Electronic devices with frequency dithering and ripple reduction

Abstract

This application relates in general to electronic devices, and more specifically to electronic devices having an inverter. [Solution] An electronic device configured to transmit wireless power to an additional electronic device may include a wireless power transmission coil, an inverter configured to receive a switching signal based on a dithered clock signal and output a corresponding AC signal to the wireless power transmission coil, and a control circuit that generates a dithered clock signal. The dithered clock signal may have multiple frequency steps. The duty cycle of the switching signal may differ between at least two different frequency steps to compensate for the different gains of wireless power transmission from the electronic device to the additional electronic device in at least two different frequency steps.

Description

[Technical Field]

[0001] (Cross-reference of related applications) This application claims priority to U.S. Provisional Application No. 63 / 735,735, entitled “Electronic Device with Frequency Dithering and Variable Timing Properties,” filed on 18 December 2024, and U.S. Provisional Application No. 63 / 847,620, entitled “Electronic Device with Frequency Dithering and Ripple Mitigation,” filed on 21 July 2025, each of which is incorporated herein by reference in whole.

[0002] This application relates in general to electronic devices, and more specifically to electronic devices having an inverter. [Background technology]

[0003] Electronic devices may include inverters that convert direct current (DC) power to alternating current (AC) power. An inverter can use a clock signal of a given frequency to output a corresponding AC signal. Improving the electromagnetic compatibility of the inverter is desirable. [Overview of the project]

[0004] An electronic device configured to transmit wireless power to an additional electronic device may include a wireless power transmission coil, an inverter configured to receive a switching signal based on a dithered clock signal and output a corresponding AC signal to the wireless power transmission coil, and a control circuit that generates the dithered clock signal. The dithered clock signal may have multiple frequency steps. The timing characteristics of one or more switching signals may differ between at least two different frequency steps to compensate for different wireless power transmission gains in at least two different frequency steps.

[0005] The inverter may include four transistors controlled by two switching signals.

[0006] The timing characteristics can include the operating phase of the inverter. The timing characteristics can also include the duty cycle of the switching signal.

[0007] The control circuit may be configured to select one or more timing characteristics of at least two different frequency steps based on real-time operating conditions determined by communicating with an additional electronic device. The real-time operating conditions may include received power information from the additional electronic device. The control circuit may be configured to receive received power information from the additional electronic device using a wireless power transmission coil. The received power information may include calibration measurements of the rectifier voltage and rectifier current of the additional electronic device at multiple operating frequencies, duty cycles, and power levels. The control circuit may calculate one or more gain values ​​based at least partially on the calibration measurements. The received power information may include runtime measurements of the rectifier power and rectifier voltage of the additional electronic device. The control circuit may calculate one or more timing characteristic values ​​based at least partially on the runtime measurements. The real-time operating conditions may include ripple messages reported by the additional electronic device.

[0008] The control circuit can be configured to receive the magnitude of the ripple from an additional electronic device using a wireless power transmission coil. The control circuit can select one or more timing characteristics of at least two different frequency steps based on real-time operating conditions determined without communication with the additional electronic device. The real-time operating conditions can include the inverter input voltage ripple measured by the control circuit. If one or more of the timing characteristics include a duty cycle, the control circuit can increment or decrement the duty cycle in response to a comparison of the inverter input voltage ripple measured by the control circuit with a threshold, a determination of whether the ripple voltage is increasing or decreasing over time, and a determination of whether the duty cycle is increasing or decreasing over time.

[0009] The dithered clock signal can have a plurality of frequency steps in an iterative cycle. The iterative cycle of the dithered clock signal can include a step function that approximates the waveform. The dithered clock signal can have a unique frequency magnitude for each of the plurality of frequency steps during the iterative cycle. The waveform can include a triangular waveform. The plurality of frequency steps in the iterative cycle can include 32 frequency steps in the iterative cycle.

[0010] An electronic device can include a wireless power transmission coil, an inverter configured to receive a switching signal based on a dithered clock signal and output a corresponding alternating current signal to the wireless power transmission coil, and a control circuit configured to generate the dithered clock signal. The dithered clock signal can have a plurality of frequency steps having magnitudes of a unique frequency. The dithered clock signal can have unique timing characteristics for at least two of the plurality of frequency steps selected to compensate for different wireless power transmission gains at at least two different frequency steps. The unique timing characteristics can include the operating phase of the inverter. The unique timing characteristics can include a duty cycle. The control circuit can be configured to select the unique timing characteristics of at least two different frequency steps based on real-time operating conditions determined in communication with an additional electronic device. The control circuit can select the unique timing characteristics of at least two different frequency steps based on real-time operating conditions determined without communication with an additional electronic device.

Brief Description of the Drawings

[0011] [Figure 1] It is a schematic diagram of an exemplary wireless power system according to some embodiments.

[0012] [Figure 2] It is a circuit diagram of an exemplary wireless power transmission circuit and a wireless power reception circuit in a wireless power system according to some embodiments.

[0013] [Figure 3] It is a circuit diagram of an exemplary inverter according to some embodiments.

[0014] [Figure 4] It is a schematic diagram of an exemplary electronic device including a dithering circuit according to some embodiments.

[0015] [Figure 5] This is a graph of an exemplary dithered clock signal in several embodiments.

[0016] [Figure 6] This is a graph of an exemplary modulated signal according to several embodiments.

[0017] [Figure 7] Figure 5 shows a graph of radiation as a function of frequency of an exemplary dithered clock signal, according to several embodiments.

[0018] [Figure 8A] This is a graph of the duty cycle as a function of time while an exemplary wireless power transmission circuit, according to several embodiments, operates with a constant duty cycle.

[0019] [Figure 8B] This is a graph of the rectifier output voltage of an exemplary receiving device as a function of time, while the transmitting device uses the frequency shown in Figure 5 and the constant duty cycle shown in Figure 8A, according to several embodiments.

[0020] [Figure 9A] This is a graph of the duty cycle as a function of time while an exemplary wireless power transmission circuit, according to several embodiments, operates with a fluctuating duty cycle.

[0021] [Figure 9B] This is a graph of the rectifier output voltage of an exemplary receiving device as a function of time, while the transmitting device uses the frequency shown in Figure 5 and the fluctuating duty cycle shown in Figure 9A, according to several embodiments.

[0022] [Figure 10] This is an exemplary graph illustrating how the duty cycle of an inverter can vary at each frequency step in several embodiments.

[0023] [Figure 11A] This is an illustrative timing diagram of inverter control signals when the inverter has different operating phases, according to several embodiments. [Figure 11B] This is an illustrative timing diagram of inverter control signals when the inverter has different operating phases, according to several embodiments.

[0024] [Figure 12] This is a state diagram of an exemplary power transmission circuit having multiple operating modes according to several embodiments.

[0025] [Figure 13] This flowchart shows exemplary methods for operating a power transmission device according to several embodiments.

[0026] [Figure 14] This is a simplified equivalent circuit model of a wireless power transmission system.

[0027] [Figure 15] This is a simplified flowchart of the first duty compensation technology.

[0028] [Figure 16] This is a simplified flowchart of the startup calibration stage of the first duty cycle compensation technology.

[0029] [Figure 17] This is a simplified flowchart of the runtime duty cycle calculation stage of the first duty cycle compensation technology.

[0030] [Figure 18] This is a simplified flowchart of the second duty cycle compensation technology.

[0031] [Figure 19]This plot shows the ripple voltage versus duty cycle when using the second duty cycle compensation technique. [Modes for carrying out the invention]

[0032] An exemplary wireless power system (sometimes called a wireless charging system) is shown in Figure 1. As shown in Figure 1, the wireless power system 8 may include one or more wireless power transmission devices, such as a wireless power transmission device 12, and one or more wireless power receiving devices, such as a wireless power receiving device 24. The wireless power system 8 may also be referred to herein as a wireless power transmission (WPT) system 8 or wireless power system 8. The wireless power transmission device 12 may also be referred herein as a power transmitter (PTX) device 12 or simply PTX 12. The wireless power receiving device 24 may also be referred herein as a power receiver (PRX) device 24 or simply PRX 24.

[0033] The PTX device 12 includes a control circuit 16, which is mounted within a housing 30. The PRX device 24 includes a control circuit 38, which is mounted within a corresponding housing 52 for the PRX device 24. Exemplary control circuits 16 and 38 are used to control the operation of the WPT system 8. This control circuit may include a processing circuit that includes one or more processors, such as a microprocessor, a power management unit, a baseband processor, a digital signal processor, a microcontroller, a graphics processing unit (GPU), a central processing unit (CPU), an application processor (AP), an application-specific integrated circuit with processing circuits, and / or other processing circuits. The processing circuit implements desired control and communication functions within the PTX device 12 and the PRX device 24. For example, the processing circuit may be used to control power to one or more coils, determine and / or set power transmission levels, generate and / or process sensor data (e.g., to detect foreign objects and / or external electromagnetic signals or electromagnetic fields), process user input, handle negotiation between the PTX device 12 and the PRX device 24, send and receive in-band and out-of-band data, perform measurements, and / or control the operation of the WPT system 8.

[0034] The control circuits within the WPT system 8 (e.g., control circuits 16 and / or 38) may be configured to perform operations within the WPT system 8 using hardware (e.g., dedicated hardware or circuitry), firmware, and / or software. The software code for performing operations within the WPT system 8 is stored on a non-temporary computer-readable storage medium (e.g., a tangible computer-readable storage medium) within the control circuits of the WPT system 8. The software code may be referred to as software, data, program instructions, instructions, or code. The non-temporary computer-readable storage medium may include non-volatile memory such as non-volatile random-access memory (NVRAM), one or more hard drives (e.g., magnetic drives or solid-state drives), one or more removable flash drives, or other removable media. The software stored on the non-temporary computer-readable storage medium can be executed on the processing circuits of control circuits 16 and / or 38.

