Wireless power transfer using capacitive sensors

Abstract

Various embodiments of the present disclosure relate to wireless power transfer using capacitive sensors. A capacitor sensor array (or grid) above a wireless power transmitting coil may include: a first set of lines; a second set of lines intersecting the first set of lines; a first multiplexer coupled to provide charge (e.g., in the form of a DC voltage) from a voltage source to the first set of lines, and to provide a first signal to detect the voltage on each line; and a second multiplexer coupled to provide charge from a voltage source to the second set of lines, and to provide a second signal to detect the voltage on each line, wherein an object is positioned relative to the location of the first set of lines and the second set of lines. According to some embodiments, a wireless power receiving coil and a rectifier circuit can be used to form a capacitor sensor to sense the capacitance between a receiving coil and a transmitting coil for better alignment between the two coils. Other embodiments are also provided.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 787,553, filed on January 2, 2019, which is incorporated herein by reference, and claims priority to U.S. Provisional Patent Application No. 62 / 786,200, filed on December 28, 2018, which is incorporated herein by reference. Technical Field

[0003] Embodiments of the present invention relate to wireless transfer of power, and in particular to capacitive sensors associated with wireless power transfer. Background Art

[0004] Mobile devices such as smartphones, tablets, wearables, and other devices increasingly use wireless charging systems. Typically, wireless power transfer involves a transmitter driving a transmission coil, and a receiver having a receiver coil placed close to the transmission coil. The receiver coil receives the wireless power generated by the transmission coil, and uses the received power to drive a load, such as to provide power to a battery charger.

[0005] There are currently a variety of different standards for the wireless transfer of power. The more common standards for the wireless transmission of power include the Alliance for Wireless Power (A4WP) standard and the Alliance for Wireless Power standard, i.e., the Qi standard. Under the Alliance for Wireless Power Qi specification, a resonant inductive coupling system is utilized to charge a single device at the resonant frequency of the receiver coil circuit. In the Qi standard, the receiving device coil is placed in close proximity to the transmitting coil, while in the A4WP standard, the receiving device coil is placed near the transmitting coil (possibly together with other receiving coils belonging to other charging devices). Any wireless power protocol or additional variants may include a combination of charging methods (i.e., one transmitter to one receiver, or one transmitter to multiple receivers).

[0006] Typically, a wireless power system includes: a transmitter coil that is driven to generate a time-varying magnetic field; and a receiver coil, which may be part of a device such as a cell phone, PDA, computer, or other device, positioned relative to the transmitter coil to receive the power transmitted in the time-varying magnetic field.

[0007] An ongoing issue with wireless power transfer is the alignment of the receive coil to the transmit coil and the positioning of foreign objects adjacent to the wireless power transmitter.

[0008] Therefore, there is a need to develop better systems to locate the alignment between the wireless power transmitting coil and the receiving coil as well as the location of foreign objects. Summary of the invention

[0009] According to some embodiments, a capacitor sensor that can be used on a wireless power transmission coil is proposed. In some embodiments, the capacitor sensor may include: a first set of lines; a second set of lines intersecting the first set of lines; a first multiplexer coupled to the first set of lines, the first multiplexer configured to: provide charge from a battery to the first set of lines, and provide a first signal to a first ADC for sampling and holding to detect a voltage on each line in the first set of lines; and a second multiplexer coupled to the second set of lines, the second multiplexer configured to: provide charge from a battery to the second set of lines, and provide a second signal to a second ADC for sampling and holding to detect a voltage on each line in the second set of lines, wherein the object is positioned relative to where the first set of lines and the second set of lines are located.

[0010] According to some embodiments, the capacitor sensor can be part of a receiver or a transmitter. In some embodiments, the capacitor sensor uses a receiving coil and a rectifier circuit device. In power transfer operation, the rectifier circuit device rectifies the AC signal in the receiving coil and provides a rectified voltage at the output terminal. However, in order to align the receiving coil with the transmitting coil, the operation of the receiving coil and the rectifier circuit device is reversed: the output terminal becomes an input that receives a DC voltage, and the rectifier circuit device couples the DC voltage to the receiving coil. The voltage change on the receiving coil is then monitored to detect the current flowing through the capacitor formed by the receiving coil and the transmitting coil. The voltage change is used to detect the presence of the transmitting coil and is used to align the two coils for optimal power transfer. Alignment can be achieved by maximizing the receiving coil capacitance.

