current sensor

Abstract

A current sensor that detects current based on a terminal voltage and a resistance value of a shunt resistor (4) includes a resistance value correction circuit (25, 75, 95, 106, 116, 126, 136) having a correction resistor (5, 6), a signal application unit (15, 15a, 15b, 15c, 15d, 74, 74a, 74b), a voltage detection unit (22, 102) that detects a terminal voltage of a portion of the shunt resistor and the correction resistor in a first time period and detects a terminal voltage of the entire correction resistor in a second time period, and a correction unit (24) that corrects a resistance value for current detection based on a calculated resistance value of the shunt resistor. As a plurality of correction resistors are disposed farther from the shunt resistor, the resistance values and resistance accuracy of the correction resistors are higher.

Description

Technical Field

[0001] This disclosure relates to a current sensor that detects a target current by using a terminal voltage provided in series in the path through which the target current flows and a current-detecting resistance value corresponding to the resistance value of the shunt resistor. Background Technology

[0002] As disclosed in Patent Documents 1 and 2, in a conceivable current sensor, the terminal voltage of a shunt resistor connected in series along the path through which the target current flows is measured and detected. The current to be detected is calculated based on the measured voltage and a current-sensing resistance value corresponding to the resistance value of the shunt resistor. In this case, since the resistance value of the shunt resistor may change due to degradation over time, the current-sensing resistance value used to calculate the current at any given time must be calibrated. In the following description, the conceivable current sensor disclosed in Patent Document 1 will be referred to as the first conceivable technology, and the conceivable current sensor disclosed in Patent Document 2 will be referred to as the second conceivable technology.

[0003] In a first conceivable technology, the resistance value used for current detection is calibrated as follows: Specifically, the first conceivable technology provides a sub-resistor and a calibration resistor. The sub-resistor allows the target current to flow within it, similar to a shunt resistor in normal operation. The calibration resistor prevents the target current from flowing within it during normal operation. According to this configuration, the sub-resistor degrades over time, similar to a shunt resistor, while the calibration resistor degrades almost entirely over time. In this first conceivable technology, the degree of degradation of the sub-resistor and the shunt resistor is obtained by comparing their resistance values ​​during calibration, and the resistance value for current detection is calibrated based on this degree of degradation.

[0004] In a second conceivable technique, the resistance value for current sensing is corrected as follows: The second conceivable technique has the following configuration: providing multiple shunt resistors from which a correction current is transferred, or providing an input terminal in the central portion of the shunt resistors and transferring the correction current from the input terminal. In the second conceivable technique, the terminal voltage of each resistor is measured when the correction current is transferred, and each resistance value is calculated based on the measurement results to correct the resistance value for current sensing.

[0005] Existing technical documents [Patent Literature] Patent Document 1: US Patent No. 8,779,777 Patent Document 2: US Patent No. 10473724 Summary of the Invention

[0006] In the first conceivable technique, the shunt resistor is not used for direct calibration. It is assumed that the sub-resistor degrades in the same way as the shunt resistor, and then the sub-resistor is used to indirectly calibrate the current sensing resistor value corresponding to the shunt resistor value. Therefore, in the first conceivable technique, if the above assumptions are not met, it may be impossible to calibrate the current sensing resistor value with high accuracy, resulting in a possible decrease in current sensing accuracy.

[0007] In the second conceivable technique, the configuration becomes complicated because multiple shunt resistors must be provided or input terminals must be provided in the middle section of the shunt resistors. Furthermore, in the second conceivable technique, it is difficult to sufficiently improve calibration accuracy, since the calibration accuracy of the resistor value used for current sensing largely depends on the accuracy of the calibration current.

[0008] In view of the above, this disclosure was made. The purpose of this disclosure is to provide a current sensor that can accurately calibrate the resistance value used for current sensing without complicating the configuration.

[0009] A current sensor detects a target current based on the terminal voltage of a shunt resistor connected in series in the path through which the target current flows and a current-sensing resistance value corresponding to the resistance value of the shunt resistor. The current sensor includes a resistance value correction circuit for correcting the current-sensing resistance value. The resistance value correction circuit includes multiple correction resistors, a signal application unit, a voltage detection unit, and a correction unit. All the multiple correction resistors are connected in series with the shunt resistor in a path different from the path through which the target current flows, and their resistance accuracy is higher than that of the shunt resistor.

[0010] A signal application unit applies an AC signal to all or part of a series circuit consisting of a shunt resistor and multiple correction resistors. A voltage detection unit detects the terminal voltages of the shunt resistors and a portion of the correction resistors during a first time period when the AC signal is applied to a portion of the series circuit including the shunt resistors. Furthermore, the voltage detection unit detects the terminal voltages of all correction resistors during a second time period when the AC signal is applied to the entire series circuit. A correction unit calculates the resistance value of the shunt resistor based on the detected terminal voltage values ​​from the voltage detection unit during the first and second time periods, and also corrects the detected resistance value based on the calculated resistance value as the calculated resistance of the shunt resistor.

[0011] With this configuration, the detected resistance value can be directly calibrated using a shunt resistor, without the need for indirect calibration using a sub-resistor as in the first conceivable technology. Furthermore, unlike the second conceivable technology, this configuration eliminates the need for multiple shunt resistors and an input terminal in the center of the shunt resistors; only one shunt resistor is required, simplifying the overall configuration of the current sensor.

[0012] Furthermore, based on the above configuration, the accuracy of calculating the resistance value and the accuracy of correcting the resistance value depend heavily on the accuracy of the resistance value of the correction resistor, which is positioned far from the shunt resistor in the series circuit, and the accuracy of the voltage detection unit in detecting the terminal voltage. In this case, the resistance values ​​and accuracy of multiple correction resistors are higher because they are further away from the shunt resistor in the series circuit. Generally, it may be difficult to accurately form resistors with small resistance values, but it may be relatively easy to accurately form resistors with large resistance values.

[0013] Therefore, based on the above configuration, the accuracy of the correction resistor value, which is far from the shunt resistor, can be significantly improved. This accuracy is highly correlated with the correction accuracy of the detection resistor value, resulting in a substantial improvement in the correction accuracy of the detection resistor value. Thus, with the above configuration, excellent results can be achieved: the detection resistor value can be corrected with high accuracy without complicating the overall configuration of the current sensor. Attached Figure Description

[0014] The above and other objects, features, and advantages of this disclosure will become more apparent when the following detailed embodiments are given with reference to the accompanying drawings. In the drawings: Figure 1 This is a schematic diagram illustrating the configuration of the current sensor according to the first embodiment; Figure 2 This is an illustration showing a specific first configuration example of the signal application unit according to the first embodiment; Figure 3 This is an illustration showing a specific second configuration example of the signal application unit according to the first embodiment; Figure 4 This is a specific first configuration example of each synchronization detection circuit according to the first embodiment; Figure 5 This is a specific second configuration example of each synchronization detection circuit according to the first embodiment; Figure 6 This is a schematic diagram illustrating the configuration of the current sensor according to the second embodiment; Figure 7 This is an illustration showing a specific first configuration example of the signal application unit according to the second embodiment; Figure 8This is an illustration showing a specific second configuration example of the signal application unit according to the second embodiment; Figure 9 This is a schematic diagram illustrating the configuration of a current sensor according to a third embodiment; Figure 10 This is a schematic diagram illustrating the configuration of the current sensor according to the fourth embodiment; Figure 11 This is a schematic diagram illustrating the configuration of a current sensor switched to a first connection state according to the fourth embodiment; Figure 12 This is a schematic diagram illustrating the configuration of a current sensor switched to a second connection state according to the fourth embodiment; Figure 13 This is a schematic diagram illustrating the configuration of the current sensor according to the fifth embodiment; Figure 14 This is a schematic diagram illustrating the configuration of the current sensor according to the sixth embodiment; Figure 15 This is a schematic diagram illustrating the configuration of the current sensor according to the seventh embodiment; Figure 16 This is an illustration showing a specific first configuration example of the signal application unit according to the eighth embodiment; and Figure 17 This is an illustration showing a specific second configuration example of the signal application unit according to the eighth embodiment. Detailed Implementation

[0015] Embodiments of this disclosure will now be described with reference to the accompanying drawings. In each embodiment, substantially the same components are indicated by the same reference numerals and their description will be omitted.

[0016] (First embodiment) The following is for reference. Figures 1 to 5 The first embodiment is described.

[0017] (Overall configuration) Figure 1 The current sensor 1 shown in this embodiment is mounted on a vehicle, such as an automobile, and detects a target current, i.e., the current flowing through a measurement target 2. The measurement target 2 can be a battery, such as a main engine battery that supplies power to the drive unit to drive the vehicle, an auxiliary battery that supplies power to the vehicle's auxiliary devices, a DC / DC converter, etc. The DC / DC converter supplies power to an electric motor that generates driving force for driving the vehicle, and together with the electric motor, constitutes the aforementioned drive unit.

[0018] In this configuration, load 3 is connected in series to the measuring target 2, and a loop circuit is configured consisting of the measuring target 2, load 3, and a switch (not shown). When the measuring target 2 is the aforementioned battery, load 3 can be, for example, the aforementioned motor, the aforementioned DC / DC converter, or an electric compressor. Furthermore, when the measuring target 2 is the aforementioned DC / DC converter, load 3 can be, for example, the aforementioned motor.

[0019] The current sensor 1 includes a shunt resistor 4, calibration resistors 5 and 6, a first signal application unit 7, a second signal application unit 8, a first voltage detection unit 9, a second voltage detection unit 10, a third voltage detection unit 11, and a control unit 12. One terminal of the shunt resistor 4 is connected to the high-potential side terminal of the measurement target 2 via a load 3, and the other terminal is connected to ground, which serves as a reference potential for the circuit, and the low-potential side terminal of the measurement target 2. That is, the shunt resistor 4 is provided in series with the path through which the target current flows. The current sensor 1 uses the terminal voltage of the shunt resistor 4 provided in this way and the detection resistance value corresponding to the resistance value of the shunt resistor 4 to detect the target current.

