Printed circuit board containing shunt bridge

Abstract

A printed circuit board comprises: a first trace (44), a second trace (45), and at least one insulating layer (43) located between the first trace and the second trace. The printed circuit board further comprises a first through-assembly having at least one first metallized hole (47) and a second through-assembly having at least one second metallized hole (48). Each first metallized hole and each second metallized hole connect the first trace and the second trace by passing through the insulating layer. The first through-assembly and the second through-assembly respectively form a first branch and a second branch of a shunt bridge.

Description

[0001] The invention relates to the field of printed circuits comprising shunt bridges. Background of the Invention

[0003] Fluxgate current sensors utilize the properties of the magnetic material forming the core, whereby the core saturates from a certain level of magnetic excitation. Figure 1 , for increasing magnetic field H, the slope of the transfer function between magnetic field H and magnetic flux density B drops sharply from the so-called "saturation" value of the core. Figure 1 The saturation value corresponds to the range ΔH and ΔB.

[0004] Reference Figure 2 and 3 In a conventional fluxgate current sensor 1 for measuring a current Im flowing in a conductor, a square wave signal generator 2 applies a square wave excitation voltage Vex to the terminals of an excitation winding 3 wound around a magnetic core 4. The excitation current Iex flowing in the excitation winding 3 is measured by a measurement module 5. A peak detector 6 connected to the measurement module 5 provides two pieces of information: a saturation level and a difference between the peak currents of the excitation current Iex. The saturation level is used to servo-control the amplitude of the excitation voltage Vex. The difference between the peak currents of the excitation current Iex is used to estimate the current Im to be measured, and the difference acts via a voltage-to-current converter 7 to servo-control the amplitude of the demagnetization current, which flows in a demagnetization winding 8 and is used to compensate for the magnetic flux generated in the magnetic core 4 by the current Im to be measured.

[0005] Fluxgate current sensors are preferred in certain applications. This is particularly suitable for measuring currents flowing in cut-off components of the solid-state power controller (SSPC) type of user equipment, or for measuring currents flowing in energy converter components of the power electronic module (PEM) type connected to one phase of an electric machine. The main difficulties arise when the current to be measured Im is large.

[0006] The demagnetization current used to compensate for the magnetic flux generated by the current Im to be measured in the magnetic core 4 must also be very large. The value of the demagnetization current must be equal to the value of the current Im to be measured divided by the transformation ratio of the transformer, which has the conductor in which the current Im to be measured flows as its primary winding and the demagnetization winding 8 as its secondary winding.

[0007] However, the number of turns of the demagnetization winding 8 is limited by its size and the resulting inductance. The larger the inductance, the more limited the rate of change of the demagnetization current and thus the bandwidth of the fluxgate current sensor 1. Therefore, increasing the number of turns of the demagnetization winding 8 does not constitute a relevant solution.

[0008] Directly increasing the generated demagnetization current does not constitute a relevant solution either. In particular, such an increase would require the generation of a very large demagnetization voltage, which is difficult to achieve using standard components.

[0009] Purpose of the Invention

[0010] The object of the present invention is to solve the above-mentioned problems. SUMMARY OF THE INVENTION

[0012] To achieve the object, a printed circuit is provided, comprising: a first trace, a second trace, and at least one insulating layer extending between the first trace and the second trace, the printed circuit further comprising a first through-assembly having at least one first plated through-hole and a second through-assembly having at least one second plated through-hole, each first plated through-hole and each second plated through-hole connecting the first trace and the second trace together by extending through the insulating layer, the first through-assembly and the second through-assembly forming a first branch and a second branch of a shunt bridge, respectively.

[0013] In a printed circuit such as the printed circuit of the present invention, the electrical characteristics of the first plated through hole and the second plated through hole are preferably reproducible.Thereby, the ratio between the resistance of the first branch and the resistance of the second branch of the shunt bridge is known very accurately.

[0014] As an example, the shunt bridge thus makes it possible to reduce the main current that is desired to be measured to obtain a current to be measured that is reduced by a precisely known ratio relative to the main current. The main current is thus estimated based on the measurement of the reduced current to be measured.

[0015] Thus, by incorporating a shunt bridge into the fluxgate current sensor, the current to be measured is reduced, thereby reducing the demagnetization current required to compensate for the magnetic flux generated by the current to be measured in the magnetic core of the fluxgate current sensor.

