A switch current measurement method integrated into a power module

Abstract

The present invention is a switch current measurement method integrated into a power module, the current sensor used in the method includes a Rogowski coil and a processing circuit; two Rogowski coils are integrated into the power module to form a differential Rogowski coil, the processing circuit is located outside the power module, the output ends of the two Rogowski coils are connected to the input ends of the processing circuit, and the ground ends of the two Rogowski coils are connected to the ground end of the processing circuit; the Rogowski coil is planarly etched on an island structure of a copper layer on a DBC substrate of a packaging structure inside the power module, the Rogowski coil has no electrical connection with the copper layer on the DBC substrate, the current-carrying conductor of the measured switch current of the power module is located above the Rogowski coil and does not contact the Rogowski coil, and the two Rogowski coils are symmetrically located on both sides of the current-carrying conductor. The Rogowski coil can be integrated into the power module by only changing part of the structural layout without changing the existing packaging structure of the power module, solving the problem of wide bandwidth of the existing Rogowski coil and difficult integration of current sensors.

Description

Technical Field

[0001] The invention belongs to the technical field of switch current measurement, and in particular is a switch current measurement method integrated into a power module. Background Art

[0002] Current sensors play a vital role in modern power electronic systems. The switching current information of power devices is the common key information required for power electronic fault protection, health monitoring and control. At present, extensive research has been carried out on current sensing technology in power electronic systems. Current can be measured by shunts, current transformers, Rogowski coils, Hall sensors and magnetoresistive sensors.

[0003] Shunts are the most cost-effective. Although the working principle based on Ohm's law is simple, actual current shunts have inherent inductance, which limits their measurement accuracy and bandwidth (from DC to tens of megahertz); in addition, at high frequencies, the resistance of the shunt changes due to the skin effect, so the shunt cannot accurately measure the switching current of the power module. Although commercial coaxial shunts solve the bandwidth problem, their structure is usually cylindrical and large in size, which is not suitable for integration into the power module. Although current transformers have the advantages of isolation and low power consumption, they usually use magnetic core materials in practical applications, so there are problems such as core saturation, increased size and cost. At the same time, since current transformers introduce additional inductance on the current-carrying conductor, this will affect the high-frequency performance of the power module. The Hall sensor is a magnetic field sensor based on the Hall effect. It is an isolated, non-invasive sensor that can be used for DC to AC current measurement. However, due to the magnetic saturation phenomenon, its bandwidth is usually only a few hundred kilohertz, and it cannot accurately measure the switching current information of the power module.

[0004] The Rogowski coil is an air-core coil without the problem of core saturation. It also has the advantages of high bandwidth, large measurement range, isolation, non-intrusion and easy integration. It is a good choice for current sensors integrated into power modules to measure switching currents. Figure 1 This is the schematic diagram of the traditional Rogowski coil for measuring the switching current. However, most commercial Rogowski coils are flexible Rogowski coils, which have problems such as large size and difficulty in fixing, and cannot be integrated into the power module. Traditional PCB Rogowski coils are mostly made of glass fiber epoxy resin FR-4 material. The "glass transition temperature" of FR-4 is usually below 135°C, while the current maximum operating temperature of power modules can generally reach 150°C or even 175°C. High temperature will cause FR-4 to change from a glassy state to a highly elastic state and undergo obvious deformation, which will cause irreversible effects on the structural parameters of the traditional PCB Rogowski coil. Therefore, the traditional PCB Rogowski coil is also not suitable for integration into the power module. Summary of the invention

[0005] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a switching current measurement method integrated into a power module, integrate the Rogowski coil into the power module, and connect the output end of the Rogowski coil to the processing circuit outside the power module, aiming to solve the problem of wide bandwidth of the existing Rogowski coil and the difficulty in integrating the current sensor. The traditional Rogowski coil is wound on a non-magnetic frame, and there are problems such as uneven winding and large volume. In this application, two Rogowski coils are used to form a differential Rogowski coil, which can well solve the problem of uneven winding, and it is small in size, compact in structure and easy to integrate, which improves the anti-interference performance of the current sensor.