[0020] One terminal of the calibration resistor 5 is connected to the first signal application unit 7, and the other terminal is connected to one terminal of the shunt resistor 4. One terminal of the calibration resistor 6 is connected to the second signal application unit 8, and the other terminal is connected to one terminal of the calibration resistor 5. That is, calibration resistors 5 and 6 are all connected in series with the shunt resistor 4 in a path different from the path through which the target current flows. In this case, since the target current is relatively large, the resistance value of the shunt resistor 4 is relatively small, for example, on the order of μΩ.

[0021] On the other hand, since the relatively large target current does not flow through the calibration resistors 5 and 6, their resistance values ​​are relatively large, for example, on the order of mΩ. Typically, it may be difficult to precisely form resistors with small resistance values, but it may be relatively easy to precisely form resistors with large resistance values. Therefore, in this embodiment, the resistance accuracy of calibration resistors 5 and 6 is sufficiently higher than the resistance accuracy of shunt resistor 4. As described above, the current sensor 1 of this embodiment includes multiple calibration resistors, specifically two calibration resistors, all of which are connected in series with shunt resistor 4 in a path different from the path through which the target current flows, and the resistance accuracy of each calibration resistor is higher than that of shunt resistor 4.

[0022] When calibrating the detection resistor value, which will be described later, the first signal application unit 7 applies a pulsed or sinusoidal AC signal to a portion of the series circuit of the shunt resistor 4 and the calibration resistors 5 and 6 (specifically, the series circuit of the shunt resistor 4 and the calibration resistor 5 during calibration). In other words, the first signal application unit 7 applies the same AC signal to the shunt resistor 4 and the calibration resistor 5 during calibration. In this case, the first signal application unit 7 is configured as a current source for supplying AC power from the power line 13 supplying the power supply voltage VDD1 to the series circuit of the shunt resistor 4 and the calibration resistor 5.

[0023] During calibration, the second signal application unit 8 applies a pulsed or sinusoidal AC signal to the entire series circuit of the shunt resistor 4 and the calibration resistors 5 and 6. In other words, the second signal application unit 8 applies the same AC signal to the shunt resistor 4 and the calibration resistors 5 and 6 during calibration. In this case, the second signal application unit 8 is configured as a current source that supplies AC power from the power supply line 14, which supplies power supply voltage VDD2 (a higher voltage than power supply voltage VDD1), to the series circuit of the shunt resistor 4 and the calibration resistors 5 and 6. In this embodiment, the power supply voltage VDD1 is set to, for example, approximately +1V, and the power supply voltage VDD2 is set to, for example, approximately +5V.

[0024] As described above, in this embodiment, the first signal application unit 7 and the second signal application unit 8 apply AC signals to all or part of the series circuit of the shunt resistor 4 and the plurality of correction resistors 5 and 6, and act as signal application unit 15. Hereinafter, the time period during which the first signal application unit 7 applies AC signals to the series circuit of the shunt resistor 4 and the correction resistors 5 is referred to as the first time period, and the time period during which the second signal application unit 8 applies AC signals to the shunt resistor 4 and the correction resistors 5 and 6 is referred to as the second time period.

[0025] The first voltage detection unit 9 detects the terminal voltage of the shunt resistor 4 during a first time period during calibration, and includes a first A / D converter 16 and a first synchronous detection circuit 17. In situations such as... Figure 1 In the accompanying drawings, the A / D converter is abbreviated as ADC. The first A / D converter 16 performs the following A / D conversion operation to detect the terminal voltage of the shunt resistor 4. That is, the first A / D converter 16 inputs a signal to each terminal of the shunt resistor 4, and by performing A / D conversion on each signal, outputs the voltage difference between each terminal of the shunt resistor 4, that is, a digital signal corresponding to the voltage between the terminals of the shunt resistor 4. In this way, the digital signal output from the first A / D converter 16 is the signal corresponding to the terminals of the shunt resistor 4.

[0026] The first synchronous detection circuit 17 receives the digital signal output from the first A / D converter 16 and synchronously detects a signal with the same frequency as the AC signal in the first signal application unit 7, and extracts that signal. Then, the first synchronous detection circuit 17 outputs the extracted signal to the control unit 12. The output signal of the first synchronous detection circuit 17 corresponds to the terminal voltage of the shunt resistor 4. In this way, during the first correction time period, the first voltage detection unit 9 is configured to detect the terminal voltage of the shunt resistor 4 based on the output signal of the first synchronous detection circuit 17 and output a signal representing the detected value of the terminal voltage to the control unit 12.

[0027] When the detection resistor value (described later) is not calibrated, i.e., in the normal state, the first voltage detection unit 9 detects the terminal voltage of the shunt resistor 4 as follows. That is, in the normal state, the first A / D converter 16 performs A / D conversion operation in the same manner as during calibration. In this case, the digital signal output from the first A / D converter 16 is output to the control unit 12, but not input to the first synchronous detection circuit 17. In other words, in the normal state, the first voltage detection unit 9 detects the terminal voltage of the shunt resistor 4 based on the output signal of the first A / D converter 16 and outputs a signal representing the detected value of the terminal voltage to the control unit 12.

[0028] The second voltage detection unit 10 detects the terminal voltage of the correction resistor 5 during a first time period and a second time period during calibration, and includes a second A / D converter 18 and a second synchronous detection circuit 19. The second A / D converter 18 performs A / D conversion to detect the terminal voltage of the correction resistor 5. Specifically, the second A / D converter 18 inputs a signal to each terminal of the correction resistor 5, and by performing A / D conversion on each signal, outputs the voltage difference between each terminal of the correction resistor 5, i.e., a digital signal corresponding to the inter-terminal voltage of the correction resistor 5. In this way, the digital signal output from the second A / D converter 18 is the signal corresponding to the terminals of the correction resistor 5.

[0029] The second synchronization detection circuit 19 takes a digital signal output from the second A / D converter 18 as input, performs synchronization detection to extract a signal, and outputs the extracted signal to the control unit 12. In this case, the second synchronization detection circuit 19 performs synchronization detection at the same frequency as the AC signal in the first signal application unit 7 during a first time period, and at the same frequency as the AC signal in the second signal application unit 8 during a second time period. The output signal of the second synchronization detection circuit 19 corresponds to the terminal voltage of the correction resistor 5. In this way, during the first and second time periods of correction, the second voltage detection unit 10 is configured to detect the terminal voltage of the correction resistor 5 based on the output signal of the second synchronization detection circuit 19, and outputs a signal representing the detected value of the terminal voltage to the control unit 12.

[0030] The third voltage detection unit 11 detects the terminal voltage of the correction resistor 6 during a second time period during calibration, and includes a third A / D converter 20 and a third synchronous detection circuit 21. The third A / D converter 20 performs A / D conversion to detect the terminal voltage of the correction resistor 6. Specifically, the third A / D converter 20 inputs a signal to each terminal of the correction resistor 6 and, by performing A / D conversion on each signal, outputs a digital signal representing the voltage difference between each terminal of the correction resistor 6, i.e., the voltage between the terminals of the correction resistor 6. In this way, the digital signal output from the third A / D converter 20 is the signal corresponding to the terminals of the correction resistor 6.

[0031] The third synchronous detection circuit 21 receives the digital signal output from the third A / D converter 20 and synchronously detects a signal with the same frequency as the AC signal in the second signal application unit 8, and extracts that signal. Then, the third synchronous detection circuit 21 outputs the extracted signal to the control unit 12. The output signal of the third synchronous detection circuit 21 corresponds to the terminal voltage of the correction resistor 6. In this way, during the second correction time period, the third voltage detection unit 11 is configured to detect the terminal voltage of the correction resistor 6 based on the output signal of the third synchronous detection circuit 21 and output a signal representing the detected value of the terminal voltage to the control unit 12.

[0032] As described above, in this embodiment, the first voltage detection unit 9, the second voltage detection unit 10, and the third voltage detection unit 11 detect the terminal voltage of the shunt resistor 4 and a portion of the terminal voltage of the correction resistor 5 during a first time period when an AC signal is applied to the series circuit of the shunt resistor 4 and the correction resistor 5, and detect the terminal voltages of all correction resistors 5 and 6 during a second time period when an AC signal is applied to the shunt resistor 4 and the correction resistors 5 and 6. Therefore, the first voltage detection unit 9, the second voltage detection unit 10, and the third voltage detection unit 11 act as voltage detection unit 22.

[0033] In this configuration, the voltage detection unit 22 includes multiple A / D converters capable of performing A / D conversion operations to detect the terminal voltages of the shunt resistor 4 and the correction resistors 5 and 6; specifically, a first A / D converter 16, a second A / D converter 18, and a third A / D converter 20. Furthermore, in this configuration, the voltage detection unit 22 is configured to input signals from the terminals of the shunt resistor 4, perform synchronous detection to extract signals, and detect the terminal voltages of the shunt resistor 4 based on the extracted signals. Similarly, the voltage detection unit 22 is configured to input signals from the terminals of the correction resistors 5 and 6, perform synchronous detection to extract and output signals, and detect the terminal voltages of the correction resistors 5 and 6 based on the extracted signals.

[0034] The control unit 12 is configured as a semiconductor integrated circuit, such as the same ASIC as the voltage detection unit 22. ASIC is an abbreviation for Application-Specific Integrated Circuit. The control unit 12 includes functional blocks such as a current detection unit 23 and a correction unit 24. Each of these functional blocks is implemented in hardware. The control unit 12 can be configured as a semiconductor integrated circuit independent of the voltage detection unit 22. For example, the control unit 12 can be configured as a microcomputer including a CPU, RAM, ROM, etc. In this case, each of the aforementioned functional blocks is implemented by the CPU of the control unit 12, which executes a computer program stored in ROM, etc., to provide a process corresponding to the computer program, i.e., a process implemented in software. Alternatively, in this case, at least a portion of the functional blocks of the parking server device can be implemented in hardware.

