Shunt type current sensor

Abstract

To provide a shunt type current sensor designed to sense shunt resistance values at low cost in a current sensor that performs redundancy detection.SOLUTION: A signal processing circuit 14 operates in one of a load current redundancy detection mode and a shunt resistance measurement mode. In the load current redundancy detection mode, the voltage applied to a shunt resistor 12 is measured using voltage measurement circuits 13, 13a while an AC exciting current IE is not flowing from a current exciting circuit 52 to a reference resistor 12a and a shunt resistor 12, and a load current IL is flowing from a load 80 to the shunt resistor 12, and the redundancy of the load current IL flowing to the load 80 is detected. In the shunt resistance measurement mode, a resistance value RS of the shunt resistor 12 is detected on the basis of the voltage of the reference resistor 12a and the voltage of the shunt resistor 12 measured by the voltage measurement circuits 13, 13a, respectively when the AC exciting current IL is flowed from the current exciting circuit 52 to the reference resistor 12a and the shunt resistor 12.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a shunt-type current sensor. [Background technology]

[0002] Electric vehicles such as electric vehicles (EV) and hybrid electric vehicles (HEV) are equipped with batteries. In order to estimate the remaining capacity of this type of battery, a circuit is required to measure the current flowing through the battery. A shunt current sensor is provided to measure the current flowing through the battery. The shunt current sensor measures the current by connecting a shunt resistor in series to the battery and measuring the voltage across the shunt resistor. The resistance value of the shunt resistor changes due to deterioration over time. Therefore, the current can be measured with high accuracy by accurately determining the resistance value of the shunt resistor. An example of a shunt current sensor is disclosed in Patent Document 1. According to the technology described in Patent Document 1, a highly accurate reference excitation current is applied to a shunt resistor, the voltage across the shunt resistor is measured, the shunt resistance value is determined from the applied excitation current and the measured voltage across the shunt, and the shunt resistance value is corrected to improve accuracy. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Pat. No. 1,052,7651 Summary of the Invention [Problem to be solved by the invention]

[0004] Typically, two or more voltage measurement circuits are provided to measure the voltage across the shunt resistor, enhancing functional safety. The two or more voltage measurement circuits are configured to be able to measure the voltage across the shunt resistor, respectively, so that the load current can be detected redundantly. However, when applying the technology described in Patent Document 1, a reference current source that generates a high-precision reference current is required. A reference current source with small temperature characteristics and degradation is not preferable because it requires a large reference diode or transistor and a large correction circuit, which increases the cost. In addition, the power supply power for passing the excitation current tends to be large, which is also undesirable. In addition, the power supply power for passing the excitation current tends to be large, which is also undesirable.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and its purpose is to provide a shunt-type current sensor that is capable of sensing the current flowing through a load with high accuracy by using two or more voltage measurement circuits for functional safety. [Means for solving the problem]

[0006] The invention of claim 1 is directed to a shunt-type current sensor for redundantly detecting a current flowing through a load. A reference resistor is connected in series with a shunt resistor. A current excitation circuit generates an AC excitation current and passes the AC excitation current through the shunt resistor and the reference resistor. Two or more voltage measurement circuits enable the voltage across the shunt resistor to be measured. A signal processing circuit processes a signal based on the voltage measured by the voltage measurement circuit.

[0007] The signal processing circuit operates in either a load current redundant detection mode or a shunt resistance measurement mode. In the load current redundant detection mode, the load current flowing through the load is redundantly detected by measuring the voltage across the shunt resistance using two or more voltage measurement circuits in a state in which no AC excitation current from the current excitation circuit flows through the reference resistance and the shunt resistance and a load current flows from the load to the shunt resistance.

[0008] In the shunt resistance measurement mode, the resistance value of the shunt resistor is detected based on the voltage of the reference resistor and the voltage of the shunt resistor measured by two or more voltage measurement circuits when an AC excitation current from a current excitation circuit is applied to the reference resistor and the shunt resistor, respectively. This makes it possible to sense the current flowing through the load with high accuracy using two or more voltage measurement circuits for functional safety. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is an electrical configuration diagram illustrating a shunt-type current sensor according to a first embodiment; [Diagram 2] FIG. 1 is an electrical block diagram showing a battery monitoring system according to a first embodiment of the present invention; [Diagram 3] Specific example of the signal processing circuit in the first embodiment [Figure 4] FIG. 13 is an electrical configuration diagram illustrating a shunt-type current sensor according to a second embodiment. [Diagram 5] Configuration example 1 of the shunt-type current sensor according to the second embodiment [Figure 6] Configuration example 2 of the shunt-type current sensor in the second embodiment [Figure 7] Time chart 1 explaining the operation in the second embodiment [Figure 8] Time chart 2 explaining the operation in the second embodiment [Figure 9] FIG. 13 is an electrical configuration diagram illustrating a shunt-type current sensor according to a third embodiment. [Figure 10] FIG. 13 is a perspective view showing a schematic appearance of a shunt resistor according to a fourth embodiment; [Figure 11] FIG. 13 is a plan view illustrating a schematic appearance of a shunt resistor according to a fourth embodiment; [Figure 12] FIG. 13 is an electrical configuration diagram illustrating a shunt-type current sensor according to a fifth embodiment. [Figure 13] Configuration example of a switching power supply circuit according to the fifth embodiment [Figure 14] FIG. 13 is a timing chart showing waveforms of various parts in the fifth embodiment; [Figure 15] FIG. 15 is an enlarged view of a portion A in FIG. 14 according to the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, several embodiments of the shunt-type current sensor will be described. In each embodiment described below, components that perform the same or similar operations are denoted by the same or similar reference numerals, and descriptions thereof will be omitted as necessary.

[0011] (First embodiment) A first embodiment will be described with reference to Fig. 1 to Fig. 3. Fig. 2 shows a schematic diagram of a battery monitoring system 100. As shown in Fig. 2, the battery monitoring system 100 is mainly composed of an integrated circuit 55 for battery monitoring, a temperature sensor 56, an MCU 57, and a shunt type current sensor 1. The shunt type current sensor 1 includes an analog front end (AFE) 50a, a DSP 51, a current excitation circuit 52, and an analog front end (AFE) 53 for temperature measurement.

[0012] DSP is an abbreviation for Digital Signal Processor. MCU is an abbreviation for Micro Controller Unit. The MCU 57 includes a processor and a memory, and operates based on a program prestored in the memory. The memory is configured as a non-transient tangible recording medium.

[0013] The current excitation circuit 52 generates an AC excitation current I E is applied to the shunt resistor 12. The analog front end 50a is connected to the terminals of the shunt resistor 12, measures the voltage across the shunt resistor 12, and performs analog processing. The shunt resistor 12 is connected in series to a battery 58. The shunt resistor 12 detects a load current I L It is provided to measure with high accuracy.

[0014] The battery 58 is a main battery and / or an auxiliary battery, which is a combination of battery cells in series or series-parallel. The battery 58 is provided to drive a load 80, which is a main motor or a DC-DC converter of a vehicle such as an electric vehicle or a hybrid vehicle, and / or to supply power to a vehicle electronic control device provided in the vehicle.

[0015] A relay 59 and a load 80 are connected in series to the battery 58 and the shunt resistor 12. The battery 58, the relay 59, and the load 80 constitute a vehicle electrical system 90. When the ignition switch is turned on by a user to start the vehicle, the relay 59 is turned on. When the relay 59 is turned on, the load 80, the battery 58, and the shunt resistor 12 are connected. As a result, a load current I L is energized.