[0011] These and other embodiments are discussed below with respect to the following figures. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1A A wireless power system is illustrated.

[0013] Figure 1B A transmitter assembly with a capacitive sensor is illustrated in accordance with some embodiments.

[0014] Figure 2 and Figure 3 An example capacitive sensor for use with a transmitter assembly is illustrated.

[0015] Figure 4 An example of a transmitter assembly having a capacitive sensor in accordance with some embodiments is illustrated.

[0016] Figure 5 is a flow chart of one example of transmitter operation using a capacitive sensor in accordance with some embodiments.

[0017] Figure 6 The capacitance between the transmitting coil and the receiving coil is shown.

[0018] Fig. 7A and Figure 7B The configuration of the receiving coil is shown.

[0019] Fig. 8A and Figure 8B The diagram illustrates a capacitance detection operation using a receiving coil.

[0020] These figures are discussed further below. DETAILED DESCRIPTION

[0021] In the following description, the specific details of describing some embodiments of the present invention are set forth. However, it is clear to those skilled in the art that some embodiments may be practiced without some or all of these specific details. The specific embodiments disclosed herein are intended to be illustrative and not restrictive. Those skilled in the art may realize other elements, even if not specifically described here, but these elements are within the scope and spirit of the present disclosure.

[0022] This description illustrates aspects of the invention, and the embodiments should not be considered restrictive, and the claims define the protected invention. Various changes may be made without departing from the spirit and scope of the description and claims. In some cases, well-known structures and techniques are not shown or described in detail to avoid obscuring the present invention.

[0023] Figure 1A An example wireless power transmission system 100 is illustrated. Figure 1A As illustrated in , a transmitting device 102 is coupled to drive a transmitting coil 106 to generate a time-varying magnetic field. The time-varying magnetic field induces a current in a receiving coil 108. The receiving coil 108 is coupled to a receiving device 104, which receives the transmitted wireless power. However, it is difficult to detect the difference between a foreign object and a misaligned receiving coil 108 (e.g., misalignment of the device 102 (a mobile phone or some other type of device)).

[0024] Figure 1B FIG. 1 illustrates a transmit coil assembly 120 according to some embodiments. Figure 1B , the transmitting coil 106 may be mounted on a substrate 110. A capacitive sensor 112 may be mounted on the transmitting coil 106. The capacitive sensor 112 may be used to identify the object size and location of the receiving device 104 or a foreign object, or may be used to identify the presence of the device 104 or a foreign object on the surface of the transmitting coil assembly 120.

[0025] Previous attempts to identify foreign objects include, for example, monitoring power loss or Q-factor measurements.Alignment issues can be addressed using forced mechanical alignment of the receiving device 104 with the transmitting device 102 .

[0026] However, according to embodiments of the present invention, the conductive grid array 112 can be placed above the transmit coil 106. The conductive grid array 112 can be used for object detection, object position and size sensing. Additionally, in some embodiments, the conductive grid array 112 can provide an electric interference comb filter to reduce radiated emissions from the transmit coil 106.

[0027] Figure 2 The grid array 112 and circuit devices 202 and 204 for driving the grid array 112 are shown. As shown, the grid array includes horizontal lines 130h and vertical lines 130v (the lines 130 are shown in a top view, and the designations of horizontal and vertical are arbitrary and refer only to a grid formed by two sets of mutually orthogonal lines). Figure 2 As illustrated in , the capacitive sensor is formed using thin PCB traces 112h, 112v in a grid array pattern (substrate 110 may be a PCB (i.e., printed circuit board) or some other type of substrate). Analog multiplexers 210h and 210v or other methods may be used to apply a known voltage individually to each line 130 (i.e., 130h, 130v) of the grid. A sample and hold technique with an analog-to-digital converter (ADC 240h, 240v, which may be two converters or a single converter) may then be used to monitor the decay rate on each line at a time. A voltage drop exceeding a typical value indicates that a metal object is over that particular line.

