WO2025087502A1

WO2025087502A1 - Techniques for current sensing

Info

Publication number: WO2025087502A1
Application number: PCT/EP2023/079496
Authority: WO
Inventors: Sarai Malinal TORRES DELGADO; Fralett SUAREZ SANDOVAL
Original assignee: Huawei Digital Power Technologies Co., Ltd.
Priority date: 2023-10-23
Filing date: 2023-10-23
Publication date: 2025-05-01

Abstract

The disclosure relates to techniques for current sensing, in particular a current sensing apparatus comprising: at least three layers of which two are electrically conductive layers and one is an electrically insulating layer, the at least three layers being arranged above each other; the current trace (200) formed by a first electrically conductive layer of the at least three layers; and an embedded inductor (201a, 201b) formed by at least one second electrically conductive layer of the at least three layers. The embedded inductor comprises a first plurality of conductive turns (201a) that are wound along a first winding direction, and a second plurality of conductive turns (201b) that are wound along a second winding direction opposite to the first winding direction. The embedded inductor is configured to provide a sensing voltage indicative of a current (202) flowing through the current trace (200). The sensing voltage results from a superposition of voltages induced by a current (202) flowing through the current trace (200) in each of the two pluralities of conductive turns.

Description

TECHNIQUES FOR CURRENT SENSING

TECHNICAL FIELD

The disclosure relates to techniques for current sensing, in particular a current sensing apparatus or arrangement with an inductor for sensing a current. The disclosure further relates to a synchronization circuit using such current sensing apparatus or arrangement and corresponding methods for current sensing.

BACKGROUND

Nowadays the number of battery-powered electronic devices is increasing rapidly because they provide freedom of movement and portability. Power converters are used to charge or power such electronic devices. Conduction losses occurring internally in a rectifier diode of the power converter significantly contribute to the total losses of the power converter, especially in low output voltage applications. To reduce such losses, synchronous rectification can be applied, which implements a controllable electronic switching device of low resistance, usually a FET, to replace the rectifier diode. Synchronous rectification requires to control the switching device in such a way that the ON/OFF behavior of the rectifier diode can be emulated, to do so, the zero crossing of the AC (sinusoidal) current or that of the input voltage must be detected which can be achieved in various ways. Among these detection methods there are the ones that have low sensitivity, others unavoidably disturb the system by a direct electrical connection. The isolated detection methods with enough sensitivity are usually of considerable size in their implementation. Especially in compact electronic devices such as wearables and consumer electronics in general, it would be beneficial to have a non-invasive, non-disturbing detection solution with the minimum footprint possible.

SUMMARY

This disclosure provides a solution for a non-invasive and non-disturbing current detection with minimum footprint that can be applied in compact electronic devices such as wearables and consumer electronics.

The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures. The solution presented in this disclosure can be applied in a variety of power conversion systems. It is suited for synchronous power converters commonly found in highly efficient secondary power supplies such as the adapters that supply or charge the battery of electronic devices (e.g., laptops, smartphones, tablets, smart glasses, earphones, wearables, console remote controls, etc.), using either wired or wireless power transfer. This is in general a challenge because it requires to detect the zero crossing of the AC current, or well, that of the input voltage to control the switching device(s) in synchrony. Moreover, among the different detection methods there are the ones that have low sensitivity, others that somehow disturb the system, and the isolated ones with enough sensitivity are usually of considerable size in their implementation which is a big constrain in compact electronic devices such as consumer electronics in general. Wireless power applications pose an increase challenge for zero crossing detection since usually the synchronous device needs to switch with the same frequency than the wireless power link, which is usually done at high frequencies, meaning that the detection needs to be fast enough.

This disclosure presents a “doubly coupled” miniature embedded inductor for current sensing purposes, and ultimately for their implementation in a synchronous operation device. Fabrication and synchronization circuit and methods are also disclosed. Such “doubly coupled miniature embedded inductor for current sensing" comprises a multilayer arrangement of electrically conductive and isolating layers; at least one flat electrically conductive trace on a main plane, in which the source of current to detect flows; and a sensing inductor, substantially flat on a second plane, adjacent to the main plane and doubly magnetically coupled to the current trace(s). The inductor further comprises a number of turns of conductive material.

The “double coupling” can be achieved in two different ways (see Figures 2 and 3 described below):

In a first case (described below with respect to Figure 2), the miniature embedded inductor can include a first plurality of conductor windings wound in a plane connected to a second plurality of conductor windings wound in opposite direction, in the same plane. Both pluralities of windings couple to the current trace laying on the adjacent layer. The changing magnetic field induces an electric field, which results in the induced voltage. This induced voltage in both plurality of windings effectively adds up and causes a current to flow over the conducting path that the inductor provides.

In a second case (described below with respect to Figure 3), the miniature embedded inductor includes a plurality of windings wound approximately on a plane. The plurality of windings couple to two current traces with current flowing in opposite directions, laying on the adjacent layer. The voltages induced by the changing magnetic fields produced by both current traces into the plurality of conductor windings effectively add up.

The solution described in this disclosure can be used in power conversion systems, in particular in electrically isolated, synchronous systems, like a wireless power transfer system composed of at least one transmitter device and at least one receiver device. In order to have an efficient overall power conversion from the input of the transmitter device to the output of the receiver device, the involved power converters need to minimize losses. A way to minimize losses is to use a synchronous rectifier on the at least one receiver device. Such a synchronous rectifier can use the double-coupled inductor as described in this disclosure for the purpose of current sensing.

The solution presented in this disclosure can be applied to highly efficient power conversion systems either wired or wireless. Like the ones found internally or in the adapters that supply or charge the battery of electronic devices such as laptops, smartphones, smart glasses, smartwatches, fitness bands, virtual reality headsets and hand-controllers, headphones, gaming controllers, desktop accessories like a mouse, battery banks, remote controls, handheld terminals, portable gaming consoles, portable music players, key fobs, drones etc.

