WO2025013266A1 - Current/voltage detecting device and current/voltage detecting method - Google Patents

Abstract

A current/voltage detecting device (1) comprises: a switch (31) which, in accordance with a timing signal, selects and switches an input path to be electrically connected to an output side, from among an input path from a current input terminal (11) and an input path from a voltage input terminal (12); a switch (21) which, in accordance with a selection signal, selects and switches a resistance, from among shunt resistors (22a, 22b, 22c), to be electrically connected to the input path from the current input terminal (11); a timing generating unit (54) which outputs the timing signal to the switch (31); and a current range determining unit (55) which determines, from among the shunt resistors (22a, 22b, 22c), a shunt resistor which reduces the value of a difference between a current conversion value and an input voltage value, and which outputs, to the switch (21), the selection signal for selecting the determined shunt resistor.

Description

Current/voltage detection device and current/voltage detection method

This disclosure relates to a current/voltage detection device and a current/voltage detection method.

In power measurement, power is calculated as the product of current and voltage, so it is necessary to detect current and voltage simultaneously or by switching quickly between them. For example, if a power measurement device is equipped with a circuit for detecting current and a circuit for detecting voltage, it can detect the current value and the voltage value almost simultaneously, making it possible to measure power instantly.

However, in a device that has both current detection and voltage detection circuits in one device, if two separate circuits are provided for current detection and voltage detection from the analog signal input to the part that performs digital signal processing via AD conversion, the circuit size will increase.

In response to this, for example, the power control device described in Patent Document 1 shares the circuitry provided after the current detection unit and the voltage detection unit, and switches between the current detection unit and the voltage detection unit in the shared circuit using a switch. This makes it possible to prevent an increase in the circuit scale of the device.

In current detection, the current from the input terminal is passed through a shunt resistor and the amount of current (hereafter referred to as the current conversion value) is measured by converting it into a voltage, which is the product of the shunt resistance and the input current, i.e., the potential difference generated across the shunt resistor.

JP 2020-160245 A

The conventional technology described in Patent Document 1 had the problem that when switching from current detection to voltage detection, if a large level difference occurs between the current conversion value and the input voltage value, large ringing occurs in the voltage waveform. For example, since ringing occurs at the initial stage of switching, if switching occurs in a short time, the voltage signal including the ringing waveform is AD converted in the subsequent stage, which becomes a cause of error in the input data (current value or voltage value).

The present disclosure aims to solve the above problem by providing a current/voltage detection device that can suppress ringing that occurs when switching between current detection and voltage detection.

The current-voltage detection device according to the present disclosure includes an input changeover switch that selects and switches an input path to be connected to the output side from among the input path from the current input terminal and the input path from the voltage input terminal in accordance with a timing signal, a plurality of shunt resistors having different resistance values, a resistance changeover switch that selects and switches a resistor to be connected to the input path from the current input terminal from among the plurality of shunt resistors in accordance with a selection signal, a timing generation unit that outputs a timing signal to the input changeover switch, and a determination unit that determines from among the plurality of shunt resistors a shunt resistor that minimizes the difference between a current conversion value converted into a voltage by multiplying the input current value input from the current input terminal and the value of the shunt resistance, and an input voltage value input from the voltage input terminal, and outputs a selection signal to the resistance changeover switch to select the determined shunt resistor.

According to the present disclosure, from among a plurality of shunt resistors having mutually different resistance values, a shunt resistor that produces a small difference between a current equivalent value and an input voltage value is determined, and the determined shunt resistor is made conductive to the input path from the current input terminal.
As the difference between the current equivalent value and the input voltage value becomes smaller, the magnitude of the ringing also becomes smaller, so the current/voltage detection device according to the present disclosure can suppress ringing that occurs due to switching between current detection and voltage detection.

1 is a circuit diagram showing a configuration example of a current/voltage detection device according to a first embodiment; 3A to 3C are waveform diagrams showing a voltage waveform, a timing signal waveform, and a ringing waveform in the first embodiment. 4 is a flowchart showing a current/voltage detection method according to the first embodiment. FIG. 11 is a circuit diagram showing a configuration example of a current/voltage detection device according to a second embodiment. 11A to 11C are waveform diagrams showing a voltage waveform, a ringing waveform, a first timing signal waveform, and a second timing signal waveform in the second embodiment.

