Current-Voltage Detection Device and Current-Voltage Detection Method

Abstract

The current-voltage detection device (1) includes a switch (31) that selects and switches an input path to be conducted to the output side from the input path from the current input terminal (11) and the input path from the voltage input terminal (12) according to a timing signal, a switch (21) that selects and switches a resistor to be conducted with the input path from the current input terminal (11) from shunt resistors (22a, 22b, 22c) according to a selection signal, a timing generation unit (54) that outputs the timing signal to the switch (31), and a current range determination unit (55) that determines a shunt resistor for which the value of the difference between the current conversion value and the input voltage value is small from the shunt resistors (22a, 22b, 22c) and outputs a selection signal for selecting the determined shunt resistor to the switch (21).

Description

Technical Field

[0001] The present disclosure relates to a current-voltage detection device and a current-voltage detection method.

Background Art

[0002] In power measurement, since power is obtained as the product of current and voltage, it is necessary to perform current detection and voltage detection simultaneously or by quickly switching between them. For example, since a power measurement device includes a circuit for current detection and a circuit for voltage detection, current and voltage values can be detected almost simultaneously, enabling instantaneous power measurement.

[0003] However, in a device having both circuits for current detection and voltage detection in one device, if circuits up to the part that performs digital signal processing via AD conversion from analog signal input are provided in two systems for current detection and voltage detection, the circuit scale increases.

[0004] On the other hand, for example, in the power control device described in Patent Document 1, the circuits provided after the current detection unit and the voltage detection unit are shared, and a switch is used to switch between the current detection unit and the voltage detection unit for the shared circuit. Thereby, an increase in the circuit scale of the device can be suppressed.

[0005] Also, in current detection, the current from the input terminal is passed through a shunt resistor, and the current amount (hereinafter referred to as the current conversion value) is measured by converting it into a voltage, which is the product of the shunt resistor and the input current, that is, the potential difference generated across the shunt resistor.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the conventional technology described in Patent Document 1, when switching from current detection to voltage detection, if there is a large level difference between the current conversion value and the input voltage value, there is a problem that large ringing occurs in the voltage waveform. For example, since ringing occurs in the initial stage of switching, if switching is performed in a short time, the voltage signal including the ringing waveform will be AD-converted in the subsequent stage, which becomes a factor of error in the input data (current value or voltage value).

[0008] The present disclosure solves the above problems, and an object thereof is to obtain a current-voltage detection device capable of suppressing ringing generated by switching between current detection and voltage detection.

Means for Solving the Problems

[0009] The current-voltage detection device according to the present disclosure includes an input switching switch that selects and switches an input path to be conducted to the output side from among the input path from the current input terminal and the input path from the voltage input terminal according to a timing signal, a plurality of shunt resistors having different resistance values, a resistance switching switch that selects and switches a resistor to be conducted to the input path from the current input terminal from among the plurality of shunt resistors according to a selection signal, a timing generation unit that outputs the timing signal to the input switching switch, and a determination unit that determines a shunt resistor for which the value of the difference between the current conversion value converted into voltage by the product of the input current value input from the current input terminal and the value of the shunt resistor and the input voltage value input from the voltage input terminal becomes small, and outputs a selection signal for selecting the determined shunt resistor to the resistance switching switch.

Effects of the Invention

[0010] According to the present disclosure, a shunt resistor for which the value of the difference between the current conversion value and the input voltage value becomes small is determined from among a plurality of shunt resistors having different resistance values, and the determined shunt resistor is conducted to the input path from the current input terminal. When the value of the difference between the current conversion value and the input voltage value becomes small, the magnitude of ringing also becomes small. Therefore, the current-voltage detection device according to the present disclosure can suppress the ringing generated by switching between current detection and voltage detection.

Brief Description of Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0012] Embodiment 1. FIG. 1 is a circuit diagram showing a configuration example of the current-voltage detection device 1 according to Embodiment 1. In FIG. 1, the current-voltage detection device 1 detects, for example, the voltage value of an AC voltage applied from a commercial power source to a load and the current value of an AC current. The current-voltage detection device 1 includes a current input terminal 11, a voltage input terminal 12, and an input return terminal 13. The current input terminal 11 is a terminal to which an input current signal I in is input. The voltage input terminal 12 is a terminal to which an input voltage signal V in is input. The input return terminal 13 is a terminal connected to the ground. A return signal Rtn flowing between the current-voltage detection device 1 and the power source is returned to the ground through the input return terminal 13.

