Patent Application
20190312459
This relates generally to power systems, and, more particularly, to wireless power systems for charging electronic devices.
In a wireless charging system, a wireless power transmitting device wirelessly transmits power to a wireless power receiving device that is placed on the wireless power transmitting device. The receiving device has a coil and rectifier circuitry. The coil receives alternating-current wireless power signals from a coil in the transmitting device that is overlapped by the coil in the receiving device. The rectifier circuitry converts the received signals into direct-current power.
A wireless power system has a wireless power transmitting device that uses an inverter to supply alternating-current signals to a coil and thereby transmit wireless power signals to a wireless power receiving circuit of a wireless power receiving device.
The system operates in an active wireless power transfer mode in which power is transmitted wirelessly between the transmitting device and the receiving device. The system also operates in a wireless-power-transfer-halted mode in which the transmitting device does not transmit power.
During the active wireless power transfer mode, while wireless power is being transferred to the receiving device, the receiving device communicates with the wireless power transmitting device using in-band communications. When the wireless power receiving device no longer desires to receive wireless power, the wireless power receiving device sends an in-band halt-wireless-power-transfer command. This command directs the wireless power transmitting device to stop transmitting wireless power and places the system in the wireless-power-transfer-halted mode.
In the wireless-power-transfer-halted mode, when power is not being transferred, the wireless power transmitting device transmits a series of short impulses that are monitored by the receiving device. This informs the receiving device that the transmitting device is present. Analysis of an associated impulse response at the transmitting device provides the transmitting device with information on the impedance of the coil of the transmitting device. When power is desired, the receiving device directs the transmitting device to resume power transmission by adjusting an adjustable impedance circuit coupled to the wireless power receiving circuit. The adjustable impedance circuit produces a mode-switching impedance change in the wireless power receiving circuit of the receiver and in the coil of the transmitting device. The transmitting device detects the impedance change and halts power transmission.
A wireless power system includes a wireless power transmitting device. The wireless power transmitting device wirelessly transmits power to one or more wireless power receiving devices. The wireless power receiving devices may include electronic devices such as wristwatches, cellular telephones, tablet computers, laptop computers, ear buds, battery cases for ear buds and other devices, tablet computer styluses (pencils) and other input-output devices, wearable devices, or other electronic equipment. The wireless power transmitting device may be an electronic device such as a wireless charging mat, a tablet computer or other portable electronic device with wireless power transmitting circuitry, or other wireless power transmitting device. The wireless power receiving devices use power from the wireless power transmitting device for powering internal components and for charging an internal battery. Because transmitted wireless power is often used for charging internal batteries, wireless power transmission operations are sometimes referred to as wireless charging operations.
An illustrative wireless power system (wireless charging system) is shown in
Control circuitry in system 8 may be configured to perform operations in system 8 using hardware (e.g., dedicated hardware or circuitry), firmware and/or software. Software code for performing operations in system 8 is stored on non-transitory computer readable storage media (e.g., tangible computer readable storage media) in control circuitry 8. The software code may sometimes be referred to as software, data, program instructions, instructions, or code. The non-transitory computer readable storage media 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, or the like. Software stored on the non-transitory computer readable storage media may be executed on the processing circuitry of control circuitry 16 and/or 30. The processing circuitry may include application-specific integrated circuits with processing circuitry, one or more microprocessors, a central processing unit (CPU) or other processing circuitry.
Power transmitting device 12 may be a stand-alone power adapter (e.g., a wireless charging mat that includes power adapter circuitry), may be a wireless charging mat that is coupled to a power adapter or other equipment by a cable, may be a portable electronic device (cellular telephone, tablet computer, laptop computer, etc.), may be equipment that has been incorporated into furniture, a vehicle, or other system, or may be other wireless power transfer equipment. Illustrative configurations in which wireless power transmitting device 12 is a wireless charging mat or portable electronic device are sometimes described herein as an example.