[0016] The shunt resistor 12 is on the order of several tens of micro-ohms and supplies a load current I L When a current is applied, a current of the order of several thousand amperes flows through the shunt resistor 12. The shunt resistor 12 deteriorates over time and its resistance value R S Therefore, the shunt current sensor 1 changes the resistance R S By accurately calculating the load current I L can be measured with high accuracy.

[0017] A temperature sensor 54 is disposed near the shunt resistor 12. The temperature sensor 54 is configured by a thermistor, and is connected to an analog front-end 53 for temperature measurement. The analog front-end 53 for temperature measurement receives a temperature measurement signal T S When the input is input, the waveform is shaped, noise is removed, and the temperature measurement signal T S Output.

[0018] The DSP51 outputs the temperature measurement signal T S The load current I flows through the shunt resistor 12 according to L , the resistance value R of shunt resistor 12 Sand outputs the corrected signal to the MCU 57. The DSP 51 functions as the signal processing circuit 14 shown in FIG.

[0019] On the other hand, an integrated circuit 55 for monitoring the battery cells is connected to the battery 58. The integrated circuit 55 monitors the voltage V C The integrated circuit 55 is provided to monitor the battery 58 and measure the remaining battery capacity (SOC). A temperature sensor 56 is disposed near the battery 58 and is connected to the integrated circuit 55. The integrated circuit 55 receives a temperature measurement signal T CELL When you input CELL Depending on the battery cell voltage V C The integrated circuit 55 corrects the temperature measurement signal T CELL The MCU57 sends the temperature measurement signal T CELL Depending on the battery cell voltage V C may be corrected.

[0020] The MCU57 receives the load current I L , the resistance value R of shunt resistor 12 S Therefore, the MCU 57 receives the resistance value R S A load current I flows through the battery cells constituting the battery 58 according to L This information can be measured accurately.

[0021] The components of the shunt type current sensor 1 will be described below with reference to Fig. 1 and Fig. 3. The shunt resistor 12 is connected to a vehicle electrical system 90. The shunt type current sensor 1 shown in Fig. 1 detects a load current I L The path connecting the shunt resistor 12 and the voltage measurement circuits 13, 13a is composed of two pairs of differential paths, each of which is connected through a different path. Note that a specific example of the connection form of the shunt resistor 12 will be described in the fourth embodiment described later.

[0022] The reference resistor 12a is connected in series to the shunt resistor 12. The impedance of the reference resistor 12a is highly accurate, about 10 Ω, while the impedance of the shunt resistor 12 is several tens of micro Ω, which is about six orders of magnitude smaller. As will be described later, the resistance value R of the shunt resistor 12 is calculated by taking the ratio of the shunt resistor 12 and the reference resistor 12a. S Therefore, it is easier to measure by selecting resistance values ​​of approximately the same value. However, the commonly available high-precision, low-degradation standard resistor 12a has a resistance value of 10 Ω or more, so the resistance value R REF1 , R S are composed of resistances that differ greatly from each other.

[0023] The current excitation circuit 52 includes the AC excitation circuit 16 shown in FIG. E This generates an AC excitation current I E The AC excitation circuit 16 of the current excitation circuit 52 receives the modulating signal S M It is preferable to configure the power supply circuit with a switching power supply circuit to which the modulation signal S M is a relatively low frequency f M The signal is, for example, a rectangular wave signal of about several hundred Hz. Although not shown here, the switching power supply circuit includes an inductor, a capacitor, and a switching element, and the modulation signal S given from the control circuit 10 is M By turning the switching element on and off, the AC excitation current I E It is recommended to generate the following.

[0024] The first voltage measurement circuit 13 and the second voltage measurement circuit 13a are configured to be able to measure the voltage applied to the shunt resistor 12. A multiplexer 19 is configured between the voltage measurement circuits 13, 13a and the shunt resistor 12 and between the voltage measurement circuits 13, 13a and the shunt resistor 12 and the reference resistor 12a.

[0025] In response to a control signal from the control circuit 10, the multiplexer 19 connects the shunt resistor 12 to either the voltage measuring circuit 13 or 13a, or connects the reference resistor 12a to either the voltage measuring circuit 13 or 13a.

[0026] This allows the first voltage measurement circuit 13 and the second voltage measurement circuit 13a to measure the voltage across the reference resistor 12a and the voltage across the shunt resistor 12, respectively. The first voltage measurement circuit 13 includes an AD converter 18, which converts the input voltage into a digital value and outputs it to the signal processing circuit 14. The second voltage measurement circuit 13a also includes an AD converter 18a, which converts the voltage into a digital value and outputs it to the signal processing circuit 14.

[0027] The signal processing circuit 14 is a DSP 51 (see FIG. 2) equipped with a volatile memory and a non-volatile memory. The signal processing circuit 14 processes signals based on the measurement results of the voltage measurement circuits 13 and 13a. The signal processing circuit 14 operates in either a load current redundant detection mode or a shunt resistance measurement mode.

[0028] <Load current redundancy detection mode> In the load current redundant detection mode, the signal processing circuit 14 receives the AC excitation current I from the current excitation circuit 52. E When the load current I flows through the load 80, the voltage across the shunt resistor 12 is measured by the two voltage measuring circuits 13 and 13a. L Detect redundantly.

[0029] Specifically, the control circuit 10 switches the input and output of the multiplexer 19, thereby measuring the voltage across the shunt resistor 12 with the first voltage measurement circuit 13 and measuring the voltage across the shunt resistor 12 with the second voltage measurement circuit 13a. This allows the first voltage measurement circuit 13 and the second voltage measurement circuit 13a to simultaneously detect the voltage across the shunt resistor 12. As a result, the load current I L In addition, even if one of the voltage measurement circuits 13 fails, the other voltage measurement circuit 13a can measure the voltage and detect the load current I L The measurement function can be compensated for.

[0030] <Shunt resistance measurement mode> In the shunt resistance measurement mode, the current excitation circuit 52 generates an AC excitation current I E In this state, the signal processing circuit 14 calculates the resistance value R of the shunt resistor 12 based on the voltage of the reference resistor 12a and the voltage of the shunt resistor 12 measured by the first voltage measurement circuit 13 and the second voltage measurement circuit 13a, respectively. S Detect.

[0031] In the shunt resistance measurement mode, the control circuit 10 switches the output of the multiplexer 19 to the first voltage measurement circuit 13 side to measure the load current I L The resistance value R of the shunt resistor 12 is measured by a first voltage measuring circuit 13 for measuring S In addition, the control circuit 10 switches the output of the multiplexer 19 to the second voltage measurement circuit 13a, and the resistance value R of the shunt resistor 12 is measured by the redundant second voltage measurement circuit 13a provided for functional safety. S Therefore, the two voltage measurement circuits 13, 13a provided for functional safety can be effectively utilized, and there is no need to add other voltage measurement circuits. As a result, the device can be constructed at low cost.

[0032] In shunt resistance measurement mode, the AC excitation current I E and the load current I L flows through the shunt resistor 12. At this time, the voltage across the shunt resistor 12 is R S × (AC excitation current I E +Load current I L The reference AC excitation current I E The information is recorded in advance in the memory.

[0033] The signal processing circuit 14 includes a reference resistor R REF Using the AC excitation current I E Since the reference AC excitation current I E Based on subtracting the load current I L As a result, the load current IL In addition, the signal processing circuit 14 can measure the load current I L Therefore, the load current I L Abnormalities can be constantly monitored.

[0034] A specific example of the signal processing circuit 14 will be described with reference to Fig. 3. As shown in Fig. 3, the signal processing circuit 14 includes an AC measurement path 14b including a synchronous detection circuit 14a that synchronously detects the measurement results of the first voltage measurement circuit 13 and the second voltage measurement circuit 13a, and a DC measurement path 14c that measures a DC component from the measurement results of the first voltage measurement circuit 13 and the second voltage measurement circuit 13a.