[0035] The current detection unit 23 uses a signal corresponding to the terminal voltage of the shunt resistor 4 output from the first voltage detection unit 9 during normal operation and a detection resistance value corresponding to the resistance value of the shunt resistor 4 to detect the target current. The detection resistance value is set based on the initial resistance value of the shunt resistor 4 actually in use and is stored in advance in the memory provided in the control unit 12. Here, since the target current (a relatively large current) flows in the shunt resistor 4, the resistance value will change from the initial value due to degradation over time, etc.

[0036] Therefore, the detection resistance value can be corrected at any time through the operation of the correction unit 24. The correction unit 24 calculates the resistance value of the shunt resistor 4 based on the following signals: a signal representing the terminal voltage detection value of the shunt resistor 4 output from the voltage detection unit 22 in the first time period; a signal representing the terminal voltage detection value of the correction resistor 5 output from the voltage detection unit 22 in the first time period; a signal representing the terminal voltage detection value of the correction resistor 5 output from the voltage detection unit 22 in the second time period; a signal representing the terminal voltage detection value of the correction resistor 6 output from the voltage detection unit 22 in the second time period; a first correction resistance value corresponding to the resistance value of the correction resistor 5; and a second correction resistance value corresponding to the resistance value of the correction resistor 6. The correction unit 24 corrects the detection resistance value based on the calculated resistance value, which is the calculated resistance value of the shunt resistor 4. For example, the correction unit 24 can correct the detection correction value to match the calculated resistance value.

[0037] The first and second correction resistor values ​​mentioned above are the initial resistance values ​​of the actual correction resistors 5 and 6, and are stored in advance in the memory provided in the control unit 12. Since the target current does not flow in the correction resistors 5 and 6 under normal conditions, the resistance values ​​hardly change from the initial values ​​due to degradation over time. As described above, in the above configuration, the resistance correction circuit 25 for correcting the detected resistance values ​​is configured with correction resistors 5 and 6, signal application unit 15, voltage detection unit 22, and correction unit 24.

[0038] In this case, as the distance from the shunt resistor 4 increases in the series circuit of the shunt resistor 4 and the correction resistors 5 and 6, the resistance values ​​and accuracy of the correction resistors 5 and 6 become higher. That is, the resistance value of the correction resistor 6 is higher than that of the correction resistor 5. Furthermore, the resistance accuracy of the correction resistor 6 is higher than that of the correction resistor 5.

[0039] <Specific configuration of the signal application unit> Specific examples of the signal application unit 15 include Figure 2 The first configuration example shown Figure 3 The second configuration example shown, etc.

[0040] [1] First configuration example like Figure 2As shown, the first signal application unit 7a in the signal application unit 15a of the first configuration example includes a transistor 31, a resistor 32, a signal generation unit 33, an operational amplifier 34, etc. The transistor 31 is, for example, an N-channel MOSFET, whose drain is connected to the power supply line 13 via the resistor 32, and whose source is connected to ground via the correction resistor 5 and the shunt resistor 4.

[0041] Signal generation unit 33 generates and outputs a pulse wave signal or a sine wave signal with the same frequency as the AC current applied to the series circuit of shunt resistor 4 and correction resistor 5. The output signal of signal generation unit 33 is applied to the non-inverting input terminal of OP amplifier 34. The inverting input terminal of OP amplifier 34 is connected to the drain of transistor 31, and its output terminal is connected to the gate of transistor 31. According to the above configuration, transistor 31 is driven by OP amplifier 34, thereby applying an AC signal, i.e., alternating current, to the series circuit of shunt resistor 4 and correction resistor 5.

[0042] Furthermore, the second signal application unit 8a in the signal application unit 15a of the first configuration example includes a transistor 35, a resistor 36, a signal generation unit 37, an operational amplifier 38, etc. The transistor 35 is, for example, an N-channel MOSFET, whose drain is connected to the power supply line 14 via the resistor 36, and whose source is connected to ground via the correction resistor 5, the correction resistor 6, and the shunt resistor 4. The signal generation unit 37 generates and outputs a pulse wave signal or a sine wave signal with the same frequency as the alternating current applied to the series circuit of the shunt resistor 4 and the correction resistors 5 and 6.

[0043] The output signal of the signal generation unit 37 is applied to the non-inverting input terminal of the OP amplifier 38. The inverting input terminal of the OP amplifier 38 is connected to the drain of the transistor 35, and its output terminal is connected to the gate of the transistor 35. According to the above configuration, the transistor 35 is driven by the OP amplifier 38, so that an AC signal, i.e., alternating current, is applied to the series circuit of the shunt resistor 4 and the correction resistors 5 and 6.

[0044] As described above, in the signal application unit 15a of the first configuration example, both the first signal application unit 7a and the second signal application unit 8a are configured to be driven by an amplifier. In this case, transistor 31 and resistor 32 act as current sources for the first signal application unit 7a, and transistor 35 and resistor 36 act as current sources for the second signal application unit 8a.

[0045] [2] Second configuration example like Figure 3 As shown, in the first signal application unit 7b of the signal application unit 15b in the second configuration example, relative to Figure 2The first signal application unit 7a in the first configuration example shown is arranged with a buffer 41 instead of the OP amplifier 34, which differs from the first configuration example. In this case, the output signal of the signal generation unit 33 is applied to the input terminal of the buffer 41. The output terminal of the buffer 41 is connected to the gate of the transistor 31. According to the above configuration, the transistor 31 is driven by the buffer 41, such that an AC signal, i.e., alternating current, is applied to the series circuit of the shunt resistor 4 and the correction resistor 5.

[0046] Furthermore, in the second signal application unit 8b of the signal application unit 15b in the second configuration example, relative to... Figure 2 The second signal application unit 8a in the first configuration example shown is arranged with a buffer 42 instead of the OP amplifier 38, which differs from the first configuration example. In this case, the output signal of the signal generation unit 37 is applied to the input terminal of the buffer 42. The output terminal of the buffer 42 is connected to the gate of the transistor 35. According to the above configuration, the transistor 35 is driven by the buffer 42, such that an AC signal, i.e., alternating current, is applied to the series circuit of the shunt resistor 4 and the correction resistors 5 and 6. As described above, both the first signal application unit 7b and the second signal application unit 8b in the signal application unit 15a of the second configuration example are driven by buffers.

[0047] [3] Features of each configuration example According to the first configuration example of the amplifier drive configuration, the drain voltages of transistors 31 and 35 are controlled to constant values ​​by the operation of OP amplifiers 34 and 38. This gives the first configuration example an advantage over the second configuration example of the buffer drive configuration, allowing for improved accuracy of the AC current applied to the series circuit of shunt resistor 4 and correction resistors 5 and 6. On the other hand, according to the second configuration example, the circuit size can be reduced to a smaller size by using buffers 41 and 42 instead of OP amplifiers 34 and 38, compared to the first configuration example.

[0048] <Specific configuration of each synchronous detection circuit> The specific configurations of the first synchronization detection circuit 17 and the second synchronization detection circuit 19 include, for example: Figure 4 The configuration shown is illustrated. Furthermore, the specific configurations of the second synchronization detection circuit 19 and the third synchronization detection circuit 21 include, for example... Figure 5 The configuration shown above. In the above configuration, the first synchronization detection circuit 17 and the second synchronization detection circuit 19 operate in the first time period, and the second synchronization detection circuit 19 and the third synchronization detection circuit 21 operate in the second time period. Therefore, the configuration and operation of each synchronization detection circuit operating in each of the first and second time periods will be described below.

[0049] [1] First time period During calibration, the specific configuration and operation of the first synchronous detection circuit 17 and the second synchronous detection circuit 19 in the first time period are as follows: Figure 4 As shown in the diagram. In this case, the AC signal, i.e., the AC current applied by the first signal application unit 7 to the series circuit of the shunt resistor 4 and the correction resistor 5, is defined as "Ia·cos(ωt)", the resistance value of the shunt resistor 4 is defined as R, and the resistance value of the correction resistor 5 is defined as R1. Here, ω is the angular frequency, and t is time.

[0050] like Figure 4 As shown, the first synchronization detection circuit 17 includes multipliers 51 and 52, low-pass filters 53 and 54, and an arithmetic unit 55. In this specification, the low-pass filter may be abbreviated as LPF. During the first time period of correction, when an AC signal is applied to the series circuit of the shunt resistor 4 and the correction resistor 5, a digital signal output from the first A / D converter 16 is input to each input terminal of the multipliers 51 and 52 of the first synchronization detection circuit 17. This digital signal corresponds to the terminal voltage of the shunt resistor 4 during the first time period of correction and is defined as “R·Ia·cos(ωt + ωt)”. )".

[0051] A cosine wave signal "cos(ωt)" is input to another input terminal of multiplier 51. A sine wave signal "-sin(ωt)" is input to another input terminal of multiplier 52. As a result, a signal with angular frequency ω is extracted as a DC component from each output signal of multipliers 51 and 52. The output signals of multipliers 51 and 52 are input to LPFs 53 and 54, respectively.

[0052] The output signal I of LPF 53 is a low-frequency signal proportional to the in-phase component of the input signal, and the output signal Q of LPF 54 is a low-frequency signal proportional to the quadrature-phase component of the input signal. Arithmetic unit 55 calculates the square root of the sum of the squares of signals I and Q, and outputs a signal representing the calculation result. The output signal of arithmetic unit 55 is represented as "R·Ia". The output signal of arithmetic unit 55 becomes the output signal of the first synchronization detection circuit 17 and is assigned to the correction unit 24 of control unit 12.

[0053] The second synchronous detection circuit 19 includes multipliers 56 and 57, low-pass filters 58 and 59, and an arithmetic unit 60. During the first time period of correction, when an AC signal is applied to the series circuit of the shunt resistor 4 and the correction resistor 5, a digital signal output from the second A / D converter 18 is input to each input terminal of the multipliers 56 and 57 of the second synchronous detection circuit 19. This digital signal corresponds to the terminal voltage of the correction resistor 5 during the first time period of correction and is defined as “R1·Ia·cos(ωt + ωt)”. 1).

