Current and voltage output device

Abstract

This invention provides a current-voltage output device that supports both current output mode and voltage output mode. [Solution] The current-voltage output device comprises a switching power supply unit 1 that generates a voltage to be applied to the load based on a PWM signal CTL, a control calculation unit 3 that generates a signal CTL according to a control command value SP, and a current detection unit 2 that detects the current flowing through the load. The control calculation unit 3 estimates the load resistance value based on the load current value detected by the current detection unit 2 and the output voltage value of the switching power supply unit 1 estimated from the signal CTL. If the load resistance value is less than or equal to a first threshold, it generates a signal CTL so that a current corresponding to the control command value SP flows to the load. If the load resistance value is greater than or equal to a second threshold greater than the first threshold, it generates a signal CTL so that a voltage corresponding to the control command value SP is applied to the load.

Description

[Technical Field]

[0001] This invention relates to a current-voltage output device. [Background technology]

[0002] Conventionally, current output circuits (Patent Documents 1 and 2) that output a 4-20mA current signal based on control instructions, and voltage output circuits that output a 2-10V voltage signal are known for transmitting sensed physical quantities to other devices. However, with conventional technology, it is difficult to share 2-10V output and 4-20mA output in the same circuit, and when incorporating them into a product, it is necessary to provide separate circuits for each, and switching between signal types requires board replacement, switch operation, or software settings.

[0003] Current output circuits require a relatively high power supply voltage (compliance voltage) to drive large load resistances. However, when the load resistance is small, a large portion of the compliance voltage is applied to the current output circuit, leading to significant heat loss on the circuit board. To solve this problem, the current output circuit disclosed in Patent Document 1 reduces the compliance voltage by varying the output voltage of the switching power supply according to the voltage drop across the load resistance and the load current. Furthermore, signals or noise from the load are input to the current output circuit, and these signals or noise could potentially affect the control of the power supply voltage. Therefore, the current output circuit disclosed in Patent Document 2 detects the load voltage by peak-holding it and controls the switching power supply based on the detection result.

[0004] However, the circuits disclosed in Patent Documents 1 and 2 cannot be used as both voltage output circuits and voltage output circuits. For example, the configuration shown in Figure 9 disclosed in Patent Document 1 is a circuit that outputs a current of 4-20mA to a load RL. The current output circuit 100 outputs a voltage signal V IN It outputs a current I0 proportional to the voltage drop V across the load RL. The adder 101 measures the voltage drop V across the load RL. OUT A constant offset voltage V F The value V obtained by adding these values.OUT +V F is input as a control voltage to the control terminal of the switching power supply 102. The switching power supply 102 outputs an output voltage V equal to the control voltage input to the control terminal. S to the current output circuit 100. Thus, the minimum compliance voltage necessary to drive the load RL is generated. In the configuration of FIG. 9, the voltage drop V generated in the load RL OUT is only used for adjusting the output voltage of the switching power supply 102 and is not particularly monitored, so the load resistance value cannot be estimated.

[0005] Also, the configuration of FIG. 10 disclosed in Patent Document 1 is a circuit configuration in which the above offset voltage V F is unnecessary. The differential amplifier 200 amplifies the difference value between the voltage signal V IN and the reference voltage V REF and inputs it to the control terminal of the switching power supply 201. When a control voltage is input to the control terminal of the switching power supply 201, the switching power supply 201 switches the voltage V CC to output a current proportional to the control voltage. The current output from the switching power supply 201 flows through the resistor 202 and the filter 203 to the load resistor RL. The differential amplifier 204 outputs a reference voltage V REF equal to the product G×R×I0 of its amplification factor G, the value R of the resistor 202, and the current I0. Thus, the current I0 flowing through the load resistor RL is converted into the reference voltage V REF , and the output voltage of the switching power supply 201 is controlled by comparing and calculating with the voltage signal V IN in the differential amplifier 200. However, also in the configuration of FIG. 10, the result of converting the load current I0 into a voltage is only used for adjusting the output voltage of the switching power supply 201, and the load resistance value cannot be estimated in the same way as the configuration of FIG. 9. Since neither the configuration of FIG. 9 nor the configuration of FIG. 10 can estimate the load resistance value, it is not possible to support the automatic switching between 4 - 20 mA output and 2 - 10 V output.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Application Publication No. 06-309046 [Patent Document 2] Japanese Patent Publication No. 2019-14909 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The present invention was made to solve the above problems and aims to provide a current-voltage output device that can handle both current output mode and voltage output mode. [Means for solving the problem]

