阅读说明：本技术 使用电隔离并集成在印刷电路板上的感测电流瞬时变化率的传感器 (Sensor for sensing instantaneous rate of change of current using galvanic isolation and integration on printed circuit board ) 是由 诺伯特·拉蒂格 于 2019-01-31 设计创作，主要内容包括：本发明涉及一种感测电流变化率的传感器,用以保护具有功率层和测量层的功率模块中的桥臂,所述传感器包括线圈和至少三个导体(C1,C2,Cp)。每个所述导体的一端连接到公共节点,同时每个所述导体的另一端分别用作电端子。所述至少三个导体包含在同一平面内,称为主平面,同时每个所述导体都有一个垂直于所述主平面的对称平面,每个所述对称平面都穿过所述公共节点及相应的端子。第一导体和第二导体相同并相对于第三导体对称放置,以及至少一对线圈相对于所述对称平面对称放置。(The invention relates to a sensor for sensing the rate of change of a current for protecting a bridge arm in a power module having a power layer and a measurement layer, said sensor comprising a coil and at least three conductors (C1, C2, Cp). One end of each of the conductors is connected to a common node, while the other end of each of the conductors respectively serves as an electrical terminal. The at least three conductors are contained in a common plane, called the main plane, while each of the conductors has a plane of symmetry perpendicular to the main plane, each of the planes of symmetry passing through the common node and the corresponding terminal. The first and second conductors are identical and symmetrically disposed with respect to the third conductor, and at least one pair of coils is symmetrically disposed with respect to the plane of symmetry.)

1. A sensor for sensing rate of change of current for protecting a leg in a power module having a power layer and a measurement layer, the sensor comprising a coil and at least three conductors (C1, C2, Cp), characterized in that:

one end of each of the conductors is connected to a common node (N);

the other end of each of said conductors respectively serving as an electric terminal (T1, T2, Tp);

said at least three conductors are contained in a same plane, called main plane (P);

each of said conductors (C1, C2, Cp) having a plane of symmetry (P1, P2, Pp) perpendicular to said main plane, each of said planes of symmetry passing through said common node (N) and the respective said electrical terminal (T1, T2, Tp);

the first conductor (C1) and the second conductor (C2) are identical and symmetrically placed with respect to the third conductor (Cp);

at least one pair of coils (10, 11 and/or 20, 21 and/or 30, 31) is placed symmetrically with respect to said symmetry plane (P1, P2, Pp).

2. The sensor for sensing rate of change of current of claim 1, wherein the first conductor (C1) and the second conductor (C2) are aligned and a distance between the respective electrical terminals (T1, T2) is minimal.

3. Sensor for sensing the rate of change of current according to any one of the preceding claims, characterized in that each coil of said third conductor (Cp) consists of one of the coils of said first conductor or one of the coils of said second conductor.

4. A sensor for sensing the rate of change of current according to any preceding claim, wherein the conductors are rectilinear planar.

5. The sensor for sensing rate of change of current of any preceding claim, wherein the conductor is multi-layered and/or striped.

6. A sensor for sensing the rate of change of current according to any preceding claim, in which the conductor has a "roebel bar" type topology.

7. Sensor for sensing the rate of change of current according to any one of the preceding claims, characterized in that the conductor (C1, C2, Cp) and the coil are formed on a multilayer printed circuit.

8. The sensor for sensing rate of change of current of any preceding claim, wherein the sensor comprises an electrostatic shield etched in a multilayer printed circuit and connected to a fixed potential between the power layer and the measurement layer.

9. A sensor for sensing the rate of change of current according to any preceding claim, in which the shield is etched to rationally guide the eddy currents.

10. A sensor for sensing the rate of change of current according to any preceding claim, in which all of the power layers are grouped together in the plane of a first layer and all of the measurement layers are grouped together in the plane of a second layer, the first layer being above or below the second layer.

Technical Field

The present invention relates to a sensor integrated in a printed circuit for sensing the instantaneous rate of change of a current. And more particularly to improvements in air transformer type sensors comprising a conductor and a coil. The sensor is particularly suitable for measuring and protecting the bridge arm current of a power module. The invention solves in particular the measurement of currents on nodes of a plurality of conductors with respect to the topology of an electronic circuit.