In order to describe the disclosure in detail, the following terms and notations will be used.

WPT Wireless Power Transfer

PCB Printed Circuit Board

IC Integrated Circuit

DC Direct Current

AC Alternating Current

AC-DC Alternating current to direct current converter converter

DC-DC Direct current to direct current converter converter

In this disclosure, wireless power transfer (WPT) systems are described. Wireless power transfer is the transmission of electrical energy without the use of wires as a physical link. This technology uses a transmitter device capable of generating a time-varying electromagnetic field that causes a circulating electric field through a receiver device (or devices) based on the principle of electromagnetic induction. The receiver device (or devices) is (are) capable of being supplied directly from this circulating electric field or they convert it to a suitable power level to supply to an electrical load or battery connected to them.

In the following, wireless power transmission systems, power converters and rectifiers are described in more detail.

Nowadays the number of battery-powered electronic devices is increasing rapidly because they provide freedom of movement and portability. While processors and screens keep increasing in size and power, battery operating time is expected to remain the same or even to increase. Moreover, charging times of such larger batteries are expected to be faster. Hence, power levels of AC-DC and DC-DC converters keeps increasing, but again, it is expected that these adapters remain small in size. At the same time the energy efficiency levels are expected to become higher and higher due to different factors such as having an acceptable surface temperature and safe operation.

Conduction losses occurring internally in a diode significantly contribute to the total losses of a power converter, especially in low output voltage applications. Nowadays, efficiency levels are actually legislated by different organizations worldwide. Therefore, to reduce the already mentioned conduction and switching losses and meet such standards, the power supply industry has implemented the use of better semiconductor devices along with better converter topologies.

As mentioned earlier, most of the conduction losses in a rectifier are due to the presence of diodes which can be approximated to be directly proportional to the forward voltage drop if the latter is considered to be roughly a fixed and constant voltage. Schottky diodes are often preferred because their lower forward voltage drop helps to reduce the conduction losses up to certain point. Nonetheless, such voltage drop is still relatively high and they are quite limited by the voltage ratings.

To further reduce such losses, synchronous rectification was introduced, which consists in the implementation of a controllable electronic (switching) device of low resistance, usually a FET (e.g. GaN, MOS), to replace the rectifier diode. Under certain current levels the voltage drop of these switching devices is considerably lower than that of a diode, consequently there is a reduction in conduction losses. Synchronous rectification is widely used in all kinds of DC-DC converters. Instead of the diode’s fixed forward voltage drop, when a MOSFET conducts, its voltage drop depends on to the instantaneous current flowing through it and to RDS<ON) , its on- state resistance, which is usually small enough to achieve much lower conduction losses. According to a first aspect, the disclosure relates to a current sensing apparatus, e.g., as shown in Figure 2, for sensing a current flowing through a current trace of the current sensing apparatus, the current sensing apparatus comprising: at least three layers of which two are electrically conductive layers and one is an electrically insulating layer, the at least three layers being arranged above each other; the current trace formed by a first electrically conductive layer of the at least three layers; and an embedded inductor formed by at least one second electrically conductive layer of the at least three layers; wherein the embedded inductor comprises a first plurality of conductive turns, that are wound along a first winding direction, and a second plurality of conductive turns that are wound along a second winding direction opposite to the first winding direction; and wherein the embedded inductor is configured to provide a sensing voltage indicative of a current flowing through the current trace, the sensing voltage resulting from a superposition of voltages induced by a current flowing through the current trace in each of the two pluralities of conductive turns.

Such current sensing apparatus or arrangement provides a non-invasive and non-disturbing current detection with minimum footprint that can be applied in compact electronic devices such as wearables and consumer electronics.

Because the inductor comprises two plurality of conductor windings wound in opposite direction, coupled to a single current trace 200, the double-coupling characteristic of this arrangement results in a summation of the voltage induced and in turn in an increase of the current flowing over the conducting path that the inductor 201 provides. In this way, the sensitivity of the current sensor is enhanced allowing its use in a wider range of applications.

Said double-coupling characteristic of this current sensing arrangement allows for a very small footprint and to still have a large enough mutual inductance to the current trace located in the adjacent layer, being able to detect the signal even at low load conditions.

The current sensing apparatus can be implemented within a multilayer integrated circuit board, for example in a multilayer PCB (Printed Circuit Board) or in a multilayer IC (integrated circuit) chip.

Embedding the inductor in a multilayer board allows for such a current sensing method to be used in devices with very limited space, for instance in substantially planar devices in which the overall height is restricted. Embedding the inductor in a multilayer board can be applied to any 2D coil geometry. If it can be drawn it can be fabricated. The above current sensing method can be used in other applications, not only for synchronization purposes. The current sensing apparatus as described in this disclosure is not meant to be a component or an IC on its own. It is not something meant to be isolated, alone, self-standing, it is rather meant to be included, implemented, embedded within a larger circuitry, e.g., within a larger PCB, within an IC with more functionalities, etc. For example, the current sensing apparatus can be implemented in a synchronous rectifier of a WPT receiver.

The proper operation of the current sensing apparatus depends on the existence and adequate location of the current trace which can represent the detection source and the coil which can represent the sensor. In that sense, the current sensing apparatus can be regarded as a current sensing arrangement.

In an exemplary implementation of the current sensing apparatus, the first plurality of conductive turns and the second plurality of conductive turns are arranged adjacent to each other on the at least one second conductive layer of the at least three layers. By such an adjacent arrangement, superposition of the voltages takes place since the magnetic field can directly couple into both pluralities of conductive turns, while being able to directly connect the two pluralities of conductive turns within the same layer

In an exemplary implementation of the current sensing apparatus, the current sensing apparatus comprises at least four layers of which two are the electrically conductive layers, one is the electrically insulating layer and one is another electrically insulating layer, the at least four layers being arranged above each other; wherein the electrically insulating layer and the other electrically insulating layer are sandwiching one of the embedded inductor, or the current trace.

