DE112013005380T5 - SMD current measuring device and its use - Google Patents

Abstract

An SMD current measuring device comprises: a magnetic core; and has first (31) and second (43) windings wound around the first and second portions of the magnetic core, respectively. The majority of the first winding (31) is surrounded by an electrically insulating material that defines a first shell (3) that defines a through hole (33) for inserting the first portion of the magnetic core, and the device includes an electrically insulating support (44) ) around which the second coil (43) is wound and which defines a through hole (42) for inserting the second portion of the magnetic core, both through holes (33, 42) being aligned with each other. The use of the SMD current measuring device is for detecting an excess of electric current flowing through the first winding and accurately measuring the magnitude of the electric current.

Description

Technical area

The present invention generally relates, in a first aspect, to an SMD (Surface Mounting Device) current measuring device, i. a device designed to be disposed over a printed circuit board and welded by an SMD technique, comprising two windings wound around a magnetic core, and more particularly an SMD current measuring device formed such that it is a compact and small device that provides high efficiency among others by providing an electrically insulating barrier between the two windings so that they can be placed close to each other.

Second and third aspects of the invention relate to various uses of the SMD current measuring apparatus of the first aspect

Background of the invention

In the prior art, there are several devices related to electrical current sensing devices, some of which include current transformers, also referred to as gage transformers, for measuring electrical currents, such as those described in US Pat US 4,630,218 are disclosed.

Furthermore, it is well known that switching protection systems incorporating these types of current sensors are located in modern power supplies, such as the power supplies powered by a power line disclosed in US patent application Ser US 2012/236611 A1 are disclosed.

In applications such as inverters and DC / DC battery chargers for electric vehicles and hybrid vehicles (also known as HEV: "hybrid electric vehicles"), current sensors must occupy as little space as possible and support the largest possible amount of energy. In addition, for good switching management, digital controllers must be better than traditional PWM controllers and this control must be done by sampling the current flowing through the conductors at a very high frequency (between 70KHz and 200KHz).

Most sensors known in the art are, due to size constraints, difficult to use in applications requiring a surface mount sensor. The requirements of various international standards regarding distances between windings, distance between core and windings, etc. prevent the use of conventional devices for this purpose.

However, some current sensing devices suitable for SMD are known, as is the case with those disclosed in the subsequently cited patents. US patent US Pat. No. 7,622,910 B2 discloses an integrated current sensor device suitable for surface mounting comprising a magnetic core and first and second windings wound around first and second portions of the magnetic core, respectively.

US Pat. No. 7,622,910 B2 discloses that the core and its windings are properly insulated, but there is no particular structural arrangement of the elements (windings and core) either for achieving such insulation or for assembling it in the support layer of the integrated device, except by reference to FIGS integrated circuit "Sentron CSA-1V-SO", which is claimed to have been modified by inclusion in an AC inductor, thereby implicitly assuming that the insulation to the windings and the core through the carrier layer of the integrated circuit itself or another layered element added during its manufacture.

The use of an integrated circuit manufacturing method for manufacturing the device of US Pat. No. 7,622,910 B2 has many disadvantages, including those associated with the costs, limitations and complexity inherent in such methods. Likewise, the maximum electrical values an integrated current sensor device can withstand are lower as compared to a non-integrated device because of thermal, geometric and other limitations.

EP 1 105 893 B1 discloses an inductive component production process comprising forming a hot melt adhesive under pressure in a metal mold enclosing a magnetic core wound through one or more windings. In an embodiment, it is stated that the inductive component, which by EP 1 105 893 B1 is directly suitable for SMD by providing a form with blind holes into which the terminals of the winding or windings are placed.

There is no inter-insulation between the windings or between the windings and the magnetic core in EP 1 105 893 B1 disclosed, wherein the only forming process disclosed therein is carried out once the windings are wound around the core.

Description of the invention

It is an object of the present invention to provide an alternative to the prior art for the purpose of providing an SMD current measuring device which provides particular structural arrangements for its internal elements, i. h., for the magnetic core and windings, enabling their manufacture as a compact and small device that offers very high efficiency and meets the requirements of various international standards for insulation criteria, such as dielectric strength and / or physical design criteria such as creepage, clearance, clearance through the insulation.