[0013] A current detection unit (not shown in FIG. 1) is connected to the current input terminal 11. The current detection unit generates an analog input current signal I in representing the current value of the AC power supplied from the power source. For example, the current detection unit performs conversion so that the current becomes a voltage value within the input range of the AD conversion unit 52, and generates the input current signal I in . A voltage detection unit (not shown in FIG. 1), for example, is connected to the voltage input terminal 12. The voltage detection unit converts the voltage value of the AC power supplied from the above power source and generates an analog input voltage signal V in . For example, the voltage detection unit performs voltage conversion at a rate such that the peak value of the AC voltage from the power source falls within the input range of the AD conversion unit 52, and generates the input voltage signal V in .

[0014] The switch 21 is a resistance switching switch that selects and switches a shunt resistor to be conducted to the input path from the current input terminal 11 from among the shunt resistors 22a, 22b, and 22c according to a selection signal. The shunt resistors 22a, 22b, and 22c have different resistance values from each other. For example, assume that the resistance values differ by 100 times. Specifically, the resistance value Rsa of the shunt resistor 22a is 0.1 mΩ, the resistance value Rsb of the shunt resistor 22b is 10 mΩ, and the resistance value Rsc of the shunt resistor 22c is 1000 mΩ. By having such greatly different resistance values from each other, it is possible to select a shunt resistor for which the difference between the current conversion value and the input voltage value described later becomes the smallest from among these shunt resistors. Note that the shunt resistors 22a, 22b, and 22c are collectively referred to as the shunt resistor 22 as appropriate.

[0015] The switch 31 is an input switching switch that selects and switches an input path to be conducted to the output side from among the input path from the current input terminal 11 and the input path from the voltage input terminal 12 according to a timing signal. An amplifier 41 is connected to the output side of the switch 31. When the switch 31 conducts the input path from the current input terminal 11 to the output side, the input current signal I input from the current input terminal 11in is output to the amplifier 41, and when the input path from the voltage input terminal 12 is made conductive to the output side, the input voltage signal V input from the voltage input terminal 12 in is output to the amplifier 41.

[0016] The amplifier 41 inputs the analog input signal output from the switch 31 and amplifies the intensity of the analog input signal. The amplified analog input signal by the amplifier 41 is output to the sample and hold circuit 42. Note that the analog input signal is the input current signal I in or the input voltage signal V in is.

[0017] The sample and hold circuit 42 is a circuit that holds the analog signal input from the current input terminal 11 or the voltage input terminal 12 and output through the switch 31. For example, the sample and hold circuit 42 is a circuit composed of a resistor and a capacitor. One end of the resistor is connected to the output end of the amplifier 41, and the other end is connected to one end of the capacitor. The other end of the capacitor is grounded. Further, the connection point between the other end of the resistor and the other end of the capacitor is connected to the subsequent AD conversion unit 52.

[0018] In the sample and hold circuit 42, the analog input signal output from the amplifier 41 is connected to the capacitor via the resistor. When the switch 31 is switched, the charge of the analog input signal is accumulated in the capacitor, and further, when the switch 31 is switched, the charge accumulated in the capacitor is discharged. That is, the sample and hold circuit 42 is a circuit that holds the analog input signal for a certain period of time by accumulating charge in the capacitor. By using the sample and hold circuit 42 and the AD conversion unit 52, it is possible to convert the analog input signal into a digital signal after holding it for a certain period of time.

[0019] The control unit 51 controls the overall operation of the current-voltage detection device 1. The control unit 51 includes an AD conversion unit 52, a data processing unit 53, a timing generation unit 54, and a current range determination unit 55. For example, when the control unit 51 executes an application for current-voltage detection, the functions of the AD conversion unit 52, the data processing unit 53, the timing generation unit 54, and the current range determination unit 55 are realized by the control unit 51.

[0020] The AD conversion unit 52 converts the analog input signal output from the sample and hold circuit 42 into a digital input signal. For example, the AD conversion unit 52 samples data from the analog input signal within the input range at a constant sampling period to generate a digital input signal composed of the sampled digital data.

