Current output device

Abstract

To simplify a current output device.SOLUTION: A current output device includes a plurality of current output units, a substitute current generation unit, a signal conversion unit, and an output current correction unit. The current output unit outputs an output current based on an input output-current signal to an external circuit. The substitute current generation unit generates a substitute current that is a current substituting for the output current of the current output unit, based on a resistor disposed in the same integrated circuit as the current output unit. The signal conversion unit converts the substitute current into a voltage signal, based on a reference resistance. The output current correction unit is disposed for each current output unit and generates an output current signal, based on a difference between the voltage signal and a target value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a current output device. [Background technology]

[0002] Conventionally, current output devices have been used in plants and factories to supply a predetermined current used for signal transmission, etc., to field devices, etc. For example, a current output module has been proposed that uses a reference resistor to generate a voltage corresponding to an output current, compares the voltage with a reference voltage, and controls the output current based on the comparison result (see, for example, Patent Document 1).

[0003] The above-mentioned current output module uses a reference resistor to detect the output current, and this reference resistor is required to have a relatively high accuracy in order to reduce errors when detecting the output current. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-141251 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned conventional technology has a problem that when applied to a multi-channel current output device that simultaneously outputs multiple currents, a highly accurate reference resistor is required for each channel, which results in an increase in costs.

[0006] The present disclosure provides a technique for simplifying a current output device that stabilizes a plurality of output currents. [Means for solving the problem]

[0007] The current output device of the present disclosure has a plurality of current output sections, a substitute current generation section, a signal conversion section, and an output current correction section. The current output section outputs an output current based on an input output current signal to an external circuit. The substitute current generation section generates a substitute current that substitutes for the output current of the current output section based on a resistor arranged in the same integrated circuit as the current output section. The signal conversion section converts the substitute current into a voltage signal based on a reference resistor. The output current correction section is arranged for each current output section, and generates the output current signal based on a difference between the voltage signal and a target value. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an example of the configuration of a current output device according to a first embodiment of the present disclosure. [Diagram 2] 3 is a diagram illustrating a configuration example of a current output section according to the first embodiment of the present disclosure. FIG. [Diagram 3] 11 is a diagram illustrating an example of the configuration of a current output device according to a second embodiment of the present disclosure. FIG. [Figure 4] FIG. 11 is a diagram illustrating a configuration example of an alternative current generating unit according to a second embodiment of the present disclosure. [Diagram 5] 13 is a diagram illustrating an example of the configuration of a current output device according to a third embodiment of the present disclosure. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The description will be given in the following order. In the following embodiments, the same components are designated by the same reference numerals, and duplicated description will be omitted. 1. First embodiment 2. Second embodiment 3. Third embodiment

[0010] 1. First Embodiment [Configuration of current output device] FIG. 1 is a diagram showing a configuration example of a current output device according to a first embodiment of the present disclosure. The figure is a block diagram showing a configuration example of a current output device 1. The current output device 1 outputs current to a plurality of field devices individually. The current output device 1 in the figure has a four-channel current output section. Field devices 2 to 5 are shown in the figure. The current output device 1 can output a predetermined current to the field devices 2 to 5 individually.

[0011] The current output device 1 includes a control unit 10 and a current output module 20. The control unit 10 controls the output current of the current output module 20. The control unit 10 outputs output current signals (DOUT1 to DOUT4 in the figure) that are control signals for each channel of the current output module 20. The control unit 10 also performs feedback control based on a current (a substitute current, described later) corresponding to the output current for each channel from the current output module 20 to stabilize the output current of the current output module 20.

