output.

  In the analog output terminal configured as described above, the output signal generation unit includes a first operational amplifier that has two inputs and one output to which the input voltage signal from the input voltage signal generation unit is input to one input terminal; A first feedback circuit that connects between the one input terminal and the output terminal of the first operational amplifier; and a second feedback circuit that connects between the other input terminal and the output terminal of the first operational amplifier. The analog switch switches between electrical connection and separation of the first feedback circuit and circuit configuration of the second feedback circuit, and when the analog voltage signal is output, the first feedback circuit is electrically connected. When the output signal generator operates as a voltage amplifier and outputs the analog current signal, the first feedback circuit is electrically connected and the output signal generator is electrically connected. It operates as a current transformer.

  In this configuration, the first operational amplifier may be operated by a dual power supply, an offset voltage is applied to the other input terminal of the first operational amplifier, and the first operational amplifier is operated by a single power supply. It may be a thing. Further, with this configuration, the first operational amplifier can be used in common regardless of whether the output signal generator is operated by the voltage amplifier or the voltage-current converter. Thereby, it is not necessary to prepare a plurality of operational amplifiers for each of the voltage amplifier and the voltage-current converter, and the apparatus can be reduced in size.

  The first feedback circuit includes a first resistor having one end connected to the one input terminal of the first operational amplifier, an amplifier having an output connected to the other end of the first resistor, and an input of the amplifier And a second resistor having one end connected to the side. At this time, the analog switch is provided between the output side of the amplifier and the first resistor. The amplifier may be a second operational amplifier that operates with both power supplies when the first operational amplifier is used as both power supplies, and a second power amplifier that operates with a single power supply when the first operational amplifier is used as a single power supply. It may be an operational amplifier.

  The second feedback circuit includes a third resistor having one end connected to the other input terminal of the first operational amplifier, a fourth resistor having one end connected to the other end of the third resistor, A fifth resistor connected between the other end of the four resistors and the output terminal of the first operational amplifier, and a first state in which the third and fifth resistors are connected in series by the analog switch; The switching may be performed between a series circuit including the third and fourth resistors and a second state in which the fifth resistor is connected in parallel.

  Furthermore, any one of the above-described analog output terminals may include a communication interface that communicates with the outside, and the operation signal received by the communication interface may be provided to the input voltage signal generation unit.

  According to the present invention, an analog switch is provided in the output signal generation unit, and an analog voltage signal and an analog current signal can be selectively output based on electrical contact / separation of the analog switch. And current control type external devices. In addition, it is not only a switch that is directly operated by an operator, such as a conventional jumper switch, but an analog switch that is operated by an electric action, so that not only the apparatus is downsized but also the operability is improved. be able to.

<Basic configuration>
The basic configuration of the analog output terminal of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing an internal configuration of an analog output terminal according to the present invention.

  An analog output terminal 1 shown in FIG. 1 converts an operation signal value by an input digital signal into a voltage value to generate an input voltage signal, and outputs from the input voltage signal generator 2 An output signal generator 3 that generates an analog voltage signal or an analog current signal according to the input voltage signal, and an output terminal 4 that outputs the analog voltage signal or analog current signal generated by the output signal generator 3 to the external device 5; Is provided.

  For example, when the operation signal output from the controller 108 illustrated in FIG. 5 is input to the input voltage signal generation unit 2, the analog output terminal 1 configured as described above receives the output terminal 4 in the input voltage signal generation unit 2. It is converted into an input voltage signal corresponding to the analog signal to be output. In addition, since the output signal generation unit 3 performs an analog signal generation process corresponding to the control method of the external device 5, the input voltage signal generation unit 2 switches the switching instruction signal that specifies the conversion operation of the output signal generation unit 3. Is output to the output signal generator 3.

  The control method of the external device 5 may be detected by electrically notifying the input voltage signal generator 2 by operating an operation switch (not shown) or the like. Further, it may be detected by being notified by communication with the controller 108 (see FIG. 5). Further, a test signal for detecting the control method of the external device 5 may be output from the output terminal 4, and the control method of the external device 5 may be detected based on a response result to the test signal.