[0008] The present invention relates to a current-voltage output device that outputs a current or voltage according to a control command value, comprising: a switching power supply unit configured to generate a voltage to be applied to a load based on a control signal; a control calculation unit configured to generate the control signal according to the control command value; and a current detection unit configured to detect the current flowing through the load, wherein the control calculation unit estimates a load resistance value based on the load current value detected by the current detection unit and the output voltage value of the switching power supply unit estimated from the control signal, generates the control signal so that a current according to the control command value flows to the load if the load resistance value is less than or equal to a first threshold, and generates the control signal so that a voltage according to the control command value is applied to the load if the load resistance value is greater than or equal to a second threshold greater than the first threshold.

[0009] Also, in one configuration example of the current-voltage output device of the present invention, the current detection unit converts the current flowing through the load into a voltage and outputs it. The control arithmetic unit is configured as a load resistance value estimation arithmetic unit that estimates a load resistance value based on the load current value indicated by the output of the current detection unit and the output voltage value of the switching power supply unit estimated from the control signal. When the load resistance value is less than or equal to the first threshold value, it selects a current output mode in which a current corresponding to the control command value flows through the load, converts the control command value into a voltage value for the current output mode, and outputs it. When the load resistance value is greater than or equal to the second threshold value, it selects a voltage output mode in which a voltage corresponding to the control command value is applied to the load, converts the control command value into a voltage value for the voltage output mode, and outputs it. It is configured with a current / voltage mode determination unit, a PID control arithmetic unit configured to calculate an operation amount so that the output of the current detection unit and the output of the current / voltage mode determination unit are equal, and a PWM signal generation unit that generates a PWM signal with a duty ratio corresponding to the operation amount as the control signal.

[0010] Also, the present invention relates to a current-voltage output device that outputs a current or a voltage according to a control command value, including a switching power supply unit configured to generate a voltage to be applied to a load based on a control signal, a control arithmetic unit configured to generate the control signal according to the control command value, a current detection unit configured to detect the current flowing through the load, and a voltage detection unit configured to detect the voltage applied to the load. The control arithmetic unit estimates a load resistance value based on the load current value detected by the current detection unit and the voltage value detected by the voltage detection unit. When the load resistance value is less than or equal to the first threshold value, it generates the control signal so that a current corresponding to the control command value flows through the load. When the load resistance value is greater than or equal to a second threshold value greater than the first threshold value, it generates the control signal so that a voltage corresponding to the control command value is applied to the load.

[0011] Also, in one configuration example of the current-voltage output device of the present invention, the current detection unit converts the current flowing through the load into a voltage and outputs it, the voltage detection unit divides the voltage applied to the load and outputs it, and the control arithmetic unit estimates a load resistance value based on the load current value indicated by the output of the current detection unit and the voltage value indicated by the output of the voltage detection unit. A load resistance value estimation arithmetic unit configured to: when the load resistance value is less than or equal to the first threshold value, select a current output mode in which a current corresponding to the control command value flows through the load, and convert the control command value into a voltage value for the current output mode and output it; when the load resistance value is greater than or equal to the second threshold value, select a voltage output mode in which a voltage corresponding to the control command value is applied to the load, and convert the control command value into a voltage value for the voltage output mode and output it. A current / voltage mode determination unit configured to: a selector configured to select the output of the current detection unit in the current output mode and select the output of the voltage detection unit in the voltage output mode; and a PID control arithmetic unit configured to calculate an operation amount so that the output of the selector and the output of the current / voltage mode determination unit are equal. And a PWM signal generation unit that generates a PWM signal having a duty ratio corresponding to the operation amount as the control signal.