Background

The conversion of energy into electricity is rapidly changing. This power is driven by various innovations that occur in the fields of automobiles (hybrid and all-electric vehicles, charging stations), railways (increase in integration of train electronics, new and more energy efficient distribution stations), aviation (more electrified aircraft), space (arrival of digital technology in energy conversion), industry (improvement of energy efficiency … in factories that can be connected to the network without converters), energy (integration of renewable energy, super grid, micro grid).

New technologies in power modules such as Insulated Gate Bipolar Transistors (IGBTs) and wide gap semiconductors (e.g., gallium (GaN) and SiC) have increased the efficiency and level of integration of the "electrification function", enabling this new development of power electronics. On the other hand, the temperature inside these modules peaks (>125 ℃ C., up to 255 ℃ C.).

The power module consists of bridge arms whose switching times are very short due to the "wide band gap" components. Typically, 100A is turned off within 10 ns. Therefore, the design rules must be such that the parasitic inductance is reduced to limit the overvoltage and reduce the energy accumulated in the inductive elements of the switching circuit.

However, there may still be a fault in the arm and/or load that must be sensed before a forbidden overcurrent is reached. Therefore, there must be a current sensor capable of measuring a rapid instantaneous change in current immediately after the current is established, particularly in the legs of a static energy converter, to sense faults in advance; the sensor must naturally withstand these fault currents both thermally and mechanically. A fault must typically be sensed within a few hundred nanoseconds after it occurs and before a subsequent inhibited overcurrent builds up in order to be able to open the circuit of the arm within a delay of typically less than 1 mus. Such a current sensor cannot generate a parasitic inductance larger than several nH.

Current sensors from US7990132 are known to include a coil located within an integrated circuit chip and inductively coupled to a conductor located within a circuit package. The inductor senses the current in the conductor and provides a sensed signal to an integrator that provides a voltage representative of the current in the conductor.

The current sensing device of the known document US20060038552 comprises a first coil and a second coil in series with the first coil. The current sensing device is capable of sensing a current flowing through an object disposed between the first coil and the second coil or disposed near the first coil or the second coil. Each of the first and second coils has a first conductive pattern provided on a surface of the substrate, a second conductive pattern provided on a back surface of the substrate, and a connecting member connecting the first conductive pattern and the second conductive pattern. A semiconductor apparatus is also provided that includes a current sensing device for measuring a current flowing in a semiconductor element.

It will be apparent to those skilled in the art that the three-dimensional topology can be found, for example, by locating three end points on three axes of a three-dimensional orthogonal coordinate system. A field measurement can be made in each plane of the coordinate system, thereby benefiting from the relative immunity between the three currents at the three endpoints. However, this principle is very difficult to implement in practice and is also costly, especially with the constraint of optimizing the wire length required to minimize the parasitic inductance necessary.

The following problems need to be solved:

-simultaneously and individually measuring di/dt formed in the bridge arm and its load;

direct physical measurement of the rate of change of the current, so that the raw information can be processed quickly, with as little noise as possible;

-minimizing any parasitic inductance induced in the switching circuit;

-has a very short response time;

very compact, ideally integrated into a Printed Circuit Board (PCB) and compatible with surface mounted models of components;

-insensitivity to ultra-strong dV/dt;

-ensuring electrical isolation;

is immune to electromagnetic interference, in particular crosstalk generated by other bridge arms (for example in the case of full-or three-phase bridges) and other adjacent power supply circuits.

Disclosure of Invention

To achieve at least one of the above objects, the present invention aims to provide a sensor for sensing a rate of change of a current, the sensor comprising a coil and at least three conductors (C1, C2, Cp). In addition, the sensor has the following characteristics:

-one end of each of said conductors is connected to a common node (N);

-the other end of each of said conductors is used as an electric terminal (T1, T2, Tp), respectively;

-said at least three conductors are contained in a same plane, called main plane (P);

-each of said conductors (C1, C2, Cp) has a plane of symmetry (P1, P2, Pp) perpendicular to said main plane, each of said planes of symmetry passing through said common node (N) and the respective said electric terminal (T1, T2, Tp);

-the first conductor (C1) and the second conductor (C2) are identical and symmetrically placed with respect to the third conductor (Cp);

-at least one pair of coils is placed symmetrically with respect to said symmetry plane (P1, P2, Pp).