[0054] A cosine wave signal "cos(ωt)" is input to another input terminal of multiplier 56. A sine wave signal "-sin(ωt)" is input to another input terminal of multiplier 57. As a result, a signal with angular frequency ω is extracted as a DC component from each output signal of multipliers 56 and 57. The output signals of multipliers 56 and 57 are input to LPFs 58 and 59, respectively.

[0055] The output signal I1 of LPF 58 is a low-frequency signal proportional to the in-phase component of the input signal, and the output signal Q1 of LPF 59 is a low-frequency signal proportional to the quadrature-phase component of the input signal. Arithmetic unit 60 calculates the square root of the sum of the squares of signals I1 and Q1 and outputs a signal representing the calculation result. The output signal of arithmetic unit 60 is represented as "R1·Ia". The output signal of arithmetic unit 60 becomes the output signal of the second synchronization detection circuit 19 and is assigned to the correction unit 24 of control unit 12.

[0056] [2] Second time period During calibration, the specific configuration and operation of the second synchronization detection circuit 19 and the third synchronization detection circuit 21 in the second time period are as follows: Figure 4 As shown in the figure. In this case, the AC signal, i.e. the second signal application unit 8, is applied to the series circuit of the shunt resistor 4 and the correction resistors 5 and 6 as the alternating current, which is defined as "Ib·cos(ωt)" and the resistance value of the correction resistor 6 is defined as R2.

[0057] like Figure 5 As shown, during the second time period of correction when an AC signal is applied to the series circuit of shunt resistor 4 and correction resistors 5 and 6, a digital signal output from the second A / D converter 18 is input to each input terminal of multipliers 56 and 57 of the second synchronous detection circuit 19. This digital signal corresponds to the terminal voltage of correction resistor 5 during the second time period of correction and is defined as “R1·Ib·cos(ωt + ... 1).

[0058] A cosine wave signal "cos(ωt)" is input to another input terminal of multiplier 56. A sine wave signal "-sin(ωt)" is input to another input terminal of multiplier 57. As a result, a signal with angular frequency ω is extracted as a DC component from each output signal of multipliers 56 and 57. The output signals of multipliers 56 and 57 are input to LPFs 58 and 59, respectively.

[0059] The output signal I1 of LPF 58 is a low-frequency signal proportional to the in-phase component of the input signal, and the output signal Q1 of LPF 59 is a low-frequency signal proportional to the quadrature-phase component of the input signal. Arithmetic unit 60 calculates the square root of the sum of the squares of signals I1 and Q1 and outputs a signal representing the calculation result. The output signal of arithmetic unit 60 is represented as "R1·Ib". The output signal of arithmetic unit 60 becomes the output signal of the second synchronization detection circuit 19 and is assigned to the correction unit 24 of control unit 12.

[0060] The third synchronous detection circuit 21 includes multipliers 61 and 62, low-pass filters 63 and 64, and an arithmetic unit 65. During the second time period of correction, when an AC signal is applied to the series circuit of shunt resistor 4 and correction resistors 5 and 6, a digital signal output from the third A / D converter 20 is input to each input terminal of multipliers 61 and 62 of the third synchronous detection circuit 21. This digital signal corresponds to the terminal voltage of correction resistor 6 during the second time period of correction and is defined as “R²·Ib·cos(ωt + ... 2).

[0061] A cosine wave signal "cos(ωt)" is input to another input terminal of multiplier 61. A sine wave signal "-sin(ωt)" is input to another input terminal of multiplier 62. As a result, a signal with angular frequency ω is extracted as a DC component from each output signal of multipliers 61 and 62. The output signals of multipliers 61 and 62 are input to LPFs 63 and 64, respectively.

[0062] The output signal I2 of LPF 63 is a low-frequency signal proportional to the in-phase component of the input signal, and the output signal Q2 of LPF 64 is a low-frequency signal proportional to the quadrature-phase component of the input signal. Arithmetic unit 65 calculates the square root of the sum of the squares of signals I2 and Q2, and outputs a signal representing the calculation result. The output signal of arithmetic unit 65 is represented as "R2·Ib". The output signal of arithmetic unit 65 becomes the output signal of the third synchronization detection circuit 21 and is assigned to the correction unit 24 of control unit 12.

[0063] <Specific Operation of the Correction Unit> The correction unit 24 calculates a resistance value based on each signal supplied from the first synchronization detection circuit 17, the second synchronization detection circuit 19, and the third synchronization detection circuit 21 during the first and second time periods, as described above. Specifically, the correction unit 24 divides the output signal "R1·Ia" of the first synchronization detection circuit 17 during the first time period by the output signal "R1·Ia" of the second synchronization detection circuit 19 during the first time period, so that the correction unit 24 obtains a value "R / R1" representing the ratio of each resistance value of the shunt resistor 4 and the correction resistor 5. Furthermore, the correction unit 24 divides the output signal "R1·Ib" of the second synchronization detection circuit 19 during the second time period by the output signal "R2·Ib" of the third synchronization detection circuit 21 during the second time period, so that the correction unit 24 obtains a value "R1 / R2" representing the ratio of each resistance value of the correction resistor 5 and the correction resistor 6.

[0064] Furthermore, the correction unit 24 obtains the value "R / R2", representing the ratio of each resistance value of the shunt resistor 4 and the correction resistor 6, by multiplying the value "R / R1" and the value "R1 / R2". Here, the resistance value R2 of the correction resistor 6 is a known value and is stored in advance in the memory of the control unit 12, etc. Therefore, the correction unit 24 multiplies the value "R / R2" obtained as described above by the pre-stored resistance value R2, so that it can calculate the current resistance value R of the shunt resistor 4, that is, calculate the resistance value.

[0065] The above embodiments provide the following effects.

[0066] According to this embodiment, the current sensor 1 detects a target current based on the terminal voltage of a shunt resistor 4 provided in series in the path through which the target current flows and the current detection resistance value corresponding to the resistance value of the shunt resistor 4. The current sensor includes a resistance value correction circuit 25 for correcting the current detection resistance value. The resistance value correction circuit 25 includes multiple correction resistors 5 and 6, a signal application unit 15, a voltage detection unit 22, and a correction unit 24. All of the multiple correction resistors 5 and 6 are connected in series with the shunt resistor 4 in a path different from the path through which the target current flows, and their resistance accuracy is higher than that of the shunt resistor 4.

[0067] The signal application unit 15 applies an AC signal to all or part of the series circuit of the shunt resistor 4 and the correction resistors 5 and 6. The voltage detection unit 22 detects the terminal voltages of the shunt resistor 4 and the correction resistor 5 during a first time period when the AC signal is applied to the shunt resistor 4 and the correction resistor 5. Furthermore, the voltage detection unit 22 detects the terminal voltages of the correction resistors 5 and 6 during a second time period when the AC signal is applied to the shunt resistor 4 and the correction resistors 5 and 6. The correction unit 24 calculates the resistance value of the shunt resistor 4 based on the terminal voltage values ​​detected by the voltage detection unit 22 during the first time period and the second time period, and also corrects the detected resistance value as the calculated resistance of the shunt resistor 4 based on the calculated resistance value.

[0068] With this configuration, the detection resistance value can be directly calibrated using the shunt resistor 4, without the need for indirect calibration using a sub-resistor as in the first conceivable technology. Furthermore, unlike the second conceivable technology, this configuration eliminates the need for multiple shunt resistors or an input terminal in the center of the shunt resistors; only one shunt resistor 4 is required, simplifying the overall configuration of the current sensor 1.

[0069] Furthermore, based on the above configuration, the accuracy of calculating the resistance value and the accuracy of correcting the resistance value depend heavily on the accuracy of the resistance value R2 of the correction resistor 6, which is positioned farthest from the shunt resistor 4 in the series circuit among the multiple correction resistors 5 and 6, and the accuracy of the voltage detection unit 22 in detecting the terminal voltage. In this case, the resistance values ​​and their accuracy of the multiple correction resistors 5 and 6 are higher because they are further away from the shunt resistor 4 in the series circuit. Generally, it may be difficult to accurately form resistors with small resistance values, but it may be relatively easy to accurately form resistors with large resistance values.

[0070] Therefore, based on the above configuration, the accuracy of the resistance value R2 of the calibration resistor 6, which is far from the shunt resistor 4, can be significantly improved. This accuracy is highly correlated with the calibration accuracy of the detection resistor value, resulting in a significant improvement in the calibration accuracy of the detection resistor value. Thus, according to the above embodiment, excellent results can be achieved, namely, the detection resistor value can be calibrated with high accuracy without complicating the configuration of the entire current sensor 1.

[0071] In this configuration, the voltage detection unit 22 receives the signal from the terminals of the shunt resistor 4, detects the signal synchronously at the same frequency as the AC signal, extracts the signal, and detects the terminal voltage of the shunt resistor 4 based on the extracted signal. Furthermore, the voltage detection unit 22 receives the signal from the terminals of the correction resistors 5 and 6, detects the signal synchronously at the same frequency as the AC signal, extracts the signal, outputs the signal, and detects the terminal voltage of the correction resistors 5 and 6 based on the extracted signal.

[0072] According to this configuration, the terminal voltages of shunt resistors 4 and correction resistors 5 and 6 are detected based on the extracted signal, which is detected synchronously at the same frequency as the AC signal applied to shunt resistors 4 and correction resistors 5 and 6. Therefore, according to this embodiment, the detection accuracy of the voltage detection unit 22 for each terminal voltage is limited but not reduced by noise, such as thermo-electromotive force and circuit-side offsets. As a result, the correction accuracy of the detected resistance value can be further improved.

[0073] Signal application unit 15 applies a pulse wave signal or a sinusoidal AC signal to all or part of the series circuit of shunt resistor 4 and correction resistors 5 and 6. When signal application unit 15 applies a sinusoidal AC signal, the configuration for generating the AC signal, specifically, the configuration of signal generation units 33 and 37, is complicated, but the signal only includes the desired frequency component as the AC signal. Therefore, the detection error of the voltage detection unit 22 for the detection value of each terminal voltage can be suppressed to a low level; in other words, the correction accuracy of the detected resistance value can be improved.

