Magnetic field distrubtion in wireless power

Techniques of magnetic field distribution are described herein. The techniques may include forming a wireless charging component including a driving coil to receive a driven current generating a magnetic field. An outer turn of a parasitic coil may be formed, wherein the outer turn is adjacent to the driving coil. An inner turn of the parasitic coil may be formed, wherein an inductive coupling between the driving coil and the parasitic coil generates a redistribution of a portion of the magnetic field at the inner turn.

TECHNICAL FIELD

This disclosure relates generally to techniques for wireless charging. Specifically, this disclosure relates to achieving a desired distribution of a magnetic field associated with a wireless charging component.

BACKGROUND ART

Magnetic resonance wireless charging may employ a magnetic coupling between a transmit (Tx) coil and a receive (Rx) coil. A common issue seen in these types of wireless charging systems is a non-uniform distribution of power delivered to the Rx coil as it is moved to various dispositions in a plane parallel to a plane of a Tx coil surface. In this scenario, a non-uniform power distribution received at the Rx coil may be due to a non-uniform magnetic field. The variation of the magnetic field may be especially pronounced when the Tx and Rx coils are closer together.

DESCRIPTION OF THE ASPECTS

The present disclosure relates generally to techniques for creating a certain distribution of magnetic field in a wireless power transfer system. As discussed above, magnetic resonance wireless charging systems may employ a magnetic coupling between a transmit (Tx) coil and a receive (Rx) coil. Non-uniform power transfer distribution may be due to variations occurring in the magnetic field associated with the Tx coil, for example. The techniques described herein include a driving coil and a parasitic coil, wherein the parasitic coil is configured to inductively couple to the driving coil, and redistribute a magnetic field associated with the coil to a disposition that is based on the geometry of the parasitic coil.

FIG. 1Ais perspective view of a diagram illustrating a device to be wirelessly coupled to a transmitting coil having a parasitic coil and a driving coil. As illustrated inFIG. 1, a device102may be placed on a Tx coil104. The coil may include a driving coil106and one or more parasitic coils108. As discussed in more detail below, the Tx coil104may have a magnetic field associated with a current injected into the driving coil106. The parasitic coil108may redistribute the magnetic field in a configurable manner based on the width of the parasitic coil.

In some aspects, the wireless Tx coil104may be used in a wireless charging system wherein the device102may be charged by inductive coupling between the Tx coil104and a Rx coil (not shown) in the device102. In some aspects, the wireless Tx coil104may be used in near-field communication wherein the Tx coil104transmits near field radio signals to a Rx coil in the device102via magnetic induction.

FIG. 1Bis coordinate system for the transmitting coil ofFIG. 1A. The “Z” direction is perpendicular to a horizontal plane of the Tx coil104, and is perpendicular to the “R” direction indicated inFIG. 1B. The variable “r” is a scalar number representing a distance from a center point of the Tx coil104to a Rx coil110, while the variable “a” is a radius of the Tx coil104. The variable “z” is a scalar number representing the distance in the “Z” direction between the Rx coil110and the Tx coil104. The Z direction magnetic field received by the Rx coil110is represented by “Hz” and, as indicated inFIG. 1, is a function of the distance from the center point of the Tx coil104to the Rx coil110. Variation of Hzmay result in a variation in the power received at the Rx coil110. In the aspects described herein, the magnetic field Hzmay be redistributed by the parasitic coil108as discussed in more detail below.

FIG. 2is top view of a diagram illustrating a wireless transmitting component having a parasitic coil and a driving coil. The wireless transmitting component ofFIG. 2may be a Tx coil, such as the Tx coil104inFIG. 1. As illustrated inFIG. 1, the Tx coil104includes the driving coil106and the parasitic coil108. The driving coil106may be driven by a current “I0” propagating in a first direction as indicated by the arrow202. The parasitic coil108may include an outer turn204and an inner turn206. The outer turn204may inductively couple to the driving coil106as a result of the current I0. The inductive coupling between the driving coil106and the outer turn204may result in a current “αI0” propagating in a direction opposite to the direction202driving current I0as indicated by the arrow208. As the current “αI0” reaches the inner turn206of the parasitic coil, the current is propagating in a direction similar to the direction of the driving current I0as indicated by the arrow210. In this scenario, α is a fraction, such that a resulting magnetic field associated with the current αI0traveling in the direction210is a fraction of the original driving current I0. The magnitude of α is related to the width of the parasitic coil indicated at212inFIG. 2. For example, the width212of the parasitic coil may be defined by the difference between a radius214of the outer turn204and a radius216of the inner turn218. WhileFIG. 2illustrates one parasitic coil108and one driving coil106, multiple parasitic coils may be used to further redistribute the magnetic field of the driving coil, as discussed in more detail below.

FIG. 3is top view of a diagram illustrating a wireless charging coil having a driving coil and multiple parasitic coils. The current associated with the driving coil106may be redistributed by the parasitic coil108as well as additional parasitic coils303,304,306. As illustrated inFIG. 3, the driving coil106may have a radius310, and the inner turn of the parasitic coil108may have a radius312. The radius312may be selected based on a desired distribution of magnetic fields, or in other words, a desired redistribution of the magnetic field associated with the driving coil106. Similarly, the radius314of an inner turn of the parasitic coil303, as well as the radii316and318of the parasitic coils304,306, respectively, may be selected based on a desired distribution of magnetic fields as the radii become shorter.