• – einen Magnetkern;
• – eine erste Wicklung, die zumindest um einen ersten Abschnitt des Magnetkerns gewickelt ist; und
• – eine zweite Wicklung, die zumindest um einen zweiten Abschnitt des Magnetkerns gewickelt ist.

To this end, the present invention relates to an electrical SMD current measuring device, comprising:

• A magnetic core;
• A first winding wound around at least a first portion of the magnetic core; and
• A second winding wound around at least a second portion of the magnetic core.

In contrast to the current measuring devices disclosed in the prior art, in that proposed by the present invention, at least a portion of the first winding is surrounded (overmolded) with an electrically insulating material which defines a first envelope includes at least the portion of the first winding, wherein the first shell determines a through hole for insertion of a first part of the magnetic core and the SMD current measuring device comprises an electrically insulating support around which the second winding is wound and which has a through hole for insertion of a second Determined portion of the magnetic core, wherein the through holes of the first and second winding are aligned with each other.

The first shell provides an insulating solid barrier that physically separates the first winding from the second winding. This barrier provides a higher electrical insulation, which allows a reduction in the distance between both windings, since the electrical insulation between them is increased compared to a case that none of the windings is surrounded with an insulating material.

Thus, the present invention provides a current measuring device having an arrangement enabling the incorporation of a current measuring device with the dimensions of an SMD device while maintaining safety characteristics and correspondences with the parameters proposed by standards such as IEC-61558 and UL-1950 ,

Preferably, the magnetic core and the first and second windings form a current transformer, the first winding serving as the primary winding and the second winding being the secondary winding of the current transformer, although other implementations than a current transformer for current sensing in which the magnetic core and windings used in the apparatus of the invention are possible for less preferred embodiments.

In one embodiment, the electrically insulating support is attached to the first shell, i. that is, the electrically insulating substrate and the shell are two independent pieces which are fixed to each other, while in another embodiment, the electrically insulating substrate is formed integrally with the first shell, i. they are both designed as one piece.

The magnetic core has, in one embodiment, at least one magnetic elongate element comprising the first and second portions.

In one embodiment, although the first and second portions correspond to different portions of a one-piece magnetic elongated member, in another embodiment, the magnetic core is divided into first and second magnetic sub-cores, wherein the sub-cores comprise magnetic elongate components having free ends disposed within the aligned ones Through holes for forming the magnetic elongated member abut each other, wherein each of the magnetic elongated components corresponds to a first and second portion of the magnetic core.

Preferably, the magnetic core is releasably secured to the first shell of the first coil and to the electrically insulating support of the second coil by inserting its first and second portions through the aligned through holes.

In another embodiment, the SMD current sensor device of the present invention includes first and second support members, each supporting one of the magnetic elongated components at respective ends opposite the free ends.

The first and second support members in one embodiment are part of the first and second magnetic sub-cores, respectively, and are integrated with the corresponding magnetic elongate component to provide integral therewith form, which, when joined, form a closed magnetic circuit.

In a preferred embodiment, each of the magnetic integral elements is an E-shaped piece, wherein in a cross-sectional plane intersecting its three legs and in which the magnetic flux flows, the central leg has a width twice as wide as the width of each lateral one Leg, so that when both E-shaped pieces face each other and are placed in contact at the free ends of their respective arms / legs, they form a closed magnetic circuit, the magnetic flux density coming from the first / primary winding inside the central leg is generated by both side legs at half induction value returns.

In an alternative embodiment, the first and second support members are non-magnetic elements attached to the magnetic elongated components of the first and second magnetic sub-cores, respectively.

In a preferred embodiment, the first winding is one turn and the second winding is more than one turn. In particular, for applications in the HEV industry, the second winding consists of at least fifty turns.

The second winding is also insulated with an electrically insulating material. It can also be encapsulated in one embodiment.

The insulation or encapsulation are independent of each other, d. i.e., are performed in at least separate ways, and provide an increase in the physical barrier between the windings and the windings and the magnetic core, whereby the SMD current measuring device of the invention is able to withstand higher electrical currents, thereby preventing a possible occurrence of arcing is limited.

According to one embodiment, the magnetic core is formed with a manganese-zinc alloy or amorphous cobalt.

In one embodiment, the electrically insulating support of the second winding is a winding template about which the second winding is formed.

