Patent Application
20160261137
1. Technical Field
The apparatus and techniques described herein relate generally to wireless power delivery, and to detection of devices to be charged or powered by a wireless power transmitter.
2. Discussion of the Related Art
Wireless Power Transfer Systems (WPTS) are gaining increasing popularity as convenient way to deliver power without wires or connectors. WPTS currently under development in the industry can be separated in two major classes: magnetic induction (MI) systems and magnetic resonance (MR) systems. Both types of systems include a transmitting unit, sometimes referred to as a power transmitting unit (PTU), and a receiving unit, sometimes referred to as a power receiving unit (PRU). Typically, the PTU is used to wirelessly charge mobile devices such as smartphones, portable music players, tablets, and laptops, among other devices and applications. The mobile devices may include a PRU.
Inductive WPTS typically operate in an allocated frequency range of several hundred kilohertz using frequency variation as a power flow control mechanism. MR WPTS typically operate on a single resonant frequency using input voltage regulation to regulate output power. In typical applications, MR WPTS operate at a frequency of 6.78 MHz.
Several industry committees such as the Wireless Power Consortium (WPC), the recently-merged Power Matters Alliance (PMA), and the Alliance for Wireless Power (A4WP), collectively A4WP/PMA, are working on developing international standards for consumer products based on wireless power transfer. The standards may include, for example, specifications on an amount of rectified current, voltage, and/or power generated at a PRU via the device's receiving coil and power rectification circuitry. In addition to these standards, some governing bodies may place restrictions relating to safety and/or energy consumption on consumer electronics.
Described embodiments relate to apparatus and methods for detecting and confirming that a device to be charged has been placed in a charging region of a wireless power transmitter. The methods include operating the wireless power transmitter in a low-power, standby operating mode during which a first method of device detection is employed. In various embodiments, the first method of device detection consumes significantly less power than device-detection schemes employed by conventional wireless power transmitters. The first method of device detection may be based on capacitive or optical detection. Following tentative detection of a device to be charged, a wireless power transmitter may switch to a second method of device detection. The second method may be an inductive method, and may confirm the presence of a device to be charged.
According to some embodiments, a wireless power transmitter comprises an object-sensing circuit that is configured to receive a first signal from an object sensor that is separate from a transmit coil of the wireless power transmitter, wherein applying power to the transmit coil is not required to activate the object sensor. The object-sensing circuit may be further configured to process the first signal to determine a proximity of an object to the wireless power transmitter, and provide a control signal to activate the transmit coil in response to determining proximity of the object.
In some implementations, a wireless power transmitter may comprise a charging region designated for placement of a device to be charged by the wireless power transmitter. The wireless power transmitter may further include a transmit coil adjacent to the region, an inductive sensor configured to detect a change of inductance of the transmit coil, and an object sensor different from the inductive sensor that is configured to detect the presence of an object placed in the charging region. The object sensor may be a capacitive or optical sensor.
Methods for operating a wireless power transmitter are also contemplated. In some embodiments, a method of operating a wireless power transmitter comprises acts of operating the wireless power transmitter in a standby mode, and activating an object-sensing circuit, wherein the activating does not require applying power to a transmit coil of the wireless power transmitter. A method may further include processing a first signal from an object sensor, determining from the first signal a proximity of an object to the wireless power transmitter, and responsive to determining the proximity of the object, providing a second signal to activate the transmit coil of the wireless power transmitter.
In some implementations, a method for detecting the presence of a device to be charged by a wireless power transmitter may include acts of operating the wireless power transmitter in a standby mode, detecting, by an object sensor of the wireless power transmitter, the presence of an object in a charging region of the wireless power transmitter, and responsive to detecting the presence of an object in the charging region by the object sensor, activating an inductive sensor to confirm the presence of a device to be charged in the charging region.
The foregoing summary is provided by way of illustration and is not intended to be limiting.
In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like reference character. For purposes of clarity, not every component may be labeled in every drawing. Directional and orientation references made with respect to the drawings are for teaching purposes only, and are not meant to limit directions or configurations of the described apparatus. The drawings are not necessarily drawn to scale, with emphasis instead being placed on illustrating various aspects of the techniques and devices described herein.
Conventionally, a wireless power transmitter 100 (as depicted in
Although inductance-based sensing to determine the presence of a device 110 in the charging area 102 makes use of the transmit coil of the wireless power transmitter, the inventors have recognized that this approach to sensing a device 110 can consume an appreciable amount of power during a standby operating mode of the wireless power transmitter 100. The inventors have recognized and appreciated that in some cases, the amount of power consumed for sensing a device during the standby mode may result in excessive “standby” power consumption.
Referring again to
Further details of a wireless power transmitter 100 are depicted in
The transmit coil 230 may comprise a conductive coil having a central axis and open area 235. The coil 230 may comprise one or multiple conductive turns, and may be connected to a power converter 220. Coil 230, or any coil described herein, may have any suitable shape (e.g., square, rectangular, polygonal, circular, oval, etc.). A transmit coil 230 may be formed from one or multiple wound wires, or may be patterned as one or more conductive current loops on one or more levels of a printed circuit board. An oscillating current applied to the conductive coil produces an oscillating magnetic field in the vicinity of the coil 230, and can extend through the wireless power transmitter's casing 105.