[0028] like Figure 2 , the circuit 202 may include an analog multiplexer 210h coupled to the horizontal line 130h and a transistor 220h coupled to the output of the multiplexer to charge the horizontal line 130h selected by the multiplexer to the voltage of the battery 230. The multiplexer output may also be coupled to an ADC sample and hold circuit that includes an ADC (analog to digital converter) 240h and a capacitor 244h connected to ground (or another reference voltage) to sample the voltage on the horizontal line.

[0029] Similarly, circuit 204 includes an analog multiplexer 210v coupled to vertical line 130v and a transistor 220v coupled to the MUX output to charge the vertical line 130v selected by the multiplexer to the voltage of a battery 230 (or some other regulated voltage source for applying a fixed known voltage to each line). The multiplexer output is also coupled to an ADC sample and hold circuit that includes an ADC 240v and a capacitor 244v connected to ground (or another reference voltage) to sample the voltage on the vertical line.

[0030] Thus, circuits 202 and 204 may use multiplexers to cycle through and charge each of the horizontal and vertical lines of the grid. Specifically, controller 250 turns on transistor 220h and causes MUX 210h to select line 130h to charge the line to the battery 230 voltage. Similarly, controller 250 turns on transistor 220v and causes MUX 210v to select line 130v to charge the line to the battery 230 voltage. After being charged, the voltages on the lines may be monitored one at a time, or two at a time (one horizontal line and one vertical line) by monitor 260 connected to the output of ADC 240, and the drop in voltage may be monitored over time. As described above, if the voltage on a line drops faster than a threshold rate (e.g., than the voltage on the other lines), or at a particular time, the voltage is below a particular threshold (e.g., a threshold set by the voltages on the other lines), the line is close to an object, and the location of the object is therefore determined. The size and position of the object may be determined by compiling the data on each of the horizontal and vertical lines 130 .

[0031] Figure 3 The operation is illustrated when an object 302 is placed over the capacitive sensor 112. (For simplicity, Figure 3 Controller 250 and some other features are omitted. ) Object 302 can be a device to be charged, such as a cell phone, a receiving coil, or can be a metallic foreign object. With object 302 placed over sensor 112, a capacitor is formed between thin trace 130 (one plate of the capacitor) and metallic object 302. When an electric field is created by charging wire 130, charge is transferred from the wire to the metallic object when an object is in close proximity. This results in a voltage change on the affected wire, as indicated by the following equation:

[0032] dV=i c dt / C

[0033] Where dV is the voltage change, i c is the capacitive current resulting from the electric field loss to the object 302 , dt is the unit of time, and C is the effective capacitance between the wire and the object 302 .

[0034] Thus, when object 302 is nearby, the electric field will cause the voltage on wires 130 near the object to decay faster. Thus, the object and its size can be detected based on which of wires 130 are losing voltage at a faster rate. Thus, sampling the voltage on each wire after one time unit will produce a change of approximately 0V in the absence of object 302 and a change of negative voltage in the presence of object 302. This is in Figure 3 This is illustrated by the “+” and “−” associated with each line, which depends on whether the line passes close to the object 302.

[0035] As in Figure 3 As further illustrated in FIG. 2 , in some embodiments, capacitors 270 are coupled to each line to store charge. These capacitances (eg, 10 pF to 30 pF per line in some embodiments) may depend on the multiplexer parasitic capacitance and the selection / deselection speed.

[0036] By storing charge on each line of the grid array of capacitive sensors 112, and then sampling the rate at which the voltage decays, the position, distance, and size of an object can be detected with reasonable accuracy. With this information, the alignment of a phone or the location of a foreign object can be detected. By rapidly charging the lines 130, and then checking the voltage decay one at a time, the voltage decay on the line can indicate when an object is over it. Using the grid pattern, we can find the location.