[0035] <About AC measurement path 14b> The signal processing circuit 14 processes the signal based on the measurement result of the first voltage measurement circuit 13 in the AC measurement path 14b and calculates the resistance value R S The AC measurement path 14b is provided with a synchronous detection circuit 14a, a divider 43a, and a multiplier 44a. In the shunt resistance measurement mode, the signal processing circuit 14 synchronously detects the measurement results of the first voltage measurement circuit 13 and the second voltage measurement circuit 13a using the synchronous detection circuit 14a of the AC measurement path 14b to obtain the AC excitation current I E Detect the AC component of

[0036] For example, the synchronous detection circuit 14a performs signal processing in synchronization with the output frequency of the digital output of the AD converter 18 of the first voltage measurement circuit 13, and the modulation signal S M AC excitation current I E This allows the synchronous detection circuit 14a to detect the AC excitation current I E This allows the voltage across the shunt resistor 12 to be measured with high accuracy.

[0037] The synchronous detection circuit 14a includes mixers 21i, 21q, 22i, and 22q, filters 31i, 31q, 32i, and 32q, and absolute value calculators 41 and 42. The signal processing circuit 14 processes signals in synchronization with the output frequencies of the digital outputs of the AD converter 18 of the first voltage measurement circuit 13 and the AD converter 18a of the second voltage measurement circuit 13a, and detects an AC excitation current I E The frequency is synchronously detected using the same frequency as the frequency of the signal.

[0038] When mixers 21i and 21q receive the measured voltage from first voltage measurement circuit 13, they mix (multiply) the sample synchronization signals from first voltage measurement circuit 13 as voltages that are out of phase with each other by 90° and output the mixed voltages to filters 31i and 31q, respectively. Filters 31i and 31q are low-pass filters that band-limit the voltages that are input, and output the voltages that have passed the low range to absolute value calculator 41.

[0039] The output voltages of the filters 31i and 31q are components representing the real part Re and the imaginary part Im, respectively, and the absolute value calculator 41 calculates the square root of the sum of the squares of the real part Re and the imaginary part Im to output the synchronous detection circuit 14a. This result is output to a divider 43. The synchronous detection circuit 14a calculates the AC excitation current I E × Resistance value R of shunt resistor 12 S The measurement result I E ×R S is output to the divider 43a.

[0040] On the other hand, when mixers 22i and 22q receive the measured voltage of second voltage measurement circuit 13a, they mix (multiply) the sample synchronization signals of second voltage measurement circuit 13a as voltages that are out of phase with each other by 90° and output the mixed voltages to filters 32i and 32q, respectively. Filters 32i and 32q are low-pass filters that band-limit the voltages that are input, and output the voltages that have passed the low range to absolute value calculator 42.

[0041] The output voltages of the filters 32i and 32q are components representing the real part Re and the imaginary part Im, respectively, and the absolute value calculator 42 calculates the square root of the sum of the squares of the real part Re and the imaginary part Im to output the synchronous detection circuit 14a. This result is output to the divider 43a. As a result, the synchronous detection circuit 14a calculates the AC excitation current I E × Resistance value R of reference resistor 12a REF The measurement result I E ×R REF is output to the divider 43a.

[0042] The signal processing circuit 14 performs calculations using a divider 43a and a multiplier 44a based on the two output results of the synchronous detection circuit 14a. E ×R S The measurement result of the reference resistor 12a is I E ×R REF The divided value is multiplied by the reference resistance value R of the reference resistor 12a recorded in advance. REF is multiplied by a multiplier 44 to obtain the resistance value R S Measure.

[0043] Reference resistance value R of reference resistor 12a REF is measured in advance during the manufacture or inspection of the reference resistor 12a, and is recorded in advance in a non-volatile memory (not shown) of the signal processing circuit 14. Therefore, the signal processing circuit 14 performs the above-mentioned predetermined calculation using the divider 43a and the multiplier 44a to obtain the AC excitation current I E The effect of

[0044] Therefore, the AC excitation current I E Noise other than the main component contained in, for example, the load current I L Even if the external noise includes DC noise or low-frequency noise (1 / f noise, offset, etc.) of the first voltage measurement circuit 13 and the second voltage measurement circuit 13a, the influence of such noise can be eliminated. S can be measured with high accuracy.

[0045] The features of the synchronous detection circuit 14a are summarized as follows. S The resistance value R of the reference resistor 12a REF The component divided by is detected, and the reference resistance value R of the reference resistor 12a recorded in advance in the signal processing circuit 14 is detected. REF By multiplying this, the resistance value R of shunt resistor 12 is obtained. S This calculates the load current I L Even if external noise contains DC components, synchronous detection can be used to detect the AC excitation current I E Only the main component of the shunt resistor 12 can be detected, and as a result, noise can be eliminated. S can be detected with high accuracy.

[0046] In addition, the AC excitation current I E In a specific frequency band, the AC excitation current I E Since the signal processing circuit 14 calculates the output of the first voltage measurement circuit 13 by the output of the second voltage measurement circuit 13a, even if noise is included in the resistance value R of the shunt resistor 12, S can be detected with high accuracy.

[0047] <About DC measurement path 14c> On the other hand, the DC measurement path 14c of the signal processing circuit 14 is provided with a low-pass filter 45 that band-limits the measurement signal of the first voltage measurement circuit 13, and a low-pass filter 46 that band-limits the measurement signal of the second voltage measurement circuit 13a. An adder-subtractor 47 that adds / subtracts an offset, and a multiplier 49 that adjusts the gain of the output of the adder-subtractor 47 are provided downstream of the low-pass filter 45. An adder-subtractor 48 that adds / subtracts an offset, and a multiplier 49 that adjusts the gain of the output of the adder-subtractor 48 are provided downstream of the low-pass filter 46.

[0048] In the load current redundant detection mode, the signal processing circuit 14 detects the load current I LThe low-pass filters 45 and 46 detect the AC excitation current I E The cutoff frequency is set so as to cut off frequency components of the load current I. The low-pass filter 45 passes the low frequency range of the voltage measured by the first voltage measurement circuit 13 and cuts off high frequency noise exceeding the DC component. The low-pass filter 46 passes the low frequency range of the voltage measured by the second voltage measurement circuit 13a and cuts off high frequency noise exceeding the DC component. L Since the load current I L The principal components of can be obtained.

[0049] The adder / subtractors 47 and 48 add or subtract an offset to minimize the effect of low-frequency noise (1 / f noise, offset) of the first voltage measurement circuit 13 and the second voltage measurement circuit 13a. E This can eliminate the effects of excitation components including the load current I L The DC component can be measured with high accuracy.

[0050] Second embodiment The second embodiment will be described with reference to Figs. 4 to 8. A shunt-type current sensor 201 shown in Fig. 4 includes a first reference resistor 12a and a second reference resistor 12b instead of the reference resistor 12a described in the first embodiment. The first reference resistor 12a and the second reference resistor 12b are connected in series to the shunt resistor 12. The first reference resistor 12a and the second reference resistor 12b are preferably made of a material containing tantalum nitride, titanium nitride, or nitride. The first reference resistor 12a is a resistor having a resistance value R REF1 Calculate the reference resistance R REF1 are recorded in advance in the memory of the signal processing circuit 14.