According to some embodiments, a wireless power transmitter 100 may further include a processor 240 or control circuitry and a signal transceiver 250. The processor may comprise a microcontroller, microprocessor, digital signal processor (DSP), field programmable gate array (FPGA), analog circuitry, logic circuitry, or a combination thereof, by way of example. The processor 240 may be in communication with at least one memory device (not shown), which may store machine-readable instructions that can be executed by the processor to adapt the wireless power transmitter 100 to execute operations related to power transmission. The memory device may include RAM, ROM, flash memory, cached memory, or any other suitable memory. The processor 240 may also communicate with the power converter 220. For example, the processor may be connected to the power converter with one or more electrical connections through which power and data may be transferred. Processor 240 may manage control of the wireless power transmitter 100 by coordinating operation of, sending data to, and processing data from the power converter 220 and transceiver 250.
In some embodiments, the transceiver 250 may comprise a radio-frequency (RF) transmitter for transmitting and receiving data signals to and from an external device (e.g., a device 110 to be charged). Transceiver 250 may be configured for Wi-Fi or Bluetooth communications, for example, though transceiver 250 is not limited to only these communication protocols. In some implementations, transceiver 250 may be configured for wired communications (e.g., via a universal serial bus). In some implementations, the transceiver may include separate transmitting and receiving chips or circuits. In some embodiments, the transceiver 250 may use a same magnetic coupling link that is used for wireless power transmission to send and receive data from a wireless power receiving device 110. Such communication processes may include, but are not limited to, “in-band communications,” “load modulation,” or “backscatter modulation”.
According to some embodiments, a wireless power transmitter 100 may operate in a high-power state when charging a device placed in the charging region 102. When the device 110 is fully charged or is removed from the wireless power transmitter, the wireless power transmitter may automatically transition to a standby operating mode. For example, the wireless power transmitter 100 may communicate with the device 110 to be charged, and determine when the device has reached a maximum charging level. The wireless power transmitter 100 may then transition to a standby operating mode.
According to some embodiments, a wireless power transmitter 100 may be configured to detect the presence of a device 110 placed in the charging region 102, while the wireless power transmitter is in a standby operating mode. For example, after a device 110 has been removed from the charging region and while the wireless power transmitter is in the standby operating mode, the transmitter 100 may be configured to determine whether a device 110 has been placed in the charging area. Conventionally, the determination may be done by powering up the transmit coil of the transmitter. If the transmitter 100 determines that a device has been placed in the charging area, the transmitter may automatically transition to a charging state so that a user need not provide input to the wireless power transmitter to initiate charging.
In an effort to reduce power consumption by a wireless power transmitter 100 when sensing devices 110 during a standby operating mode, the inventors have conceived of apparatus and techniques for low-power detection of devices placed in a charging region 102 of a wireless power transmitter 100.
The at least one electrode 320 may be connected to a capacitive-sensing circuit 310 that is configured to evaluate capacitance of the at least one electrode 320. For example, the capacitive-sensing circuit 310 may detect changes in capacitance of the at least one electrode from a nominal value of capacitance that is measured when no device is placed in the charging area 102. When an object or device is placed in the charging area (e.g., in close proximity to the transmit coil 230), the capacitance of the at least one electrode may change and the change may be detected by the capacitive-sensing circuit 310 to indicate proximity of the object or device.
According to some embodiments, an output from the capacitive-sensing circuit may be communicated to and received by the controller 240 of the wireless power transmitter. The controller 240 may evaluate a signal received from the capacitive-sensing circuit 310 and, based upon the received value, activate the transmit coil 230 to inductively sense and confirm the presence of a device 110 in the charging area 102 of the wireless power transmitter. In some implementations, the presence of a device 110 in the charging area can be confirmed using an inductive-sensing technique.
The inductive-sensing technique may be realized by sensing one or more of a number of quantities that include, but are not limited to, coil inductance, AC coil current, AC coil voltage, coil quality factor, reflected impedance, voltage-to-standing-wave ratio, and amplifier input current. A receiver placed in the charging area will generally create a real and/or imaginary impedance shift of the transmit coil's impedance that causes a disturbance on one or more of these quantities. Inductive sensing requires that the inductive coil be energized to transmit an electromagnetic beacon, which may result in a significant level of power consumption.