[0006] In order to achieve the above purpose, the technical solution of this application is:

[0007] A switch current measurement method integrated into a power module, the current sensor used in the method includes a Rogowski coil and a processing circuit; two Rogowski coils are integrated into the power module to form a differential Rogowski coil, the processing circuit is located outside the power module, the output ends of the two Rogowski coils are connected to the input end of the processing circuit, and the ground ends of the two Rogowski coils are connected to the ground end of the processing circuit;

[0008] The Rogowski coil is planarly etched on the copper layer on the DBC substrate of the internal packaging structure of the power module. For the power module whose copper layer on the DBC substrate itself has an island structure, two Rogowski coils are directly etched on the island structure; for the power module whose copper layer on the DBC substrate itself does not have an island structure, it is necessary to etch an island structure on the copper layer on the DBC substrate, and etch the Rogowski coil on the island structure; the Rogowski coil has no electrical connection with the copper layer on the DBC substrate, the current-carrying conductor of the measured switching current of the power module is located above the Rogowski coil and does not contact the Rogowski coil, and the two Rogowski coils are symmetrically located on both sides of the current-carrying conductor; when a changing current flows through the current-carrying conductor, an induced electromotive force is generated at the output end of the Rogowski coil, and the processing circuit is used to integrate the induced electromotive force to restore the measured switching current.

[0009] Furthermore, the processing circuit includes an integration circuit and a differential amplifier circuit, the integration circuit includes an improved low-pass filter circuit, an in-phase active integration circuit and a high-pass filter circuit; the improved low-pass filter circuit includes a capacitor C, an inductor L and resistors R1 and R2, the differential amplifier circuit includes an operational amplifier A1 and resistors R4 and R5, the in-phase active integration circuit includes an operational amplifier A2, a capacitor Cc and resistors R3 and R f , the high-pass filter circuit includes a resistor R h and capacitor C h ;

[0010] The output end of each Rogowski coil is connected to an improved low-pass filter circuit. The capacitor C, inductor L and resistor R2 of each improved low-pass filter circuit form a series branch. Each series branch is connected in parallel with the damping resistor of the respective Rogowski coil. One end of the two series branches is grounded. One end of the resistor R1 of each improved low-pass filter circuit is connected to the damping resistor of the respective Rogowski coil. The other end of the resistor R1 of one of the improved low-pass filter circuits is connected to the other end of the corresponding series branch and then connected to the in-phase input end of the operational amplifier A1 through a resistor R4. The other end of the resistor R1 of the improved low-pass filter circuit is connected to the other end of the corresponding series branch and then connected to the in-phase input end of the operational amplifier A1 through a resistor R4. The other end of the resistor R1 of the improved low-pass filter circuit is connected to the other end of the corresponding series branch and then connected to the inverting input end of the operational amplifier A1 through another resistor R4; a resistor R5 is connected between the non-inverting input end and the output end of the operational amplifier A1, one end of another resistor R5 is connected to the inverting input end of the operational amplifier A1, and the other end is grounded; the output end of the operational amplifier A1 is connected to the non-inverting input end of the operational amplifier A2, the inverting input end of the operational amplifier A2 is connected to one end of the resistor R3, and the other end of the resistor R3 is grounded; the capacitor Cc and the resistor R f A parallel branch is formed, one end of the parallel branch is connected to the resistor R3, and the other end is connected to the output end of the operational amplifier A2. The output end of the operational amplifier A2 is also connected to the capacitor C h One end of the capacitor C h The other end of the resistor R h Connect one end of the resistor R h The other end is grounded.