[0074] On the other hand, when the signal application unit 15 applies a pulsed AC signal, errors may occur in the voltage detection value of each terminal voltage by the voltage detection unit 22 because the AC signal includes harmonic components. However, the configuration for generating the AC signal can be simplified, specifically the configuration of the signal generation units 33 and 37.

[0075] The current sensor 1 of this embodiment has a configuration including multiple correction resistors 5 and 6. Alternatively, one of the correction resistors 5 and 6 can be removed from the current sensor 1 of this embodiment, and the configuration associated with one of the correction resistors 5 and 6 can also be removed, i.e., the configuration includes only one correction resistor. Even in such a case, it is believed that the correction accuracy of the detected resistance value can be improved as in this embodiment. Hereinafter, the configuration having such a correction resistor will be referred to as a comparative example. Here, according to this embodiment, the following effects that cannot be obtained in the comparative example can be obtained.

[0076] That is, in the comparative example, when increasing the detected value of the terminal voltage of the shunt resistor 4 during calibration to improve detection accuracy, the ratio of each resistance value of the shunt resistor 4 and the calibration resistor is set to, for example, "1:1000", "1:10000", etc., thus this ratio must be very large. Here, assuming that the voltage detection range of the ADC constituting the voltage detection unit 22 is within the same range, this detection range must be matched with the range that can detect the terminal voltage of the calibration resistor. Therefore, in the comparative example, it may be difficult to accurately detect each terminal voltage of the shunt resistor 4 and the calibration resistor unless an ADC with extremely high resolution is used.

[0077] On the other hand, in this embodiment, when the detected value of the terminal voltage of the shunt resistor 4 is increased during calibration to improve detection accuracy, the ratio of the resistance values ​​of the shunt resistor 4 and the calibration resistor 5, as well as the ratio of the resistance values ​​of the calibration resistors 5 and 6, can be suppressed to relatively small values, such as "1:100" or "1:10". Therefore, in this embodiment, even without using an ADC with extremely high resolution, using the same ADC as each ADC constituting the voltage detection unit 22, the terminal voltages of the shunt resistor 4 and the calibration resistors 5 and 6 can be detected with high accuracy, which is an excellent result.

[0078] (Second Embodiment) The following is for reference. Figures 6 to 8 The second embodiment is described.

[0079] (Overall configuration) like Figure 6 As shown in the figure, the current sensor 71 in this embodiment and Figure 1 The current sensor 1 shown in the first embodiment differs from the current sensor 1 shown in that a first signal application unit 72 and a second signal application unit 73 are provided instead of the first signal application unit 7 and the second signal application unit 8.

[0080] Similar to the first signal application unit 7, the first signal application unit 72 applies a pulse wave signal or a sinusoidal AC signal to the series circuit of the shunt resistor 4 and the correction resistor 5 during calibration. In this case, the first signal application unit 72 is configured as a voltage source to supply AC voltage to the series circuit of the shunt resistor 4 and the correction resistor 5. The second signal application unit 73 is configured as a voltage source to supply AC voltage to the series circuit of the shunt resistor 4 and the correction resistors 5 and 6. Similar to the second signal application unit 8, the second signal application unit 73 applies a pulse wave signal or a sinusoidal AC signal to the series circuit of the shunt resistor 4 and the correction resistors 5 and 6 during calibration. In this case, the second signal application unit 73 is configured as a voltage source to supply AC voltage to the series circuit of the shunt resistor 4 and the correction resistors 5 and 6.

[0081] As described above, in this embodiment, the first signal application unit 72 and the second signal application unit 73 apply AC signals to all or part of the series circuit of the shunt resistor 4 and the plurality of correction resistors 5 and 6, and act as the signal application unit 74. In the above configuration, the resistance value correction circuit 75 for correcting the detected resistance value is configured with the correction resistors 5 and 6, the signal application unit 74, the voltage detection unit 22, and the correction unit 24.

[0082] <Specific configuration of the signal application unit> Specific examples of the signal application unit 74 include Figure 7 The first configuration example shown Figure 8 The second configuration example shown, etc.

[0083] [1] First configuration example like Figure 7 As shown, the first signal application unit 72a in the signal application unit 74a of the first configuration example includes a transistor 81, a signal generation unit 82, an operational amplifier 83, etc. The transistor 81 is, for example, an N-channel MOSFET, whose drain is connected to the power line 84 supplied with power supply voltage VDD1, and whose source is connected to ground via a correction resistor 5 and a shunt resistor 4.

[0084] Signal generation unit 82 generates and outputs a pulse wave signal or a sine wave signal with the same frequency as the AC voltage applied to the series circuit of shunt resistor 4 and correction resistor 5. The output signal of signal generation unit 82 is applied to the non-inverting input terminal of OP amplifier 83. The inverting input terminal of OP amplifier 83 is connected to the source of transistor 81, and its output terminal is connected to the gate of transistor 81. According to the above configuration, transistor 81 is driven by OP amplifier 83, such that an AC signal, i.e., an alternating current voltage, is applied to the series circuit of shunt resistor 4 and correction resistor 5.

[0085] Furthermore, the second signal application unit 73a in the signal application unit 74a of the first configuration example includes a transistor 85, a signal generation unit 86, an operational amplifier 87, etc. The transistor 85 is, for example, an N-channel MOSFET, whose drain is connected to a power line 88 supplied with a power supply voltage VDD2, and whose source is connected to ground via correction resistors 5 and 6 and a shunt resistor 4.

[0086] Signal generation unit 86 generates and outputs a pulse wave signal or a sine wave signal with the same frequency as the AC voltage applied to the series circuit of shunt resistor 4 and correction resistors 5 and 6. The output signal of signal generation unit 86 is applied to the non-inverting input terminal of OP amplifier 87. The inverting input terminal of OP amplifier 87 is connected to the source of transistor 85, and its output terminal is connected to the gate of transistor 85. According to the above configuration, transistor 85 is driven by OP amplifier 87, such that an AC signal, i.e., an alternating current voltage, is applied to the series circuit of shunt resistor 4 and correction resistors 5 and 6. As described above, the first signal application unit 72a and the second signal application unit 73a in the signal application unit 74a of the first configuration example are both configured to be driven by amplifiers.

[0087] [2] Second configuration example like Figure 8 As shown, in the first signal application unit 72b of the signal application unit 74b in the second configuration example, relative to Figure 7 The first signal application unit 72a shown in the first configuration example is arranged with a buffer 89 instead of the OP amplifier 83, which differs from the first configuration example. In this case, the output signal of the signal generation unit 82 is applied to the input terminal of the buffer 89. The output terminal of the buffer 89 is connected to the gate of the transistor 81. According to the above configuration, the transistor 81 is driven by the buffer 89, such that an AC signal, i.e., an alternating current voltage, is applied to the series circuit of the shunt resistor 4 and the correction resistor 5.

[0088] Furthermore, in the second signal application unit 73b of the second configuration example signal application unit 74b, relative to... Figure 7 The second signal application unit 73a in the first configuration example shown is arranged with a buffer 90 instead of the OP amplifier 87, which differs from the first configuration example. In this case, the output signal of the signal generation unit 86 is applied to the input terminal of the buffer 90. The output terminal of the buffer 90 is connected to the gate of the transistor 85. According to the above configuration, the transistor 85 is driven by the buffer 90, such that an AC signal, i.e., an alternating current voltage, is applied to the series circuit of the shunt resistor 4 and the correction resistors 5 and 6. As described above, both the first signal application unit 72b and the second signal application unit 73b in the signal application unit 74b of the second configuration example are driven by buffers.

[0089] [3] Features of each configuration example According to the first configuration example of the amplifier drive configuration, the source voltages of transistors 81 and 85 are controlled to constant values ​​by the operation of OP amplifiers 83 and 87. This gives the first configuration example an advantage over the second configuration example of the buffer drive configuration, thereby improving the accuracy of the AC current voltage applied to the series circuit of shunt resistor 4 and correction resistors 5 and 6. On the other hand, according to the second configuration example, the circuit size can be reduced to a smaller size by using buffers 89 and 90 instead of OP amplifiers 83 and 87 compared to the first configuration example.

[0090] As described above, the current sensor 71 of this embodiment includes a resistance correction circuit 75, which performs the same operation as the resistance correction circuit 25 of the first embodiment, except that during correction in the first embodiment, all or part of the AC signal applied to the series circuit of the shunt resistor 4 and the correction resistors 5 and 6 changes from AC current to AC voltage. Therefore, in this embodiment, the detected resistance value can be corrected in the same manner as in the first embodiment, and the same effect as in the first embodiment can be obtained.

[0091] (Third embodiment) The following will refer to Figure 9 The third embodiment is described.

[0092] like Figure 9 As shown, the current sensor 91 in this embodiment has added... Figure 1 The current sensor 1 shown in the first embodiment has a switching unit 92, and has a control unit 93 instead of the control unit 12, which is different from the first embodiment. The switching unit 92 includes, for example, a multiplexer, and switches the connection state between each terminal of the shunt resistor 4, the correction resistors 5 and 6, and each input terminal of the voltage detection unit 22. The operation of the switching unit 92 is controlled by the control unit 93.

[0093] In the connection state of switching unit 92, each of the first voltage detection unit 9, the second voltage detection unit 10, and the third voltage detection unit 11 is switchable to detect the terminal voltage of each of the shunt resistor 4, the correction resistor 5, and the correction resistor 6. For example, the connection state of switching unit 92 can be switched such that the first voltage detection unit 9 detects the terminal voltage of the shunt resistor 4, the second voltage detection unit 10 detects the terminal voltage of the correction resistor 5, and the third voltage detection unit 11 detects the terminal voltage of the correction resistor 6. Alternatively, the connection state of switching unit 92 can be switched such that the first voltage detection unit 9 detects the terminal voltage of the shunt resistor 4, the second voltage detection unit 10 detects the terminal voltage of the correction resistor 6, and the third voltage detection unit 11 detects the terminal voltage of the correction resistor 5.