The inventors have recognized and appreciated that the amount of power consumed for capacitive sensing can be significantly less than the amount of power consumed for inductive sensing. For example, inductive sensing conventionally requires powering the transmit coil 230 at least intermittently at high power levels that can require brief bursts of power at the 100 mW level or higher. Capacitive sensing circuits, such as the circuit depicted in
In some embodiments, a wireless power transmitter 100 can be configured to use a first, low-power, sensing apparatus and method (e.g., capacitive sensing) to initially detect the presence of an object proximal to the charging area, when operating in a standby mode. The first sensing apparatus and method can be activated intermittently during the standby operating mode. Once an object is sensed, control circuitry of the wireless power transmitter 100 can activate a higher-power sensing apparatus and method (e.g., inductive sensing) to confirm the presence of a device 110 to be charged.
An alternative embodiment of a capacitive-sensing apparatus for a wireless power transmitter is depicted in
Alternatively, a thin conductive film 442 may be formed adjacent to the ferromagnetic shield 440 and used as an electrode of a capacitive sensor. For example, a thin film of metal or other conductor, which may be non-magnetic, may be formed on (above or below) the ferromagnetic shield 440 when it is manufactured. The thin film may be electrically connected to the capacitive-sensing circuit 310, which can evaluate a capacitance of the thin film. A proximal device 110 can alter the thin film's capacitance, which can be detected by the capacitive-sensing circuit and reported to the controller.
Other low-power sensing techniques are also contemplated.
The light source 520 may be arranged to illuminate at least a portion of a device 110 placed in the charging region 102 of a wireless power transmitter, as depicted in the elevation view of
In some implementations, the light source 520 and photodetector 530 may be mounted below a circuit board 505 that contains a transmit coil 230 and ferromagnetic shield 440. Holes may be opened through the circuit board 505 and ferromagnetic shield 440 for the light beam 525 and backscattered beam 527 to pass. When a device is not placed in the charging region 102, there may be little or no backscattered beam to the photodetector 530.
According to some implementations the light source 520 may be flashed for a brief period of time (e.g., less than 10 ms or even less than 1 ms) intermittently while the wireless power transmitter is operating in a standby mode. The flashing can be repeated at regular intervals (e.g., 1-4 times per second or less). By flashing the light source 520 briefly, power consumption can be appreciably reduced during standby mode.
If a measured value greater than the threshold value has been detected from the first sensor, a controller of the wireless power transmitter may activate 640 a second sensor (e.g., an inductive sensor) different from the first sensor. This may comprise activating a magnetic beacon using the transmit coil 230 to inductively sense the presence of a device 110. The controller may then determine 650 from the second sensor whether a wireless power receiving device 110 is present in the charging area 102 of the wireless power transmitter.
If it is determined 650 that a wireless power receiving device is not located in the charging area, the controller may delay 655 for a period of time before reactivating 620 the first sensor. Additionally, the controller may deactivate the transmit coil 230 and return to a standby mode.
If it is determined that a wireless power receiving device 650 is located in the charging area 102, the controller 240 may determine 660 whether the wireless power receiving device is fully charged. If it is determined that the wireless power receiving device is fully charged, the wireless power transmitter may re-enter 610 the standby mode. If it is determined that the wireless power receiving device is not charged, or not fully charged, the wireless power transmitter may enter 670 a power transfers state and transfer power 680 to the wireless power receiving device 110. During operation in the power transfer state the wireless power transmitter may repeatedly determine 660 whether the wireless power receiving device 110 is fully charged.
An output from the oscillator circuit 705 may be provided to a frequency-comparison circuit 730 along with a signal from a reference clock 720. The frequency of the reference clock may be fixed. Changes in the oscillation frequency from the oscillator circuit 705 (due to changes in capacitance C2 at sensor electrode 320) can be determined by comparison to the reference clock. The changes in the RC oscillator's frequency will cause changes in an output signal Sout from the frequency-comparison circuit 730. According to some embodiments, the output signal Sout may be provided to a comparator or signal processor (not shown) to detect a threshold crossing. Detection of the threshold crossing, e.g., by control circuitry, may cause issuance of a control signal to activate inductive sensing for a wirelessly powered or chargeable device.
In some embodiments, components of a capacitive-sensing circuit and/or logic circuitry for implementing acts of a method 600 for sensing an object may be included in an integrated circuit, such as an application-specific integrated circuit (ASIC) or field-programmable gate array (FPGA), for a wireless power transmitter. In some implementations, components of a capacitive-sensing circuit and/or logic circuitry for implementing acts of method 600 may be included on a printed circuit board (PCB) for a wireless power transmitter. In some embodiments, acts of a method 600 may be executed at least in part by a microcontroller or microprocessor adapted to operate a wireless power transmitter.
Various aspects of the apparatus and techniques described herein may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described in the foregoing description and is therefore not limited in its application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments.
Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.
Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” “containing,” “involving,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. For example, an apparatus, structure, device, layer, or region recited as “including,” “comprising,” or “having,” “containing,” “involving,” a particular material is meant to encompass at least the material listed and any other elements or materials that may be present.
This application claims priority to U.S. provisional application Ser. No. 62/129,112, titled “Wireless Charging Transmitter Using Capacitive Sensing for Device Detection,” filed Mar. 6, 2015, which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62129112 | Mar 2015 | US |