Embodiment 1.
Fig. 1 is a circuit diagram showing a configuration example of a current-voltage detection device 1 according to a first embodiment. In Fig. 1, the current-voltage detection device 1 detects, for example, a voltage value of an AC voltage and a current value of an AC current applied to a load from a commercial power source. 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.

1 is connected to the current input terminal 11. The current detection unit generates an analog input current signal Iin that represents the current value of 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 to generate _the input current signal _Iin .
1 is connected to the voltage input terminal 12. The voltage detection unit converts the voltage value of the AC power supplied from the power source to generate an analog input voltage signal _Vin . For example, the voltage detection unit generates the input voltage signal _Vin by performing 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.

The switch 21 is a resistor changeover switch that selects and switches the shunt resistor to be connected 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. For example, the resistance values are 100 times different, 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 significantly different resistance values, it is possible to select from these shunt resistors the shunt resistor that has the smallest difference between the current conversion value and the input voltage value, which will be described later.
The shunt resistors 22a, 22b, and 22c will be collectively referred to as shunt resistor 22 as appropriate.

The switch 31 is an input changeover switch that, in response to a timing signal, 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. An amplifier 41 is connected to the output side of the switch 31.
When the switch 31 connects the input path from the current input terminal 11 to the output side, the input current signal I _in input from the current input terminal 11 is output to the amplifier 41, and when the switch 31 connects the input path from the voltage input terminal 12 to the output side, the input voltage signal V _in input from the voltage input terminal 12 is output to the amplifier 41.

The amplifier 41 receives the analog input signal output from the switch 31 and amplifies the strength of the analog input signal. The analog input signal amplified by the amplifier 41 is output to a sample-and-hold circuit 42. The analog input signal is an input current signal _Iin or an input voltage signal _Vin .

The sample-and-hold circuit 42 is a circuit that holds an analog signal that is 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 made up 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. Furthermore, the connection point between the other end of the resistor and the other end of the capacitor is connected to the AD conversion unit 52 in the subsequent stage.

In the sample and hold circuit 42, the analog input signal output from the amplifier 41 is connected to a capacitor via a resistor. When the switch 31 is switched, the charge of the analog input signal is stored in the capacitor, and when the switch 31 is switched again, the charge stored in the capacitor is discharged. In other words, the sample and hold circuit 42 is a circuit that stores charge in the capacitor to hold the analog input signal for a fixed period of time. By using the sample and hold circuit 42 and the AD conversion unit 52, it is possible to hold the analog input signal for a fixed period of time and then convert it into a digital signal.

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, the control unit 51 executes a current/voltage detection application, whereby the control unit 51 realizes 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.

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, thereby generating a digital input signal made up of the sampled digital data.

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

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 square wave signal in which the high level and low level alternate at a constant cycle as the timing signal. When this square wave timing signal is at a high level, it switches to the input path from the voltage input terminal 12 to perform a voltage detection sequence, and when it is at a low level, it switches to the input path from the current input terminal 11 to perform a current detection sequence.

The current range determination unit 55 is a determination unit that determines, from among the shunt resistors 22a, 22b, and 22c, the shunt resistor that produces the smallest difference between the current conversion value and the input voltage value input from the voltage input terminal, and outputs a selection signal to the switch 21 to select the determined shunt resistor. The current conversion value is the product of the input current value input from the current input terminal 11 and the value of the shunt resistance, converted into a voltage.

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

In the current detection sequence, the current range determination unit 55 detects the input current value (A) by passing an input current through one of the shunt resistors 22a, 22b, and 22c. The current range determination unit 55 then calculates a current equivalent value (V) converted into voltage by multiplying the input current value (A) by the known resistance value (Ω) of the currently selected shunt resistor. In this way, the input current value can be uniquely determined if the voltage value input to the AD conversion unit 52 and the resistance value of the selected and used shunt resistor are known.

The current range determination unit 55 acquires the input current signal _Iin output from the AD conversion unit 52 to the data processing unit 53 in the current detection sequence, and obtains a current equivalent value converted into voltage by the product of the current value of the input current signal _Iin and the resistance value of the shunt resistor 22. Furthermore, the current range determination unit 55 acquires the input voltage signal _Vin 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 _Vin . Then, the current range determination unit 55 selects the shunt resistor to be switched next so that the level difference between the voltage value of the input voltage signal _Vin and the current equivalent value becomes small.