[0012] Moreover, the current output module 20 generates a current for each channel and outputs it to the field device 2 and the like via the output terminal. The current output module 20 in the figure includes an output terminal 210, an output terminal 220, an output terminal 230, and an output terminal 240. The output terminal 210 is connected to the field device 2 and supplies a current (IOUT1). The output terminal 220 is connected to the field device 3 and supplies a current (IOUT2). The output terminal 230 is connected to the field device 4 and supplies a current (IOUT3). The output terminal 240 is connected to the field device 5 and supplies a current (IOUT4). Moreover, the current output module 20 has current output sections (such as a current output section 320 described later) corresponding to each of these output terminals 210-240. The current output sections 320 and the like are connected to the output terminals 210 and the like. For example, one end of the output terminal 210 is connected to the current output section 320, and the other end of the output terminal 210 is connected to a common GND.

[0013] The control unit 10 includes a plurality of output current correction units (output current correction units 101 to 104), a reference resistor 110, an analog-to-digital conversion unit 120, and a selection control unit 268. In the figure, the "analog conversion unit" is written as "A / D."

[0014] The output current correction units 101, etc. are arranged for each channel and output an output current signal, which is a control signal, based on the difference between a voltage signal (DIN) corresponding to the output current of the channel to which they correspond and a target value. In the figure, "ISET1", "ISET2", "ISET3", and "ISET4" respectively represent the target values ​​of the output current correction units 101 to 104. Also, "DOUT1", "DOUT2", "DOUT3", and "DOUT4" respectively represent the output current signals of the output current correction units 101 to 104. The output current correction units 101, etc. in the figure generate digital output current signals. The output current correction units 101, etc. control the current output units 320, etc. so as to reduce the difference between the voltage signal (DIN) corresponding to the output current and the target value.

[0015] The reference resistor 110 converts the substitute current (IVAL) output from the current output module 20 into a voltage signal (VVAL). Here, the substitute current is a current that corresponds to the output current of the current output section 320 or the like, and is a current that substitutes for the output current. A voltage signal (VVAL) can be generated by passing this substitute current through the reference resistor 110. The circuit of the reference resistor 110 is an example of a "signal conversion section" in this disclosure.

[0016] The analog-to-digital conversion section 120 performs analog-to-digital conversion on the above-mentioned voltage signal (VVAL) to generate a voltage signal (DIN).

[0017] The selection control unit 268 controls the selection of the alternative current in the current output module 20. The above-mentioned alternative current is generated for each of the current output units 320-350. One of the multiple alternative currents is selected and output from the current output module 20. The selection control unit 268 controls the selection of this alternative current.

[0018] The current output module 20 includes the output terminals 210-240, a plurality of digital-analog conversion units (digital-analog conversion units 311 to 314), and a plurality of current output units (current output unit 320, current output unit 330, current output unit 340, and current output unit 350). The current output module 20 further includes a plurality of alternative current generation units (alternative current generation unit 390 described below) and switch elements 261, 262, 265, and 266. The current output units 320 and 330, the digital-analog conversion units 311 and 312, and the switch elements 261 and 262 are disposed in the integrated circuit 30. The current output units 340 and 350, the digital-analog conversion units 313 and 314, and the switch elements 265 and 266 are disposed in the integrated circuit 31.

[0019] The digital-analog conversion unit 311 and the like convert the digital output current signal output from the output current correction unit 101 and the like into an analog output current signal. The converted output current signal is output to the current output unit 320 and the like. Specifically, the digital-analog conversion unit 311 converts DOUT1 into an analog signal and outputs it to the current output unit 320. The digital-analog conversion unit 312 converts DOUT2 into an analog signal and outputs it to the current output unit 330. The digital-analog conversion unit 313 converts DOUT3 into an analog signal and outputs it to the current output unit 340. The digital-analog conversion unit 314 converts DOUT4 into an analog signal and outputs it to the current output unit 350. The digital-analog conversion units 311 and 312 can also be arranged outside the integrated circuit 30. Similarly, the digital-analog conversion units 313 and 314 can also be arranged outside the integrated circuit 31.

