Inductive current detection device and detection method

Abstract

The invention provides an inductive current detection device and a detection method, which are used for solving the technical problems that a measuring device is large in size and high in cost, or only inductive current with the frequency higher than that of a certain component can be detected, and the detection error amount of low-frequency inductive current is very large in an existing inductive current detection mode. According to the inductive current detection device, the first sensing unit in the detection circuit senses the high-frequency AC voltage signal corresponding to the inductive current, and the second sensing unit senses the low-frequency AC + DC voltage signal corresponding to the inductive current; and the low-frequency AC + DC voltage signal corresponding to the inductive current is subjected to gain amplification by K-1 times through the K-1-time gain amplification channel and then is superposed with the high-frequency AC voltage signal, so that the full-band real-time detection of the inductive current can be realized, and the measurement precision and reliability of the inductive current are effectively improved.

Description

Technical Field

[0001] The present invention relates to an inductor current detection device and method, and in particular to an inductor current detection device and method. Background Art

[0002] In modern power electronic devices, accurate sensing of inductor current is critical to improving system performance and efficiency, especially in switching power supplies, electric vehicle drives, and other power conversion applications.

[0003] There are two main methods for detecting inductor current. One is to measure the inductor current in a non-isolated manner using magnetic coupling, and the other is to measure the inductor current using board-level capacitance. Figure 1 As shown in the figure, it is a circuit topology diagram for non-isolated measurement of inductor current using magnetic coupling. Although this method of measuring inductor current is accurate, it is limited by the bandwidth of magnetic coupling. In addition, since the magnetic coupling component cannot be integrated with the inductor, additional wiring is required, resulting in a large size of the measurement device and a correspondingly high cost. Figure 2 As shown in FIG. 1 , a circuit topology diagram for measuring the inductor current using a board-level capacitor is shown. However, this method of measuring the inductor current can only detect the inductor current with a frequency higher than a certain component. It has a large gain and detection accuracy for the AC component of the inductor current. For the low-frequency inductor current, the detection error is very large, resulting in this detection method being used only as a protection. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problems that the existing inductor current detection method has large measurement device size and high cost, or can only detect the inductor current with a frequency higher than a certain component, and has a large detection error for the low-frequency inductor current, and to provide an inductor current detection device and detection method.

[0005] In order to achieve the above purpose, the technical solution of the present invention is as follows:

[0006] An inductor current detection device is used to detect the current passing through an inductor, wherein the inductor comprises an inductor body L and a parasitic resistor DCR connected in series; the device is special in that it comprises a detection circuit and a calculation unit;

[0007] The detection circuit includes a first sensing unit, a second sensing unit, a gain amplifier, an analog-to-digital conversion unit, and a signal processing unit;

[0008] The first sensing unit includes a resistor R1 and a capacitor C1 connected in series, the other end of the resistor R1 is used to connect the other end of the inductor body L, the other end of the capacitor C1 is used to connect the other end of the parasitic resistor DCR, and the first sensing unit is used to sense the high-frequency AC voltage signal corresponding to the inductor current;

[0009] The second sensing unit includes a capacitor C2 and a resistor R2 connected in series, the other end of the capacitor C2 is connected between the resistor R1 and the capacitor C1, and the other end of the resistor R2 is connected to the other end of the capacitor C1, and the second sensing unit is used to sense the low-frequency AC+DC voltage signal corresponding to the inductor current;

[0010] The capacity of the capacitor C2 is less than or equal to 1 / K of the capacity of the capacitor C1, and is used to distinguish the frequency, where K is the total gain multiple of the gain amplifier;

[0011] The gain amplifier is provided with a K-1 times gain amplification channel and a unit gain channel; one input end of the K-1 times gain amplification channel is connected between the resistor R1 and the capacitor C1, and the other input end is connected between the capacitor C2 and the resistor R2, for collecting the low-frequency AC+DC voltage signal corresponding to the inductor current and performing gain amplification on it; one input end of the unit gain channel is connected between the capacitor C2 and the resistor R2, and the other input end is connected to the other end of the resistor R2, for collecting and maintaining the high-frequency AC voltage signal corresponding to the inductor current;

[0012] The two input ends of the analog-to-digital conversion unit are respectively connected to the output ends of the K-1 times gain amplification channel and the unity gain channel, and are used to convert the gain-amplified low-frequency AC+DC voltage signal of the inductor current and the maintained high-frequency AC voltage signal into a digital signal after superposition;

[0013] The input end of the signal processing unit is connected to the output end of the analog-to-digital conversion unit, and is used to filter and amplify the input digital signal;

[0014] The input end of the calculation unit is connected to the output end of the signal processing unit, and is used to obtain an accurate value of the inductor current according to the filtered and amplified digital signal.