[0021] The data processing unit 53 detects a current value using the input current signal I in converted into a digital signal, and detects a voltage value using the input voltage signal V in converted into a digital signal. For example, the data processing unit 53 calculates a current value from the input current signal I in for all sampling points, and calculates a voltage value from the input voltage signal V in . The data processing unit 53 may calculate the effective value of the AC voltage based on the detected change in the voltage value.

[0022] The timing generation unit 54 generates a timing signal and outputs the generated timing signal to the switch 31. For example, the timing generation unit 54 generates a rectangular wave signal in which the high level and the low level alternate at a constant period as the timing signal. In order to perform a voltage detection sequence when this rectangular wave timing signal is at a high level, the input path from the voltage input terminal 12 is switched, and in order to perform a current detection sequence when it is at a low level, the input path from the current input terminal 11 is switched.

[0023] The current range determination unit 55 is a determination unit that determines a shunt resistor among the shunt resistors 22a, 22b, and 22c for which the value of the difference between the current conversion value and the input voltage value input from the voltage input terminal is small, and outputs a selection signal for selecting the determined shunt resistor to the switch 21. The current conversion value is converted to a voltage by the product of the input current value input from the current input terminal 11 and the value of the shunt resistor.

[0024] For example, based on the result of comparing the digital input signal output from the AD conversion unit 52 and the timing signal output from the timing generation unit 54, the current range determination unit 55 determines, from the shunt resistors 22a, 22b, and 22c, a shunt resistor for which the value of the difference between the input voltage value detected in the voltage detection sequence and the current conversion value is small.

[0025] In the current detection sequence, by passing the input current through any one of the shunt resistors 22a, 22b, and 22c, the current range determination unit 55 detects the input current value (A). Then, the current range determination unit 55 calculates a current conversion value (V) converted to a voltage by obtaining the product of the input current value (A) and the known resistance value (Ω) of the currently selected shunt resistor. In this way, if the voltage value input to the AD conversion unit 52 and the resistance value of the selected shunt resistor are known, the input current value can be uniquely determined.

[0026] The current range determination unit 55 acquires the input current signal I in output from the AD conversion unit 52 to the data processing unit 53 in the current detection sequence, and obtains a current conversion value converted to a voltage by the product of the current value of the input current signal I in and the resistance value of the shunt resistor 22. Further, the current range determination unit 55 acquires the input voltage signal V in output from the AD conversion unit 52 to the data processing unit 53 in the voltage detection sequence, and detects the voltage value of the input voltage signal V in And the current range determination unit 55 is the input voltage signal V inSelect the shunt resistor to be switched next so that the level difference between the voltage value and the current conversion value becomes small.

[0027] Based on the timing signal acquired from the timing generation unit 54, the current range determination unit 55 determines whether the digital signal output from the AD conversion unit 52 is the input current signal I in or the input voltage signal V in For example, assume that the timing signal is a rectangular wave signal in which the high level and the low level alternate at a constant period, and the voltage detection sequence is performed when the signal is at the high level, and the current detection sequence is performed when the signal is at the low level. In this case, the current range determination unit 55 determines the shunt resistor for which the difference value between the input voltage value and the current conversion value detected in the voltage detection sequence performed when the signal is at the high level becomes small.

[0028] Furthermore, the current-voltage detection device 1 may repeatedly perform the voltage detection sequence and the current detection sequence until the difference value between the input voltage value and the current conversion value becomes equal to or less than the reference value. In the repetition of these sequences, the current range determination unit 55 may determine the shunt resistor for which the difference value between the input voltage value and the current conversion value becomes equal to or less than the reference value. Thereby, it is possible to switch to a shunt resistor that suppresses ringing due to the switching between current detection and voltage detection.

[0029] FIG. 2 is a waveform diagram showing a voltage waveform, a timing signal waveform A, and a ringing waveform B in the first embodiment. In FIG. 2, the uppermost waveform is the voltage waveform switched by the switch 31, and shows the signal waveform output from the AD conversion unit 52 to the data processing unit 53. The voltage detection sequence is performed when the timing signal waveform A is at the high level, and the current detection sequence is performed when the timing signal waveform A is at the low level.