[0020] The current output units 320, etc. generate an output current based on the output current signal, and output it to the field device 2, etc. via the output terminal 210, etc. Specifically, the current output unit 320 outputs a current via the output terminal 210. The current output unit 330 outputs a current via the output terminal 220. The current output unit 340 outputs a current via the output terminal 230. The current output unit 350 outputs a current via the output terminal 240. In addition, the current output units 320, etc. each generate a substitute current for their own output current. The configuration of the current output units 320, etc. will be described in detail later.

[0021] The switch element 261 and the like are switches that are arranged on a signal line to which an alternative current is supplied and output the alternative current. Specifically, the switch element 261 corresponds to the alternative current of the current output section 320, the switch element 262 corresponds to the alternative current of the current output section 330, the switch element 265 corresponds to the alternative current of the current output section 340, and the switch element 266 corresponds to the alternative current of the current output section 350. By turning on any of these switch elements 261 and the like, an alternative current can be selected. The selected alternative current is output from the current output module 20 as the above-mentioned IVAL. The above-mentioned selection control section 268 controls the conduction of the switch elements 261, 262, 265, and 266. A MOS transistor can be applied to the switch element 261 and the like. The selection control section 268 and the circuits of the switch elements 261, 262, 265, and 266 are an example of the "selection section" of the present disclosure.

[0022] The substitute current of the channel selected by the selection control unit 268 and the switch element 261, etc. is fed back to the corresponding output current correction unit 101, etc. via the reference resistor 110 and the analog-to-digital conversion unit 120, and the output current is corrected. By performing this sequentially for all channels, the accuracy of the output currents IOUT1-IOUT4 can be improved.

[0023] [Current output section configuration] 2 is a diagram showing a configuration example of a current output section according to the first embodiment of the present disclosure. The figure is a circuit diagram showing a configuration example of a current output section 320. Note that the current output section 330 and the like can also have a similar configuration.

[0024] The current output unit 320 includes an operational amplifier 321, a resistor 322, and MOS transistors 323 to 326. An n-channel MOS transistor can be used as the MOS transistor 323. Furthermore, p-channel MOS transistors can be used as the MOS transistors 324 to 326. Furthermore, a power supply line Vdd is provided in the current output unit 320.

[0025] A signal line from the digital-to-analog conversion unit 311 is connected to a non-inverting input of an operational amplifier 321. An output of the operational amplifier 321 is connected to a gate of a MOS transistor 323. A source of the MOS transistor 323 is connected to an inverting input of the operational amplifier 321 and one end of a resistor 322. The other end of the resistor 322 is connected to a common GND. A drain of the MOS transistor 323 is connected to a drain of a MOS transistor 324. A gate of the MOS transistor 323 is connected to a source of the MOS transistor 324, a gate of a MOS transistor 325, a gate of a MOS transistor 326, and a power supply line Vdd. A source of the MOS transistor 325 is connected to the power supply line Vdd, and a drain is connected to a wiring to the switch element 261. A source of the MOS transistor 326 is connected to the power supply line Vdd, and a drain is connected to a wiring to the output terminal 210.

[0026] The operational amplifier 321, the MOS transistor 323, and the resistor circuit constitute a voltage-current conversion circuit. A current corresponding to the output current signal from the digital-to-analog conversion unit 311 is generated based on the resistor 322, and is output as a drain current of the MOS transistor 323.

[0027] The MOS transistor 324 and the MOS transistor 326 form a current mirror circuit. The gate of the MOS transistor 324 is connected to its own source. The drain current of the MOS transistor 324 is mirrored to the MOS transistor 326 as a reference current. This reference current corresponds to the drain current of the MOS transistor 323. Therefore, the drain current of the MOS transistor 326 is a current based on the output current signal. By making the channel sizes of the MOS transistor 324 and the MOS transistor 326 equal, the mirror ratio can be made 1:1. The MOS transistor 324 is an example of a "first transistor" in the present disclosure. The MOS transistor 326 is an example of a "second transistor" in the present disclosure.