In aspects of the present disclosure, the driving coil106and the parasitic coil108are concentric to a center point of the coil. However, the coils106and108are not necessarily concentric, but may be implemented with any suitable arrangement based on a desired magnetic field distribution. In aspects, the desired distribution of magnetic fields generates a substantially even distribution in comparison to a distribution associated with a Tx coil that does not include a parasitic coil, as discussed in more detail below in relation toFIG. 6. For example, the radii312,314,316,318may be fractions, such as 0.8, 0.6, 0.4, and 0.2, respectively, of the radius310of the driving coil106. The resulting current at each inner turn of the parasitic coils108,303,304, and306, may be 0.21 I0, 0.17 I0, 0.1 I0, 0.05 I0, respectively. In this scenario, the current resulting at each inner turn of the parasitic coils reflects a redistribution of the original driving current I0, effectively evenly distributing the magnetic field and therefore, more evenly transmitting power to a receiving coil.

FIG. 4is top view of a diagram illustrating a wireless charging coil having a driving coil including multiple turns and multiple parasitic coils. The wireless charging coil400illustrated inFIG. 4includes a driving coil having multiple turns as indicated by the dashed circle402. In this aspect, the wireless charging coil400may include a first parasitic coil404and a second parasitic coil406. In the aspects described herein, parasitic coils need not be circular in shape. For example, as illustrated inFIG. 4, the driving coil402as well as the parasitic coils404,406are not perfect circles but are more oval in shape. Other shapes may be implemented according to a given design to distribute the magnetic field in a desired distribution.

FIG. 5is perspective view of a diagram illustrating a wireless charging coil having multiple driving coils and multiple parasitic coils. As illustrated inFIG. 5, the aspects described herein are not limited to a single driving coil. Rather, multiple driving coils502may be used. One or more parasitic coils504,506,508,510may be used to redistribute magnetic fields of the multiple driving coils502. In aspects, the multiple driving coils502may be selectively implemented having similar radii or varying radii, enabling design flexibility of the Tx coil, and in choosing a coil's inductance.

FIG. 6is a graph illustrating a substantially even distribution of a magnetic field in relation to a magnetic field of a wireless charging component without a parasitic coil. As discussed above, the aspects described herein may include a redistribution of the magnetic field of a driving coil. The graph600illustrates a distribution602of a magnetic field when parasitic coils are used to redistribute the magnetic field associated with a driving coil. In comparison to the distribution602, a distribution604is relatively more uneven when a coil does not include a parasitic element, such as the parasitic coils discussed above in reference toFIGS. 1-5.

FIG. 7is a graph illustrating a substantially even distribution of a magnetic field in relation to a magnetic field of a wireless component having multiple turns without a parasitic coil. As discussed above, the aspects described herein may include a redistribution of the magnetic field of a driving coil. The graph700illustrates a wireless component702having multiple turns in a driving coil as well as having one or more parasitic coils. The magnetic field distribution of the wireless component702is indicated by the line704. As illustrated inFIG. 7, a wireless component706having multiple turns, but not having one or more parasitic coils has a magnetic field distribution, indicated by the line708, that includes more variation in terms of magnitude than the distribution704.

FIG. 8is a diagram illustrating an example parasitic coil with a tuning element. A parasitic coil802may include a tuning element804. As illustrated inFIG. 8, the tuning element804may be a capacitor. In aspects, the tuning element804may be configured to enable tuning flexibility of the current on the parasitic coil. For example, the parasitic coil802may be turned on or near a resonance frequency of a driving coil. Tuning the parasitic coil802on or near the resonance frequency of the driving coil may achieve more flexibility in redistribution of the current of the driving coil. The aspects illustrated inFIG. 8, may be implemented in any combination of the aspects described herein.

FIG. 9is a flow diagram illustrating a method for forming a wireless charging component. The method900may include, forming a driving coil at block902. The driving coil may be configured to receive a driven current resulting in a magnetic field. A parasitic coil may also be formed. At block904, an outer turn of the parasitic coil is formed wherein the outer turn is adjacent to the driving coil. An inner turn is formed at block906, wherein an inductive coupling between the driving coil and the parasitic coil at the outer turn generates a redistribution of a portion of the magnetic field at the inner turn.

As discussed above, the portion of the magnetic field that is redistributed to the inner turn of the parasitic coil may be based on a distance between the outer turn and the inner turn. Therefore, in some aspects, the portion that is redistributable is configurable based on the distance, and the parasitic coil may be formed based on a desired magnetic field distribution profile. For example, a substantially even distribution, such as the distribution602discussed above in reference toFIG. 6, may be desired such that a substantially even power distribution associated with the magnetic field distribution is achieved. In aspects, a substantially even power distribution may enable wireless charging to be relatively agnostic to the location of a receiving coil in relation to the transmitting coil.

It is to be noted that, although some aspects have been described in reference to particular implementations, other implementations are possible according to some aspects. Additionally, the arrangement and/or order of circuit elements or other features illustrated in the drawings and/or described herein need not be arranged in the particular way illustrated and described. Many other arrangements are possible according to some aspects.