[0051] The resistance value R of the first reference resistor 12a, the second reference resistor 12b, and the shunt resistor 12 REF1 , R REF2 , R S The relationship between REF1 >>R REF2 >>RS The resistance value R REF1 and resistance value R REF2 The relationship between the resistance value R REF2 and resistance value R S The relationship between the shunt resistor 12 and the first reference resistor 12a is preferably set to a difference of one to two digits, or two to three digits, for example, about 10:1 to 100:1, or 100:1 to 1000:1. The resistance value R of the shunt resistor 12 is calculated by taking the ratio between the shunt resistor 12 and the first reference resistor 12a. S Therefore, it is easier to measure by selecting resistance values ​​of approximately the same value. However, the commonly available high-precision, low-degradation standard resistor 12a has a resistance value of 10 Ω or more, so the first reference resistor 12a and the shunt resistor 12 have a resistance value R REF1 , R S The resistance value R of the first reference resistor 12a is significantly different from that of the first reference resistor 12b. REF1 is the resistance value R of the second reference resistor 12b REF2 and the resistance value R of shunt resistor 12 S The configuration is such that the amount of drift is reduced over a longer period of time.

[0052] The shunt-type current sensor 201 includes a current excitation circuit 252 instead of the current excitation circuit 52 described in the above embodiment. The current excitation circuit 252 includes AC excitation circuits 16 and 16a, each of which outputs a first AC excitation current I E1 , the second AC excitation current I E The first AC excitation current I E1 , the second AC excitation current I E The frequencies of the second AC excitation current I E is the AC excitation current I E The first AC excitation current I is a current similar to that of the first AC excitation current I , and is generated by a switching power supply circuit. On the other hand, it is preferable that the AC excitation circuit 16a is configured by a linear regulator (LDO). The linear regulator generates the first AC excitation current I , by toggling a switching element with a modulation signal of about several hundred Hz provided from the control circuit 10. E1 It is recommended to generate the following.

[0053] <Resistance value R of shunt resistor 12 in shunt resistance measurement mode S Measurement method> In the shunt resistance measurement mode, the signal processing circuit 14 performs a first measurement step Step1 and a second measurement step Step2 to obtain the resistance value R S At this time, in the first measurement step Step1, the control circuit 10 measures the first AC excitation current I E1 is applied to the first reference resistor 12a and the second reference resistor 12b. Then, the control circuit 10 switches the input / output of the multiplexer 19, thereby causing the first voltage measurement circuit 13 to detect the voltage across the first reference resistor 12a and the second voltage measurement circuit 13a to detect the voltage across the second reference resistor 12b.

[0054] In the second measurement step Step2, the control circuit 10 outputs a second AC excitation current I E is applied to the second reference resistor 12b and the shunt resistor 12. Then, the control circuit 10 switches the input / output of the multiplexer 19, thereby detecting the voltage applied to the second reference resistor 21b by the first voltage measurement circuit 13 and detecting the voltage applied to the shunt resistor 12 by the second voltage measurement circuit 13a.

[0055] In the shunt resistance measurement mode, the signal processing circuit 14 synchronously detects the outputs of the first voltage measurement circuit 13 and the second voltage measurement circuit 13a, and calculates a first AC excitation current I E1 , the second AC excitation current I E The signal processing circuit 14 extracts the main component of the resistance R of the shunt resistor 12 by the divider 43a. S The voltage applied to the second reference resistor 12b is calculated by the resistance R REF2 The resistance ratio R is calculated by dividing the result by the voltage applied to S / R REF2 Measure.

[0056] Furthermore, the signal processing circuit 14 calculates the resistance value R of the second reference resistor 12b by the divider 43b. REF2 The voltage applied to the first reference resistor 12a is calculated by the resistance R REF1The resistance ratio R is calculated by dividing the result by the voltage applied to REF2 / R REF1 The signal processing circuit 14 also calculates the resistance ratio R S / R REF2 and resistance ratio R REF2 / R REF1 and the resistance ratio R S / R REF1 The multiplier 44a calculates the resistance ratio R S / R REF1 The reference resistance value R of the first reference resistor 12a previously stored in the memory REF1 The resistance value R of shunt resistor 12 is calculated by multiplying S This allows the resistance value R of the shunt resistor 12 to be measured. S can be measured with high accuracy.

[0057] <Load current in redundant load current detection mode I L Measurement method> In the load current redundant detection mode, the signal processing circuit 14 detects the load current I L The DC measurement path 14c includes low-pass filters 45 and 46 as well as adders and subtractors 47 and 48. Thus, the signal processing circuit 14 applies the low-pass filters 45 and 46 to the outputs of the first voltage measurement circuit 13 and the second voltage measurement circuit 13a, respectively, to measure the load current I L can be measured.

[0058] Next, a desirable hardware configuration will be described with reference to Fig. 5 and Fig. 6. Fig. 5 and Fig. 6 show desirable hardware configurations of the shunt-type current sensors 201a and 201b of the second embodiment. As shown in Fig. 5 or Fig. 6, each block constituting the shunt-type current sensors 201a and 201b may be configured as hardware divided into an ASIC 50, a DSP 51, and a current excitation circuit 252 as integrated circuits.

[0059] 5, the ASIC 50 includes a control circuit 10, a first voltage measurement circuit 13, a second voltage measurement circuit 13a, and a multiplexer 19. The first voltage measurement circuit 13 includes a differential switched capacitor amplifier 17 and an AD converter 18 equipped with a ΔΣ modulator in the downstream thereof, forming an analog front-end 50a. The second voltage measurement circuit 13a includes a differential switched capacitor amplifier 17a and an AD converter 18a equipped with a ΔΣ modulator in the downstream thereof, forming an analog front-end 50a.

[0060] As shown in Fig. 5, the first reference resistor 12a, the second reference resistor 12b, and the anti-aliasing filters 20a, 20b, and 20 may be provided externally to the ASIC 50, but it is preferable to configure the first reference resistor 12a in the ASIC 50 as shown in the shunt-type current sensor 201b in Fig. 6. In particular, the first reference resistor 12a is preferably mounted on the same ASIC 50 (equivalent to an integrated circuit) on which the first voltage measurement circuit 13 and the second voltage measurement circuit 13a are mounted. By mounting the first reference resistor 12a on the same ASIC 50 on which the first voltage measurement circuit 13 and the second voltage measurement circuit 13a are mounted, it becomes unnecessary to provide an external reference resistor separately, and the first reference resistor 12a can be configured in a small area.

[0061] 6 also includes an anti-aliasing filter 20a. The anti-aliasing filter 20a is configured between the first reference resistor 12a and the multiplexer 19, and cuts frequency components higher than the Nyquist frequency before the measurement voltage of the first reference resistor 12a is input to the AD converters 18 and 18a.

[0062] Anti-aliasing filters 20b, 20 are configured outside the ASIC 50. The anti-aliasing filter 20b is configured between the second reference resistor 12b and the multiplexer 19, and cuts off frequency components higher than the Nyquist frequency before the measurement voltage of the second reference resistor 12b is input to the AD converters 18, 18a. The anti-aliasing filter 20 is configured between the shunt resistor 12 and the multiplexer 19, and cuts off frequency components higher than the Nyquist frequency before the measurement voltage of the shunt resistor 12 is input to the AD converters 18, 18a. In addition, in Figures 5 and 6, the same reference numerals are used for the same parts as those in Figure 4 described above, and the description of the same parts will be omitted.

[0063] Next, how to use each mode will be described with reference to FIGS. <Control during a specified long period> For example, regardless of whether the ignition switch of the vehicle is operated once every week or several weeks, the first measurement step Step 1 and the second measurement step Step 2 in the shunt resistance measurement mode may be executed as shown in FIG. 7. This is because the resistance value R of the first reference resistor 12a, which is relatively less affected by drift, is REF1 The resistance value R of shunt resistor 12 is calculated using S This is to measure.

[0064] 7, the control circuit 10 controls the current excitation circuit 52 to be turned off. The signal processing circuit 14 transitions to a load current redundant detection mode and measures the resistance value R of the shunt resistor 12 using the first voltage measurement circuit 13 and the second voltage measurement circuit 13a. S Measure the voltage across the load current I L Detect redundantly.