[0012] Also, in one configuration example of the current-voltage output device of the present invention, the current / voltage mode determination unit executes exception processing when the load resistance value is below a third threshold smaller than the first threshold or when the load resistance value exceeds a fourth threshold larger than the second threshold. It is characterized by that.

Effects of the Invention

[0013] According to the present invention, it is possible to realize a current-voltage output device that can cope with both a current output mode in which a current corresponding to a control command value flows through a load and a voltage output mode in which a voltage corresponding to the control command value is applied to the load. Further, in the present invention, since it is possible to estimate the load resistance value, it is possible to determine the type of the load (input device) from the estimated resistance value, and it is possible to automatically switch between the current output mode and the voltage output mode.

Brief Description of the Drawings

[0014] [Figure 1] Figure 1 is a block diagram showing the configuration of a current-voltage output device according to a first embodiment of the present invention. [Figure 2] Figure 2 is a circuit diagram showing an example of the configuration of a switching power supply unit according to the first embodiment of the present invention. [Figure 3] Figure 3 is a control block diagram of a current-voltage output device according to the first embodiment of the present invention. [Figure 4] Figure 4 is a flowchart illustrating the operation of a current-voltage output device according to the first embodiment of the present invention. [Figure 5] Figure 5 is a block diagram showing the configuration of a current-voltage output device according to a second embodiment of the present invention. [Figure 6] Figure 6 is a control block diagram of a current-voltage output device according to a second embodiment of the present invention. [Figure 7] Figure 7 is a flowchart illustrating the operation of a current-voltage output device according to a second embodiment of the present invention. [Figure 8] Figure 8 is a block diagram showing an example configuration of a computer that implements the control calculation unit according to the first and second embodiments of the present invention. [Figure 9] Figure 9 is a circuit diagram showing the configuration of a conventional current output circuit. [Figure 10] Figure 10 is a circuit diagram showing another configuration of a conventional current output circuit. [Modes for carrying out the invention]

[0015] [First Embodiment] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 is a block diagram showing the configuration of a current-voltage output device according to the first embodiment of the present invention. The current-voltage output device outputs a voltage V proportional to the duty cycle of the PWM signal CTL (control signal). SThe system includes a switching power supply unit 1 that applies power to the load (input device), a current detection unit 2 that detects the current flowing through the load resistor RL, and a control calculation unit 3 that generates a PWM signal CTL according to the control command value SP.

[0016] This embodiment is an example of a case where a current-voltage output device is to be implemented with the minimum number of components and cost. By using a switching power supply unit 1 in which the duty cycle-output voltage characteristics of the PWM signal are known, the output voltage V OUT Monitoring of is unnecessary. Since the control calculation unit 3 only requires one channel of AD conversion, it is easy to use an inexpensive microcontroller in the control calculation unit 3. In this embodiment, the output voltage V OUT Since monitoring is unnecessary, the circuit size can be reduced compared to the configuration of the second embodiment described later. However, since open-loop control is used in the 2-10V voltage output mode, this embodiment is suitable for devices where rough output accuracy is acceptable.

[0017] Figure 2 is a circuit diagram showing an example configuration of the switching power supply unit 1. The switching power supply unit 1 consists of a switching element SW1, a diode D1, a coil L1, and a capacitor C1. Note that Figure 2 shows the simplest example of the switching power supply unit 1, and the actual switching power supply unit 1 is not limited to the configuration shown in Figure 2.

[0018] The current detection unit 2 is a resistor R inserted in series between the output terminal of the switching power supply unit 1 and the load resistor RL. S It consists of an operational amplifier OP1 whose non-inverting input terminal is connected to the output terminal of the switching power supply unit 1 and whose inverting input terminal is connected to the load resistor RL.

[0019] Figure 3 shows the control block diagram of the current-voltage output device of this embodiment. The control calculation unit 3 includes an AD conversion unit 30, a load resistance value estimation calculation unit 31, a current / voltage mode determination unit 32, a PID control calculation unit 33, a gain control unit 34, and a PWM signal generation unit 35. In Figure 3, Kp is the proportional gain, Ki is the integral gain, Kd is the integral, and the derivative gain.