[0030] The portion corresponding to the high level section of the timing signal waveform A in the uppermost voltage waveform is the input voltage signal V obtained in the voltage detection sequence inis the voltage value, and the portion corresponding to the low-level section of the timing signal waveform A is the current conversion value I obtained in the current detection sequence ina , I inb and I inc are shown.

[0031] For example, assume that the resistance value Rsa of the shunt resistor 22a is 0.1 mΩ, the resistance value Rsb of the shunt resistor 22b is 10 mΩ, and the resistance value Rsc of the shunt resistor 22c is 1000 mΩ. When switched to the shunt resistor 22a by the switch 21, as shown in FIG. 2, a current conversion value I ina of several mV is obtained.

[0032] When the voltage value of the input voltage signal V in is several volts, a large level difference as indicated by the double arrows occurs between the current conversion value I ina and the voltage value of the input voltage signal V in . When there is a large difference between the voltage value of the input voltage signal V in and the current conversion value I ina , a large ringing waveform B occurs in the voltage waveform due to the sudden change in potential when the input path is switched by the switch 31 in the voltage waveform input to the amplifier 41.

[0033] The ringing not only increases the amplitude of the ringing as the potential difference increases, but also increases the convergence time for the amplitude to converge. When an analog input signal including a ringing component is input to the AD conversion unit 52, a difference corresponding to the ringing component occurs in the current value or current value converted into a digital signal by the AD conversion unit 52. Therefore, this results in an error factor in the input data input to the data processing unit 53.

[0034] When switched to the shunt resistor 22b by the switch 21, as shown in FIG. 2, a current conversion value I inb of several hundred mV is obtained. If the voltage value of the input voltage signal V in is several volts, the current conversion value I inb and the input voltage signal V inA level difference indicated by double arrows occurs between the voltage value of. In this case, in the voltage waveform, a ringing waveform B of medium magnitude is generated, which is smaller than when ina .

[0035] When switched to the shunt resistor 22c by the switch 21, as shown in FIG. 2, a current conversion value I of several volts inc is obtained. When the voltage value of the input voltage signal V in is several volts, the smallest level difference indicated by double arrows occurs between the current conversion value I inc and the voltage value of the input voltage signal V in . In this case, the smallest ringing waveform B is generated in the voltage waveform. For this reason, the current range determination unit 55 selects the shunt resistor 22c as the shunt resistor 22 used for current detection and voltage detection of the AC power supplied from the power source.

[0036] Next, the current-voltage detection method according to Embodiment 1 will be described. FIG. 3 is a flowchart showing the current-voltage detection method according to Embodiment 1, and shows the current-voltage detection by the current-voltage detection device 1. The switch 31 switches the input path to be conducted to the output side to the input path from the voltage input terminal 12 according to the timing signal input from the timing generation unit 54 (step ST1). For example, the switch 31 switches to the voltage detection sequence when the timing signal waveform A is at a high level.

[0037] The control unit 51 detects the voltage value of the input voltage signal V in input from the voltage input terminal 12 (step ST2). For example, the input voltage signal V in output from the switch 31 is input to the amplifier 41, and the amplifier 41 amplifies the intensity of the input voltage signal V in . The input voltage signal V in amplified by the amplifier 41 is output to the sample hold circuit 42. The sample hold circuit 42 temporarily holds the input voltage signal V inis output to the AD conversion unit 52. The AD conversion unit 52 converts the input voltage signal V in into a digital signal, thereby detecting the voltage value of the input voltage signal V in .

[0038] The switch 31 switches the input path to be conducted to the output side from the input path from the current input terminal 11 according to the timing signal input from the timing generation unit 54 (step ST3). For example, the switch 31 switches to the current detection sequence when the timing signal waveform A is at a low level.

[0039] The current range determination unit 55 calculates a current conversion value converted into a voltage by the product of the input current value output from the AD conversion unit 52 and the resistance value of the shunt resistor 22 (step ST4). Here, the input current value output from the AD conversion unit 52 is the current value of the input current signal I in input from the current input terminal 11.

[0040] Next, the current range determination unit 55 calculates the value of the difference between the current conversion value and the voltage value of the input voltage signal V in . After performing the voltage detection sequence in this way, at the stage where the switch 31 is switched to attempt the current detection sequence, the voltage value is known but the current value is unknown. Therefore, the shunt resistor to be selected first is the shunt resistor with the smallest resistance value among the shunt resistors 22a, 22b, and 22c.