Power receiving device 24 may be a portable electronic device such as a wristwatch, a cellular telephone, a laptop computer, a tablet computer, an accessory such as an earbud, a tablet computer input device such as a wireless tablet computer stylus (pencil), a battery case, or other electronic equipment. Power transmitting device 12 may be coupled to a wall outlet (e.g., an alternating current power source), may have a battery for supplying power, and/or may have another source of power. Power transmitting device 12 may have an alternating-current (AC) to direct-current (DC) power converter such as AC-DC power converter 14 for converting AC power from a wall outlet or other power source into DC power. In some configurations, AC-DC power converter 14 may be provided in an enclosure (e.g., a power brick enclosure) that is separate from the enclosure of device 12 (e.g., a wireless charging mat enclosure or portable electronic device enclosure) and a cable may be used to couple DC power from the power converter to device 12. DC power may be used to power control circuitry 16. During operation, a controller in control circuitry 16 may use power transmitting circuitry 52 to transmit wireless power to power receiving circuitry 54 of device 24. Power transmitting circuitry 52 may have switching circuitry (e.g., inverter circuitry 60 formed from transistors) that is turned on and off based on control signals provided by control circuitry 16 to create AC current signals through one or more transmit coils 42. Coils 42 may be arranged in a planar coil array (e.g., in configurations in which device 12 is a wireless charging mat) or may be arranged in other configurations. In some arrangements, device 12 may have only a single coil. In arrangements in which device 12 has multiple coils, the coils may be arranged in multiple layers (e.g., three layers or any other suitable number of layers) and each of the multiple layers may have coils that overlap coils in other layers.
As the AC currents pass through one or more coils 42, alternating-current electromagnetic (e.g., magnetic) fields (signals 44) are produced that are received by one or more corresponding receiver coils such as coil 48 in power receiving device 24. When the alternating-current electromagnetic fields are received by coil 48, corresponding alternating-current currents are induced in coil 48. Rectifier circuitry such as rectifier 50, which contains rectifying components such as synchronous rectification metal-oxide-semiconductor transistors arranged in a bridge network, converts received AC signals (received alternating-current signals associated with electromagnetic signals 44) from coil 48 into DC voltage signals for powering device 24.
The DC voltages produced by rectifier 50 can be used in powering an energy storage device such as battery 58 and can be used in powering other components in device 24. For example, device 24 may include input-output devices 56 such as a display, touch sensor, communications circuits, audio components, sensors, components that produce electromagnetic signals that are sensed by a touch sensor in tablet computer or other device with a touch sensor (e.g., to provide stylus (pencil) input, etc.), and other components and these components may be powered by the DC voltages produced by rectifier 50 (and/or DC voltages produced by battery 58 or other energy storage device in device 24).
Device 12 and/or device 24 may communicate wirelessly (e.g., using in-band and out-of-band communications). Device 12 may, for example, have wireless transceiver circuitry 40 that wirelessly transmits out-of-band signals to device 24 using an antenna. Wireless transceiver circuitry 40 may be used to wirelessly receive out-of-band signals from device 24 using the antenna. Device 24 may have wireless transceiver circuitry 46 that transmits out-of-band signals to device 12. Receiver circuitry in wireless transceiver 46 may use an antenna to receive out-of-band signals from device 12.
Wireless transceiver circuitry 40 can use one or more coils 42 to transmit in-band signals to wireless transceiver circuitry 46 that are received by wireless transceiver circuitry 46 using coil 48. Any suitable modulation scheme may be used to support in-band communications between device 12 and device 24. With one illustrative configuration, frequency-shift keying (FSK) is used to convey in-band data from device 12 to device 24 and amplitude-shift keying (ASK) is used to convey in-band data from device 24 to device 12. Power may be conveyed wirelessly from device 12 to device 24 during these FSK and ASK transmissions. Other types of communications (e.g., other types of in-band communications) may be used, if desired.
During wireless power transmission operations, circuitry 52 supplies AC drive signals to one or more coils 42 at a given power transmission frequency. The power transmission frequency may be, for example, a predetermined frequency of about 125 kHz, at least 80 kHz, at least 100 kHz, less than 500 kHz, less than 300 kHz, or other suitable wireless power frequency. In some configurations, the power transmission frequency may be negotiated in communications between devices 12 and 24. In other configurations, the power transmission frequency may be fixed.
During wireless power transfer operations, while power transmitting circuitry 52 is driving AC signals into one or more of coils 42 to produce signals 44 at the power transmission frequency, wireless transceiver circuitry 40 uses FSK modulation to modulate the power transmission frequency of the driving AC signals and thereby modulate the frequency of signals 44. In device 24, coil 48 is used to receive signals 44. Power receiving circuitry 54 uses the received signals on coil 48 and rectifier 50 to produce DC power. At the same time, wireless transceiver circuitry 46 uses FSK demodulation to extract the transmitted in-band data from signals 44. This approach allows FSK data (e.g., FSK data packets) to be transmitted in-band from device 12 to device 24 with coils 42 and 48 while power is simultaneously being wirelessly conveyed from device 12 to device 24 using coils 42 and 48. Other types of in-band communications between device 12 and device 24 may be used, if desired.