[0020] Figure 4 is a flowchart illustrating the operation of the current-voltage output device in this embodiment. First, the control calculation unit 3 needs to estimate the load resistance value and determine the appropriate operating mode (current mode or voltage mode). In the example in Figure 4, the processing flow is determined assuming that a typical resistance (maximum approximately 600Ω) for a 4-20mA input device is connected as the load resistance RL (internal impedance of a 4-20mA or 2-10V input device).

[0021] The current detection unit 2 outputs a value V1 obtained by converting the current flowing through the load resistor RL into a voltage. The AD conversion unit 30 of the control calculation unit 3 converts the voltage V1 into a digital signal. The load resistance value estimation calculation unit 31 of the control calculation unit 3 controls the PWM signal generation unit 35 to set the duty cycle of the PWM signal CTL output from the PWM signal generation unit 35 to 0% (Figure 4, step S100). At this time, the voltage V output from the switching power supply unit 1 is set to 0%. S The voltage becomes 0V.

[0022] Next, the load resistance value estimation calculation unit 31 gradually increases the duty cycle of the PWM signal CTL output from the PWM signal generation unit 35 from 0%, and the voltage V output from the switching power supply unit 1 S The value is increased (Figure 4, step S101). As described above, in this embodiment, a switching power supply unit 1 is used in which the duty cycle-output voltage characteristics of the PWM signal are known. Therefore, the load resistance value estimation calculation unit 31 calculates the output voltage V of the switching power supply unit 1 from the duty cycle of the PWM signal CTL. S It is possible to estimate this.

[0023] The load resistance value estimation calculation unit 31 calculates the output voltage V of the switching power supply unit 1. S If the estimated value is less than or equal to a predetermined value (10V in this embodiment) (YES in step S102 of Figure 4), and the value of the load current I0 indicated by the voltage V1 becomes 4mA or more (YES in step S103 of Figure 4), then this load current value and the output voltage V S Estimated value and resistance R S The load resistance value is estimated based on the known value (Figure 4, step S104).

[0024] The current / voltage mode determination unit 32 determines that a 4-20mA input device is connected to the current / voltage output device if the estimated load resistance value obtained by the load resistance value estimation calculation unit 31 is 10Ω (third threshold) or greater and 600Ω (first threshold) or less (YES in step S105 of Figure 4), and sets the operating mode of the current / voltage output device to the 4-20mA current output mode (step S106 of Figure 4).

[0025] In current output mode, the current / voltage mode determination unit 32 converts a control command value SP, such as valve opening or sensor measurement value, into a value for current output mode (Figure 4, step S107). Here, the control command value SP is converted into a current value of 4-20mA. However, in practice, the PID control calculation unit 33 needs to calculate the deviation between the current command value and the output voltage V1 of the current detection unit 2 corresponding to the load current value. For this reason, the current / voltage mode determination unit 32 converts the 4-20mA current value corresponding to the control command value SP into a voltage value for current output mode and outputs it, using the same characteristics as the known current-voltage conversion characteristics of the current detection unit 2.

[0026] The PID control calculation unit 33 calculates the manipulated variable by PID control calculation so that the output voltage of the current / voltage mode determination unit 32 and the output voltage V1 of the AD conversion unit 30 are equal (so that the load current value is equal to the current value corresponding to the control command value SP). The gain control unit 34 adjusts the gain of the manipulated variable to fit the control input range of the PWM signal generation unit 35. The PWM signal generation unit 35 generates a PWM signal CTL with a duty cycle corresponding to the manipulated variable input via the gain control unit 34. In this way, the output voltage V of the switching power supply unit 1 is set according to the PWM signal CTL so that the load current value is equal to the current value corresponding to the control command value SP. S This is controlled (Figure 4, step S108). The control calculation unit 3 performs the processing in steps S107 and S108 for each control cycle.