[0035] The PTX device 12 may be a standalone power adapter (e.g., a wireless charging mat or charging pack including a power adapter circuit), a wireless charging mat or pack connected by cable to a power adapter or other device, an electronic device (e.g., a laptop computer, a desktop computer, a computer monitor with a built-in embedded computer, a tablet computer, a cellular phone, a media player, or other handheld or portable electronic device, a small device such as a wristwatch device, a pendant device, headphones or earphone devices, glasses, goggles, or a device incorporated into other equipment worn on the user's head, or other wearable or miniature devices, a television, a computer display without a built-in embedded computer, a gaming device, a navigation device, a wireless internet-connected voice-controlled speaker, a home entertainment device, a remote control device, a gaming controller, a peripheral user input device, a wireless base station or access point, equipment implementing two or more functions of these devices, or other electronic equipment), equipment incorporated into furniture, a vehicle, or other system, a removable battery case, or other wireless power transmission equipment.

[0036] The PRX device 24 may be an electronic device such as a laptop computer, desktop computer, computer monitor including an embedded computer, tablet computer, cellular telephone, media player, or other handheld or portable electronic device; a wristwatch device, pendant device, headphone device or earphone device, a device embedded in eyeglasses or goggles or other device worn on the user's head, or a small device such as other wearable devices or miniature devices; a wireless tracking tag, television, computer display not including an embedded computer, gaming device, navigation device, internet-connected voice-controlled wireless speaker, home entertainment device, remote control device, gaming controller, peripheral user input device, wireless base station or access point, a device that implements two or more functions of these devices, or other electronic equipment.

[0037] The PTX device 12 may be connected to a wall outlet (e.g., an AC power source), coupled to a wall outlet via an external power adapter, have a battery for power supply, and / or have another power source. In an implementation where the PTX device 12 is coupled to a wall outlet via an external power adapter, the adapter may have an AC-DC power converter that converts alternating current (AC) power from the wall outlet or other power source to direct current (DC) power. If necessary, the PTX device 12 may include a DC-DC power converter for converting DC power between different DC voltages. Additionally or alternatively, the PTX device 12 may include an AC-DC power converter that generates DC power from AC power provided by a wall outlet (e.g., in an implementation where the PTX device 12 is connected to a wall outlet without an external power adapter). DC power can be used to power the control circuit 16. During operation, the controller in the control circuit 16 transmits wireless power to the power receiving circuit 46 of the PRX device 24 using the power transmission circuit 22.

[0038] The power transmission circuit 22 may have a switching circuit (e.g., an inverter circuit 26 formed from transistors) that is turned on and off based on a control signal supplied by the control circuit 16 to generate an AC current signal via one or more wireless power transmission coils, such as the wireless power transmission coil 32. These coil drive signals cause the coil(s) 32 to transmit wireless power. In implementations where the coil(s) 32 includes multiple coils, the coils may be arranged on a ferromagnetic structure, arranged in a planar coil array, or arranged to form a cluster of coils (e.g., two or more coils, 5 to 10 coils, at least 10 coils, 10 to 30 coils, fewer than 35 coils, fewer than 25 coils, or any other appropriate number of coils). In some implementations, the PTX device 12 includes only a single coil 32.

[0039] When an AC current flows through one or more coils 32, an AC electromagnetic field (e.g., a magnetic field) (a radio power signal 44) is generated, which is received by one or more corresponding receiving coils, such as one or more coils 48 in the PRX device 24. In other words, one or more of the coils 32 are inductively coupled to one or more of the coils 48. The PRX device 24 may have a single coil 48, at least two coils 48, at least three coils 48, at least four coils 48, or any other preferred number of coils 48. When an AC electromagnetic field is received by one or more coils 48, a corresponding AC current is induced in one or more coils 48. The AC signal used when transmitting radio power can have any desired frequency (e.g., 100-400 kHz, 1-100 MHz, 1.7 MHz-1.8 MHz, less than 2 MHz, 100 kHz-2 MHz, 6.78 MHz, 13.56 MHz, etc.). A rectifier circuit, such as a rectifier circuit 50, which includes rectifier components such as synchronous rectifier transistors located within the bridge network, converts the received AC signal (the received AC signal associated with the radio power signal 44) into a DC voltage signal for supplying power to the PRX device 24 from one or more coils 48. The radio power signal 44 may be referred to herein as radio power 44 or radio charging signal 44. The coil 32 may be referred herein as a radio power transmission coil 32, a radio charging coil 32, or a radio power transmission coil 32. The coil 48 may be referred herein as a radio power transmission coil 48, a radio charging coil 48, or a radio power receiving coil 48.

[0040] The DC voltage generated by the rectifier circuit 50 (sometimes called the rectifier output voltage Vrect) may be used to charge a battery such as the battery 34, or to supply power to other components in the PRX device 24, such as the control circuit 38 and the input / output (I / O) device 54. The PTX device 12 may also include input / output devices such as the input / output device 28. The input / output device 54 and / or the input / output device 28 may include input devices for collecting user inputs and / or performing environmental measurements, and may include output devices for providing outputs to the user.

[0041] For example, input / output devices 28 and / or 54 may include a display (screen) for generating a visual output, a speaker for presenting the output as an audio signal, a light-emitting diode status indicator light and other light-emitting components for emitting light to provide status information and / or other information to the user, a tactile device for generating vibration and other tactile outputs, and / or other output devices. Input / output devices 28 and / or 54 may also include sensors for collecting user input and / or making measurements of the surroundings of the WPT system 8.

[0042] The example of a PRX device 24 including a battery 34 in Figure 1 is illustrative. More generally, the electronic device may include an energy storage device 34. The energy storage device 34 may be a battery or, for example, a supercapacitor that stores electric charge.

[0043] The PTX device 12 and the PRX device 24 can communicate wirelessly using in-band or out-of-band communication. Implementations using in-band communication, for example, can utilize frequency-shift keying (FSK) and / or amplitude-shift keying (ASK) techniques to communicate in-band data between the PTX device 12 and the PRX device 24. Wireless power and in-band data transmission can be carried using coils 32 and 48 simultaneously. When the PTX 12 transmits in-band data to the PRX 24, the wireless transceiver (TX / RX) circuit 20 can modulate the wireless charging signal 44 to provide FSK or ASK communication, and the wireless transceiver circuit 40 can demodulate the wireless charging signal 44 to obtain the transmitted data. When the PRX 24 transmits in-band data to the PTX 12, the wireless transceiver (TX / RX) circuit 40 can modulate the wireless charging signal 44 to provide FSK or ASK communication, and the wireless transceiver circuit 20 can demodulate the wireless charging signal 44 to obtain the transmitted data.

[0044] Implementations using out-of-band communication can utilize, for example, a hardware antenna structure and a communication protocol such as Bluetooth or NFC to communicate out-of-band data between the PTX device 12 and the PRX device 24. Power can be wirelessly carried between coils 32 and 48 simultaneously with the transmission of out-of-band data. The wireless transceiver circuit 20 can wirelessly transmit and / or receive out-of-band signals to and / or from the PRX device 24 using an antenna such as antenna 56. The wireless transceiver circuit 40 can wirelessly transmit and / or receive out-of-band signals to and / or from the PTX device 12 using an antenna such as antenna 58.

[0045] Antennas 56 and 58 are connected to wireless local area network (WLAN) communication bands such as the 2.4GHz and 5GHz Wi-Fi® (IEEE802.11) bands, wireless personal area network (WPAN) communication bands such as the 2.4GHz Bluetooth® band, cellular low band (LB) (e.g., 600~960MHz), cellular low-midband (LMB) (e.g., 1400~1550MHz), cellular midband (MB) (e.g., 1700~2200MHz), cellular high band (HB) (e.g., 2300~2700MHz), cellular ultra-high band (UHB) (e.g., 3300~5000MHz), or other cellular communication bands of approximately 600MHz to approximately 5000MHz (e.g., 3G band, 4G band). It can handle cellular telephone communication bands such as LTE bands and 5G Frequency Range 1 (FR1) bands below 10GHz, near-field communications (NFC) bands (e.g., at 13.56MHz), satellite navigation bands (e.g., L1 global positioning system (GPS) band at 1575MHz, L5 GPS band at 1176MHz, Global Navigation Satellite System (GLONASS) band, BeiDou Navigation Satellite System (BDS) band, etc.), ultra-wideband (UWB) communication bands (one or more) supported by the IEEE 802.15.4 protocol, and / or other UWB communication protocols (e.g., a first UWB communication band at 6.5GHz and / or a second UWB communication band at 8.0GHz), and / or any other desired communication band.

[0046] Antennas 56 and 58 can support communication in the extremely high frequency (EHF) or millimeter-wave communication band of approximately 30 GHz to 300 GHz, and / or in the centimeter-wave communication band of approximately 10 GHz to 30 GHz (sometimes called the super high frequency (SHF) band). For example, antennas 56 and 58 can support communication in the IEEE K communication band of approximately 18 GHz to 27 GHz, and the K band of approximately 26.5 GHz to 40 GHz. a Communication bandwidth, approximately 12GHz~18GHz K u The communication band can support communication in the V communication band of approximately 40GHz to 75GHz, the W communication band of approximately 75GHz to 110GHz, or any other desired frequency band of approximately 10GHz to 300GHz. If desired, the millimeter-wave / centimeter-wave transceiver circuit can support IEEE 802.11ad communication at 60GHz (e.g., the WiGig or 60GHz Wi-Fi band around 57-61GHz) and / or the 5th generation mobile network or 5th generation wireless system (5G) new radio (NR) frequency range 2 (FR2) communication band of approximately 24GHz to 90GHz.

[0047] Antennas 56 and 58 may include antennas having resonant elements formed from loop antenna structures, patch antenna structures, inverted F antenna structures, slot antenna structures, planar inverted F antenna structures, helical antenna structures, dipole antenna structures, monopole antenna structures, or hybrids of these designs. Different types of antennas may be used for different bandwidths and combinations of bandwidths. For example, one type of antenna may be used to form a local radio link, and another type of antenna may be used to form a remote radio link antenna.

[0048] Each of the housings 30 and 52 can be formed from plastic, metal, fiber composite materials such as carbon fiber materials, wood and other natural materials, glass, other materials, and / or combinations of two or more of these materials.

[0049] The example in Figure 1, where PTX 12 transmits wireless power and PRX 24 receives wireless power, is merely illustrative. PTX 12 can optionally receive wireless power signals using one or more coils 32, and PRX 24 can optionally transmit wireless power signals using one or more coils 48. When a device is capable of both transmitting and receiving wireless power signals, the device may include both an inverter and a rectifier.