[0041] The current range determination unit 55 determines whether there is an unselected shunt resistor among the shunt resistors 22a, 22b, and 22c (step ST6). If it is determined that there is an unselected shunt resistor and the shunt resistor can be reselected (step ST6; YES), the current range determination unit 55 selects an unselected shunt resistor from among the shunt resistors 22a, 22b, and 22c, and outputs a selection signal indicating the selected shunt resistor to the switch 21. Thereby, a series of processes from step ST1 are executed.

[0042] When it is determined that there is no unselected shunt resistor and the shunt resistor cannot be reselected (step ST6; NO), the current range determination unit 55 selects, from among the shunt resistors 22a, 22b, and 22c, the shunt resistor with the smallest difference value calculated in step ST5, and outputs a selection signal indicating the selected shunt resistor to the switch 21. Thereby, the current-voltage detection device 1 can suppress the ringing generated by switching between current detection and voltage detection. Note that the re-selection of the shunt resistor may be terminated when the difference value between the current conversion value and the input voltage value becomes equal to or less than the allowable value.

[0043] When the first current detection sequence is completed, as described above, the difference between the current conversion value and the voltage value of the input voltage signal V in can be calculated. Therefore, the operation is to either complete the flowchart as it is or return to voltage detection again. When the second voltage detection sequence is completed, the shunt resistor used in the second current detection sequence is clear in the first current detection sequence. For this reason, the shunt resistor 22 is selected so that the current conversion value is closest to the voltage value of the input voltage signal V in . Thereby, in the switching between current detection and voltage detection, the difference between the input voltage value and the current conversion value can be reduced, the magnitude and duration of the ringing can be suppressed, and thus, high-speed switching between current detection and voltage detection is possible.

[0044] So far, the shunt resistors 22a, 22b, and 22c having three different resistance values have been taken as an example, but the shunt resistor 22 may be a shunt resistor having two or more different resistance values. For example, when the resistance value Rsa of the shunt resistor 22a is 0.1 mΩ, the resistance value Rsb of the shunt resistor 22b is 10 mΩ, and the resistance value Rsc of the shunt resistor 22c is 1000 mΩ, only the shunt resistors 22b and 22c may be provided. Further, the shunt resistor 22 may be a shunt resistor having four or more different resistance values. These resistance values may be determined in advance by experiments or the like for the power supply assumed to be the detection target, for example.

[0045] As described above, the current-voltage detection device 1 according to the first embodiment includes a switch 31 that selects and switches an input path to be conducted to the output side from the input path from the current input terminal 11 and the input path from the voltage input terminal 12 according to a timing signal, shunt resistors 22a, 22b, and 22c, and a switch 21 that selects and switches a resistor to be conducted to the input path from the current input terminal 11 from the shunt resistors 22a, 22b, and 22c according to a selection signal. A timing generation unit 54 that outputs a timing signal to the switch 31, and a current range determination unit 55 that determines a shunt resistor for which the value of the difference between the current conversion value and the input voltage value is small from the shunt resistors 22a, 22b, and 22c, and outputs a selection signal for selecting the determined shunt resistor to the switch 21. Since the magnitude of ringing decreases when the value of the difference between the current conversion value and the input voltage value decreases, the current-voltage detection device 1 can suppress the ringing generated by switching between current detection and voltage detection. Further, although ringing occurs at the initial stage of switching, in the current-voltage detection device 1, since the magnitude of the ringing itself is small, it is possible to perform the switching between current detection and voltage detection in a short time, that is, high-speed switching is possible.

[0046] In Embodiment 1, the current-voltage detection device 1 includes a sample-and-hold circuit 42 that holds an analog signal input from the current input terminal 11 or the voltage input terminal 12 and output through the switch 31, and an AD conversion unit 52 that converts the analog signal output from the sample-and-hold circuit 42 into a digital signal. The current range determination unit 55 determines, based on the result of comparing the digital signal output from the AD conversion unit 52 and the timing signal output from the timing generation unit 54, a shunt resistor from among the shunt resistors 22a, 22b, and 22c for which the value of the difference between the input voltage value and the current conversion value detected in the voltage detection sequence is small. Thereby, the current-voltage detection device 1 can switch to a shunt resistor that suppresses ringing due to the switching between current detection and voltage detection.