[0011] Furthermore, the method also includes the following contents:

[0012] 1. Since the measurement bandwidth of the current sensor should be 3 to 5 times the minimum bandwidth of the power module, that is, the first resonant frequency of the Rogowski coil should be 3 to 5 times the minimum bandwidth of the power module, the structural parameters of the Rogowski coil are designed according to the minimum bandwidth of the power module;

[0013] The first resonant frequency f of the Rogowski coil n for:

[0014]

[0015] In the formula, R0, L0, and C0 are the parasitic resistance, parasitic inductance, and parasitic capacitance of the Rogowski coil respectively, and R d is the damping resistance of the Rogowski coil;

[0016] The expressions of the parasitic resistance R0 and parasitic inductance L0 of the Rogowski coil of this method are:

[0017]

[0018]

[0019]

[0020] Where ρ represents the wire resistivity of the Rogowski coil, L c represents the total length of the wire of the Rogowski coil, w c 、h c They represent the wire width and thickness of the Rogowski coil, μ0 represents the vacuum permeability, and L coil,n ,d coil,n They represent the length and width of the nth turn of the Rogowski coil, respectively, and N represents the total number of turns of the Rogowski coil;

[0021] In summary, the structural parameters include the total length L of the wire of the Rogowski coil c , the wire width w of the Rogowski coil c , the wire thickness of the Rogowski coil h c , the length of the n-th Rogowski coil L coil,n and the width d of the nth turn of the Rogowski coil coil,n ;

[0022] 2. According to the structural parameters of the Rogowski coil, the Rogowski coil is etched on the copper layer on the DBC substrate;

[0023] 3. Determine the value of each component in the integration circuit;

[0024] The corner frequency of the high-pass filter circuit is:

[0025]

[0026] The low-frequency corner frequency f2 and high-frequency corner frequency f3 of the in-phase active integrator circuit are:

[0027]

[0028]

[0029] The resonant frequency f of the improved low-pass filter circuit cs and damping coefficient ξ2 are:

[0030]

[0031]

[0032] The low-frequency corner frequency f4 of the improved low-pass filter circuit is:

[0033]

[0034] In summary, in order to meet the integration requirements of the integration circuit, the values ​​of each component in the integration circuit are determined according to formula (21);

[0035]

[0036] Where ξ1 is the damping coefficient of the Rogowski coil, and its expression is:

[0037]

[0038] 4. Calculate the induced electromotive force of the differential Rogowski coil by formula (24), then integrate the induced electromotive force of the differential Rogowski coil to obtain the switching current, thus completing the measurement of the switching current of the power module;

[0039]

[0040] Where v'(t) represents the induced electromotive force of the differential Rogowski coil, i(t) represents the expression of the current flowing through the current-carrying conductor in the time domain t, M0 represents the mutual inductance coefficient between the differential Rogowski coil and the current-carrying conductor, M0 = M a +M b , M a 、M b are the mutual inductance coefficients between the two Rogowski coils and the current-carrying conductor, respectively, and the expression is:

[0041]

[0042] Where M n It represents the mutual inductance between the nth turn of Rogowski coil and the current-carrying conductor.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The present application method provides a new idea for integrating the current sensor into the power module. The Rogowski coil can be integrated into the power module by only changing the partial structural layout without changing the existing packaging structure of the power module. It has the characteristics of compact structure and small size. It can measure the switching current of the power module while meeting the high power density of modern power electronic equipment. Compared with the existing integration technology, it has been greatly improved in terms of universality, difficulty and accuracy. It has also made certain improvements in the processing circuit. The differential amplifier circuit is inserted into the integration circuit to form a complete differential structure with the Rogowski coil. The integration circuit reduces the droop effect while increasing the measurement bandwidth of the current sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is the measurement principle diagram of the traditional Rogowski coil current sensor;

[0046] Figure 2 It is the overall flow chart of the method of the present invention;

[0047] Figure 3It is the internal packaging structure diagram of the power module;

[0048] Figure 4 It is a measurement principle diagram of the current sensor of the present invention;

[0049] Figure 5 It is a schematic diagram of the structural parameters of the Rogowski coil of the present invention;

[0050] Figure 6 is a connection diagram of a differential Rogowski coil and a processing circuit of the present invention;

[0051] Figure 7 is an equivalent circuit diagram of the Rogowski coil of the present invention;

[0052] Figure 8 is the overall circuit diagram of the present invention;

[0053] Fig. 9 is an integration circuit diagram of the present invention;

[0054] FIG10( a ) is an amplitude-frequency characteristic curve of the high-pass filter circuit of the present invention;