[0027] On the other hand, by increasing the duty cycle of the PWM signal CTL, the output voltage V of the switching power supply unit 1 increased. SEven if the estimated value of reaches a predetermined value (10V in this embodiment), if the value of the load current I0 indicated by the voltage V1 is less than 4mA (NO in step S102), the load resistance value estimation calculation unit 31 calculates, for example, the output voltage V S The estimated load current value and output voltage V when the voltage is 10V S The estimated value is 10V and the resistor R S The load resistance value is estimated based on the known value (Figure 4, step S109).

[0028] The current / voltage mode determination unit 32 determines that a 2-10V input device is connected to the current / voltage output device if the estimated load resistance value obtained by the load resistance value estimation calculation unit 31 is 10kΩ (second threshold) or greater and 100kΩ (fourth threshold) or less (YES in step S110 of Figure 4), and sets the operating mode of the current / voltage output device to the 2-10V voltage output mode (step S111 of Figure 4).

[0029] In voltage output mode, the current / voltage mode determination unit 32 converts control command values ​​SP, such as valve opening or sensor measurement values, into values ​​for voltage output mode (Figure 4, step S112). Here, the control command value SP is converted into a voltage value of 2-10V. In voltage output mode, the output voltage value applied to the load cannot be monitored, so the output signal of the current / voltage mode determination unit 32 bypasses the PID control calculation unit 33 and the gain control unit 34 and is input to the PWM signal generation unit 35. The PWM signal generation unit 35 generates a PWM signal CTL with a duty cycle corresponding to the output signal of the current / voltage mode determination unit 32.

[0030] The control calculation unit 3 performs the processing in steps S112 and S113 for each control cycle.

[0031] If the estimated load resistance value in step S105 is less than 10Ω, it can be assumed that a device with a very low load resistance value is connected or that the load is short-circuited. In this case, the current / voltage mode determination unit 32 performs an exception processing, such as outputting an alarm signal indicating a load abnormality to a higher-level device (not shown), controlling the PWM signal generation unit 35 to stop the output of the switching power supply unit 1, or performing other appropriate processing (Figure 4, step S114). Similarly, if the estimated load resistance value in step S110 exceeds 100kΩ, it can be assumed that a device with an excessively high load resistance value is connected or that the load is open. In this case, the current / voltage mode determination unit 32 performs the above exception processing.

[0032] As described above, the embodiment makes it possible to realize a current-voltage output device that can handle both 4-20mA output and 2-10V output.

[0033] [Second Example] Figure 5 is a block diagram showing the configuration of a current-voltage output device according to a second embodiment of the present invention. The current-voltage output device of this embodiment includes a switching power supply unit 1, a current detection unit 2, a control calculation unit 3a, and a voltage detection unit 4.

[0034] This embodiment shows the output current I0 and output voltage V OUT This is an example of a case where high precision is required or when a step-up / step-down converter is used in the switching power supply unit 1. The control calculation unit 3a requires two AD conversion channels, and the output voltage V OUT A voltage detection unit 4 is required to detect this, but since the output voltage to the load resistor RL can be directly monitored, high-precision voltage output control becomes possible. Accordingly, a step-up / step-down converter with a nonlinear duty cycle-output voltage characteristic of the PWM signal can be used in the switching power supply unit 1, and the power supply voltage V CC The functions of the present invention can be implemented even in systems where the power supply is low or where only a single power supply is available.

[0035] Figure 6 shows a control block diagram of the current-voltage output device of this embodiment. The control calculation unit 3a includes an AD conversion unit 30, a load resistance value estimation calculation unit 31a, a current / voltage mode determination unit 32a, a PID control calculation unit 33, a gain control unit 34, a PWM signal generation unit 35, an AD conversion unit 36, and a selector 37.

[0036] Figure 7 is a flowchart illustrating the operation of the current-voltage output device in this embodiment. The processes in steps S100 and S101 in Figure 7 are the same as in the first embodiment. The voltage detection unit 4 detects the output voltage V applied to the load RL. OUT The voltage V2 obtained by dividing the voltage using the voltage divider circuit 40 is output. The AD conversion unit 36 ​​of the control calculation unit 3a converts the voltage V2 into a digital signal.