[0015] Furthermore, the calculation unit calculates the exact value of the inductor current I by the following formula: L :

[0016] I L =Vtotal / (L*DCR)

[0017] In the above formula, Vtotal is the analog voltage signal output by the signal processing unit, and DCR is the resistance value of the inductor parasitic resistance.

[0018] Furthermore, the capacity of the capacitor C2 is equal to 1 / 10 of the capacity of the capacitor C1.

[0019] Furthermore, the first sensing unit and the second sensing unit are integrated on the inductor body L.

[0020] Furthermore, the signal processing unit adopts a Kalman filter algorithm to implement filtering, thereby reducing the measurement error by compensating for the measurement deviation caused by the change of ambient temperature.

[0021] In addition, the present invention also provides an inductor current detection method, which uses the above-mentioned inductor current detection device, and its special feature is that it includes the following steps:

[0022] Step 1, convert the current passing through the inductor into a voltage signal through the parasitic resistance DCR;

[0023] Step 2, sensing a high-frequency AC voltage signal corresponding to the inductor current through a first sensing unit, and sensing a low-frequency AC+DC voltage signal corresponding to the inductor current through a second sensing unit;

[0024] Step 3, amplifying the low-frequency AC+DC voltage signal corresponding to the inductor current by K-1 times through the K-1 times gain amplification channel of the gain amplifier, and at the same time collecting and maintaining the high-frequency AC voltage signal corresponding to the inductor current through the unity gain channel;

[0025] Step 4, superimposing the gain-amplified low-frequency AC+DC voltage signal and the high-frequency AC voltage signal of the inductor current through an analog-to-digital conversion unit, and converting them into an analog voltage signal; and then filtering and amplifying the input analog voltage signal through a signal processing unit;

[0026] Step 5: The calculation unit calculates the accurate value of the inductor current according to the filtered and amplified analog voltage signal.

[0027] Furthermore, in step 5, the exact value of the inductor current I is calculated by the following formula: L :

[0028] I L =Vtotal / (L*DCR)

[0029] In the above formula, Vtotal is the analog voltage signal output by the signal processing unit, and DCR is the resistance value of the inductor parasitic resistance.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. An inductor current detection device provided by the present invention senses a high-frequency AC voltage signal corresponding to the inductor current through a first sensing unit in a detection circuit, senses a low-frequency AC+DC voltage signal corresponding to the inductor current through a second sensing unit, and then amplifies the low-frequency AC+DC voltage signal corresponding to the inductor current by K-1 times through a K-1 times gain amplification channel and superimposes the gain with the high-frequency AC voltage signal, thereby realizing real-time detection of the full frequency band of the inductor current, effectively improving the measurement accuracy and reliability of the inductor current, and being more practical.

[0032] 2. The present invention can accurately detect the current change in the inductor by integrating the first sensing unit and the second sensing unit next to the inductor. At the same time, combined with a high-precision analog-to-digital conversion unit and an advanced digital filtering algorithm, real-time monitoring and analysis of the inductor current can be achieved.

[0033] 3. The inductor current detection device provided by the present invention has a simple structure and can calibrate the current flowing through different inductors, thereby reducing the impact of temperature and environmental changes on measurement accuracy, and can be suitable for miniaturized occasions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The topology diagram of the circuit for measuring the inductor current in a non-isolated manner by means of magnetic coupling is shown;

[0035] Figure 2 The topology diagram of the circuit for measuring the inductor current by using the board-level capacitor is shown;

[0036] Figure 3 A topological diagram of a detection circuit in an embodiment of an inductor current detection device of the present invention;

[0037] Figure 4 A simulation test circuit according to an embodiment of the present invention;

[0038] Figure 5 is a curve diagram showing the gain variation of the inductor current with respect to the frequency measured by the embodiment of the present invention;