According to other advantageous and non-limiting features of the invention, the following are employed, alone or in any technically feasible combination:

-at least two planes of symmetry overlap;

-the first and second conductors are aligned and the distance between the respective terminals is minimal;

one of the coils of the third conductor is identical to one of the coils of the first conductor and the other coil of the third conductor is identical to one of the coils of the second conductor.

-the conductor is rectilinear planar;

-the conductor is multilayered or striped;

-the conductor (C1, C2, Cp) and the coil are formed on a multilayer printed circuit;

-the conductors (C1, C2, Cp) are multi-path and multi-layered, with a "roebel bar" topology commonly used in electrical machines to reduce eddy currents causing an increase of the internal resistance and inductance of high frequency conductors.

The role of the described topology is to position an equivalent virtual conductive layer with respect to the magnetic phenomenon in the region of the intermediate thickness of the conductor plane;

the sensor comprises an electrostatic shield etched in the multilayer printed circuit and connected to a fixed potential between the power layer and the measurement layer;

-etching the shield to rationally guide the eddy currents;

all power layers are grouped in the plane of a first layer and all measurement layers are grouped in the plane of a second layer, the first layer being above or below the second layer.

Drawings

Other features and advantages of the invention will be shown in the detailed description of the invention with reference to the drawings, in which:

FIG. 1 is a schematic diagram of a sensor for measuring the instantaneous rate of change of the sensed current of three currents;

fig. 2 is a schematic diagram of a sensor for measuring the instantaneous rate of change of the sensed currents of the bridge arm currents and the phase currents of the bridge converter topology;

fig. 3 is a schematic diagram of a sensor for measuring the instantaneous rate of change of the sensed current of the bridge arm current.

Detailed Description

To simplify the following description, the same reference numerals are used to denote the same rows of elements or elements performing the same function in different variants of the described device.

Examples of embodiments for the measurement of the three currents are as follows:

fig. 1 shows a first embodiment of a sensor for instantaneously measuring the instantaneous rate of change of three currents in a three-pole configuration. The sensor senses the rate of instantaneous change of current and comprises three conductors C1, C2 and Cp, one end of each conductor being connected to a common node N, while the other end of each conductor is defined as an electrical terminal T1, T2, Tp. Note that currents Ip, I1, and I2 flow through the three terminals Tp, T1, and T2.

All three conductors are contained in substantially the same plane, i.e. in the plane of the paper, called the principal plane. Furthermore, a symmetry plane Pp is defined for conductor Cp, which passes through the line between node N and terminal Tp and is perpendicular to the main plane. A pair of coils 30 and 31 is placed symmetrically with respect to plane Pp and each one on one side of conductor Cp. Likewise, symmetry planes P1 and P2 perpendicular to the main plane are defined for conductors C1 and C2, respectively, symmetry plane P1 passing through the line between node N and terminal T1, and symmetry plane P2 passing through the line between node N and terminal T2.

A pair of coils 10 and 11 are placed symmetrically with respect to plane P1 and each coil is located on one side of conductor C1, while a pair of coils 20 and 21 are placed symmetrically with respect to plane P2 and each coil is located on one side of conductor C2. In each pair of coils, one coil is wired in the left direction and the other coil is wired in the right direction, which are called: sp1D 10, Sp1G 11, Sp2D 20, Sp2G 21, SppD 30 and SppG 31.

For example, independently of the values of I1 and I2, a measurement of the instantaneous rate of change of the current Ip, independent of the values of I1 and I2, is obtained by the electromotive force delivered by a coil consisting of the following combination:

SppD tandem, SppG reverse tandem

Sp1G in inverse series, Sp1D in inverse series

Sp2G series, Sp2D series

Likewise, independently of the other two currents, the value of the instantaneous rate of change of I1 is obtained by a combination of:

SppD, SppG, in-line

Sp1G in reverse series, Sp1D in series

Sp2G series, Sp2D series

And rate of change for I2:

SppD, SppG, in-line

Sp1G series, Sp1D series

Sp2G series, Sp2D series

In the case of the present embodiment, a circular coil is given by way of illustration and not by way of limitation.