[0055] FIG10( b ) is an amplitude-frequency characteristic curve of the in-phase active integration circuit of the present invention;

[0056] FIG10( c ) is an amplitude-frequency characteristic curve of the improved low-pass filter circuit of the present invention;

[0057] FIG10( d ) is an amplitude-frequency characteristic curve of the integration circuit of the present invention;

[0058] Fig.11 is the amplitude-frequency characteristic curve of the current sensor of the present invention;

[0059] Fig.12 It is the amplitude-frequency characteristic curve of the traditional Rogowski coil current sensor. DETAILED DESCRIPTION

[0060] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present application is not limited thereto.

[0061] Figure 3 It is the internal packaging structure of the power module, including a base plate, a DBC substrate and a chip. The DBC substrate is composed of an upper copper layer, a ceramic substrate and a lower copper layer. The DBC substrate is soldered to the base plate through a DBC solder layer, and the chip is soldered to the upper copper layer through a chip solder layer. An island structure is generally provided on the upper copper layer of the DBC substrate. The power module can be an IGBT power module, a SiCMOSFET power module or a SiC JFET power module, etc.

[0062] The present invention is a switch current measurement method integrated into a power module, such as Figure 4 As shown, the current sensor used in the method consists of two parts: a Rogowski coil and a processing circuit. The two Rogowski coils are integrated inside the power module to form a differential Rogowski coil. The processing circuit is located outside the power module. The output ends of the two Rogowski coils are respectively connected to their respective measurement terminals through bonding wires, and the measurement terminals are connected to the input end of the processing circuit. The ground ends of the two Rogowski coils are respectively connected to their respective grounded measurement terminals through bonding wires, and the grounded measurement terminals are connected to the ground end of the processing circuit.

[0063] The principle of using Rogowski coil to measure the switching current of power module is as follows:

[0064] According to Ampere's circuit law, when a changing current flows through a current-carrying conductor, the magnetic induction intensity B(t) generated by the changing current at any point in space is:

[0065]

[0066] In the formula, μ0 represents the vacuum magnetic permeability, i(t) represents the current flowing through the current-carrying conductor, and R represents the distance between the current-carrying conductor and the measuring point;

[0067] If there is a coil within the range R around the current-carrying conductor, the magnetic flux Φ(t) passing through the coil is:

[0068] Φ(t)=∫∫B(t)·dS (2)

[0069] Where S represents the area enclosed by the coil;

[0070] According to the law of electromagnetic induction, the induced electromotive force v(t) generated in the coil is:

[0071]

[0072] Let the mutual inductance Then the induced electromotive force v(t) of the coil is:

[0073]

[0074] In the formula, t represents the time domain;

[0075] It can be seen from formula (4) that the induced electromotive force of the coil is proportional to the differential of the measured current. Therefore, by integrating the induced electromotive force of the coil, the current flowing through the current-carrying conductor can be obtained. Therefore, the Rogowski coil can be used to measure the switching current of the power module.

[0076] Figure 7 The equivalent circuit diagram of the Rogowski coil is shown in Figure 2. The parasitic resistance R0, parasitic inductance L0 and parasitic capacitance C0 are connected in series, and the damping resistance R d In parallel with the parasitic capacitance C0, the damping resistor R dand parasitic capacitance C0 are grounded; the values ​​of parasitic resistance R0, parasitic inductance L0 and parasitic capacitance C0 are related to the structural parameters of the Rogowski coil, and the damping resistor R d It is used to adjust the damping coefficient of the Rogowski coil in order to achieve better impedance matching between the Rogowski coil and the integrating circuit.

[0077] Figure 8 , 9 They are respectively the structural diagrams of the processing circuit and the integration circuit. The processing circuit is composed of an integration circuit and a differential amplifier circuit. The integration circuit includes an improved low-pass filter circuit, a common-phase active integration circuit and a high-pass filter circuit. In order to form a complete differential structure with the differential Rogowski coil inside the power module, a differential amplifier circuit is inserted into the integration circuit of the processing circuit. In order to prevent the voltage peak generated by the Rogowski coil when the current is turned off from exceeding the use range of the operational amplifier after amplification, the improved low-pass filter circuit is located in front of the differential amplifier circuit, and the voltage peak is buffered by the capacitor of the low-pass filter circuit to protect the operational amplifier from exceeding the use range.