In-band communications between device 24 and device 12 uses ASK modulation and demodulation techniques or other suitable in-band communications techniques. Wireless transceiver circuitry 46 transmits in-band data to device 12 by using a switch (e.g., one or more transistors in transceiver 46 that are coupled coil 48) to modulate the impedance of power receiving circuitry 54 (e.g., coil 48). This, in turn, modulates the amplitude of signal 44 and the amplitude of the AC signal passing through coil(s) 42. Wireless transceiver circuitry 40 monitors the amplitude of the AC signal passing through coil(s) 42 and, using ASK demodulation, extracts the transmitted in-band data from these signals that was transmitted by wireless transceiver circuitry 46. The use of ASK communications allows a stream of ASK data bits (e.g., a series of ASK data packets) to be transmitted in-band from device 24 to device 12 with coils 48 and 42 while power is simultaneously being wirelessly conveyed from device 12 to device 24 using coils 42 and 48.
Control circuitry 16 has external object measurement circuitry 41 (sometimes referred to as foreign object detection circuitry or external object detection circuitry) that detects external objects on a charging surface associated with device 12. Circuitry 41 can detect foreign objects such as coils, paper clips, and other metallic objects and can detect the presence of wireless power receiving devices 24. During object detection and characterization operations, external object measurement circuitry 41 can be used to make measurements on coils 42 to determine whether any devices 24 are present on device 12 (e.g., whether devices 24 are suspected to be present on device 12). In capturing data from an array of coils 42, a pattern is formed, which is sometimes referred to as an impedance image or inductance image. The image may be processed by system 8 to determine which power transmission settings to use for transmitting power, etc.
In an illustrative arrangement, measurement circuitry 41 of control circuitry 16 contains signal generator circuitry (e.g., oscillator circuitry for generating AC probe signals at one or more probe frequencies, a pulse generator, etc.) and signal detection circuitry (e.g., filters, analog-to-digital converters, impulse response measurement circuits, etc.). During measurement operations, switching circuitry in device 12 may be adjusted by control circuitry 16 to switch each of coils 42 into use. As each coil 42 is selectively switched into use, control circuitry 16 uses the signal generator circuitry of signal measurement circuitry 41 to apply a probe signal to that coil while using the signal detection circuitry of signal measurement circuitry 41 to measure a corresponding response. Measurement circuitry 43 in control circuitry 30 and/or in control circuitry 16 may also be used in making current and voltage measurements, may be used in detecting impulses and other attributes in transmitted signals 44, may measure impulse responses, and/or may be used in making other measurements on wireless power receiving circuitry 54.
The characteristics of each coil 42 depend on whether any foreign objects overlap that coil (e.g., coins, wireless power receiving devices, etc.) and also depend on whether a wireless power receiving device with a coil such as coil 48 of
In some situations (e.g., in an arrangement in which system 8 is operating in a low power, power-transfer-halted mode in which power is not being transferred to device 24), pulses such as pulse 70 may be generated by device 12 to measure the impedance of coil 42 (and thereby the impedance of the overlapping coil 48 of receiving device 24, which affects the impedance of coil 48 measured in device 12). Device 24 can send extremely low power in-band communications (sometimes referred to as direct-current or DC communications) to device 12 by detuning the power receiving circuit (e.g., by selectively coupling or decoupling a capacitor or other detuning circuit element into or out of the power receiving circuit). These selective DC detuning operations alter the impedance of wireless power receiving circuitry 54 in device 24 and alter impedance of the wireless power transmitting circuitry 52 of device 12, which can be detected by measurement circuitry 41.