  Therefore, when the control method of the external device 5 is a voltage control type, an analog voltage signal without an offset is output to the external device 5, so that the input voltage signal generator 2 outputs to the output signal generator 3. A switching instruction signal is given to instruct to perform conversion to an analog voltage signal. A voltage signal having a dynamic range of 0 to V1 [V] (for example, 0 to 2 [V]) is output from the input voltage signal generation unit 2 as an input voltage signal input to the output signal generation unit 3. .

  On the other hand, when the control method of the external device 5 is a current control type, the input voltage signal generation unit 2 outputs to the output signal generation unit 3 the analog current signal having an offset to the external device 5. A switching instruction signal is given to instruct to perform conversion to an analog current signal. A voltage signal having a dynamic range of Vof to V1 [V] (for example, 0.4 to 2 [V]) is output from the input voltage signal generation unit 2 as an input voltage signal input to the output signal generation unit 3. Is done.

  By operating in this way, the conversion operation of the output signal generation unit 3 is switched according to the control method of the external device 5, and the dynamic range of the input voltage signal to the output signal generation unit 3 is switched. An analog signal corresponding to the control method of the device 5 can be output from the output terminal 4. Thereby, when the control method of the external device 5 is a voltage control type, for example, an analog voltage signal of 0 to 10 [V] or 0 to 5 [V] is output, and the control method of the external device 5 is the current. In the case of the control type, for example, an analog current signal of 4 to 20 [mA] can be output.

<Common configuration in the embodiment>
Details of the analog output terminal having the basic configuration as shown in FIG. 1 will be described in the following embodiments. In the following embodiments, the block configuration shown in FIG. 2 is provided in common. Therefore, the internal configuration of the analog output terminal according to the block diagram of FIG. 2 will be briefly described. In the analog output terminal shown in FIG. 2, parts used for the same purpose as those of the basic configuration shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  An analog output terminal 1 shown in FIG. 2 includes an output terminal 4 connected to an external device 5 (see FIG. 1), a communication interface 11 that communicates with the controller 108 shown in FIG. A control circuit 12 that performs digital processing for controlling each operation such as, photocouplers 13a and 13b that send each signal obtained and output by arithmetic processing by the control circuit 12 to the subsequent stage as an optical signal, and a photocoupler A DAC (Digital to Analog Converter) 14 for performing DA conversion connected to 13a, a switching circuit 15 connected to the photocoupler 13b, and an output signal for converting a voltage signal from the DAC 14 into an analog signal output from the output terminal 4. The power generation circuit 30, the power supply circuit 16 a that supplies power to the communication interface 11 and the control circuit 12, and the DAC 1 , And a power supply circuit 16b for supplying power to the switching circuit 15 and an output signal generating circuit 30.

  The analog output terminal 1 includes a communication interface 11, a control circuit 12, light emitting diodes LD1 and LD2 of photocouplers 13a and 13b, and a power supply circuit 16a. A digital processing block 10x that is operated by a voltage equivalent to the above is configured. 2 is digitally processed by the output terminal 4, the phototransistors PT1 and PT2, the DAC 14, the switching circuit 15, the power supply circuit 16b, and the output signal generation circuit 30 of the photocouplers 13a and 13b. An analog processing block 10y electrically separated from the block 10x is configured. In order to perform this electrical divergence, for example, the digital processing block 10x and the analog processing block 10y can be configured on different substrates.

  In this way, by electrically separating the digital processing block 10x and the analog processing block 10y by insulation or the like, each circuit constituting the digital processing block 10x due to the occurrence of overvoltage or overcurrent in the analog processing block 10y The element can be prevented from being destroyed. Thereby, it is possible to prevent an electrical influence given to the controller 108 from the analog processing block 10y side. In the configuration example shown in FIG. 2, the digital processing block 10x and the analog processing block 10y are insulated from each other. However, such insulation may not be provided.

