Wireless power transfer and communications

Abstract

A wireless power transmission system is provided, the wireless power transmission system including a power transmitter for providing power to a power receiver via an inductive power signal, the wireless power transmission system including the power transmitter, the power transmitter further comprising: a transmitter resonant circuit including a power transmitting inductor having a transmit resonance at a first frequency and arranged to generate the power transmission signal, the power transmitting inductor being arranged to be magnetically coupled to a power receiver inductor in the power receiver; a power transmitter driver operatively coupled to the power transmitting resonant circuit and arranged to generate a drive signal for the power transmitting inductor; and a transmitter communication resonant circuit different from the transmitter resonant circuit and being DC-coupled or capacitively coupled to the power transmitting inductor, the transmitter communication resonant circuit being arranged to establish a transmitter communication resonance at a second frequency different from the first frequency for communication, wherein the power transmitting inductor participates in both the transmit resonance and the transmitter communication resonance, and wherein the transmitter resonant circuit and the transmitter communication resonant circuit are arranged to exhibit the first resonance and the second resonance simultaneously.

Description

Technical Field

[0001] The present invention relates to communication in wireless power transmission, and particularly, but not exclusively, to communication between a power transmitter and a power receiver requiring the transmission of large amounts of data. Background Art

[0002] Most electrical products today require dedicated electrical contacts to obtain power from an external power source. However, this is often impractical and requires the user to physically plug in a connector or otherwise establish physical electrical contact. Typically, power requirements also vary significantly, and most current devices are provided with their own dedicated power supply, so that users typically have a large number of different power sources, each dedicated to a specific device. While using an internal battery can avoid the need for a wired connection to a power source during use, this only provides a partial solution because the battery will need to be recharged (or replaced). Using batteries can also significantly increase the weight and potential cost and size of the device.

[0003] To provide a significantly improved user experience, the use of wireless power supply has been proposed, wherein power is inductively transferred from a transmit inductor in a power transmitter device to a receiver coil in the respective device.

[0004] Power transmission via magnetic induction is a well-known concept, primarily applied to transformers with tight coupling between a primary transmitter inductor / coil and a secondary receiver coil. By separating the primary transmitter coil and the secondary receiver coil between the two devices, wireless power transfer between these devices becomes possible based on the principle of loosely coupled transformers.

[0005] Such an arrangement allows for wireless power transfer to the device without requiring any wires or physical electrical connections. In fact, such an arrangement can simply allow the device to be placed near or on top of the transmitter coil to be recharged or powered externally. For example, the power transmitter device can be placed on a horizontal surface, on which the device can be simply placed to receive power.

[0006] Furthermore, such wireless power transfer arrangements can advantageously be designed so that a power transmitter device can be used with a range of power receiver devices. In particular, a wireless power transfer method known as the Qi specification has been defined and is currently being further developed. This method allows a power transmitter device that complies with the Qi specification to be used with a power receiver device that also meets the Qi specification, without them having to be from the same manufacturer or being specific to each other. The Qi standard also includes certain features for allowing operation to be adapted to a specific power receiver device (e.g., depending on a specific power draw).

[0007] The Qi specification was developed by the Wireless Power Consortium and more information can be found on their website: http: / / www.wirelesspowerconsortium.com / index.html where in particular the defining specification documents can be found.

[0008] Before power transfer can begin, the power transmitter and power receiver need to mutually identify and negotiate the power transfer conditions. This is defined in the Qi specification, as is the communication method using power signal modulation. Because the frequency of the power signal carrier is in the 100kHz region and the system's inertia is significant, the possible data rate is relatively low.

[0009] In some cases, especially with higher power systems, the amount of data that needs to be exchanged becomes large because more checks are required for safety reasons. Summary of the Invention

[0010] Accordingly, the Invention seeks to mitigate, alleviate or eliminate one or more of the above mentioned disadvantages singly or in any combination.

[0011] Thus, there is provided a power transmitter for wirelessly providing power to a power receiver via an inductive power transfer signal, the power transmitter comprising: a transmitter resonant circuit including a power transmitting inductor having a transmit resonance at a first frequency and arranged to generate the power transfer signal, the power transmitting inductor being arranged to be magnetically coupled to a power receiver inductor in the power receiver; a power transmitter driver operatively coupled to the power transmitter resonant circuit and arranged to generate a drive signal for the power transmitting inductor; and a transmitter communication resonant circuit distinct from the transmitter resonant circuit and being DC-coupled or capacitively coupled to the power transmitting inductor and not significantly magnetically coupled to the power transmitter inductor, the transmitter communication resonant circuit being arranged to establish a transmitter communication resonance at a second frequency distinct from the first frequency for communication, wherein the power transmitting inductor participates in both the transmit resonance and the transmitter communication resonance, and wherein the transmitter resonant circuit and the transmitter communication resonant circuit are arranged to simultaneously exhibit the first resonance and the second resonance.

[0012] This arrangement is much less sensitive to the relative placement of the power transmitter and receiver, so there's less risk of communication interruption due to the user moving the receiver. Furthermore, compared to NFC-based systems, design constraints are relaxed, resulting in a simpler overall design for the power transmitter and receiver. In addition to potentially saving components, this can also help reduce overall system cost.

[0013] In an embodiment, power signals and communication signals are transferred via the power transmitting inductor.

[0014] In an embodiment, the power signal and the communication signal can exist simultaneously.

[0015] Since the transmission and communication resonances exist simultaneously, the power transfer signal and the communication signal can exist simultaneously. In addition, the MHz frequency of the communication carrier can provide a much higher bandwidth than the technology using power signal modulation (e.g., load modulation).

[0016] In an embodiment, in the power transmitter, the transmitter communication resonant circuit comprises a transmitter communication inductor (305) arranged to not be substantially magnetically coupled to a receiver communication inductor present in the power receiver.