Control circuitry 30 may have measurement circuitry 43. Measurement circuitry 43 of control circuitry 30 may contain signal generator circuitry and signal detection circuitry (e.g., filters, analog-to-digital converters, impulse response measurement circuits, etc.). During measurement operations, device 24 may use measurement circuitry 43 to make measurements to characterize device 24 and the components of device 24. For example, device 24 may use measurement circuitry 43 to measure the inductance of coil 48 (e.g., signal measurement circuitry 43 may be configured to measure signals at coil 48 while supplying coil 48 with signals at one or more frequencies to measure coil inductances, signal pulses (e.g., so that impulse response measurement circuitry in the measurement circuitry can be used to make inductance and Q factor measurements), etc. Measurement circuitry 43 may also make measurements of the output voltage of rectifier 50, the output current of rectifier 50, etc. In arrangements in which device 12 generates impulses to measure the impedance of coil 42, measurement circuitry 43 may include impulse (pulse) detection circuitry. The output of this circuitry in device 24 informs device 24 when device 12 is present (coupled to device 24) and is actively sending impulses.
During in-band communications, transceiver 46 may modulate the impedance of the wireless power receiving circuit (e.g., coil 48 and capacitor 78) by selectively connecting and disconnecting a capacitor or other circuit element to and from node N or other portion of the wireless power receiving circuit at a desired data rate. This type of arrangement is used to support in-band communications (e.g., ASK communications) with device 12 while device 12 is transferring wireless power signals 44 to device 24.
It is sometimes desirable to halt power transmission from device 12 to device 10. For example, if the temperature of device 24 (e.g., battery 58) exceeds a predetermined thermal limit, it may be desirable to temporarily stop transmission of power from device 12 to device 24. System 8 may then operate in a wireless-power-transfer-halted mode in which inverter 60 does not produce pulse width modulation (PWM) power output pulses and signals 44 therefore do not convey power to device 24 to charge battery 58. By stopping power transfer operations in this way, device 12 will no longer cause the temperature of battery 24 to rise.
While operating in the power-transfer-halted mode, inverter 60 does not supply PWM signals to coil 42, wireless power signals 44 are absent, and the ASK in-band transmitter of transceiver 46 does not send in-band signals to device 12 (i.e., ASK transmissions from device 24 to device 12 are interrupted). Nevertheless, device 24 is able to transmit at least one DC bit of information to device 12 (e.g., to indicate whether power transmission resumption is desired or not). This one bit of information may be conveyed to device 12 by adjusting the impedance of the wireless power receiving circuit formed from coil 48 and capacitor 78 with an impedance adjustment circuit (which may be implemented using a switch and capacitor or other circuitry in in transceiver 46 or using a separate switch and capacitor or other circuitry).
As shown in
During operation, device 12 can use short measurement pulses (impulses provided with inverter 60) and measurement circuitry 41 to monitor the impulse response impedance of coil 42 (and therefore the impedance of coil 48 and its associated wireless power receiving circuitry). When device 12 detects an impedance of Z1, device 12 can conclude that device 24 is not requesting a resumption of power transfer. When device 12 detects an impedance of Z2, device 12 can conclude that device 24 is requesting a resumption of wireless power transmission operations. The state of device 24 (whether requesting a resumption of power transmission or not) can be conveyed to device 12 without simultaneously conveying power signals 44 from device 12 to device 24 and using ASK in-band communications (e.g., without using transceiver 46 to transmit an in-band data stream).
To allow device 24 to determine whether device 12 is present (e.g., to determine whether coil 48 is still overlapping coil 42), device 24 can be provided with an impulse detection circuit. In the example of
The voltage on voltage divider 80 contains impulses (pulses) corresponding to the impulses in transmitted signals from inverter 60. With one illustrative configuration, inverter 60 produces a series of short pulses whenever wireless power transmission has been temporarily halted. The impulse detection circuitry of device 24 can detect these pulses, so that device 24 is made aware that device 12 and device 24 are still coupled, even though power transmission operations have been halted.
The impulse detection circuitry in device 24 consumes a small amount of power and will therefore not significantly drain the battery of device 24. The pulses that are generated by inverter 60 in device 12 when power transmission is halted may be 4 microseconds in duration or may have other suitable short durations (e.g., at least 1 microsecond, at least 0.2 microseconds, less than 16 microseconds, less than 100 microseconds, less than 500 microseconds, etc.). The pulses may be supplied with any suitable period (e.g., a period of at least 10 ms, at least 100 ms, at least 200 ms, at least 500 ms, less than 10 s, less than 3 s, less than 1 s, less than 750 ms, etc.). The amount of energy expended in producing these impulses is negligible compared to the amount of energy expended in attempting to use transceiver circuitry 46 to send in-band data to device 12 while device 12 sends bursts (e.g., 10-30 ms bursts) of PWM power signals 44 from device 12 to device 24. While the short-duration impulses are being sent, rectifier 50 does not harvest power from these transmitted impulses and there is no wireless power transfer to device 24. The power stored in battery 58 will slowly decrease due to the power expended by circuit 42 in monitoring the impulses from device 12 and due to any power expended in other background tasks (e.g., monitoring battery temperature to determine when the battery temperature has fallen to an acceptable temperature for resumed charging, etc.). These power requirements for the halted-power-transfer mode are small, so the power-transfer-halted mode of operation may sometimes be referred to as a low-power mode or a low-power-wireless-power-transfer-halted mode.