The winding template, in one embodiment, is made of a material comprising a liquid crystal polymer or other plastic materials compatible with an SMD soldering process, such as reflow or vapor phase soldering processes, i. h., high heat index plastics according to the IEC85 standard, and also meet the self-extinguishing criteria according to the UL94 standard.

In one embodiment, the first winding comprises copper, nickel, silver, gold and / or a tin alloy.

The principle of the current measuring device of the present invention is based in a preferred embodiment on the use of a measuring transformer. In this case, the electric current flowing through a conductor is not measured, but the measurement is performed on the magnetic field induced by the current in a core.

A second aspect of the invention relates to a use of the SMD current measuring apparatus of the first aspect for detecting an excess of electric current flowing through the first winding, for example, to prevent overheating.

In addition, apart from providing a current measuring device used for detecting an excess of electric current, the present invention can also be applied to current measurement. This type of measurement allows the measurement of very high currents without direct contact with them, since, when such contact occurs, associated devices should have a considerable volume.

Thus, a third aspect of the invention relates to use of the SMD current measuring device to accurately measure the magnitude of the electrical current flowing through the first winding and the use for reading, for example, in a control loop of associated switching power supplies.

Brief description of the drawings

The foregoing and other advantages and features will be better understood from the following detailed description of embodiments with reference to the accompanying drawings, which are to be considered by way of illustration and not of limitation, of which:

1 Fig. 12 is a perspective view showing the SMD current measuring apparatus of the first aspect of the invention in an embodiment;

2 a plan view of the device of 1 is;

3 a perspective, disassembled view of the device of the first aspect of the Invention for the same embodiment of 1 and 2 is;

4 in a perspective view some of the in 3 shown elements, in particular those containing the first and second winding;

5 the same elements as 4 but in a plan view shows where three aligned through holes for the insertion of the magnetic core are shown in dashed lines;

6 a cross-sectional view along the sectional plane line VI-VI of 5 is.

7 a cross-sectional view along the sectional plane line VII-VII of 5 is;

8th a cross-sectional view taken along the section plane VIII-VIII of 5 is; and

9 is a perspective view, all in 3 represented elements, with the exception of the cover 2 , when assembled shows.

Detailed description of several embodiments

• – einen Magnetkern, der in einen ersten und zweiten magnetischen Teilkern geteilt ist, umfassend entsprechende magnetische längliche Komponenten 511, 521;
• – eine erste Wicklung 31, die mit einem elektrisch isolierenden Material umgeben ist, das eine erste Hülle 3 bestimmt, die das meiste der ersten Wicklung 31 darin umschließt (wie in 6 erkennbar ist), mit Ausnahme der freien Enden 31a und 31b, wobei die erste Hülle 3, wie in 6 dargestellt, ein Durchgangsloch 33 für das Einsetzen der magnetischen länglichen Komponente 511 bestimmt;
• – einen elektrisch isolierenden Träger 44; und
• – eine zweite Wicklung 43, die um den elektrisch isolierenden Träger 44 gewickelt ist und ein Durchgangsloch 42 (wie in 7 dargestellt) für das Einsetzen der magnetischen länglichen Komponente 521 bestimmt.

The attached figures show the various elements of the SMD current measuring device 1 of the invention in one embodiment, as predominantly in 3 shown, comprising:

• A magnetic core divided into first and second partial magnetic cores, comprising corresponding magnetic elongated components 511 . 521 ;
• - a first winding 31 which is surrounded by an electrically insulating material which is a first shell 3 That determines most of the first winding 31 encloses in it (as in 6 is recognizable), with the exception of the free ends 31a and 31b , where the first shell 3 , as in 6 shown, a through hole 33 for inserting the magnetic elongated component 511 certainly;
• - An electrically insulating support 44 ; and
• - a second winding 43 surrounding the electrically insulating support 44 is wound and a through hole 42 (as in 7 shown) for the insertion of the magnetic elongated component 521 certainly.

For the illustrated embodiment, there is also the first winding 31 from one turn, while the second winding 43 between 50 and 200 Can include turns. One skilled in the art can calculate the ratio of the number of turns of the first and second windings for other embodiments.