The current range determination unit 55 identifies whether the digital signal output from the AD conversion unit 52 is an input current signal _Iin or an input voltage signal _Vin , based on the timing signal obtained from the timing generation unit 54. For example, it is assumed that the timing signal is a square wave signal that alternates between high and low levels at a constant cycle, and that a voltage detection sequence is performed when the timing signal is at a high level, and a current detection sequence is performed when the timing signal is at a low level. In this case, the current range determination unit 55 determines a shunt resistance that reduces the difference between the input voltage value detected in the voltage detection sequence performed when the timing signal is at a high level and the current equivalent value.

Furthermore, the current/voltage detection device 1 may repeat the voltage detection sequence and the current detection sequence until the difference between the input voltage value and the current conversion value becomes equal to or less than a reference value, and in the repetition of these sequences, the current range determination unit 55 may determine a shunt resistor for which the difference between the input voltage value and the current conversion value becomes equal to or less than the reference value. This makes it possible to switch to a shunt resistor that suppresses ringing caused by switching between current detection and voltage detection.

FIG. 2 is a waveform diagram showing a voltage waveform, timing signal waveform A, and ringing waveform B in embodiment 1. In FIG. 2, the top waveform is a voltage waveform that is switched by switch 31, and shows the signal waveform output from AD conversion unit 52 to data processing unit 53. When 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.

In the top voltage waveform, the portion corresponding to the high level section of timing signal waveform A is the voltage value of input voltage signal _Vin obtained in the voltage detection sequence, and the portion corresponding to the low level section of timing signal waveform A shows the current equivalent values _Iina , _Iinb , and _Iinc obtained in the current detection sequence.

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 _Iina of several mV is obtained as shown in FIG.

When the voltage value of the input voltage signal _Vin is several volts, a large level difference occurs between the current equivalent value _Iina and the voltage value of the input voltage signal _Vin , as indicated by the double arrow. When the difference between the voltage value of the input voltage signal _Vin and the current equivalent value _Iina is large, a large ringing waveform B occurs in the voltage waveform input to the amplifier 41 due to a sudden change in potential when the input path is switched by the switch 31.

When the potential difference is large, not only does the ringing amplitude increase, but the convergence time for the amplitude to converge also increases. When an analog input signal containing a ringing component is input to the AD conversion unit 52, a difference corresponding to the ringing component is generated in the current value or current value converted into a digital signal by the AD conversion unit 52. This ultimately becomes a cause of error in the input data input to the data processing unit 53.

When the switch 21 is switched to the shunt resistor 22b, a current equivalent value _Iinb of several hundred mV is obtained, as shown in Fig. 2. If the voltage value of the input voltage signal _Vin is several volts, a level difference is generated between the current equivalent value _Iinb and the voltage value of the input voltage signal _Vin , as indicated by the double arrow. In this case, a ringing waveform B of moderate magnitude is generated in the voltage waveform, which is smaller than that of the current equivalent value _Iina .

When the switch 21 is switched to the shunt resistor 22c, a current equivalent value _Iinc of several volts is obtained, as shown in Fig. 2. When the voltage value of the input voltage signal _Vin is several volts, the smallest level difference occurs between the current equivalent value _Iinc and the voltage value of the input voltage signal _Vin , as indicated by the double arrow. In this case, the smallest ringing waveform B occurs in the voltage waveform. Therefore, the current range determination unit 55 selects the shunt resistor 22c as the shunt resistor 22 to be used for current detection and voltage detection of the AC power supplied from the power source.

Next, the current/voltage detection method according to the first embodiment will be described.
FIG. 3 is a flowchart showing the current/voltage detection method according to the first embodiment, and shows current/voltage detection by the current/voltage detection device 1.
The switch 31 switches the input path to be connected to the output side to the input path from the voltage input terminal 12 in accordance with the timing signal input from the timing generating unit 54 (step ST1). For example, when the timing signal waveform A is at a high level, the switch 31 switches to the voltage detection sequence.

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

The switch 31 switches the input path to be conducted to the output side to the input path from the current input terminal 11 in accordance with 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.

The current range determination unit 55 calculates a current equivalent value converted into a voltage by multiplying the input current value output from the AD conversion unit 52 by 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.

Next, the current range determination unit 55 calculates the difference between the current equivalent value and the voltage value of the input voltage signal _Vin (step ST5). After performing the voltage detection sequence in this way, when the switch 31 is switched to try 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.