[0094] Furthermore, regarding the connection state of the switching units 92, for example, they can be switched such that the first voltage detection unit 9 detects the terminal voltage of the correction resistor 5, the second voltage detection unit 10 detects the terminal voltage of the shunt resistor 4, and the third voltage detection unit 11 detects the terminal voltage of the correction resistor 6. Regarding the connection state of the switching units 92, for example, they can be switched such that the first voltage detection unit 9 detects the terminal voltage of the correction resistor 5, the second voltage detection unit 10 detects the terminal voltage of the correction resistor 6, and the third voltage detection unit 11 detects the terminal voltage of the shunt resistor 4.

[0095] Regarding the connection state of the switching units 92, for example, they can be switched such that the first voltage detection unit 9 detects the terminal voltage of the correction resistor 6, the second voltage detection unit 10 detects the terminal voltage of the shunt resistor 4, and the third voltage detection unit 11 detects the terminal voltage of the correction resistor 5. Regarding the connection state of the switching units 92, for example, they can be switched such that the first voltage detection unit 9 detects the terminal voltage of the correction resistor 6, the second voltage detection unit 10 detects the terminal voltage of the correction resistor 5, and the third voltage detection unit 11 detects the terminal voltage of the shunt resistor 4.

[0096] Furthermore, the connection state of the switching unit 92 can be switched so that at least two of the first voltage detection unit 9, the second voltage detection unit 10, and the third voltage detection unit 11 detect the terminal voltage of the shunt resistor 4. Furthermore, the connection state of the switching unit 92 can be switched so that at least two of the first voltage detection unit 9, the second voltage detection unit 10, and the third voltage detection unit 11 detect the terminal voltage of the correction resistor 5. Furthermore, the connection state of the switching unit 92 can be switched so that at least two of the first voltage detection unit 9, the second voltage detection unit 10, and the third voltage detection unit 11 detect the terminal voltage of the correction resistor 6.

[0097] The difference between control unit 93 and control unit 12 is the addition of a gain error reduction unit 94. In the above configuration, the resistance correction circuit 95 for correcting the detection resistor value is configured with correction resistors 5 and 6, signal application unit 15, voltage detection unit 22, correction unit 24, switching unit 92, and gain error reduction unit 94. The gain error reduction unit 94 includes a first A / D converter 16 of the first voltage detection unit 9, a second A / D converter 18 of the second voltage detection unit 10, and a third A / D converter 20 of the third voltage detection unit 11, thereby reducing the gain error of each ADC.

[0098] In the following description, when it is not necessary to distinguish between the first A / D converter 16, the second A / D converter 18, and the third A / D converter 20, they can be collectively referred to as ADCs. Furthermore, in the following description, when it is not necessary to distinguish between the first voltage detection unit 9, the second voltage detection unit 10, and the third voltage detection unit 11, they can be collectively referred to as voltage detection units.

[0099] When the gain error reduction unit 94 is not performing the operation to reduce the gain error, the connection state of the switching unit 92 is switched so that the first voltage detection unit 9 detects the terminal voltage of the shunt resistor 4, the second voltage detection unit 10 detects the terminal voltage of the correction resistor 5, and the third voltage detection unit 11 detects the terminal voltage of the correction resistor 6. Then, the gain error reduction unit 94 can reduce the gain error of each ADC by switching the connection state of the switching unit 92 as follows.

[0100] That is, the gain error reduction unit 94, for example, switches the connection state of the switching unit 92 so that the terminal voltages of the two detection shunt resistors 4, correction resistors 5, or correction resistors 6 in the voltage detection unit are such that the gain error reduction unit 94 can reduce the relative gain error of each ADC based on the detected values ​​of the terminal voltages of the shunt resistors 4, correction resistors 5, or correction resistors 6 detected by each of the two voltage detection units. In this case, the gain error reduction unit 94 can perform correction, for example, to make the gains of the ADCs the same.

[0101] Furthermore, in the gain error reduction unit 94, for example, The connection state of the switching unit 92 is switched so that the first voltage detection unit 9 detects the terminal voltage of the shunt resistor 4, and the second voltage detection unit 10 detects the terminal voltage of the correction resistor 5. Then, the connection state of the switching unit 92 is switched again so that the first voltage detection unit 9 detects the terminal voltage of the correction resistor 5, and the second voltage detection unit 10 detects the terminal voltage of the shunt resistor 4. As a result, the gain error reduction unit 94 reduces the gain error of the first A / D converter 16 and the second A / D converter 18 based on the corresponding detection values ​​of the terminal voltages of the shunt resistor 4 detected by each of the first voltage detection unit 9 and the second voltage detection unit 10.

[0102] Furthermore, the gain error reduction unit 94 reduces the gain error of the first A / D converter 16 and the second A / D converter 18 based on the corresponding detected values ​​of the terminal voltages of the correction resistor 5 detected by each of the first voltage detection unit 9 and the second voltage detection unit 10. In these cases, the gain error reduction unit 94 can reduce the gain error by, for example, averaging the two detected values ​​to eliminate each gain error.

[0103] As described above, the resistance value correction circuit 95 of the current sensor 91 in this embodiment includes a gain error reduction unit 94, which is used to reduce the gain error of each of the first A / D converter 16 of the first voltage detection unit 9, the second A / D converter 18 of the second voltage detection unit 10, and the third A / D converter 20 of the third voltage detection unit 11. With this configuration, the gain errors of the first A / D converter 16, the second A / D converter 18, and the third A / D converter 20 can be reduced to a minimum, for example, 0.1%. Therefore, according to this embodiment, the detection accuracy of the voltage detection unit 22 for the terminal voltages of the shunt resistor 4 and the correction resistors 5 and 6 is further improved, resulting in further improvement in the correction accuracy of the detected resistance value.

[0104] (Fourth embodiment) The following is for reference. Figures 10 to 12 The fourth embodiment is described.

[0105] like Figure 10 As shown, the current sensor 101 in this embodiment and Figure 1 The difference in the current sensor 1 of the first embodiment shown is that the current sensor 101 includes a voltage detection unit 102 instead of a voltage detection unit 22, a switching unit 103 is added, and the current sensor 101 includes a control unit 104 instead of a control unit 12, etc.

[0106] The voltage detection unit 102 differs from the voltage detection unit 22 in that the third voltage detection unit 11 is omitted. Similar to the switching unit 92 in the third embodiment, the switching unit 103 is configured, for example, by a multiplexer, and switches the connection state between the terminals of the shunt resistor 4, the correction resistors 5 and 6, and the input terminal of the voltage detection unit 102. The operation of the switching unit 103 is controlled by the control unit 104.

[0107] In the connection state of the switching unit 103, each of the first voltage detection unit 9 and the second voltage detection unit 10 is switchable to detect the terminal voltage of each of the shunt resistor 4, the correction resistor 5, and the correction resistor 6. The connection state of the switching unit 103 can be switched, for example, to... Figure 11 The first connection state shown causes the first voltage detection unit 9 to detect the terminal voltage of the shunt resistor 4, and the second voltage detection unit 10 to detect the correction resistor 5. Furthermore, the connection state of the switching unit 103 can be switched, for example, to... Figure 12 The second connection state shown in the figure enables the first voltage detection unit 9 to detect the terminal voltage of the correction resistor 5, and the second voltage detection unit 10 to detect the correction resistor 6.

[0108] Furthermore, the connection state of the switching unit 103 can be switched, for example, so that the first voltage detection unit 9 detects the terminal voltage of the correction resistor 5, and the second voltage detection unit 10 detects the terminal voltage of the shunt resistor 4. Furthermore, the connection state of the switching unit 103 can be switched, for example, so that the first voltage detection unit 9 detects the terminal voltage of the correction resistor 6, and the second voltage detection unit 10 detects the terminal voltage of the correction resistor 5.

[0109] Furthermore, the connection state of the switching unit 103 can be switched so that both the first voltage detection unit 9 and the second voltage detection unit 10 detect, for example, the terminal voltage of the shunt resistor 4. Furthermore, the connection state of the switching unit 103 can be switched so that, for example, both the first voltage detection unit 9 and the second voltage detection unit 10 detect the terminal voltage of the correction resistor 5. Furthermore, the connection state of the switching unit 103 can be switched so that, for example, both the first voltage detection unit 9 and the second voltage detection unit 10 detect the terminal voltage of the correction resistor 6.

[0110] The control unit 104 differs from the control unit 12 in that it adds a functional block for a gain error reduction unit 105. In the above configuration, the resistance value correction circuit 106 for correcting the detection resistor value is configured with correction resistors 5 and 6, a signal application unit 15, a voltage detection unit 102, a correction unit 24, a switching unit 103, and a gain error reduction unit 105. Similar to the gain error reduction unit 94 in the fourth embodiment, the gain error reduction unit 105 includes a first A / D converter 16 of the first voltage detection unit 9 and a second A / D converter 18 of the second voltage detection unit 10, thereby reducing the gain error of each ADC.

[0111] Then, the gain error reduction unit 105 can reduce the gain error of each ADC by switching the connection state of the switching unit 103 as follows: That is, in the gain error reduction unit 105, for example, the switching state of the switching unit 103 is switched such that both the first voltage detection unit 9 and the second voltage detection unit 10 detect the terminal voltage of the shunt resistor 4, the correction resistor 5, or the correction resistor 6. As a result, the gain error reduction unit 105 can reduce the relative gain error of each ADC based on the detected value of the terminal voltage of the shunt resistor 4, the correction resistor 5, or the correction resistor 6 detected by each of the first voltage detection unit 9 and the second voltage detection unit 10. In this case, the gain error reduction unit 105 can perform correction, for example, to make the ADC gains the same.

