Wireless power transmission

Abstract

The power transmitter 101 comprises a driver 201 generating a drive signal for an output resonant circuit comprising a transmitter coil 103 generating a power transfer signal. A resonance detector 307 determines a coupled resonant frequency of the output resonant circuit, the coupled resonant frequency being a resonant frequency of the output resonant circuit of the transmitter coil 103 coupled to a receiver coil 107 which is part of a power transfer input resonant circuit of the power receiver 105. The quality factor of the input resonant circuit is 10 or greater. An estimation circuit 309 determines an estimate of a coupling coefficient for the coupling between the transmitter coil 103 and the receiver coil 107 depending on the first effective resonant frequency and, as the case may be, the uncoupled resonant frequency of the output resonant circuit or the input resonant circuit. An adapter 311 sets operating parameters depending on the estimate of the coupling coefficient.

Description

[Technical Field]

[0001] The present invention relates to a wireless power transmission system, and more particularly, but not limited to, the operation of a power transmitter that enables inductive power transmission to high-power devices such as kitchen electrical appliances. [Background technology]

[0002] Most modern electrical devices require dedicated electrical contacts to be powered from an external power source. However, this is often impractical, as the user must physically insert a connector or otherwise establish physical electrical contact. Power requirements also vary considerably, and since most devices now have dedicated power supplies, the average user often owns numerous different power supplies, each dedicated to a specific device. While using an internal battery eliminates the need for a wired connection to a power source during use, it only offers a partial solution, as it requires recharging (or replacement). Furthermore, using a battery significantly increases the weight, and in some cases the cost and size, of the device.

[0003] To provide a significantly improved user experience, the use of wireless power supplies is proposed, in which power is inductively transmitted from the transmitter inductor of a power transmitter device to the receiver coil of individual devices.

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

[0005] This configuration makes it possible to wirelessly transmit power to a device without the need for any wires or physical electrical connections. In fact, wireless power transmission allows a device to be recharged or powered externally simply by placing it adjacent to or on top of the transmitter coil. The power transmitter device is positioned, for example, with a horizontal surface on which a device can be simply placed for power supply.

[0006] Such wireless power transmission devices are further advantageous because the power transmitter devices are designed to be used with a variety of power receiver devices. In particular, a wireless power transmission method known as the Qi specification has been defined and is currently under further development. This method allows a power transmitter device that conforms to the Qi specification to be used with a power receiver device that also conforms to the Qi specification, and these devices do not need to be from the same manufacturer or be dedicated to each other. The Qi standard further includes several features that allow the operation to be adapted to a specific power receiver device (for example, depending on a specific power consumption).

[0007] The Qi specification is developed by the Wireless Power Consortium, and more information can be found, for example, on the Wireless Power Consortium's website, http: / / www.wirelesspowerconsortium.com / index.html. In particular, the defined specification document can be found there.

[0008] The Wireless Power Consortium is developing the Ki specification (also known as the Cordless Kitchen specification), based on the Qi specification, with the aim of enabling safe, reliable, and efficient wireless power transmission to kitchen electrical appliances. Ki supports much higher power levels, up to 2.2 kW.

[0009] An issue that can occur with wireless power transmission is that the performance of power transmission significantly depends on specific conditions. In particular, the power transmission performance regarding efficiency, achievable power levels, adaptive response time, etc. generally greatly depends on how the transmitter coil and the receiver coil are arranged relative to each other. Generally, when the coils are arranged side by side and brought closer to each other, more efficient and reliable power transmission is generally achieved.

[0010] The performance of power transmission usually depends on the coupling coefficient or ratio, and the higher the coupling coefficient, the higher the efficiency of power transmission.

[0011] Aligning closer and having a higher coupling coefficient can be achieved by designing the devices such that the positioning of the power receiver device relative to the power transmitter device is severely restricted, for example, constraining the power receiver to one specific position, but this restricts the practicality of the system and is generally not desirable. For example, in the case of a kitchen appliance where the power transmitter is implemented within a kitchen counter, the user can only place the appliance approximately near the power transmitter coil, and it is preferable for the system to then adapt accordingly. It is also preferable for the power transmission function to be realized without requiring a mechanical or physical guiding mechanism that restricts the power receiver device. For example, it is desirable to be able to implement the power transmitter using a completely flat kitchen counter surface.

[0012] Power transmission starts at an initial operating point that realizes acceptable performance for the worst - case conditions in order to take into account significant changes in operating conditions. During power transmission, a control loop adapts the operating point to a more optimal operating point. Specifically, power transmission starts at a low power level and then gradually increases during power transmission. Summary of the Invention Problems to be Solved by the Invention

[0013] However, such methods are usually not optimal and fail to achieve ideal performance. Such methods tend to cause delays before optimal performance is achieved. In many scenarios and conditions, this method results in the control loop, for example, settling at a local extremum rather than progressing to an overall optimal value, thus failing to reach the optimal operating point.

[0014] Therefore, any method that can improve the operation of power transmission systems, in particular by increasing flexibility, reducing costs, decreasing complexity, improving coupling coefficient estimation, ensuring backward compatibility, improving suitability for higher power level transmissions, improving power transmission initialization, improving suitability for specific operating conditions, and / or improving performance, would be beneficial.

[0015] Therefore, the present invention aims to mitigate, reduce, or eliminate one or more of the drawbacks mentioned above, either individually or in any combination. [Means for solving the problem]

[0016] According to a first aspect of the present invention, a wireless power transmission system is provided comprising a power transmitter and a power receiver, wherein the power transmitter is configured to wirelessly supply power to the power receiver via an inductive power transmission signal, and the power transmitter comprises an output resonant circuit comprising a transmitter coil and at least one capacitor, a driver configured to generate a drive signal for the output resonant circuit and generate an inductive power transmission signal, and a resonance detector configured to determine a first coupled resonant frequency of the output resonant circuit during a resonance measurement period, wherein the first coupled resonant frequency is the resonant frequency of the output resonant circuit of the transmitter coil coupled to the receiver coil of the power transmission input resonant circuit of the power receiver, and the resonance detector is configured to determine the first coupled resonant frequency The power receiver comprises an estimation circuit configured to determine an estimated value of the coupling coefficient between a transmitter coil and a receiver coil, and an adapter configured to set operating parameters according to the estimated value of the coupling coefficient, and the power receiver comprises a power transmission input resonant circuit having a quality coefficient of 10 or more during the resonance measurement period, and a circuit configured to switch from a power transmission mode in which the quality coefficient is not limited to 10 or more to a measurement mode in which the quality coefficient becomes 10 or more during the resonance measurement period when the power receiver is operating in the measurement mode.

[0017] In many embodiments, the present invention enables improved power transmission. In many embodiments, the present invention enables improved initial performance and / or faster adaptation and convergence to a preferred operating point. In many embodiments, this method enhances the adaptability of power transmission to changing operating conditions. This method typically enables advantageous power transmission operation and performance while allowing for less complex embodiments. This method enables efficient, reliable, and / or accurate determination of coupling coefficients and can improve the adaptability of parameters that are usually important in power transmission, thereby enabling improved power transmission.

[0018] A particular advantage of this method is that, in many embodiments, it is entirely power transmitter-based, without necessarily performing specific estimation processes or calculations in the power receiver. This reduces costs in many scenarios. This method also facilitates implementation and / or improves backward compatibility.

[0019] The estimated coupling coefficient is an estimate of the change in the coupling coefficient.

[0020] The uncoupled resonant frequency of a resonant circuit is the resonant frequency when there is no inductive coupling from the resonant circuit to an inductor that is not part of the resonant circuit. The uncoupled resonant frequency of an output resonant circuit is the resonant frequency when the transmitter coil is not coupled to the receiver coil (or usually to any other inductor).

[0021] The first coupled resonant frequency is the resonant frequency of the output resonant circuit when the power receiver, to which the output resonant circuit is coupled with the receiver coil 107, is in the power transmission position for power transmission.

[0022] In some embodiments, the power transmission input resonant circuit has quality factors of 20, 50, 100, and even 500 or more during the resonance measurement period.

[0023] The coupled resonant frequency of the output resonant circuit corresponds to the resonant frequency of the drive signal, specifically to the maximum (or possibly minimum) value of the drive signal's characteristics with respect to the frequency at which the drive signal changes.

[0024] In some embodiments, the estimation circuit is further configured to determine an estimated value of the coupling coefficient depending on the uncoupled resonant frequency of the power transmission input resonant circuit.

[0025] In some embodiments, the uncoupled resonant frequency of the power transmission input resonant circuit is a predetermined frequency.

[0026] In some embodiments, the power transmitter further comprises a receiver that receives data from a power receiver, the receiver configured to receive data from the power receiver indicating the uncoupled resonant frequency of a power transmission input resonant circuit.

[0027] In some embodiments, the estimation circuit is further configured to determine an estimated value of the coupling coefficient depending on the uncoupled resonant frequency of the power transmission output resonant circuit.

[0028] In some embodiments, the uncoupled resonant frequency of the power transmission output resonant circuit is a predetermined frequency.

[0029] According to an optional feature of the present invention, the resonance detector is further configured to measure a second coupled resonance frequency of the output resonant circuit during the resonance measurement period, the second coupled resonance frequency being another resonance frequency of the output resonant circuit in the presence of a power receiver, and the estimation circuit is further configured to determine an estimated value of the coupling coefficient according to the second coupled resonance frequency.

[0030] In many embodiments, this improves and / or facilitates the estimation of coupling coefficients, and specifically reduces sensitivity to changes in the operating environment, components, changing or unknown parameters of the power transmitter and / or power receiver, and / or measurement errors or inaccuracies in many scenarios.

[0031] According to an optional feature of the present invention, the first coupling resonance frequency and / or the second coupling resonance frequency are frequencies at which the current of the drive signal shows a maximum value.

[0032] This results in improved performance and / or operation, typically making the estimation of coupling coefficients easier or more efficient.

[0033] The maximum value is the maximum value of the drive signal current in response to a change in the drive signal frequency.

[0034] In some embodiments, the estimation circuit is configured to determine the coupling coefficient based on the ratio of the first coupling resonance frequency to the second coupling resonance frequency.

[0035] According to an optional feature of the present invention, the estimation circuit is further configured to determine the coupling coefficient according to the uncoupled resonant frequency of the output resonant circuit and the uncoupled resonant frequency of the input resonant circuit.

[0036] This results in improved performance and / or operation, typically making the estimation of coupling coefficients easier or more efficient.

[0037] According to an optional feature of the present invention, the estimation circuit is further configured to determine the coupling coefficient according to the ratio of the uncoupled resonant frequency of the output resonant circuit to the uncoupled resonant frequency of the input resonant circuit.

[0038] This results in improved performance and / or operation, typically making the estimation of coupling coefficients easier or more efficient. Specifically, this reduces sensitivity in many scenarios to changes in the operating environment, components, changing or unknown parameters of the power transmitter and / or power receiver, and / or measurement errors or inaccuracies.

