Current output device

Abstract

And a current output device is simplified. The 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 the input output current signal to an external circuit. The alternative current generation unit generates an alternative current, which is a current that substitutes the output current of the current output unit, on the basis of a resistor disposed in the same integrated circuit as the current output unit. The signal conversion unit converts the alternative current into a voltage signal on the basis of the reference resistor. The output current correction unit is disposed for each current output unit, and generates an output current signal on the basis of the difference between the voltage signal and the target value.

Description

Technical Field

[0001] The invention relates to a current output device. Background Art

[0002] At present, current output devices are used in workshops and factories to supply a specified current for signal transmission, etc. to field instruments, etc. For example, a current output module is proposed, which generates a voltage corresponding to the output current using a reference resistor, compares the voltage with the reference voltage, and controls the output current based on the comparison result (for example, refer to Patent Document 1).

[0003] The above-mentioned current output module uses a reference resistor to detect the output current. A high precision is required for the reference resistor to reduce the error when detecting the output current.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2022-141251

[0005] However, in the above-mentioned prior art, when applied to a multi-channel current output device that outputs a plurality of currents simultaneously, there is a problem that a high-precision reference resistor is required for each channel. Therefore, in the above-mentioned prior art, there is a problem of increased cost. Summary of the invention

[0006] The present invention provides a technique for simplifying a current output device, which stabilizes a plurality of output currents.

[0007] The current output device of the present invention has a plurality of current output units, a substitute current generating 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 generating unit generates a substitute current that replaces the output current of the current output unit based on a resistor configured 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 resistor. The output current correction unit is configured for each current output unit and generates the output current signal based on the difference between the voltage signal and the target value. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a diagram showing a configuration example of a current output device according to the first embodiment of the present invention.

[0009] Figure 2 It is a diagram showing a configuration example of a current output unit according to the first embodiment of the present invention.

[0010] Figure 3 It is a diagram showing a configuration example of a current output device according to a second embodiment of the present invention.

[0011] Figure 4 It is a diagram showing a configuration example of a substitute current generating unit according to a second embodiment of the present invention.

[0012] Figure 5 It is a diagram showing a configuration example of a current output device according to a third embodiment of the present invention. DETAILED DESCRIPTION

[0013] Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings. The description will be given in the following order. In addition, in each of the following embodiments, the same reference numerals are given to the same parts and repeated descriptions are omitted.

[0014] 1. First Implementation Method

[0015] 2. Second Implementation Method

[0016] 3. Third Implementation Method

[0017] (1. First Implementation Method)

[0018] [Structure of current output device]

[0019] Figure 1 1 is a diagram showing a configuration example of a current output device according to a first embodiment of the present invention. The diagram is a block diagram showing a configuration example of a current output device 1. The current output device 1 outputs currents to a plurality of field instruments. The current output device 1 in the diagram has a current output unit with four channels. Field instruments 2 to 5 are recorded in the diagram. The current output device 1 can output a predetermined current to each of the field instruments 2 to 5.

[0020] 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 an output current signal (DOUT1 to DOUT4 in the figure) as a control signal for each channel of the current output module 20. In addition, the control unit 10 performs feedback control based on a current (substitute current described later) corresponding to the output current of each channel from the current output module 20 to stabilize the output current of the current output module 20.

[0021] In addition, the current output module 20 generates a current for each channel and outputs it to the field instrument 2, etc. via the output terminal. The current output module 20 of the figure has 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 instrument 2 and supplies a current (IOUT1). The output terminal 220 is connected to the field instrument 3 and supplies a current (IOUT2). The output terminal 230 is connected to the field instrument 4 and supplies a current (IOUT3). The output terminal 240 is connected to the field instrument 5 and supplies a current (IOUT4). In addition, the current output module 20 is configured with a current output unit (a current output unit 320, etc. described later) corresponding to the above-mentioned output terminals 210-240, respectively. The current output unit 320, etc. is respectively connected to the output terminal 210, etc. For example, one end of the output terminal 210 is connected to the current output unit 320, and the other end of the output terminal 210 is connected to the common GND.

[0022] 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 converter 120, and a selection control unit 268. In the figure, the "analog-to-digital converter" is referred to as "A / D".