  Then, when an external power supply having a voltage V (for example, +24 [V]) is input to each of the power supply circuits 16a and 16b, the power supply circuit 16a in the digital processing block 10x has the operating voltage Vx (for example, +3.3 [for example +3.3 [V]). V]) and output, and in the analog processing block 10y, the power supply circuit 16b converts to an operating voltage ± Vy or + Vy (for example, ± 15 [V] or +15 [V]) higher than the operating voltage Vx and outputs To do. Note that a voltage conversion operation may be performed on the switching circuit 15 by the power supply circuit 16b to apply a voltage Vz (for example, +5 [V]) lower than Vy. Further, the communication interface 11, the control circuit 12, the photocouplers 13a and 13b, the DAC 14, and the switching circuit 15 constitute the input voltage signal generation unit 2 in the basic configuration of FIG. This corresponds to the output signal generation unit 3 in the basic configuration.

  The operation of the analog output terminal 1 having such a configuration will be described below. When an operation signal from the controller 108 received by the communication interface 11 is given to the control circuit 12, the control circuit 12 converts the operation signal into a digital signal to be processed by the DAC 14, and outputs the digital signal to the photocoupler 13a. The control circuit 12 generates a switching control signal that is a digital signal according to the control method of the external device 5 (see FIG. 1), and outputs the switching control signal to the photocoupler 13b.

  In the photocoupler 13a, light emission of the light emitting diode LD1 is controlled according to the digital signal output from the control circuit 12, and the phototransistor PT1 operates according to the light emission operation of the light emitting diode LD1. Accordingly, the phototransistor PT1 of the photocoupler 13a is turned on / off according to the digital signal output from the control circuit 12, and the digital signal from the control circuit 12 is input to the DAC.

  The photocoupler 13a is composed of a plurality of photocoupler groups corresponding to the number of bits of the digital signal. Then, only the light emitting diode of the photocoupler corresponding to the digit that is 1 in the digital signal output from the control circuit 12 emits light, and the light emitting diode and the phototransistor forming the photocoupler are made conductive. By using the photocoupler 13a including a plurality of photocoupler groups corresponding to the number of bits of the digital signal, a digital signal having a plurality of bits can be transmitted from the control circuit 12 to the DAC 14.

  On the other hand, in the photocoupler 13b, the light emission of the light emitting diode LD2 is controlled according to the switching instruction signal output from the control circuit 12, and the phototransistor PT2 operates according to the light emission operation of the light emitting diode LD2. Thus, according to the switching instruction signal output from the control circuit 12, the phototransistor PT2 of the photocoupler 13b is turned on / off, and the switching instruction signal from the control circuit 12 is input to the switching circuit 15. At this time, for example, the light emitting diode LD2 may emit light when the voltage control method is used, and the light emission of the light emitting diode LD2 may be stopped when the current control method is used.

  In addition, when the control circuit 12 converts the operation signal input from the communication interface 11 into a digital signal output to the photocoupler 13a, the dynamic range of the converted digital signal is converted to that of the external device 5 (see FIG. 1). Change according to the control method. That is, when an analog voltage signal without an offset is output, the dynamic range of the digital signal is set to a range of 0 to L, and when an analog current signal with an offset is output, the dynamic range of the digital signal is set to a range of Lo to L. And

  Therefore, when the dynamic range of the operation signal input to the control circuit 12 is in the range of 0 to Lx, the control circuit 12 outputs a value ( When outputting a digital signal of (L1 × L / Lx) and outputting an analog current signal, a digital signal of a value (Lo + L1 × (L−Lo) / Lx) is output. In this way, a digital signal having a dynamic range corresponding to the control method of the external device 5 (see FIG. 1) is input to the DAC 14 via the photocoupler 13a.

  The DAC 14 performs DA conversion processing on a digital signal input via the photocoupler 13a, and outputs an analog signal obtained after DA conversion to the output signal generation circuit 30 as an input voltage signal. That is, the DAC 14 generates an analog voltage signal with a voltage value corresponding to the value of the digital signal, and outputs the analog voltage signal to the output signal generation circuit 30 as an input voltage signal. When an analog voltage signal is output from the output terminal 4 by DA conversion processing of the DAC 14, an input voltage signal having a dynamic range of 0 to V1 [V] (for example, 0 to 2 [V]) is output signal generation circuit. On the other hand, when an analog current signal is output from the output terminal 4, an input voltage signal whose dynamic range is Vof to V1 [V] (for example, 0.4 to 2 [V]) is output as an output signal. Input to the generation circuit 30.