This refers for instance to top-down fabrication process approaches, such as photolithography, where one substrate/insulating layer is needed per conductive layer, but the fabrication order of the conductive layers can be exchanged providing design flexibility, meaning the inductor can be the one on top of the current trace, and so the current trace can be the one sandwiched in that case.

In an exemplary implementation of the current sensing apparatus, the first plurality of conductive turns and the second plurality of conductive turns are formed by a same layer of the at least three layers or by different layers of the at least three layers. This provides flexibility in the design. Depending on the design or fabrication requirements and/or restrictions, specific layers and footprint space may be assigned and used for the conductive turns. In an exemplary implementation of the current sensing apparatus, the first plurality of conductive turns and the second plurality of conductive turns have the same or different coil geometries; and/or wherein the first plurality of conductive turns and the second plurality of conductive turns have the same or different number of turns. This provides flexibility in design. Depending on the footprint space available the coil geometries and/or number of conductive turns can be adjusted to achieve the desired coupling factor.

According to a second aspect, the disclosure relates to a current sensing apparatus, e.g., as shown in Figure 3, for sensing a current flowing through two current traces of the current sensing apparatus, the current sensing apparatus comprising: at least three layers of which two are electrically conductive layers and one is an electrically insulating layer, the at least three layers being arranged above each other; a first current trace and a second current trace formed by at least one first electrically conductive layer of the at least three layers; and an embedded inductor formed by a second electrically conductive layer of the at least three layers; wherein the embedded inductor comprises a plurality of conductive turns; wherein the embedded inductor is configured to provide a sensing voltage indicative of the current flowing through the two current traces, the sensing voltage resulting from a superposition of voltages induced by the current flowing through the first current trace and through the second current trace in the plurality of conductive turns.

Because the inductor comprises a single plurality of conductor windings coupled to two current traces 200a and 200b with current 202 flowing through them in opposite directions, the doublecoupling characteristic of this current sensing arrangement results in a summation of the voltage induced and in turn in an increase of the current 204 flowing over the conducting path that the inductor 201 provides. In this way, the sensitivity of the current sensor is enhanced allowing its use in a wider range of applications.

Said double-coupling characteristic of this current sensing arrangement allows for a very small footprint and to still have a large enough mutual inductance to the current trace located in the adjacent layer, being able to detect the signal even at low load conditions. As described above for the first aspect, the current sensing apparatus according to the second aspect can also be implemented within a multilayer integrated circuit board, for example in a multilayer PCB (Printed Circuit Board) or in a multilayer IC (integrated circuit) chip.

Embedding the inductor in a multilayer board allows for such a current sensing method to be used in devices with very limited space, for instance in substantially planar devices in which the overall height is restricted. Embedding the inductor in a multilayer board can be applied to any 2D coil geometry. If it can be drawn it can be fabricated. The above current sensing method can be used in other applications, not only for synchronization purposes.

As already described above for the current sensing apparatus of the first aspect, also the current sensing apparatus of the second aspect is not meant to be a component or an IC on its own. It is not something meant to be isolated, alone, self-standing, it is rather meant to be included, implemented, embedded within a larger circuitry, e.g., within a larger PCB, within an IC with more functionalities, etc. For example, the current sensing apparatus can be implemented in a synchronous rectifier of a WPT receiver.

The proper operation of the current sensing apparatus depends on the existence and adequate location of the current traces which can represent the detection source and the coil which can represent the sensor. In that sense, also the current sensing apparatus of the second aspect can be regarded as a current sensing arrangement.

In an exemplary implementation of the current sensing apparatus of the second aspect, the current flowing through the first current trace flows in opposite direction through the second current trace. By such an arrangement, superposition of the voltages takes place since the magnetic field of both traces can directly couple into the pluralities of conductive turns. If the current was flowing in the same direction through the current traces, the magnetic fields would mostly cancel out.

In an exemplary implementation of the current sensing apparatus of the second aspect, the first current trace and the second current trace are formed as substantially parallel current traces by the at least one first electrically conductive layer. Such a parallel configuration of the current traces improves the magnetic field strength by superposition and thus improves sensing of the current.

In an exemplary implementation of the current sensing apparatus of the second aspect, the first current trace and the second current trace are formed by a same electrically conductive layer of the at least three layers or by different electrically conductive layers of the at least three layers. This provides flexibility in the design. Depending on the design or fabrication requirements and/or restrictions, specific conductive layers and footprint space may be designated and used for the current traces.

In an exemplary implementation of the current sensing apparatus of the second aspect, the current traces and the embedded inductor are placed in consecutive layers of the at least three layers. Because usually the dielectric/substrate/insulating layer thickness is smaller than the minimum trace-to-trace spacing allowed, this arrangement optimizes the coupling between the current traces and the inductor, therefore improving the current sensing resolution.

In an exemplary implementation of the current sensing apparatus of the first aspect or of the second aspect, the current sensing apparatus comprises: at least five layers of which three are electrically conductive layers and two are electrically insulating layers, the at least five layers being arranged above each other; a ground plane shield, the ground plane shield being configured to shield the embedded inductor from coupling to other current traces on the same multilayer board, the ground plane shield being formed by a third electrically conductive layer of the at least five layers.

The current sensing can be completely shielded from the rest of the circuitry and surrounding noise by adding the ground plane, e.g., formed as a copper plane, underneath. This for example avoids false pulses to be send to a switching device when such current sensing apparatus is being used as part of a synchronization circuit.

In an exemplary implementation of the current sensing apparatus of the first aspect or of the second aspect, the current sensing apparatus comprises: an interconnection layer configured to interconnect the embedded inductor to a resonant network component arranged on the current sensing apparatus for creating an electromagnetic resonance. Such a configuration narrows the bandwidth enhancing the overall detection by filtering out noise and increasing the signal to noise ratio (SNR).