[0016] There is also provided a fluxgate current sensor comprising the printed circuit as described above.

[0017] The present invention may be better understood in light of the following description of certain non-limiting embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] With reference to the accompanying drawings, in which:

[0020] · Figure 1 The transfer function between magnetic field and magnetic flux density is plotted;

[0021] · Figure 2 An existing fluxgate current sensor is shown;

[0022] · Figure 3 A curve of an excitation voltage and a curve of an excitation current for exciting a magnetic core of an existing fluxgate current sensor are shown;

[0023] · Figure 4 A novel fluxgate current sensor is shown;

[0024] · Figure 5 A shunt bridge is shown which is incorporated into the printed circuit of the invention and is used to measure the current to be measured.

[0025] · Figure 6 is a cross-sectional view of a printed circuit of the present invention incorporating a shunt bridge; and

[0026] · Figure 7 is with Figure 6 A similar view to that of , but from above.

[0027] Detailed description of the invention

[0028] Reference Figure 4 In this example, a fluxgate current sensor 10 is used to measure a current Im to be measured and flowing in a conductor 11 .

[0029] The fluxgate current sensor 10 includes a transformer 12 including a magnetic core 13, a primary winding and a secondary winding. The primary winding is a conductor 11. The magnetic core 13 extends around the conductor 11. The secondary winding is a measuring winding 14 wound around the magnetic core 13.

[0030] The fluxgate current sensor 10 includes a plurality of electronic components forming a digital portion 15 and an analog portion 16 .

[0031] The digital part 15 comprises a digital processor component, which is in particular a Field Programmable Gate Array (FPGA), but it could be some other component: a microcontroller, a processor Application Specific Integrated Circuit (ASIC) and so on.

[0032] The fluxgate current sensor 10 further comprises an acquisition circuit 17. The acquisition circuit 17 forms part of the analog part 16.

[0033] An acquisition circuit 17 is connected to the measuring winding 14 .

[0034] The acquisition circuit 17 includes a high-pass filter 19 and an analog-to-digital converter (ADC) 20 connected to the output of the high-pass filter 19 .

[0035] In this example, the ADC 20 is a 12-bit converter, the operation of which is clocked at a frequency Fech. In this example, Fech=100 Megahertz (MHz). The ADC 20 may naturally exhibit different characteristics.

[0036] The acquisition circuit 17 acquires the analog measurement voltage Ve from the terminals of the measurement winding 14 . The measurement voltage Ve is used as input for a high-pass filter 19 .

[0037] The generated voltage is used as input to an ADC 20 which generates a digital measurement signal Sm. The fluxgate current sensor 10 comprises a high frequency generator 22. The high frequency generator 22 is incorporated into the FPGA (wherein the term "incorporated" may be replaced by any of the following terms: programmed, implemented, provided, etc.).

[0038] The high frequency generator 22 generates a digital reference signal of a frequency f0, a digital reference signal of a frequency 2f0, and a digital reference signal of a frequency 3f0.

[0039] In this example, the digital reference signal at frequency f0 has the following form:

[0040] S1r=sin(ω0t).

[0041] In this example, the digital reference signal at frequency 2f0 has the following form:

[0042] S2r=cos(2ω0t).

[0043] In this example, the digital reference signal at frequency 3f0 has the following form:

[0044] S3r=sin(3ω0t).

[0045] The fluxgate current sensor 10 further comprises an excitation circuit 23. The excitation circuit 23 is implemented in the FPGA.

[0046] The excitation circuit 23 is connected to the high-frequency generator 22 .

[0047] The excitation circuit 23 includes a primary excitation circuit 24 and an excitation servo control circuit 25 .

[0048] The original excitation circuit 24 receives the digital reference signal of frequency f0 and the digital reference signal of frequency 3f0, and the original excitation circuit 24 generates a partial digital excitation signal of frequency f0 and a partial digital excitation signal of frequency 3f0 from these signals.

[0049] In this example, the partial digital excitation signal at frequency f0 has the following form:

[0050] S1p=k1·sin(ω0t).