[0047] In Embodiment 1, the current-voltage detection device 1 repeatedly performs a voltage detection sequence and a current detection sequence until the value of the difference between the input voltage value and the current conversion value becomes equal to or less than a reference value. The current range determination unit 55 determines a shunt resistor for which the value of the difference between the input voltage value and the current conversion value becomes equal to or less than the reference value. Thereby, the current-voltage detection device 1 can switch to a shunt resistor that suppresses ringing due to the switching between current detection and voltage detection.

[0048] The current-voltage detection method according to Embodiment 1 includes steps of: the current-voltage detection device 1 switching an input path to be conducted to the output side of the switch 31 to an input path from the voltage input terminal 12; detecting an input voltage value input from the voltage input terminal 12; switching the input path to be conducted to the output side of the switch 31 to an input path from the current input terminal 11; calculating a current conversion value converted into a voltage by the product of the input current value input from the current input terminal 11 and the value of the shunt resistor; calculating a value of the difference between the current conversion value and the input voltage value; and determining whether a shunt resistor for which the calculated value of the difference is small can be selected from among the shunt resistors 22a, 22b, and 22c. By executing this method, the current-voltage detection device 1 can suppress the ringing generated by switching between current detection and voltage detection.

[0049] Embodiment 2. FIG. 4 is a circuit diagram showing a configuration example of the current-voltage detection device 1A according to Embodiment 2. In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals and redundant descriptions are omitted. The current-voltage detection device 1A detects, for example, the voltage value of an AC voltage applied from a commercial power source to a load and the current value of an AC current. The current-voltage detection device 1A includes a current input terminal 11, a voltage input terminal 12, an input return terminal 13, a switch 21, a shunt resistor 22, a switch 31, an amplifier 41, a sample hold circuit 43, and a control unit 51A.

[0050] The sample hold circuit 43 is a circuit that holds an analog signal input from the current input terminal 11 or the voltage input terminal 12 and output through the switch 31. The sample hold circuit 43 is a circuit composed of a switch 43a, a resistor, and a capacitor. The switch 43a is an input adjustment switch that blocks or conducts the signal path from the sample hold circuit 43 to the AD conversion unit 52 according to a timing signal. The input side of the switch 43a is connected to the amplifier 41. One end of the resistor is connected to the output side of the switch 43a, and the other end is connected to one end of the capacitor. The other end of the capacitor is grounded. Further, the connection point between the other end of the resistor and the other end of the capacitor is connected to the subsequent AD conversion unit 52.

[0051] In the sample hold circuit 43, the analog input signal output from the amplifier 41 is blocked or conducted by the switch 43a. The analog input signal conducted by the switch 43a is connected to the capacitor via a resistor. When the switch 31 is switched, the charge of the analog input signal is accumulated in the capacitor, and further, when the switch 31 is switched again, the charge accumulated in the capacitor is discharged. That is, the sample hold circuit 42 is a circuit that holds the analog input signal for a certain period of time by accumulating charge in the capacitor. By using the sample hold circuit 42 and the AD conversion unit 52, it is possible to convert the analog input signal into a digital signal after holding it for a certain period of time.

[0052] The control unit 51A controls the overall operation of the current-voltage detection device 1. The control unit 51A includes an AD conversion unit 52, a data processing unit 53, a timing generation unit 54A, and a current range determination unit 55. For example, when the control unit 51A executes an application for current-voltage detection, the functions of the AD conversion unit 52, the data processing unit 53, the timing generation unit 54A, and the current range determination unit 55 are realized by the control unit 51A.

[0053] The timing generation unit 54A generates a timing signal for the switch 31, outputs the generated timing signal to the switch 31, generates a timing signal for the switch 43a, and outputs the generated timing signal to the switch 43a. For example, the timing generation unit 54A generates an on-off timing signal indicating a timing at which a ringing component included in the analog signal held in the sample hold circuit 43 is not input to the AD conversion unit 52, and outputs the generated on-off timing signal to the switch 43a as a timing signal. Thereby, the timing of taking in the analog signal from the sample hold circuit 43 to the AD conversion unit 52 can be controlled.