[0039] In some embodiments, the estimation circuit is configured to determine a first ratio between a first coupling resonance frequency and a second coupling resonance frequency, and to determine the coupling coefficient, which is a function of that ratio.

[0040] According to an optional feature of the present invention, the estimation circuit is further configured to determine the coupling coefficient according to the ratio of the sum of the squares of the uncoupled resonant frequencies of the output resonant circuit and the input resonant circuit to the sum of the squares of the second coupled resonant frequency, which is the resonant frequency of the output resonant circuit of the transmitter coil coupled to the receiver coil, and the first coupled resonant frequency.

[0041] This results in improved performance and / or operation, typically making the estimation of coupling coefficients easier or more efficient. Specifically, this reduces sensitivity in many scenarios to changes in the operating environment, components, changing or unknown parameters of the power transmitter and / or power receiver, and / or measurement errors or inaccuracies.

[0042] According to an optional feature of the present invention, the resonance detector is configured to determine that the uncoupled resonance frequency of the output resonance circuit is the frequency at which the current of the drive signal shows a maximum value for an input resonance circuit having a quality coefficient of 2 or less, and the estimation circuit is configured to determine the coupling coefficient according to the uncoupled resonance frequency of the output resonance circuit.

[0043] This improves the determination of the uncoupled resonant frequency of the output resonant circuit under current conditions, and consequently, improves the estimation of the coupling coefficient.

[0044] In some embodiments, the input resonant circuit has a quality factor of 0.5, 1, 3, or 5 or less when determining the maximum value corresponding to the uncoupled resonant frequency of the output resonant circuit.

[0045] The maximum value is the maximum value of the drive signal current in response to a change in the drive signal frequency.

[0046] According to an optional feature of the present invention, the resonance detector is configured to determine that the uncoupled resonance frequency of the input resonant circuit is the frequency at which the current of the drive signal shows a minimum value for an input resonant circuit having a quality factor of 10 or more, and the estimation circuit is configured to determine the coupling coefficient according to the uncoupled resonance frequency of the input resonant circuit.

[0047] This improves the determination of the uncoupled resonant frequency of the input resonant circuit under current conditions, and consequently improves the estimation of the coupling coefficient.

[0048] In some embodiments, the input resonant circuit has a quality factor of 5, 15, 20, or 30 or more when determining the minimum value corresponding to the uncoupled resonant frequency of the input resonant circuit.

[0049] The minimum value is the minimum value of the drive signal current in response to a change in the drive signal frequency.

[0050] The minimum is determined during the resonance measurement period, specifically by using the same frequency sweep to determine both the coupled resonant frequencies of one or more output resonant circuits / drive signals and the uncoupled resonant frequencies of the input resonant circuits.

[0051] In some embodiments, the resonant detector is configured to control a driver to generate a drive signal whose frequency changes during the resonant measurement period, and to determine a first coupled resonant frequency depending on at least one of the voltage of the drive signal, the current of the drive signal, and the phase difference between the voltage of the drive signal and the current of the drive signal.

[0052] This provides a particularly advantageous method, leading to highly efficient and practical determination of coupling coefficients, and therefore, an improvement in setting operating parameters.

[0053] In some embodiments, the resonant detector is configured to control a driver to perform a frequency sweep of the drive signal from higher frequencies to lower frequencies, and to determine a first coupled resonant frequency, which is a first detection frequency at which a criterion for the drive signal resonance is met.

[0054] This improves the detection of the coupling resonant frequency of the output resonant circuit in many embodiments, and therefore improves the estimation of the coupling coefficient, leading to improved setting of operating parameters and improved power transmission.

[0055] According to an optional feature of the present invention, the resonance measurement period is during the initialization of the power transmission operation, and the operating parameters are the initial operating parameters for the power transmission operation.

[0056] This method can improve the initialization of power transmission. This method enables faster and / or more reliable convergence towards the preferred operating point of power transmission.

[0057] According to an optional feature of the present invention, the driver is configured to generate a drive signal according to a repetition time frame, the power transmission stage comprising at least one power transmission period and at least one measurement period, wherein the resonant measurement period is included in the measurement period.

[0058] Specifically, this method makes it possible to improve adaptability to changes in operating conditions during power transmission, such as increasing the adaptability of the power receiver to the movement of the power transmitter.

[0059] In many embodiments, the duration of the measurement period is 5%, 10%, or 20% or more of the duration of the time frame. In many embodiments, the duration of the measurement period is 70%, 80%, or 90% or less of the time frame. In many scenarios, the duration of the measurement period is 5 milliseconds, 10 milliseconds, or 50 milliseconds or less.

[0060] In some embodiments, the operating parameter is a parameter that controls the power level of the power transmission signal.

[0061] The operating parameters enable particularly advantageous operation in many embodiments.

[0062] The parameters that control the power level of a power transmission signal are specifically the parameters of the drive signal, such as the frequency, duty cycle, phase, current, and / or voltage of the drive signal.

[0063] According to an optional feature of the present invention, the operating parameter is a power loop parameter, which is a loop parameter of a power control loop configured to adapt the power level of a power transmission signal in response to a power control message received from a power receiver.

[0064] Operating parameters enable particularly advantageous operation in many embodiments. These parameters allow for the dynamic adaptation and / or optimization of the power transmission control response to current conditions. This approach enables faster control operation in many scenarios while still ensuring control loop stability.

[0065] Loop parameters specifically refer to loop gain and / or loop delay.

[0066] In some embodiments, the estimation circuit is further configured to determine an estimated value of the coupling coefficient depending on the uncoupled resonant frequency of the power transmission input resonant circuit.

[0067] This improves the estimation of coupling coefficients in many scenarios, making it easier to make decisions regarding coupling coefficient estimations.

[0068] The uncoupled resonant frequency of a power transmission input resonant circuit is the resonant frequency of the power transmission input resonant circuit when the receiver coil is not coupled to the transmitter coil (or typically to any other inductor).

[0069] According to some embodiments, the resonant detector is further configured to determine a second coupled resonant frequency of the output resonant circuit during the resonant measurement period, the second operating resonant frequency being another resonant frequency of the output resonant circuit in the presence of a power receiver, and the estimation circuit is further configured to determine an estimate of the coupling coefficients according to the second operating resonant frequency.

[0070] This results in particularly advantageous and / or smooth operation and / or performance in many embodiments.

[0071] In some embodiments, the estimation circuit is configured to determine an estimate of the coupling coefficients according to at least one of the following equations.

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[0072] This results in particularly advantageous and / or smooth operation and / or performance in many embodiments.

[0073] The power receiver includes a circuit configured to switch from a power transmission mode in which the quality factor is not limited to 10 or more, to a measurement mode in which, during the resonant measurement period, the quality factor becomes 10 or more when the power receiver is operating in measurement mode.

[0074] This results in particularly advantageous and / or smooth operation and / or performance in many embodiments.

[0075] According to an optional feature of the present invention, the power receiver further comprises a circuit configured to short-circuit the power transmission input resonant circuit during the resonant measurement period.

[0076] This results in particularly advantageous and / or smooth operation and / or performance in many embodiments.

[0077] According to another aspect of the present invention, a method for operating a wireless power transmission system comprising a power transmitter and a power receiver is provided, wherein the power transmitter is configured to wirelessly supply power to the power receiver via an inductive power transmission signal, the power transmitter comprises an output resonant circuit comprising a transmitter coil and at least one capacitor, and the power receiver comprises a power transmission input resonant circuit comprising a receiver coil configured to extract power from the power transmitter and at least one capacitor, the method for operating the system comprising the steps of the power transmitter generating a drive signal for the output resonant circuit and generating an inductive power transmission signal, and determining a first coupled resonant frequency of the output resonant circuit during a resonance measurement period, wherein the first coupled resonant frequency is power The method comprises the steps of: determining a first coupled resonant frequency which is the resonant frequency of the output resonant circuit of the transmitter coil coupled to the receiver coil of the power transmission input resonant circuit of the receiver, and which the power transmission input resonant circuit has a quality factor of 10 or more during the resonant measurement period; determining an estimated value of the coupling coefficient relating to the coupling between the transmitter coil and the receiver coil according to the first coupled resonant frequency; and setting operating parameters according to the estimated value of the coupling coefficient. The method further comprises the step of switching from a power transmission mode in which the power receiver operates, in which the quality factor is not limited to 10 or more, to a measurement mode in which the quality factor becomes 10 or more during the resonant measurement period when the power receiver is operating in measurement mode.

[0078] According to another aspect of the present invention, a power receiver for a wireless power transmission system comprising a power transmitter and a power receiver is provided, the power transmitter configured to wirelessly supply power to the power receiver via an inductive power transmission signal, the power receiver comprising a power transmission input resonant circuit comprising a receiver coil configured to draw power from the power transmitter and at least one capacitor, and a circuit configured to switch from a power transmission mode in which the quality factor is not limited to 10 or more to a measurement mode in which, during the resonant measurement period, the quality factor is 10 or more when the power receiver is operating in the measurement mode.

[0079] According to another aspect of the present invention, a method for operating a power receiver for a wireless power transmission system comprising a power transmitter and a power receiver is provided, wherein the power transmitter is configured to wirelessly supply power to the power receiver via an inductive power transmission signal, and the power receiver comprises a power transmission input resonant circuit comprising a power transmitter and a receiver coil configured to draw power from at least one capacitor, the method having a circuit configured to switch from a power transmission mode in which the quality factor is not limited to 10 or more, to a measurement mode in which, during a resonant measurement period, the quality factor is 10 or more when the power receiver is operating in measurement mode.

[0080] Embodiments of the present invention will be described simply as examples with reference to the following drawings. [Brief explanation of the drawing]

[0081] [Figure 1] This figure shows an example of elements of a power transmission system according to several embodiments of the present invention. [Figure 2] This figure shows an example of the equivalent circuit of the power transmission system shown in Figure 1. [Figure 3] This figure shows an example of a power transmitter element according to several embodiments of the present invention. [Figure 4] This figure shows an example of a half-bridge type inverter for a power transmitter. [Figure 5] This figure shows an example of a full-bridge inverter for a power transmitter. [Figure 6] This figure shows an example of an element of a power receiver according to several embodiments of the present invention. [Figure 7] This figure shows an example of the response of the output resonant circuit of the power transmitter shown in Figure 3. [Figure 8] This figure shows an example of the coupled resonant frequency of the output resonant circuit of the power transmitter shown in Figure 3, which is a function of the coupling coefficient. [Figure 9] This figure shows an example of the coupled resonant frequency of the output resonant circuit of the power transmitter shown in Figure 3, which is a function of the coupling coefficient. [Figure 10]This figure shows an example of the response of the output resonant circuit of the power transmitter shown in Figure 3. [Figure 11] This figure shows an example of the response of the output resonant circuit of the power transmitter shown in Figure 3. [Figure 12] This figure shows an example of the response of the output resonant circuit of the power transmitter shown in Figure 3. [Figure 13] This figure shows an example of the response of the output resonant circuit of the power transmitter shown in Figure 3. [Figure 14] This figure shows an example of the response of the output resonant circuit of the power transmitter shown in Figure 3. [Figure 15] This figure shows an example of a time frame for the wireless power transmission system shown in Figure 1. [Figure 16] This figure shows an example of the equivalent circuit of the power transmission system shown in Figure 1. [Modes for carrying out the invention]

[0082] The following description focuses on embodiments of the present invention applicable to wireless power transmission systems that utilize power transmission techniques such as those known as the Qi or Ki specifications. However, it will be understood that the present invention is not limited to this application and is applicable to many other wireless power transmission systems.