[0037] Those skilled in the art will recognize that the capacitive sensor 112 may include patterns other than a grid pattern. In addition, additional circuitry may be included so that multiple lines 130h in the horizontal direction and multiple lines 130v in the vertical direction may be charged and sampled simultaneously. Although the additional circuitry may improve the response time of the sensor array 112, it increases the required circuitry.

[0038] For capacitive sensors such as capacitive sensor 112, several applications are clear. For example, capacitive sensor 112 can detect edges, and therefore can detect the size, shape, and position of ferrous objects for alignment observation. In some systems, FOD (foreign object detection) settings can be adjusted based on the placement of the object. For example, Figure 4 A transmitter assembly 120 having three transmitting coils 106.1, 106.2, 106.3 is shown. A capacitive sensor 112 (with Figure 2 , Figure 31, 106.3. The capacitive sensor 112 senses an object 302 that is above coil 106.2 and not above coils 106.1, 106.3. If the transmitter 120 determines that the object 302 is a device to be charged (e.g., this can be determined from the size or shape of the object 302, or by the transmitter 120 attempting to wirelessly communicate with the object 302 through coil 160.2 acting as an antenna, or by the transmitter 120 receiving a user command), the transmitter 120 starts wireless power transfer via coil 106.2; the other two coils are inactive. If the transmitter 120 determines that the object 302 is a foreign object, the transmitter 120 does not start power transfer, and an alarm signal may be generated. In addition, if power transfer is in progress, the transfer may be shut off until the object is removed.

[0039] Additionally, during wireless power transfer, the horizontal or vertical lines can be grounded to create an EMI comb filter shield.

[0040] Figure 5 is a flow chart of transmitter operation according to some embodiments. In step 510, (multiple) multiplexers 210 select one or more lines 130. In step 514, the selected lines are connected to the battery 230 via (multiple) transistors 220 for a predetermined charging time, or until the lines reach a predetermined charging voltage. In step 518, the lines are disconnected from the battery for a predetermined discharge time, or until the lines reach a predetermined discharge voltage. For each line, the final voltage reached during the discharge time is recorded, or the time taken for the lines to reach the discharge voltage is recorded. These recorded values ​​can be measured by a monitor circuit including an ADC 240 and a monitor 260, or some other suitable monitor circuit. The recorded values ​​can be recorded in a suitable computer readable memory (e.g., a semiconductor register). The monitor 260 can include a microcontroller.

[0041] The above steps may be repeated until all rows have been selected. Alternatively, these steps may be performed for only some of the lines, ie for lines covering a single one of the transmit coils 106 if multiple transmit coils are present.

[0042] At step 530, transmitter control actions are taken based on the recorded values, as described above. For example, if a foreign object is detected above an operating transmitter coil, the coil is turned off.

[0043] In some embodiments, wire 130 may or may not be present, and capacitance sensing may be performed by receiving device 104 instead of (or in addition to) the transmitter. Receiver 104 may sense the capacitance between receiving coil 108 and the transmitter to help align receiving coil 108 for optimal power transfer. Figure 6 A configuration 600 of a transmitting coil 106 positioned relative to a receiving coil 108 is illustrated. The receiver coil 108 is coupled to a driver IC 104C, which may include a rectifier circuit that provides a rectified voltage VRECT generated from the receiver coil current. The driver 104C may also include circuitry for monitoring the voltage on the receiver coil 108 as needed for optimal capacitive coupling to the transmitting coil 106. The voltage V on the receiver coil satisfies the following relationship:

[0044]

[0045] Where dV is the voltage change on the receiving coil 108, i c is the "capacitor current" reflecting the electric field losses between the receive coil 108 and the transmit coil 106, and C is the effective capacitance, which increases with proximity and alignment with the transmit coil 106. Figure 6 Monitoring of the capacitance of the receiver coil 108 relative to the transmitter coil 106 is illustrated, but the capacitance of the receiver coil 108 may be monitored by monitoring voltage changes when any metal object is provided near the receiver coil 108 .