[0078] The improved low-pass filter circuit includes a capacitor C, an inductor L and resistors R1 and R2, a differential amplifier circuit includes an operational amplifier A1 and resistors R4 and R5, and a common-phase active integration circuit includes an operational amplifier A2, a capacitor Cc and resistors R3 and R f , the high-pass filter circuit includes a resistor R h and capacitor C h The output end of each Rogowski coil is connected to an improved low-pass filter circuit, and the capacitor C, inductor L and resistor R2 of each improved low-pass filter circuit form a series branch, and each series branch is connected to the damping resistor R of the respective Rogowski coil. d In parallel, one end of the two series branches is grounded, and one end of the resistor R1 of each improved low-pass filter circuit is connected to the damping resistor R of the respective Rogowski coil. d The other end of the resistor R1 of one improved low-pass filter circuit is connected to the other end of the corresponding series branch and then connected to the non-inverting input end of the operational amplifier A1 through a resistor R4. The other end of the resistor R1 of another improved low-pass filter circuit is connected to the other end of the corresponding series branch and then connected to the inverting input end of the operational amplifier A1 through another resistor R4. A resistor R5 is connected between the non-inverting input end and the output end of the operational amplifier A1. One end of another resistor R5 is connected to the inverting input end of the operational amplifier A1, and the other end is grounded. The output end of the operational amplifier A1 is connected to the non-inverting input end of the operational amplifier A2. The inverting input end of the operational amplifier A2 is connected to one end of the resistor R3, and the other end of the resistor R3 is grounded. The capacitor Cc and the resistor R fA parallel branch is formed, one end of the parallel branch is connected to the resistor R3, and the other end is connected to the output end of the operational amplifier A2. The output end of the operational amplifier A2 is also connected to the capacitor C h One end of the capacitor C h The other end of the resistor R h Connect one end of the resistor R h The other end is grounded; the inductor L is used to generate resonance at the first resonant frequency of the Rogowski coil, and the resistor R2 is used to adjust the improved low-pass filter circuit at its resonant frequency f cs The purpose is to increase the bandwidth of the current sensor and achieve more accurate impedance matching between the Rogowski coil and the integration circuit.

[0079] The method also includes the following:

[0080] 1. Design the structural parameters of the Rogowski coil according to the minimum bandwidth (BW) of the power module. To ensure the measurement accuracy, the measurement bandwidth of the current sensor should be 3 to 5 times the minimum bandwidth of the power module, so the first resonant frequency of the Rogowski coil should be 3 to 5 times the minimum bandwidth of the power module. The structural parameters include the total length L of the Rogowski coil wire. c , the wire width w of the Rogowski coil c , the wire thickness of the Rogowski coil h c , the length of the n-th Rogowski coil L coil,n and the width d of the nth turn of the Rogowski coil coil,n ;

[0081] Depend on Figure 7 It can be seen that the transfer function of the Rogowski coil equivalent circuit is:

[0082]

[0083] Where u(s) represents the induced voltage across the Rogowski coil, i(s) represents the current flowing through the current-carrying conductor, and s represents the frequency domain;

[0084] From formula (5), we can know that the first resonant frequency and damping coefficient of the Rogowski coil are:

[0085]

[0086]

[0087] It can be seen from equations (6) and (7) that the first resonant frequency and damping coefficient of the Rogowski coil are mainly related to its parasitic parameters; the expressions of the parasitic resistance R0 and parasitic inductance L0 of the Rogowski coil in this method are:

[0088]

[0089]

[0090]

[0091] Where ρ represents the wire resistivity of the Rogowski coil, L c represents the total length of the wire of the Rogowski coil, w c 、h c Respectively represent the wire width and thickness of the Rogowski coil, L coil,n ,d coil,n They represent the length and width of the nth turn of the Rogowski coil, respectively, and N represents the total number of turns of the Rogowski coil;