[0051] In this example, the partial digital excitation signal at frequency 3f0 has the following form:

[0052] S3p=k2.sin(3ω0t). The original excitation circuit 24 adds the partial digital excitation signal of frequency f0 and the partial digital excitation signal of frequency 3f0 together to generate the original digital excitation signal. The original digital excitation signal has the following form:

[0053] Seb=S1p+S3p=k1·sin(ω0t)+k2·sin(3ω0t).

[0054] An excitation servo control circuit 25 is connected to the high-frequency generator 22 .

[0055] The excitation servo control circuit 25 receives the digital reference signal of the frequency 3f0, and the excitation servo control circuit 25 generates a digital demodulation signal of the frequency 3f0 from the digital reference signal of the frequency 3f0.

[0056] In this example, the digital demodulated signal at frequency 3f0 has the following form:

[0057] S3d = k3·sin(3ω0t).

[0058] The excitation servo control circuit 25 includes a first multiplier 27, a second multiplier 28, an integrator 29, and a first amplifier 30. The first amplifier 30 is connected to the output of the integrator 29.

[0059] The first multiplier 27 multiplies the digital measurement signal Sm by the digital demodulated signal of the frequency 3f0. The resulting signal is used as input to the integrator 29.

[0060] It should be observed that the first multiplier 27 and the integrator 29 act as a first synchronous demodulator.

[0061] The first amplifier 30 generates a digital error signal. The second multiplier 28 multiplies the original digital excitation signal Seb by the digital error signal to obtain a digital excitation signal. The digital excitation signal has the following form:

[0062] Se=k0·(k1·sin(ω0t)+k2·sin(3ω0t)).

[0063] The fluxgate current sensor 10 further includes a demagnetization servo control circuit 32. The demagnetization servo control circuit 32 is incorporated into the FPGA.

[0064] The demagnetization servo control circuit 32 is connected to the high frequency generator 22 .

[0065] The demagnetization servo control circuit 32 receives the digital reference signal of the frequency 2f0, and the demagnetization servo control circuit 32 generates a digital demodulation signal of the frequency 2f0 from the digital reference signal of the frequency 2f0.

[0066] In this example, the digital demodulated signal at frequency 2f0 has the following form:

[0067] S2d=k4·cos(2ω0t).

[0068] The demagnetization servo control circuit 32 includes a third multiplier 33, a low-pass filter 34, and a second amplifier 35. The second amplifier 35 is connected to the output of the low-pass filter 34.

[0069] The third multiplier 33 multiplies the digital measurement signal Sm by the digital demodulated signal of the frequency 2f0. The resulting signal is used as the input of the low-pass filter 34. The second amplifier 35 thus generates a signal as a digital mirror image of the current Im to be measured, which is also the digital demagnetization signal Sdm. The digital mirror signal or the digital demagnetization signal Sdm has the following form:

[0070] Sdm=k·Im.

[0071] It should be observed that the third multiplier 33 and the low-pass filter 34 act as a second synchronous demodulator.

[0072] The fluxgate current sensor 10 further comprises a summing circuit 36. The summing circuit 36 ​​is implemented in the FPGA.

[0073] The summing circuit 36 ​​sums the digital excitation signal Se and the digital demagnetization signal Sdm to obtain the digital injection signal Si. This gives:

[0074] Si=k0·(k1·sin(ω0t)+k2·sin(3ω0t))+k·Im.

[0075] The fluxgate current sensor 10 further comprises an injection circuit 37. The injection circuit 37 forms part of the analog part 16.

[0076] The injection circuit 37 is connected to the summing circuit 36 ​​and the measuring winding 14 .

[0077] The injection circuit 37 includes a digital-to-analog converter (DAC) 38 .

[0078] In this example, the DAC 38 is a 12-bit converter and the operation of the converter is clocked at a frequency Fech (Fech=100 MHz). The DAC 38 may naturally exhibit different characteristics.

[0079] The DAC 38 acquires the digital injection signal Si, generates an analog excitation current Ie from the digital injection signal Si, and injects the excitation current Ie into the measurement winding 14 .

[0080] The operation of the fluxgate current sensor 10 is described below.

[0081] The excitation circuit 23 generates a digital excitation signal Se, which is converted into an excitation current Ie and injected into the measurement winding 14 .

[0082] The measurement voltage Ve is acquired and subsequently digitized to generate a digital measurement signal Sm.