  That is, when an analog voltage signal is output and a digital signal having a value (L1 × L / Lx) is input, the analog voltage signal having a value (L1 × V1 / Lx) is input to the input voltage. Output as a signal. On the other hand, when a digital signal having a value (Lo + L1 × (L−Lo) / Lx) is input when an analog current signal is output, the value (Vof + L1 × (V1−Vof) / Lx) is obtained. The analog voltage signal is output as an input voltage signal.

  The switching circuit 15 is an analog switch (to be described later in the first and second embodiments) in the output signal generation circuit 30 based on a switching instruction signal input from the control circuit 12 via the photocoupler 13b. The circuit configuration of the output signal generation circuit 30 is designated by switching between electrical contact and separation. That is, when the input switching instruction signal instructs the output terminal 4 to output an analog voltage signal, the output signal generation circuit 30 is switched to a circuit configuration that becomes a voltage amplifier, while the inputted switching instruction signal When the signal instructs the output terminal 4 to output an analog current signal, the output signal generation circuit 30 is switched to a circuit configuration that becomes a voltage-current converter.

  Thus, the output signal generation circuit 30 operates based on the circuit configuration specified by the switching circuit 15, performs voltage amplification or current-voltage conversion on the input voltage signal output from the DAC 14, and sets the output terminal 4. An analog voltage signal or an analog current signal is output to the external device 5 (see FIG. 1). The first and second embodiments of the analog output terminal having the above-described configuration and operation in common will be described in detail with respect to the output signal generation circuit that is a feature of each embodiment.

<First Embodiment>
A first embodiment of the present invention will be described with reference to FIG. FIG. 3 is a circuit diagram showing the configuration of the output signal generation circuit built in the analog output terminal of this embodiment.

  As shown in FIG. 3, an output signal generation circuit 30a (corresponding to the output signal generation circuit 30 in FIG. 2) provided in the analog output terminal of this embodiment is an input terminal to which an input voltage signal from the DAC 14 is input. IN, a resistor R6 having one end grounded, a resistor R7 having one end connected to the input terminal IN, and an inverting input terminal (−) and a non-inverting input terminal (+) at the other ends of the resistors R6 and R7, respectively. Are connected to each other and the operational amplifier A1 operates with both power sources, the npn transistor Tr1 whose base is connected to the output terminal of the operational amplifier A1, the resistor R5 whose one end is connected to the emitter of the transistor Tr1, and the resistor R5. Resistors R1 and R2 and an operational amplifier A2 constituting a first feedback circuit between the terminal and the non-inverting input terminal of the operational amplifier A1, and the other end of the resistor R5 and the inverse of the operational amplifier A1 Comprises a resistor R3, R4 constituting the second feedback circuit between the analog switches SW1~SW3 an electrical contact and separation by the switching circuit 15 is controlled - Power terminal ().

  In the first feedback circuit, one end of the analog switch SW1 is connected to the other end of the resistor R1 whose one end is connected to the non-inverting input terminal of the operational amplifier A1, and one end is connected to the other end of the resistor R5. The other end of the resistor R2 is connected to the non-inverting input terminal (+) of the operational amplifier A2 in which the output terminal and the inverting input terminal (−) are connected to the other end of the analog switch SW1. At this time, the operational amplifier A2 operates with both power sources similarly to the operational amplifier A1, and functions as an amplifier by connecting the output terminal and the inverting input terminal.

  In the second feedback circuit, one end of each of the resistor R4 and the analog switch SW2 is connected to the other end of the resistor R3 connected to the inverting input terminal of the operational amplifier A1, and one end is connected to the other end of the resistor R5. The other end of the resistor R4 having one end connected to the connection node between the resistor R3 and the analog switch SW2 is connected to the other end of the connected analog switch SW3. Furthermore, the other end of the analog switch SW2 is connected to a connection node between the resistor R5 and the emitter of the transistor Tr1.