[0112] Furthermore, during the first time period, the gain error reduction unit 105 switches the connection state of the switching unit 103 to [condition] during the calibration process. Figure 11The first connection state is shown in the diagram. Then, during the second time period, the gain error reduction unit 105 switches the connection state of the switching unit 103 to the following state during correction: Figure 12 The second connection state is shown. In the first connection state, the first voltage detection unit 9 can detect the terminal voltage of the shunt resistor 4, and the second voltage detection unit 10 can detect the terminal voltage of the correction resistor 5. In the second connection state, the first voltage detection unit 9 can detect the terminal voltage of the correction resistor 6, and the second voltage detection unit 10 can detect the terminal voltage of the correction resistor 5.

[0113] In this case, the gain errors of the first A / D converter 16 and the second A / D converter 18 are reduced as follows. That is, assuming the gain error of the first A / D converter 16 is defined as G1 and the gain error of the second A / D converter 18 is defined as G2, then the value representing the ratio of the resistance values ​​of the shunt resistor 4 and the correction resistor 5 obtained by the correction unit 24 in the first time period is defined as "(G1 × R) / (G2 × R1)". Furthermore, the value representing the ratio of each resistance value of the correction resistor 5 and the correction resistor 6 obtained by the correction unit 24 in the second time period is defined as "(G2 × R1) / (G1 × R2)". The value representing the ratio of the resistance values ​​of the shunt resistor 4 and the correction resistor 6 obtained by multiplying these values ​​is defined as "R / R2", and the gain errors G1 and G2 of the ADC are eliminated. As described above, in the above configuration, the gain error reduction unit 105 can eliminate the gain error of each ADC by averaging.

[0114] As described above, the resistance value correction circuit 106 of the current sensor 101 in this embodiment includes a gain error reduction unit 105 for reducing the gain error of each of the first A / D converter 16 of the first voltage detection unit 9 and the second A / D converter 18 of the second voltage detection unit 10. With this configuration, the gain errors of the first A / D converter 16 and the second A / D converter 18 can be reduced to a minimum, for example, 0.1%. Therefore, according to this embodiment, the detection accuracy of the voltage detection unit 102 for the terminal voltages of the shunt resistor 4 and the correction resistors 5 and 6 is further improved, resulting in further improvement in the correction accuracy of the detected resistance value.

[0115] In this configuration, the voltage detection unit 102 is arranged such that, in each of the above embodiments, the third voltage detection unit 11 is omitted from the voltage detection unit 22. Here, the current sensor 101 includes a switching unit 103 for switching the connection state between each terminal of the shunt resistor 4, the correction resistors 5 and 6, and each input terminal of the voltage detection unit 102. By switching the connection state of the switching unit 103, the two voltage detection units detect the terminal voltages of the shunt resistor 4 and the correction resistor 5 in a first time period, and the terminal voltages of the correction resistors 5 and 6 in a second time period. These two voltage detection units are the first voltage detection unit 9 and the second voltage detection unit 10. Therefore, according to this embodiment, the same operations as in each of the above embodiments can be performed, while keeping the circuit size small by omitting the third voltage detection unit 11.

[0116] (Fifth Embodiment) The following will refer to Figure 13 The fifth embodiment is described.

[0117] like Figure 13 As shown in the figure, the current sensor 111 in this embodiment and Figure 1 The difference in the first embodiment of the current sensor 1 shown is the addition of a temperature sensor 112, and the current sensor 111 has a control unit 113 that replaces the control unit 12. The temperature sensor 112 is provided near the shunt resistor 4 and outputs a temperature detection signal based on the temperature of the shunt resistor 4.

[0118] The control unit 113 differs from the control unit 12 in that it adds functional blocks such as a first temperature detection unit 114 and a current value correction unit 115. In the above configuration, the resistance value correction circuit 116 for correcting the detected resistance value is configured with correction resistors 5 and 6, a signal application unit 15, a voltage detection unit 22, a correction unit 24, the first temperature detection unit 114, and the current value correction unit 115. The first temperature detection unit 114 detects the temperature of the shunt resistor 4 based on the temperature detection signal output from the temperature sensor 112.

[0119] The current value correction unit 115 cooperates with the correction unit 24 to perform the following operation: The current value correction unit 115 corrects the detected resistance value based on the calculated resistance value and the temperature detected value obtained by the first temperature detection unit 114. Specifically, after determining the temperature of the shunt resistor 4 based on the temperature detected value of the first temperature detection unit 114, the current value correction unit 115 corrects the detected resistance value based on the calculated resistance value, and finally, corrects the detected value of the target current. As described above, the current value correction unit 115 corrects the detected value of the target current based on the temperature detected value of the first temperature detection unit 114.

[0120] As described above, the resistance correction circuit 116 of the current sensor 111 in this embodiment includes a current correction unit 115, which corrects the detected resistance value. Finally, based on the temperature detection value of the first temperature detection unit 114, together with the first temperature detection unit 114 that detects the temperature of the shunt resistor 4, the detected value of the target current is corrected. With this configuration, taking into account the temperature characteristics of the resistance value of the shunt resistor 4, the detected resistance value can be corrected with high accuracy, and the detected target current can also be corrected with high accuracy.

[0121] (Sixth embodiment) The following will refer to Figure 14 The sixth embodiment is described.

[0122] like Figure 14 As shown in the figure, the current sensor 121 in this embodiment and Figure 13 The difference in the fifth embodiment of the current sensor 111 shown is the addition of a temperature sensor 122, and the current sensor 121 has a control unit 123 that replaces the control unit 113. The temperature sensor 122 is provided near the calibration resistor 5 and outputs a temperature detection signal corresponding to the temperature of the calibration resistor 5.

[0123] The control unit 123 differs from the control unit 113 in that it adds a functional block for a second temperature detection unit 124 and provides a current value correction unit 125 instead of the current value correction unit 115. In the above configuration, the resistance value correction circuit 126 for correcting the detection resistance value is configured with correction resistors 5 and 6, a signal application unit 15, a voltage detection unit 22, a correction unit 24, a first temperature detection unit 114, a second temperature detection unit 124, and a current value correction unit 125. The second temperature detection unit 124 detects the temperature of the correction resistor 5 based on the temperature detection signal output from the temperature sensor 122.

[0124] In addition to operating in the same way as the current value correction unit 115, the current value correction unit 125 also cooperates with the correction unit 24 to perform the following operations: That is, the current value correction unit 125 corrects the correction resistor value based on the temperature detection value of the second temperature detection unit 124, and uses the corrected correction resistor value to calculate the calculated resistance value. In other words, the current value correction unit 125 corrects the calculated resistance value based on the temperature detection value of the second temperature detection unit 124.

[0125] Then, the current value correction unit 125 corrects the resistance value based on the calculated resistance value after correction and the temperature detection value of the first temperature detection unit 114, and finally corrects the detected value of the target current. In this way, the current value correction unit 125 corrects the detected value of the target current based on the temperature detection values ​​of the first temperature detection unit 114 and the second temperature detection unit 124.

[0126] As described above, the resistance correction circuit 126 of the current sensor 121 in this embodiment includes a first temperature detection unit 114 for detecting the temperature of the shunt resistor 4, a second temperature detection unit 124 for detecting the temperature of the correction resistor 5, and a current correction unit 125. The current correction unit 125 corrects the detection resistance value based on the temperature detection values ​​of the first temperature detection unit 114 and the second temperature detection unit 124, and ultimately corrects the detection value of the target current. With this configuration, not only the temperature characteristics of the resistance value of the shunt resistor 4 are considered, but also the temperature characteristics of the resistance value of the correction resistor 5 are considered, and the detection resistance value is corrected with high accuracy. Finally, the target current is detected with high accuracy.

[0127] (Seventh Embodiment) The following will refer to Figure 15 The seventh embodiment is described.

[0128] like Figure 15 As shown in the figure, the current sensor 131 in this embodiment and Figure 14 The difference in the sixth embodiment of the current sensor 121 shown is the addition of a temperature sensor 132, and the current sensor 121 has a control unit 133 instead of a control unit 123. The temperature sensor 132 is provided near the calibration resistor 6 and outputs a temperature detection signal corresponding to the temperature of the calibration resistor 6.

[0129] The control unit 133 differs from the control unit 123 in that a second temperature detection unit 134 is arranged in place of the second temperature detection unit 124, and a current value correction unit 135 is arranged in place of the current value correction unit 125. In the above configuration, the resistance value correction circuit 136 for correcting the detection resistance value is configured with correction resistors 5 and 6, a signal application unit 15, a voltage detection unit 22, a correction unit 24, a first temperature detection unit 114, a second temperature detection unit 134, and a current value correction unit 135. The function of the second temperature detection unit 134 is, in addition to having the same function as the second temperature detection unit 124, to detect the temperature of the correction resistor 6 based on the temperature detection signal output from the temperature sensor 132.

[0130] The current value correction unit 135 cooperates with the correction unit 24 to perform the following operation: The current value correction unit 135 corrects each correction resistor value based on each temperature detection value of the second temperature detection unit 134, and uses each corrected correction resistor value to calculate a calculated resistance value. In other words, the current value correction unit 135 corrects the calculated resistance value based on each temperature detection value of the second temperature detection unit 134.

[0131] Then, the current value correction unit 135 corrects the resistance value based on the corrected calculated resistance value and the temperature detection value of the first temperature detection unit 114, and finally corrects the detected value of the target current. In this way, the current value correction unit 135 corrects the detected value of the target current based on the temperature detection value of the first temperature detection unit 114 and each temperature detection value of the second temperature detection unit 134.

[0132] As described above, the resistance correction circuit 136 of the current sensor 131 in this embodiment includes a first temperature detection unit 114 for detecting the temperature of the shunt resistor 4, a second temperature detection unit 134 for detecting the temperature of the correction resistors 5 and 6, and a current correction unit 135. The current correction unit 135 corrects the detection resistance value based on the temperature detection values ​​of the first and second temperature detection units 114 and ultimately corrects the detection value of the target current. With this configuration, not only the temperature characteristics of the resistance value of the shunt resistor 4 are considered, but also the temperature characteristics of each resistance value of the correction resistors 5 and 6 are considered, and the detection resistance value is corrected with high accuracy. Finally, the target current is detected with high accuracy.