[0050] Figure 2 is a schematic diagram of an exemplary wireless charging circuit for system 8. As shown in Figure 2, the circuit 22 may include an inverter circuit, such as one or more inverters 26, or other drive circuits that generate a wireless power signal transmitted via an output circuit, such as one or more coils 32 and a capacitor, such as a capacitor 70. In some embodiments, the device 12 may include a plurality of individually controlled inverters 26, each supplying a drive signal to an individual coil 32. In other embodiments, the inverters 26 are shared among the plurality of coils 32 using a switching circuit.

[0051] During operation, control signals for one or more inverters 26 are provided by the control circuit 16 at control inputs 74. While a single inverter 26 and a single coil 32 are shown in the embodiment of Figure 2, multiple inverters 26 and multiple coils 32 may be used as needed. In a multiple-coil configuration, a switching circuit (e.g., a multiplexer circuit) can be used to couple a single inverter 26 to multiple coils 32, and / or each coil 32 to an individual inverter 26. During wireless power transmission operation, transistors in one or more selected inverters 26 are driven by AC control signals from the control circuit 16. The relative phase between inverters can be dynamically adjusted (e.g., a pair of inverters 26 may produce in-phase or out-of-phase output signals).

[0052] By applying a drive signal using an inverter (one or more) 26 (for example, a transistor or other switch in circuit 22), the output circuit formed from the selected coil 32 and capacitor 70 generates an AC electromagnetic field (signal 44) which is received by the wireless power receiving circuit 46 using a wireless power receiving circuit formed from one or more coils 48 and one or more capacitors 72 in device 24.

[0053] The rectifier circuit 50 is coupled to one or more coils 48 and converts the received power from AC to DC, supplying a corresponding DC output voltage Vrect between the rectifier output terminals 76 to power load circuits within the device 24 (for example, to charge the battery 34, to power the display and / or other input / output devices 54, and / or other components).

[0054] Figure 3 is a circuit diagram showing the configuration of the inverter 26 in the power transmission circuit 22. As shown in Figure 3, the inverter 26 may be a full-bridge inverter including four switches arranged in a bridge configuration. Switches T1 and T4 control an adjustable voltage V IN It is connected in series between the control terminal that provides the voltage and ground. Switches T3 and T2 are connected in parallel with switches T1 and T4, and the adjustable voltage V IN A control terminal providing power is connected in series between the control terminal and ground. Coil 32 and capacitor 70 are connected between the first node between T1 and T4 and the second node between T2 and T3. The four switches (T1, T2, T3, and T4) may be power metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), or other desired switching components. Figure 3 shows an example where the switches T1, T2, T3, and T4 (sometimes called transistors T1, T2, T3, and T4) are power MOSFETs.

[0055] During the operation of the inverter 26, the transistors T1, T2, T3, and T4 can be switched on and off in pairs. In an example where the duty cycle is equal to 50%, one pair of transistors (for example, transistors T1 and T2) conducts (is turned on) during one half cycle of the output waveform, while the other pair is turned off. Then, during the next half cycle, the conducting transistors (T1 and T2) are switched off, and the transistors (T3 and T4) that were previously turned off are turned on. This process is repeated to generate a desired AC output waveform as the input to the wireless power transmission coil 32.

[0056] FIG. 3 shows an example of receiving the common control signals SW1 for transistors T1 and T2 and the common control signal SW2 for transistors T3 and T4. The control signals SW1 and SW2 can be alternately switched between a first state and a second state (for example, a high state and a low state) to operate the inverter 26.

[0057] There are some operating characteristics of the inverter 26 that can be adjusted during the operation of the PTX 12. These operating characteristics include the inverter voltage V IN , the operating phase θ, the duty cycle, and the frequency of the output AC current signal generated by the inverter 26.

[0058] As shown in FIG. 3, the inverter 26 can be connected to a variable DC voltage V IN . The magnitude of V IN can be adjusted to control the magnitude of the wireless power transmitted by the power transmission circuit 22. Increasing V IN increases the magnitude of the wireless power transmitted by the power transmission circuit 22, and decreasing V IN decreases the magnitude of the wireless power transmitted by the power transmission circuit 22. Instead or in addition, the magnitude of the operating phase can be used to control the magnitude of the wireless power transmitted by the power transmission circuit 22. Instead or in addition, the magnitude of the duty cycle can be used to control the magnitude of the wireless power transmitted by the power transmission circuit 22.

[0059] The example of an inverter output coupled to a wireless power transmission coil in Figure 3 is for illustrative purposes only. In general, the inverter output can be coupled to a wireless power transmission coil (similar to those in Figures 2 and 3), a transformer coil, an antenna, or any other desired component.

[0060] Several electronic devices having inverters, such as the PTX 12 in Figures 1 and 3, can employ signal dithering to improve the electromagnetic radiation characteristics of the system (e.g., to reduce conduction radiation and / or radioactive emissions). For example, the PTX 12 can dither the clock signal used to control the inverter 26. This effectively dithers the frequency of the AC signal output by the inverter 26.

[0061] In this specification, various signals (e.g., clock signals) may be referred to as having a corresponding waveform (e.g., the shape of the signal voltage over time). A given waveform may have a repeating shape that repeats at a given frequency (i.e., a given waveform may be periodic). The repeating shape does not necessarily have to be a regular shape (e.g., a sinusoidal curve). In fact, the repeating shape may deviate from a sinusoidal shape. However, this type of waveform may still have frequencies associated with periodic repetitions of a non-sinusoidal waveform.

[0062] Figure 4 shows an exemplary PTX 12 with a dithering circuit. In one possible configuration, a dithering circuit 84 and a clock modulation circuit 86 can be used to implement spread spectrum clocking technique (sometimes called clock dithering). The dithering circuit 84 and the clock modulation circuit 86 can be considered as part of the control circuit 16. In spread spectrum clocking, the clock waveform is intentionally modified so that the spectrum of the signal spreads around a target frequency of the clock signal. This target frequency is sometimes called the fundamental frequency of the clock signal. This improves the electromagnetic compatibility (EMC) associated with the target frequency of the clock signal. The dithering circuit 84 can determine a modulation waveform 88 used to modulate the clock waveform 92 (sometimes called the native clock waveform 92, initial clock waveform 92, undithered clock waveform 92, system clock 92, etc.). To improve EMC, the modulation waveform 88 is applied to the clock waveform 92 by the clock modulation circuit 86. The clock modulation circuit 86 can frequency modulate the clock waveform 92 using the modulation waveform 88. The resulting switching signal 90 (sometimes called a modified clock signal 90, a dithered clock signal 90, or a dithered switching signal 90) is then supplied to the inverter 26 to generate a frequency-dithered AC signal.

[0063] The modulated waveform 88 output by the dithering circuit 84 may be fixed or adjusted based on the real-time operating conditions of the wireless power system 8. For example, the dithering circuit 84 can generate the modulated waveform 88 based on the charge state of the battery 34 in the PRX 24, the output voltage and / or current of the rectifier 50, the output voltage and / or current of the coil 48, the voltage and / or current of the coil 32, and so on.

[0064] Figure 5 is a graph of an exemplary dithered clock signal that can be provided to the inverter 26 of a PTX 12. The dithered clock signal in Figure 5 can be used in a PTX having a specified radio power transmission frequency (sometimes called nominal radio power transmission frequency or simply radio power transmission frequency) of 360 kHz. As shown in Figure 5, the dithered clock signal may also be a step function approximating a triangular waveform. Thus, the dithered clock signal can be referred to as having a triangular shape. The dithered clock signal in Figure 5 may be repeated in multiple iteration cycles. Each iteration cycle may contain one period of the waveform shown in Figure 5. It is desirable that the triangular waveform has a smooth transition between each iteration cycle of the dithering pattern.

[0065] One iterative cycle of the dithered clock signal has a total of 32 frequency steps. Figure 5 shows the instantaneous frequency of the clock signal over time. The period of each frequency step is 1 / f. s Equal to (in the formula, f s (where is the instantaneous frequency of the clock signal). In other words, the dithered clock signal remains at the instantaneous frequency associated with each frequency step for exactly one cycle.

[0066] Each of the 32 frequency steps can have a unique frequency magnitude. The 32 unique frequency steps have a first subset of descending steps (sometimes called decreasing steps) where the frequency magnitude decreases with each subsequent step of the waveform. The 32 unique frequency steps have a second subset of ascending steps (sometimes called increasing steps) where the frequency magnitude increases with each subsequent step of the waveform. In the embodiment of Figure 5, steps 1-17 are descending steps of the waveform, and steps 18-32 are ascending steps of the waveform. The intermediate step of the ascending steps (i.e., step 24) is equal to the radio power transmission frequency of 360 kHz. The intermediate step of the descending steps (i.e., step 9) is close to the radio power transmission frequency of 360 kHz (although not exactly equal to 360 kHz, each frequency step has a unique frequency magnitude).

[0067] Each of the ascending frequency steps can be shifted relative to the corresponding frequency step of the descending frequency step. For example, the magnitude of the frequency in step 18 is slightly greater than the magnitude of the frequency in step 16, the magnitude of the frequency in step 19 is slightly greater than the magnitude of the frequency in step 15, the magnitude of the frequency in step 20 is slightly greater than the magnitude of the frequency in step 14, and so on.

[0068] The magnitude of the frequency in each ascending frequency step may be between two of the magnitudes of the frequencies in each descending frequency step. For example, the magnitude of the frequency in step 18 may be between the magnitudes of the frequencies in steps 15 and 16, the magnitude of the frequency in step 19 may be between the magnitudes of the frequencies in steps 14 and 15, the magnitude of the frequency in step 20 may be between the magnitudes of the frequencies in steps 13 and 14, and so on.

[0069] Modulation frequency (f) of the dithered clock signal m) may be equal to the reciprocal of the period of the waveform in Figure 5. Each frequency step has a duration of one period at the instantaneous frequency in that frequency step, and since the dithered clock signal is centered on a specified radio power transmission frequency, the modulation frequency of the dithered clock signal may also be equal to the radio power transmission frequency divided by the number of steps in the frequency profile. Thus, the modulation frequency of the dithered clock signal in Figure 5 is 11.25 kHz (e.g., 360 kHz / 32 = 11.25 kHz).