[0054] For example, the timing generating unit 54A generates a timing signal having a square wave whose high level and low level alternate at a constant cycle, as in the first embodiment. When this square wave timing signal is at a high level, it switches the input path to the input path from the voltage input terminal 12 in order to perform a voltage detection sequence, and when it is at a low level, it switches the input path to the input path from the current input terminal 11 in order to perform a current detection sequence.

[0055] 5 is a waveform diagram showing a voltage waveform, a ringing waveform, a first timing signal waveform A, and a second timing signal waveform C in the second embodiment. In FIG. 5, the waveform at the top is a voltage waveform switched by the switch 31, as in FIG. 2, and shows a signal waveform output from the AD conversion unit 52 to the data processing unit 53. When the first timing signal waveform A is at a high level, a voltage detection sequence is performed, and when it is at a low level, a current detection sequence is performed. When the second timing signal waveform C is at a high level, the switch 43a is turned on, and when it is at a low level, the switch 43a is turned off.

[0056] In the top voltage waveform, the portion corresponding to the high level section of the first timing signal waveform A is the input voltage signal V obtained in the voltage detection sequence. in The portion corresponding to the low level section of the first timing signal waveform A is the equivalent current value I obtained in the current detection sequence. ina , I inb and I inc In addition, the portion of the voltage waveform at the top that corresponds to the high level section of the second timing signal waveform C corresponds to the input voltage signal V in is in the range D.

[0057] For example, assume that the resistance value Rsa of the shunt resistor 22a is 0.1 mΩ, the resistance value Rsb of the shunt resistor 22b is 10 mΩ, and the resistance value Rsc of the shunt resistor 22c is 1000 mΩ. When the shunt resistor 22a is selected by the switch 21, a current equivalent value I inais obtained.

[0058] When the voltage value of the input voltage signal V in is several volts, a large level difference as indicated by the double arrows occurs between the current conversion value I ina and the voltage value of the input voltage signal V in . A large ringing waveform occurs in the voltage waveform due to the sudden potential change when the input path is switched by the switch 31. When the difference between the voltage value of the input voltage signal V in and the current conversion value I ina is large, a large ringing waveform occurs in the voltage waveform input to the amplifier 41 due to the sudden potential change when the input path is switched by the switch 31.

[0059] The ringing not only increases in amplitude as the potential difference increases, but also has a longer convergence time for the amplitude to converge. When an analog input signal including a ringing component is input to the AD conversion unit 52, a difference corresponding to the ringing component occurs in the current value or current value converted into a digital signal by the AD conversion unit 52. As a result, this becomes a factor of error in the input data input to the data processing unit 53. On the other hand, by controlling the switching of the switch 43a, the AD conversion unit 52 can acquire only the analog input signal corresponding to the range D after the ringing has converged.

[0060] When switched to the shunt resistor 22b by the switch 21, as shown in FIG. 5, a current conversion value I inb of several hundred mV is obtained. If the voltage value of the input voltage signal V in is several volts, a level difference as indicated by the double arrows occurs between the current conversion value I inb and the voltage value of the input voltage signal V in . In this case, a ringing waveform B of a smaller but medium size occurs in the voltage waveform compared to the case of ina . Also in this case, by controlling the switching of the switch 43a, the AD conversion unit 52 can acquire only the analog input signal corresponding to the range D after the ringing has converged.

[0061] ​ When switched to the shunt resistor 22c by the switch 21, as shown in FIG. 5, a current conversion value I in terms of several volts is obtained. inc is obtained. When the voltage value of the input voltage signal V in is several volts, the smallest level difference occurs between the current conversion value I inc and the voltage value of the input voltage signal V in as indicated by the double arrows. In this case, in the voltage waveform, the smallest ringing waveform B is generated. However, by controlling the switching of the switch 43a, the AD conversion unit 52 can acquire only the analog input signal corresponding to the range D after the ringing has converged. As a result, the current range determination unit 55 can select the shunt resistor 22c as the shunt resistor used for current detection and voltage detection of the AC power supplied from the power source, and the control unit 51A can acquire the analog input signal in the range D where the ringing has converged.