[0017] Because the communication inductor is not magnetically coupled to any significant extent and the communication signal is transmitted via the power transmitting inductor and the power receiving inductor, the communication signal is less susceptible to perturbations caused by the relative positioning of the power receiver and the power transmitter. In effect, the risk of the communication signal being interrupted by the power receiver is further reduced.

[0018] In an embodiment, the second frequency is at least 7 times greater than the first frequency.A higher carrier frequency allows for higher data rates than load modulation, which in turn allows for more complex negotiation / communication protocols and enhanced security features.

[0019] In an embodiment, the transmitter communication inductor is a separate component from the power transmitting inductor.In a further embodiment, the transmitter communication inductor includes an electromagnetic shield.

[0020] In an embodiment, the transmitter communication inductor is formed from parts of the same inductor that forms the power transmission inductor. This may provide a cost-effective solution as additional components are avoided.

[0021] In an embodiment, there is also a communication driver coupled to the transmitter communication resonant circuit and arranged to generate a communication drive signal. This allows the power transmitter to respond to the power receiver using a high frequency system.

[0022] In an embodiment, the power transmitter further comprises a communications receiver (501) coupled to the transmitter communications resonant circuit and arranged to decode communications signals, thereby allowing it to receive high frequency communications.

[0023] Similarly, a power receiver for wirelessly receiving power via an inductive power transfer signal is provided; the power receiver includes: a power receiving inductor for extracting power from the power transfer signal; a receiver resonant circuit, which is operatively coupled to the power receiving inductor and is arranged to establish a receiving resonance at a first frequency; and a receiver communication resonant circuit, which is different from the receiver resonant circuit and is DC coupled or capacitively coupled to the power receiver inductor and is not significantly magnetically coupled to the power receiver inductor, the receiver communication resonant circuit being arranged to establish a receiver communication resonance at a second frequency different from the first frequency for communication, wherein the power receiver inductor participates in both the receiving resonance and the receiver communication resonance, and wherein the receiver resonant circuit and the receiver communication resonant circuit are arranged to be able to exhibit the first resonance and the second resonance simultaneously.

[0024] In an embodiment, the communication signal is passed via the power receiving inductor.

[0025] In an embodiment, the receiver communication resonant circuit comprises a receiver communication inductor arranged to not be substantially magnetically coupled to a communication inductor present in the power transmitter.

[0026] In an embodiment, the receiver communication inductor is a separate component from the power transmission inductor.

[0027] In an embodiment, the receiver communication inductor comprises an electromagnetic shield.

[0028] In an embodiment, the receiver communication inductor is formed from parts of the same inductor that forms the power receiving inductor.

[0029] In an embodiment, the power receiver further comprises a communication driver coupled to the receiver communication resonant circuit and arranged to generate a communication drive signal.

[0030] In an embodiment, the power receiver further comprises a communication receiver coupled to the receiver communication resonant circuit and arranged to decode the communication signal,

[0031] Also provided is a wireless power transmission system, comprising a power transmitter for providing power to a power receiver via an inductive power signal, the wireless power transmission system comprising: a power transmitter, comprising: a transmitter resonant circuit, comprising a power transmitting inductor having a transmitting resonance at a first frequency and arranged to generate the power transmission signal, the power transmitting inductor being arranged to be magnetically coupled to a power receiver inductor in the power receiver; a power transmitter driver, operatively coupled to the power transmitter resonant circuit and arranged to generate a drive signal for the power transmitting inductor; and a transmitter communication resonant circuit, different from the transmitter resonant circuit, and being DC coupled or capacitively coupled to the power transmitting inductor, the transmitter communication resonant circuit being arranged to establish a transmitter communication resonance at a second frequency different from the first frequency for communication, wherein the power transmitting inductor participates in both the transmitting resonance and the transmitter communication resonance, and wherein the transmitter resonant circuit and the transmitter a receiver communication resonant circuit arranged to exhibit a first resonance and a second resonance simultaneously; and a power receiver comprising: a power receiving inductor for extracting power from the power transfer signal; a receiver resonant circuit operatively coupled to the power receiving inductor and arranged to establish a receive resonance at a first frequency; and a receiver communication resonant circuit different from the receiver resonant circuit and DC-coupled or capacitively coupled to the power receiver inductor, the receiver communication resonant circuit being arranged to establish a second receiver resonance at a second frequency different from the first frequency for communication, and wherein the power receiver inductor participates in both the receive resonance and the receiver communication resonance, and wherein the transmitter resonant circuit and the transmitter communication resonant circuit are arranged to exhibit a first resonance and a second resonance simultaneously, the system being arranged to perform at least part of the communication between the power transmitter and the power receiver using a carrier at the second frequency passed via the power transmitter inductor and the power receiver inductor.

[0032] A wireless power transmission method is also provided, which uses the power transmitter proposed in this article to provide power to the power receiver proposed in this article via an inductive power transmission signal. The method includes: in the power transmitter, generating a drive signal and applying the drive signal to the power transmission inductor to generate a power transmission signal; generating a communication signal by applying a communication drive signal to the power receiver or a second resonant circuit in the power transmitter, wherein the power signal and the communication signal exist simultaneously. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The foregoing as well as additional objects, features and advantages of the disclosed apparatus, system and method will be better understood through the following illustrative and non-limiting detailed description of embodiments of the disclosed apparatus and method with reference to the accompanying drawings, in which:

[0034] Figure 1 A wireless power transfer system is shown.

[0035] Figure 2a and Figure 2b Examples of a half-bridge inverter and a full-bridge inverter are shown.

[0036] Figure 3 FIG. 4 shows a circuit in a wireless power transmitter according to an embodiment.

[0037] Figure 4a and Figure 4b FIG. 4 shows a transfer function curve of a power transmission circuit and a communication circuit in a power transmitter according to an embodiment.

[0038] Figure 5 Circuits of a power transmitter and a power receiver according to an embodiment and arranged for operation are shown.

[0039] Figure 6a and Figure 6b Modifications of the communication circuit according to the embodiment are shown.