As in 8th shown are through holes 33 and 42 aligned with each other, so that when both magnetic elongated components 511 . 521 are inserted through their free ends in the aligned through holes 33 . 42 lie together. The magnetic elongated components 511 . 521 can on the inner contours of the through holes of the windings 33 and 42 be attached by a structural adhesive or epoxy adhesive.

For the case is a cover 2 provided, which, in this case by snap closure, the various elements of the current measuring device 1 , and in particular partial cores, holds together, as in 1 and 2 shown.

As in 3 shown has the SMD current measuring device 1 a first and second support element 51 . 52 , each with two parallel arms 51a - 51b ; 52a - 52b passing through a traverse 51c . 52c are connected, with which one of the magnetic elongated components 511 . 521 is connected at respective ends opposite the free ends, so that the magnetic elongated components 511 . 521 parallel and in the same direction as the parallel arms 51a - 51b ; 52a - 52b extend to the corresponding crossbar 51c ; 52c to form an E-shaped piece. Both E-shaped pieces are arranged facing each other and when joined together, as in 9 shown are the free ends of their respective arms 51a - 51b ; 52a - 52b and magnetic elongated components 511 . 521 in contact.

These E-shapes for the first and second carrier element 51 . 52 provide a particularly advantageous embodiment, when finally joined together, that is, the shape of the two E-shaped pieces which, once joined together, are more similar to the cubic or rectangular prism shape of the typical surface mount device. Thus, these E-forms additionally allow a symmetrical device 1 and the magnetic core is easily removable when needed for replacement.

In a preferred embodiment, the first 51 and second 52 Carrier element part of the first and second magnetic part of the core and are with the corresponding magnetic elongated component 511 . 521 formed integrally and form the corresponding magnetic one-piece elements with these, which are each an E-shaped piece, which, as in 3 represented, a central leg 511 . 521 having a width Wc which is twice as wide as the width Ws of each side leg 51a . 51b . 52a . 52b such that when both E-shaped pieces are arranged facing each other and at the free ends of their contact respective arms / legs, they form a closed magnetic circuit, the magnetic flux density coming from the first / primary winding 31 within the central leg is generated, the 511 and 521 is formed by both lateral legs, 51a and 52a such as 51b and 52b , returns at half induction value.

In another embodiment, the first one 51 and second 52 Carrier element non-magnetic elements attached to the magnetic elongated component 511 . 521 are attached to the first and second magnetic part of the core.

As in 3 can be seen, the present invention provides a single enclosure for each of the windings 31 . 43 so that there is a physical barrier between them that prevents arcing or loss. This is particularly relevant since the device of the present invention is preferably used in applications in the range of 100 to 1000V with an RMS current (up to 50A to capture / measure).

This single cladding contains the fully overmolded primary winding comprising an insulator having a dielectric strength of between 2 and 4 kV, a creepage distance of at least 5 mm to the secondary winding and the core, and thus meeting the requirements of standards such as IEC-61558 and UL. Fulfilled in 1950.

4 shows the device of 3 in detail, without the magnetic core and the cover 2 so that the details of the windings 31 . 43 and the associated elements, such as the first insulating sheath 3 and the electrically insulating support 44 or Windungsschablone, which consists in a particularly preferred embodiment of a liquid crystal polymer (also known as LCP for the English term "liquid crystal polymer"), phenol or other material with high temperature resistance and flame retardancy. This carrier 44 must be able to withstand continuous temperatures between about -40 ° C and + 155 ° C.

5 shows a plan view of the in 4 illustrated elements, with two of the five pins 41 (like the second and fourth row of five pins) with the free ends of the second or secondary winding 43 are connected (connection not shown), on which in use an output current proportional to the current passing through the first or primary winding 31 flows, according to the principle of electromagnetic induction is generated. The carrier 44 the secondary winding 43 is mechanical with the five pins 32 connected to provide better mechanical attachment, but these pins 32 have no direct electrical connection for the illustrated embodiment.

The first winding 31 is a flat metallic strip that, as in 1 to 9 shown, free ends 31a . 31b which are not encapsulated, outside the shell 3 and form two metallic pins for SMD application to be electrically connected by welding to respective traces of a circuit board so that current can flow therethrough.

6 is a cross-sectional view along the sectional plane line VI-VI of 5 and shows how the first winding 31 in the first shell 3 embedded, after a course with an omega shape or the like, such as an omega shape, which is generally used for determining a rectangular shape, for example, for a metal profile.