Examples of sensors that sense the instantaneous rate of change of current for the leg current and phase current are as follows:

fig. 2 shows a second embodiment of a sensor for measuring the instantaneous rate of change of current for the leg current and phase current. The current sensor comprises three conductors C1, C2, Cp. Conductors C1 and C2 are identical and are symmetrically and vertically aligned and positioned with respect to conductor Cp. One end of each conductor is connected to the common node N, while the other end of each conductor is defined as an electrical terminal T1, T2, Tp. Current I1 flows through terminal T1, current I2 flows through terminal T2, and current Ip flows through terminal Tp. By definition, current is defined as being input.

These three conductors are all contained in the same plane, i.e. in the plane of the paper, called the principal plane. Similarly to the first embodiment, three symmetry planes P1, P2 and Pp perpendicular to the main plane are also defined for each conductor C1, C2 and Cp. When conductors C1 and C2 are aligned, symmetry planes P1 and P2 coincide.

A pair of coils 43 and 44 is placed symmetrically with respect to plane Pp and each one on one side of conductor Cp. Conductors C1 and C2 have coils 41 and 42, respectively, on one side. By symmetry, the pair of coils 41 and 43 are placed symmetrically with respect to plane P1 and each on one side of conductor C1, while the pair of coils 42 and 44 are placed symmetrically with respect to plane P2 and each on one side of conductor C2.

By definition, the four coils are oriented in a direction perpendicular to the major plane, flowing in a forward direction on the page.

For purposes of illustration and not limitation, the coils are shown as square in shape. The coils may be rectangular, circular, etc., as long as symmetry is observed.

12 mutual inductances are introduced between the circuits C1, C2, Cp and each of the four coils, denoted Mxxy, where xx denotes the coil and y denotes the current. The value of the inductance is defined as positive.

By calculating the flux in each coil by superposition, the following equation can be written:

Phi1D＝-M1D1.I1+M1D2.I2-M1Dp.Ip

PhipD＝MpD1.I1-MpD2.I2-MpDp.Ip

PhipG＝MpG1.I1-MpG2.I2+MpGp.Ip

Phi2G＝-M2G1.I1+M2G2.I2+M2Gp.Ip

this set of equations can be simplified due to the symmetry of the structure.

In fact, due to the symmetry of the coil with respect to the plane Pp, the following properties are present:

MpGp＝MpDp＝Mpp

M2Gp＝M1Dp＝Mip

in fact, due to the symmetry of the coil with respect to the plane P1, the following properties are present:

M1D1＝MpD1＝Mii

M2G1＝MpG1＝Mij

in fact, due to the symmetry of the coil with respect to the plane P2, the following properties are present:

M2G2＝MpG2＝Mii

M1D2＝MpD2＝Mji

furthermore, due to the symmetry of the conductors C1 and C2 with respect to the plane Pp, the following properties are further present:

Mij＝Mji

finally, 4 equation sets with only 4 operational parameters are obtained and are marked as Mii, Mji, Mpp and Mip.

Namely:

Phi1D＝-Mii.I1+Mji.I2-Mip.Ip

PhipD＝+Mii.I1–Mji.I2-Mpp.Ip

PhipG＝+Mji.I1-Mii.I2+Mpp.Ip

Phi2G＝-Mji.I1+Mii.I2+Mip.Ip

the IMC common mode current and IMD differential mode current are defined as follows:

thus, I₁＝IMC+IMD

And, I₂＝IMC–IMD

The node law is: Ip-I1-I2

Thus, Ip ═ 2IMC

It follows that the phase currents are images of common mode currents, while the leg currents are images of differential mode currents.

It should also be remembered that the electromotive force at the coil terminals is proportional to the derivative of the collected flux with respect to time. Thus, a potential difference occurs at the terminals of the coil, proportional to the rate of change of the adjacent current at the start of the flux.