[0083] Figure 1 shows an example of a power transmission system according to several embodiments of the present invention. The power transmission system comprises a power transmitter 101 having a transmitter coil / inductor 103 (or coupled to a transmitter coil / inductor). The system further comprises a power receiver 105 having a receiver coil / inductor 107 (or coupled to a receiver coil / inductor).

[0084] The system supplies an inductive electromagnetic wave power transmission signal that inductively transmits power from the power transmitter 101 to the power receiver 105. Specifically, the power transmitter 101 generates an electromagnetic signal that propagates as magnetic flux from the transmitter coil or inductor 103. The power transmission signal typically has a frequency between approximately 20 kHz and 500 kHz, often in the range of 95 kHz to 205 kHz in Qi-compatible systems and 20 kHz to 80 kHz in Ki-compatible systems. Since the transmitter coil 103 and the receiving coil 107 are loosely coupled, the receiving coil 107 receives (at least a portion of) the power transmission signal from the power transmitter 101. Thus, power is transmitted from the power transmitter 101 to the power receiver 105 via radio inductive coupling from the transmitter coil 103 to the receiving coil 107. The term "power transmission signal" is primarily used to refer to the inductive signal / magnetic field (magnetic flux signal) between the transmitter coil 103 and the receiving coil 107, but it will also be understood to refer to and be used to refer to any electrical signal supplied to the transmitter coil 103 or received by the receiving coil 107.

[0085] In this example, the power receiver 105 is specifically a power receiver that receives power via a receiver coil 107. However, in other embodiments, the power receiver 105 comprises a metallic element such as a metal heating element, in which case the power transmission signal directly induces eddy currents, which in turn directly heat the element.

[0086] The system is configured to transmit a wide range of power levels, and the power transmitter in particular supports power levels of 500mW, 1W, 5W, 50W, 100W, or more than 500W in many embodiments. Power transmission typically ranges from 1 to 5W for low-power applications (basic power profile), up to 15W for Qi specification version 1.2, up to 100W for higher-power applications such as power tools, laptops, drones, and robots, and beyond 100W to over 2000W for very high-power applications such as Qi-enabled kitchen applications.

[0087] The operation of the power transmitter 101 and power receiver 105 will be described below with particular reference to embodiments that generally conform to the Qi or Ki specifications (excluding modifications and enhancements described herein or resulting therefrom), or are suitable for higher-power kitchen specifications developed by the Wireless Power Consortium. The power transmitter 101 and power receiver 105 conform to or are substantially compatible with elements of Qi specification versions 1.0, 1.1, 1.2, or 1.3 (excluding modifications and enhancements described herein or resulting therefrom).

[0088] Many wireless power transmission systems, particularly high-power systems such as Ki, utilize resonant power transmission, where the transmitter coil 103 is part of a resonant circuit, and usually the receiver coil 107 is also part of a resonant circuit. In many embodiments, the resonant circuit is a series resonant circuit, so the transmitter coil 103 and the receiver coil 107 are coupled in series with the corresponding resonant capacitor. Using a resonant circuit usually results in more efficient power transmission.

[0089] In most power transmission systems, a communication channel is established between the power transmitter 101 and the power receiver 105 before power transmission begins. Once communication is established and the two devices are identified, the power transmitter 101 begins transmitting power to the power receiver 105.

[0090] Figure 2 shows an example of an electrical equivalent diagram of the power transfer function of a power transmitter 101 and a power receiver 105. A given system can have a wide range of power transmitters and power receivers, which have significantly different characteristics and parameters. For example, the size of the coils, the inductance, and the loads vary considerably. Therefore, the system parameters specifically shown in Figure 2 will actually differ significantly depending on various devices, mechanical structures, and positioning. In particular, the placement of the power receiver, and thus the relative position of the receiver coil 107 and the transmitter coil 103, significantly affects the coupling between the coils, i.e., the primary side (power transmitter side) inductor Lp and the secondary side (power transmitter side) inductor Ls, and thus the behavior of the system changes considerably.

[0091] A power receiving device may also have several different modes of operation, such as several loads being switched on or off in various modes. For example, if the power receiver is an oil-free fryer appliance, the heating element can be switched on or off. This can result in very large load steps, such as from 50 to 1200W and vice versa. Furthermore, such load switching may be repeated during the device's operation to maintain a constant temperature. The system may also include nonlinear loads. For example, the power receiver may drive a motor, such as the motor in a food processor, rather than a resistive component. This results in a completely different system response and, specifically, has a significant impact on the design of the control system.

[0092] Wireless power transmission systems typically use a power control loop to guide the system towards the appropriate operating point. This power control loop modifies the amount of power transmitted from the power transmitter to the power receiver. It can measure the received power (or voltage or current) and, along with the set power value, generate an error signal. The electrical appliance transmits this error signal, or possibly the desired power set value, to the power control function of the power transmitter to reduce, ideally, the static error to zero.

[0093] However, since the performance and operation of the system vary greatly depending on the combination and arrangement of existing power transmitters and power receivers, the appropriate operating point also varies considerably. This includes the conditions during power transmission startup / initialization, so the optimal initial operating point also varies greatly.

[0094] One of the important parameters that affects operation is the coupling coefficient. The coupling coefficient also largely depends on the positioning of the power receiver relative to the power transmitter (specifically, the receiver coil 107 relative to the transmitter coil 103), and therefore on specific operating conditions. In contrast, most of the other parameters in Figure 2 are generally known and are generally relatively constant for a given combination of power transmitter and receiver coils 107. Therefore, almost all relevant system parameters are usually known, except for the coupling coefficient. The coupling coefficient varies depending on many parameters, particularly the size / geometry of the coils, as well as the distance between the power transmitter and the power receiver.

[0095] In the system shown in Figure 1, the system has the function of estimating the coupling coefficient and fitting the operating parameters according to the coupling coefficient. Specifically, in many embodiments, parameters of the control loop, such as the open-loop transfer function and / or loop gain, are fitted to optimize and control the closed-loop performance. As another example, a preferred (usually early) operating point, such as the power level, is fitted according to the coupling coefficient. Measurement and fitting are performed before power transmission in some embodiments, and alternatively or additionally, after power transmission.

[0096] In an exemplary operation, when a power receiver is placed on top of a power transmitter, communication is established between the two. This allows the power transmitter to begin transmitting power, but first, a suitable operating point must be established. One option would be to select a very safe and reliable operating point that can guarantee operation even in the worst-case scenario, and then gradually adapt the operating point during power transmission. However, such a method is often time-consuming and inefficient, and in fact, in many scenarios, gradually adapting to the optimal operating point is not practical (for example, the system remains at a local maximum rather than progressing to its overall maximum).

[0097] Therefore, it is preferable to determine a desired operating point and start operation at or near this desired operating point. The desired operating point can be estimated using all known system parameters. Known system parameters include (or consist of) primary and secondary inductances, primary and secondary resonances, load resistance values, power and voltage, and coupling coefficients, for example. If all these parameters are known, the transfer function of the power path can be calculated and the initial operating point can be determined. However, while the power transmitter can know most of the parameters based on the parameters of the power receiver transmitted from the power receiver, for example, the coupling coefficients cannot be known in advance because they vary depending on the placement / misalignment of the devices.

[0098] The power transmitter then proceeds to the measurement / estimation of the coupling coefficient in this example. This is done, for example, by determining one or more resonant frequencies of the power transmitter resonant circuit when the power receiver is loaded. During such measurement, the power receiver enters a high-Q mode, and the resonant frequency is determined by a frequency sweep of the signal driving the transmitter coil 103 in the power transmitter. The coupling coefficient is calculated based on the measured resonant frequency, for example, based on the resonant frequency of the power receiver and the self-propelled resonant frequency of the power transmitter.

[0099] Next, using these coupling coefficients, the complete transfer function can be calculated, and then the initial operating point and required operating parameters, such as the initial power level and / or loop gain, can be calculated. Setting the operating parameters to the calculated values ​​allows the initial operating point to be reached from the start of power transmission, resulting in the appropriate power / current being delivered to the power receiver.

[0100] In fact, by measuring the coupling coefficients of the power transmission system before power is transmitted, the system response can be more accurately estimated. This allows for a more appropriate selection of the initial operating point (power signal frequency, duty cycle, loop gain, etc.). As a result, the desired power level can be reached much more quickly. Such a technique also reduces the risk of overvoltage or overcurrent conditions occurring.

[0101] Furthermore, measuring the coupling coefficient during power transmission and adapting the operating parameters based on these measurements improves performance and typically allows for more accurate optimization and adaptation.

[0102] Figure 3 shows the elements of the power transmitter 101 in Figure 1 in more detail.

[0103] The power transmitter 101 includes a driver 301 which can generate a drive signal supplied to the transmitter coil 103, and the transmitter coil, in return, generates an electromagnetic power transmission signal, thereby enabling power transmission to the power receiver 105. The transmitter coil 103 is part of an output resonant circuit, which includes the transmitter coil 103 and a capacitor 303. In this example, the output resonant circuit is a series resonant circuit, but in other embodiments, the output resonant circuit will be understood to be a parallel resonant circuit. It will be understood that any suitable resonant circuit may be used, including a resonant circuit comprising multiple inductors and / or capacitors.

[0104] The driver 301 generates current and voltage supplied to the output resonant circuit and, therefore, to the transmitter coil 103. The driver 301 is typically a drive circuit in the form of an inverter that generates an AC signal from a DC voltage. The output of the driver 301 is typically a switch bridge that generates the drive signal by the proper switching of the switches of the switch bridge. Figure 4 shows a half-bridge type switch bridge / inverter. Switches S1 and S2 are controlled so that they never close at the same time. Alternately, S1 is closed while S2 is open, and S2 is closed while S1 is open. The switches open and close at the desired frequency, thereby generating an AC signal at the output. The output of the inverter is typically connected to the transmitter inductor via a resonant capacitor. Figure 5 shows a full-bridge type switch bridge / inverter. Switches S1 and S2 are controlled so that they never close at the same time. Switches S3 and S4 are controlled so that they never close at the same time. Alternating between S2 and S3 being open, switches S1 and S4 are closed, and then S2 and S3 are closed while S1 and S4 are open, thereby producing a square wave signal at the output. The switches are opened and closed at a desired frequency.