[0039] Figure 6 The voltage and current waveforms obtained by the simulation test circuit of the embodiment of the present invention, wherein the pink curve is the inductor current curve detected by the solution of the present invention, and the khaki curve is the voltage curve of the resistor R2 in the second sensing unit;

[0040] Figure 7 Schematic diagram of the inductor current waveform detected by the current sensor using magnetic coupling and the inductor current detection device of the present invention, wherein the blue line is the inductor current waveform detected by the current sensor using magnetic coupling, and the orange line is the low-frequency DC waveform of the inductor current detected by the inductor current detection device of the present invention;

[0041] Figure 8 The figure is a schematic diagram of the error of the inductor current detected by the current sensor using magnetic coupling and the inductor current detection device of the present invention. DETAILED DESCRIPTION

[0042] In order to make the advantages and features of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] The inductor current detection device of the present invention is used to detect the current passing through the inductor. In the present invention, the inductor is equivalent to a series integrated structure of an inductor body L and a parasitic resistor DCR, that is, one end of the inductor body L is connected to one end of the parasitic resistor DCR to be equivalent to an inductor. The current passing through the inductor body L can be converted into a voltage signal through the parasitic resistor DCR, thereby realizing the detection of the inductor current change.

[0044] like Figure 1 As shown, an inductor current detection device includes a detection circuit and a calculation unit. The detection circuit includes a first sensing unit, a second sensing unit, a gain amplifier, an analog-to-digital conversion unit, a signal processing unit, and a calculation unit. Preferably, the first sensing unit and the second sensing unit can be integrated on the inductor body L.

[0045] The first sensing unit includes a resistor R1 and a capacitor C1, one end of the resistor R1 is connected to one end of the capacitor C1, the other end of the resistor R1 is used to connect the other end of the inductor body L, and the other end of the capacitor C1 is used to connect the other end of the parasitic resistor DCR. The second sensing unit includes a capacitor C2 and a resistor R2, one end of the capacitor C2 is connected to one end of the resistor R2, the other end of the capacitor C2 is connected between the resistor R1 and the capacitor C1, and the other end of the resistor R2 is connected to the other end of the capacitor C1. In order to distinguish the frequency, the capacity of the capacitor C2 needs to be less than or equal to 1 / K of the capacity of the capacitor C1. In this embodiment, the capacity of the capacitor C2 is 1 / 10 of the capacity of the capacitor C1.

[0046] Since the current flowing through the resistor R1 can be a low-frequency DC amount, a low-frequency AC amount, and a high-frequency AC amount, and the current flowing through the capacitor C1 must be a high-frequency AC amount to generate a voltage, the first sensing unit is used to sense the high-frequency AC voltage signal corresponding to the inductor current. Since the capacitor C1 consumes the high-frequency AC amount of the current, only the low-frequency AC amount and the low-frequency DC amount flow through the capacitor C2, so the second sensing unit is used to sense the low-frequency AC+DC voltage signal corresponding to the inductor current.

[0047] The gain amplifier is provided with a K-1 times gain amplification channel and a unit gain channel, where K is the total gain multiple of the gain amplifier. One input end of the K-1 times gain amplification channel is connected between the resistor R1 and the capacitor C1, and the other input end is connected between the capacitor C2 and the resistor R2, for collecting the low-frequency AC+DC voltage signal corresponding to the inductor current and performing gain amplification on it to increase the sensing degree of the low-frequency AC+DC voltage signal corresponding to the inductor current. One input end of the unit gain channel is connected between the capacitor C2 and the resistor R2, and the other input end is connected to the other end of the resistor R2, for collecting and maintaining the high-frequency AC voltage signal corresponding to the inductor current.

[0048] The two input ends of the analog-to-digital conversion unit are respectively connected to the output ends of the K-1 times gain amplification channel and the unity gain channel in the gain amplifier, and are used to superimpose the low-frequency AC+DC voltage signal of the inductor current after gain amplification and the maintained high-frequency AC voltage signal, and convert the superimposed voltage signal into a digital signal.

[0049] The input end of the signal processing unit is connected to the output end of the analog-to-digital conversion unit, and is used to filter and amplify the input digital signal. Preferably, in this embodiment, a Kalman filter algorithm is used to implement filtering, and the measurement error is reduced by compensating for the measurement deviation caused by the change of ambient temperature.