[0037] The load resistance value estimation unit 31a calculates the output voltage V2 indicated by the voltage V2. OUT When the load current value indicated by the voltage V1 is 4mA or more (YES in step S103 of Figure 7), and the load current value indicated by the voltage V1 is 10V or less, the load current value and the output voltage V OUT The load resistance value is estimated based on this (Figure 7, step S104a).

[0038] The current / voltage mode determination unit 32a determines the operating mode of the current / voltage output device to a 4-20mA current output mode (Figure 7, step S106) if the estimated load resistance obtained by the load resistance value estimation calculation unit 31a is 10Ω (third threshold) or greater and 600Ω (first threshold) or less (YES in step S105 of Figure 7).

[0039] In current output mode, the current / voltage mode determination unit 32a sets the selector 37 to output current monitoring. That is, the current / voltage mode determination unit 32a controls the selector 37 to select the output of the AD conversion unit 30 (Figure 7, step S115). As a result, the selector 37 inputs the output of the AD conversion unit 30 to the PID control calculation unit 33. The processing in steps S107 and S108 is the same as in the first embodiment.

[0040] On the other hand, by increasing the duty cycle of the PWM signal CTL, the output voltage V2 is shown. OUT Even if the voltage V1 reaches a predetermined value (10V in this embodiment) or higher, if the value of the load current I0 indicated by the voltage V1 is less than 4mA (NO in step S102a), the load resistance value estimation calculation unit 31a calculates, for example, the output voltage V OUT Load current value and output voltage V when the voltage is 10V OUT The load resistance value is estimated based on =10V (Figure 7, step S109a).

[0041] The current / voltage mode determination unit 32a determines the operating mode of the current / voltage output device to a 2-10V voltage output mode (Figure 7, step S111) if the estimated load resistance obtained by the load resistance estimation calculation unit 31a is 10kΩ (second threshold) or greater and 100kΩ (fourth threshold) or less (YES in step S110 of Figure 7).

[0042] In voltage output mode, the current / voltage mode determination unit 32a sets the selector 37 to output voltage monitoring. That is, the current / voltage mode determination unit 32a controls the selector 37 to select the output of the AD conversion unit 36 ​​(Figure 7, step S116). As a result, the selector 37 inputs the output of the AD conversion unit 36 ​​to the PID control calculation unit 33.

[0043] In voltage output mode, the current / voltage mode determination unit 32a converts the control command value SP to a value for voltage output mode (Figure 7, step S112a). Here, the control command value SP is converted to a voltage value of 2-10V. However, in reality, the output voltage V OUT The PID control calculation unit 33 needs to calculate the deviation between the output voltage V2 of the voltage detection unit 4 and the corresponding value. For this reason, the current / voltage mode determination unit 32a converts the control command value SP into a voltage value of 2-10V, divides the converted voltage value using the same voltage division ratio as the known voltage division ratio of the voltage detection unit 4, converts it into a voltage value for the voltage output mode, and outputs it. The processing in step S113 is the same as in the first embodiment.

[0044] Thus, in this embodiment, the output current I0 and output voltage VOUT It can be controlled with higher precision. The thresholds and exception handling details described in the first and second embodiments are merely examples and can be modified as needed depending on the specifications of the product or system in which they are implemented.

[0045] The control calculation units 3 and 3a described in the first and second embodiments can be realized by a computer equipped with a CPU (Central Processing Unit), a storage device, and an interface, and a program that controls these hardware resources. An example of the configuration of this computer is shown in Figure 8.

[0046] The computer comprises a CPU 300, a storage device 301, and an interface device (I / F) 302. A switching power supply unit 1, a current detection unit 2, a voltage detection unit 4, etc., are connected to the I / F 302. In such a computer, the program for realizing the current-voltage output method of the present invention is stored in the storage device 301. The CPU 300 executes the processes described in the first and second embodiments according to the program stored in the storage device 301. [Explanation of Symbols]

[0047] 1…Switching power supply unit, 2…Current detection unit, 3,3a…Control calculation unit, 4…Voltage detection unit, 30,36…AD conversion unit, 31,31a…Load resistance value estimation calculation unit, 32,32a…Current / voltage mode determination unit, 33…PID control calculation unit, 34…Gain control unit, 35…PWM signal generation unit, 37…Selector, 40…Voltage divider circuit, RL…Load resistance, R S ...resistor, OP1...operational amplifier