[0046] Any suitable technique may be used to monitor the voltage on the receiving coil, which may include a combination of the above Figure 3 and Figure 3 As a non-limiting example, such a technique may include using an ADC and / or analog circuitry to monitor the receive coil discharge rate. In particular, the discharge rate may be monitored by sensing that the voltage on the receive coil is dropping faster than usual (based on history); or by sensing that the receive coil voltage is below a certain threshold at a certain time. Such sensing may be accomplished using digital or analog circuitry (including a time-to-digital converter, and / or a delay line for sensing when the voltage of the receive coil reaches a threshold, and / or a comparator, and / or some other circuitry).

[0047] Fig. 7A and Figure 7B The control circuit 104C is illustrated coupled to the receive coil 108 . Fig. 7A The diagram shows a schematic diagram, and Figure 7B The receiving coil 108 and the circuit board 104B including the control circuit 104C are shown. Figure 6 As discussed, the voltage across the receive coil 108 may be monitored to capacitively detect the presence of a transmit coil or other object.

[0048] exist Fig. 7AIn the embodiment of the present invention, the receiving coil 108 is connected to a synchronous rectifier, which includes PMOS transistors 702H, 704H, 702L, 702H driven by drivers 708H, 708L. Specifically, one end of the receiving coil 108 is connected to a node 710L between the transistors 702L, 704L connected in series. The node 710L is connected to a MOSFET driver 708L through a capacitor, and the MOSFET driver 708L drives the transistors 702L, 704L. Similarly, the other end of the receiving coil 108 is connected to a node 710H between the transistors 702H, 704H connected in series through a capacitor Cs. The node is connected to a MOSFET driver 708H through a capacitor, and the MOSFET driver 708H drives the transistors 702H, 704H. A node VRECT providing a rectified voltage is connected to the sources of the transistors 702H, 702L.

[0049] In power transfer operation, node VRECT provides the rectified voltage generated by the rectifier. However, before power transfer, node VRECT can be connected to a DC power source (possibly an external power source, not shown) to apply a DC voltage V to the receive coil 108 and monitor the voltage change dV in the receive coil. (At any given time during this operation, the entire coil is forced to be at the same voltage, i.e., the voltage across the coil is 0V.) The DC voltage is applied by causing MOSFET driver 708 (i.e., 708H, 708L) to turn transistors 704H, 702L on and transistors 702H, 704L off. The receive coil voltage can be used to estimate the capacitance C based on the relationship (1).

[0050] Fig. 8A and Figure 8B The diagram shows monitoring the capacitance in the receiving coil 108 by monitoring the voltage change dV. Figure 8B As shown in FIG. 1 , the receiving coil 108 may be formed on the circuit board 104B and coupled to the control system 104C. The control system 104C may couple a voltage across the combination of the receiving coil 108 and the receiving capacitor Cs. Fig. 8A As shown in FIG. , the capacitance between the receiving coil 108 and the corresponding transmitting coil 106 is given by:

[0051] C=εA / z,

[0052] Where C is the capacitance, A is the overlapping area covered by the receive coil 108 and the transmit coil 106, z is the distance between the two coils, and ε is the dielectric constant of the material (air, housing, cover, etc.) between the receive coil 108 and the transmit coil 106. In particular, the receive coil 108 may be positioned at a particular distance z in a lateral position that maximizes the capacitance.

[0053] Some embodiments of the invention are defined by the following clauses.

[0054] Clause 1 defines a capacitor sensor positioned above a transmitting coil, the capacitor sensor comprising:

[0055] The first set of lines;

[0056] The second set of lines intersects the first set of lines;

[0057] a first multiplexer coupled to the first set of lines, the first multiplexer configured to: provide charge from the battery to the first set of lines, and provide a first signal to a first ADC sample and hold to detect a voltage on each line in the first set of lines; and

[0058] a second multiplexer coupled to the second set of lines, the second multiplexer being configured to: provide charge from the battery to the second set of lines, and provide a second signal to a second ADC sample and hold to detect a voltage on each line in the second set of lines,

[0059] The object is positioned relative to the locations of the first set of lines and the second set of lines.