[0050] The input end of the calculation unit is connected to the output end of the signal processing unit, and is used to obtain the accurate value of the inductor current according to the filtered and amplified digital signal. Specifically, the accurate value of the inductor current IL is calculated by the following formula:

[0051] I L =Vtotal / (K*DCR)

[0052] In the above formula, Vtotal is the analog voltage signal output by the signal processing unit.

[0053] In this embodiment, the total gain multiple K of the gain amplifier is designed to be 10 times, then:

[0054] ωR1*C1=10*ωDCR=ωR2*C2

[0055] The detection accuracy of the inductor current obtained by the signal processing unit is 10 times that of the inductor current sensed by the parasitic resistance DCR.

[0056] Because there are:

[0057]

[0058] In the above formula, V C2 is the voltage of capacitor C2, I L is the current flowing through the inductor body L, s is the complex frequency, and ω is the actual frequency.

[0059] Then we have:

[0060]

[0061] That is I L =Vtotal / (K*DCR).

[0062] In order to further illustrate the effect of the present invention, the detection circuit of the present invention is used to simulate the inductor to be tested formed by the inductor body L of 220nH and the parasitic resistance DCR of 0.29mΩ. The simulation test circuit is as follows: Figure 4 shown.

[0063] like Figure 5 1 is a graph showing a gain variation curve of the inductor current measured with frequency using an embodiment of the present invention, wherein the orange curve is a gain variation curve of the inductor current sensed by the first sensing unit (R1C1) with frequency, the red curve is a gain variation curve of the inductor current sensed by the second sensing unit (R2C2) with frequency, and the dashed line above is the actual gain of the inductor current sampled by the inductor current detection device of the present invention, with a frequency of 10 3 As the boundary, it can be seen that the first sensing unit composed of resistor R1 and capacitor C1 has a large gain at low frequency, and the second sensing unit composed of resistor R2 and capacitor C2 has a large gain at high frequency. Therefore, the inductor current detection device of the present invention can detect the current of the inductor at both high and low frequencies. The blue curve in the figure is the gain of the inductor current measured by the traditional board-level capacitor method. For example, after the present invention increases the sampling gain on both sides of the second sensing unit composed of capacitor C2 and resistor R2 by 20dB (K=10), the inductor current measurement gain obtained by using the present invention is 10 times the measurement gain of the traditional board-level capacitor method. Since the parasitic resistance DCR of the inductor is small, the detected inductor current is also small. After the scheme increases the gain of the inductor current by 10 times, the interference of clutter on the inductor current detection can be reduced, the signal-to-noise ratio is increased by 10 times, and the accuracy of the inductor current detection is also increased by ten times. Compared with the existing scheme, the accuracy of the inductor current detection can be greatly increased.

[0064] like Figure 6 As shown, it is based on Figure 4 The voltage and current waveforms obtained by the constructed simulation test circuit, wherein the pink curve is the inductor current curve detected by the solution of the present invention, and the khaki curve is the voltage curve of the resistor R2 in the second sensing unit, that is, the AC part sensed by the second sensing unit. It can be confirmed from the simulation measurement value that the measured AC inductor current is consistent with the current flowing through the inductor, meeting the high-precision detection requirements.

[0065] like Figure 7 , which is a schematic diagram of the inductor current waveform detected by the current sensor using the magnetic coupling method and the inductor current detection device of the present invention, wherein the blue line is the inductor current waveform detected by the current sensor using the magnetic coupling method, and the orange line is the low-frequency DC waveform of the inductor current detected by the inductor current detection device of the present invention. It can be seen that the two lines are almost overlapped, reflecting that the inductor current detection scheme proposed by the present invention has high accuracy for the low-frequency DC part of the current; Figure 8As shown, it is a schematic diagram of the error of the inductor current detected by the current sensor using magnetic coupling and the inductor current detection device of the present invention. It can be seen that the error is less than 0.7%. Therefore, the present invention can not only realize the effective detection of low-frequency DC signals, but also ensure high-precision detection.

[0066] The above description is only used to illustrate the technical solution of the present invention rather than to limit it. For ordinary professional and technical personnel in the field, the specific technical solution recorded in the above embodiment can be modified, or some of the technical features therein can be replaced by equivalents, and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution protected by the present invention.