[0065] 7, the control circuit 10 turns on the current excitation circuit 52. The signal processing circuit 14 transitions to a shunt resistance measurement mode and measures the resistance value R of the second reference resistor 12b by the second voltage measurement circuit 13a in a first measurement step Step1. REF2The voltage across the first reference resistor 12a is measured by the first voltage measurement circuit 13, and the resistance value R REF1 As a result, the signal processing circuit 14 measures the resistance ratio R REF2 / R REF1 can be measured.

[0066] 7, the control circuit 10 also controls the operation of the current excitation circuit 52 to be on. In the second measurement step Step2 of the shunt resistance measurement mode, the signal processing circuit 14 measures the resistance value R S The voltage across the first reference resistor 12a is measured by the first voltage measurement circuit 13, and the resistance value R REF1 As a result, the signal processing circuit 14 measures the resistance ratio R S / R REF2 Therefore, by performing the above-mentioned measurement process, the resistance value R of the shunt resistor 12 can be measured. S can be measured.

[0067] 7, the control circuit 10 turns off the operation of the current excitation circuit 52. The signal processing circuit 14 transitions to a load current redundant detection mode and measures the resistance value R S Measure the voltage across the load current I L According to the flow of the time chart shown in FIG. 7, the second voltage measurement circuit 13a detects the shunt resistance R S The voltage applied to the

[0068] <Control during a specified short period> During a relatively short period, such as when the vehicle is starting up in response to the operation of the ignition switch, the signal processing circuit 14 may execute only the second measurement step Step 2 in the shunt resistance measurement mode, as shown in FIG. 8.

[0069] That is, the signal processing circuit 14 may execute the second measurement step Step2 without executing the first measurement step Step1 for calibration using the first reference resistor 12a. That is, when there is no need to perform calibration using the first reference resistor 12a that is less affected by drift, it is advisable to execute the process while omitting the first measurement step Step1, as shown at timings t10 to t12a and t12a to t13 in FIG. 8. Then, the result of the first measurement step Step1 recorded in advance, i.e., the resistance ratio R REF2 / R REF1 Using the result, the resistance value R of shunt resistor 12 is S Therefore, the processing time of the first measurement step, Step 1, can be omitted.

[0070] By performing the process shown in FIG. 8, the resistance value R S According to the flow of the time chart shown in FIG. 8, the second voltage measurement circuit 13a detects the shunt resistor R S This constantly monitors the voltage across the input terminals, eliminating the need to use multiplexer 19 for switching.

[0071] <Summary of this embodiment> According to the configuration of this embodiment, the resistance value R of the shunt resistor 12 is measured using the first voltage measurement circuit 13 and the second voltage measurement circuit 13a that are provided redundantly for functional safety. S It can be constructed at low cost to measure

[0072] When the signal processing circuit 14 performs signal processing in the resistance measurement mode while the vehicle is running, for example, the load current I L and AC excitation current I E However, by using the synchronous detection circuit 14a, these signals can be separated and detected with high accuracy.

[0073] The signal processing circuit 14 detects the AC excitation component from the synchronous detection circuit 14a, while extracting the DC excitation component through the low-pass filters 45 and 46. As a result, the signal processing circuit 14 calculates the load current I L At the same time, the resistance value R of the shunt resistor 12 can be calculated based on the AC excitation component. S The resistance value R of the shunt resistor 12 can be detected. S、 And the load current I L can be detected simultaneously.

[0074] According to the configuration shown in FIG. 6, although a highly accurate reference resistor 12a is required, detection can be performed at low cost by using the first reference resistor 12a built into the integrated circuit, and a highly accurate reference power supply can be eliminated. In this embodiment, the resistance value R of the shunt resistor 12 is calculated by taking the ratio between the reference resistor 12a and the reference resistor 12b and the ratio between the shunt resistor 12 and the reference resistor 12b. S Therefore, it is easier to measure by selecting resistance values ​​of approximately the same value. However, the first reference resistor 12a, which is generally available and has high accuracy and low deterioration, has a resistance value of 10 Ω or more. Therefore, the first reference resistor 12a and the shunt resistor 12 have a resistance value R REF1 , R S The resistances are composed of resistors that are significantly different from each other. If the resistance value ratio becomes too small, the signal entering the voltage measurement circuit becomes small, the signal-to-noise ratio becomes poor, and the resistance measurement accuracy deteriorates. Therefore, in order to increase the resistance value ratio, a resistance of several tens of milliohms, which is between the shunt resistor 12 of several tens of microohms and the reference resistor 12a of 10 ohms or more, is selected for the second reference resistor 12b. In addition, in the shunt resistance measurement mode, the measurement steps Step 1 and Step 2 are divided into two steps, so that the dynamic range can be expanded compared to one-step measurement. The first voltage measurement circuit 13 and the second voltage measurement circuit 13a for redundant detection can be configured without adding a voltage measurement circuit because they can handle two-step resistance measurement by switching the multiplexer 19.

[0075] In the shunt resistance measurement mode, the signal processing circuit 14 synchronously detects the outputs of the two voltage measurement circuits 13 and 13a using the synchronous detection circuit 14a, and detects the first AC excitation current IE1 and the second AC excitation current I E The principal component of the shunt resistor 12 is extracted and the resistance value R S The resistance value R of the second reference resistor 12b REF2 The resistance value R of the second reference resistor 12b is obtained by dividing the resistance value R REF2 The resistance value R of the first reference resistor 12a REF1 and multiplying the results of these divisions by the previously recorded reference resistance value R of the first reference resistor 12a. REF1 The resistance value R of shunt resistor 12 is calculated by multiplying S Calculate.

[0076] According to this configuration, the first AC excitation current I E1 , the second AC excitation current I E Even if noise is included in the resistance ratio R, the resistance ratio R can be calculated by dividing one of the outputs of the first voltage measurement circuit 13 and the second voltage measurement circuit 13a by the other output using the dividers 43a and 43b, so that the effect of the noise can be eliminated. S / R REF2 , R REF2 / R REF1 These resistance ratios are multiplied by a multiplier 44a to obtain the resistance value R of the shunt resistor 12. S can be calculated with high accuracy.

[0077] In the shunt resistance measurement mode, the signal processing circuit 14 applies a low-pass filter 45 to the output of the first voltage measurement circuit 13 that is measuring the shunt resistance 12, thereby obtaining a load current I L Since the AC excitation current I E The measured voltage can be removed as a noise component, and the load current I L In the shunt resistance measurement mode, the resistance value R of the shunt resistor 12 can be measured with high accuracy because the measurement is performed using the DC measurement path 14c simultaneously with the AC measurement path 14b. S along with the load current I L can be detected simultaneously.

[0078] In addition, the resistance value R of the first reference resistor 12a REF1is the resistance value R of the second reference resistor 12b REF2 and the resistance value R of shunt resistor 12 S The first reference resistor 12a, which has a small long-term drift value, is expensive. The expensive reference resistor is composed of only the first reference resistor 12a, and the resistance value R of the second reference resistor 12b is measured in the first measurement step Step1 and the second measurement step Step2. REF2 , the resistance value R of shunt resistor 12 S By correcting the resistance R of shunt resistor 12, S can be measured.

[0079] Third embodiment The third embodiment will be described with reference to FIG. 9. Explanation of the same parts as in the second embodiment will be omitted, and differences will be described. The shunt-type current sensor 301 shown in FIG. 9 includes a comparator 51 that compares the measured values ​​measured through the two voltage measurement circuits 13, 13a. As described in the previous embodiment, the signal processing circuit 14 detects the load current I L According to this embodiment, the comparator 51 detects two load currents I L When the abnormal value is exceeded, the signal processing circuit 14 outputs a signal indicating the detection of a fault in the DC measurement path 14c, the first voltage measurement circuit 13, or the second voltage measurement circuit 13a.