[0028] Moreover, a MOS transistor 325 is further connected to the above-mentioned current mirror circuit. The reference current is also mirrored to this MOS transistor 325. Therefore, the drain current of the MOS transistor 325 is also a current based on the output current signal. Furthermore, the drain current of the MOS transistor 326 and the drain current of the MOS transistor 325 are currents with a ratio according to their respective channel sizes, etc. Therefore, the drain current of the MOS transistor 325 can be used as a substitute for the drain current of the MOS transistor 326, i.e., the output current. By changing the channel size of the MOS transistor 325 relative to the channel size of the MOS transistor 324, a substitute current with a desired ratio can be generated. In this way, the substitute current can be generated by the circuit of the MOS transistor 325. Note that the circuit including the MOS transistor 325 is an example of the "substitute current generating unit" of the present disclosure. The MOS transistor 325 is an example of the "third transistor" of the present disclosure.

[0029] In this way, the alternative current can be generated based on the resistor 322. The resistor 322 is also disposed in the other current output units 330, etc., so that the alternative current can be generated for each of the current output units 320-350. The resistor 322 is a resistor formed in the integrated circuit 30, etc., so that the variation in the resistance value of each resistor 322 for each current output unit 320 is small. Therefore, feedback control can be performed using the alternative current instead of the output current. Furthermore, the output current and the alternative current contain errors based on the variation in the resistor 322. However, these errors can be reduced (compressed) by the action of a feedback control system including the circuit of the reference resistor 110 in FIG. 1. Note that in order to reduce errors in the feedback control system, it is necessary to use a high-precision resistor for the reference resistor 110 in FIG. 1. However, high-precision resistors are not necessary for the multiple resistors 322. Therefore, the increase in cost of the current output device 1 can be reduced.

[0030] Moreover, the current output device 1 selects an alternative current from a plurality of current output sections 320, etc., by a circuit such as the switch element 261, and inputs the selected alternative current to the reference resistor 110 circuit and the analog-digital conversion section 120. Therefore, the configuration of the current output device 1 can be simplified compared to a case where the reference resistor 110 circuit and the analog-digital conversion section 120 are provided for each channel. This makes it possible to reduce an increase in the cost of the current output device 1.

[0031] 2. Second Embodiment The current output device 1 of the first embodiment described above generates an alternative current based on the resistor 322 arranged in the current output section 320. In addition, since feedback control is performed that includes the digital-to-analog converter 311 and the like in the loop, there is a problem that the response speed is relatively slow. In contrast, the current output device 1 of the second embodiment of the present disclosure differs from the first embodiment described above in that an alternative current is generated based on a resistor arranged in the integrated circuit 30 and the like.

[0032] [Configuration of current output device] Fig. 3 is a diagram showing a configuration example of a current output device according to a second embodiment of the present disclosure. Similar to Fig. 1, the diagram is a block diagram showing a configuration example of a current output device 1. The current output device 1 in the diagram differs from the current output device 1 in Fig. 1 in that it includes switch elements 263 and 267 and alternative current generating units 360 and 370 instead of switch elements 261, 262, 265, and 266.

[0033] The alternative current generating units 360 and 370 generate an alternative current, similar to the alternative current generating unit 390 in Fig. 2. The alternative current generating units 360 and the like generate an alternative current based on their own resistance. The alternative current generating unit 360 is disposed in the integrated circuit 30, and the alternative current generating unit 370 is disposed in the integrated circuit 31. Note that in the integrated circuit 30, the current output units 320 and 330 and the alternative current generating unit 360 are assumed to be configured on the same semiconductor chip. Similarly, in the integrated circuit 31, the current output units 340 and 350 and the alternative current generating unit 370 are assumed to be configured on the same semiconductor chip.

[0034] The switch elements 263 and 267 are switches that are arranged on a signal line to which an alternative current is supplied and output the alternative current. Specifically, the switch element 263 corresponds to the alternative current of the alternative current generating unit 360, and the switch element 267 corresponds to the alternative current of the alternative current generating unit 370.