This Omega shape allows the surrounding magnetic elongated component 511 follows a course that is to be understood electromagnetically as a turn.

As in 5 and 6 illustrated, includes the first shell 3 two upper level walls 3a . 3b and between them a prominent central section 3c , which is the central area of the first winding 31 surrounds.

After merging, as in 9 shown, each of the two parallel arms 51a - 51b of the first carrier element 51 on one of the two upper flat walls 3a . 3b and on a corresponding adjacent side wall 3c1 . 3c2 of the projecting central section 3c supported, resulting in a total structural robustness of the device 1 contributes.

The primary winding is preferably provided to support DC currents of about 50 A RMS, and is therefore preferably selected to have a cross-section of about 3 × 0.4 mm ² with a material such as copper and nickel plating, tin alloy, silver or gold in that it can be well welded and has good electrical (ohmic resistance) and thermal performance (thermal conductivity).

In addition, the frequency operating range must be approximately between 10 kHz and 250 kHz to meet industrial requirements.

The metal strip, the first winding 31 is obtained by a conventional pressing and bending process and is usually made of stainless steel.

7 shows a cross-sectional view along the sectional plane line VII-VII of 5 that shows how the electrically insulating support 44 , also referred to as a winding template, the above-mentioned through hole 42 determines that with the through hole 33 is aligned.

7 and as well 3 . 4 and 5 show the electrically insulating support 44 which is attached to a carrier piece 4 attached or integrally formed with this, the two upper flat surfaces 4a . 4b has and between them a central arc section 4c with a central through hole 55 that with through holes 33 . 42 aligned, each of the two parallel arms 52a - 52b the second carrier element 52 on one of the two upper flat surfaces 4a . 4b and on a corresponding adjacent side wall 4c1 . 4c2 of the central arch section 4c is supported, with the same purpose, to an overall structural robustness of the device 1 contribute. This insulating carrier 44 becomes the execution of the second or secondary winding 43 used.

For the embodiment of 8th are the electrically insulating carrier 44 , the carrier piece 4 and the first shell 3 formed as a one-piece element, where corresponding through holes 55 . 42 and 33 form a single and common through hole.

A recess R1 is on the upper surface of the support piece 4 shaped, which runs under the central arch, as a guide for the magnetic elongated component 521 to serve, thereby inserting into the through holes 55 and 42 is relieved. For the same purpose, another recess R2 is on the upper surface of the first shell 3 shaped as in 5 is shown.

Metallic pins 41 for SMD soldering are mechanical to the carrier piece 4 attached so that they extend as shown in all the accompanying figures. As stated above, at least two of the metallic pins are 41 with the free ends of the second winding 43 connected.

Claims (22)