Claims

1. An inductor current detection device, used for detecting the current passing through an inductor, wherein the inductor comprises an inductor body L and a parasitic resistor DCR connected in series; Features: including a detection circuit and a calculation unit; The detection circuit includes a first sensing unit, a second sensing unit, a gain amplifier, an analog-to-digital conversion unit, and a signal processing unit; The first sensing unit includes a resistor R1 and a capacitor C1 connected in series, the other end of the resistor R1 is used to connect the other end of the inductor body L, the other end of the capacitor C1 is used to connect the other end of the parasitic resistor DCR, and the first sensing unit is used to sense the high-frequency AC voltage signal corresponding to the inductor current; The second sensing unit includes a capacitor C2 and a resistor R2 connected in series, the other end of the capacitor C2 is connected between the resistor R1 and the capacitor C1, and the other end of the resistor R2 is connected to the other end of the capacitor C1, and the second sensing unit is used to sense the low-frequency AC+DC voltage signal corresponding to the inductor current; The capacity of the capacitor C2 is less than or equal to 1 / K of the capacity of the capacitor C1, where K is the total gain multiple of the gain amplifier; The gain amplifier is provided with a K-1 times gain amplification channel and a unit gain channel, wherein one input end of the K-1 times gain amplification channel is connected between the resistor R1 and the capacitor C1, and the other input end is connected between the capacitor C2 and the resistor R2, for collecting the low-frequency AC+DC voltage signal corresponding to the inductor current and performing gain amplification on it; one input end of the unit gain channel is connected between the capacitor C2 and the resistor R2, and the other input end is connected to the other end of the resistor R2, for collecting and maintaining the high-frequency AC voltage signal corresponding to the inductor current; The two input ends of the analog-to-digital conversion unit are respectively connected to the output ends of the K-1 times gain amplification channel and the unity gain channel, and are used to convert the gain-amplified low-frequency AC+DC voltage signal of the inductor current and the maintained high-frequency AC voltage signal into a digital signal after superposition; The input end of the signal processing unit is connected to the output end of the analog-to-digital conversion unit, and is used to filter and amplify the input digital signal; The input end of the calculation unit is connected to the output end of the signal processing unit, and is used to obtain an accurate value of the inductor current according to the filtered and amplified digital signal.

2. The inductor current detection device according to claim 1, characterized in that: The calculation unit calculates the exact value of the inductor current I by the following formula: L : I L =Vtotal / (K*DCR) In the above formula, Vtotal is the analog voltage signal output by the signal processing unit, and DCR is the resistance value of the inductor parasitic resistance.

3. The inductor current detection device according to claim 2, characterized in that: The capacity of the capacitor C2 is equal to 1 / 10 of the capacity of the capacitor C1.

4. The inductor current detection device according to claim 3, characterized in that: The first sensing unit and the second sensing unit are integrated on the inductor body L.

5. An inductor current detection device according to any one of claims 1 to 4, characterized in that: The signal processing unit uses a Kalman filter algorithm to implement filtering.

6. An inductor current detection method, using the inductor current detection device according to any one of claims 1 to 5, characterized in that: The following steps are involved: Step 1, convert the current passing through the inductor into a voltage signal through the parasitic resistance DCR; Step 2, sensing a high-frequency AC voltage signal corresponding to the inductor current through a first sensing unit, and sensing a low-frequency AC+DC voltage signal corresponding to the inductor current through a second sensing unit; Step 3, amplifying the low-frequency AC+DC voltage signal corresponding to the inductor current by K-1 times through the K-1 times gain amplification channel of the gain amplifier, and at the same time collecting and maintaining the high-frequency AC voltage signal corresponding to the inductor current through the unity gain channel; Step 4, superimposing the gain-amplified low-frequency AC+DC voltage signal and the high-frequency AC voltage signal of the inductor current through an analog-to-digital conversion unit, and converting them into an analog voltage signal; and then filtering and amplifying the input analog voltage signal through a signal processing unit; Step 5: The calculation unit calculates the accurate value of the inductor current according to the filtered and amplified analog voltage signal.

7. The inductor current detection method according to claim 6, characterized in that: In step 5, the exact value of the inductor current I is calculated using the following formula: L : I L =Vtotal / (K*DCR) In the above formula, Vtotal is the analog voltage signal output by the signal processing unit, and DCR is the resistance value of the inductor parasitic resistance.

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