[0023] The output current correction unit 101, etc. is configured for each channel, and outputs an output current signal as a control signal based on the difference between the voltage signal (DIN) corresponding to the output current of the channel corresponding to itself and the target value. "ISET1", "ISET2", "ISET3" and "ISET4" in the figure respectively represent the target values ​​of the output current correction units 101 to 104. In addition, "DOUT1", "DOUT2", "DOUT3" and "DOUT4" respectively represent the output current signals of the output current correction units 101 to 104. In addition, the output current correction unit 101, etc. in the figure generates a digital output current signal. The output current correction unit 101, etc. controls the current output unit 320, etc. in a manner that reduces the difference between the voltage signal (DIN) corresponding to the output current and the target value.

[0024] 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 corresponding to the output current of the current output unit 320, etc., and is a current that replaces the output current. By passing the substitute current through the reference resistor 110, a voltage signal (VVAL) can be generated. In addition, the circuit of the reference resistor 110 is an example of the "signal conversion unit" of the present invention.

[0025] The analog-to-digital converter 120 performs analog-to-digital conversion on the voltage signal (VVAL) to generate a voltage signal (DIN).

[0026] The selection control unit 268 controls the selection of the substitute current of the current output module 20. The substitute current is generated for each of the current output units 320 to 350. One of the plurality of substitute currents is selected and output from the current output module 20. The selection control unit 268 controls the selection of the substitute current.

[0027] The current output module 20 has the aforementioned 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). In the figure, the "digital analog conversion unit" is denoted as "D / A". In addition, the current output module 20 also has a plurality of substitute current generating units (substitute current generating unit 390 described later), switching elements 261, 262, 265, and 266. In the figure, the "switching element" is denoted as "SW". In addition, the current output units 320 and 330, the digital analog conversion units 311 and 312, and the switching elements 261 and 262 are configured in the integrated circuit 30. In addition, the current output units 340 and 350, the digital analog conversion units 313 and 314, and the switching elements 265 and 266 are configured in the integrated circuit 31.

[0028] The digital-to-analog converter 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-to-analog converter 311 converts DOUT1 into an analog signal and outputs it to the current output unit 320. The digital-to-analog converter 312 converts DOUT2 into an analog signal and outputs it to the current output unit 330. The digital-to-analog converter 313 converts DOUT3 into an analog signal and outputs it to the current output unit 340. The digital-to-analog converter 314 converts DOUT4 into an analog signal and outputs it to the current output unit 350. In addition, the digital-to-analog converters 311 and 312 may also be arranged outside the integrated circuit 30. Similarly, the digital-to-analog converters 313 and 314 may also be arranged outside the integrated circuit 31.

[0029] The current output unit 320 etc. generates an output current based on the output current signal, and outputs it to the field device 2 etc. via the output terminal 210 etc. Specifically, the current output unit 320 outputs the current via the output terminal 210. The current output unit 330 outputs the current via the output terminal 220. The current output unit 340 outputs the current via the output terminal 230. The current output unit 350 outputs the current via the output terminal 240. In addition, the current output unit 320 etc. respectively generates a substitute current for its own output current. The structure of the current output unit 320 etc. will be described in detail later.

[0030] The switch element 261 and the like are switches that are arranged on a signal line for supplying a substitute current and output a substitute current. Specifically, the switch element 261 corresponds to the substitute current of the current output unit 320, the switch element 262 corresponds to the substitute current of the current output unit 330, the switch element 265 corresponds to the substitute current of the current output unit 340, and the switch element 266 corresponds to the substitute current of the current output unit 350. By turning on any one of the above-mentioned switch elements 261 and the like, the substitute current can be selected. The selected substitute current is output from the current output module 20 as the aforementioned IVAL. The aforementioned selection control unit 268 controls the conduction of the switch elements 261, 262, 265, and 266. MOS transistors can be applied to the switch element 261 and the like. In addition, the circuit of the selection control unit 268 and the switch elements 261, 262, 265, and 266 is an example of the "selection unit" of the present invention.

[0031] The substitute current of the channel selected by the selection control unit 268 and the switch element 261 is returned to the corresponding output current correction unit 101 through the reference resistor 110 and the analog-to-digital conversion unit 120, and the output current is corrected. By performing the above processing sequentially for all channels, the accuracy of the output currents IOUT1-IOUT4 can be improved.

[0032] [Structure of current output section]

[0033] Figure 2 1 is a diagram showing a configuration example of a current output unit according to the first embodiment of the present invention. This diagram is a circuit diagram showing a configuration example of a current output unit 320. In addition, the current output unit 330 and the like may also be formed into a similar configuration.

[0034] The current output unit 320 includes an operational amplifier 321, a resistor 322, and MOS transistors 323 to 326. An n-channel MOS transistor may be used for the MOS transistor 323. Alternatively, a p-channel MOS transistor may be used for the MOS transistors 324 to 326. The power supply line Vdd is provided in the current output unit 320.