[0092] 2. According to the structural parameters of the Rogowski coil, the Rogowski coil is etched on the copper layer on the DBC substrate;

[0093] For the power module whose copper layer on the DBC substrate itself has an island structure, two Rogowski coils are directly etched on the island structure in a plane, and there is no electrical connection between the Rogowski coil and the copper layer on the DBC substrate; for the power module whose copper layer on the DBC substrate itself does not have an island structure, it is necessary to etch an island structure on the copper layer on the DBC substrate, and etch two Rogowski coils on the island structure, ensuring that there is no electrical connection between the Rogowski coil and the copper layer on the DBC substrate, and the position of the island structure should minimize the influence of the etching position of the Rogowski coil on the parasitic parameters of the power module;

[0094] The bonding wire is used as a current-carrying conductor of the measured switch current of the power module, the current-carrying conductor is located above the Rogowski coil and does not contact the Rogowski coil, and the two Rogowski coils are symmetrically located on both sides of the current-carrying conductor;

[0095] 3. Determine the value of each component in the integration circuit;

[0096] Formula (14) is the transfer function of the high-pass filter circuit, and its amplitude-frequency characteristic curve is shown in Figure 10(a);

[0097]

[0098] The corner frequency of the high-pass filter circuit is:

[0099]

[0100] Formula (13) is the transfer function of the in-phase active integration circuit, and its amplitude-frequency characteristic curve is shown in Figure 10(b);

[0101]

[0102] Since low-frequency gain may over-amplify low-frequency noise and saturate the active integrator, the resistor R fThe purpose of this resistor is to limit the low-frequency gain of the active integrator. Usually, the resistor R f The resistance of is much larger than that of resistor R3, so equation (13) can be simplified as:

[0103]

[0104] The low-frequency corner frequency f2 and high-frequency corner frequency f3 of the in-phase active integrator circuit are:

[0105]

[0106]

[0107] Formula (17) is the transfer function of the improved low-pass filter circuit, and its amplitude-frequency characteristic curve is shown in Figure 10(c);

[0108]

[0109] The resonant frequency f of the improved low-pass filter circuit cs and damping coefficient ξ2 are:

[0110]

[0111]

[0112] The low-frequency corner frequency f4 of the improved low-pass filter circuit is:

[0113]

[0114] In summary, in order to meet the integration requirements of the integration circuit, the design of the integration circuit must meet the following conditions. The complete amplitude-frequency characteristic curve of the integration circuit is shown in Figure 10(d);

[0115]

[0116] Determine the value of each component in the integration circuit according to formula (21);

[0117] 4. Measure the switching current of the power module;

[0118] Since the structural parameters of the two Rogowski coils are exactly the same, the mutual inductance coefficient between the two Rogowski coils and the current-carrying conductor is:

[0119]

[0120] Where M n represents the mutual inductance coefficient between the nth turn of the Rogowski coil and the current-carrying conductor, r is the distance between the current-carrying conductor and the outside of the Rogowski coil;

[0121] Therefore, the mutual inductance between the differential Rogowski coil and the current-carrying conductor is:

[0122] M0=M a +M b (twenty three)

[0123] Substitute equation (23) into equation (24) to calculate the induced electromotive force of the differential Rogowski coil. By integrating the induced electromotive force of the differential Rogowski coil, the switching current can be obtained, and the measurement of the switching current of the power module can be completed.

[0124] The expression of the induced electromotive force of the differential Rogowski coil is:

[0125]