[0105] The power transmitter 101 further comprises a power transmitter controller 305 configured to control the operation of the power transmitter 101 according to a desired operating principle. Specifically, the power transmitter 101 has many of the functions necessary to perform power control according to the Qi specification or Ki specification.

[0106] The power transmitter controller 305 is configured to control the generation of drive signals by the driver 301, and specifically, it can control the power level of the drive signals, and therefore the level of the generated power transmission signals. The power transmitter controller 305 includes a power loop controller that controls the power level of the power transmission signals in response to power control messages received from the power receiver 105 during the power transmission phase.

[0107] The power transmitter controller 305 further has functions for communicating with the power receiver 105. The power transmitter controller 305 is configured to transmit data to the power receiver 105 by modulating the power transmission signal, for example, and to receive data from the power receiver 105 by detecting load modulation of the power transmission signal. In other embodiments, it will be understood that other communication means may be used, such as implementing a different communication function, like NFC communication.

[0108] It is well known that the use of a resonant circuit with a transmitter coil 103 enables more efficient power transmission in many scenarios. Furthermore, having a power receiver that also uses a resonant circuit, in other words, in which the receiver coil 107 is part of the resonant circuit, results in resonant power transmission that offers many advantages, including highly efficient power transmission and ease of control of power transmission, such as by controlling the frequency of the drive signal.

[0109] Figure 6 shows some exemplary elements of the power receiver 105.

[0110] The receiver coil 107 is coupled to the power receiver controller 601 via a capacitor 603 that, together with the receiver coil 107, forms an input resonant circuit. Power transmission is therefore resonant power transmission between the resonant circuits.

[0111] The power receiver controller 601 specifically couples the receiver coil 107 to the load 605 via a switch 607 that can short-circuit the load 605. The power receiver controller 601 includes a power control path that converts the power extracted by the receiver coil 107 into a suitable power source for the load 605. In some embodiments, the power receiver controller 601 includes a direct power path in which the input resonant circuit is simply connected to the switch 607 or the load 605, i.e., the power path of the power receiver controller 601 is realized by simply two wires. In other embodiments, the power path includes, for example, a rectifier for supplying a DC voltage, and optionally a smoothing capacitor. In yet another embodiment, the power path includes more complex functions such as, for example, a voltage control circuit, an impedance matching circuit, and a current control circuit. Similarly, it will be understood that the switch 607 is only present in some embodiments, and in some embodiments, the load 605 may be permanently coupled to the input resonant circuit.

[0112] In addition, the power receiver controller 601 has various power receiver controller functions necessary for performing power transmission, in particular functions necessary for performing power transmission in accordance with the Qi or Ki specification.

[0113] The power receiver controller 601 further has functions for communicating with the power transmitter 101. For example, it may be configured to decode and demodulate data modulated on the power transmission signal, or it may be configured to transmit data to the power transmitter 101 by load modulating the power transmission signal. In some embodiments, other communication functions are used, such as NFC communication functions.

[0114] The system is configured to control the drive signal so that, during operation, the power transmission signal obtains suitable operating parameters / characteristics and the power transmission operates at a suitable operating point. The power transmitter is configured to control the parameters of the drive signal using a power control loop, in which the power characteristics of the power transmission signal / drive signal are controlled in response to power control error messages received from the power receiver.

[0115] The power receiver sends power control error messages to the power transmitter at regular intervals, typically frequently. In some embodiments, a direct power setpoint change message is sent, indicating the desired absolute power level (rather than a relative error message). The power receiver 105 has the functionality to handle such a power control loop. For example, the power receiver controller 601 continuously monitors the power or voltage of the load signal supplied to the load and detects whether it is above or below a desired value. The power receiver controller generates a power control error message at regular intervals requesting an increase or decrease in the power level of the power transmission signal and sends this power control error message to the power transmitter.

[0116] When the transmitter controller 305 receives a power control error message from the power receiver, it determines how the drive signal parameters need to be modified in order to increase or decrease the power level of the power transmission signal as requested. The transmitter controller then controls and adapts the drive signal parameters accordingly.

[0117] Therefore, a power control loop is used to control the power characteristics of the power transmission signal and obtain the desired operating point in the power receiver. The operation of power transmission is thus controlled by the power control loop, and its effective operation is crucial to the system's performance. Therefore, it is important to initialize or adapt the power control loop to the operating conditions in order to obtain optimal performance.

[0118] The power transmitter has the function of estimating the coupling coefficients in the described system and adapting the operation of the power transmission system, specifically the power control loop, based on the coupling coefficients.

[0119] The power transmitter is configured to determine the coupling coefficient in response to the detection / measurement of one or more resonant frequencies (and / or equivalent drive signals) of the output resonant circuit when coupled to the power receiver, specifically the receiver coil 107 and the input resonant circuit. The power transmitter then adapts the operation of the power transmission system accordingly.

[0120] The power transmitter 101 includes a resonance detector 307 configured to determine at least one coupled operating resonance frequency of the output resonant circuit during the resonance measurement period. Here, the coupled resonance frequency is the resonance frequency of the output resonant circuit when a power receiver is present, i.e., when the transmitter coil 103 is coupled to the receiver coil 107 of the power receiver. The coupled resonance frequency therefore reflects the effective resonance frequency of the output resonant circuit when the transmitter coil 103 is coupled to the receiver coil 107. The effective inductance of the transmitter coil 103 is different from the self-inductance of the transmitter coil 103 when it is not coupled to any receiver coil 107, due to the coupling of the two coils. Similarly, the effective inductance of the receiver coil 107 is different from the self-inductance of the receiver coil 107 when it is not coupled to any transmitter coil 103. As a result, the effective resonance is different from the self-resonance when there is no coupling. Furthermore, the drive signal is effectively affected by two (out of phase) resonant frequencies due to the coupling of the two coils, and therefore the two resonant circuits. In other words, the output resonant circuit effectively has two resonant frequencies due to the coupling, and these two resonant frequencies are out of phase with the output resonant circuit's own (uncoupled) resonant frequency.

[0121] In many embodiments, the resonance detector 307 is configured to determine both coupled resonance frequencies.

[0122] The effective resonant frequency or coupled resonant frequency of the output resonant circuit is different from the self-resonant frequency of the output resonant circuit when it is not coupled to any other inductor, and this difference depends on the coupling. Therefore, by detecting the coupled resonant frequency or operating resonant frequency of the output resonant circuit, information regarding the coupling with the receiver coil 107 can be obtained, and this information is used in the power transmitter 101 to estimate the coupling coefficient.

[0123] The resonant detector 307 is coupled to an estimation circuit 309, which is configured to determine an estimated coupling coefficient for the coupling between the transmitter coil 103 and the receiver coil 107, based at least on the coupling resonant frequency.

[0124] In some embodiments, the estimation circuit 309 is configured to generate an estimate of the coupling coefficient based on only one measured coupling resonance frequency. The estimation circuit 309 has a lookup table that presents a coupling estimate for an input address word corresponding to the determined coupling resonance frequency. The lookup table is generated, for example, by measurements during the manufacturing and design phases, or based on theoretical calculations.

[0125] However, while such methods are advantageous in many embodiments, they often fail to yield optimal estimates of the coupling coefficients when the relevant parameters change significantly, and are therefore typically limited to situations where the relevant parameters (including electrical parameters of the resonant circuit, and characteristics of the power transmitter and power receiver) are very restricted.

[0126] In most embodiments, the estimation circuit 309 is configured to further consider additional parameters, and in many embodiments, the estimation circuit 309 is configured to determine an estimate of the coupling coefficients based on also considering a second coupled resonant frequency of the output resonant circuit, the self-resonant frequency / uncoupled resonant frequency of the output resonant circuit, and the self-resonant frequency / uncoupled resonant frequency of the input resonant circuit.

[0127] In particular, in many embodiments, the estimator 309 is configured to further consider the uncoupled resonant frequency of the output resonant circuit when determining the estimated coupling coefficient.

[0128] The uncoupled frequency of the output resonant circuit is the resonant frequency of the output resonant circuit when it is not coupled to the receiver coil 107, and is typically the resonant frequency of the output resonant circuit when it is not coupled to any inductor. The uncoupled resonant frequency is also called the self-resonant frequency of the output resonant circuit.

[0129] The estimation circuit 309 is therefore configured, in many embodiments, to estimate the coupling coefficient based on the effect that the coupling between the transmitter coil 103 and the receiver coil 107 has on the resonant frequency of the output resonant circuit.

[0130] The estimation circuit 309 is coupled to an adapter 311 configured to set operating parameters according to the estimated coupling coefficients. In some embodiments, the settings are relative or absolute. The adapter 311 performs relative setting of operating parameters, for example, by increasing or decreasing parameter values ​​by a given amount, such as increasing or decreasing the power level from its current value.

[0131] In some embodiments, the adapter 311 is configured to adapt or set operating values ​​for power transmission signal parameters, specifically, to set parameter values ​​for the power transmission signal that control the power level of the power transmission signal. Such parameter values ​​include the frequency (which affects the power level of the resonant power transmission system), phase, amplitude (current and / or voltage), or duty cycle of the power transmission signal.

[0132] For example, if the coupling coefficient is high, power transmission between coils is efficient, allowing for a higher power level to be set. However, if the coupling coefficient is low, power transmission is less efficient, requiring a lower power level to be set.

[0133] Therefore, by estimating the coupling coefficient, it is possible to determine a suitable power level, and by appropriately setting the operating parameters of the power transmission signal when starting the power transmission operation, the power transmission operation is initialized with its power level set to the desired value.

[0134] The appropriate power level is determined, for example, using a lookup table (LUT) generated during manufacturing. For example, based on measurements performed on various power receivers with various characteristics (e.g., coil dimensions, power receiver inductance values, etc.), suitable power levels for various coupling coefficients are determined and stored in the LUT. During operation, when initializing a new power transmission with a new power receiver, the power receiver transmits relevant parameter values ​​to the power transmitter, which further estimates the coupling coefficients. The resulting values ​​are used to perform a table lookup in the LUT, and the power transmission is initialized with the corresponding power level. Specifically, the LUT outputs suitable values ​​for the frequency, duty cycle, and / or amplitude of the drive signal. The adapter 311 then supplies this information to, for example, the power transmitter controller 305, which controls the driver 301 to generate a drive signal with these characteristics. The system then starts the power transmission with the suitable parameters and subsequently performs the adaptation by the power control loop.

[0135] In some embodiments, the adapter 311 alternatively or additionally adapts the power control loop parameters of the power control loop to control the power level of the power transmission signal based on power control messages received from the power receiver (105).

[0136] The open-loop performance of a power control loop is highly dependent on the coupling coefficient, and therefore, the closed-loop performance is also highly dependent. In fact, in many scenarios, the closed loop is stable only for a subset of coupling coefficient values. The loop gain is usually substantially proportional to the coupling coefficient, and as the coupling coefficient changes significantly, the gain changes significantly as well. Changes in the loop gain directly affect the closed-loop time (and frequency) response, including loop stability. Adapter 311 is configured to correct the loop gain so that the overall gain is at the desired level, compensating for changes in the coupling coefficient. This eliminates the need to set the loop gain to ensure stability in worst-case scenarios, thus achieving performance optimized by a faster operating loop.