[0080] According to this embodiment, the load current I L In the DC measurement path 14c until the load current I is calculated, two paths are used. L Therefore, the functional safety requirements can be met by detecting failures by comparing these measured values ​​with comparator 51.

[0081] (Fourth embodiment) The fourth embodiment will be described with reference to Figs. 10 and 11. In the fourth embodiment, the structure of a shunt resistor 312 that replaces the shunt resistor 12 will be described. The same parts as those in the previous embodiment (for example, the first embodiment) are denoted by the same reference numerals, and the description will be omitted. Only the different parts will be described. The material of the shunt resistor 312 is a ferroelectric material having a resistance value R S It is preferable to use an alloy having as little temperature dependency as possible, for example an alloy containing copper, manganese, or nickel.

[0082] 10 and 11, the shunt resistor 312 is made of a copper material 312a and an alloy 312b. The shunt resistor 312 extends in the X direction, which is the longitudinal direction, and is made of the copper material 312a with the alloy 312b sandwiched in the middle part in the X direction.

[0083] As shown in Fig. 10, a printed wiring board 312c is fixed on the upper surface of the bifurcated copper material 312a and alloy 312b. The printed wiring board 312c has printed wiring formed thereon that connects the shunt resistor 12 to the first voltage measurement circuit 13 and the second voltage measurement circuit 13a. A temperature sensor 54 is mounted at the center of the printed wiring board 312c in the XY plane direction, and the temperature of the shunt resistor 312 can be measured by the temperature sensor 54. A connector 312d is soldered on the upper surface of the printed wiring board 312c, and is connected to the voltage measurement circuits 13 and 13a through the connector 312d and the multiplexer 19.

[0084] The connection points between the printed wiring board 312c and the shunt resistor 12 are provided so as to correspond to the measurement points of the voltage measurement circuits 13, 13a that measure the voltage applied to the shunt resistor 12. As shown in FIG. 11, two pairs of differential input points P1a-P1b and P2a-P2b are provided as the measurement points of the voltage measurement circuits 13, 13a.

[0085] The first pair of differential input locations P1a-P1b are located at the boundary between the alloy 312b and the copper material 312a where the alloy 312b is sandwiched, and the other pair of differential input locations P2a-P2b are located away from the first pair of differential input locations P1a-P1b on the outer side in the longitudinal X direction.

[0086] In this case, in the load current redundant detection mode, the differential input point P2a-P2b connected for redundant detection of the voltage of the shunt resistor 12 may be located outside the differential input point P1a-P1b of the main detection path. In the load current redundant detection mode, if the measurement point is the differential input point P2a-P2b, there is a risk of an error occurring by the resistance value of the copper material 312a, but the redundant detection voltage may be used only for fault diagnosis. In this case, a practical configuration can be achieved by locating the differential input point P2a-P2b outside the differential input point P1a-P1b so that the error is within the threshold value of the measurement voltage for fault diagnosis.

[0087] In the shunt resistance measurement mode, the voltage measurement circuit 13 detects the differential input points P1a-P1b, and the AC excitation current I E By setting the detection point and application point in this way, the common impedance for excitation and detection is set to the resistance value R of the shunt resistor 12. S As a result, the shunt resistor R S This makes it possible to measure with high accuracy. In this way, an additional path for excitation is not required, and as a result, the device can be constructed at low cost.

[0088] Fifth embodiment The fifth embodiment will be described with reference to Fig. 12 to Fig. 15. A shunt-type current sensor 501 shown in Fig. 12 includes a control circuit 10, a current excitation circuit 552, a voltage measurement circuit 13, a signal processing circuit 14, and a mixer 15, and is connected to a shunt resistor 12. The control circuit 10 outputs an AC carrier signal S C and AC modulation signal S M In the shunt resistance measurement mode, the shunt current sensor 501 outputs the resistance value R SWhen measuring, the control circuit 10 turns off the relay 59 (see FIG. 2) and supplies the AC carrier signal S C and AC modulation signal S M is output to the switching power supply circuit 11.

[0089] The current excitation circuit 552 includes the AC excitation circuit 16a described in the above embodiment. The current excitation circuit 552 also includes a switching power supply circuit 11. The switching power supply circuit 11 includes switching elements M1 to M3 as shown in FIG. 13. The switching power supply circuit 11 receives a carrier signal S C and the modulating signal S M The modulated carrier signal S is multiplied by the mixer 15. MC is input through the driver circuit 11a to drive the switching elements M1 to M3, and the modulated carrier signal S MC AC excitation current I E The power supply includes:

[0090] In practical use, as shown in FIG. 13, a driver circuit 11a is configured between the switching power supply circuit 11 and the mixer 15, but the driver circuit 11a is omitted from FIG. 12, which shows the characteristic parts of the present disclosure in a block diagram.

[0091] Carrier signal S C is a frequency f of several tens of kHz, for example, 10 kHz. C The square wave signal is of frequency f C The reciprocal of period T C The modulation signal S M is the carrier signal S C Lower frequency f M The signal is, for example, a rectangular wave signal of several hundred Hz. M The reciprocal of period T M The mixer 15 mixes the carrier signal S C and the modulating signal S M After multiplication, the modulated carrier signal S MC and outputs it to the switching power supply circuit 11.

[0092] Modulated carrier signal S MC is used as a signal for driving the switching power supply circuit 11. The modulated carrier signal S MC is a relatively low frequency modulating signal S M A relatively high frequency carrier signal S C In this application, a signal having the above relationship is referred to as a carrier signal S C , the modulated signal S M These carrier signals S C , the modulated signal S M The name is not limited to this name.

[0093] The switching power supply circuit 11 shown in FIG. 13 is driven through a driver circuit 11a, which outputs a drive signal S M1 , S M2 , S M3 The switching elements M1 to M3 are driven by inputting the second AC excitation current I E The switching elements M1 and M2 are configured with P-channel MOSFETs, and the switching element M3 is configured with an N-channel MOSFET. Although an example of the configuration of the switching power supply circuit 11 is shown in FIG. 13, the configuration of the switching power supply circuit 11 is not limited to this example.

[0094] 13 is configured as a synchronous rectification type switching power supply, and includes two switching elements M2 and M3 connected in series between a power supply node Ni of a power supply V0 and a ground node Ng, and an inductor L1 disposed between an intermediate node Na of the two switching elements M2 and M3 and an output node No of the switching power supply circuit 11. The power supply V0 is generated by stepping down the power supply of a battery 58. A second AC excitation current I E Since the impedance of the shunt resistor 12 that applies this current is small, at several tens of micro-ohms, by using an element that satisfies the condition of a lower on-resistance as the switching element M3, power can be output under conditions of lower power consumption than in the form of diode rectification.

[0095] Furthermore, the switching power supply circuit 11 includes a charge sampling switching element M1 connected in series between the DC power supply node Ni and the upstream switching element M2. The switching power supply circuit 11 also includes a capacitor C1 disposed in a charge sampling stage between an intermediate node Nb between the upstream switching element M2 and the charge sampling switching element M1 and a ground node Ng.

[0096] FIG. 14 shows the AC excitation current I E FIG. 15 shows an enlarged view of a portion A of the timing chart of FIG. 1. The driver circuit 11a receives the modulated carrier signal S MC When the carrier signal S C A drive signal S that becomes a high voltage for a predetermined period of time from the generation timing M1 At the same time, the drive signal S M1 A driving signal S that changes voltage complementary to M3 Output.