[0126] Fig.11 , 12 are the amplitude-frequency characteristic curves of the current sensor of the present method and the traditional Rogowski coil current sensor respectively; Fig.11 It can be seen that when the Rogowski coil frequency is lower than the resonant frequency f of the improved low-pass filter circuit cs When the amplitude-frequency characteristic curve of the Rogowski coil shows a differential characteristic, it is higher than the resonant frequency f cs Later, due to the influence of parasitic parameters, the amplitude-frequency characteristic curve changes from differential characteristic to integral characteristic; according to the working principle of Rogowski coil, the measurement effect of Rogowski coil for switching current is poor under low frequency conditions, and serious droop effect will occur. In order to improve the low-frequency measurement effect of Rogowski coil, a high-pass filter circuit is added after the in-phase active integration circuit, which can change the frequency characteristic of the current sensor from 20dB / decade to 40dB / decade when it is below the low-frequency corner frequency, thereby improving the low-frequency performance of Rogowski coil current sensor. Fig.12 It can be seen that the bandwidth range of the traditional Rogowski coil current sensor is f L ~f cs In order to improve the measurement bandwidth of the current sensor, the Rogowski coil is combined with the resonant frequency f cs Then the differential characteristic is changed to an integral characteristic, so that the amplitude-frequency characteristic of the integrator is at the resonant frequency f cs After that, the integral characteristic is changed to the differential characteristic, so that the Rogowski coil and the integrator cooperate well, achieving the purpose of improving the measurement bandwidth. The bandwidth range of the current sensor of the present application is f L ~f H The improved bandwidth range is f cs ~f H ; In summary, the current sensor of the present application has significant improvements in low-frequency performance and measurement bandwidth compared with traditional Rogowski coil current sensors.

[0127] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A method for measuring a switch current integrated into a power module, wherein the current sensor used in the method comprises a Rogowski coil and a processing circuit; characterized in that: Two Rogowski coils are integrated inside the power module to form a differential Rogowski coil, the processing circuit is located outside the power module, the output ends of the two Rogowski coils are connected to the input end of the processing circuit, and the ground ends of the two Rogowski coils are connected to the ground end of the processing circuit; The Rogowski coil is planarly etched on the copper layer on the DBC substrate of the internal packaging structure of the power module. For a power module whose copper layer on the DBC substrate itself has an island structure, two Rogowski coils are directly etched on the island structure; for a power module whose copper layer on the DBC substrate itself does not have an island structure, it is necessary to etch an island structure on the copper layer on the DBC substrate, and etch the Rogowski coil on the island structure; the Rogowski coil has no electrical connection with the copper layer on the DBC substrate, the current-carrying conductor of the measured switching current of the power module is located above the Rogowski coil and does not contact the Rogowski coil, and the two Rogowski coils are symmetrically located on both sides of the current-carrying conductor; when a changing current flows through the current-carrying conductor, an induced electromotive force is generated at the output end of the Rogowski coil, and the processing circuit is used to integrate the induced electromotive force and restore the measured switching current; The processing circuit is composed of an integration circuit and a differential amplifier circuit, wherein the integration circuit includes an improved low-pass filter circuit, a common-phase active integration circuit and a high-pass filter circuit; in order to form a complete differential structure with the differential Rogowski coil inside the power module, a differential amplifier circuit is inserted into the integration circuit of the processing circuit; in order to prevent the voltage peak generated by the Rogowski coil when the current is turned off from exceeding the use range of the operational amplifier after amplification, the improved low-pass filter circuit is located in front of the differential amplifier circuit, and the voltage spike peak is buffered by the capacitor of the low-pass filter circuit to protect the operational amplifier from exceeding the use range.