[0083] A signal which is a digital image of the current Im to be measured is obtained at the output of the second amplifier 35. This digital image signal is used to estimate the current Im to be measured.

[0084] The digital mirror signal is also a digital demagnetization signal Sdm, which is used to compensate for the magnetic flux generated by the current Im to be measured.

[0085] By means of the summing circuit 36 ​​and the parallel connection, the digital demagnetization signal Sdm and the digital excitation signal Se are easily added together. The excitation current is thus used to excite the magnetic core 13 and also to demagnetize the magnetic core 13. The demagnetization current is thus incorporated into the excitation current Ie.

[0086] Saturation of the magnetic core 13 causes asymmetry in the measurement voltage Ve, which is composed of the sum of the sin(ω0t) component of frequency f0 (corresponding to the fundamental wave) and the cos(2ω0t) component of frequency 2f0 (corresponding to the second harmonic component).

[0087] It should be observed that the amplitudes of the partial digital excitation signal of frequency f0 and the partial digital excitation signal of frequency 3f0 are set to obtain an excitation current Ie, in which the component of frequency 3f0 (or third harmonic component) is in phase with the component of frequency f0 (or fundamental wave).

[0088] The third harmonic component of the measured voltage Ve obtained after synchronous demodulation using the first synchronous demodulator is positive. In the case where the magnetic core 13 is saturated, the third harmonic component is attenuated more strongly than the fundamental wave, and after synchronous demodulation, the third harmonic component becomes negative because the third harmonic becomes anti-phase with the fundamental wave.

[0089] Thus, when the excitation current Ie makes the magnetic core 13 close to saturation, the ratio of the amplitudes of the first harmonic component and the third harmonic component of the measurement voltage Ve changes until the third harmonic component becomes zero, and thereafter until the phase of the third harmonic component is reversed. The operating point corresponding to the third harmonic component of the measurement voltage Ve becoming zero is thus the optimal operating point of the fluxgate current sensor 10. This optimal operating point corresponds to the plot of the transfer function Figure 1 Bend 9 in the curve.

[0090] A digital error signal is obtained at the output from the first amplifier 30 .

[0091] The digital error signal is used to servo-control the excitation current Ie. The servo control includes controlling the excitation current Ie so that the third harmonic component of the measurement voltage Ve is zero. The fluxgate current sensor 10 thus operates continuously at the optimal operating point. This is used to obtain the maximum gain with the asymmetry introduced by the current Im to be measured and detectable in the measurement voltage Ve. It should be observed that this servo control by synchronously demodulating the third harmonic component is relatively insensitive to external electromagnetic disturbances, because all signals with frequencies other than the frequency 3f0 generate intermodulation products with components filtered by the low-pass filter 34 connected to the output of the third multiplier 33. It can also be observed that the servo control does not need to be very fast, because the changes from external parameters (temperature, aging) are relatively slow.

[0092] Thus, the measuring winding 14 is used simultaneously to excite the magnetic core 13 , to control the excitation, to measure the current Im to be measured, and to compensate for the magnetic flux (demagnetization) generated in the magnetic core 13 by the current Im to be measured.

[0093] Combining the functions in a single measuring winding 14 serves to simplify the fluxgate current sensor 10 , reduce its cost and weight, and facilitate its manufacture.

[0094] It should also be observed that the system used to process the measurements is mainly digital: a single FPGA is used to perform the main part of the processing system.

[0095] Digitizing a processing system increases its reliability and robustness (particularly with regard to temperature), reduces its cost, facilitates its manufacture, and improves its industrial reproducibility.

[0096] The improvement in regulating the operating point obtained by the demodulation performed by the first synchronous demodulator also serves to obtain better noise immunity. Furthermore, the use of a synchronous demodulator makes it possible to operate at high frequencies, allowing a wide bandwidth of the current Im to be measured while retaining very good immunity to external electromagnetic disturbances.

[0097] The sensitivity of the fluxgate current sensor 10 is constant in the temperature range, since the measurement is always performed at the optimum operating point corresponding to the saturation bend 9. The accuracy of the fluxgate current sensor 10 is thus good over a large temperature range.

[0098] As mentioned above, the fluxgate current sensor 10 measures the current Im to be measured and flowing in the conductor 11 .