[0060] 2. A capacitor sensor according to clause 1, wherein the first set of wires and the second set of wires form a grid array.

[0061] 3. A wireless power transmitter, comprising:

[0062] one or more transmitting coils;

[0063] A capacitor sensor positioned above one or more transmitting coils and comprising:

[0064] First line;

[0065] The second line intersects the first line;

[0066] a multiplexer circuit coupled to the first line and the second line, the multiplexer circuit being configured to provide charge from the charge source to the line selected by the multiplexer circuit (e.g., the multiplexer circuits may be 210h and 210v; or the two multiplexers may be replaced with a single MUX with a single output coupled to an ADC or other circuit to monitor a single line at a time; or there may be many multiplexers, each connected to a group of lines 130, and the outputs of the multiplexers may be monitored in parallel, or may be held by a sample-and-hold and monitored one after the other); and

[0067] a monitor circuit (e.g., ADC 240, possibly with monitor 260) for monitoring a discharge rate of each of the first and second lines, the discharge rate of each line depending on the presence of an object proximate to the line and on the transfer of charge between the line and the object (e.g., the discharge rate may be monitored by sensing that the voltage on the sense line drops faster than a threshold rate, or faster than the voltages on other lines; or by sensing that the voltage on the sense line is below a particular threshold, or below the voltages on other lines, at a particular time; such sensing may be accomplished using digital or analog circuitry including a time-to-digital converter, and / or a delay line for sensing the time at which the voltage on the line reaches the threshold, and / or a comparator, and / or some other circuitry);

[0068] The power transmitter is responsive to the monitor circuit during power transfer.

[0069] 4. A wireless power transmitter according to clause 3, wherein monitoring the discharge rate of each line by the monitor circuit comprises: determining whether the voltage of the line has reached a threshold after a predetermined length of time.

[0070] 5. A wireless power transmitter according to clause 3, wherein monitoring the discharge rate of each line by the monitor circuit comprises: comparing the voltage of the line with the voltages of the other lines after each line has been discharged for a predetermined length of time.

[0071] 6. A wireless power transmitter according to clause 3, wherein monitoring the discharge rate of each line by the monitor circuit comprises: determining the length of time it takes for the voltage of the line to reach a predetermined value.

[0072] 7. A wireless power transmitter according to clause 3, wherein monitoring the discharge rate of each line by the monitor circuit comprises: comparing the length of time it takes for the voltage of the line to reach a predetermined value with the length of time it takes for the voltage of the other lines to reach the predetermined value.

[0073] 8. A wireless power transmitter according to any of clauses 3 to 7, wherein the multiplexer circuit comprises:

[0074] a first multiplexer (eg, 210h) coupled to the first line to provide charge from the charge source to the first line selected by the first multiplexer and to couple the selected first line to the monitor circuit; and

[0075] A second multiplexer (eg, 210v) is coupled to the second line to provide charge from the charge source to the second line selected by the second multiplexer and couple the selected second line to the monitor circuit.

[0076] 9. A wireless power transmitter according to any of clauses 3 to 8, configured to ground the first line during power transfer.

[0077] 10. A wireless power transmitter according to any of clauses 3 to 9, comprising a plurality of transmitting coils, wherein the transmitter is configured to: perform power transfer by operating a transmitting coil on which an object to be charged has been detected by a capacitor sensor, but keeping inactive each transmitting coil on which no object to be charged has been detected by a capacitor sensor

[0078] 11. A wireless power transmitter according to any of clauses 3 to 10, wherein the wireless power transmitter is configured to switch off the transmit coil when a foreign object is detected above the transmit coil.

[0079] 12. A wireless power transmission method, comprising:

[0080] charging each of a plurality of first wires and a plurality of second wires, the first wires and the second wires covering one or more transmitting coils;

[0081] monitoring the discharge rate of each of the first and second lines to determine the presence and location of an object adjacent to one or more of the first and second lines; and

[0082] One or more transmit coils are operated in response to the monitoring operation.