2. The switch current measurement method integrated into the power module according to claim 1, characterized in that: The improved low-pass filter circuit includes a capacitor C, an inductor L and resistors R1 and R2, a differential amplifier circuit includes an operational amplifier A1 and resistors R4 and R5, and a common-phase active integration circuit includes an operational amplifier A2, a capacitor Cc and resistors R3 and R f , the high-pass filter circuit includes a resistor R h and capacitor C h ; The output end of each Rogowski coil is connected to an improved low-pass filter circuit. The capacitor C, inductor L and resistor R2 of each improved low-pass filter circuit form a series branch. Each series branch is connected in parallel with the damping resistor of the respective Rogowski coil. One end of the two series branches is grounded. One end of the resistor R1 of each improved low-pass filter circuit is connected to the damping resistor of the respective Rogowski coil. The other end of the resistor R1 of one of the improved low-pass filter circuits is connected to the other end of the corresponding series branch and then connected to the in-phase input end of the operational amplifier A1 through a resistor R4. The other end of the resistor R1 of the improved low-pass filter circuit is connected to the other end of the corresponding series branch and then connected to the in-phase input end of the operational amplifier A1 through a resistor R4. The other end of the resistor R1 of the improved low-pass filter circuit is connected to the other end of the corresponding series branch and then connected to the inverting input end of the operational amplifier A1 through another resistor R4; a resistor R5 is connected between the non-inverting input end and the output end of the operational amplifier A1, one end of another resistor R5 is connected to the inverting input end of the operational amplifier A1, and the other end is grounded; the output end of the operational amplifier A1 is connected to the non-inverting input end of the operational amplifier A2, the inverting input end of the operational amplifier A2 is connected to one end of the resistor R3, and the other end of the resistor R3 is grounded; the capacitor Cc and the resistor R f A parallel branch is formed, one end of the parallel branch is connected to the resistor R3, and the other end is connected to the output end of the operational amplifier A2. The output end of the operational amplifier A2 is also connected to the capacitor C h One end of the capacitor C h The other end of the resistor R h One end of the resistor R h The other end is grounded.

3. The switch current measurement method integrated into the power module according to claim 2, characterized in that: The method also includes the following:

1. Since the measurement bandwidth of the current sensor should be 3 to 5 times the minimum bandwidth of the power module, that is, the first resonant frequency of the Rogowski coil should be 3 to 5 times the minimum bandwidth of the power module, the structural parameters of the Rogowski coil are designed according to the minimum bandwidth of the power module; The first resonant frequency f of the Rogowski coil n for: In the formula, R0, L0, and C0 are the parasitic resistance, parasitic inductance, and parasitic capacitance of the Rogowski coil respectively, and R d is the damping resistance of the Rogowski coil; The expressions of the parasitic resistance R0 and parasitic inductance L0 of the Rogowski coil of this method are: Where ρ represents the wire resistivity of the Rogowski coil, L c represents the total length of the wire of the Rogowski coil, w c 、h c They represent the wire width and thickness of the Rogowski coil, μ0 represents the vacuum permeability, and L coil,n ,d coil,n They represent the length and width of the nth turn of the Rogowski coil, respectively, and N represents the total number of turns of the Rogowski coil; In summary, the structural parameters include the total length L of the wire of the Rogowski coil c , the wire width w of the Rogowski coil c , the wire thickness of the Rogowski coil h c , the length of the n-th Rogowski coil L coil,n and the width d of the nth turn of the Rogowski coil coil,n ; 2. According to the structural parameters of the Rogowski coil, the Rogowski coil is etched on the copper layer on the DBC substrate; 3. Determine the value of each component in the integration circuit; The corner frequency of the high-pass filter circuit is: The low-frequency corner frequency f2 and high-frequency corner frequency f3 of the in-phase active integrator circuit are: The resonant frequency f of the improved low-pass filter circuit cs and damping coefficient ξ2 are: The low-frequency corner frequency f4 of the improved low-pass filter circuit is: In summary, in order to meet the integration requirements of the integration circuit, the values ​​of each component in the integration circuit are determined according to formula (21); Where ξ1 is the damping coefficient of the Rogowski coil, and its expression is:

4. Calculate the induced electromotive force of the differential Rogowski coil by formula (24), then integrate the induced electromotive force of the differential Rogowski coil to obtain the switching current, thus completing the measurement of the switching current of the power module; Where v'(t) represents the induced electromotive force of the differential Rogowski coil, i(t) represents the expression of the current flowing through the current-carrying conductor in the time domain t, M0 represents the mutual inductance coefficient between the differential Rogowski coil and the current-carrying conductor, M0 = M a +M b , M a 、M b are the mutual inductance coefficients between the two Rogowski coils and the current-carrying conductor, respectively, and the expression is: Where M n It represents the mutual inductance between the nth turn of Rogowski coil and the current-carrying conductor.

4. The switch current measurement method integrated into a power module according to any one of claims 1 to 3, characterized in that: The power module is an IGBT power module, a SiC MOSFET power module or a SiC JFET power module.

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