[0099] This situation does not cause any particular difficulty when the current Im to be measured is small (for example, less than 1 ampere (A)).

[0100] However, major difficulties arise when the currents to be measured are large.

[0101] The demagnetization current used to compensate for the magnetic flux generated by the measured current Im in the magnetic core 13 must also be very large. The amplitude of the demagnetization current needs to be equal to the amplitude of the measured current divided by the transformation ratio of the transformer 12, which is related to the characteristics of the primary winding and the secondary winding.

[0102] However, the number of turns of the measuring winding 14 is limited by its size and the resulting inductance. The larger the inductance, the more limited the rate of change of the demagnetization current (from the digital demagnetization signal Sdm), and thus the more limited the bandwidth of the fluxgate current sensor 10. Therefore, increasing the number of turns of the secondary winding is not an effective solution.

[0103] Increasing the demagnetization current is not an effective solution either. Specifically, this would involve generating a very large demagnetization voltage associated with a large demagnetization current, which is difficult to implement using standard components.

[0104] It should be observed that this problem is not specific to the fluxgate current sensor 10 as described above, but applies to all fluxgate current sensors (and in particular to those fluxgate current sensors comprising a winding dedicated only to demagnetization).

[0105] To solve this difficulty, a shunt bridge is used to reduce the amplitude of the current to be measured. Figures 5 to 7 The fluxgate current sensor 10 comprises a printed circuit 40 according to the invention, on which a plurality of electronic components forming the digital part 15 and the analog part 16 are mounted.

[0106] In this example, the printed circuit 40 of the present invention includes a first conductive layer 41, a second conductive layer 42, and an insulating layer 43. In this example, each of the first conductive layer 41 and the second conductive layer 42 extends on corresponding opposite faces of the printed circuit 40.

[0107] The first conductive layer 41 has a first track 44 and the second conductive layer 42 has a second track 45. An insulating layer 43 thus extends between the first track 44 and the second track 45.

[0108] Printed circuit 40 further includes a first through-assembly having at least one first plated through-hole 47 and a second through-assembly having at least one second plated through-hole 48. In this example and in particular, the first through-assembly has a plurality of first plated through-holes 47 and the second through-assembly has a plurality of second plated through-holes 48. In this example, both first plated through-holes 47 and second plated through-holes 48 have the same first diameter.

[0109] A "plated through hole" may also be referred to as a "through hole". A "plated through hole" may be made by any type of method. Specifically, a "plated through hole" may be made conductive by depositing a metallic material or any type of conductive material. A "plated through hole" may also be made conductive by inserting a tube or rivet made of metal or any type of conductor.

[0110] Each first plated through hole 47 and each second plated through hole 48 connects the first trace 44 and the second trace 45 together by extending through the insulating layer 43 .

[0111] The first through assembly and the second through assembly form a first branch 51 and a second branch 52 of the shunt bridge 53 , respectively.

[0112] Thus, in this example, the current Im to be measured is not actually the main current Ip having a value to be determined, but the current Im to be measured is obtained by shunting the main current Ip and is then used to estimate the value of the main current Ip. The main current Ip flows in the first track 44, in the first branch 51 and the second branch 52 of the shunt bridge 53, and in the second track 45.

[0113] In this example, it can thus be clearly seen that the above-mentioned conductor 11 carrying the current to be measured is constituted by the second feed-through assembly (or the second branch 52 ).

[0114] In this example, the main current Ip is equal to 10A.

[0115] The number of first plated through holes 47 in the first through assembly is nine times greater than the number of second plated through holes 48 in the second through assembly. The second resistance of the second branch 52 is thus nine times greater than the first resistance of the first branch 51 .

[0116] The current to be measured Im flowing in the second branch 52 of the shunt bridge 53 is equal to 1A, while the current flowing in the first branch 51 of the shunt bridge 53 is equal to 9A.

[0117] In this example, the reproducibility property of the electrical characteristics of a plurality of plated through holes of the same diameter adjacent to each other in the same printed circuit 40 is exploited.

[0118] The first resistance of the first branch 51 and the second resistance of the second branch 52 are not exactly known, but due to the reproducibility the ratio of these two resistances is known very accurately.

[0119] The first through-assembly and the second through-assembly are thus equivalent to two shunt resistors with a well-controlled ratio.