[0137] In some embodiments, more complex fitting of the loop is performed, such as adjusting the delay or (open-loop) frequency response. This allows for more flexible fitting and more precise individualization of performance. For example, the filter response is fitted to prevent any possible self-oscillation and instability.

[0138] Regarding the power level of the power transmission signal, the parameters are determined by measurements and experiments during design / manufacturing, for example, using appropriate parameters stored in the LUT. In fact, both the control loop and power level setting parameters are stored in the same LUT.

[0139] The applicable operating parameters are not limited to power level parameters or loop parameters, and in some embodiments, other parameters may be set, either alternatively or additionally, such as foreign object detection parameters or communication parameters.

[0140] In various embodiments, the estimator 309 employs various methods to determine the coupling coefficient. In particular, when the output resonant circuit is coupled to the input resonant circuit and can oscillate with sufficient undamping, the output resonant circuit will exhibit not just one coupling resonant frequency, but practically two. Specifically, when the input resonant circuit is not attenuated at all, such as when the series load / resistance is substantially zero due to a short circuit in the series resonant circuit, the output resonant circuit will exhibit two coupling resonant frequencies.

[0141] As illustrated in the example in Figure 7, the response of the output resonant circuit when coupled to the input resonant circuit (which is well undamped) is a response that includes two resonances. Figure 7 shows an example of the response to typical system parameters (amplitude and phase of the primary side current with respect to a constant voltage amplitude of the drive signal) when the input resonant circuit is undamped, and as is clearly shown, the response includes two resonance peaks.

[0142] Figure 8 shows an example of how the resonant frequency of the coupled output resonant circuit changes for various coupling coefficients k. In this example, the uncoupled resonant frequencies of both the output and input resonant circuits are normalized to a frequency of 0.3 × 10⁻⁶. 5 As can be seen, when coupled, the first resonant frequency is higher than the uncoupled frequency, and the second resonant frequency is lower than the uncoupled frequency. Again, as can be seen, the resonant frequency strongly depends on the coupling coefficient, and as the coupling coefficient increases, the difference also increases.

[0143] Figure 9 shows an example corresponding to the example in Figure 8, where the normalized average uncoupled resonant frequency of the output resonant circuit is 0.268 × 10⁻⁶. 5 Therefore, the normalized mean uncoupled resonant frequency of the input resonant circuit is still 0.3 × 10⁻⁶. 5 As you can see, this causes the coupled resonant frequencies to be slightly different.

[0144] In some embodiments, as shown in Figures 8 and 9, such dependency measurements are performed during the manufacturing / design phase of the associated power transmitter and receiver coil 107 combination. The results are stored in the LUT of the power transmitter (or, for example, centrally stored and retrieved when setting up a new power transmission). The estimator 309 performs a table lookup following the determination of the coupling resonant frequency to obtain the estimated coupling coefficients.

[0145] In some embodiments, the resonant detector 307 is configured to detect the coupled resonant frequency by varying the frequency of the drive signal during the resonant measurement period. Specifically, the resonant detector performs a frequency sweep over a range of frequencies corresponding to frequency intervals within a range where a coupled resonant frequency is expected to exist or where the coupling coefficient is considered sufficiently high to achieve acceptable power transmission. The resonant detector 307 then monitors the drive signal and detects, for example, extreme values ​​of current or voltage amplitude. The resonant detector 307 controls the driver 301 to vary the frequency over a range with a constant voltage amplitude, for example, in the case of a series resonant circuit. The resonant detector 307 then measures the current amplitude at various frequencies and determines the coupled resonant frequency at which the maximum current amplitude is determined. As another example, the resonant detector 307 detects when the phase difference between the current and voltage of the drive signal becomes zero (or close to zero), i.e., when the load on the output resonant circuit becomes completely resistive. If no coupled resonant frequency is detected within this frequency interval, this indicates that the coupling coefficient is not within a suitable interval for power transmission, and power transmission is terminated.

[0146] In some embodiments, the frequency sweep of the drive signal is performed from higher frequencies to lower frequencies, and the coupled resonant frequency is determined to be the first detected frequency where the resonance criterion (e.g., an extreme value of the signal's current or voltage amplitude, or zero phase difference between voltage and current) is satisfied. Thus, for example, the first local extreme value is detected rather than an overall extreme value.

[0147] This method allows for the detection of the highest of the two coupling resonance frequencies. Since the greatest change in coupling resonance frequency with respect to a change in coupling coefficient occurs at the highest coupling resonance frequency, it is generally considered advantageous to use the highest coupling resonance frequency, especially when using only one coupling resonance frequency.

[0148] In some embodiments, both coupling resonant frequencies are detected and used to determine an estimate of the coupling coefficient. For example, two separate LUTs are provided for the lower coupling resonant frequency and the higher coupling resonant frequency, respectively, and the estimate of the coupling coefficient is determined to be the average of the lookup results from the two tables.

[0149] In other embodiments, other methods are used to determine the coupled resonant frequency of the output resonant circuit. For example, in some embodiments, a successive approximation method is used. Such a method would be very advantageous and useful when determining the resonant frequency based on frequency intervals. This method allows for the rapid detection of one or more resonant frequencies.

[0150] In some embodiments, the power receiver transmits system parameters, such as the uncoupled resonant frequency and / or the inductance of the receiver coil, to the power transmitter, and these system parameters are used to determine the coupling coefficient from the coupled resonant frequency. The LUT depends, for example, on the elements of such power receivers, or different LUTs are provided for different power receivers (in fact, in some embodiments, the LUT is supplied by the power receiver).

[0151] In some embodiments, the determination of the coupling coefficients is based on an analytical formula. Specifically, the estimation circuit 309 is configured to determine an estimated value of the coupling coefficients according to at least one of the following formulas.

number

[0152] These equations apply to coupled resonant circuits and are used (directly or indirectly) by the resonant detector 307.

[0153] In some embodiments, only one of the equations is used, and in fact, the estimated coupling coefficient is based on only one of the coupling resonant frequencies. For example, as described, the highest coupling resonant frequency is determined by detecting the first peak during a sweep from higher frequencies to lower frequencies. Based on the first equation above, the known uncoupled resonant frequencies of the input and output resonant circuits are used, and then this highest coupling resonant frequency is used to calculate the estimated coupling coefficient.

[0154] Using the same method, the coupling coefficient is determined based on the lowest coupling resonance frequency.

[0155] In some embodiments, both the highest and lowest coupling resonance frequencies are measured, and both equations are used. The values ​​of the two coupling coefficients are calculated, for example, using the first and second equations respectively, and the respective measured coupling resonance frequencies, and the estimated coupling coefficient is generated as the average of the two coupling coefficients. In other embodiments, the estimated coupling coefficient is calculated as the value that minimizes the error between the above equations and the measured values.

[0156] In some embodiments, both coupled resonant frequencies and both equations are used, but the uncoupled resonant frequency of the input resonant circuit is not. This variable is instead estimated using the above equation and the two coupled resonant frequencies. Such a method therefore employs more complex estimations and calculations so that the power transmitter does not need to know the specific characteristics of the input resonant circuit. Such a method is particularly useful in embodiments of existing systems where some power receivers cannot transmit this information.

[0157] The described method is based on estimating the coupling coefficient by considering the change in resonant frequency that occurs when an output resonant circuit is coupled to an input resonant circuit. This change depends not only on the coupling coefficient but also on the quality factor Q of the input resonant circuit. This change can be seen in Figures 10 to 14, which show not only how the two coupled resonant frequencies change for various coupling coefficients (k = [0.1, 0.2, ~0.9] in each graph), but also how this change depends on the Q value (this can be seen by comparing the various graphs, which show the graphs for Q = 1000, 10, 3, 1, and 0.1).

[0158] In this method, the quality factor of the input resonant circuit during the resonance measurement period is 10 or higher, and usually even higher. This increases the reliability and reasonable accuracy of the detection of the coupling resonance frequency, and similarly, the estimated coupling coefficients become more reliable and accurate. Therefore, the reliability of the operating point fitting is definitely increased, enabling efficient operation.

[0159] In some embodiments, a high Q during the resonant measurement period is ensured by the Q value of the input resonant circuit always being greater than 10, i.e., by the power receiver being designed so that the input resonant circuit always has a quality factor greater than 10. However, this is usually in contrast to the desire to supply adequate power to the load.

[0160] The Q value, for example in a Ki system, is usually less than 5, and often less than 2, depending on the load on the input resonant circuit with typical power values.

[0161] In many embodiments, the power receiver is configured to switch the operating mode from a lower quality factor mode to a higher quality factor mode having a Q value of at least 10 during the resonant measurement interval, for at least a period outside the resonant measurement period. This enables efficient power transmission and efficient estimation of the coupling coefficient. The power receiver is therefore configured to switch from a power transmission mode, in practice where the quality factor is substantially less than 10 and not limited to exceeding 10, to a measurement mode where the quality factor is 10 or greater during the resonant measurement period, in order to enable efficient power transmission.

[0162] This is achieved, for example, by switch 607. For example, if the power path directly couples switch 607 and load 605 to the input resonant circuit outside of the resonant measurement period, the switch couples the normal load 605 to the input resonant circuit. However, switch 607 disconnects load 605 during the resonant measurement period. In the case of an input parallel resonant circuit, switch 607 disconnects load 605, for example, to prevent current from being drawn from the input resonant circuit. In contrast, in the case of an input series resonant circuit, switch 607 disconnects the load by short-circuiting load 605 during the resonant measurement period, thereby short-circuiting the power transmission input resonant circuit.

[0163] In some embodiments, such changes to the quality factor are made when the power receiver does not have a particular function. For example, in some embodiments, the load performs an inherently effective short circuit during startup, thereby allowing it to have an inherently high-Q input resonant circuit during the resonant measurement period before power transmission. For example, if the load is a motor, the load starts up in an almost short-circuit state. As another example, if a rectifier and a high-power capacitor are present in the power path, when the capacitor discharges, this also acts almost the same as a short circuit.

[0164] In many embodiments, a resonant measurement period (or at least one resonant measurement period) precedes power transmission. The determination of estimated coupling coefficients and the setting of operating parameters are specifically performed during the initialization of the power transmission operation. The power transmitter therefore determines, before power transmission, operating parameter values ​​suitable for a particular power receiver and a specific location within the power receiver. The power transmitter then uses these parameter values ​​as initial operating parameter values ​​and begins power transmission.

[0165] This method is used, for example, in many embodiments to determine the initial loop gain and power level values ​​of a power transmission signal. The system therefore begins power transmission with a higher probability of being close to the optimal operating point, and does not need to slowly and gradually adapt from an initial, worst-case safe operating point. Thus, faster optimization can be achieved, and the risk of failing to reach the optimal operating point can be reduced.