[0083] 13. The method of clause 12, wherein monitoring the discharge rate of each line comprises determining whether the voltage of the line has reached a threshold after a predetermined length of time.

[0084] 14. The method of clause 12, wherein monitoring the discharge rate of each line comprises comparing the voltage of the line to the voltages of the other lines after each line has been discharged for a predetermined length of time.

[0085] 15. The method of clause 12, wherein monitoring the discharge rate of each line comprises determining the length of time it takes for the voltage of the line to reach a predetermined value.

[0086] 16. The method of clause 12, wherein monitoring the discharge rate of each line comprises comparing the length of time it takes for the voltage of the line to reach a predetermined value to the length of time it takes for the voltage of the other lines to reach the predetermined value.

[0087] 17. A method according to any of clauses 12 to 16, wherein charging comprises: connecting each line being charged to a charge source using a multiplexer circuit; and

[0088] Monitoring the discharge rate includes coupling each line to a monitor circuit through a multiplexer circuit.

[0089] 18. The method of any of clauses 12 to 17, further comprising: grounding the first line during power transfer.

[0090] 19. A method according to any of clauses 12 to 18, wherein the one or more transmitting coils is a plurality of transmitting coils, and the method comprises: performing the power transfer by operating a transmitting coil on which an object to be charged has been detected using monitoring, but keeping inactive each transmitting coil on which no object to be charged has been detected using monitoring.

[0091] 20. The method according to any of clauses 12 to 19, further comprising switching off the transmitting coil when a foreign object is detected above the transmitting coil.

[0092] 21. A wireless power transfer device, comprising:

[0093] A receiving coil, for receiving a wireless signal and generating a corresponding AC signal;

[0094] a circuit arrangement coupling the receiving coil to a terminal for rectifying the AC signal and providing a rectified DC signal at the terminal (e.g., the circuit arrangement may be IC 104C, possibly having driver 708 and transistors 702, 704; the terminal may be VRECT);

[0095] Wherein the circuit arrangement is operable to monitor capacitance in the receiving coil as a function of a position of the receiving coil relative to another object.

[0096] 22. The device of clause 21, wherein the device is a wireless power receiver.

[0097] 23. Apparatus according to clause 21 or 22, wherein the further object is a transmission coil.

[0098] 24. An apparatus according to any one of claims 21 to 23, wherein monitoring the capacitance comprises applying a voltage to a receiving coil and monitoring the voltage in the receiving coil.

[0099] 25. The apparatus of clause 24, wherein applying voltage to the receiving coil comprises applying voltage to the terminals.

[0100] 26. The device according to clause 25, wherein the circuit arrangement comprises a rectifier, the rectifier comprising:

[0101] one or more transistors coupled between the receive coil and the terminal; and

[0102] a driver circuit device for driving the transistor; and

[0103] Applying the voltage to the receiving coil includes driving the transistor by the driver circuit arrangement to couple the voltage at the terminal to the receiving coil.

[0104] 27. The device according to any one of clauses 21 to 26, wherein the circuit arrangement comprises a rectifier, the rectifier comprising:

[0105] one or more transistors coupled between the receive coil and the terminal; and

[0106] a driver circuit device for driving the transistor; and

[0107] Monitoring the capacitance includes driving a transistor through a driver circuit to apply a voltage to the receiving coil, and monitoring the voltage in the receiving coil.

[0108] The present invention includes a method performed by the above-mentioned device, and a device configured to perform the above-mentioned method. The present invention includes a manufacturing technology for manufacturing the device.

[0109] The above detailed description is provided to illustrate a specific embodiment of the present invention and is not intended to be limiting. Numerous changes and modifications are possible within the scope of the present invention. The present invention is set forth in the appended claims.