The interconnection layer can be implemented and placed according to the example of Figure 6, for instance. Other implementations are possible as well. For example, the component 602 can be placed in the same layer as the current trace or it can be placed in the same layer as the inductor, or in other locations. The current sensing apparatus can, for example, be fabricated within one of the following: a Printed Circuit Board, PCB, a High-Density Interconnect, HDI, Printed Circuit Board, a substrate-like PCB, an Integrated Circuit, IC, substrate, an integrated circuit chip.

According to a third aspect, the disclosure relates to a synchronization circuit, comprising the current sensing apparatus of the first aspect or of the second aspect. The current sensing apparatus or arrangement can be used in any synchronization circuit, in particular it is very beneficial for devices with very limited space, for instance in substantially planar devices in which the overall height is restricted.

In an exemplary implementation of the synchronization circuit, the synchronization circuit comprises: a resonant network formed by the embedded inductor and a capacitive element, the resonant network being configured to create an electromagnetic resonance with the embedded inductor. Such a configuration narrows the bandwidth enhancing the overall detection by filtering out noise and increasing the signal to noise ratio (SNR).

In an exemplary implementation of the synchronization circuit, the synchronization circuit comprises: a zero-crossing detection circuitry connected to and configured to work with the resonant network, the zero-crossing detection circuitry being configured to detect a zerocrossing of the sensed current and/or the sensing voltage. This allows synchronization between the switching device and the current flowing through them by generating a switching signal synchronized to the zero-crossing of the sensed current. .

In an exemplary implementation of the synchronization circuit, the sensed current is a reference current for driving a switching device; and the zero-crossing detection circuitry is configured to provide a switching signal to the switching device that is based on the zerocrossing of the sensed current and/or the sensing voltage. By such a zero-crossing detection circuitry, the switching device can be optimally controlled, synchronized to the zero-crossing of the sensed current.

In an exemplary implementation of the synchronization circuit, the capacitive element is configured to enable the resonant network creating an electromagnetic resonance with a frequency corresponding to that of the current and in turn an operating frequency of the switching device.

Such a configuration of the capacitive element narrows the bandwidth enhancing the overall detection, but for this to happen the frequency of resonance has to be the same or very close to that of the detected current flowing through the circuit to control. The current sensing apparatus for example, can be used in a synchronous rectifier, in particular in a synchronous rectifier of an isolated DC-DC converter.

According to a fourth aspect, the disclosure relates to a method for current sensing using a current sensing apparatus, e.g., as shown in Figure 2, for sensing a current flowing through a current trace of the current sensing apparatus, the current sensing apparatus comprising: at least three layers of which two are electrically conductive layers and one is an electrically insulating layer, the at least three layers being arranged above each other; the current trace formed by a first electrically conductive layer of the at least three layers; and an embedded inductor formed by at least one second electrically conductive layer of the at least three layers; wherein the embedded inductor comprises a first plurality of conductive turns, that are wound along a first winding direction, and a second plurality of conductive turns that are wound along a second winding direction opposite to the first winding direction; the method comprising: providing, by the embedded inductor, a sensing voltage indicative of a current flowing through the current trace, the sensing voltage resulting from a superposition of voltages induced by a current flowing through the current trace in each of the two pluralities of conductive turns.

Such a method for current sensing provides a non-invasive and non-disturbing current detection that can be applied with minimum footprint by compact electronic devices such as wearables and consumer electronics.

According to a fifth aspect, the disclosure relates to a method for current sensing using a current sensing apparatus, e.g., as shown in Figure 3, for sensing a current flowing through two current traces of the current sensing apparatus, the current sensing apparatus comprising: at least three layers of which two are electrically conductive layers and one is an electrically insulating layer, the at least three layers being arranged above each other; a first current trace and a second current trace formed by at least one first electrically conductive layer of the at least three layers; and an embedded inductor formed by a second electrically conductive layer of the at least three layers; wherein the embedded inductor comprises a plurality of conductive turns; the method comprising: providing, by the embedded inductor, a sensing voltage indicative of the current flowing through the two current traces, the sensing voltage resulting from a superposition of voltages induced by the current flowing through the first current trace and through the second current trace in the plurality of conductive turns. Such a method for current sensing provides a non-invasive and non-disturbing current detection that can be applied with minimum footprint by compact electronic devices such as wearables and consumer electronics.

BRIEF DESCRIPTION OF THE DRAWINGS

Further embodiments of the disclosure will be described with respect to the following figures, in which:

Figure 1 shows a circuit diagram illustrating an exemplary synchronous device 10;

Figure 2 shows a schematic diagram illustrating a first embodiment of a current sensing apparatus 20 according to the disclosure;

Figure 3 shows a schematic diagram illustrating a second embodiment of a current sensing apparatus 30 according to the disclosure;

Figure 4 shows a cross section view of a multilayer board 40 forming a current sensing apparatus 20, 30 according to the disclosure;

Figure 5a shows different geometries for the conductive turns of a current sensing apparatus 20 according to the first embodiment;

Figure 5b shows different geometries for the conductive turns and current trace(s) of a current sensing apparatus 30 according to the second embodiment;

Figure 6 shows a cross section view of another implementation of a multilayer board 60 forming a current sensing apparatus 20, 30 according to the disclosure;

Figure 7 shows a block diagram of a synchronous system or device 700 with a synchronization circuit 702 according to the disclosure;

Figure 8 shows a circuit diagram of an isolated power conversion system 80 as another implementation of a synchronous system or device with a synchronization circuit 702 according to the disclosure; and Figures 9a to 9d show different circuit diagrams with exemplary implementation of two current traces with the same current flowing through but in opposite direction, according to the second embodiment as shown in Figure 3.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following detailed description, reference is made to the accompanying drawings, which form a part thereof, and in which is shown by way of illustration specific aspects in which the disclosure may be practiced. It is understood that other aspects may be utilized and structural or logical changes may be made without departing from the scope of the disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the disclosure is defined by the appended claims.