Claims

1. In a current-voltage output device that outputs a current or voltage according to a control command value, A switching power supply unit configured to generate a voltage to be applied to a load based on a control signal, A control calculation unit configured to generate the control signal according to the control command value, The system includes a current detection unit configured to detect the current flowing through the load, The current-voltage output device is characterized in that the control calculation unit estimates a load resistance value based on the load current value detected by the current detection unit and the output voltage value of the switching power supply unit estimated from the control signal, generates a control signal so that a current corresponding to the control command value flows to the load when the load resistance value is less than or equal to a first threshold, and generates a control signal so that a voltage corresponding to the control command value is applied to the load when the load resistance value is greater than or equal to a second threshold which is greater than the first threshold.

2. In the current-voltage output device according to claim 1, The current detection unit converts the current flowing through the load into a voltage and outputs it. The control calculation unit is, A load resistance value estimation calculation unit is configured to estimate the load resistance value based on the load current value indicated by the output of the current detection unit and the output voltage value of the switching power supply unit estimated from the control signal. A current / voltage mode determination unit is configured to select a current output mode in which a current corresponding to the control command value flows to the load when the load resistance value is less than or equal to the first threshold, and to convert the control command value into a voltage value for the current output mode and output it, and to select a voltage output mode in which a voltage corresponding to the control command value is applied to the load when the load resistance value is greater than or equal to the second threshold, and to convert the control command value into a voltage value for the voltage output mode and output it, A PID control calculation unit configured to calculate an operation variable such that the output of the current detection unit and the output of the current / voltage mode determination unit are equal, A current-voltage output device characterized by comprising a PWM signal generation unit that generates a PWM signal with a duty cycle corresponding to the manipulated amount as the control signal.

3. In a current-voltage output device that outputs a current or voltage according to a control command value, A switching power supply unit configured to generate a voltage to be applied to a load based on a control signal, A control calculation unit configured to generate the control signal according to the control command value, A current detection unit configured to detect the current flowing through the aforementioned load, The system includes a voltage detection unit configured to detect the voltage applied to the load, The current-voltage output device is characterized in that the control calculation unit estimates the load resistance value based on the load current value detected by the current detection unit and the voltage value detected by the voltage detection unit, generates a control signal so that a current corresponding to the control command value flows to the load when the load resistance value is less than or equal to a first threshold, and generates a control signal so that a voltage corresponding to the control command value is applied to the load when the load resistance value is greater than or equal to a second threshold which is greater than the first threshold.

4. In the current voltage output device according to claim 3, The current detection unit converts the current flowing through the load into a voltage and outputs it. The voltage detection unit divides the voltage applied to the load and outputs it. The control calculation unit is, A load resistance value estimation calculation unit configured to estimate the load resistance value based on the load current value indicated by the output of the current detection unit and the voltage value indicated by the output of the voltage detection unit, A current / voltage mode determination unit is configured to select a current output mode in which a current corresponding to the control command value flows to the load when the load resistance value is less than or equal to the first threshold, and to convert the control command value into a voltage value for the current output mode and output it, and to select a voltage output mode in which a voltage corresponding to the control command value is applied to the load when the load resistance value is greater than or equal to the second threshold, and to convert the control command value into a voltage value for the voltage output mode and output it, A selector configured to select the output of the current detection unit when in the current output mode and the output of the voltage detection unit when in the voltage output mode, A PID control calculation unit configured to calculate the manipulated amount such that the output of the selector and the output of the current / voltage mode determination unit are equal, A current-voltage output device characterized by comprising a PWM signal generation unit that generates a PWM signal with a duty cycle corresponding to the manipulated amount as the control signal.

5. In the current-voltage output device according to claim 2 or 4, The current / voltage mode determination unit is characterized in that it performs exception processing when the load resistance value falls below a third threshold which is smaller than the first threshold, or when the load resistance value exceeds a fourth threshold which is larger than the second threshold.

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