Claims

1. A wireless power transmitter, comprising: one or more transmitting coils; a capacitor sensor positioned above the one or more transmitting coils and comprising: First line; a second line intersecting the first line; a multiplexer circuit coupled to the first line and the second line, the multiplexer circuit configured to provide charge from a charge source to a line selected by the multiplexer circuit; and a monitor circuit for monitoring a discharge rate of each of the first and second wires, the discharge rate of each wire being dependent on the presence of an object proximate to the wire and on a charge transfer between the wire and the object; wherein the power transmitter is responsive to the monitor circuit in power transfer; and The power transmitter is configured to ground the first line during power transfer.

2. The wireless power transmitter of claim 1 , wherein monitoring the discharge rate of each line by the monitor circuit comprises: After a predetermined length of time, it is determined whether the voltage of the line has reached a threshold value.

3. The wireless power transmitter of claim 1 , wherein monitoring the discharge rate of each line by the monitor circuit comprises: After each line has been discharged for a predetermined length of time, the voltage of that line is compared to the voltages of the other lines.

4. The wireless power transmitter of claim 1 , wherein monitoring the discharge rate of each line by the monitor circuit comprises: The length of time it takes for the voltage of the line to reach a predetermined value is determined.

5. The wireless power transmitter of claim 1 , wherein monitoring the discharge rate of each line by the monitor circuit comprises: The length of time it takes for the voltage of the line to reach a predetermined value is compared to the length of time it takes for the voltages of the other lines to reach the predetermined value.

6. The wireless power transmitter of claim 1 , wherein the multiplexer circuit comprises: a first multiplexer coupled to the first line to provide charge from the charge source to the first line selected by the first multiplexer and to couple the selected first line to the monitor circuit; as well as A second multiplexer is coupled to the second line to provide charge from the charge source to the second line selected by the second multiplexer and couple the selected second line to the monitor circuit.

7. The wireless power transmitter of claim 1 , wherein the first line being grounded during power transfer creates an EMI filter shield to reduce radiated emissions from at least one of the one or more transmit coils.

8. The wireless power transmitter of claim 1 , wherein the one or more transmitting coils are a plurality of transmitting coils, wherein the transmitter is configured to perform power transfer by operating a transmitting coil on which an object to be charged has been detected by the capacitor sensor, but keeping inactive each transmitting coil on which no object to be charged has been detected by the capacitor sensor. 9 . The wireless power transmitter of claim 1 , wherein the wireless power transmitter is configured to shut down the transmitting coil when a foreign object is detected above the transmitting coil.

10. The wireless power transmitter of claim 7, wherein the EMI filter shield is a comb filter shield.

11. A wireless power transmission method, comprising: charging each of a plurality of first wires and a plurality of second wires, the first wires and the second wires covering one or more transmitting coils, and the second wires intersecting the first wires; monitoring a discharge rate of each of the first and second wires to determine the presence and location of an object proximate one or more of the first and second wires; as well as The one or more transmitting coils are operated in response to the monitoring operation to perform wireless power transfer, and the first line is grounded during the wireless power transfer.

12. The method of claim 11 , wherein monitoring the discharge rate of each line comprises: After a predetermined length of time, it is determined whether the voltage of the line has reached a threshold value.

13. The method of claim 11 , wherein monitoring the discharge rate of each line comprises: After each line has been discharged for a predetermined length of time, the voltage of that line is compared to the voltages of the other lines.

14. The method of claim 11, wherein the one or more transmitting coils is a plurality of the transmitting coils, and the method comprises: The power transfer is performed by operating the transmitting coils on which an object to be charged has been detected using the monitoring, but keeping inactive each transmitting coil on which no object to be charged has been detected using the monitoring.

15. The method of claim 11, wherein during the wireless power transfer, the grounded first line creates an EMI filter shield to reduce radiated emissions from at least one of the one or more transmit coils.

16. The method of claim 11, wherein during the wireless power transfer, the grounded first line creates an EMI comb filter shield to reduce radiated emissions from at least one of the one or more transmit coils.

17. The method of claim 11, further comprising shutting off a transmit coil based on detecting that the object is a foreign object proximate to the transmit coil.

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