The current range determination unit 55 determines whether or not 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 that a shunt resistor can be reselected (step ST6; YES), the current range determination unit 55 selects an unselected shunt resistor among the shunt resistors 22a, 22b, and 22c, and outputs a selection signal indicating the selected shunt resistor to the switch 21. This executes a series of processes from step ST1.

If it is determined that there is no unselected shunt resistor and that a shunt resistor cannot be reselected (step ST6; NO), the current range determination unit 55 selects a shunt resistor that has the smallest difference value calculated in step ST5 from among the shunt resistors 22a, 22b, and 22c, and outputs a selection signal indicating the selected shunt resistor to the switch 21. This allows the current/voltage detection device 1 to suppress ringing that occurs due to switching between current detection and voltage detection.
The reselection of the shunt resistor may be terminated when the difference between the current conversion value and the input voltage value becomes equal to or less than an allowable value.

When the first current detection sequence is completed, as described above, the difference between the current equivalent value and the voltage value of the input voltage signal _Vin can be calculated. Then, the flow chart can be ended as it is, or the process can be returned to voltage detection again.
When the second voltage detection sequence is completed, the shunt resistor to be used in the second current detection sequence is known from the first current detection sequence, so the shunt resistor 22 is selected so that the current equivalent value is closest to the voltage value of the input voltage signal _Vin .
As a result, when switching between current detection and voltage detection, the difference between the input voltage value and the current equivalent value can be reduced, the magnitude and duration of ringing can be suppressed, and high-speed switching between current detection and voltage detection can be achieved.

Although the shunt resistors 22a, 22b, and 22c having three different resistance values have been given as examples so far, the shunt resistor 22 may be a shunt resistor having two or more different resistance values. For example, if 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.
The shunt resistor 22 may be a shunt resistor having four or more different resistance values. These resistance values are determined in advance, for example, by experiments for the power supply expected to be detected.

As described above, the current-voltage detection device 1 according to the first embodiment includes a switch 31 that selects and switches the 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, a switch 21 that selects and switches the 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 from the shunt resistors 22a, 22b, and 22c that reduces the difference between the current conversion value and the input voltage value, and outputs a selection signal to the switch 21 to select the determined shunt resistor. When the difference between the current conversion value and the input voltage value is reduced, the magnitude of ringing is also reduced, so the current-voltage detection device 1 can suppress ringing that occurs due to switching between current detection and voltage detection. In addition, ringing occurs in the initial stage of switching, but in the current/voltage detection device 1, the magnitude of the ringing itself is small, so switching between current detection and voltage detection can be performed in a short time, i.e., high-speed switching is possible.

In the first embodiment, 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. Based on the result of comparing the digital signal output from the AD conversion unit 52 with 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 the shunt resistor that reduces the difference between the input voltage value detected in the voltage detection sequence and the current conversion value. This allows the current-voltage detection device 1 to switch to a shunt resistor that suppresses ringing caused by switching between current detection and voltage detection.

In the first embodiment, the current-voltage detection device 1 repeats a voltage detection sequence and a current detection sequence until 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 resistance at which the difference between the input voltage value and the current conversion value becomes equal to or less than a reference value. This allows the current-voltage detection device 1 to switch to a shunt resistance that suppresses ringing caused by switching between current detection and voltage detection.

The current/voltage detection method according to the first embodiment includes the steps of: by the current/voltage detection device 1 switching the input path to be conducted to the output side of the switch 31 to the input path from the voltage input terminal 12; detecting the 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 the input path from the current input terminal 11; calculating a current equivalent value converted into a voltage by multiplying the input current value input from the current input terminal 11 and the value of the shunt resistor; calculating a difference between the current equivalent value and the input voltage value; and determining whether a shunt resistor that results in a smaller calculated difference value can be selected from among the shunt resistors 22a, 22b, and 22c.
By implementing this method, the current/voltage detection device 1 can suppress ringing that occurs due to switching between current detection and voltage detection.

Embodiment 2.
Fig. 4 is a circuit diagram showing a configuration example of a current/voltage detection device 1A according to a second embodiment. In Fig. 4, the same components as those in Fig. 1 are given the same reference numerals and duplicated explanations are omitted. The current/voltage detection device 1A detects, for example, the voltage value of an AC voltage and the current value of an AC current applied to a load from a commercial power source. 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-and-hold circuit 43, and a control unit 51A.