[0120] The ratio between the current to be measured Im and the main current Ip is thereby known very accurately. Measuring the current to be measured Im enables a very accurate estimation of the main current Ip, while reducing the main current to reduce the required demagnetization current.

[0121] The current Im to be measured is measured by using the transformer 12 mentioned above.

[0122] The transformer 12 comprises a printed circuit 40 , or more precisely, a portion of the printed circuit 40 , provided that the printed circuit also carries the digital part 15 and the analog part 16 .

[0123] The second through-assembly as described above is also referred to herein as a “primary through-assembly.” The second plated through-hole 48 is a “primary plated through-hole.”

[0124] Printed circuit 40 also includes a third through-assembly including at least one third plated through-hole 56 extending through insulating layer 43 and a fourth through-assembly including at least one fourth plated through-hole 57 extending through insulating layer 43. In this example and specifically, the third through-assembly includes a plurality of third plated through-holes 56 and the fourth through-assembly includes a plurality of fourth plated through-holes 57. In this example, third plated through-holes 56 and fourth plated through-holes 57 both have the same second diameter, which, for reasons of available space, is smaller than the first diameter of first plated through-holes 47 and second plated through-holes 48. The number of third plated through-holes 56 is equal to the number of fourth plated through-holes 57.

[0125] The third and fourth through-assemblies together form an assembly referred to herein as a “secondary through-assembly.” In the secondary through-assembly, third plated through hole 56 forms at least one, and specifically a plurality of, “first secondary plated through holes” 56 , and fourth plated through hole 57 forms at least one, and specifically a plurality of, “second secondary plated through holes” 57 .

[0126] The transformer 12 further comprises a magnetic core 13 . The magnetic core 13 extends along the thickness of the printed circuit 40 .

[0127] The core 13 has the shape of a tube with a rectangular inner and outer cross section. It should be observed that the core 13 may naturally have a different shape. The core 13 comprises a primary core part 60 and a secondary core part 61 .

[0128] The primary feed-through assembly extends inside the core 13 adjacent the primary core portion 60 .

[0129] The primary feed-through assembly thus forms part of the primary winding of the transformer 12 , which in this example has only one turn.

[0130] The first secondary plated through hole 56 extends inside the magnetic core 13, near the secondary magnetic core portion 61. The second secondary plated through hole 57 extends outside the magnetic core 13, near the secondary magnetic core portion 61.

[0131] It can be seen that the first secondary plated through hole 56 and the second secondary plated through hole 57 are connected together by a conductive element 65 (eg, but not necessarily, a trace) extending in the first conductive layer 41 and the second conductive layer 42 . Figure 7 Only two conductive elements 65 are shown.

[0132] The third through-assembly thus forms a first portion of a secondary winding of the transformer 12. The fourth through-assembly thus forms a second portion of a secondary winding of the transformer. The secondary through-assembly thus forms a portion of a secondary winding of the transformer 12.

[0133] The secondary winding has a plurality of turns, each turn including a first secondary plated through hole 56 , a second secondary plated through hole 57 , and a conductor element 65 .

[0134] It can be seen from this that the secondary winding of the transformer 12 is the above-mentioned measuring winding 14 .

[0135] The following describes how to manufacture the printed circuit 40 and the magnetic core 13 extending along the thickness of the printed circuit 40 .

[0136] The printed circuit 40 includes a first prepreg layer and a second prepreg layer (wherein "prepreg" is short for "pre-impregnated"). The first and second prepreg layers are not polymerized.

[0137] The magnetic core 13 includes a mixture of magnetic powder and a resin constituting a magnetic powder binder.

[0138] The magnetic powder is composed of a crystal structure, especially yttrium iron garnet (Y3Fe 15 O 12 ) is made.

[0139] The resin is epoxy resin.

[0140] The magnetic core 13 is deposited on the first prepreg layer by screen printing.

[0141] Thereafter, the magnetic core 13 is covered with the second prepreg layer.

[0142] The printed circuit 40 is then passed through an oven.

[0143] The printed circuit 40 is then drilled to create the plated through holes described above.

[0144] Alternatively, the magnetic core 13 may be manufactured by laser sintering using additive manufacturing techniques.

[0145] The magnetic powder is deposited on the first prepreg layer. Afterwards, a laser beam is used to coalesce the magnetic powder layer in predefined areas to form the magnetic core 13.