During the power-transfer-halted mode, device 12 can use measurement circuitry 41 to measure the impedance Z of coil 42 (and associated coil 48).
In an illustrative embodiment, switching circuitry (e.g., switch SW and optionally one or more additional switches) can be used to switch additional circuit components (e.g., one or more capacitors) into use (e.g., so that the impedance can be changed to one of two or more different values (e.g., from Z 1 to either Z2 or Z3, as an example). The use of optional additional switching circuits provides device 24 with the ability to send device 12 more than a single binary mode switching command during halted-power-transfer mode operations, if desired. Configurations in which device 24 uses switch SW to switch between two states (e.g., closed and open states) are illustrative.
During the operations of block 100, device 12 can use measurement circuit 41 to measure the free-space impedance of coil(s) 42 (see, e.g., impedance Z0 of
At a later time, after device 24 has been placed on device 12, system 8 may be used in wireless power transfer operations. In particular, system 8 may be operated in a first mode in which power is actively transferred between device 12 and device 24 or a second mode in which power transfer is temporarily stopped.
Wireless power may, as an example, be transmitted between device 12 and device 24 during the operations of block 102. During the operations of block 102, system 8 operates in an active power transfer mode (sometimes referred to as a power-being-transferred mode or an active wireless power transfer mode).
Wireless power transmission operations may be halted during the operations of block 104. During the operations of block 104, system 8 operates in a power-transfer-halted mode (sometimes referred to as a wireless-power-transfer-halted mode). Power transfer operations can be halted, for example, because the temperature of battery 58 has exceeded a predetermined temperature threshold value or because device 12 determines that power transmission should be halted. Once the temperature of battery 58 drops sufficiently (e.g., as measured by control circuitry 30 using a temperature sensor in devices 56) or other appropriate conditions have been satisfied, wireless power transfer operations can be resumed.
As shown in
If control circuitry 30 determines that power transfer operations should be halted (e.g., because a temperature sensor in device 24 indicates that battery 58 has become too hot or because other conditions have been satisfied), control circuitry 30 directs device 12 to halt wireless power transmission (e.g., by sending a halt command via in-band communications using transceiver 46 that is received by transceiver 40). Control circuitry 30 knows that device 24 is in communication with device 12, because device 24 is receiving power from device 12. Upon receiving the halt command, device 12 stops transmitting wireless power to device 24 and system 8 enters the wireless-power-transfer-halted mode (block 104). Upon transitioning to the operations of block 104 or earlier (e.g., during the operations of block 102), switch SW is opened.
During the operations of block 104, no wireless power is transferred from device 12 to device 24. Device 12 uses inverter 60 to generate a train of short impulses while using measurement circuitry 41 to measure the impulse response of coil 42 and thereby determine the impedance of coil 42 (and associated impedance of coil 48). The measured impedance is monitored by device 12 and is compared to the known free-space impedance of block 100 to confirm to device 12 that device 24 remains present during the operations of block 104. Device 24 uses impulse response measurement circuitry (
While power transfer is halted, device 24 can maintain switch SW in an open state. This causes the wireless power receiving circuit with coil 48 and therefore the wireless power transmission circuit with coil 42 to exhibit first impedance values (e.g., a first impedance (Z1), as described in connection with
In response to detection of a mode switching impedance change while operating in the power-transfer-halted mode, device 12 resumes the transfer of wireless power (e.g., inverter 60 resumes sending PWM alternating-current signals to coil 42 and rectifier 50 supplies DC output based on the received signals at coil 48). System 8 exits the power-transfer-halted mode (block 104) and enters the active-power-transfer mode (block 102).
The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.
This application claims the benefit of provisional patent application No. 62/653,276, filed Apr. 5, 2018, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62653276 | Apr 2018 | US |