The flux equation is rewritten to show the two currents IMC and IMD:

Phi1D＝-Mii.(IMC+IMD)+Mji.(IMC-IMD)+2Mip.IMC

PhipD＝+Mii.(IMC+IMD)–Mji.(IMC-IMD)+2Mpp.IMC

PhipG＝+Mji.(IMC+IMD)–Mii.(IMC-IMD)-2Mpp.IMC

Phi2G＝-Mji.(IMC+IMD)+Mii.(IMC-IMD)-2Mip.IMC

the flux of an SpMC coil, consisting of the following combination, is now calculated:

sp1D series

-SppD in reverse tandem

-SppG tandem

Reverse cascade of-Sp 2G

This combination is advantageous because it consists of double differential pairs, thus specifically suppressing all the flux from the external field.

One complete flux was obtained, designated PhiMC, as follows:

PhiMC＝-Mii.(IMC+IMD)+Mji.(IMC-IMD)+2Mip.IMC-Mii.(IMC+IMD)+Mji.(IMC-IMD)-2Mpp.IMC+Mji.(IMC+IMD)–Mii.(IMC-IMD)-2Mpp.IMC+Mji.(IMC+IMD)–Mii.(IMC-IMD)+2Mip.IMC

PhiMC＝-2Mii.(IMC+IMD)+2Mji.(IMC-IMD)+4Mip.IMC+2Mji.(IMC+IMD)-2Mii.(IMC-IMD)-4Mpp.IMC)

PhiMC＝IMC.(-2Mii+2Mji+4Mip-4Mpp+2Mji-2Mii)+IMD.(-2Mii-2Mji+2Mji+2Mii)

PhiMC＝IMC.(-4Mii+4Mji+4Mip-4Mpp)

PhiMC＝2Ip.(-Mii+Mji+Mip-Mpp)

PhiMC does not depend on the differential mode current (IMD) which is an image of the arm current, but only on the common mode current (IMC) which is an image of the phase current. This topology thus allows the phase currents to be accessed independently of the leg currents.

The flux of the helix of the SpMD, consisting of the following combination, is now calculated:

sp1D series

-SppD in reverse tandem

-SppG in reverse tandem

-Sp2G series

This combination is advantageous because it consists of differential pairs, which are well resistant to the effects of external fields.

One complete flux was obtained, denoted PhiMD, as follows:

PhiMD＝-Mii.(IMC+IMD)+Mji.(IMC-IMD+2Mip.IMC-Mii.(IMC+IMD)+Mji.(IMC-IMD)-2Mpp.IMC-Mji.(IMC+IMD)+Mii.(IMC-IMD+2Mpp.IMC-Mji.(IMC+IMD)+Mii.(IMC-IMD)-2Mip.IMC

PhiMD＝+4(Mji+Mii).IMD

PhiMD＝+2(Mji+Mii).(I1-I2)

PhiMD does not depend on the common mode current (IMC), which is an image of the phase current, but only on the differential mode current (IMD), which is an image of the arm current. This topology thus allows the arm current to be accessed independently of the phase current.

Examples of sensors that sense the instantaneous rate of change of bridge arm current are as follows:

fig. 3 shows a third embodiment of a sensor that measures the instantaneous rate of change of leg current and phase current. The conductors are the same as those of the second embodiment. A pair of coils 51 and 52 is placed symmetrically with respect to planes P1, P2 and Pp, and each coil is located on one side of conductor Cp, respectively. In this example, only the phase current is measured, independent of the bridge arm current.

The following paragraphs describe several variations of the sensor for sensing the instantaneous rate of change of current based on the above-described primary structure.

First, consider a configuration that introduces very low parasitic inductance into the switching circuit.

If the phase current is considered to be Ip, the switching behavior of the bridge arm only involves the inductance between the terminals 1 and 2. This inductance value is preferred so that the distance between the nodes and the terminals 1 and 2 can be reduced. In this configuration, the distance between the terminal T1 and the terminal T2 is minimized to reduce inductance. Therefore, it is not possible to separate the currents I1 and I2. When the conductive tracks on the printed circuit board are preferably wide and short, while maintaining symmetry, low inductance values, typically less than 10nH, or even less than 5nH, 2nH, or even less than 1nH, are achieved.