[0097] Drive signal S M1 The driving signal S drives the gate of the switching element M1, which is a P-channel MOSFET. M3 The driver circuit 11a drives the gate of the switching element M3, which is an N-channel MOSFET. Therefore, the switching elements M1 and M3 are simultaneously turned on or off. M1 and S M3 The drive signal S becomes low voltage only for a part of the time while it is an off drive signal. M2 The drive signal S M2 is applied to the gate of the switching element M2, which is a P-channel MOSFET.

[0098] As shown in Fig. 15, when the switching elements M1 and M3 are in the ON state, the switching element M2 is maintained in the OFF state. In this case, the capacitor C1 is charged from the node Ni through the switching element M1. Conversely, when the switching elements M1 and M3 are in the OFF state, the switching element M2 is in the ON state only for a part of the time.

[0099] The switching power supply circuit 11 supplies a second AC excitation current I E As a result, the second AC excitation current I E As shown in FIG. 14, the modulated signal S M Frequency f M A small amplitude carrier signal S is added to the large amplitude waveform C The second AC excitation current I E is the modulating signal S M The amplitude of the waveform of the carrier signal S C In other words, the switching power supply circuit 11 generates the carrier signal S so as to have a larger amplitude than that of the frequency of the carrier signal S in order to ensure a predetermined supply current. C Frequency f C While maintaining the switching frequency by E Output.

[0100] The switching power supply circuit 11 is provided with a charge sampling stage consisting of a switching element M1 and a capacitor C1. This allows a large current to be supplied from the capacitor C1 of the charge sampling stage, and the switching power supply circuit 11 can be configured with a low power supply capacity. As a result, the switching power supply circuit 11 can be configured at low cost.

[0101] In addition, since a large current during operation of the switching power supply circuit 11 can be supplied from the capacitor C1 of the charge sampling stage, fluctuations in the power output of the switching power supply circuit 11 can be suppressed. As a result, interference with other circuits can be suppressed, and the resistance value R of the shunt resistor 12 can be reduced. S can be measured with high accuracy.

[0102] Modulated carrier signal S MC is, for example, a relatively low frequency modulating signal S M A relatively high frequency carrier signal S C Therefore, the modulated signal S M A carrier signal S with a higher frequency than C In accordance with this embodiment, the switching power supply circuit 11 is designed to output a modulated carrier signal S. In the case where the switching elements M1 to M3 are selected to correspond to a low frequency, the element values ​​of the inductor L1 and the capacitor C1 become large, resulting in high costs. MC By driving with E can be produced easily and at low cost.

[0103] According to the configuration of this embodiment, the switching power supply circuit 11 reduces the voltage of the battery 58 from the main battery or the auxiliary battery to generate the second AC excitation current I E For example, the carrier signal S C In this case, there is a risk of high-frequency excitation due to size restrictions on the inductor L1 and capacitor C1 to be mounted, but this can be achieved by setting the inductance of the inductor L1 and the capacitance of the capacitor C1 to be large.

[0104] At this time, an error is likely to be large due to the influence of the skin effect of the shunt resistor 12. In order to suppress this error, according to this embodiment, the carrier signal S C The modulating signal S M The modulated signal S M As a result, the error can be reduced and the second AC excitation current I E According to this embodiment, a high-frequency carrier signal S C This produces a low-frequency modulation signal S MSince excitation is achieved by the inductor L1 and the capacitor C1, the sizes of the inductor L1 and the capacitor C1 can be reduced and the circuit can be constructed at low cost.

[0105] (Other embodiments) The present disclosure is not limited to the above-described embodiment, and can be implemented in various modifications and can be applied to various embodiments without departing from the spirit of the present disclosure. For example, the following modifications or extensions are possible. Each component is conceptual, and is not limited to the above-described embodiment.

[0106] In the above-described embodiment, a configuration in which the voltage across the shunt resistor 21 is detected using two voltage measurement circuits 13, 13a has been described. However, this is not limited to this, and for example, three or more voltage measurement circuits may be used for redundant detection.

[0107] The present disclosure includes the following inventions in addition to the inventions described in the claims. [1] A shunt-type current sensor using a shunt resistor for redundantly detecting a current flowing through a load, a reference resistor (12a) connected in series with the shunt resistor; a current excitation circuit (52; 252; 552) for generating an AC excitation current and passing the AC excitation current through the shunt resistor and the reference resistor; Two or more voltage measurement circuits (13, 13a) capable of measuring a voltage applied to the shunt resistor; a signal processing circuit (14) for processing a signal based on the measured voltage of the voltage measuring circuit; The signal processing circuit includes: a load current redundant detection mode in which the load current flowing through the load is redundantly detected by measuring a voltage across the shunt resistor using the two or more voltage measurement circuits in a state in which the AC excitation current from the current excitation circuit is not flowing through the reference resistor and the shunt resistor and a load current is flowing from the load to the shunt resistor; and a shunt resistance measurement mode for detecting a resistance value of the shunt resistance based on a voltage of the reference resistance and a voltage of the shunt resistance measured by the two or more voltage measurement circuits when the AC excitation current from the current excitation circuit is applied to the reference resistance and the shunt resistance, respectively. A shunt type current sensor that operates in either of the above modes.

[0108] [2] the signal processing circuit includes an AC measurement path that synchronously detects the measurement result of the voltage measurement circuit, In the shunt resistance measurement mode, a measurement signal of the voltage measurement circuit is synchronously detected by the AC measurement path to detect an AC component of the AC excitation current; A shunt type current sensor according to [1], wherein the component obtained by dividing the resistance value of the shunt resistor by the resistance value of the reference resistor is detected, and the resistance value of the shunt resistor is calculated by multiplying the component by a reference resistance value of the reference resistor that has been recorded in advance.

[0109] [3] the signal processing circuit includes a DC measurement path including a low-pass filter that band-limits the measurement signal of the voltage measurement circuit; In the load current redundant detection mode, the shunt-type current sensor [1] or [2] detects the load current by a signal obtained through the low-pass filter.

[0110] [4] The reference resistor is a first reference resistor (R REF1 ) and the second reference resistor (R REF2 ) and the first reference resistor and the second reference resistor are connected in series to the shunt resistor, In the shunt resistance measurement mode, the signal processing circuit In a first measurement step (Step 1), a first AC excitation current (I E1 ) to the first reference resistor and the second reference resistor, and a voltage applied to the first reference resistor and a voltage applied to the second reference resistor are detected by the voltage measurement circuit; In a second measurement step (Step 2), a second AC excitation current (I E ) to the second reference resistor and the shunt resistor, and the voltage measurement circuit detects the voltage across the second reference resistor and the voltage across the shunt resistor.

[0111] [5] In the shunt resistance measurement mode, the signal processing circuit A shunt-type current sensor according to claim 4, which calculates the resistance value of the shunt resistor by performing synchronous detection on the outputs of two voltage measurement circuits, extracting the principal components of the first AC excitation current and the second AC excitation current, dividing the resistance value of the shunt resistor output by synchronous detection by the resistance value of the second reference resistor, dividing the resistance value of the second reference resistor output by synchronous detection by the resistance value of the first reference resistor, and multiplying the results of these divisions together with the reference resistance value of the first reference resistor that was recorded in advance.

[0112] [6] In the shunt resistance measurement mode, the signal processing circuit A shunt type current sensor [4] or [5] that calculates the load current by applying a low-pass filter to the output of a voltage measurement circuit that measures the shunt resistance.

[0113] [7] A shunt-type current sensor according to any one of [4] to [6], wherein the resistance value of the first reference resistor is configured to drift less over a longer period of time than the resistance value of the second reference resistor and the resistance value of the shunt resistor.