[0035] The signal line from the digital-to-analog conversion unit 311 is connected to the non-inverting input of the operational amplifier 321. The output of the operational amplifier 321 is connected to the gate of the MOS transistor 323. The source of the MOS transistor 323 is connected to the inverting input of the operational amplifier 321 and one end of the resistor 322. The other end of the resistor 322 is connected to the common GND. The drain of the MOS transistor 323 is connected to the drain of the MOS transistor 324. The gate of the MOS transistor 324 is connected to the source of the MOS transistor 324, the gate of the MOS transistor 325, the gate of the MOS transistor 326, and the power supply line Vdd. The source of the MOS transistor 325 is connected to the power supply line Vdd, and the drain is connected to the wiring for the switch element 261. The source of the MOS transistor 326 is connected to the power supply line Vdd, and the drain is connected to the wiring for the output terminal 210.

[0036] The circuit of the operational amplifier 321 , the MOS transistor 323 and the resistor constitutes 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 .

[0037] MOS transistor 324 and MOS transistor 326 form a current mirror circuit. The gate of MOS transistor 324 is connected to its own source. The drain current of MOS transistor 324 is mirrored in MOS transistor 326 as a reference current. This reference current is equivalent to the drain current of MOS transistor 323. Therefore, the drain current of MOS transistor 326 becomes a current based on the output current signal. By making the channel sizes of MOS transistor 324 and MOS transistor 326 equal, the mirror ratio can be achieved to 1:1. In addition, MOS transistor 324 is an example of the "first transistor" of the present invention. MOS transistor 326 is an example of the "second transistor" of the present invention.

[0038] In addition, a MOS transistor 325 is also connected to the above-mentioned current mirror circuit. The reference current is also mirrored in the MOS transistor 325. Therefore, the drain current of the MOS transistor 325 also becomes a current based on the output current signal. In addition, the drain current of the MOS transistor 326 and the drain current of the MOS transistor 325 are currents of a ratio corresponding to the respective channel sizes, etc. Therefore, the drain current of the MOS transistor 325 can be used to replace the drain current of the MOS transistor 326, that is, the output current. By changing the size of the channel of the MOS transistor 325 relative to the channel size of the MOS transistor 324, a substitute current of a desired ratio can be generated. In this way, a substitute current can be generated using the circuit of the MOS transistor 325. In addition, the circuit including the MOS transistor 325 constitutes a substitute current generating unit 390. The MOS transistor 325 is an example of the "third transistor" of the present invention.

[0039] In this way, a substitute current can be generated based on the resistor 322. In addition, the resistor 322 is also configured in other current output units 330, etc., so that a substitute current can be generated in each current output unit 320-350. The resistor 322 is a resistor formed in the integrated circuit 30, etc., so the fluctuation of the resistance value of the resistor 322 of each current output unit 320 is reduced. Therefore, the substitute current can be used instead of the output current to perform feedback control. In addition, the output current and the substitute current contain errors based on the fluctuation of the resistor 322. However, by including Figure 1 The feedback control system including the reference resistor 110 circuit can reduce (compress) the above error. In addition, in order to reduce the error of the feedback control system, it is necessary to Figure 1 A high-precision resistor is used for the reference resistor 110. However, a high-precision resistor is not required for the plurality of resistors 322. Therefore, the increase in the cost of the current output device 1 can be reduced.

[0040] In addition, the current output device 1 uses a circuit such as the switch element 261 to select a substitute current from a plurality of current output units 320 and the like and input the substitute current to the circuit of the reference resistor 110 and the analog-to-digital converter 120. Therefore, the structure of the current output device 1 can be simplified compared to the case where the circuit of the reference resistor 110 and the analog-to-digital converter 120 are arranged for each channel. As a result, the increase in the cost of the current output device 1 can be reduced.

[0041] (2. Second Implementation Method)

[0042] The current output device 1 of the first embodiment described above generates a substitute current based on the resistor 322 disposed in the current output unit 320. In addition, since feedback control including the digital analog converter 311 and the like is performed in the loop, there is a problem that the response speed is slow. In contrast, the current output device 1 of the second embodiment of the present invention is different from the first embodiment described above in that a substitute current is generated based on a resistor disposed in the integrated circuit 30 and the like.