The sample-and-hold circuit 43 is a circuit that holds an analog signal that is input from the current input terminal 11 or the voltage input terminal 12 and output via the switch 31. The sample-and-hold circuit 43 is a circuit that includes a switch 43a, a resistor, and a capacitor.
The switch 43a is an input adjustment switch that cuts off or connects the signal path from the sample-and-hold circuit 43 to the AD conversion unit 52 in accordance with 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. Furthermore, the connection point between the other end of the resistor and the other end of the capacitor is connected to the AD conversion unit 52 in the subsequent stage.

In the sample and hold circuit 43, the analog input signal output from the amplifier 41 is cut off or conducted by the switch 43a. The analog input signal that is conducted by the switch 43a is connected to a capacitor via a resistor. When the switch 31 is switched, the charge of the analog input signal is stored in the capacitor, and when the switch 31 is switched again, the charge stored in the capacitor is discharged. In other words, the sample and hold circuit 42 is a circuit that stores charge in the capacitor to hold the analog input signal for a fixed period of time. By using the sample and hold circuit 42 and the AD conversion unit 52, it is possible to hold the analog input signal for a fixed period of time and then convert it into a digital signal.

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, the control unit 51A executes a current/voltage detection application, whereby the control unit 51A realizes 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.

The timing generation unit 54A generates a timing signal for the switch 31 and outputs the generated timing signal to the switch 31, and also generates a timing signal for the switch 43a and outputs the generated timing signal to the switch 43a.
For example, the timing generating unit 54A generates an on-off timing signal indicating the timing at which 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 generated on-off timing signal to the switch 43a as a timing signal. This makes it possible to control the timing at which the analog signal is taken in from the sample-and-hold circuit 43 to the AD conversion unit 52.

For example, similar to the first embodiment, the timing generation unit 54A generates a timing signal in the form of a square wave whose high level and low level alternate at a constant cycle. When this square wave timing signal is at a high level, it switches 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 to the input path from the current input terminal 11 in order to perform a current detection sequence.

FIG. 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 embodiment 2. In FIG. 5, the top waveform is a voltage waveform switched by switch 31, as in FIG. 2, and shows the signal waveform output from AD conversion unit 52 to data processing unit 53. When 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 second timing signal waveform C is at a high level, switch 43a is conductive, and when it is at a low level, switch 43a is cut off.

In the voltage waveform at the top, the portion corresponding to the high level section of the first timing signal waveform A indicates the voltage value of the input voltage signal _Vin obtained in the voltage detection sequence, and the portion corresponding to the low level section of the first timing signal waveform A indicates the current equivalent values _Iina , _Iinb , and _Iinc obtained in the current detection sequence. Also, in the voltage waveform at the top, the portion corresponding to the high level section of the second timing signal waveform C indicates the range D of the input voltage signal _Vin output to the AD conversion unit 52.

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 _Iina of several mV is obtained as shown in FIG.

When the voltage value of the input voltage signal _Vin is several volts, a large level difference occurs between the current equivalent value _Iina and the voltage value of the input voltage signal _Vin , as indicated by the double arrow. When the difference between the voltage value of the input voltage signal _Vin and the current equivalent value _Iina is large, a large ringing waveform occurs in the voltage waveform input to the amplifier 41 due to a sudden change in potential when the input path is switched by the switch 31.

When the potential difference is large, not only does the ringing amplitude increase, but the convergence time for the amplitude to converge also increases. When an analog input signal containing a ringing component is input to the AD conversion unit 52, a difference corresponding to the ringing component is generated 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.
In response to this, by controlling the switching of the switch 43a, the AD conversion section 52 can obtain only the analog input signal that corresponds to range D after the ringing has converged.

When the switch 21 is switched to the shunt resistor 22b, a current equivalent value _Iinb of several hundred mV is obtained, as shown in Fig. 5. If the voltage value of the input voltage signal _Vin is several volts, a level difference is generated between the current equivalent value _Iinb and the voltage value of the input voltage signal _Vin , as indicated by the double arrow. In this case, a ringing waveform B of moderate magnitude is generated in the voltage waveform, which is smaller than that of the current equivalent value _Iina .
Even in this case, by controlling the switching of the switch 43a, the AD conversion unit 52 can obtain only the analog input signal corresponding to the range D after the ringing has converged.