It is understood that comments made in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if a specific method step is described, a corresponding device may include a unit to perform the described method step, even if such unit is not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary aspects described herein may be combined with each other, unless specifically noted otherwise.

Figure 1 shows a circuit diagram illustrating an exemplary synchronous device 10.

Techniques for current sensing and the current sensing apparatus as described in this disclosure are well suited for synchronous power converters commonly found in highly efficient secondary power supplies such as the adapters that supply or charge the battery of electronic devices (e.g., laptops, smartphones, tablets, smart glasses, earphones, wearables, console remote controls, etc.), using either wired or wireless power transfer. This is in general a challenge because it requires to detect the zero crossing 11 of the AC current 12, or well, that of the input voltage to control the switching device(s) 13 in synchrony. Moreover, among the different detection methods there are the ones that have low sensitivity, others that somehow disturb the system, and the isolated ones with enough sensitivity are usually of considerable size in their implementation which is a big constrain in compact electronic devices such as consumer electronics in general. Wireless power applications pose an increase challenge for zero crossing detection since usually the synchronous device 10 needs to switch with the same frequency than the wireless power link, which is usually done at high frequencies, meaning that the detection needs to be fast enough. Techniques for current sensing as presented in this disclosure can be efficiently applied for zero crossing detection 11 and driving signal(s) generation 14 and thereby controlling the switching device(s) 13.

Figure 2 shows a schematic diagram illustrating a first embodiment of a current sensing apparatus 20 with an inductor 201a, 201b according to the disclosure.

The current sensing apparatus 20 with inductor 201a, 201b can be used for sensing a current 202 flowing through a current trace 200 of the current sensing apparatus 20.

The current sensing apparatus 20 comprises: at least three layers of which two are electrically conductive layers 41 and one is an electrically insulating layer 42, the later not shown in this figure for simplicity, the at least three layers being arranged above each other, as can be seen in the example of Figure 4. The current trace 200 is formed by a first electrically conductive layer of the at least three layers.

The current sensing apparatus 20 comprises: an embedded inductor 201a, 201 b formed by at least one second electrically conductive layer of the at least three layers. The embedded inductor 201 a, 201 b comprises a first plurality of conductive turns 201a that are wound along a first winding direction, and a second plurality of conductive turns 201 b that are wound along a second winding direction opposite to the first winding direction as can be seen in Figure 2.

The embedded inductor 201a, 201 b is configured to provide a sensing voltage indicative of a current 202 flowing through the current trace 200. The sensing voltage results from a superposition of voltages induced by a current 202 flowing through the current trace 200 in each of the two pluralities of conductive turns 201a, 201b.

The current sensing apparatus 20 can be implemented within a multilayer integrated circuit board 40, as shown in the embodiment of Figure 4, for example in a multilayer PCB (Printed Circuit Board) or in a multilayer IC (integrated circuit) chip.

The first plurality of conductive turns 201a and the second plurality of conductive turns 201 b can be arranged adjacent to each other on the at least one second conductive layer of the at least three layers, e.g., as shown in Figure 2 where the first plurality of conductive turns 201a are placed on the right to the current trace 200 and the second plurality of conductive turns 201 b are placed in a same plane on the left to the current trace. In one embodiment, the current sensing apparatus 20 may comprise: at least four layers of which two are the electrically conductive layers, one is the electrically insulating layer and one is another electrically insulating layer. The at least four layers are arranged above each other, e.g., as shown in Figure 4. The electrically insulating layer and the other electrically insulating layer may be sandwiching one of the embedded inductors 201a, 201 b, or the current trace 200.

This refers for instance to top-down fabrication process approaches, such as photolithography, where one substrate/insulating layer 42 is needed per conductive layer 41 , but the fabrication order of the conductive layers can be exchanged providing design flexibility, meaning the inductor can be the one on top of the current trace 200, and so the current trace 200 can be the one sandwiched in that case.

In one embodiment, the first plurality of conductive turns 201a and the second plurality of conductive turns 201 b can be formed by a same layer of the at least three layers or by different layers of the at least three layers.

In one embodiment, the first plurality of conductive turns 201a and the second plurality of conductive turns 201 b can have the same or different coil geometries as shown for example in Figure 5.

In one embodiment, the first plurality of conductive turns 201a and the second plurality of conductive turns 201 b can have the same or different number of turns.

The current sensing apparatus 20 can be fabricated within one of the following: a Printed Circuit Board (PCB), a High-Density Interconnect (HDI) PCB, a substrate-like PCB, an Integrated Circuit (IC) substrate, an integrated circuit chip.

Figure 3 shows a schematic diagram illustrating a second embodiment of a current sensing apparatus 30 with inductor 201 according to the disclosure.

The current sensing apparatus 30 with inductor 201 can be used for sensing a current 202 flowing through two current traces 200a, 200b of the current sensing apparatus.

The current sensing apparatus 30 comprises at least three layers of which two are electrically conductive layers and one is an electrically insulating layer. The at least three layers are arranged above each other as shown in the example of Figure 4. The current sensing apparatus 30 comprises a first current trace 200a and a second current trace 200b formed by at least one first electrically conductive layer of the at least three layers.

The current sensing apparatus 30 comprises an embedded inductor 201 formed by a second electrically conductive layer of the at least three layers. The embedded inductor 201 comprises a plurality of conductive turns. The embedded inductor 201 is configured to provide a sensing voltage indicative of the current 202 flowing through the two current traces 200a, 200b. The sensing voltage results from a superposition of voltages induced by the current 202 flowing through the first current trace 200a and through the second current trace 200b in the plurality of conductive turns.

Both current traces 200a, 200b may be electrically connected at some place not shown in Figure 3 (examples can be seen in Figure 9) such that the current 202 flowing through the first current trace 200a is the same as the current 202 flowing through the second current trace 200b.

The current sensing apparatus 30 can be implemented within a multilayer integrated circuit board 40, e.g., as shown in Figure 4, for example in a multilayer PCB (Printed Circuit Board) or in a multilayer IC (integrated circuit) chip.