[0040] Figure 7 The clocking of signals in a power transmitter according to an embodiment is represented.

[0041] Figure 8 An embodiment of a receiving portion of a communication circuit according to an embodiment is shown.

[0042] Figure 9 Signals including power signals and communication signals in a transmitter and a receiver according to an embodiment are shown. DETAILED DESCRIPTION

[0043] In the following description, the same reference numerals refer to similar elements.

[0044] The following description focuses on embodiments of the invention applicable to wireless power transfer systems utilizing power transfer methods known, for example, from the Qi specification. However, it will be appreciated that the invention is not limited to such applications but may be applied to many other wireless power transfer systems.

[0045] Figure 1An example of a power transfer system 100 according to some embodiments of the present invention is shown. The power transfer system includes a power transmitter 101, which includes (or is coupled to) a transmitter coil / inductor 103. The system also includes a power receiver 105, which includes (or is coupled to) a receiver coil / inductor 107.

[0046] System 100 provides an electromagnetic power signal that can be inductively transmitted from a power transmitter 101 to a power receiver 105. Specifically, the power transmitter 101 generates an electromagnetic signal that is propagated as magnetic flux by a transmitter coil or inductor 103. This power signal can typically have a frequency between about 20 kHz and about 500 kHz, and often in the range of 95 kHz to 205 kHz for Qi-compatible systems (or, for example, in the range of 20 kHz to 80 kHz for high-power kitchen applications). The power transmitting inductor 103 is loosely coupled to the power receiving inductor 107, so that the power receiving coil 107 picks up (at least part of) the power transmission signal from the power transmitter 101. Thus, power is transferred from the power transmitter 101 to the power receiver 105 via wireless inductive coupling from the transmitter coil 103 to the power receiving coil 107. The term power signal is primarily used to refer to the induced signal / magnetic field (magnetic flux signal) between the transmitter coil 103 and the power receiving coil 107, but it will be appreciated that, in an equivalent manner, the term power signal may also be considered and used as a reference to the electrical signal provided to the transmitter coil 103 or picked up by the power receiving coil 107.

[0047] In the example, the power receiver 105 is a power receiver that receives power via a receiver coil 107. However, in other embodiments, the power receiver 105 may comprise a metallic element, such as a metallic heating element, in which case the power signal directly induces eddy currents, resulting in direct heating of the element.

[0048] The system 100 can be arranged to transmit considerable power levels, and in particular, in many embodiments, the power transmitter 101 can support power levels exceeding 500 mW, 1 W, 5 W, 50 W, 100 W, or 500 W. For example, for Qi-compliant applications, power transmission can typically be in the power range of 1-5 W for low-power applications (basic power profile); for Qi specification version 1.2, power transmission can reach up to 15 W; for higher power applications (e.g., power tools, laptops, drones, robots, etc.), power transmission can reach up to 100 W; and for ultra-high power applications (e.g., kitchen applications), power transmission can exceed 100 W and reach over 1000 W.

[0049] Hereinafter, the operation of the power transmitter 101 and the power receiver 105 will be described with specific reference to embodiments generally in accordance with the Qi specification (except for the modifications and enhancements described herein (or arising therefrom)) or embodiments suitable for use with the higher power kitchen specification developed by the Wireless Power Consortium. In particular, the power transmitter 101 and the power receiver 105 may conform to elements of or be substantially compatible with the Qi specification versions 1.0, 1.1, or 1.2 (except for the modifications and enhancements described herein (or arising therefrom)).

[0050] Figure 2a A schematic diagram of a half-bridge switching bridge / inverter as used in an embodiment of power transmitter 101 is shown. A DC voltage is applied across input terminals V+ and V-. Switches S1 and S2 are controlled so that they are never closed simultaneously. Instead, S1 is closed while S2 is open, and S2 is closed while S1 is open. These switches open and close at the desired frequency, generating an AC signal at the output. Typically, the output of the inverter is connected to the power transmitting inductor 103 via a resonant capacitor, Cres.

[0051] Figure 2b A schematic diagram of a full-bridge switching bridge / inverter as used in an embodiment of power transmitter 101 is shown. A DC voltage is applied across input terminals V+ and V-. In some operating modes, switches S1 and S2 are controlled so that they are never closed at the same time. Switches S3 and S4 are controlled so that they are never closed at the same time. Alternatively, switches S1 and S4 are closed while S2 and S3 are open, and then S2 and S3 are closed while S1 and S4 are open, creating a square wave signal at the output. These switches open and close at the desired frequency. In another operating mode, S1 and S3 are open, and for a portion of the time S2 and S4 are closed, and vice versa. This is often referred to as phase control. These arrangements produce a square wave-like output, which in this case becomes the power signal carrier frequency. The inductive effect of the power transmitter inductor 103 is to transform it into a near-sine wave. However, because the switches in the inverter have finite open and close times, the current flowing directly from V+ to V- is very brief, resulting in spikes at the zero crossings of the power signal's sine wave. In the frequency domain, these spikes appear as high-frequency components of the power signal. For power transfer, these spikes can be filtered out by the receiver resonant circuit and any other necessary filtering.

[0052] For high power systems (e.g., systems transferring 100W of power), the power transmitter and the power receiver typically establish a communication channel in order to perform control of the wireless power transfer and / or perform authentication or other auxiliary data transmission between the power receiver and the power transmitter.

[0053] A parallel (out-of-band) communication channel could be used, such as NFC. However, this raises a number of issues.

[0054] For NFC to work, the NFC antenna needs to be well aligned. In the case of a wireless kitchen, for example, the user might move the power receiver. While this repositioning might be within the acceptable range for power transfer, it could disrupt the NFC field enough to disrupt any NFC communication that happens to be occurring at that moment. This can cause errors at the system control level, leading to a reset of power transfer.