[0146] The magnetic core 13 is subsequently covered with a second prepreg layer.

[0147] Manufacturing the magnetic core 13 by laser sintering appears to be more efficient. Specifically, when manufacturing by screen printing, it is observed that as many air gaps will be found in the mixture of magnetic powder and resin as in the magnetic powder particles. These air gaps reduce the performance of the magnetic core 13. With laser sintering, the magnetic powder particles are melted, which avoids the generation of said air gaps.

[0148] Naturally, the invention is not limited to the embodiments described but covers any variant coming within the ambit of the invention as defined by the claims.

[0149] It is stated that the fluxgate current sensor comprises a digital part and an analog part, and that the ADC and DAC form part of the analog part. Naturally, it is possible to consider these components to be digital components, and it is even possible to consider these components being incorporated directly into an FPGA (or a microcontroller or some other component), in which case they will form part of the digital part.

[0150] It is stated above that each of the first conductive layer including the first traces and the second conductive layer including the second traces extends on respective opposite sides of the printed circuit. Naturally, the first conductive layer and the second conductive layer may be internal layers of the printed circuit, the layers being separated by one or more insulating layers.

[0151] Above, each through-assembly is described as including one or more plated through holes. Above, the plated through holes all pass through a single insulating layer. Naturally, the plated through holes may pass through multiple insulating layers, or even through one or more insulating layers and one or more conductive layers. Different through-assemblies may equally well pass through different layer stacks.

[0152] It is explained above that the secondary feed-through assembly includes at least one first secondary plated through hole and at least one second secondary plated through hole located on opposite sides of the secondary core portion of the magnetic core. Naturally, it is also possible to have the primary feed-through assembly include at least one first primary plated through hole and at least one second primary plated through hole located on opposite sides of the primary core portion of the magnetic core. It is also possible to have these two configurations coexist.

[0153] Naturally, the printed circuit and the shunt bridge of the invention can be used in any type of application requiring a shunt bridge: the invention is not in any way limited to fluxgate current sensors.

Claims

1. A printed circuit comprising: A printed circuit comprises a first trace (44), a second trace (45), and at least one insulating layer (43) extending between the first trace and the second trace, the printed circuit further comprising a first through-assembly having at least one first plated through-hole (47) and a second through-assembly having at least one second plated through-hole (48), each first plated through-hole and each second plated through-hole connecting the first trace and the second trace together by extending through the insulating layer, the first through-assembly and the second through-assembly forming a first branch (51) and a second branch (52) of a shunt bridge (53), respectively, the printed circuit further comprising a measuring device, the measuring device being arranged to measure a current to be measured (Im) flowing in the second branch (52), the measuring device being used to estimate a main current (Ip) flowing in the first trace (44) and the second trace (45) based on the current to be measured.

2. The printed circuit according to claim 1, characterized in that Each of the first trace and the second trace extends on respective opposing sides of the printed circuit (40).

3. The printed circuit according to claim 1, characterized in that The at least one first plated through hole (47) and the at least one second plated through hole (48) have a same first diameter.

4. The printed circuit according to claim 3, characterized in that The measuring device comprises a transformer (12), the second feed-through assembly forming part of a primary winding of the transformer (12).

5. The printed circuit according to claim 4, characterized in that Further included is a third feed-through assembly having at least one third plated through hole (56) extending through the insulating layer (43), the third feed-through assembly forming a first portion of a secondary winding of the transformer.

6. The printed circuit according to claim 5, characterized in that Further included is a fourth through-assembly having at least one fourth plated through-hole (57) extending through the insulating layer (43), the fourth through-assembly forming a second portion of the secondary winding of the transformer.

7. The printed circuit according to claim 6, characterized in that The at least one third plated through hole and the at least one fourth plated through hole have a same second diameter that is smaller than the first diameter.

8. The printed circuit according to claim 7, characterized in that The transformer comprises a magnetic core (13) extending along the thickness of the printed circuit (40).

9. The printed circuit according to claim 8, characterized in that The magnetic core includes a secondary magnetic core portion (61) extending between the third through-assembly and the fourth through-assembly.

10. A fluxgate current sensor comprising a printed circuit as claimed in any preceding claim.

Images