[0043] [Structure of current output device]

[0044] Figure 3 2 is a diagram showing a configuration example of a current output device according to a second embodiment of the present invention. Figure 1 Similarly, this is a block diagram showing a configuration example of the current output device 1. The current output device 1 of this figure is similar to the current output device 1 in that it has switch elements 263 and 267 and substitute current generators 360 and 370 instead of the switch elements 261, 262, 265, and 266. Figure 1 The current output device 1 is different.

[0045] The substitute current generating units 360 and 370 are Figure 2 The substitute current generating unit 390 of the integrated circuit 30 similarly generates a substitute current. The substitute current generating unit 360 and the like generate a substitute current based on the resistance they have. The substitute current generating unit 360 is configured in the integrated circuit 30, and the substitute current generating unit 370 is configured in the integrated circuit 31. In addition, an example in which the current output units 320 and 330 and the substitute current generating unit 360 are configured as the same semiconductor chip in the integrated circuit 30 is envisioned. Similarly, an example in which the current output units 340 and 350 and the substitute current generating unit 370 are configured as the same semiconductor chip in the integrated circuit 31 is envisioned.

[0046] The switch elements 263 and 267 are switches that are disposed on a signal line for supplying a substitute current and output a substitute current. Specifically, the switch element 263 corresponds to the substitute current of the substitute current generating unit 360 , and the switch element 267 corresponds to the substitute current of the substitute current generating unit 370 .

[0047] In addition, the substitute current generating section 390 may be omitted from the current output section 320 and the like in the figure.

[0048] [Structure of substitute current generating unit]

[0049] Figure 4 2 is a diagram showing a configuration example of a substitute current generating unit according to a second embodiment of the present invention. This diagram is a circuit diagram showing a configuration example of a substitute current generating unit 360. In addition, the substitute current generating unit 370 may also be formed into a similar configuration.

[0050] The substitute current generating section 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 used for the MOS transistor 363. P-channel MOS transistors can be used for the MOS transistors 364 and 365. In addition, a power supply line Vdd is provided in the substitute current generating section 360.

[0051] The low potential side terminal of the voltage source 369 is connected to the common GND, and the high potential side 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 the resistor 362. The other end of the resistor 362 is connected to the 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 the wiring for the switch element 263.

[0052] MOS transistors 364 and 365 form a current mirror circuit. In addition, the circuit of operational amplifier 361, MOS transistor 363 and resistor 362 forms a voltage-current conversion circuit. The output voltage of voltage source 369 is equivalent to the reference voltage. The drain current of MOS transistor 363 is based on the voltage of voltage source 369 and the current of resistor 362. This drain current becomes the reference current of the current mirror circuit, and is mirrored in MOS transistor 365. The drain current of MOS transistor 365 is output as a substitute current. Resistor 362 is a resistor configured in the same integrated circuit 30 as resistor 322 of current output unit 320, and therefore has the same characteristics as resistor 322. Specifically, the resistance value fluctuation of resistor 362 and resistor 322 is reduced. In addition, the change of resistance value based on temperature drift of resistor 362 and resistor 322 is also approximately equal. Therefore, the current based on resistor 362 can be used as a substitute current instead of the substitute current based on resistor 322.

[0053] In this way, a substitute current can be generated based on the resistor 362. Since a high-precision resistor is not required for the resistor 362, the increase in the cost of the current output device 1 can be reduced. In addition, the circuit using the switch elements 263 and 267 selects the substitute current from the integrated circuit 30 and the like, and inputs it to the circuit of the reference resistor 110 and the analog-to-digital conversion unit 120. As a result, the structure of the current output device 1 can be simplified compared to the case where the circuit of the reference resistor 110 and the analog-to-digital conversion unit 120 are configured in each channel. In addition, compared to Figure 1Compared with the current output device 1 of the second embodiment of the present invention, the digital-to-analog conversion unit 311 is not included in the control system. Therefore, the current output device 1 of the second embodiment of the present invention can improve the response speed.

[0054] The configuration of the current output device 1 other than this is the same as that of the current output device 1 according to the first embodiment of the present invention, and thus the description thereof will be omitted.

[0055] (3. Third Implementation Method)

[0056] A modification of the current output device 1 of the first embodiment described above will be described.

[0057] [Structure of current output device]

[0058] Figure 5 1 is a diagram showing a configuration example of a current output device according to a third embodiment of the present invention. Figure 1 Similarly, this is a block diagram showing a configuration example of the current output device 1. The current output device 1 of this figure is similar to the current output device 1 in that it further includes switching elements 263 and 267 and substitute current generating units 360 and 370. Figure 1 The current output device 1 is different.