[0070] The dithered clock signal in Figure 5 may also have a characteristic frequency deviation Δf. The magnitude of Δf may be equal to the maximum difference between the frequency of the dithered clock signal and the radio power transmission frequency. In the waveform of Figure 5, frequency step 1 has the maximum frequency, and frequency step 17 has the minimum frequency. Frequency step 17 may have the largest deviation from the radio power transmission frequency, and therefore the magnitude of Δf is equal to 360 kHz minus the frequency at step 17. Here, the frequency at step 17 may be equal to 341.23 kHz, and therefore Δf is equal to 18.77 kHz.

[0071] The dithered clock signal in Figure 5 is Δf / f m It can have a characteristic modulation index (h) defined as follows. In the case of the waveform in Figure 5, the modulation index is equal to 1.67 (for example, 18.77kHz / 11.25kHz=1.67).

[0072] Figure 6 shows an exemplary modulated waveform that can be used to generate the dithered clock signal of Figure 5. In one embodiment, the clock modulation circuit 86 can modulate the clock waveform 92 by dividing the clock frequency by the denominator provided by the modulated waveform 88. In one embodiment, the system clock frequency may be 288 MHz. The denominator used to divide the system clock frequency is shown in Figure 6. The waveform in Figure 6 has 32 steps, each step corresponding to an individual step of the dithered clock signal of Figure 5.

[0073] In a specific embodiment, the modulated waveform in Figure 6 may have denominators of 764, 768, 772, 776, 780, 784, 788, 792, 796, 802, 810, 816, 822, 828, 836, 842, 844, 840, 834, 824, 820, 814, 808, 800, 794, 790, 786, 782, 778, 774, 770, and 766 (in this order). The resulting frequency ranges are 376.96kHz (e.g., 288MHz / 764=376.96kHz), 375.00kHz (e.g., 288MHz / 768=375.00kHz), 373.06kHz, 371.13kHz, 369.23kHz, 367.35kHz, 365.48kHz, 363.64kHz, 361.81kHz, 359.10kHz, 355.56kHz, 352.94kHz, 350.36kHz, These are equal to 347.83kHz, 344.50kHz, 342.04kHz, 341.23kHz, 342.86kHz, 345.32kHz, 349.51kHz, 351.22kHz, 353.81kHz, 356.44kHz, 360kHz, 362.72kHz, 364.56kHz, 366.41kHz, 368.29kHz, 370.18kHz, 372.09kHz, 374.03kHz, and 375.98kHz (in this order). For each pair of adjacent frequency steps, the difference in magnitude between the frequencies may be between 0.5kHz and 4.5kHz. The minimum difference in magnitude between adjacent frequency steps may be 0.81kHz. The maximum difference in magnitude between adjacent frequency steps may be 4.19kHz.

[0074] Each of the 32 unique denominator steps in Figure 6 can have a unique magnitude. The 32 unique denominator steps have a first subset of ascending steps (sometimes called increasing steps) in which the magnitude of the denominator increases with each subsequent step of the waveform. The 32 unique denominator steps have a second subset of descending steps (sometimes called decreasing steps) in which the magnitude of the denominator decreases with each subsequent step of the waveform. In the embodiment of Figure 6, steps 1 to 17 are ascending steps of the waveform, and steps 18 to 32 are descending steps of the waveform.

[0075] One or more of the descending denominator steps can be shifted by a certain amount relative to the corresponding denominator step of the ascending frequency step. In Figure 6, the magnitude of the shift is equal to 2. The size of the denominator in step 18 is 2 less than the size of the denominator in step 16, the size of the denominator in step 19 is 2 less than the size of the denominator in step 15, the size of the denominator in step 21 is 2 less than the size of the denominator in step 13, and so on.

[0076] The specific embodiments shown in Figures 5 and 6 are merely illustrative examples. Modulation frequency f m The modulation frequency f may be greater than 9kHz, greater than 10kHz, greater than 11kHz, greater than 15kHz, less than 30kHz, less than 20kHz, etc. Lower modulation frequencies may be desirable to reduce the magnitude of Δf, as this places less stress on the radio power system. Since 9kHz is the resolution bandwidth (RBW) used in some electromagnetic interference (EMI) test protocols, the modulation frequency f m It can also be desirable for the frequency to be greater than 9kHz.

[0077] The magnitude of the modulation index (h) of the dithered clock signal may be less than 2.0, less than 1.9, less than 1.8, less than 1.7, less than 1.6, greater than 1.4, greater than 1.5, greater than 1.6, 1.4 to 1.8, 1.5 to 1.7, 1.6 to 1.7, etc. The magnitude of the frequency deviation (Δf) of the dithered clock signal may be greater than 5kHz, greater than 10kHz, greater than 15kHz, greater than 20kHz, greater than 30kHz, less than 20kHz, less than 15kHz, 10kHz to 30kHz, 10kHz to 20kHz, etc. The magnitude of the frequency deviation (Δf) of the dithered clock signal may be less than 20% of the wireless power transmission frequency, less than 10%, less than 5%, less than 3%, greater than 1%, greater than 2%, greater than 5%, greater than 10%, or between 1% and 10% of the wireless power transmission frequency.

[0078] The dithered clock signal in Figure 5 can have a time-weighted average frequency that is within 1 kHz of the wireless power transmission frequency (e.g., 359 kHz to 361 kHz, 127 kHz to 129 kHz, etc.).

[0079] One objective of the frequency dithering schemes described herein is to improve EMC at a given radio power transmission frequency. Generally, a greater reduction in EMI at a given radio power transmission frequency is desirable. However, the maximum radiated peak associated with the dithered clock signal must remain at the radio power transmission frequency and not at the sideband frequencies. In other words, it is desirable that the radiated peak at the sideband frequencies associated with the radio power transmission frequency is smaller than the radiated peak at the radio power transmission frequency. By reducing the radiated peak at the radio power transmission frequency, it is possible to increase the radiated peak at the sideband frequencies. Therefore, the dithering patterns described herein can be selected to reduce the radiated peak at the radio power transmission frequency as much as possible while also ensuring that the radiated peak at the sideband frequencies is smaller than the radiated peak at the radio power transmission frequency.

[0080] Figure 7 is a graph of the radiation spectrum associated with the dithered clock signal in Figure 5. The graph shows the radiation as a function of frequency (in units of dBμA / m). The difference in radiation may have units of dB. The dashed profile 102 shows the radiation of the undithered version of the clock signal at the radio power transmission frequency. In the embodiments of Figures 5-7, profile 102 shows the radiation of the undithered clock signal at a constant frequency of 360 kHz. The magnitude of profile 102 at 360 kHz can be defined as 0 with respect to the Y-axis scale in Figure 7.

[0081] The solid line profile 104 represents the radiation of the dithered clock signal in Figure 5. As shown in Figure 7, the maximum radiation peak of profile 104 has a magnitude E1 and is located at the radio power transmission frequency (e.g., 360 kHz). The radiation peak of profile 104 at 360 kHz (e.g., E1) is 106 smaller than the radiation peak of profile 102 at 360 kHz. Thus, the difference 106 characterizes EMI reduction at the radio power transmission frequency. In the case of the dithered clock signal in Figure 5, the magnitude of the difference 106 is -4.8 dB.

[0082] Profile 104 has peaks at the sideband frequencies in addition to the radio power transmission frequency. The sideband frequencies can be separated from each other by the modulation frequency of the dithered clock signal. In the embodiment of Figure 5, the modulation frequency is equal to 11.25 kHz. Therefore, in Figure 7, each radiated peak is separated from adjacent radiated peaks by a frequency of 11.25 kHz.

[0083] The radiated peak can decrease as the deviation from the radio power transmission frequency increases. The dithering pattern in Figure 5 is chosen to ensure that the magnitude of radiation at the sideband frequency closest to the radio power transmission frequency is smaller than the magnitude of radiation at the radio power transmission frequency. Figure 7 shows how the magnitude of radiation E2 at the first sideband frequency of 348.75 kHz and the magnitude of radiation E3 at the second sideband frequency of 371.25 kHz exist. The magnitude of radiation E2 is 108 less than the radiated peak of profile 102. The magnitude of radiation E3 is 110 less than the radiated peak of profile 102. For the dithered clock signal in Figure 5, the magnitude of the difference 108 is -5.9 dB, and the magnitude of the difference 110 is -5.3 dB.

[0084] To ensure that the peak at the specified radio power transmission frequency is the maximum radiation magnitude of the dithered clock signal, the differences 108 and 110 may be greater than the difference 106. However, the differences 108 and 110 may be close to the difference 106 in order to improve the sum of the differences 106. The difference 108 may be within 2 dB of the difference 106, within 1.5 dB of the difference 106, within 1 dB of the difference 106, etc. The difference 110 may be within 2 dB of the difference 106, within 1.5 dB of the difference 106, within 1 dB of the difference 106, etc.

[0085] The dithering patterns described herein are used for a radio power transmission frequency of 360 kHz. However, it should be understood that the same concepts can be applied to dithering patterns regardless of the magnitude of the radio power transmission frequency. For example, dithering patterns at any desired radio power transmission frequency (e.g., 100-400 kHz, 128 kHz, 1-100 MHz, 1.7 MHz-1.8 MHz, less than 2 MHz, 100 kHz-2 MHz, 6.78 MHz, 13.56 MHz, etc.) may have the number of frequency steps, modulation frequency, waveform shape, frequency deviation, modulation index, and / or radiation profile characteristics described herein.

[0086] One or more operating characteristics of the PTX 12 may vary (in addition to frequency) between different frequency steps in the dithered clock signal shown in Figure 5. Different frequency steps may have different associated amplitudes, duty cycles, phases, etc. In particular, non-frequency operating characteristics may be modified to adjust the magnitude of the radio power transmission from the PTX 12 to the PRX 24. Adjusting the magnitude (power level) of the radio power transmission can mitigate ripple that would otherwise exist due to gain variations caused by frequency changes.