The current 202 flowing through the first current trace 200a should flow in opposite direction through the second current trace 200b.

In one embodiment, the first current trace 200a and the second current trace 200b may be formed as parallel current traces, as shown in Figure 3, by the at least one first electrically conductive layer.

In one embodiment, the first current trace 200a and the second current trace 200b may be formed by a same electrically conductive layer of the at least three layers or by different electrically conductive layers of the at least three layers.

In one embodiment, the current traces 200a, 200b and the embedded inductor 201 may be placed in consecutive layers of the at least three layers.

The current sensing apparatus 20 can be fabricated within one of the following: a Printed Circuit Board (PCB), a High-Density Interconnect (HDI) PCB, a substrate-like PCB, an Integrated Circuit (IC) substrate, an integrated circuit chip. Figure 4 shows a cross section view of a multilayer board 40 forming a current sensing apparatus 20, 30 according to the disclosure.

The multilayer board 40 is an implementation of the current sensing apparatus 20 described above with respect to Figure 2 or of the current sensing apparatus 30 described above with respect to Figure 3.

The multilayer board 40 with inductor 201 , 201a, 201 b can be used for sensing a current 202 flowing through a current trace 200 of the multilayer board 40 as shown in Figure 2 (or through two current traces 200a, 200b of the multilayer board 40 as shown in Figure 3).

The multilayer board 40 comprises at least three layers of which two are electrically conductive layers and one is an electrically insulating layer, the at least three layers being arranged above each other.

The multilayer board 40 comprises the current trace 200 formed by a first electrically conductive layer of the at least three layers as shown in Figure 2 (or a first current trace and a second current trace 200b formed by at least one first electrically conductive layer of the at least three layers as shown in Figure 3).

The multilayer board 40 comprises an embedded inductor 201a, 201b formed by at least one second electrically conductive layer of the at least three layers as shown in Figure 2 (or an embedded inductor 201 formed by a second electrically conductive layer of the at least three layers as shown in Figure 3).

The embedded inductor 201a, 201b comprises a first plurality of conductive turns 201a, that are wound along a first winding direction, and a second plurality of conductive turns 201b that are wound along a second winding direction opposite to the first winding direction as shown in Figure 2 (or a plurality of conductive turns as shown in Figure 3).

The embedded inductor 201a, 201b is configured to provide a sensing voltage indicative of a current 202 flowing through the current trace 200 as shown in Figure 2 (or to provide a sensing voltage indicative of the current 202 flowing through the two current traces 200a, 200b as shown in Figure 3).

The sensing voltage results from a superposition of voltages induced by a current 202 flowing through the current trace 200 in each of the two pluralities of conductive turns 201a, 201b as shown in Figure 2 (or a superposition of voltages induced by the current 202 flowing through the first current trace 200a and through the second current trace 200b in the plurality of conductive turns as shown in Figure 3).

In the example of Figure 4, the multilayer board 40 may have a current trace 200 in a first layer of conductive material, a miniature sensing inductor 201 , substantially flat on a second layer of conductive material, adjacent to the first layer and doubly magnetically coupled to the current trace(s). The inductor may have a certain number of turns, which in the example of this Figure 4 can be six but the number of turns can be different as well.

Some of the principal characteristics of the inductor according to this disclosure are that the inductor can have two pluralities of conductor windings (as shown in Figure 2 and Figure 5a, for example), very similar (ideally identical) and placed adjacent to each other. The first plurality of conductor windings can be connected to a second plurality of conductor windings wound in opposite direction, both may be in the same plane.

This image in Figure 4 shows how the current 202 flowing in the current trace 200 generates a magnetic field 203 that couples to both pluralities of conductor windings located in the adjacent layer (underneath in this case), and wherein the voltage induced in both pluralities of windings effectively adds up.

Figure 5a shows different geometries for the conductive turns of a current sensing apparatus 20 according to the first embodiment and Figure 5b shows different geometries for the conductive turns and current trace(s) of a current sensing apparatus 30 according to the second embodiment.

The current sensing inductors presented in this disclosure can have different geometry and number of turns. Figures 5a and 5b show exemplary geometries.

Fig. 5a depicts one way to achieve the double coupling characteristic, where a miniature embedded inductor 201 that includes a first plurality of conductor windings 201a wound in a plane connected to a second plurality of conductor windings 201b wound in opposite direction, in the same plane. Both pluralities of windings may couple to the current trace 200 laying on the adjacent layer. The changing magnetic field 203 induces an electric field, which results in the induced voltage. This induced voltage in both pluralities of windings effectively adds up and causes a current to flow 204 over the conducting path that the inductor 201 provides. Fig. 5b depicts the second way to achieve the double coupling characteristic, where a miniature embedded inductor 201 includes a plurality of windings wound approximately on a plane. The plurality of windings may couple to two current traces 200a and 200b with current 202 flowing in opposite directions, laying on the adjacent layer. The voltage induced by the changing magnetic fields 203a and 203b produced by both current traces into the plurality of conductor windings effectively adds up.

Figure 6 shows a cross section view of another implementation of a multilayer board 60 forming a current sensing apparatus 20, 30 according to the disclosure.

The multilayer board 60 is an implementation of the current sensing apparatus 20 described above with respect to Figure 2 or of the current sensing apparatus 30 described above with respect to Figure 3.

The multilayer board 60 may comprise at least five layers of which three are electrically conductive layers 41 and two are electrically insulating layers 42. The at least five layers are arranged above each other as shown in Figure 6.

The multilayer board 60 shown in Figure 6 may comprise a ground plane shield 600 which is configured to shield the embedded inductor 201a, 201 b, 201 from coupling to other current traces of the multilayer board 60. The ground plane shield 600 may be formed by a third electrically conductive layer of the at least five layers.