[0055] The NFC antenna must be positioned so that it is not affected by the power transfer inductor 103 , 107 (transmit or receive). This places additional design constraints on the power transmitter 101 or the power receiver 105 .

[0056] Importantly, NFC systems can only operate when the power signal is below a relatively low level.

[0057] Finally, NFC systems carry cost implications associated with the hardware and other considerations that skilled artisans will be aware of.

[0058] Therefore, a solution that addresses the above-mentioned problems is desired.

[0059] Figure 3 Exemplary elements of a power transmitter are illustrated, particularly a resonant circuit associated with the power transmitting inductor 103 .

[0060] Capacitor 301(C P ) is connected between the power transmitting inductor 103 and the power transmitter driver 303 (PTSDRV). The power transmitter driver 303 may include components, such as Figure 2a and Figure 2b The capacitor 301 and the power transmission inductor 103 form a first (series) resonant circuit. Typically, the carrier of the power signal is between 20kHz and 300kHz. Therefore, the resonant circuit (transmitter resonant circuit) can have a resonant frequency CO within this range. P , for example, 100kHz, which is somewhere around the frequency of the power signal carrier. The second inductor 305 (transmitter communication inductor L C) is coupled between the power transmitting inductor 103 and the lower reference potential. In this example, it is desirable to direct current (in other words, DC) couple or capacitively couple the transmitter communication inductor 305 to the power transmitting inductor 103.

[0061] The coupling point of the power transmission inductor 103 and the transmitter communication inductor 305 is coupled to a capacitor 307 (C C ), capacitor 307 is then coupled to resistor 309 (R C ). The other terminal of resistor 309 is connected to a transmitter communication driver 311 (TCDRV). A transmitter communication receiver 312 is coupled between capacitor 307 and resistor 309. Transmitter communication receiver 312 (TCRCV) is arranged to detect, demodulate, and decode communication signals. A power transmitter controller 313 (PTCTRL) is connected to power transmitter driver 303, transmitter communication driver 311, and transmitter communication receiver 312 to control the generation of power signals and communication with power receiver 105.

[0062] The second (series) resonant circuit (transmitter communication resonant circuit) comprises the transmitter communication inductor 305, capacitor 307, resistor 309 and the power transmission inductor 103. The carrier frequency conveniently chosen for the communication signal will be ten times higher than the power signal carrier (if not higher). Thus, in the present example, the resonant frequency CO of the transmitter communication resonant circuit is C It may be in the MHz range, for example, about 1.1 MHz. Communications are relatively high "high frequency".

[0063] Both the power transmitter driver 303 and the transmitter communication driver 311 are referenced to a lower reference or lower reference potential.

[0064] Figure 4a The transmission curve of the transmitter resonant circuit is shown. The first trace 401 shows the magnitude of the system response as a function of frequency, and the second trace 403 shows the phase. There is a peak 405 in power transfer at or near the resonance of the transmitter resonant circuit (around 100 kHz).

[0065] Figure 4b The transmission curves of the transmitter communication resonant circuit are shown. The first trace 407 shows the magnitude of the system response as a function of frequency, and the second trace 409 shows the phase. There is a peak 411 in power transfer at the resonance of the transmitter communication resonant circuit (around 1.1 MHz).

[0066] Thus, a power transmitter 101 for wirelessly providing power to a power receiver 103 via an inductive power transfer signal comprises:

[0067] a transmitter resonant circuit comprising a power transmitting inductor having a transmitting resonance at a first frequency and arranged to generate the power transfer signal, the power transmitting inductor being arranged to be magnetically coupled to (i.e., can be magnetically coupled to) a power receiver inductor in the power receiver; a power transmitter driver 303 operatively coupled to the power transmitter resonant circuit and arranged to generate a drive signal for the power transmitting inductor 103; a transmitter communication resonant circuit distinct from the transmitter resonant circuit and being DC coupled or capacitively coupled to the power transmitting inductor; an inductor, the transmitter communication resonant circuit being arranged to establish a transmitter communication resonance at a second frequency different from the first frequency for communication; and a communication circuit coupled to the second transmitter resonant circuit and arranged to generate a communication drive signal, wherein the power transmitting inductor 103 participates in both the transmitting resonance and the transmitter communication resonance, and wherein the transmitter resonant circuit and the transmitter communication resonant circuit (301+103 and 305+307+309+103, respectively, in this example) are arranged to simultaneously exhibit the first resonance and the second resonance.

[0068] Figure 5 1 shows a power transmitter 101 and a power receiver 103 and their elements arranged to perform power transfer and communication according to an embodiment. Figure 3 The elements of the power transmitter 101 have been discussed and will not be described again.

[0069] On the power receiver 103 side, the power receiving inductor 107 is connected to the power receiving inductor 107 via the capacitor 505 (C P) is coupled to a receiver controller 507 (RCVCTRL), where capacitor 505 is also coupled to a lower reference potential via capacitor 506. It should be noted that the lower reference potential in power transmitter 103 is not directly connected to the lower reference potential in power receiver 105, and the absolute value of each reference potential may be completely different relative to the actual situation. Power receiving inductor 107 and capacitor 505 are used for the first resonant circuit on the receiver side—the receiver resonant circuit. Receiver controller 507 extracts power from the power signal captured by power receiving inductor 107 using the receiver resonant circuit. In a manner similar to power transmitter 103, the receiver resonant circuit has a resonant frequency in the range of 20-200 kHz (e.g., approximately 100 kHz). It is desirable that the resonant frequencies of the transmitter resonant circuit and the receiver resonant circuit be the same. Receiver controller 507 is coupled to load 509, to which it supplies power. The coupling of the receiver controller to the load 509 comprises switch connections and / or other elements that allow load modulation as seen by the power receiving inductor.This coupling will not be discussed here and is within the capabilities of the skilled person to implement.