[0087] This concept is illustrated in Figures 8 and 9. Figure 8A is a graph of the duty cycle over time when PTX 12 operates using a constant duty cycle. As shown in Figure 8A, the duty cycle remains fixed at a given value (e.g., 0.5 or 50%) over time. However, a change in the frequency of the dithered clock signal (as shown in Figure 5) can cause a change in the output voltage at PRX 24. Figure 8B shows the rectifier output voltage (e.g., V) of PRX 24 while PTX 12 is using the frequency in Figure 5 and the duty cycle in Figure 8A. RECT This is a graph of the operation. As shown in Figure 8B, when the duty cycle (and other non-frequency operating characteristics) is constant, the output voltage correlates with the instantaneous frequency of the radio power signal transmitted by the PTX 12. Different frequencies may have different magnitudes of associated gain in the inductive link between the PTX 12 and the PRX 24. In the example of radio power transmission system 8 (Figures 1 and 2), the operating frequency is inversely proportional to the gain between the PTX 12 and the PRX 24, and therefore inversely proportional to the output voltage seen by the PRX 24 given a particular output by the PTX 12. In particular, higher frequencies have lower associated gain and output voltage, while lower frequencies have higher associated gain and output voltage.

[0088] Using the operating characteristics of Figures 5 and 8A, the rectifier output voltage has ripple (as shown in Figure 8B). Ripple is defined as the residual periodic fluctuation of the DC voltage. Hereinafter, the magnitude of the ripple may be characterized as the difference between the maximum and minimum output voltages over at least one iterative cycle of the dithered clock signal. In Figure 8B, the maximum output voltage is approximately 30V and the minimum output voltage is approximately 26V. Therefore, the magnitude of the ripple 202 is approximately 4V.

[0089] To improve the wireless charging operation between the PTX 12 and the PRX 24 (e.g., to reduce noise and vibration, improve stability and communication, etc.), the PTX 12 may mitigate ripple caused by the dithered clock signal. In particular, the PTX 12 may vary one or more non-frequency operating characteristics (e.g., amplitude, duty cycle, phase, etc.) between different frequency steps within an iterative cycle. Varying the non-frequency operating characteristics can vary the transmit power level associated with wireless power transmission from the PTX 12 to the PRX 24, and thus compensate for gain changes caused by frequency variations between different frequency steps. In particular, the non-frequency operating characteristics may be controlled to offset gain changes caused by frequency changes. In other words, the non-frequency operating characteristics have a correspondingly high transmit power level when the frequency is high (and the gain is low) and a correspondingly low transmit power level when the frequency is low (and the gain is high).

[0090] Figure 9A is a graph of the duty cycle over time when the PTX 12 operates using a variable duty cycle to mitigate ripple. As shown in Figure 9A, the duty cycle varies over time according to a pattern similar to the frequency pattern in Figure 5. For each of the 32 frequency steps in Figure 5, or for some but not all of the 32 frequency steps in Figure 5, there may be a unique duty cycle.

[0091] Figure 9B shows the rectifier output voltage of PRX 24 (e.g., V) while PTX 12 uses the frequency and duty cycle of Figure 5 and Figure 9A. RECT This is a graph of the voltage. As shown in Figure 9B, the fluctuating duty cycle in Figure 9A keeps the output voltage constant (or nearly constant). Therefore, the ripple in Figure 9B is equal to 0 (or nearly 0, such as less than 0.5V, less than 0.3V, less than 0.1V, etc.).

[0092] Figure 10 is a graph showing how the duty cycle of inverter 26 can vary at each frequency step. Figure 10 shows the switching signals used for steps 1, 2, and 3 of the dithered clock signal in Figure 10. As shown in Figure 10, step 1 has a corresponding period 204-1, step 2 has a corresponding period 204-2, and step 3 has a corresponding period 204-3. The instantaneous frequency in step 1 is 376.96 kHz, and therefore step 1 has a period 204-1 of 2.65 μs. The instantaneous frequency in step 2 is 375.00 kHz, and therefore step 2 has a period 204-2 of 2.67 μs. The instantaneous frequency in step 3 is 373.06 kHz, and therefore step 3 has a duration of 2.68 μs.

[0093] In addition to its inherent period, each frequency step may also have an inherent duty cycle. The duty cycle can be defined as the percentage of time that the control signal SW1 is high (and therefore conducts or turns on transistors T1 and T2 in Figure 3). As shown in Figure 10, during the period 204-1 between t0 and t1, SW1 is high for a duration of 206-1 (e.g., a subset of the period). SW1 is then low for the remainder of the period. Thus, the duty cycle during step 1 is equal to the duration 206-1 divided by the duration 204-1. Similarly, the duty cycle during step 2 is therefore equal to the duration 206-2 divided by the duration 204-2, and the duty cycle during step 3 is therefore equal to the duration 206-3 divided by the duration 204-3. The duty cycle for Step 1 may be 50%, the duty cycle for Step 2 (e.g., 49%) may be less than the duty cycle for Step 1, and the duty cycle for Step 3 (e.g., 48%) may be less than the duty cycle for Step 2.

[0094] Figure 10 shows an example of complementary duty cycle control where SW2 is set to be equal to the reciprocal of SW1. In other words, when SW1 is high, SW2 is low, and vice versa. This example is illustrative, and SW1 and SW2 could instead be controlled using symmetric duty cycle control (sometimes called parallel duty cycle control). In symmetric duty cycle control, SW1 and SW2 are high for the same amount of time in each period. Therefore, there can be one or more periods in which both SW1 and SW2 are low. In an example where the duty cycle is 45% and symmetric duty cycle control is used, SW1 may be high and SW2 may be low for the first 45% of the period, both SW1 and SW2 may be low for the next 5% of the period, SW2 may be high and SW1 may be low for the next 45% of the period, and both SW1 and SW2 may be low for the last 5% of the period.

[0095] A 50% duty cycle can maximize the transmit power level of a radio power transmission at a given frequency. Reducing the duty cycle can reduce the transmit power level of a radio power transmission at a given frequency. Therefore, the duty cycle is 50% at least for the frequency step having the maximum frequency of the frequency dithering pattern. The duty cycle can have at least the minimum magnitude of the frequency step having the minimum frequency of the frequency dithering pattern. Minimum duty cycles may be less than 45%, less than 40%, less than 35%, less than 30%, etc. The range of duty cycles used during the iterative cycle of a dithered clock signal may be at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, between 10% and 30%, etc. When a 32-step dithering pattern is used (as in Figure 5), the 32 frequency steps may have at least 10 intrinsic duty cycle sizes, at least 15 intrinsic duty cycle sizes, at least 20 intrinsic duty cycle sizes, at least 25 intrinsic duty cycle sizes, at least 30 intrinsic duty cycle sizes, 32 intrinsic duty cycle sizes, and so on.

[0096] An example of varying the duty cycle size between different frequency steps of the dithered clock signal to reduce ripple is merely illustrative. In another possible configuration, the control circuit 16 may vary the phase of the control signals SW1 and SW2 to reduce ripple.

[0097] The operating phase θ (sometimes called the inverter phase θ) refers to the offset between the control signals SW1 and SW2. Figure 11A shows the timing diagram for SW1 and SW2 when the inverter phase is equal to 0 degrees. Figure 11B shows the timing diagram for SW1 and SW2 when the inverter phase is equal to 180 degrees. Using the rules in Figures 11A and 11B, an operating phase of 0 degrees is defined as the state where SW2 is the reciprocal of SW1, and an operating phase of 180 degrees is defined as the state where SW2 is the same as SW1. In an operating phase of 0 degrees, when SW1 changes from high to low, SW2 changes from low to high, and when SW1 changes from low to high, SW2 changes from high to low. In other words, when the operating phase is 0 degrees, the waveforms of SW1 and SW2 are offset by half a period. With a 180-degree operating phase, when SW1 changes from low to high, SW2 changes from low to high, and when SW1 changes from high to low, SW2 changes from high to low. In other words, when the operating phase is 180 degrees, the waveforms of SW1 and SW2 are synchronized.

[0098] In the definition of the operating phase θ in Figures 11A and 11B, the effective output voltage of the inverter is maximum when the phase is equal to 0 degrees (as shown in Figure 11A) and minimum when the phase is equal to 180 degrees (as shown in Figure 11B). Therefore, adjusting the phase of the inverter 26 can adjust the magnitude of the radio power transmitted by the transmission circuit 22. Between 0 and 180 degrees, increasing the phase causes a decrease in the magnitude of the radio power transmitted by the transmission circuit, and decreasing the phase causes an increase in the magnitude of the radio power transmitted by the transmission circuit 22.

[0099] Therefore, the phase can be 0 degrees for at least the frequency step having the highest frequency of the frequency dithering pattern. The phase can have the maximum magnitude for at least the frequency step having the lowest frequency of the frequency dithering pattern. The maximum phase can be greater than 5 degrees, greater than 10 degrees, greater than 20 degrees, greater than 30 degrees, greater than 50 degrees, etc. The range of phase used during the iterative cycle of the dithered clock signal can be greater than 5 degrees, greater than 10 degrees, greater than 20 degrees, greater than 30 degrees, greater than 50 degrees, etc. If a 32-step dithering pattern is used (as in Figure 5), the 32 frequency steps can have at least 10 intrinsic phase magnitudes, at least 15 intrinsic phase magnitudes, at least 20 intrinsic phase magnitudes, at least 25 intrinsic phase magnitudes, at least 30 intrinsic phase magnitudes, 32 intrinsic phase magnitudes, etc.

[0100] Under certain operating conditions, wireless power transmission performance can be satisfactory without ripple mitigation. Therefore, the power transmission circuit 22 may be capable of operating in two modes: a mode with ripple mitigation and a mode without ripple mitigation.

[0101] Figure 12 is a state diagram of an exemplary power transmission circuit having multiple operating modes. As shown in Figure 12, the power transmission circuit may be able to operate in a first mode 212 and a second mode 214. In the first mode, no ripple mitigation is performed by the control circuit 16 and / or the power transmission circuit 22. Therefore, the phase and duty cycle can be fixed while the power transmission circuit 12 is operating in mode 212 (sometimes called non-ripple mitigation mode 212). In the second mode, ripple mitigation is performed by the control circuit 16 and / or the power transmission circuit 22. While the power transmission circuit 12 is operating in mode 214 (sometimes called ripple mitigation mode 214), the phase and / or duty cycle may vary within each iteration cycle of the dithered clock signal.

[0102] Phase and duty cycle are both sometimes referred to as the timing characteristics of the switching signals used to control the inverter 26. Phase and duty cycle are both sometimes referred to as the non-frequency operating conditions of the power transmission circuit 22.