When the switch 21 is switched to the shunt resistor 22c, a current equivalent value _Iinc of several volts is obtained as shown in Fig. 5. When the voltage value of the input voltage signal _Vin is several volts, the smallest level difference occurs between the current equivalent value _Iinc and the voltage value of the input voltage signal _Vin , as shown by the double arrow. In this case, the smallest ringing waveform B occurs in the voltage waveform, but by controlling the switching of the switch 43a, the AD conversion unit 52 can obtain 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 22 used for current detection and voltage detection of the AC power supplied from the power source, and the control unit 51A can obtain the analog input signal in the range D after the ringing has converged.

In the second embodiment, the current-voltage detection device 1A includes a switch 43a for blocking or connecting 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 at which the ringing component contained 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 timing of taking in the analog signal from the sample-and-hold circuit 43 to the AD conversion unit 52. Because the switch 43a is switched at a timing at which the ringing component is not input to the AD conversion unit 52, the current-voltage detection device 1A can suppress ringing that occurs due to switching between current detection and voltage detection.

It is possible to combine the embodiments, modify any of the components in each embodiment, or omit any of the components in each embodiment.

The current/voltage detection device disclosed herein can be used, for example, to detect current/voltage in a power control device.

1, 1A current and voltage detection device, 11 current input terminal, 12 voltage input terminal, 13 input return terminal, 21, 31, 43a switch, 22, 22a, 22b, 22c shunt resistor, 41 amplifier, 42, 43 sample and hold circuit, 51, 51A control unit, 52 AD conversion unit, 53 data processing unit, 54, 54A timing generation unit, 55 current range determination unit.

Claims (5)

an input changeover switch that selects and switches an input path to be conducted to an output side from among an input path from a current input terminal and an input path from a voltage input terminal in accordance with a timing signal;
A plurality of shunt resistors having different resistance values;
a resistor changeover switch that selects and switches a resistor to be connected to an input path from the current input terminal from among the plurality of shunt resistors in accordance with a selection signal;
a timing generation unit that outputs the timing signal to the input changeover switch;
a determination unit that determines, from among the plurality of shunt resistors, the shunt resistor that produces the smallest difference between a current equivalent value, converted into voltage by multiplying an input current value of a current signal input from the current input terminal and a value of the shunt resistor, and an input voltage value of an input voltage signal input from the voltage input terminal, and outputs the selection signal to the resistance changeover switch to select the determined shunt resistor. 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 changeover switch;
an AD conversion unit that converts the analog signal output from the sample-and-hold circuit into a digital signal;
2. The current/voltage detection device according to claim 1, wherein the determination unit determines, from among the multiple shunt resistors, the shunt resistor that results in the smallest difference between the input voltage value detected in a voltage detection sequence and the current conversion value, based on a result of comparing the digital signal output from the AD conversion unit and the timing signal output from the timing generation unit. a voltage detection sequence and a current detection sequence are repeatedly performed until a difference between the input voltage value and the current equivalent value becomes equal to or less than a reference value;
2 . The current/voltage detection device according to claim 1 , wherein the determination unit determines the shunt resistor for which a difference between the input voltage value and the current equivalent value is equal to or smaller than the reference value. an input adjustment switch that cuts off or connects a signal path from the sample-and-hold circuit to the AD conversion unit in accordance with an on/off timing signal;
3. The current/voltage detection device according to claim 2, wherein the timing generation unit generates the on/off timing signal indicating a timing at which a ringing component contained in the analog signal held in the sample-and-hold circuit is not input to the AD conversion unit, and controls a timing at which the analog signal is taken in from the sample-and-hold circuit to the AD conversion unit by outputting the generated on/off timing signal to the input adjustment switch. A current/voltage detection method for the current/voltage detection device according to any one of claims 1 to 4, comprising:
The current/voltage detection device is
switching an input path to be conducted to an output side of the input changeover switch to an input path from the voltage input terminal;
detecting the input voltage value inputted from the voltage input terminal;
switching an input path to be conducted to an output side of the input changeover switch to an input path from the current input terminal;
calculating the current equivalent value converted into a voltage by multiplying the input current value input from the current input terminal by the value of the shunt resistor;
calculating a difference between the current equivalent value and the input voltage value;
selecting, from among the plurality of shunt resistors, the shunt resistor that provides the smallest calculated difference value.

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