[0070] Receiver communication inductor 511 (L C ) is coupled between the power receiving inductor 107 and the lower reference or lower reference potential. In this example, it is expected that this coupling is either direct current (DC) coupling or capacitive coupling. The coupling point of the power receiver inductor 103 and the receiver communication inductor 511 is coupled to the capacitor 313 (C C ), capacitor 313 is in turn coupled to resistor 515. The other terminal of resistor 515 is coupled to a receiver communication driver 517 (RCDRV).

[0071] In a manner similar to that of the power transmitter 103, the second resonant circuit (receiver communication resonant circuit) includes a receiver communication inductor 511, a capacitor 313, a resistor 515, and a power receiving inductor 107. The resonant frequency of the receiver communication resonant circuit may be in the MHz range, for example, approximately 1.1 MHz.

[0072] A receiver communication receiver 519 (RCRCV) is coupled to the receiver communication resonant circuit and is arranged to demodulate and decode communication signals via the receiver communication resonant circuit.

[0073] Because the power transmitting inductor 103 participates in the transmitter communication resonant circuit, it is possible to transmit a communication signal using a carrier frequency near the resonance of the transmitter communication resonant circuit (i.e., in the MHz range). Therefore, the power signal and the communication signal can be transferred via the power transmitting inductor, and the power signal and the communication signal can exist simultaneously.

[0074] Thus, a power receiver (103) for wirelessly receiving power via an inductive power transfer signal may include: a power receiving inductor (107) for extracting power from the power transfer signal; a receiver resonant circuit operatively coupled to the power receiving inductor and arranged to establish a receive resonance at a first frequency; a receiver communication resonant circuit operatively coupled to the power receiving inductor (107) and arranged to establish a second receiver resonance at a second frequency, the receiver communication resonant circuit being different from the receiver resonant circuit and being DC-coupled or capacitively coupled to the power receiver inductor (107), the receiver communication resonant circuit being arranged to establish a receiver communication resonance at a second frequency different from the first frequency for communication; and a receiver communication driver (517) coupled to the second receiver communication resonant circuit and arranged to generate a communication drive signal, wherein the power receiver inductor (107) participates in both the receive resonance and the receiver communication resonance, and wherein the receiver resonant circuit and the receiver communication resonant circuit are arranged to exhibit both the first resonance and the second resonance simultaneously.

[0075] like Figure 5 As shown, the power transmission inductor and the receiving inductor 107 are magnetically coupled. In many cases, the inductive coupling factor, k, of this coupling is in the range of 0.2 to 0.8. However, for the communication inductors 305 and 511, it is desirable that they have no significant magnetic coupling with the corresponding "power" inductors 103 and 107, or with each other. This situation would create the risk of generating anti-phase communication signals in one or both of the communication inductors 305 and 511, resulting in unpredictable effects and potentially degrading the communication signal. More importantly, it is intended that communication signals be transferred via the transmitter inductor 103 and the receiver inductor 107 and their magnetic coupling. "No significant magnetic coupling" means that magnetic coupling of less than 1% is sufficiently low for acceptable performance, and magnetic coupling of less than 0.1% is desirable. The level of magnetic coupling can be checked by looking for the presence of a measurable anti-phase communication signal.

[0076] This arrangement has multiple advantages.

[0077] Because the communication inductors 305 and 511 are not magnetically coupled and do not transmit communication signals to any significant extent via the power transmitting inductor 103 and the power receiving inductor 107, the communication signals are less susceptible to being disturbed by the relative positioning of the power receiver 103 and the power transmitter 101. This effectively reduces the risk of interrupting the communication signal due to movement of the power receiver 103.

[0078] Because the transmit resonance and the communication resonance exist simultaneously, the power transfer signal and the communication signal can exist simultaneously. In addition, the MHz frequency of the communication carrier can provide a much higher bandwidth than the technology using power signal modulation (eg, load modulation).

[0079] Furthermore, compared to NFC-based systems, design constraints are relaxed, making the overall design of the power transmitter 101 and the power receiver 103 simpler. In addition to the potential savings in components, this can also help reduce the overall system cost.

[0080] The signal flow will now be discussed with reference to the power transmitter 103, but a similar analysis can also be applied to the power receiver 103. The power signal carrier flows through path C P -L P -L C , i.e., 301-103-305. At the carrier frequency of the power signal ("low frequency"), capacitor 307 (C C ) has a high impedance, and the communication inductor 305 (L C ) is much lower. For example, when the power signal carrier frequency differs by about ten times from the communication signal carrier frequency, the capacitor 307C at low frequency C With the communication inductor 305 (L C ) can be about 40dB. This has the limitation that resistor 309 (R C )—the ideal effect of the amplitude of the power signal seen by the communications driver / receiver circuitry. The greater this amplitude, the greater the dynamic range over which communications receiver 501 must be able to distinguish the communications signal from the power signal. This consideration for communications-to-power isolation allows for at least a factor of ten difference in the desired carrier frequency.

[0081] The current supplied from the communication driver 311 flows through the path R C -C C , and in L C With L P Although most of the current flows through L C flows downwards towards the lower reference potential, but some current flows through path L P -C P -C P- Power transmission driver 303 (or receiver controller 507). The amount of this current may be less than 20%. Nevertheless, the current of the communication carrier flowing through the power transmission inductor 103 may be only a few percent of the current flowing through the communication inductor 305. The current due to the communication carrier in the power transmission inductor 103 can be given as follows:

[0082]

[0083] In this example, at the carrier frequency, capacitor 307 (C P ) and the impedance of the driver 303 is low, thereby effectively transmitting the power to the inductor 103 (L P ) to a lower reference. In this example, the amplitude of the communication carrier can be 5% or less of the power signal carrier. Moreover, the communication carrier current in the power transmission inductor 103 is only a few percent of the communication carrier current in the communication inductor 305. Nevertheless, this current can also be detected on the receiving side. Therefore, the power signal carrier and the low-level communication carrier can be independently and simultaneously present in the power transmission inductor 103 (or 107 for the power receiver).