[0103] The control circuit 16 can switch the power transmission circuit 22 to mode 212 or mode 214 based on one or more coefficients. In particular, the control circuit 16 controls the inverter power level (P INV ), estimated inductive coupling coefficient (k) between PTX 12 and PRX 24 EST Based on one or more real-time operating conditions, such as the ripple magnitude information reported from the PRX 24 to the PTX 12, an appropriate mode for the power transmission circuit 22 can be selected.

[0104] Inverter power level P INV P can refer to the power level of the AC signal generated by the inverter 26 and supplied to the transmit (TX) coil 32. At some inverter power levels, satisfactory wireless power transmission performance may be achieved without ripple mitigation operation, and therefore the transmission circuit 22 may operate in mode 212. The control circuit 16 uses P to determine the appropriate mode for the transmission circuit 22. INV A threshold may exist. INV If the value falls below the threshold, the control circuit 16 switches the power transmission circuit to mode 212 (without ripple reduction). INV If the value exceeds the threshold, the control circuit 16 switches the power transmission circuit to mode 214 (with ripple reduction). The magnitude of the threshold may be 7W, 10W, 15W, 20W, 25W, less than 15W, less than 12W, less than 10W, greater than 8W, greater than 10W, greater than 12W, greater than 15W, etc.

[0105] Inverter power level P INVThe example of comparing a threshold to determine the mode of the power transmission circuit 22 is merely illustrative. Other power levels associated with the PTX 12 (e.g., DC power output from a power adapter connected to the PTX 12, DC power output from the boot portion of a cable connected to the power adapter, etc.) may instead be compared to a threshold to determine the mode of the power transmission circuit 22, as needed.

[0106] PTX 12 can estimate the magnitude of the inductive coupling coefficient (k) between PTX 12 and PRX 24. The inductive coupling coefficient k is,

number

number

[0107] For some inductive coupling coefficients, the wireless power transmission performance can be satisfactory without ripple mitigation, and therefore the transmission circuit 22 can operate in mode 212. The control circuit 16 uses k to determine the appropriate mode for the transmission circuit 22. EST A threshold may exist. EST If the threshold is exceeded, the control circuit 16 sets the power transmission circuit to mode 212 (without ripple reduction). EST When the value falls below the threshold, the control circuit 16 switches the power transmission circuit to mode 214 (with ripple reduction). The magnitude of the threshold may be 0.7, 0.75, 0.8, 0.85, greater than 0.7, greater than 0.75, greater than 0.8, greater than 0.85, less than 0.85, less than 0.8, less than 0.75, less than 0.7, etc.

[0108] PRX 24 may report ripple magnitude information to PTX 12 using in-band and / or out-of-band communication. Ripple magnitude information may include ripple magnitudes such as magnitude 202 from Figure 8B. Generally, ripple magnitude is the output voltage V RECT It may include any desired information associated with Ripple.

[0109] One or more of the aforementioned coefficients can be used by the control circuit 16 to put the power transmission circuit 22 into mode 212 or mode 214. The control circuit 16 may put the power transmission circuit 22 into mode 212 or mode 214 at the start of power transmission operation. The control circuit 16 may optionally switch between mode 212 and mode 214 during ongoing power transmission operation.

[0110] To reduce ripple, the system gain is used to determine the duty cycle or phase magnitude for each frequency step in the dithering pattern, given a set of operating conditions (e.g., V IN , P INV The gain can be measured at each frequency step for (etc.). The measured gain can then be used to calculate the duty cycle or phase for each frequency step. For example, the duty cycle for a given frequency step is given by equation

number

[0111] Patterns of varying duty cycle magnitudes or varying phase magnitudes associated with different operating conditions can be stored in the control circuit 16. During real-time operation of the PTX 12, the PTX 12 can use a lookup table to select a duty cycle pattern or phase pattern based on the operating conditions closest to the real-time operating conditions.

[0112] Figure 13 is a flowchart illustrating an exemplary operation of the power transmission device. During the operation of block 302, the control circuit 16 can collect information. The collected information is real-time measurements associated with the power transmission circuit 22 (e.g., P INV , V IN ) may include Real-time measurements may be determined using voltage and / or current sensors in the power transmission circuit 22. The collected information may include or be based on information received from PRX 24. For example, the control circuit 16 may include PRECT and / or V RECT The control circuit 16 can receive information about the received power from the PRX 24 (sometimes called received power information or RP information), such as the following. Alternatively, or in addition, the control circuit 16 can receive ripple magnitude information and / or device type information from the PRX 24. The information received from the PRX 24 may be received using in-band and / or out-of-band communication. The control circuit 16 uses the information received from the PRX 24 to determine the inductive coupling coefficient k EST Additional parameters such as these can be estimated and / or derived.

[0113] While block 304 is operating, the control circuit 16 can select the mode of the power transmission circuit 22 based on the information collected from 304. The control circuit 16 can select either mode 212 or mode 214 from Figure 12. The control circuit 16, P INV Comparing it to a threshold, k EST The mode of the power transmission circuit 22 can be selected based on comparing the value to a threshold and / or comparing the magnitude of the ripple to a threshold. For example, the control circuit 16 is P INV When k is greater than the threshold, EST The ripple reduction mode 214 of the power transmission circuit 22 can be selected when the value is smaller than the threshold, and / or when the ripple magnitude is larger than the threshold.

[0114] As another example, the control circuit 16 may select a mode in block 304 based on the communication protocol used for communication between the PTX 12 and the PRX 24. The first communication protocol may not support communication regarding ripple magnitude and / or may have a maximum power level at which wireless power transmission operation is satisfactory without ripple mitigation. The second communication protocol may support communication regarding ripple magnitude and / or may have a maximum power level at which wireless power transmission operation is improved by ripple mitigation. In this example, the control circuit 16 may set the power transmission circuit to non-ripple mitigation mode 212 when using the first protocol and to ripple mitigation mode 214 when using the second protocol.

[0115] If control circuit 16 selects a ripple reduction mode during the operation of block 304, the control circuit can select the magnitude of the timing characteristic of the inverter switching signal during the operation of block 306. The timing characteristic may be the duty cycle or the phase, as described above. The control circuit may arbitrarily select which timing characteristic (e.g., duty cycle or phase) to vary during the operation of block 306. Based on the information collected from block 302, the control circuit may select the magnitude of the selected timing characteristic.

[0116] To select the magnitude of the chosen timing characteristic, the control circuit 16 may use a lookup table. The lookup table may contain multiple patterns for various operating conditions. Each pattern may contain multiple magnitudes of the timing characteristic. Each magnitude may be associated with a separate frequency step of the dithered clock signal.

[0117] The operating conditions associated with each stored pattern are the device type of the PRX 24, the inverter current (I INV ), V RECT or P RECT Received power information such as k EST, and / or ripple magnitude may be included. The control circuit 16 may select a pattern with associated operating conditions that best match the real-time operating conditions. Interpolation and / or extrapolation can be optionally used to accommodate the difference between the operating conditions of the selected pattern and the real-time operating conditions. Scaling The size of a given pattern may be optionally scaled based on the device type of the PRX 24.

[0118] Following the operation of block 306, the PTX 12 may transmit radio power to the PRX 24 using a frequency dithering pattern having a corresponding variable non-frequency characteristic. The magnitude of the variable non-frequency characteristic is selected during the operation of block 306. During the ongoing radio power transmission operation, while block 308 is operating, the control circuit 16 can collect additional information (similar to the operation of block 302). In other words, the control circuit 16 can continuously monitor the operating conditions associated with radio power transmission.

[0119] During the operation of block 310, the control circuit may take additional actions based on additional information from block 308. For example, control circuit 16 may switch the mode of the power transmission circuit. In a specific example, control circuit 16 may P INV In response to the increase in magnitude greater than the threshold, the system may switch from non-ripple mitigation mode 212 to ripple mitigation mode 214, or P INV Depending on the magnitude of the ripple reduction, the control circuit may switch from ripple reduction mode 214 to non-ripple reduction mode 212. As an additional example, the control circuit 16 may control k EST Depending on the magnitude of the ripple reduction, the system may switch from non-ripple reduction mode 212 to ripple reduction mode 214, or k EST In response to the increase in magnitude exceeding a threshold, the system may switch from ripple mitigation mode 214 to non-ripple mitigation mode 212.

[0120] As another example, the control circuit 16 may change the magnitude of the timing characteristics during the operation of block 310. Consider an example where a fluctuating duty cycle is used to mitigate ripple in mode 214. The control circuit 16 may store multiple duty cycle patterns. Each duty cycle pattern contains 32 duty cycle magnitudes (one for each frequency step of the repetition cycle of the dithered clock signal). The first pattern is the first inverter power level P INV1 It may also be associated with the second pattern, where the second inverter power level P INV2 It may be associated with the following. During the operation of block 306, the inverter power level is P INV1 It may be equal to , and therefore the first pattern of the fluctuating duty cycle is used. During the operation of block 310, the inverter power level is P INV2 It may be equal to , and therefore the second pattern of variable duty cycles is used.

[0121] As described above, inverter switching frequency dithering can be employed to reduce electromagnetic interference (EMI) and improve electromagnetic compatibility (EMC). In the context of wireless power transmission systems, this can cause ripple in the rectifier output voltage (Vrect). Various techniques to mitigate this ripple have also been described above, such as manipulating additional inverter control parameters in addition to frequency, and such manipulation corresponds to frequency dithering. As mentioned above, such additional parameters may include manipulation of duty cycle, phase, etc.

[0122] In some embodiments, it may be advantageous to further modify such ripple compensation techniques to account for different operating conditions, such as different radio power transmission levels and different relative positions between the PTX and PRX. As an example, duty cycle dithering may be employed in which the duty cycle can be gradually changed to reduce rectifier output voltage (Vrect) ripple by compensating for changes in radio power transmission gain associated with frequency changes (dithering). While such duty cycle changes can significantly reduce ripple, the "optimal" duty cycle depends on both the load (i.e., the amount of energy supplied by the radio power transmission system) and the relative position or magnetic alignment between the PTX and PRX. Therefore, it may be desirable to change the duty cycle to compensate for ripple, partly in response to the load and / or relative position or magnetic alignment, and in response to frequency dithering. There are at least two methods to achieve the desired duty cycle compensation. The first technique can be based on gain calculations performed by the cooperation between the PTX and PRX devices. The second technique can be performed by the PTX alone based on the measurement of its own input voltage. These techniques are described in more detail below.