[0059] The current output device 1 of the figure has Figure 2 The substitute current generating unit 390 and the substitute current generating units 360 and 370 are used. Therefore, the current output device 1 of the figure can select and use the substitute current generated by the substitute current generating unit 390 and the substitute current generating units 360 and 370. For example, in the case of controlling the output current with higher accuracy, the substitute current from the substitute current generating unit 390 arranged in each current output unit 320 can be selected, and in the case of requiring a higher speed response, the substitute current from the substitute current generating unit 360 and the like can be selected.

[0060] The configuration of the current output device 1 other than this is the same as that of the current output device 1 according to the first embodiment of the present invention, and thus the description thereof will be omitted.

[0061] The above describes the various embodiments of the present invention, but the technical scope of the present invention is not limited to the above embodiments, and various changes can be made within the scope of the gist of the present invention. In addition, the structural elements of different embodiments and modified examples can be appropriately combined.

[0062] In addition, the effects described in this specification are merely illustrative and are not limiting, and other effects may also be possible.

[0063] Several examples of combinations of the disclosed technical features are described below.

[0064] (1) A current output device, wherein:

[0065] The current output device comprises:

[0066] a plurality of current output sections that output output currents based on the input output current signals to an external circuit;

[0067] a substitute current generating unit for generating a substitute current that replaces the output current of the current output unit based on a resistor disposed in the same integrated circuit as the current output unit;

[0068] a signal conversion unit that converts the substitute current into a voltage signal based on a reference resistor; and

[0069] An output current correction unit is provided for each of the current output units and generates the output current signal based on a difference between the voltage signal and a target value.

[0070] (2) The current output device according to (1), wherein:

[0071] The current output device includes a plurality of substitute current generating sections.

[0072] (3) The current output device according to (2), wherein:

[0073] The current output device further includes a selection unit for selecting a plurality of substitute currents generated by the plurality of substitute current generating units.

[0074] The signal conversion unit converts the substitute current selected by the selection unit into the voltage signal.

[0075] (4) The current output device according to any one of (1) to (3), wherein:

[0076] The resistor is arranged in the current output portion,

[0077] The current output unit has a current mirror circuit, which has: a first transistor for passing a reference current; and a second transistor for passing the output current mirrored relative to the reference current. The current generated based on the output current signal and the resistor is supplied to the current mirror circuit as the reference current.

[0078] (5) The current output device according to (4), wherein:

[0079] The substitute current generating unit is formed of a third transistor connected to the current mirror circuit and mirroring the reference current.

[0080] (6) The current output device according to any one of (1) to (3), wherein:

[0081] The substitute current generating unit generates the substitute current based on a predetermined reference voltage and the resistance.

[0082] Description of the label

[0083] 1 Current output device

[0084] 30, 31 Integrated Circuits

[0085] 320, 330, 340, 350 Current output

[0086] 101~104 output current correction unit

[0087] 110 reference resistor

[0088] 120 Analog-digital conversion unit

[0089] 261~263, 265~267 switch elements

[0090] 360, 370, 390 substitute current generation unit

[0091] 322, 362 resistors

[0092] 323~326, 363~365 MOS transistors

Claims

1. A current output device, wherein: The current output device comprises: a plurality of current output sections that output output currents based on the input output current signals to an external circuit; a substitute current generating unit for generating a substitute current that replaces the output current of the current output unit based on a resistor disposed in the same integrated circuit as the current output unit; a signal conversion unit that converts the substitute current into a voltage signal based on a reference resistor; as well as An output current correction unit is provided for each of the current output units and generates the output current signal based on a difference between the voltage signal and a target value.

2. The current output device according to claim 1, wherein: The current output device includes a plurality of substitute current generating sections.

3. The current output device according to claim 2, wherein: The current output device further includes a selection unit for selecting a plurality of substitute currents generated by the plurality of substitute current generating units. The signal conversion unit converts the substitute current selected by the selection unit into the voltage signal.

4. The current output device according to claim 1, wherein: The resistor is arranged in the current output portion, The current output unit includes a current mirror circuit, the current mirror circuit including: a first transistor through which a reference current flows; A second transistor through which the output current mirrored with respect to the reference current flows is provided, and a current generated based on the output current signal and the resistor is supplied to the current mirror circuit as the reference current.

5. The current output device according to claim 4, wherein: The substitute current generating unit is formed of a third transistor connected to the current mirror circuit and mirroring the reference current.

6. The current output device according to claim 1, wherein: The substitute current generating unit generates the substitute current based on a predetermined reference voltage and the resistance.

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