[0166] Furthermore, the power receiver enters a measurement mode for detecting the coupling resonant frequency during coupling coefficient estimation, prior to power transmission. Specifically, switch 607 short-circuits the load to achieve a high quality coefficient for the input resonant circuit. When the system enters the power transmission phase, the power receiver switches back to the normal power transmission operation mode, specifically, the short circuit is resolved.

[0167] In some embodiments, this method is applied alternatively or additionally to the power transmission stage. In such a method, estimation of coupling coefficients is particularly useful for fitting loop parameters and performance. This method is used, for example, to fit loop parameters so that substantially the same control performance can be achieved for various positions of the power receiver. Thus, performance can be improved, and in particular, sensitivity to differences in the positioning of the power receiver can be reduced.

[0168] In many embodiments where this technique is used in the power transmission stage, the system is configured to operate in a time-slot mode, during which measurement and coupling resonant frequency detection are performed. The resonant measurement period is specifically performed during such a short measurement period of a repetitive time frame, which further includes at least one power transmission period during which power is transmitted to a power receiver.

[0169] The system, therefore, in such embodiments, utilizes time-division multiplexing in the power transmission stage. In particular, since the detection of the coupled resonant frequency and power transmission are performed, for example, in separate periods, interference between detection and power transmission can be significantly reduced.

[0170] In this example, the driver 301 and transmitter coil 103 are configured to generate an electromagnetic power transmission signal for the purpose of transmitting power to a power receiver during the power transmission interval. In addition, the coupling resonant frequency is detected using the drive signal during the measurement period to determine an estimate of the coupling coefficient. The power transmitter uses a repetitive time frame for the drive signal during the power transmission phase, and the time frame includes at least one power transmission period and at least one resonant measurement period. An example of such a repetitive time frame is shown in Figure 15, where the power transmission period is denoted by PT and the measurement period is denoted by D (this period is also called the detection period). In this example, each time frame FRM includes only one resonant measurement period and one power transmission period, and these (and the time frame itself) have the same duration in each frame. However, it will be understood that in other embodiments, other periods (e.g., communication intervals) may also be included in the time frame, or multiple resonant measurement periods and / or power transmission periods may be included in each time frame. Furthermore, in some embodiments, the duration of various periods (and in fact, the time frame itself) changes dynamically.

[0171] Therefore, in this method, the separation of measurement, communication, and power transmission in the time domain reduces mutual interference from power transmission to measurement and coupling coefficient estimation. Consequently, variability and uncertainty arising from changes in the operating conditions of power transmission can be separated from measurement and estimation, resulting in a more reliable and accurate estimation process. Furthermore, this method makes it possible to generate (and optimize) a drive signal to detect the coupling resonance frequency. In particular, this method allows the resonance detector 307 to perform a frequency sweep and operate in a manner suitable for this detection.

[0172] Furthermore, this method makes it possible to adapt the power receiver to achieve improved or optimal characteristic detection. In particular, in many embodiments, the power receiver switches from a power operating mode in which the load is coupled to the input resonant circuit (and therefore the quality factor of the input resonant circuit is low) during the power transmission period to a measurement mode in which a high quality factor of the input resonant circuit is ensured, for example by shorting the load with switch 607.

[0173] Therefore, the time-slot method makes it possible or easy to estimate coupling coefficients during the power transmission phase.

[0174] As described above, in many embodiments, the estimated coupling coefficient is determined not only based on at least one coupling resonant frequency, but also on the uncoupled / self-resonant and / or input resonant of the output resonant circuit (of the power transmitter) and / or the input resonant circuit (of the input resonant circuit).

[0175] In some embodiments, the uncoupled resonant frequencies of the input and / or output resonant circuits are predetermined frequencies. For example, in some embodiments, the power transmitter and / or power receiver are strictly limited, for example, by the specifications and provisions of a preferred standard. For example, a wireless power transmission standard (e.g., the Ki specification) specifies that the power transmitter and power receiver use output and input resonant circuits, each having an uncoupled resonant frequency of, for example, 30 kHz. In such embodiments, the estimator 309 is configured to estimate the coupling coefficients based on assumed nominal values ​​of one or more coupled and uncoupled resonant frequencies.

[0176] In other embodiments, the system allows for some variation in the output resonant circuit, for example. However, the power transmitter and estimator 309 can often know the uncoupled resonant frequency of the output resonant circuit. The output uncoupled resonant frequency is stored in memory, for example, during manufacturing, and retrieved and used when determining an estimate of the coupling coefficient. The uncoupled resonant frequency is simply determined as the resonant frequency resulting from, for example, the self-inductance of the transmitter coil and the capacitance of the resonant capacitor, and is stored in memory.

[0177] In some embodiments, such a predetermined (non-constant) value is used in conjunction with the assumed uncoupled resonant frequency of the input resonant circuit of a power receiver, for example, in scenarios where the uncoupled resonant frequency of the power receiver is defined by an appropriate standard.

[0178] In some embodiments, the estimator 309 is configured to determine the uncoupled resonant frequency of the input resonant circuit based on data received from the power receiver. In some embodiments, the power transmitter includes a data receiver 313 configured to receive data from the power receiver. Similarly, the power receiver includes a data transmitter 609 that transmits data to the power transmitter. Communication is carried out, for example, using load modulation or, for example, using NFC communication, which will be known to those skilled in the art.

[0179] In some embodiments, the data transmitter 609 transmits data to the data receiver 313 that is used to determine the uncoupled resonant frequency of the input resonant circuit. The power receiver transmits, for example, data that directly represents the uncoupled resonant frequency of the input resonant circuit. In other embodiments, the power receiver transmits characteristic data or data that allows the power transmitter to determine the input resonant circuit.

[0180] The power receiver transmits data representing parameters of the components of the input resonant circuit, such as, for example, the self-inductance of the receiver coil and the capacitance of the resonant capacitor in some embodiments. The estimator 309 then calculates the uncoupled resonant frequency from the values ​​of the components. As another example, the power receiver transmits information about the type of input resonant circuit the receiver is equipped with. For example, the characteristics (specifically, the uncoupled resonant frequencies) of a possible set of input resonant circuits are specified by the system standard, and the power receiver indicates which type is equipped. The power transmitter stores the uncoupled resonant frequencies of various types of input resonant circuits and retrieves values ​​for the indicated type. In some embodiments, the uncoupled resonant frequencies of the input resonant circuits are associated with the type or characteristics of the power receiver, which are transmitted to the power transmitter, for example, during the initialization of power transmission. For example, the values ​​of various components are used for various power levels, and the power receiver transmits an index of the required power level, which the power transmitter also uses to determine the uncoupled resonant frequency of the input resonant circuit.

[0181] The power transmitter therefore includes a data receiver configured, in some embodiments, to receive data from the power receiver indicating the uncoupled resonant frequency of a power transmission input resonant circuit. The data either directly represents the uncoupled resonant frequency or presents data that allows the uncoupled resonant frequency to be determined (based on further information, typically stored in the power transmitter).

[0182] However, embodiments that use a predetermined value of the uncoupled resonant frequency, independent of the current situation / state, achieve advantageous performance in many embodiments. However, it is recognized that performance improvements can be achieved by estimating the coupling coefficients using dynamically measured uncoupled resonant frequencies for the input and / or output resonant circuits.

[0183] In particular, it is recognized that changes in the uncoupled resonant frequency occur in various states and scenarios of wireless charging, and that this change is determined and taken into account when generating an estimate of the coupling coefficient. It is recognized that performance improvements can be achieved by using measured values ​​of the uncoupled resonant frequencies of the input and / or output resonant circuits. Furthermore, it is recognized that advantageous measurements can be made using the same method as for determining the coupled resonant frequency, and in fact, the coupled resonant frequency of the input resonant circuit can be determined from measurements during the same frequency sweep used to determine the coupled resonant frequency.

[0184] In some embodiments, the estimator 309 is configured to determine an estimate of the coupling coefficient based on at least one measurement of the natural resonant frequencies, rather than a predetermined value.

[0185] In some embodiments, the resonant detector 307 is further configured to determine the uncoupled resonant frequency of the input resonant circuit as the frequency at which the drive signal current exhibits a minimum value for an input resonant circuit with a quality factor of 10 or more. The uncoupled resonant frequency of the input resonant circuit, hereafter also referred to as the input uncoupled resonant frequency, is determined by measuring the drive signal while the input resonant circuit is substantially undamped. In many embodiments, the measurement and determination of the input uncoupled resonant frequency is performed when the load on the input resonant circuit is substantially zero, specifically, when the (series) load of a series resonant circuit is short-circuited or the (parallel) load of a parallel resonant circuit is disconnected.

[0186] The resonant detector 307 performs the measurement, for example, by performing a frequency sweep with the input resonant circuit in an undamped state and measuring the current of the drive signal. The resonant detector then determines that the input uncoupled resonant frequency is the frequency at which the current is minimum. In some embodiments, the determination of the frequency at which the current is minimum is more indirect, by measuring various parameters such as the phase between the voltage and current of the drive signal being zero and the power of the drive signal being minimized. In some embodiments, such a state occurs when the current is minimum (because such a state is caused by the resonant effect at that frequency).

[0187] In many embodiments, the determination of the input uncoupled resonant frequency is combined with the determination of the coupled resonant frequency. The resonant detector 307 performs the frequency sweep described previously to determine the coupled resonant frequency, which is the frequency at which a maximum value of the drive signal current is detected. In addition, the resonant detector determines the input uncoupled resonant frequency, which is the frequency at which the drive signal exhibits a minimum current, based on the same frequency sweep. This determination is based on a direct measurement of the drive signal current, as mentioned, or on the measurement of relevant parameters such as the phase, voltage, or power of the drive signal.

[0188] It is recognized that the frequency of the minimum drive signal current allows for a proper estimation of the uncoupled resonant frequency of the input resonant circuit.

[0189] In some embodiments, the resonant detector 307 is further configured to determine the uncoupled resonant frequency of the output resonant circuit as the frequency at which the drive signal current shows a maximum value for an input resonant circuit with a quality factor of 2 or less. The uncoupled resonant frequency of the output resonant circuit, hereafter also referred to as the output uncoupled resonant frequency, is determined by measuring the drive signal when the input resonant circuit is greatly attenuated, or in some cases completely attenuated. In many embodiments, the measurement and determination of the output uncoupled resonant frequency is performed when the load on the input resonant circuit is very large (in some cases virtually infinite), specifically when the (series) load of a series resonant circuit is disconnected or the (parallel) load of a parallel resonant circuit is short-circuited.

[0190] The resonance detector 307 performs the measurement, for example, by performing a frequency sweep with the input resonant circuit completely attenuated so that resonance does not occur in the input resonant circuit, and measuring the current of the drive signal. The resonance detector then determines the output uncoupled resonance frequency to be the frequency at which the current is maximum. In some embodiments, the determination of the frequency at which the current is maximum is more indirect, by measuring various parameters such as the phase between the voltage and current of the drive signal being zero and the power of the drive signal being minimized. In some embodiments, such a condition occurs when the current is maximum (because such a condition is caused by the resonance effect of the output resonant circuit at that frequency).