[0084] As mentioned previously, it is desirable that any inductive coupling seen by the communication inductor 305 / 511 be very small or negligible. This is also to ensure that the desired signal flow can be achieved.

[0085] Due to the nature of driver 303 (as discussed with respect to FIG. 2 ), there are high-frequency spikes at the zero crossings of the power signal. For the purposes of the communication signal, these spikes can be in-band. If the Q factor of the communication resonant circuit is too high, these spikes can cause oscillations in the communication resonant circuit. This, in turn, will require additional damping to be able to decode the communication signal. Therefore, the Q factor of the communication resonant circuit is low, preferably below 20.

[0086] In an embodiment, the transmitter communication inductor 305 may be a separate component (eg, a surface mounted component) from the power transmitting inductor 103. This has the advantage that it is small and can be relatively freely positioned.

[0087] In an embodiment, the transmitter communication inductor 305 includes electromagnetic shielding. The shielding can provide improved isolation and reduce the risk of undesired coupling with one or more of the other inductors.

[0088] In an embodiment, the power transmission inductor 103 is formed from a coil, and the transmitter communication inductor 305 is formed from a portion of the same inductor, for example by coupling the capacitor 307 to a point somewhere along the length of the coil. This point should be chosen to achieve the desired two inductance values. Such calculations are within the skill of the art. It is also desirable to choose the length of the communication-related portion and the overall layout so that the communication-related portion does not find itself positioned in a way that it could be magnetically coupled to an inductor in the power receiver (e.g., by being closely aligned with and approximately parallel to the other inductors).

[0089] In an embodiment, the receiver communication inductor 511 may be a separate component from the power transmission inductor 103 , such as a surface mounted component.

[0090] In an embodiment, the receiver communication inductor 511 includes electromagnetic shielding.

[0091] In an embodiment, the power receiving inductor 107 is formed by a coil, and the transmitter communication inductor 511 is formed by a portion of the same inductor, for example by coupling the capacitor 513 to a point somewhere along the length of the coil. This point should be chosen to achieve the desired two inductance values. Such calculations are within the skill of the art. It is also desirable to choose the length of the communication-related portion and the overall layout so that the communication-related portion does not find itself positioned in a situation where it could be magnetically coupled to the inductor in the power receiver (e.g., by being closely aligned with and approximately parallel to the other inductors).

[0092] In a wireless power transmission system, there may be a power transmitter (101) according to an embodiment for providing power to a power receiver (103) according to an embodiment via an inductive power transmission signal. In one aspect, the power transmitter comprises: a transmitter resonant circuit comprising a power transmission inductor (103) having a transmission resonance at a first frequency and arranged to generate the power transmission signal, the power transmission inductor being arranged to be magnetically coupled to a power receiver inductor (107) in the power receiver (103); a power transmitter driver (303) operatively coupled to the power transmitter resonant circuit and arranged to generate a drive signal for the power transmission inductor (103); a transmitter communication resonant circuit, which is different from the transmitter resonant circuit , and is DC-coupled or capacitively coupled to the power transmitting inductor, the transmitter communication resonant circuit being arranged to establish a transmitter communication resonance at a second frequency different from the first frequency for communication; a transmitter communication receiver (501) coupled to the second transmitter resonant circuit and arranged to extract information from a communication signal, wherein the power transmitting inductor (103) participates in both the transmitting resonance and the transmitter communication resonance, and wherein the transmitter resonant circuit and the transmitter communication resonant circuit are arranged to be able to exhibit a first resonance and a second resonance simultaneously. On the other hand, the power receiver (103) includes: a power receiving inductor (107) for extracting power from the power transmission signal; a receiver resonant circuit operatively coupled to the power receiving inductor (107) and arranged to establish a receiving resonance at a first frequency; a receiver communication resonant circuit operatively coupled to the power receiving inductor and arranged to establish a second receiver resonance at a second frequency, the receiver communication resonant circuit being different from the receiver resonant circuit and being DC coupled or capacitively coupled to the power receiver inductor (107), the receiver communication resonant circuit being arranged to establish a second receiver resonance at a second frequency different from the first frequency for communication; and a receiver communication driver (517) coupled to the second receiver communication resonant circuit and arranged to generate a communication drive signal, wherein the power receiver inductor (107) participates in both the receiving resonance and the receiver communication resonance, and wherein the receiver resonant circuit and the receiver communication resonant circuit are arranged to exhibit both the first resonance and the second resonance simultaneously.

[0093] The system may be arranged to perform at least part of the communication between the power transmitter and the power receiver using a carrier wave at the second frequency passed via the power transmitter inductor and the power receiver inductor.

[0094] By virtue of the transmission resonance and communication resonance present in both the power transmitter 103 and the power receiver 105, a power transmitter according to an embodiment can be used to provide power to a power receiver according to an embodiment via an inductive power transfer signal, wherein the use includes: in the power transmitter, a drive signal is generated and applied to a power transmission inductor to generate a power signal; and in the power transmitter 103 or the power receiver 105, a communication signal is generated by applying the communication drive signal to a second resonant circuit in the power receiver or the power transmitter, wherein the power signal and the communication signal (“high frequency” signal) exist simultaneously.

[0095] In wireless power systems with an in-band communication channel, the typical communication method from the power receiver 105 to the power transmitter 103 is load modulation. One advantageous solution is to use relative load modulation, which can be achieved by generating a high-frequency carrier on the power receiver 105 side. This allows the power receiver 105, which only has a single high-frequency carrier modulator, to communicate with the power transmitter 103 both with and without a high-frequency demodulator. The modulation of the power signal will be "similar" to the load modulation of a power transmitter with only the Tow frequency (the older load modulation). Therefore, a power receiver with a high-frequency modulator can still communicate with the "older" power transmitter.