[0123] Figure 14 shows a simplified equivalent circuit model 1400 of a wireless power transmission system. The model includes an AC voltage source 1402, a complex impedance 1404 representing the wireless power transmission system, and a load impedance 1406 corresponding to the load supplied by the PRX. The rectifier output voltage Vrect appears across the load impedance 1406. The parameters K and Zo shown in the equivalent circuit model 1400 can be used to determine the duty cycle for mitigating the rectifier voltage ripple associated with frequency dithering, as will be described in more detail below. These parameters can also be considered to characterize the load line of the wireless power transmission system.

[0124] Figure 15 is a simplified flowchart 1500 of a first duty compensation technique based on gain calculation performed by cooperation between a PTX device and a PRX device. The left side of Figure 15 shows actions that may be performed by the PTX device, for example, by a control circuit 16. The right side of Figure 15 shows actions that may be performed by the PRX device, for example, by a control circuit 38. For convenience, such actions are described as being performed by individual PTX or PRX devices, but it is understood that such actions may actually be performed by specific components or systems of such devices. Starting from block 1501, the PTX can detect ripple associated with the frequency dithering described above. This can be based on its own measurements, such as inverter output and / or voltage, inverter input current and / or voltage, or other appropriate circuit parameter measurements. In some embodiments, the PRX device can detect such ripple (block 1502) and notify the PTX using an available in-band or out-of-band communication channel (block 1503). The PRX device can detect such ripple by measuring the rectifier input current and / or voltage, the rectifier output current and / or voltage, or other appropriate circuit parameters.

[0125] In either case, once the PTX detects a ripple condition (block 1501), the system, including the PTX and PRX, can enter the startup calibration phase 1600, which is described in more detail below with respect to Figure 16. Once the startup calibration phase 1600 is complete, the PTX can participate in the runtime duty cycle calculation, which is described in more detail below with respect to Figure 17 (block 1700).

[0126] Figure 16 is a simplified flowchart 1600 of the startup calibration stage of the first duty cycle compensation technology. Similar to Figure 15, the left side of Figure 16 shows actions that may be performed by the PTX device, for example, by the control circuit 16. Similarly, the right side of Figure 16 shows actions that may be performed by the PRX device, for example, by the control circuit 38. For convenience, such actions are described as being performed by individual PTX or PRX devices, but it is understood that such actions may actually be performed by specific components or systems of such devices. Furthermore, the operations described in Figure 16 are performed in four groups labeled (a) to (d), which include measurements, communications, and / or calculations performed by the PTX and PRX devices, respectively. Blocks corresponding to these operations are provided with reference numbers within group (a), but such reference numbers are omitted from groups (b) to (d) for brevity. Nevertheless, it should be understood that each reference number in Figure 16 applies to all operations of a given type, even if the number is omitted from one or more instances.

[0127] The startup calibration operation in Figure 16 can be triggered as part of the power ramp-up phase. For example, the operation may be triggered in response to a power level below a threshold. One such threshold may be 15W, but other values ​​such as 5W, 7.5W, or 10W can also be selected. The estimated coupling coefficient kest may also be part of such a trigger. For example, startup calibration may be triggered when kest < 0.83, or other appropriate values ​​such as 0.80, 0.81, 0.82, 0.84, or 0.85.

[0128] The startup calibration operation in Figure 16 can incorporate multiple gain measurements, in which the PTX works with the PRX to measure the gain of the wireless power transmission path. These gain measurements can be performed at multiple operating frequencies and duty cycles to enable characterization of the wireless power transmission path. Thus, in block 1601 of group (a), the PTX can set the initial wireless power transmission frequency F1 and the initial duty cycle D1-1. The PTX can then (in block 1602) initiate a Gain Measurement Mode (GMM), which may involve communication with the PRX, the reception of which is shown in block 1603. In some embodiments, initiating the Gain Measurement Mode may be performed using communication in accordance with one or more versions of the Qi wireless power transmission protocol published by the Wireless Power Consortium. These communications may involve the exchange of messages between the PTX and the PRX, which are omitted here for brevity.

[0129] When gain measurement mode is initiated, the PRX can measure the rectifier voltage (Vr) and rectifier current (Ir) at the first and second load levels, respectively. For example, the PRX can measure Vr1 and Ir1 at the first load level, then switch to an additional load and measure Vr2 and Ir2 at the second load level (block 1604). In block 1605, the PRX can transmit (report) these values ​​to the PTx. This transmission may follow one or more versions of the Qi protocol and may include the exchange of one or more messages, but these are omitted here for brevity.

[0130] When the PTX receives the measured voltage value Vr1 and current values ​​Ir1, Vr2, and Ir2, the PTX can communicate the parameters K and Zo shown in the equivalent circuit model 1400 in Figure 14. More specifically, the parameter Zo can be calculated according to the following formula.

number

[0131] If Zo is known, the parameter K can be calculated according to the following formula.

number

[0132] These operations can be repeated in the sequence of gain measurements (b) to (d) shown in Figure 16, where gain measurement (b) is with a first frequency F1 and a second duty cycle D1-2, gain measurement (c) is with a second frequency F2 and a third duty cycle D2-1, and gain measurement (d) is with a second frequency F2 and a fourth duty cycle D2-2. These measurements can therefore generate the corresponding parameters Zo1-2, K1-2, Zo2-1, K2-1, Zo2-2, and K2-2 along the lines described above. These calibration values ​​can be used in the runtime duty cycle calculation 1700, which is introduced above with respect to Figure 15 and described in more detail below with reference to Figure 17.

[0133] The frequency values ​​F1 and F2, and the duty cycle values ​​at each of these frequencies, may be selected by the PTX to provide adequate coverage of the expected range of operating conditions. For example, the first and second frequencies may be selected to correspond to the range of frequencies caused by the dithering operation described above. As an example, for a nominal operating frequency of 360 kHz, F1 may be 380 kHz and F2 may be 340 kHz. These values ​​may, but do not have to be, the minimum and maximum values ​​provided by the dithering operation. Similarly, various duty cycles may be selected to correspond to the range of duty cycles that are expected to provide a certain gain (reduction of ripple) based on the dithered operating frequency. For example, at the first frequency F1 (e.g., 380 kHz), a first duty cycle D1-1 of 0.46 and a second duty cycle of 0.5 may be selected. Similarly, at the second frequency F2 (e.g., 340 kHz), a third duty cycle D2-1 of 0.35 and a second duty cycle of 0.4 may be selected. In general, selecting a range between frequencies F1 and F2 that covers a significant portion of the expected dithering range may provide better compensation. Furthermore, regarding the duty cycle, it should be understood that the duty cycle is always less than 0.5, and as the frequency decreases, it may be necessary to reduce the duty cycle to keep the radio power transmission channel gain (and therefore the power level) relatively constant. Thus, each of the above frequency and duty cycle values ​​is merely illustrative, and any appropriate value can be selected for a given implementation.

[0134] Figure 17 is a simplified flowchart 1700 of the runtime duty cycle calculation stage of the first duty cycle compensation technique. Similar to Figures 15 and 16, the left side of Figure 17 shows actions that may be performed by the PTX device, for example, by the control circuit 16. Similarly, the right side of Figure 17 shows actions that may be performed by the PRX device, for example, by the control circuit 38. For convenience, such actions are described as being performed by individual PTX or PRX devices, but it is understood that such actions may actually be performed by specific components or systems of such devices. During wireless power transmission, the PRX periodically reports its rectifier power level (Prect), i.e., the amount of energy supplied to the load on the PRX, and its rectifier output voltage (Vrect) to the PTX (block 1701). In some embodiments, this reporting or communication may be performed in accordance with one or more versions of the Qi standard referenced above. In some embodiments, such reporting may involve the use of MPLA packets transmitted at specified time intervals. The time interval may be 1.3 seconds or other time periods.

[0135] Upon receiving the reported Prect and Vrect values, the PTX can compare the Prect value to a threshold, for example, to determine whether the transmit power level exceeds the threshold (block 1702). The threshold may be 15W, or other appropriate values ​​such as 5W, 7.5W, 10W, 12.5W, 20W, or 25W. If the reported Prect value exceeds the threshold, the PTX can calculate the gains G1 and G2 according to the following formulas (block 1703).

number

number

[0136] After calculating the gain, PTX can calculate the duty cycles D1 and D2 by solving the following system of equations (block 1704). dD = D1 - D2 V rect =G1sin(πD1)=G2sin(πD2) Here, dD is the duty cycle span, G1 and G2 are the gains calculated above, and Vrect is the rectifier voltage reported by the PRX. The solution to these equations is as follows:

number

number

[0137] In the above calculations, the gain calculations used the values ​​Zo1 as Zo1-1, K1 as K1-1, Zo2 as Zo2-1, and K2 as K2-1. In some embodiments, these parameters may vary depending on the current or determined duty cycle. As an example, the above values ​​may be used when D2 is greater than or equal to a certain threshold, e.g., 0.42. If D2 is less than the threshold, other values, namely Zo1 as Zo1-2, K1 as K1-2, Zo2 as Zo2-2, and K2 as K2-2, can be used instead, as they were calculated using lower (and therefore closer duty cycles) values ​​in the calibration step described above, with reference to Figure 16. Furthermore, it may be desirable for the PTX to set boundaries for duty cycle values; for example, D2 may be constrained to a range of 0.35 to 0.445 (or other appropriate value), and the maximum duty cycle may be constrained to be greater than D2 and always less than 0.5.

[0138] Figure 18 is a simplified flowchart 1800 of a second duty cycle compensation technique performed solely by the PTX without additional data from the PRX or other cooperation. For convenience, such actions are described as being performed by the PTX, but it is understood that such actions may actually be performed by certain components or systems of such devices. This compensation technique is based on a PTX that monitors the inverter input voltage (Vinv) ripple caused by a corresponding ripple on the PRX. Thus, in block 1801, the PTX can measure the Vinv ripple and yield a value of Vinvpp[n], where n is the number of measurements. Then, in block 1802, the PTX can compare the measured ripple Vinvpp[n] with a threshold (e.g., 100mV) and a previously measured value Vinvpp[n-1], and can also perform a comparison of the current duty cycle (D[n]) with a previous duty cycle (D[n-1]), depending on the following conditions: ● Ripple is greater than the threshold (i.e., Vinvpp[n]>Th), ● The ripple value is decreasing over time (i.e., Vinvpp[n] <Vinvpp[n-1])、かつ、 ● The duty cycle increases over time (i.e., dD > 0, where dD = D[n] - D[n-1]), Next, in block 1803, the PTX can increment the duty cycle by a small value (e.g., 0.1, i.e., D[n+1]=D[n]+0.1) to set a maximum duty cycle value, e.g., 0.445. This can be described as left-hand operation with reference to the curve in Figure 19, which is described below. The PTX can then return to block 1801 to perform another ripple measurement.