[0062] In the second embodiment, the current-voltage detection device 1A includes a switch 43a for blocking or conducting the signal path from the sample-and-hold circuit 43 to the AD conversion unit 52 according to a timing signal. The timing generation unit 54A generates a timing signal indicating the timing when the ringing component included in the analog signal held in the sample-and-hold circuit 43 is not input to the AD conversion unit 52, and outputs the timing signal to the switch 43a, thereby controlling the sampling timing of the analog signal from the sample-and-hold circuit 43 to the AD conversion unit 52. Since the switch 43a is switched at the timing when the ringing component is not input to the AD conversion unit 52, the current-voltage detection device 1A can suppress the ringing generated by the switching between current detection and voltage detection.

[0063] In addition, combinations of the respective embodiments or deformations of any constituent elements of the respective embodiments or omissions of any constituent elements in the respective embodiments are possible.

Industrial Applicability

[0064] The current-voltage detection device according to the present disclosure can be used, for example, for detecting current and voltage in a power control device.

Explanation of Signs

[0065] 1,1A current-voltage detection device, 11 current input terminal, 12 voltage input terminal, 13 input return terminal, 21,31,43a switches, 22,22a,22b,22c shunt resistors, 41 amplifier, 42,43 sample-and-hold circuits, 51,51A control units, 52 AD conversion unit, 53 data processing unit, 54,54A timing generation units, 55 current range determination unit.

Claims

1. An input switching switch that selects and switches an input path to be conducted to the output side from among an input path from a current input terminal and an input path from a voltage input terminal according to a timing signal; A plurality of shunt resistors having different resistance values from each other; A resistance switching switch that selects and switches a resistor to be conducted to the input path from the current input terminal from among the plurality of shunt resistors according to a selection signal; A timing generation unit that outputs the timing signal to the input switching switch; Among the plurality of shunt resistors, a current conversion value converted into a voltage by the product of the input current value of the current signal input from the current input terminal and the value of the shunt resistor, and the input voltage value of the input voltage signal input from the voltage input terminal, and a determination unit that outputs the selection signal for selecting the determined shunt resistor to the resistance switching switch by determining the shunt resistor having a small difference value. A current-voltage detection device characterized by the above.

2. A sample-and-hold circuit that holds an analog signal input from the current input terminal or the voltage input terminal and output through the input switching switch; An AD conversion unit that converts the analog signal output from the sample-and-hold circuit into a digital signal, and The determination unit acquires the input voltage signal and the current signal, which are the digital signals output from the AD conversion unit, and the timing signal output from the timing generation unit, and from among the plurality of shunt resistors, the input voltage value of the input voltage signal detected in the voltage detection sequence specified based on the timing signal and the current conversion value in the current detection sequence specified based on the timing signal. The shunt resistor having a small difference value is determined. The current-voltage detection device according to claim 1, characterized by the above.

3. Repeatedly perform the voltage detection sequence and the current detection sequence until the value of the difference between the input voltage value and the current conversion value becomes equal to or less than a reference value. The determination unit determines the shunt resistor when the value of the difference between the input voltage value and the current conversion value becomes equal to or less than the reference value. The current-voltage detection device according to claim 1, characterized in that.

4. The sample hold circuit is configured to include an input adjustment switch that blocks or conducts the analog signal input to the sample hold circuit according to an on-off timing signal. The timing generation unit generates the on-off timing signal indicating the timing when the ringing component included in the analog signal held in the sample hold circuit is not input to the AD conversion unit, and outputs the generated on-off timing signal to the input adjustment switch, thereby controlling the timing of taking in the analog signal from the sample hold circuit to the AD conversion unit. The current-voltage detection device according to claim 2, characterized in that.

5. A current-voltage detection method for the current-voltage detection device according to any one of claims 1 to 4, wherein The current-voltage detection device Switching the input path to be conducted to the output side of the input switching switch to the input path from the voltage input terminal; Detecting the input voltage value input from the voltage input terminal; Switching the input path to be conducted to the output side of the input switching switch to the input path from the current input terminal; Calculating the current conversion value converted into voltage by the product of the input current value input from the current input terminal and the value of the shunt resistor; Calculating the value of the difference between the current conversion value and the input voltage value; Selecting the shunt resistor with the smallest calculated difference value from among the plurality of shunt resistors. A current-voltage detection method characterized by the following.

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