[0096] For example, at the start of negotiation, initial communication can be performed using known load modulation techniques applied to the power signal ("low frequency"). Portions of these communications can be used to determine whether the power transmitter 103 and the power receiver 105 are capable of supporting the "high frequency" communication described herein, and whether this is unidirectional (simplex) or bidirectional (duplex). If this is determined to be the case, the power transmitter 103 and the power receiver 105 can move to using the "high frequency" method.

[0097] Figure 6a and Figure 6b 1 shows a communication circuit according to an embodiment. Figure 6a In FIG, the communication receiver 501 / 519 is coupled between the capacitor 307 / 513 and the resistor 309 / 515. A bidirectional switch 601 is provided between the resistor 309 / 515 and the communication driver 311 / 517. When the communication circuit is in receive mode, the bidirectional switch 601 can be used to disconnect the communication driver 311 / 517. The common terminal of the switch 601 is coupled to the resistor 309 / 515, one switching terminal of the switch 601 is coupled to the communication driver 311 / 517, and the other switching terminal of the switch 601 is connected to a lower reference potential. Figure 6bAnother embodiment is shown in which the common terminal of the switch 601 is coupled to the capacitor 307 / 513. One switch terminal is coupled to the first resistor 309 / 515 and the other switch terminal is coupled to the second resistor 603 which in turn is connected to a lower reference potential.

[0098] Both arrangements provide for semi-bidirectional communication.The desired information may be modulated onto the communication carrier signal by a variety of modulation schemes (eg, amplitude keying, phase / frequency shift keying, quadrature modulation, or other techniques).

[0099] In an embodiment, communication is unidirectional from power receiver 105 to power transmitter 101. Power transmitter 103 only has communication receiver 312, and power receiver 105 does not have communication receiver 519. In this case, the terminal of resistor 309, which has been shown as being connected to communication driver 311, should be connected to the lower reference potential. In an embodiment with unidirectional communication in the other direction, it is resistor 515 that will be connected to the lower reference potential of power receiver 105.

[0100] Figure 7 This shows advantageous relative timing of the power transmission drive signals 701 and 703. As previously mentioned, there are (relatively) high frequency spikes at the zero crossings of the power signal. For the purposes of the communication signal, these spikes can be within the frequency band. Therefore, it can be useful to limit the modulation of the communication carrier to one half or the other of the power transmission drive signal 701, rather than modulating the communication signal during the zero crossings.

[0101] Figure 8 An embodiment of a detector circuit for an on-off keyed modulated signal is shown. The incoming signal (VM2) passes through a high-pass filter 801 and then through an amplifier (or comparator?) 803 to a recovery circuit comprising a 4-bit counter 805 and a retriggerable multivibrator 807, which is arranged to reset the counter 805. The counter output is then fed to another retriggerable multivibrator 809 to recover the original modulation. The advantage of this arrangement is that the number of carrier cycles per bit can be varied without imposing constraints on the duty cycle of the power signal carrier. The recovered modulation can then be decoded to recover the information.

[0102] Figure 91 and 2. Example waveforms of modulation and detection related to the previously described embodiments are shown. Trace 901 shows the unrectified AC power output of the system, i.e., the voltage across capacitor 506. Trace 903 shows the output of the detector of multivibrator 809. Trace 905 shows the output of counter 805. Trace 907 shows the carrier detector signal, which is the output of multivibrator 807. Trace 909 shows the pulse recovered from comparator 803. Trace 911 shows the input to the high-pass filter. Finally, trace 913 shows the power signal driver signal with the communication input signal modulation (for visualization) superimposed thereon.

[0103] It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

[0104] In the claims, any reference signs placed between brackets shall not be construed as limiting the claim. The use of the verb "comprise" and its conjugations does not exclude the presence of other elements or steps than those stated in the claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several different elements, and by means of a suitably programmed computer or processing unit. In a device claim enumerating several units, several of these units may be implemented by one and the same item of hardware. The fact that certain measures are stated in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0105] Various aspects of the present invention can be implemented in a computer program product, which can be a set of computer program instructions stored on a computer-readable storage device that can be run by a computer. Instructions of the present invention can be in any interpretable or executable code mechanism, including but not limited to scripts, interpretable programs, dynamic link libraries (DLLs) or Java classes. These instructions can be provided as complete executable programs, partial executable programs, modifications (for example, updates) to existing programs or expansions (for example, plug-ins) to existing programs. In addition, the part of processing of the present invention can be distributed on multiple computers or processors.

[0106] Storage media suitable for storing computer program instructions include all forms of non-volatile memory, including but not limited to EPROM, EEPROM and flash memory devices, magnetic disks (e.g., internal and external hard drives, removable disks and CD-ROM disks). Computer program products may be distributed on such storage media or provided by downloading via HTTP, FTP, email or a server connected to a network (e.g., the Internet).

Claims

1. A power transmitter (101) for wirelessly providing power to a power receiver (503) via an inductive power transfer signal, the power transmitter (101) comprising: a transmitter resonant circuit comprising a power transmitting inductor (103) having a transmit resonance at a first frequency and arranged to generate the power transfer signal, the power transmitting inductor being arranged to be magnetically coupled to a power receiving inductor in the power receiver; a power transmitter driver (303) operatively coupled to the power transmitter resonant circuit and arranged to generate a drive signal for the power transmitting inductor (103); as well as a transmitter communication resonant circuit distinct from the transmitter resonant circuit, wherein the transmitter communication resonant circuit includes a transmitter communication inductor (305) and shares the power beaming inductor (103) with the transmitter resonant circuit, wherein the transmitter communication inductor (305) is DC coupled or capacitively coupled to the power beaming inductor (103) and is not significantly magnetically coupled to the power transmitter inductor (103), and wherein the transmitter communication resonant circuit is arranged to establish a transmitter communication resonance at a second frequency distinct from the first frequency for communication, wherein the power transmitting inductor (103) participates in both the transmitting resonance and the transmitter communication resonance, and wherein the transmitter resonant circuit and the transmitter communication resonant circuit are arranged to exhibit a first resonance and a second resonance simultaneously.