  Then, ± Vy (for example, ± 15 V) is supplied as a bias voltage from the power supply circuit 16b (see FIG. 2) to each of the operational amplifiers A1 and A2 that operate with the above-described two power supplies. Further, the output terminal 4 is formed by the contact point of the output signal generation circuit 30a with the connection node of the resistors R2 and R5 and the ground point.

  In such a configuration, when the external device 5 (see FIG. 1) operates by voltage control, the analog switch SW1 and SW2 are turned off by the switching circuit 15 and the analog switch SW3 is turned on. That is, when the analog switch SW1 is turned off, the connection of the first feedback circuit is disconnected, and when the analog switch SW2 is turned off and the analog switch SW3 is turned on, the second feedback circuit is configured by a series circuit of resistors R3 and R4. Therefore, the output signal generation circuit 30a functions as a voltage amplifier.

Thus, an analog voltage signal having a voltage value (Vin × {1+ (r3 + r4) / r6}) with respect to the voltage value Vin of the input voltage signal by the resistance values r3, r4, r6 of the resistors R3, R4, R6, respectively. Can be output. Therefore, for example, when the dynamic range of the input voltage signal is 0 to 2 [V] and the dynamic range of the analog voltage signal is 0 to 10 [V], the resistance values r3 and r4 of the resistors R3, R4, and R6, respectively. , R6 may be set to values satisfying the relationship of the following expression (1).
1+ (r3 + r4) / r6 = 5 (1)

  On the other hand, when the external device 5 (see FIG. 1) operates by current control, the analog switch SW1 and SW2 are turned on by the switching circuit 15, and the analog switch SW3 is turned off. That is, when the analog switch SW1 is turned on, the first feedback circuit is electrically connected, and when the analog switch SW2 is turned on and the analog switch SW3 is turned off, the resistor R3 in the second feedback circuit forms a series circuit with the resistor R5. . Therefore, the output signal generation circuit 30a functions as a voltage / current converter.

  Thus, an analog current that becomes a current value ({Vin × (1 + r3 / r6)} / r5) with respect to the voltage value Vin of the input voltage signal by the resistance values r3, r5, and r6 of the resistors R3, R5, and R6, respectively. A signal can be output. Therefore, for example, when the dynamic range of the input voltage signal is 0.4 to 2 [V] and the dynamic range of the analog current signal is 0.4 to 2 [mA], the resistance value of the resistor R5 is set to 100 [Ω. And the resistance value r6 of the resistor R6 may be set to a value sufficiently larger than the resistance value r3 of the resistor R3.

  As described above, in this embodiment, the output signal generation circuit 30a that can switch the circuit configuration to the current amplifier or the voltage-current converter by providing the analog switches SW1 to SW3 is configured by the two operational amplifiers A1 and A2. Therefore, the output signal generation circuit 30a can be downsized. Also, by setting the resistance values of the resistors R3 to R6 to predetermined values, the input voltage signal input from the DAC 14 is converted into a desired analog voltage signal or analog current signal and output to the output terminal 4. Can do.

<Second Embodiment>
A second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a circuit diagram showing a configuration of an output signal generation circuit built in the analog output terminal of this embodiment. In the output signal generation circuit shown in FIG. 4, elements or parts used for the same purpose as those of the output signal generation circuit shown in FIG.

  An output signal generation circuit 30b (corresponding to the output signal generation circuit 30 in FIG. 2) provided in the analog output terminal of the present embodiment is different from the first output signal generation circuit 30a (see FIG. 3). By adopting a configuration in which the voltage Vk is applied to one end of the resistor R6 grounded in the circuit configuration, the operational amplifiers A1 and A2 are operated by a single power source biased by a voltage + Vy (for example, + 15V). Since other configurations are the same as those in the first embodiment, the details thereof are omitted.