[0133] (Eighth Embodiment) The following will refer to Figure 16 and Figure 17 The eighth embodiment of this disclosure is described.

[0134] In the specific configuration examples of the signal application units 15 and 74 described in each of the above embodiments, the first signal application units 7 and 72 and the second signal application units 8 and 73 each have a dedicated amplifier or buffer. Alternatively, they may share the same amplifier or buffer.

[0135] For example, such as Figure 16 As shown, the first signal application unit 7 and the second signal application unit 8 can share the same amplifier. That is, Figure 16 The first signal application unit 7c in the signal application unit 15c shown is... Figure 2 The difference in the first signal application unit 7a shown is the addition of switches S1 and S2. In this case, the inverting input terminal of the OP amplifier 34 is connected to the drain of the transistor 31 via switch S1, and its output terminal is connected to the gate of the transistor 31 via switch S2.

[0136] The second signal application unit 8c of the signal application unit 15c and Figure 2 The difference in the second signal application unit 8a shown is that the signal generation unit 37 and the OP amplifier 38 are omitted, and switches S3 and S4 are added. In this case, the signal generation unit 33 and the OP amplifier 34 are used not only in the first signal application unit 7c but also in the second signal application unit 8c. Therefore, the inverting input terminal of the OP amplifier 34 is connected to the drain of the transistor 35 via switch S3, and its output terminal is connected to the gate of the transistor 35 via switch S4.

[0137] In the above configuration, switches S1 and S2, as well as switches S3 and S4, are switched on and off in a complementary manner. Specifically, switches S1 and S2 are switched on during the first correction time period, and switches S3 and S4 are switched on during the second correction time period. As a result, the first signal application unit 7c can operate using the OP amplifier 34 during the first time period, and the second signal application unit 8c can operate using the OP amplifier 34 during the second time period.

[0138] For example, such as Figure 17 As shown, the first signal application unit 7 and the second signal application unit 8 can share the same buffer. That is, Figure 17 The first signal application unit 7d in the signal application unit 15d shown is... Figure 3 The difference in the first signal application unit 7b shown is the addition of a switch S5. In this case, the output terminal of the buffer is connected to the gate of the transistor 31 via the switch S5.

[0139] The second signal application unit 8d in signal application unit 15d and Figure 3The difference in the second signal application unit 8b shown is that the signal generation unit 37 and the buffer 42 are omitted, and a switch S6 is added, etc. In this case, the signal generation unit 33 and the buffer 41 are used not only in the first signal application unit 7d but also in the second signal application unit 8d. Therefore, the output terminal of the buffer 41 is connected to the gate of the transistor 35 via the switch S6.

[0140] In the above configuration, switches S5 and S6 are turned on and off in a complementary manner. Specifically, switch S5 is turned on during the first correction time period, and switch S6 is turned on during the second correction time period. As a result, the first signal application unit 7d can operate using buffer 41 during the first time period, and the second signal application unit 8d can operate using buffer 41 during the second time period.

[0141] As described above, the first signal application units 7c and 7d and the second signal application units 8c and 8d of this embodiment are configured to share the same amplifier or buffer. This configuration reduces the circuit size by eliminating the need for a separate amplifier or buffer compared to a configuration that provides separate dedicated amplifiers or buffers for the first signal application unit 7 and the second signal application unit 8.

[0142] (Other embodiments) This disclosure is not limited to the embodiments described above and shown in the accompanying drawings, but can be freely modified, combined or extended without departing from the spirit of this disclosure.

[0143] The numerical values ​​shown in the above embodiments are examples and are not limited to those examples.

[0144] The resistance correction circuit 25, etc., has a configuration with two correction resistors 5 and 6, or the number of correction resistors can be multiple, or even three or more correction resistors can be provided.

[0145] The specific configuration of signal application units 15 and 74 is not limited to the configuration described in each of the above embodiments. It can be any configuration as long as the feature applies an AC signal to all or part of the series circuit of shunt resistor 4 and multiple correction resistors 5 and 6.

[0146] The specific configuration of the first synchronization detection circuit 17 is not limited to the configurations described in each of the above embodiments; it can be any configuration, as long as the signal at the terminal of the input shunt resistor 4 is input and synchronization detection is performed at the same frequency as the AC signal to extract and output the signal. The specific configuration of the second synchronization detection circuit 19 enables the input of the signal at the terminal of the correction resistor 5 and enables synchronization detection to be performed at the same frequency as the AC signal to extract and output the signal. The specific configuration of the third synchronization detection circuit 21 enables the input of the signal at the terminal of the correction resistor 6 and enables synchronization detection to be performed at the same frequency as the AC signal to extract and output the signal.

[0147] Although this disclosure has been described with reference to embodiments, it is to be understood that this disclosure is not limited to such embodiments or structures. This disclosure incorporates various modifications and variations within the scope of its equivalents. Furthermore, various combinations and forms, including other combinations and forms with only one element or more or fewer such elements, are also within the spirit and scope of this disclosure.

[0148] 1, 71, 91, 101, 111, 121, and 131 represent current sensors; 4 represents a shunt resistor; 5 and 6 represent calibration resistors; 7, 7a, 7b, 7c, 7d, 72, 72a, and 72b represent first signal application units; 8, 8a, 8b, 8c, 8d, 73, 73a, and 73b represent second signal application units; 9 represents a first voltage detection unit; 10 represents a second voltage detection unit; 11 represents a third voltage detection unit; 15, 15a, 15b, 15c, 15d, 74, 74a, and 74b represent signal application units; and 16 represents a first A / D converter. The circuit diagram is as follows: 17 represents the first synchronous detection circuit, 18 represents the second A / D converter, 19 represents the second synchronous detection circuit, 20 represents the third A / D converter, 21 represents the third synchronous detection circuit, 22 and 102 represent voltage detection units, 24 represents correction units, 25, 75, 95, 106, 116, 126 and 136 represent resistance value correction circuits, 92 and 103 represent switching units, 94 and 105 represent gain error reduction units, 114 represents the first temperature detection unit, 115, 125 and 135 represent current value correction units, and 124 and 134 represent the second temperature detection unit.

[0149] Although this disclosure has been described with reference to embodiments thereof, it is to be understood that this disclosure is not limited to these embodiments and constructions. This disclosure is intended to cover various modifications and equivalent arrangements. Furthermore, although various combinations and configurations are possible, other combinations and configurations including more, fewer, or only a single element are also within the spirit and scope of this disclosure.

Claims

1. A current sensor for detecting the target current based on the terminal voltage of a shunt resistor (4) arranged in series in the path through which the target current flows and a current-detecting resistance value corresponding to the resistance value of the shunt resistor, the current sensor comprising: The resistor value correction circuit (25, 75, 95, 106, 116, 126, 136) used to correct the resistor value for current detection, wherein: The resistance correction circuit includes: Multiple correction resistors (5, 6) are connected in series with the shunt resistor in a different path than the path through which the target current flows, and have a higher resistance accuracy than the shunt resistor. Signal application units (15, 15a, 15b, 15c, 15d, 74, 74a, 74b) apply AC signals to all or part of the series circuit of the shunt resistor and the plurality of correction resistors. A voltage detection unit (22, 102) detects the terminal voltage of the shunt resistor and the terminal voltage of a portion of the correction resistor during a first time period when the AC signal is applied to the portion of the series circuit including the shunt resistor, and detects the terminal voltage of the entire correction resistor during a second time period when the AC signal is applied to the entire series circuit; and The correction unit (24) calculates the resistance value of the shunt resistor based on the detection values ​​of each terminal voltage detected by the voltage detection unit in the first time period and the detection values ​​of each terminal voltage detected by the voltage detection unit in the second time period, and corrects the current detection resistance value based on the calculated resistance value, wherein the calculated resistance value is the calculated resistance value of the shunt resistor; and As the plurality of correction resistors are positioned further away from the shunt resistor in the series circuit, the resistance values ​​and resistance accuracy of the plurality of correction resistors are higher.

2. The current sensor according to claim 1, wherein: The voltage detection unit includes multiple A / D converters (16, 18, 20), which perform A / D conversion operations to detect the terminal voltage of the shunt resistor and the terminal voltage of the correction resistor; and The resistance correction circuit further includes: Switching units (92, 103) switch connection states to connect each of the plurality of A / D converters to each of the plurality of correction resistors and the shunt resistors, respectively; and Gain error reduction unit (94, 105), which reduces the gain error of the plurality of A / D converters by switching the connection state of the switching unit.

3. The current sensor according to claim 1, wherein: The resistor value correction circuit (116, 126, 136) also includes: A first temperature detection unit (114) detects the temperature of the shunt resistor; and A current value correction unit (115, 125, 135) corrects the detection value of the target current based on the temperature detection value of the first temperature detection unit.

4. The current sensor according to claim 3, wherein: The resistance correction circuit (126, 136) further includes a second temperature detection unit (124, 134), which detects the temperature of at least one of the correction resistors; and The current value correction unit (125, 135) corrects the detection value of the target current based on the temperature detection value of the first temperature detection unit and the temperature detection value of the second temperature detection unit.

5. The current sensor according to claim 1, wherein: The signal application units (15c, 15d) include: First signal application units (7c, 7d) apply the AC signal to the portion of the series circuit including the shunt resistor; and The second signal application unit (8c, 8d) applies the AC signal to the entire series circuit; and The first signal application unit and the second signal application unit share the same amplifier (34) or the same buffer (41).

6. The current sensor according to claim 1, wherein: The signal applying unit applies the AC signal having a pulse wave or a sine wave to the series circuit.

7. The current sensor according to any one of claims 1 to 6, wherein: The voltage detection unit is configured to: Input signals to the terminals of the shunt resistor; Synchronization detection is performed at the same frequency as the AC signal to extract the signal; The terminal voltage of the shunt resistor is detected based on the extracted signal; Input the signal to the terminal of each correction resistor; Synchronization detection is performed at the same frequency as the AC signal to extract and output the signal; as well as The terminal voltage of each correction resistor is detected based on the extracted signal.

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