2. The power transmitter according to claim 1, wherein: Power signals and communication signals are transferred via the power transmitting inductor.

3. The power transmitter according to any one of claims 1 or 2, wherein: Power signals and communication signals can exist at the same time.

4. The power transmitter according to claim 1, wherein: The transmitter communication inductor (305) is arranged to not be substantially magnetically coupled to a receiver communication inductor present in a power receiver.

5. The power transmitter according to claim 1, wherein: The second frequency is at least 7 times the first frequency.

6. The power transmitter according to claim 1, wherein: The transmitter communication inductor is a separate component from the power transmitting inductor.

7. The power transmitter according to claim 1, wherein: The transmitter communication inductor includes an electromagnetic shield.

8. The power transmitter according to claim 1, wherein: The transmitter communications inductor is formed from portions of the same inductor that forms the power transmitting inductor.

9. The power transmitter of claim 1, further comprising a communication driver coupled to the transmitter communication resonant circuit and arranged to generate a communication drive signal.

10. The power transmitter of claim 1, further comprising a communication receiver (501) coupled to the transmitter communication resonant circuit and arranged to decode communication signals.

11. A power receiver for wirelessly receiving power via an inductive power transfer signal; the power receiver (503) comprising: a receiver resonant circuit comprising a power receiving inductor (107) and arranged to establish a receiving resonance at a first frequency and capture the power transfer signal; a receiver controller (507) for extracting power from the power transfer signal; as well as a receiver communication resonant circuit distinct from the receiver resonant circuit, wherein the receiver communication resonant circuit includes a receiver communication inductor (511) and shares the power receiving inductor (107) with the receiver resonant circuit, wherein the receiver communication inductor (511) is DC coupled or capacitively coupled to the power receiving inductor (107) and is not significantly magnetically coupled to the power receiving inductor (107), and wherein the receiver communication resonant circuit is arranged to establish a receiver communication resonance at a second frequency distinct from the first frequency for communication, wherein the power receiving inductor (107) participates in both the receiving resonance and the receiver communication resonance, and wherein the receiver resonant circuit and the receiver communication resonant circuit are arranged to exhibit a first resonance and a second resonance simultaneously.

12. The power receiver according to claim 11, wherein: A communication signal is transferred via the power receiving inductor.

13. The power receiver according to claim 11, wherein: The receiver communication inductor (511) is arranged to not be substantially magnetically coupled to a communication inductor present in the power transmitter.

14. The power receiver according to claim 11, wherein: The receiver communication inductor (511) is a separate component from the power receiving inductor (107).

15. The power receiver according to claim 11, wherein: The receiver communication inductor includes an electromagnetic shield.

16. The power receiver according to claim 11, wherein: The receiver communications inductor is formed from portions of the same inductor that forms the power receiving inductor.

17. The power receiver of claim 11, further comprising a communication driver coupled to the receiver communication resonant circuit and arranged to generate a communication drive signal.

18. The power receiver of claim 11, further comprising a communication receiver (519) coupled to the receiver communication resonant circuit and arranged to decode communication signals.

19. A wireless power transmission system comprising a power transmitter (101) for providing power to a power receiver (503) via an inductive power signal, the wireless power transmission system comprising: The power transmitter (101) comprises: a transmitter resonant circuit comprising a power transmitting inductor (103) having a transmit resonance at a first frequency and arranged to generate a power transfer signal, said power transmitting inductor being arranged to be magnetically coupled to a power receiving inductor (107) in said power receiver (503); a power transmitter driver (303) operatively coupled to the power transmitter resonant circuit and arranged to generate a drive signal for the power transmitting inductor (103); and a transmitter communication resonant circuit distinct from the transmitter resonant circuit, wherein the transmitter communication resonant circuit includes a transmitter communication inductor (305) and shares the power beaming inductor (103) with the transmitter resonant circuit, wherein the transmitter communication inductor is DC coupled or capacitively coupled to the power beaming inductor and is not significantly magnetically coupled to the power transmitter inductor, the transmitter communication resonant circuit being arranged to establish a transmitter communication resonance at a second frequency distinct from the first frequency for communication, wherein the power transmitting inductor (103) participates in both the transmitting resonance and the transmitter communication resonance, and wherein the transmitter resonant circuit and the transmitter communication resonant circuit are arranged to exhibit a first resonance and a second resonance simultaneously; and The power receiver (503) comprises: a receiver resonant circuit comprising a power receiving inductor (107) and arranged to establish a receiving resonance at a first frequency and capture the power transfer signal; a receiver controller (507) for extracting power from the power transfer signal; and a receiver communication resonant circuit distinct from the receiver resonant circuit, wherein the receiver communication resonant circuit includes a receiver communication inductor (511) and shares the power receiver inductor (107) with the receiver resonant circuit, wherein the receiver communication inductor (511) is DC coupled or capacitively coupled to the power receiver inductor (107) and is not significantly magnetically coupled to the power receiver inductor (107), the receiver communication resonant circuit being arranged to establish a second receiver resonance at a second frequency distinct from the first frequency for communication, and wherein the power receiver inductor (107) participates in both the receive resonance and the receiver communication resonance, and wherein the receiver resonant circuit and the receiver communication resonant circuit are arranged to exhibit a first resonance and a second resonance simultaneously, The system is arranged to perform at least part of the communication between the power transmitter and the power receiver using a carrier wave at the second frequency passed via the power transmitter inductor and the power receiver inductor.

20. A wireless power transmission method, using a power transmitter according to any one of claims 1 to 10 to provide power to a power receiver according to any one of claims 11 to 18 via an inductive power transfer signal, the method comprising: In the power transmitter, generating a drive signal and applying the drive signal to the power transmitting inductor to generate a power transfer signal; A communication signal is generated by applying a communication drive signal to a receiver communication resonant circuit in the power receiver or a transmitter communication resonant circuit in the power transmitter, wherein the power signal and the communication signal exist simultaneously.

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