[0114] [8] a comparator (51) for comparing two measured values ​​of two or more voltage measurement circuits in a load current redundant detection mode; A shunt-type current sensor according to any one of [4] to [6] that detects a fault in the measurement path or the voltage measurement circuit when the difference between the two measured values ​​exceeds any abnormal value.

[0115] [9] The shunt resistor is extended in a longitudinal direction and is made of a copper material with an alloy sandwiched in a middle portion thereof, A shunt-type current sensor according to any one of [1] to [8], wherein the measurement points of a voltage measurement circuit that measures the voltage across the shunt resistor are provided with two sets of differential input points, one set being located at the boundary between the alloy and the copper material where the alloy is sandwiched, and the other set being located at a position spaced apart from the first set of measurement points to the outside in the longitudinal direction.

[0116]

[10] A control circuit (10) is provided for outputting an AC carrier signal and an AC modulation signal, The shunt-type current sensor according to any one of [1] to [9], comprising: a switching power supply circuit (11) having a switching element, driving the switching element with a modulated carrier signal obtained by multiplying the carrier signal and a modulation signal, and outputting a power supply including an AC excitation current due to the modulated carrier signal.

[0117]

[11] The shunt-type current sensor according to any one of [4] to

[10] , wherein the first reference resistor is mounted on the same integrated circuit as the integrated circuit on which the voltage measurement circuit is mounted.

[0118]

[12] The shunt-type current sensor according to any one of [4] to

[11] , wherein the first reference resistor is made of a material including tantalum nitride, titanium nitride, or nitride.

[0119] The techniques described in the present disclosure may be implemented by a special purpose computer provided by configuring a processor and memory programmed to perform one or more functions embodied in a computer program. Alternatively, the techniques described in the present disclosure may be implemented by a special purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the techniques described in the present disclosure may be implemented by one or more special purpose computers configured by a combination of a processor and memory programmed to perform one or more functions and a processor configured with one or more hardware logic circuits. Also, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions executed by the computer.

[0120] Although the present disclosure has been described based on the above-mentioned embodiment, it is understood that the present disclosure is not limited to the embodiment or the structure described in the embodiment. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure. [Explanation of symbols]

[0121] In the drawings, 1 and 201 denote shunt type current sensors, 52, 252, and 552 denote current excitation circuits, 12 denotes a shunt resistor, 12a denotes a reference resistor, 13 denotes a first voltage measurement circuit, 13a denotes a second voltage measurement circuit, 14 denotes a signal processing circuit, and 52, 252, and 552 denote current excitation circuits.

Claims

1. A shunt-type current sensor using a shunt resistor for redundantly detecting a current flowing through a load, A reference resistor (12a) connected in series with the shunt resistor; a current excitation circuit (52; 252; 552) for generating an AC excitation current and passing the AC excitation current through the shunt resistor and the reference resistor; Two or more voltage measurement circuits (13, 13a) capable of measuring a voltage applied to the shunt resistor; A signal processing circuit (14) that processes a signal based on the measured voltage of the voltage measurement circuit, The signal processing circuit includes: a load current redundant detection mode in which the load current flowing through the load is redundantly detected by measuring a voltage across the shunt resistor using the two or more voltage measurement circuits in a state in which the AC excitation current from the current excitation circuit is not flowing through the reference resistor and the shunt resistor and a load current is flowing from the load to the shunt resistor; and a shunt resistance measurement mode for detecting a resistance value of the shunt resistance based on a voltage of the reference resistance and a voltage of the shunt resistance measured by the two or more voltage measurement circuits when the AC excitation current from the current excitation circuit is applied to the reference resistance and the shunt resistance, respectively. A shunt type current sensor that operates in either of the above modes.

2. the signal processing circuit includes an AC measurement path that synchronously detects the measurement result of the voltage measurement circuit, In the shunt resistance measurement mode, a measurement signal of the voltage measurement circuit is synchronously detected by the AC measurement path to detect an AC component of the AC excitation current; 2. The shunt type current sensor according to claim 1, wherein the resistance value of the shunt resistor is calculated by detecting a component obtained by dividing the resistance value of the shunt resistor by the resistance value of the reference resistor and multiplying the component by a reference resistance value of the reference resistor that is recorded in advance.

3. the signal processing circuit includes a DC measurement path including a low-pass filter that band-limits the measurement signal of the voltage measurement circuit; 3. The shunt-type current sensor according to claim 2, wherein in the load current redundant detection mode, the load current is detected by a signal obtained through the low-pass filter.

4. the reference resistor is composed of a first reference resistor (12a) and a second reference resistor (12b), and is configured by connecting the first reference resistor and the second reference resistor in series to the shunt resistor; In the shunt resistance measurement mode, the signal processing circuit In a first measurement step (Step 1), a first AC excitation current (I Ｅ１ ) to the first reference resistor and the second reference resistor, and a voltage applied to the first reference resistor and a voltage applied to the second reference resistor are detected by the voltage measurement circuit; In a second measurement step (Step 2), a second AC excitation current (I Ｅ 2. The shunt type current sensor according to claim 1, wherein a voltage applied to the second reference resistor and the shunt resistor is applied to the second reference resistor and the shunt resistor, and the voltage measuring circuit detects a voltage applied to the second reference resistor and a voltage applied to the shunt resistor.

5. In the shunt resistance measurement mode, the signal processing circuit 5. The shunt type current sensor according to claim 4, further comprising: synchronously detecting outputs of two voltage measurement circuits; extracting principal components of the first AC excitation current and the second AC excitation current; dividing the resistance value of the shunt resistor output by synchronous detection by the resistance value of the second reference resistor; dividing the resistance value of the second reference resistor output by synchronous detection by the resistance value of the first reference resistor; and multiplying these division results by a reference resistance value of the first reference resistor that has been recorded in advance, thereby calculating the resistance value of the shunt resistor.

6. In the shunt resistance measurement mode, the signal processing circuit 6. The shunt type current sensor according to claim 5, wherein the load current is calculated by applying a low-pass filter to the output of a voltage measuring circuit that measures the shunt resistance.

7. 7. The shunt type current sensor according to claim 6, wherein the resistance value of the first reference resistor has a smaller drift amount over a longer time period than the resistance values ​​of the second reference resistor and the shunt resistor.

8. a comparator (51) for comparing two measured values ​​of two or more voltage measurement circuits in a load current redundant detection mode; 7. The shunt-type current sensor according to claim 6, wherein a failure in the measurement path or the voltage measurement circuit is detected when a difference between the two measured values ​​exceeds an arbitrary abnormal value.

9. The shunt resistor is extended in a longitudinal direction and is made of a copper material with an alloy sandwiched in a middle portion thereof, A shunt type current sensor as described in claim 6, wherein the measurement points of the voltage measurement circuit that measures the voltage across the shunt resistor are provided with two sets of differential input points, one set being located at the boundary between the alloy and the copper material where the alloy is sandwiched, and the other set being located at a distance outside the first set of measurement points in the longitudinal direction.

10. A control circuit (10) is provided for outputting an AC carrier signal and an AC modulation signal, 7. The shunt type current sensor according to claim 6, wherein the current excitation circuit comprises: a switching power supply circuit (11) that has a switching element, drives the switching element with a modulated carrier signal obtained by multiplying the carrier signal and the modulation signal, and outputs a power supply including an AC excitation current due to the modulated carrier signal.

11. The shunt-type current sensor according to claim 10 , wherein the first reference resistor is mounted on the same integrated circuit as the voltage measuring circuit.

12. The shunt-type current sensor according to claim 11 , wherein the first reference resistor is made of a material including tantalum nitride, titanium nitride, or nitride.

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