  In the state where one end of the resistor R6 is grounded as in the first embodiment, if the operational amplifier A1 is not operated with both power sources, the other end of the resistor R5 connected to the output terminal 4 is set to 0 [V]. A voltage value of 0 [V] corresponding to the input voltage signal cannot be output. Therefore, in the present embodiment, as described above, by applying the offset voltage Vk to the resistor R6, the other end of the resistor R5 connected to the output terminal 4 even if the operational amplifier A1 is operated with a single power source. Is configured to output a voltage value of 0 [V] corresponding to an input voltage signal of 0 [V].

  Therefore, in the first embodiment, since the positive and negative voltages ± Vy are respectively supplied from the power supply circuit 16b, the power supply circuit 16b has a circuit configuration that generates the positive and negative voltages ± Vy from the power supplied from the outside. Although the scale is large, in this embodiment, it is sufficient to supply the positive voltage + Vy from the power supply circuit 16b. Therefore, the circuit scale of the power supply circuit 16b can be reduced as compared with the first embodiment. In order to generate the voltage Vk, it is only necessary to configure a transformer circuit, which is smaller than the circuit scale of the power supply circuit that generates the negative voltage -Vy.

  The present invention is not limited to an air conditioning control system, and can be applied to other control systems as long as the control system can operate an external device by a controller that performs central management.

These are block diagrams which show the basic composition of the analog output terminal of this invention. These are block diagrams which show the structure of the analog output terminal in the 1st and 2nd embodiment of this invention. These are circuit diagrams which show the circuit structure of the output signal generation circuit of the analog output terminal in the 1st Embodiment of this invention. These are circuit diagrams which show the circuit structure of the output signal generation circuit of the analog output terminal in the 2nd Embodiment of this invention. These are block diagrams which show the structure of the air-conditioning control system using an analog output terminal device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Analog output terminal 2 Input voltage signal generation part 3 Output signal generation part 4 Output terminal 5 External apparatus 10x Digital processing block 10y Analog processing block 11 Communication interface 12 Control circuit 13a, 13b Photocoupler 14 DAC
15 switching circuit 16a, 16b power supply circuit 30, 30a, 30b output signal generation circuit R1-R7 resistor A1, A2 operational amplifier SW1-SW3 analog switch Tr1 transistor

Claims (4)

An analog output terminal that converts a digital operation signal corresponding to an operation amount of an external device into an analog signal and outputs the analog signal from the output terminal to the external device,
When a first external device for voltage control is connected to the output terminal, an analog voltage signal is generated as the analog signal, while when a second external device for current control is connected to the output terminal, an analog current is generated. An output signal generator for generating a signal as the analog signal, and supplying the generated analog voltage signal or the analog current signal to the output terminal;
When a first external device for voltage control is connected to the output terminal, an input voltage signal corresponding to the signal value of the operation signal is generated in the first voltage range, while a second external device for current control is generated. Is connected to the output terminal, an input voltage signal corresponding to the signal value of the operation signal is generated in a second voltage range different from the first voltage range, and the generated input voltage signal is generated as the output signal An input voltage signal generation unit to be supplied to the unit;
With
An analog output terminal that selectively outputs the analog voltage signal and the analog current signal from the output terminal by switching electrical contact and separation of an analog switch provided in the output signal generation unit vessel. In claim 1,
The output signal generator is
A first operational amplifier that has two inputs and one output, and the input voltage signal from the input voltage signal generator is input to one input terminal;
A first feedback circuit connecting between the one input terminal and the output terminal of the first operational amplifier;
A second feedback circuit connecting the other input terminal and the output terminal of the first operational amplifier;
Have
The analog switch switches between electrical connection and separation of the first feedback circuit and circuit configuration of the second feedback circuit,
When outputting the analog voltage signal, the first feedback circuit is electrically disconnected and the output signal generation unit operates as a voltage amplifier,
When outputting the analog current signal, the first feedback circuit is electrically connected, and the output signal generator operates as a voltage-current converter. In claim 1 or claim 2,
An analog output terminal characterized in that an offset voltage is applied to the other input terminal of the first operational amplifier, and the first operational amplifier operates with a single power source. In any one of Claims 1 thru | or 3,
It has a communication interface that communicates with the outside,
The analog output terminal device, wherein the operation signal received by the communication interface is provided to the input voltage signal generation unit.

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