[0035] It should be noted that the alternative current generating section 390 can be omitted from the current output section 320 in the figure.

[0036] [Configuration of alternative current generation unit] 4 is a diagram showing a configuration example of a substitute current generating unit according to a second embodiment of the present disclosure. The figure is a circuit diagram showing a configuration example of a substitute current generating unit 360. The substitute current generating unit 370 can also have a similar configuration.

[0037] The alternative current generating unit 360 includes an operational amplifier 361, a resistor 362, MOS transistors 363 to 365, and a voltage source 369. An n-channel MOS transistor can be applied to the MOS transistors 363. A p-channel MOS transistor can be applied to the MOS transistors 364 and 365. In addition, a power supply line Vdd is disposed in the alternative current generating unit 360.

[0038] The low potential terminal of the voltage source 369 is connected to a common GND, and the high potential terminal is connected to the non-inverting input of the operational amplifier 361. The output of the operational amplifier 361 is connected to the gate of the MOS transistor 363. The source of the MOS transistor 363 is connected to the inverting input of the operational amplifier 361 and one end of a resistor 362. The other end of the resistor 362 is connected to a common GND. The drain of the MOS transistor 363 is connected to the drain of the MOS transistor 364. The gate of the MOS transistor 364 is connected to the source of the MOS transistor 364, the gate of the MOS transistor 365, and the power supply line Vdd. The source of the MOS transistor 365 is connected to the power supply line Vdd, and the drain is connected to a wiring to the switch element 263.

[0039] The MOS transistors 364 and 365 constitute a current mirror circuit. The circuit of the operational amplifier 361, the MOS transistor 363, and the resistor 362 constitute a voltage-current conversion circuit. The output voltage of the voltage source 369 corresponds to a reference voltage. The drain current of the MOS transistor 363 is a current based on the voltage of the voltage source 369 and the resistor 362. This drain current becomes a reference current of the current mirror circuit and is mirrored to the MOS transistor 365. This drain current of the MOS transistor 365 is output as a substitute current. The resistor 362 is a resistor disposed in the same integrated circuit 30 as the resistor 322 of the substitute current generating unit 360, and therefore has the same characteristics as the resistor 322. Specifically, the resistance value variation of the resistors 362 and 322 is small. Furthermore, the resistance value changes due to temperature drift of the resistors 362 and 322 are approximately equal. Therefore, the current based on the resistor 362 can be used as the substitute current instead of the substitute current based on the resistor 322.

[0040] In this way, the alternative current can be generated based on the resistor 362. Since the resistor 362 does not need to be a highly accurate resistor, the increase in the cost of the current output device 1 can be reduced. In addition, the alternative current from the integrated circuit 30 or the like is selected by the circuits of the switch elements 263 and 267 and input to the circuit of the reference resistor 110 and the analog-digital conversion unit 120. Therefore, compared to the case where the circuit of the reference resistor 110 and the analog-digital conversion unit 120 are arranged for each channel, the configuration of the current output device 1 can be simplified. In addition, compared to the current output device 1 of FIG. 1, since the digital-analog conversion unit 311 is not included in the control system, the current output device 1 of the third embodiment of the present disclosure can improve the response speed.

[0041] Other than this, the configuration of the current output device 1 is similar to the configuration of the current output device 1 in the first embodiment of the present disclosure, and therefore a description thereof will be omitted.

[0042] 3. Third embodiment A modification of the current output device 1 of the above-mentioned first embodiment will be described.

[0043] [Configuration of current output device] 5 is a diagram showing a configuration example of a current output device according to a third embodiment of the present disclosure. The same figure is a block diagram showing a configuration example of a current output device 1, similar to FIG. 1. The current output device in the same figure 1 in that it further includes switch elements 263 and 267 and alternative current generating units 360 and 370.