SMD current measuring device, comprising: - a magnetic core; A first winding ( 31 ) wound around at least a first portion of the magnetic core; and a second winding ( 43 ) wound around at least a second portion of the magnetic core; characterized in that at least a portion of the first winding ( 31 ) is surrounded by an electrically insulating material having a first shell ( 3 ) determines at least the region of the first winding ( 31 ), the first envelope ( 3 ) a through hole ( 33 ) for insertion of the first portion of the magnetic core, and that the SMD current measuring device an electrically insulating support ( 44 ), around which the second winding ( 43 ) is wound, and the one through hole ( 42 ) for insertion of the second portion of the magnetic core, wherein the through holes ( 33 . 42 ) the first ( 31 ) and second ( 43 ) Winding are aligned with each other. SMD current measuring device according to claim 1, wherein the electrically insulating support ( 44 ) on the first shell ( 3 ) is attached or formed integrally therewith. The SMD current measuring device according to claim 1 or 2, wherein the magnetic core has at least one magnetic elongated member including the first and second portions. An SMD current measuring device according to claim 3, wherein said magnetic core is divided into first and second partial magnetic core comprising magnetic elongated components ( 511 . 521 ) having free ends extending in the aligned through holes ( 33 . 42 ) to form the magnetic elongated member, the magnetic elongated components ( 511 . 521 ) correspond to the first and the second portion of the magnetic core. SMD current measuring device according to claim 4, comprising a first and a second carrier element ( 51 . 52 ), each of which is one of the magnetic elongated components ( 511 . 521 ) at ends opposite the free ends. SMD current measuring device according to claim 5, wherein the first ( 51 ) and second ( 52 ) Carrier element are part of the first or second magnetic partial core and with the corresponding magnetic elongated component ( 511 . 521 ) are integrally formed. SMD current measuring device according to claim 5, wherein the first ( 51 ) and second ( 52 ) Carrier element are non-magnetic elements attached to the magnetic elongated components ( 511 . 521 ) of the first and second magnetic sub-core are attached. An SMD current measuring device according to claim 6 or 7, wherein each of said first ( 51 ) and second ( 52 ) Carrier element two parallel arms ( 51a - 51b ; 52a - 52b ), which by a Traverse ( 51c ; 52c ), wherein the magnetic elongated component ( 511 . 521 ) with the crossbeam ( 51c ; 52c ) is connected so that they are parallel and in the same direction as the parallel arms ( 51a - 51b ; 52a - 52b ) extends to an E-shaped Piece with them and with the Traverse ( 51c ; 52c ) are formed, wherein both E-shaped pieces are arranged facing each other and at the free ends of their respective arms ( 51a - 51b ; 52a - 52b ) and magnetic elongated components ( 511 . 521 ) stay in contact. An SMD current measuring device according to claim 8, wherein the first envelope ( 3 ) at least two upper planar walls ( 3a . 3b ) and between them a prominent central section ( 3c ), at least part of the first winding ( 31 ), each of the two parallel arms ( 51a - 51b ) of the first carrier element ( 51 ) on one of the at least two upper planar walls ( 3a . 3b ) and on a corresponding adjacent side wall ( 3c1 . 3c2 ) of the projecting central section ( 3c ) is supported. SMD current measuring device according to claim 9, wherein the electrically insulating support ( 44 ) on a carrier piece ( 4 ) is attached or integrated with the at least two upper planar surfaces ( 4a . 4b ) and between these a central arc section ( 4c ) with a central through hole ( 55 ), wherein the central through hole ( 55 ) with the through holes ( 33 . 42 ), each of the two parallel arms ( 52a - 52b ) of the second carrier element ( 52 ) on one of the at least two upper planar surfaces ( 4a . 4b ) and on a corresponding adjacent side wall ( 4c1 . 4c2 ) of the central arc section ( 4c ) is supported. SMD current measuring device according to claim 10, comprising metallic pins ( 41 ) for SMD soldering, wherein at least a part of the metallic pins ( 41 ) electrically with at least the free ends of the second winding ( 43 ) and mechanically connected to the support piece ( 4 ) is attached. SMD current measuring device according to one of the preceding claims, wherein the free ends ( 31a . 31b ) of the first winding ( 31 ) are not surrounded by the electrically insulating material, outside the envelope ( 3 ) are arranged and form two corresponding metallic pins for SMD soldering. SMD current measuring device according to claim 1, wherein the first winding ( 31 ) consists of one turn and the second winding ( 43 ) consists of more than one turn. SMD current measuring device according to one of the preceding claims, wherein the second winding ( 43 ) is also surrounded by an electrically insulating material. SMD current measuring device according to one of the preceding claims, wherein the magnetic core releasably attached to the first shell ( 3 ) of the first winding ( 31 ) and on the electrically insulating support ( 44 ) of the second winding ( 43 by inserting its first and second sections through the respective aligned through holes ( 33 . 42 ) is attached. SMD current measuring device according to one of the preceding claims, wherein the magnetic core is formed with a manganese-zinc alloy and / or amorphous cobalt. SMD current measuring device according to claim 1, wherein the electrically insulating support ( 44 ) of the second winding ( 43 ) is a winding template. The SMD current measuring device according to claim 17, wherein the winding template is made of a material comprising a liquid crystal polymer. SMD current measuring device according to one of the preceding claims, wherein the first winding ( 31 ) Comprises nickel, silver, gold and / or a tin alloy. SMD current measuring device according to one of the preceding claims, wherein the magnetic core and the first ( 31 ) and second ( 43 ) Winding form a current transformer. Use of the SMD current measuring device according to one of the preceding claims, for detecting an excess of an electric current flowing through the first winding. Use of the SMD current measuring device according to any one of claims 1 to 20 for accurately measuring the magnitude of the electric current flowing through the first winding.

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