The multilayer board 60 shown in Figure 6 may comprise an interconnection layer 601 configured to interconnect the embedded inductor 201a, 201 b, 201 to a resonant network component 602 (e.g., a capacitive element) arranged on the multilayer board 60 for creating an electromagnetic resonance.

The interconnection layer 601 can be implemented and placed according to the example of Figure 6, for instance. Other implementations are possible as well. For example, the component 602 can be placed in the same layer as the current trace or it can be placed in the same layer as the inductor, or in other locations.

Fig. 6 shows an implementation of the multilayer board 60 that is different from the implementation of the multilayer board 40 shown in Figure 4. Similar to the cross-section view presented in Fig. 4, the board 60 has a current trace 200 in a first layer of conductive material 41 , a miniature sensing inductor 201 , substantially flat on a second layer of conductive material 41 , adjacent to the first layer and doubly magnetically coupled to the current trace(s). Nonetheless, in this case the multilayer board 60 includes two additional conductive layers 600 and 601.

Layer 600 can be a ground plane shield, for example, on a third plane adjacent to the second plane that prevents the miniature sensing inductor from coupling to any other traces and harvesting noise. Layer 601 can, for instance, comprise interconnections between the miniature sensing inductor and the component(s) 602 of the parallel resonant network comprised by the synchronization circuit, creating an electromagnetic resonance.

Figure 7 shows a block diagram of a synchronous system or device 700 with a synchronization circuit 702 according to the disclosure.

The synchronous system or device 700 shown in Figure 7 can implement the disclosed synchronization circuit 702 and therefore, the miniature embedded inductor 201 as well.

The system 700 may comprise among other modules, a driving module 706 and at least one switching device 701.

The synchronization circuit 702 may comprise a current trace 200, in which the source of current to detect 202 flows, zero-crossing detection circuitry 704, delay generation circuitry 705 and a parallel resonant network 703, which in turn may comprise a miniature embedded sensing inductor 201 and a capacitive element 602.

The synchronization circuit 702 and driving module 706 may be operated to provide the signals to control the ON/OFF behavior of the switching device(s) 701 in such a way that the behavior of the replaced diode can be emulated.

Figure 8 shows a circuit diagram of an isolated power conversion system 80 as another implementation of a synchronous system or device with a synchronization circuit 702 according to the disclosure.

The techniques for current sensing according to the disclosure can be used in power conversion systems, in particular in electrically isolated, synchronous systems, such as isolated switching mode power supplies or wireless power transfer systems. The isolated power conversion system 80 of Fig. 8, which depicts another possible implementation of a synchronous system or device 700 (see Figure 7) comprises a constant current AC source that can be the output of a DC-AC converter. This power source may be connected to a transformer or to a wireless power transfer link 800 composed of at least one transmitter coil and at least one receiver coil.

In order to have an efficient overall power conversion from the input to the output of the device, the involved power converters need to minimize losses. A way to minimize losses can be to use a synchronous rectifier on the secondary side or in the at least one receiver device. The synchronous rectifier can use the miniature embedded sensing inductor 201 for the purpose of sensing the current flowing through L2 by doubly-coupling to the current trace 200.

A parallel resonant network 703 can be formed by adding a capacitive element 602, whose voltage is the input signal to the zero-crossing detector 704. In this figure, the zero-crossing detector circuit applies an offset to the signal and utilizes a comparator to generate a unipolar pulse, but this is only one example, this unit can be implemented in many different ways.

The analog delay generator 705 can rely in the charging and discharging time of the capacitor and the switching levels of a digital gate or an additional comparator, to shift the signal as much as needed to achieve synchrony. Such delay needs to take into account the delays that may be introduced by any component and/or module down the line before reaching the gate of the switching device(s) 701. Depending on the rectifier topology, and nature of the switching device(s) 701 , further circuitry may be required in order to properly drive it (them). This circuitry is comprised in the so-called driving module 706, which for example can include a dedicated driver 803.

In some implementations, the rectifier may have more than one switching device, hence, generation of complementary signals and dead time between them may be required. In this exemplary figure, the latter requirements can be achieved with the use of modules 801 and 802.

Figures 9a show a circuit diagram of an exemplary synchronous device 90 using a current sensing apparatus or arrangement according to the second embodiment as shown in Figure 3.

The current sensing apparatus 30 as shown in Figure 3 can be implemented in the synchronous device 90. The current 202 flowing into the switching device(s) 13 can have a first current trace 200a and a second current trace 200b which can be used by the current sensing apparatus 30 for sensing the current 202 flowing through the two current traces 200a, 200b as described above with respect to Figure 3.

The zero-crossing detector 11 can detect a zero crossing of this current 202 and can control the driving signal(s) generation 14 for controlling the switching device(s) 13.

Figures 9b, 9c and 9d show different circuit diagrams with exemplary implementation to sense an alternating current 202 with a current sensing apparatus 30 as shown in Figure 3 where the two current traces with the same current flowing through but in opposite direction, according to the second embodiment as shown in Figure 3 are depicted. In Figure 9b, the two current traces 200a, 200b are located on the left side of the circuit between current source 11 and capacitive element C1. In Figure 9c, the two current traces 200a, 200b are chosen to be located on the right side of the circuit between capacitive element C1 and inductive element L1. In Figure 9d, the two current traces 200a, 200b are located right between the resonant network and the load on the receiver side of a WPT system with L2 inductively coupled by coupling factor M12 to L1.

While a particular feature or aspect of the disclosure may have been disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features or aspects of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms "include", "have", "with", or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprise". Also, the terms "exemplary", "for example" and "e.g." are merely meant as an example, rather than the best or optimal. The terms “coupled” and “connected”, along with derivatives may have been used. It should be understood that these terms may have been used to indicate that two elements cooperate or interact with each other regardless whether they are in direct physical or electrical contact, or they are not in direct contact with each other.

Although specific aspects have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific aspects shown and described without departing from the scope of the disclosure. This application is intended to cover any adaptations or variations of the specific aspects discussed herein. Although the elements in the following claims are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence.

Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art readily recognize that there are numerous applications of the disclosure beyond those described herein. While the disclosure has been described with reference to one or more particular embodiments, those skilled in the art recognize that many changes may be made thereto without departing from the scope of the disclosure. It is therefore to be understood that within the scope of the appended claims and their equivalents, the disclosure may be practiced otherwise than as specifically described herein.

Claims

1 . A current sensing apparatus (20) for sensing a current (202) flowing through a current trace of the current sensing apparatus, the current sensing apparatus comprising: at least three layers of which two are electrically conductive layers and one is an electrically insulating layer, the at least three layers being arranged above each other; the current trace (200) formed by a first electrically conductive layer of the at least three layers; and an embedded inductor (201a, 201b) formed by at least one second electrically conductive layer of the at least three layers; wherein the embedded inductor (201a, 201 b) comprises a first plurality of conductive turns (201a), that are wound along a first winding direction, and a second plurality of conductive turns (201b) that are wound along a second winding direction opposite to the first winding direction; and wherein the embedded inductor (201a, 201b) is configured to provide a sensing voltage indicative of a current (202) flowing through the current trace (200), the sensing voltage resulting from a superposition of voltages induced by a current (202) flowing through the current trace (200) in each of the two pluralities of conductive turns (201a, 201 b).

2. The current sensing apparatus (20) of claim 1 , wherein the first plurality of conductive turns (201a) and the second plurality of conductive turns (201 b) are arranged adjacent to each other on the at least one second conductive layer of the at least three layers.

3. The current sensing apparatus (20) of claim 1 or 2, comprising: at least four layers of which two are the electrically conductive layers, one is the electrically insulating layer and one is another electrically insulating layer, the at least four layers being arranged above each other; wherein the electrically insulating layer and the other electrically insulating layer are sandwiching one of the embedded inductor (201a, 201 b), or the current trace (200).

4. The current sensing apparatus (20) of any of claims 1 to 3, wherein the first plurality of conductive turns (201a) and the second plurality of conductive turns (201b) are formed by a same layer of the at least three layers or by different layers of the at least three layers.

5. The current sensing apparatus (20) of any of the preceding claims, wherein the first plurality of conductive turns (201a) and the second plurality of conductive turns (201b) have the same or different coil geometries; and/or wherein the first plurality of conductive turns (201a) and the second plurality of conductive turns (201b) have the same or different number of turns.

6. A current sensing apparatus (30) for sensing a current (202) flowing through two current traces (200a, 200b) of the current sensing apparatus, the current sensing apparatus comprising: at least three layers of which two are electrically conductive layers and one is an electrically insulating layer, the at least three layers being arranged above each other; a first current trace (200a) and a second current trace (200b) formed by at least one first electrically conductive layer of the at least three layers; and an embedded inductor (201) formed by a second electrically conductive layer of the at least three layers; wherein the embedded inductor (201) comprises a plurality of conductive turns; wherein the embedded inductor (201) is configured to provide a sensing voltage indicative of the current (202) flowing through the two current traces (200a, 200b), the sensing voltage resulting from a superposition of voltages induced by the current (202) flowing through the first current trace (200a) and through the second current trace (200b) in the plurality of conductive turns.

7. The current sensing apparatus (30) of claim 6, wherein the current (202) flowing through the first current trace (200a) flows in opposite direction through the second current trace (200b).

8. The current sensing apparatus (30) of claim 6 or 7, wherein the first current trace (200a) and the second current trace (200b) are formed as parallel current traces by the at least one first electrically conductive layer.

9. The current sensing apparatus (30) of any of claims 6 to 8, wherein the first current trace (200a) and the second current trace (200b) are formed by a same electrically conductive layer of the at least three layers or by different electrically conductive layers of the at least three layers.

10. The current sensing apparatus (30) of any of claims 6 to 9, wherein the current traces (200a, 200b) and the embedded inductor (201) are placed in consecutive layers of the at least three layers.

11. The current sensing apparatus (20, 30) of any of the preceding claims, implemented within a multilayer board (40, 60), the current sensing apparatus (20, 30) comprising: at least five layers of which three are electrically conductive layers and two are electrically insulating layers, the at least five layers being arranged above each other; a ground plane shield (600), the ground plane shield (600) being configured to shield the embedded inductor (201a, 201 b, 201 ) from coupling to other traces of the multilayer board (40, 60), the ground plane shield (600) being formed by a third electrically conductive layer of the at least five layers.

12. The current sensing apparatus (20, 30) of any of the preceding claims, comprising: an interconnection layer configured to interconnect the embedded inductor (201a, 201 b, 201) to a resonant network component arranged on the current sensing apparatus for creating an electromagnetic resonance.

13. A synchronization circuit (702), comprising: the current sensing apparatus (20, 30) of any of the preceding claims.

14. The synchronization circuit (702) of claim 13, comprising: a resonant network (703) formed by the embedded inductor (201 , 201a, 201 b) and a capacitive element (602), the resonant network (703) being configured to create an electromagnetic resonance with the embedded inductor (201a, 201b, 201).

15. The synchronization circuit (702) of claim 14, comprising: a zero-crossing detection circuitry (704) connected to and configured to work with the resonant network (703), the zero-crossing detection circuitry (704) being configured to detect a zero-crossing of the sensed current (202) and/or the sensing voltage.

16. The synchronization circuit (702) of claim 15, wherein the sensed current (202) is a reference current for driving a switching device (701); and wherein the zero-crossing detection circuitry (704) is configured to provide a switching signal to the switching device (701) that is based on the zero-crossing of the sensed current (202) and/or the sensing voltage.

17. The synchronization circuit (702) of claim 16, wherein the capacitive element (602) is configured to enable the resonant network (703) creating an electromagnetic resonance with a frequency corresponding to that of the current (202) and in turn an operating frequency of the switching device (701).