[0044] The current output device 1 in the figure includes the alternative current generating unit 390 and the alternative current generating units 360 and 370 in Fig. 2. Therefore, the current output device 1 in the figure can select and use the alternative currents generated by the alternative current generating unit 390 and the alternative current generating units 360 and 370. For example, when controlling the output current with relatively high accuracy, the alternative current from the alternative current generating unit 390 arranged for each current output unit 320 can be selected, and when a relatively high-speed response is required, the alternative current from the alternative current generating unit 360 or the like can be selected.

[0045] Other than this, the configuration of the current output device 1 is similar to the configuration of the current output device 1 in the first embodiment of the present disclosure, and therefore a description thereof will be omitted.

[0046] Although the embodiments of the present disclosure have been described above, the technical scope of the present disclosure is not limited to the above-described embodiments as they are, and various modifications are possible without departing from the gist of the present disclosure. In addition, components of different embodiments and modifications may be appropriately combined.

[0047] It should be noted that the effects described in this specification are merely examples and are not limiting, and other effects may also be obtained.

[0048] Some examples of combinations of the disclosed technical features are set out below. (1) a plurality of current output units each outputting an output current based on an input output current signal to an external circuit; a substitute current generating unit that generates a substitute current that is a current that substitutes for the output current of the current output unit based on a resistor that is arranged in the same integrated circuit as the current output unit; a signal conversion unit that converts the alternative current into a voltage signal based on a reference resistance; an output current correction unit arranged for each of the current output units and generating the output current signal based on a difference between the voltage signal and a target value; A current output device having a (2) The current output device according to (1), comprising a plurality of the alternative current generating units. (3) A selection unit that selects a plurality of alternative currents generated by the plurality of alternative current generation units, The signal conversion unit converts the alternative current selected by the selection unit into the voltage signal. The current output device according to (2) above. (4) The resistor is disposed in the current output section, The current output section includes a current mirror circuit having a first transistor through which a reference current flows and a second transistor through which the output current that is a mirror of the reference current flows, and a current generated based on the output current signal and the resistor is supplied to the current mirror circuit as the reference current. The current output device according to any one of (1) to (3). (5) The current output device according to (4), wherein the alternative current generating section is configured with a third transistor connected to the current mirror circuit to mirror the reference current. (6) The current output device according to any one of (1) to (4), wherein the alternative current generating section generates the alternative current based on a predetermined reference voltage and the resistance. [Explanation of symbols]

[0049] 1 Current output device 30, 31 Integrated circuits 320, 330, 340, 350 Current output section 101 to 104 Output current correction section 110 Reference Resistor 120 Analog-to-digital conversion section 261-263, 265-267 Switching elements 360, 370, 390 alternative current generator 322, 362 Resistance 323~326, 363~365 MOS transistors

Claims

1. a plurality of current output units each outputting an output current based on an input output current signal to an external circuit; a substitute current generating unit that generates a substitute current that is a current that substitutes for the output current of the current output unit based on a resistor that is arranged in the same integrated circuit as the current output unit; a signal conversion unit that converts the alternative current into a voltage signal based on a reference resistance; an output current correction unit arranged for each of the current output units and generating the output current signal based on a difference between the voltage signal and a target value; A current output device having a

2. 2. The current output device according to claim 1, comprising a plurality of the alternative current generating units.

3. A selection unit that selects a plurality of alternative currents generated by the plurality of alternative current generation units, The signal conversion unit converts the alternative current selected by the selection unit into the voltage signal.

3. The current output device according to claim 2.

4. The resistor is disposed in the current output section, The current output section includes a current mirror circuit having a first transistor through which a reference current flows and a second transistor through which the output current that is a mirror of the reference current flows, and a current generated based on the output current signal and the resistor is supplied to the current mirror circuit as the reference current.

2. The current output device according to claim 1.

5. 5. The current output device according to claim 4, wherein the alternative current generating section is configured by a third transistor connected to the current mirror circuit to mirror the reference current.

6. 2. The current output device according to claim 1, wherein the alternative current generating section generates the alternative current based on a predetermined reference voltage and the resistance.

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