[0191] It is recognized that the frequency of the drive signal relative to the maximum current when the input resonant circuit is significantly attenuated allows for accurate estimation of the uncoupled resonant frequency of the output resonant circuit. Specifically, by significantly attenuating the input resonant circuit, the resonant effect of the input resonant circuit on the output resonant circuit can be eliminated or greatly reduced, thereby enabling measurement of the uncoupled resonant frequency of the output resonant circuit. For example, by opening a series input resonant circuit, no current flows through the receiver coil, and no power is extracted from the electromagnetic field. The input resonant circuit then substantially does not affect the output resonant circuit, making it possible to efficiently measure the uncoupled resonant frequency of the output resonant circuit.

[0192] Measuring the uncoupled resonant frequency substantially improves performance and allows for a more accurate estimation of the coupling coefficient. This method mitigates and compensates for the effects of variations in circumstances, environment, and power transmission equipment settings, particularly the effects of the characteristics of the power transmitter and power receiver. For example, the influence of the presence of a power receiver on the drive signal is not limited to the coupling between the transmitter and receiver coils (and therefore between the resonant circuits), but is also affected by other effects, such as the influence of metals within the power receiver and power transmitter devices. Such effects are independent of the coupling coefficient but vary significantly depending, for example, on the specific characteristics of the device embodiment and the positioning of the device or other elements in its vicinity. Consequently, such (usually unknown or inappropriate) effects hinder the estimation of the coupling coefficient, leading to reduced accuracy. However, current methods take these dependencies and effects into account by determining the uncoupled resonant frequency by measuring the RMS value under specific circumstances and conditions. Thus, by using at least one measurement of the uncoupled resonant frequency of the input or output resonant circuit, a substantially improved estimation of the coupling coefficient is achieved.

[0193] The measured (situation / state-dependent) uncoupled resonant frequency is also called the paired uncoupled resonant frequency.

[0194] As previously described, the estimator 309 is configured in many embodiments to determine an estimate of the coupling coefficients depending on both the first and second coupling resonant frequencies of the output resonant circuit / drive signal. Determining the estimate of the coupling coefficients is done, as mentioned, for example, by estimating the coupling coefficients for two different coupling resonant frequencies using a given coupling resonant frequency or a measured coupling resonant frequency, and averaging the results.

[0195] In another embodiment, the two coupled resonant frequencies are determined and used together with the estimated uncoupled resonant frequency of the output resonant circuit to estimate the coupling coefficient without requiring knowledge of the coupled resonant frequency of the input resonant circuit. Specifically, the two formulas previously presented are used together to generate an estimate of the coupling coefficient based on the coupled resonant frequency of the output resonant circuit and the two uncoupled resonant frequencies.

[0196] It will be understood that the exact formulas and equations used to determine the estimates of the coupling coefficients may vary depending on the specific choices and requirements of each embodiment. In many embodiments, a favorable and efficient method for generating estimates of the coupling coefficients is obtained by manipulating and simplifying the previously presented equations based on various assumptions or simplifications.

[0197] In many embodiments, the estimator 309 is configured to determine an estimate of the coupling coefficients in relation to the first coupling resonance frequency relative to the second coupling resonance frequency.

[0198] In particular, in many embodiments, the estimator 309 is configured to determine an estimate of the coupling coefficient based on the ratio of the first coupling resonant frequency to the second coupling resonant frequency. In many embodiments, the estimate of the coupling coefficient is determined as a function of the ratio of the first coupling resonant frequency to the second coupling resonant frequency. In some embodiments, this function depends only on either the first or second coupling resonant frequency by depending on the ratio between the coupling resonant frequencies, and this function does not consider the first or second coupling resonant frequencies separately. In some embodiments, this function can be modified or rearranged so that the first and second coupling resonant frequencies are included only as a ratio between the coupling resonant frequencies.

[0199] In many embodiments, the estimator 309 is configured to determine an estimate of the coupling coefficient, which is a function of a dimensionless parameter (specifically, a ratio between frequencies) determined from the first and second coupling resonant frequencies. The dependence on the first and / or second coupling resonant frequencies depends solely on the dimensionless parameter, specifically the ratio.

[0200] In particular, while the first and second coupled resonant frequencies change significantly as a function of various parameters such as the load and effective quality coefficient and coil characteristics when performing the measurement, it is recognized that such changes can be mitigated and compensated for by determining the estimated coupling coefficient in relation to the relationship between the first and second coupled resonant frequencies, specifically, the relationship between these relationships. Specifically, the sensitivity of the uncoupled resonant frequencies of the input and output resonant circuits to the changes when determining the estimated coupling coefficient is greatly reduced by determining the estimated coupling coefficient, which is a function of the ratio of the first coupled resonant frequency to the second coupled resonant frequency.

[0201] The coupling coefficients are determined using the following functions in some embodiments, as specific examples.

number

[0202] This function has been found to achieve particularly advantageous performance when the uncoupled resonance frequencies of the input resonance circuit and the output resonance circuit are substantially similar. In particular, it has been found that using the ratio between frequencies significantly reduces the sensitivity to measurement errors and inaccuracies. Furthermore, using the simplified equation as described above makes the evaluation easier, thereby facilitating implementation and / or operation. For example, in some embodiments, only one LUT is implemented based on the ratio between the frequencies used as input for look-up.

[0203] In many embodiments, the estimator 309 is configured to determine an estimated value of the coupling coefficient according to the uncoupled resonance frequency of the input resonance circuit and / or the output resonance circuit, as previously described. This determination is used, for example, together with the determination of the estimated value of the coupling coefficient based on the ratio between the coupling resonance frequencies, and is particularly used to modify the above equation.

[0204] In many embodiments, the estimator 309 is configured to determine an estimated value of the coupling coefficient according to the ratio of the uncoupled resonance frequency of the output resonance circuit to the uncoupled resonance frequency of the input resonance circuit. By considering the ratio between the uncoupled resonance frequencies, particularly advantageous operation becomes possible, and it has been recognized that, in particular, the sensitivity to changing and often unknown parameters is reduced.

[0205] In many embodiments, the estimated value of the coupling coefficient is determined as a function of the ratio between the first coupling resonance frequency and the second coupling resonance frequency, and the ratio between the uncoupled resonance frequencies of the input resonance circuit and the output resonance circuit. [Number] Here, the shown f r is the uncoupled resonance frequency of the input resonance circuit, f tF1 is the uncoupled resonant frequency of the output resonant circuit, F1 is the highest coupled resonant frequency, and F2 is the lowest coupled resonant frequency.

[0206] The following are particularly advantageous functions for estimating the join function:

number

number

number

[0207] If β=1, solving the previous equation gives the following:

number

[0208] Alternatively, this function can be expressed as follows:

number

[0209] The following equation can be derived from the previously presented equation, assuming the load of the input resonant circuit is short-circuited.

number

number

number

number

number

number

number

number

number

number

number

number

number

[0210] Another example of a particularly advantageous function for estimating the coupling function is as follows. [Number]

[0211] Therefore, in some embodiments, the estimator 309 is configured to determine an estimated value of the coupling coefficient according to the ratio of the sum of the squares of the first and second uncoupled resonance frequencies to the sum of the squares of the first and second coupled resonance frequencies.

[0212] In many embodiments, the estimated coupling coefficient is determined as a function of the ratio of the sum of the squares of the uncoupled resonance frequency and the coupled resonance frequency. In some embodiments, this function depends on this ratio, depends only on the resonance frequency, and this function does not consider the coupled resonance frequency or the uncoupled resonance frequency except for such a ratio. In some embodiments, this function is a function that can be processed or rearranged so that the resonance frequency is included only as the ratio of the sum of the squares of the coupled resonance frequency and the sum of the squares of the uncoupled resonance frequency.

[0213] In many embodiments, the estimator 309 is configured to determine an estimated value of the coupling coefficient that is a function of dimensionless parameters (specifically, ratios between frequencies or squares of frequencies, etc.) determined from the first and second coupled resonance frequencies and the first and second coupled resonance frequencies. The dependence on the first coupled resonance frequency and / or the second coupled resonance frequency, and / or the first uncoupled resonance frequency and / or the second uncoupled resonance frequency depends only on dimensionless parameters, specifically ratios.

[0214] Such an approach has been found to be particularly advantageous, resulting in improved robustness and reduced sensitivity to environmental changes, component variations, measurement errors, etc.

[0215] The above equation is specifically derived from the two previously presented equations using suitable assumptions and simplifications.

Number

[0216] More specifically, starting from the system equation of the electrical equivalent circuit in FIG. 16, the First Harmonic Approximation is derived.

Number

[0217] i t and i r The system equation for this is determined, and then the positions of the peaks and troughs of the transfer function are determined based on the following equation.

number

[0218] Keep only the numerator of this equation, R L Set = 0 (i.e., short-circuit the load of the power receiver),

number

number

number

Number

[0219] In this equation,

Number

Number

Number

Number

[0220] Setting the second term of this equation to zero gives the position of the valley (minimum), i.e., f = β, or equivalently, ω = ω’. r is obtained. Setting the fourth term of this equation to zero gives the positions of the two peaks (minima). That is,

number

number

[0221] By splitting the two results and reworking them to separate the coupling coefficients, we obtain the following equation.

number

[0222] In this equation, T is the ratio of the two resonant frequencies (the positive solution divided by the negative solution).

[0223] Adding the two results yields the following equation.

number

number

number

[0224] The uncoupled resonant frequency ω' of the output resonant circuit. t This is derived by measuring the peak position (maximum value) of the current in the output resonant circuit with the load of the power receiver disconnected. Uncoupled resonant frequency ω' r This is derived by measuring the position (minimum) of the trough between the two resonant peaks of the output resonant circuit's current.

[0225] It will be understood that deviations from the assumptions (for example, replacing a short circuit in a series input resonant circuit with a lower resistance value) will cause some differences, and in some cases, determine frequencies that differ from the theoretical values. However, in many embodiments, such differences are acceptable or even negligible. In fact, it has been found that even when the deviation is relatively large, this method, along with the use of simplified mathematical formulas and relationships, allows for favorable and useful estimation of coupling coefficients.

[0226] In some embodiments, the power transmitter is configured to determine an index or degree of misalignment of the power receiver relative to the power transmitter (specifically, the receiver coil 107 relative to the transmitter coil 103). Specifically, the lower the coupling coefficient, the greater the misalignment. Furthermore, in such embodiments, the power transmitter is configured to generate an output to the user indicating the misalignment. Specifically, the power transmitter provides the user with a warning indicating that the position of the power receiver needs to be changed if the coupling coefficient falls below a threshold.