The limb currents and phase currents are still available, although the possibility of independently measuring the two half-limb currents T1-Tp and T2-Tp is lost.

For another embodiment, a very short response time is required, typically less than 300ns or even less than 100 ns. In order to reduce the response time, the time constants due to skin and proximity effects should be kept to a minimum. For this purpose, the electrical conductors C1, C2 and Cp preferably serve as primary conductors, which are composed of a plurality of layers, each of which is insulated from the other. A multilayer PCB is a good example of implementing the main conductor.

Further, the conductors may be striped for each layer. Thus, primary conductors C1, C2, and Cp are multilayered and/or striped.

Furthermore, the conductors C1, C2 and Cp may be made in a roebel bar topology, which means that the bar-shaped electrical conductor is divided in particular into a plurality of parallel, mutually insulated and laminated sub-conductors. This topology allows the conductor to appear as a single planar conductor as a whole and greatly reduces the effects of eddy currents on the resistance and inductance values of the high frequency conductor.

In another aspect, the present invention provides a sensor for sensing the instantaneous rate of change of a dense current, ideally integrated in a printed circuit. Here, the main conductors C1, C2, and CP are generated by etching tracks on a Printed Circuit Board (PCB). To control the rules of symmetry, the sensor coils are also fabricated on the same PCB, with widely spaced layers.

As described above, the induced electromotive force (e.m.f) can be directly transferred using a plurality of sensor coils without performing post-processing. This will provide the coil with one layer to deliver an electromotive force proportional to the instantaneous rate of change of the phase current and another layer to deliver an image of the induced electromotive force of the instantaneous rate of change of the leg current. Conductors C1, C2, Cp and the windings are all implemented on a multi-layer PCB.

In another aspect, the present invention provides a current transient rate sensor that is compatible with a Surface Mounted Device (SMD) model.

All that is required is to locate all layers of the power PCB below the measurement layer. The power tracks are grouped substantially in the same plane, and the measurement tracks are grouped in one plane and another, the same parallel plane, arranged above or below.

In a particular aspect, the invention provides a current sensor that is immune to ultra-high dV/dt (typically greater than 10kV/μ s, or even greater than 100kV/1 μ s, or even greater than 1MV/μ s).

The voltage at the midpoint of the bridge arm is subject to an ultra high dV/dt with respect to the zero point of the potential (point free). Thus, current can be injected into the sensor electronics by capacitive effects. Ideally, these currents are common mode currents which are related to the variation of the common mode potential of the mid-point of the arms with respect to the zero providing the dc source for the bridge converter. Thus, the advantage of using differential measurements is to eliminate the effect of these currents on the measurement. However, injecting ultra-high currents in low-level electronic circuits still risks that the circuits may be damaged.

In order to reduce this risk, an electrostatic shield, for example of the faraday type, is used between the primary conductor and the measuring coil. Such a shield may be realized on the PCB by an additional copper layer. Whether to introduce a new time constant may be chosen in view of the generation of eddy currents. For this reason, this way of etching the shield layer enables the eddy currents that may be generated to be guided reasonably. Furthermore, in order to control the formation of eddy currents within the shield, the electrical conductivity of the shield must be controlled by the thickness of the shield or the use of striations in certain preferential directions. The electrostatic shield may be connected to a fixed potential between the power layer and the measurement layer to reasonably transfer parasitic currents.

The invention also relates to a sensor for sensing the instantaneous rate of change of current, which sensor provides electrical isolation, typically rated at an isolation voltage of 1kV or even 10kV, and a breakdown voltage of greater than 10kV, or even greater than 20kV, or even greater than 50 kV.

By using a material with a breakdown voltage corresponding to the desired target it is sufficient to control the distance between the power circuit and the measurement circuit. This is achieved in PCB technology by means of an insulating material, for example epoxy.

According to an embodiment, the invention relates to a sensor for sensing the instantaneous rate of change of a current, which is immune to electromagnetic interference, in particular to crosstalk generated by other bridge arms (for example in the case of a full-bridge or a three-phase bridge). This is achieved by a differential structure of the measuring coils, which suppresses all electromagnetic phenomena having a common mode between the two coils.