[0139] Instead, if one or more of the above conditions in block 1802 are not met, then in block 1804, the PTX is: ● Whether the ripple is greater than the threshold (i.e., Vinvpp[n]>Th), ● Whether the ripple value is increasing over time (i.e., Vinvpp[n]>Vinvpp[n-1]), and, ●It is possible to determine whether the duty cycle increases over time (i.e., dD>0, where dD=D[n]-D[n-1]). Depending on whether these conditions are met, the PTX may decrement the duty cycle in block 1805 by a small value (e.g., 0.1, i.e., D[n+1]=D[n]-0.1) to set a minimum duty cycle value, e.g., 0.35. This can be described as a rightward shift operation, referring to the curve in Figure 19, which is described below. The PTX can then return to block 1801 to perform another ripple measurement.

[0140] Instead, if one or more of the above conditions in block 1804 are not met, then in block 1807, the PTX is: ● Whether the ripple is greater than the threshold (i.e., Vinvpp[n]>Th), ● The ripple value is decreasing over time (i.e., Vinvpp[n] <Vinvpp[n-1])かどうか、かつ、 ●It is possible to determine whether the duty cycle decreases over time (i.e., dD < 0, where dD = D[n] - D[n-1]). Depending on whether these conditions are met, the PTX may, in block 1806, decrement the duty cycle by a small value (e.g., 0.1, i.e., D[n+1]=D[n]-0.1) to set a minimum duty cycle value, e.g., 0.35. This can be illustrated by referring to the curve in Figure 19, which is described below. The PTX can then return to block 1801 to perform another ripple measurement.

[0141] Instead, if one or more of the above conditions in block 1806 are not met, then in block 1808, the PTX is: ● Whether the ripple is greater than the threshold (i.e., Vinvpp[n]>Th), ● Whether the ripple value is increasing over time (i.e., Vinvpp[n]>Vinvpp[n-1]), and, ●It is possible to determine whether the duty cycle decreases over time (i.e., dD < 0, where dD = D[n] - D[n-1]). Depending on whether these conditions are met, the PTX may increment the duty cycle in block 1809 by a small value (e.g., 0.1, i.e., D[n+1]=D[n]+0.1) to set a maximum duty cycle value, e.g., 0.445. This can be described as a leftward shift operation with reference to the curve in Figure 19, which is described below. The PTX can then return to block 1801 to perform another ripple measurement.

[0142] Finally, if none of the conditions in blocks 1802, 1804, 1806, or 1808 are met (for example, because the ripple is below the threshold, the ripple is neither increasing nor decreasing, and / or the duty cycle has not changed), the PTX can simply return to block 1801, perform another ripple measurement, and repeat the process described above without changing the duty cycle, as in blocks 1803, 1805, 1807, or 1809.

[0143] Figure 19 is a plot 1900 showing ripple voltage versus duty cycle when using the second duty cycle compensation technique. Curve 1901 corresponds to a first power level P1 (e.g., 50W), and curve 1902 makes the second power level P2 (e.g., 25W) smaller than the first power level P1. For both curves, starting from the left, the ripple voltage decreases with increasing duty cycle until it reaches a certain minimum value. The minimum ripple value and / or associated duty cycle may differ for different power levels. Nevertheless, for a given power level (and the relative positions of PTX and PRX), there exists an optimal duty cycle value at which the ripple is minimized. For any given power level lower than this optimal duty cycle, increasing the duty cycle reduces the ripple voltage. This is the left-hand operation described above. Conversely, for any given power level, above the optimal duty cycle, increasing the duty cycle increases the ripple voltage, and decreasing the duty cycle decreases the ripple voltage. This is the right-side action described above.

[0144] Therefore, when the PTX measures ripple and increments or decrements the duty cycle, as described above, the PTX makes a decision on whether to increment or decrement based in part on whether the previous increment or decrement achieved the desired result. If not, the control logic must transition to the other side of the curve to achieve the desired result. Furthermore, by having a Vinv ripple threshold (e.g., 100mV) below which the duty cycle is not changed, there may be a "dead zone" at an acceptablely small ripple voltage value below which no change to the duty cycle is made. Moreover, the control technique described above can be started with an appropriate initial duty cycle value, e.g., 0.5.

[0145] This second technique for duty cycle compensation relies on measuring the inverter input voltage Vinv. In some embodiments, noise associated with these measurements may be present, linked to sources other than perturbations caused by frequency dithering. Thus, the measured ripple voltage may be obscured by such noise. However, since the frequency of the ripple associated with frequency dithering is known, the measured voltage (e.g., block 1801) can be filtered in either the analog domain before sampling and / or the digital domain after sampling to isolate the ripple value from other noise sources. One digital domain filtering technique that may be advantageous in certain applications is the Goertzel algorithm, as it can provide relatively simple calculations that can be made easier within the scope of the PTX control circuit 16. However, depending on the available computational resources and the desired level of performance, any of the various filtering techniques can also be used.

[0146] For example, reducing the ripple of the rectifier voltage Vrect can have various advantages. One such advantage may be a reduction in audible noise. In some embodiments, the Vrect ripple can be correlated with audible noise, for example, when a ceramic capacitor is used in a DC link. Depending on the switching frequency (e.g., 360 kHz) and the number of dithering steps (e.g., 32 steps), a frequency within the audible range (e.g., 360 kHz / 32 = 11.25 kHz) can be generated. This advantage, as well as other advantages such as improved EMI and EMC, can also be obtained from reducing the ripple associated with frequency dithering, as described herein.

[0147] The above is merely an example, and various modifications may be made to the described embodiments. The embodiments described above may be implemented individually or in any combination.

Claims

1. An electronic device configured to transmit wireless power to an additional electronic device, wherein the electronic device is Wireless power transmission coil and An inverter configured to receive a switching signal based on a dithered clock signal and output a corresponding AC signal to the wireless power transmission coil, The system comprises a control circuit that generates the dithered clock signal, The dithered clock signal has multiple frequency steps, An electronic device wherein the timing characteristics of one or more of the switching signals differ between at least two different frequency steps to compensate for different wireless power transmission gains in the at least two different frequency steps.

2. The electronic device according to claim 1, wherein the inverter comprises four transistors controlled by two switching signals.

3. The electronic device according to claim 1, wherein the timing characteristics include the operating phase of the inverter.

4. The electronic device according to claim 1, wherein the timing characteristics include the duty cycle of the switching signal.

5. The electronic device according to claim 4, wherein the control circuit is configured to select one or more timing characteristics of at least two different frequency steps based on real-time operating conditions determined by communicating with the additional electronic device.

6. The electronic device according to claim 5, wherein the real-time operating conditions include received power information of the additional electronic device.

7. The electronic device according to claim 6, wherein the control circuit is configured to receive the received power information from the additional electronic device using the wireless power transmission coil.

8. The electronic device according to claim 6, wherein the received power information includes calibration measurements of the rectifier voltage and rectifier current of the additional electronic device at a plurality of operating frequencies, duty cycles, and power levels.

9. The electronic device according to claim 8, wherein the control circuit calculates one or more gain values ​​based at least in part on the calibration measurement values.

10. The electronic device according to claim 6, wherein the received power information includes runtime measurements of the rectifier power and rectifier voltage of the additional electronic device.

11. The electronic device according to claim 10, wherein the control circuit calculates one or more timing characteristic values ​​based at least in part on the runtime measurement values.

12. The electronic device according to claim 6, wherein the real-time operating conditions include ripple messages reported by the additional electronic device.

13. The electronic device according to claim 12, wherein the control circuit is configured to receive the magnitude of the ripple from the additional electronic device using the wireless power transmission coil.

14. The electronic device according to claim 4, wherein the control circuit selects one or more timing characteristics of the at least two different frequency steps based on real-time operating conditions determined without communication with the additional electronic device.

15. The electronic device according to claim 14, wherein the real-time operating conditions include inverter input voltage ripple measured by the control circuit.

16. The one or more timing characteristics include a duty cycle, and the control circuit is A comparison of the inverter input voltage ripple measured by the control circuit with a threshold, Determination of whether the ripple voltage is increasing or decreasing over time, The electronic device according to claim 15, comprising determining whether the duty cycle is increasing or decreasing over time, and incrementing or decrementing the duty cycle accordingly.

17. The electronic device according to claim 1, wherein the dithered clock signal has the plurality of frequency steps in an iterative cycle, the iterative cycle of the dithered clock signal comprises a step function that approximates the waveform, and the dithered clock signal has a unique frequency magnitude for each of the plurality of frequency steps during the iterative cycle.

18. The electronic device according to claim 17, wherein the waveform includes a triangular waveform.

19. The electronic device according to claim 17, wherein the plurality of frequency steps in the iterative cycle include 32 frequency steps in the iterative cycle.

20. It is an electronic device, Wireless power transmission coil and An inverter configured to receive a switching signal based on a dithered clock signal and output a corresponding AC signal to the wireless power transmission coil, The system comprises a control circuit configured to generate the dithered clock signal, The dithered clock signal has a plurality of frequency steps, each having a specific frequency magnitude. An electronic device wherein the dithered clock signal has timing characteristics specific to at least two frequency steps selected to compensate for different radio power transmission gains in at least two different frequency steps among the plurality of frequency steps.

21. The electronic device according to claim 20, wherein the timing characteristics include the operating phase of the inverter.

22. The electronic device according to claim 20, wherein the timing characteristics include a duty cycle.

23. The electronic device according to claim 20, wherein the control circuit selects the unique timing characteristics of the at least two different frequency steps based on real-time operating conditions determined in communication with an additional electronic device.

24. The electronic device according to claim 20, wherein the control circuit selects the intrinsic timing characteristics of the at least two different frequency steps based on real-time operating conditions determined without communication with additional electronic devices.

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