[0227] It will be understood that the above description has, for clarity, illustrated embodiments of the present invention with reference to various functional circuits, units, and processors. However, it will be clear that any preferred form of distribution of functionality may be used among various functional circuits, units, or processors without departing from the present invention. For example, functionality shown to be performed by separate processors or controllers may be performed by the same processor or controller. Therefore, references to specific functional units or circuits should be considered not as indicating a strict logical or physical structure or configuration, but merely as references to preferred means of realizing the described functionality.

[0228] The present invention can be implemented in any preferred form, including hardware, software, firmware, or any combination thereof. The present invention may optionally be implemented as computer software operating at least partially on one or more data processors and / or digital signal processors. Elements and components of one embodiment of the present invention may be implemented physically, functionally, and logically in any preferred manner. The function may actually be implemented in just one unit, in multiple units, or as part of other functional units. The present invention may therefore be implemented in just one unit or physically and functionally distributed across various units, circuits, and processors.

[0229] Although the present invention has been described in relation to several embodiments, it is not intended to be limited to any particular form described herein. Rather, the scope of the present invention is limited solely by the appended claims. Furthermore, although features appear to be described in relation to a particular embodiment, those skilled in the art will recognize that various features of the described embodiments may be combined in accordance with the present invention. In the claims, the term “including” does not preclude the existence of other elements or steps.

[0230] Furthermore, while multiple means, elements, circuits, or steps of a method are listed individually, they may, for example, be carried out by only one circuit, unit, or processor. Moreover, while individual features are included in different claims, they may be advantageously combined as needed, and inclusion in different claims does not imply that the combination of features is impossible and / or unfavorable. Also, the inclusion of a feature in one category of a claim does not imply limitation to that category, but rather indicates that the feature may similarly apply to other claim categories as needed. The inclusion of a feature in a dependent claim of an independent claim does not imply limitation to that independent claim, but rather indicates that the feature may similarly apply to other independent claims as needed. Furthermore, the order of features in a claim does not imply any particular order in which the features must be performed, and in particular, the order of individual steps in a method claim does not imply that the steps must be performed in that order. The steps may rather be performed in any preferred order. In addition, singular references do not exclude plurals. Therefore, references to "first," "second," etc., do not exclude multiple references. Reference numerals in the claims are provided merely to clarify examples and shall not be construed as limiting the scope of the claims.

[0231] In some scenarios, a power transmitter (101) is provided that wirelessly supplies power to a power receiver (105) via an inductive power transmission signal. The power transmitter (101) is, An output resonant circuit comprising a transmitter coil (103) and at least one capacitor (303), A driver (201) is configured to generate a drive signal for the output resonant circuit (103) and an inductive power transmission signal, A resonance detector (307) configured to measure a first coupled resonance frequency of an output resonant circuit during the resonance measurement period, wherein the first coupled resonance frequency is the resonance frequency of the output resonant circuit of a transmitter coil (103) coupled to a receiver coil (107) of the power transmission input resonant circuit of a power receiver (105), and the power transmission input resonant circuit has a quality factor of 10 or more during the resonance measurement period, and the resonance detector (307) An estimation circuit (309) is configured to determine an estimated value of the coupling coefficient between the transmitter coil (103) and the receiver coil (107) according to the first coupling resonance frequency, The system comprises an adapter (311) configured to set operating parameters according to estimated coupling coefficients.

[0232] A method for operating a power transmitter (101) that wirelessly supplies power to a power receiver (105) via an inductive power transmission signal, wherein the power transmitter (101) comprises an output resonant circuit having a transmitter coil (103) and at least one capacitor (303), This delicious, The steps include generating a drive signal for the output resonant circuit (103) and generating an inductive power transmission signal, A step of determining the first coupled resonant frequency of the output resonant circuit during the resonance measurement period, wherein the first coupled resonant frequency is the resonant frequency of the output resonant circuit of the transmitter coil (103) coupled to the receiver coil (107) of the power transmission input resonant circuit of the power receiver (105), and the power transmission input resonant circuit has a quality factor of 10 or more during the resonance measurement period. The steps include determining an estimated coupling coefficient for the coupling between the transmitter coil (103) and the receiver coil (107) according to the first coupling resonance frequency, The process includes the step of setting operating parameters according to the estimated values ​​of the coupling coefficients.

Claims

1. A wireless power transmission system comprising a power transmitter and a power receiver, wherein the power transmitter wirelessly supplies power to the power receiver via an inductive power transmission signal. The aforementioned power transmitter, An output resonant circuit comprising a transmitter coil and at least one capacitor, The output resonant circuit includes a driver that generates a drive signal for generating the inductive power transmission signal, A resonance detector for determining the first coupled resonance frequency of the output resonance circuit during the resonance measurement period, wherein the first coupled resonance frequency is the resonance frequency of the output resonance circuit of the transmitter coil coupled to the receiver coil of the power transmission input resonance circuit of the power receiver, An estimation circuit that determines an estimated value of the coupling coefficient between the transmitter coil and the receiver coil according to the first coupling resonance frequency, The adapter sets the operating parameters according to the estimated value of the coupling coefficient. It is equipped with, The aforementioned power receiver A power transmission input resonant circuit comprising a receiver coil configured to extract power from the power transmitter and at least one capacitor, wherein the power transmission input resonant circuit has a quality factor of 10 or more during the resonance measurement period, A circuit that switches from a power transmission mode in which the quality factor is not limited to 10 or more, to a measurement mode in which the quality factor becomes 10 or more, by disconnecting or short-circuiting the load connected to the power transmission input resonant circuit while the power receiver is operating in measurement mode during the resonance measurement period, and A wireless power transmission system equipped with the following features.

2. The wireless power transmission system according to claim 1, wherein the resonance detector further measures a second coupled resonance frequency of the output resonant circuit during the resonance measurement period, the second coupled resonance frequency being another resonance frequency of the output resonant circuit in the presence of the power receiver, and the estimation circuit further determines an estimated value of the coupling coefficient according to the second coupled resonance frequency.

3. The wireless power transmission system according to claim 2, wherein the first coupling resonance frequency and the second coupling resonance frequency are frequencies at which the current of the drive signal shows a maximum value.

4. The wireless power transmission system according to any one of claims 1 to 3, wherein the estimation circuit further determines the coupling coefficient according to the uncoupled resonant frequency of the output resonant circuit and the uncoupled resonant frequency of the power transmission input resonant circuit.

5. The wireless power transmission system according to any one of claims 1 to 3, wherein the estimation circuit further determines the coupling coefficient according to the ratio of the uncoupled resonant frequency of the output resonant circuit to the uncoupled resonant frequency of the power transmission input resonant circuit.

6. The wireless power transmission system according to any one of claims 1 to 3, wherein the estimation circuit further determines the coupling coefficient according to the ratio of the sum of the squares of the uncoupled resonant frequency of the output resonant circuit and the uncoupled resonant frequency of the power transmission input resonant circuit and the sum of the squares of the first coupled resonant frequency and the second coupled resonant frequency, which is the resonant frequency of the output resonant circuit of the transmitter coil coupled to the receiver coil.

7. The wireless power transmission system according to any one of claims 1 to 6, wherein the resonance detector determines that the uncoupled resonance frequency of the output resonance circuit is a frequency that shows a maximum value for the power transmission input resonance circuit having the quality coefficient of 2 or less for which the current of the drive signal is 2, and the estimation circuit determines the coupling coefficient according to the uncoupled resonance frequency of the output resonance circuit.

8. The wireless power transmission system according to any one of claims 1 to 7, wherein the resonance detector determines that the uncoupled resonance frequency of the power transmission input resonant circuit is a frequency at which the current of the drive signal shows a minimum value for the power transmission input resonant circuit having a quality coefficient of 10 or more, and the estimation circuit determines the coupling coefficient according to the uncoupled resonance frequency of the power transmission input resonant circuit.

9. The wireless power transmission system according to any one of claims 1 to 8, wherein the resonance measurement period is during the initialization of the power transmission operation, and the operation parameter is the initial operation parameter of the power transmission operation.

10. The wireless power transmission system according to any one of claims 1 to 9, wherein the driver generates the drive signal according to a repetitive time frame that includes at least one power transmission period and at least one measurement period in the power transmission stage, and the resonance measurement period is included in the measurement period.

11. The wireless power transmission system according to any one of claims 1 to 10, wherein the operating parameter is a power loop parameter, which is a loop parameter of a power control loop that adjusts the power level of the inductive power transmission signal in response to a power control message received from the power receiver.

12. A method for operating a wireless power transmission system comprising a power transmitter and a power receiver, wherein the power transmitter wirelessly supplies power to the power receiver via an inductive power transmission signal, The power transmitter comprises an output resonant circuit comprising a transmitter coil and at least one capacitor, and the power receiver comprises a power transmission input resonant circuit comprising a receiver coil that extracts power from the power transmitter and at least one capacitor. The above operating method is such that the power transmitter The steps include generating a drive signal for the output resonant circuit and generating the inductive power transmission signal, A step of determining a first coupled resonant frequency of the output resonant circuit during the resonance measurement period, wherein the first coupled resonant frequency is the resonant frequency of the output resonant circuit of the transmitter coil coupled to the receiver coil of the power transmission input resonant circuit of the power receiver, and the power transmission input resonant circuit has a quality factor of 10 or more during the resonance measurement period, The steps include determining an estimated coupling coefficient for the coupling between the transmitter coil and the receiver coil according to the first coupling resonance frequency, The steps include setting the operating parameters according to the estimated value of the coupling coefficient, and Execute, The above operating method involves the power receiver, An operating method comprising the step of switching from a power transmission mode in which the quality factor is not limited to 10 or more, to a measurement mode in which the quality factor becomes 10 or more, by disconnecting or short-circuiting the load connected to the power transmission input resonant circuit while the power receiver is operating in measurement mode during the resonance measurement period.

13. A power receiver for a wireless power transmission system comprising a power transmitter and a power receiver, wherein the power transmitter wirelessly supplies power to the power receiver via an inductive power transmission signal, The aforementioned power receiver A power transmission input resonant circuit comprising a receiver coil configured to extract power from the power transmitter and at least one capacitor, A circuit that switches from a power transmission mode in which the quality factor is not limited to 10 or more, to a measurement mode in which the quality factor is 10 or more, by disconnecting or short-circuiting the load connected to the power transmission input resonant circuit while the power receiver is operating in measurement mode during the resonant measurement period, and A power receiver equipped with the following:

14. A method for operating a power receiver for a wireless power transmission system comprising a power transmitter and a power receiver, wherein the power transmitter wirelessly supplies power to the power receiver via an inductive power transmission signal, and the power receiver comprises a power transmission input resonant circuit comprising a receiver coil and at least one capacitor configured to extract power from the power transmitter, The above operating method includes the step of switching the circuit from a power transmission mode in which the quality factor is not limited to 10 or more, to a measurement mode in which the quality factor is 10 or more, by disconnecting or short-circuiting the load connected to the power transmission input resonant circuit while the power receiver is operating in measurement mode during the resonant measurement period.

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