PATENT DOCUMENT

Publication Number: US-10886781-B2
Application Number: US-201815997508-A
Country: US
Kind Code: B2

Title: Wireless power transmitting circuitry with multiple modes

Abstract:
A wireless power transmitting device includes a plurality of coils and respective wireless power transmitting circuitry coupled to each coil. The wireless power transmitting circuitry coupled to each coil may include an inverter and adjustable circuitry that is configured to mitigated radiated emissions in nominally passive coils in the power transmitting device. The wireless power transmitting circuitry coupled to each coil in the wireless power transmitting device may include adjustable circuitry coupled to an inverter output terminal in parallel or in series with the coil. The adjustable circuitry may have a variable capacitance that is controlled based on whether the coil is in an active or passive mode. The capacitance of the adjustable circuitry may be varied in a repeating cycle when the coil is in a passive mode. The adjustable circuitry may include one or more capacitors coupled between the inverter output terminal and ground.

Claims:
What is claimed is: 
     
       1. A wireless power transmitting device with a charging surface configured to receive a wireless power receiving device, the wireless power transmitting device comprising:
 a plurality of coils configured to transmit wireless power signals; 
 a plurality of inverters each having an output terminal coupled to a corresponding coil in the plurality of coils, wherein each coil of the plurality of coils is coupled to respective
 adjustable circuitry having a variable capacitance coupled in series with the coil; and 
 
 control circuitry configured to control the variable capacitance of the adjustable circuitry of each coil of the plurality of coils based on a determination indicative of whether the coil is in an active mode in which the inverter of the coil is enabled or a passive mode in which the inverter of the coil is disabled, wherein each coil of the plurality of coils is operable in the active mode and in the passive mode, and the control circuitry is configured to control a first coil in the active mode to transmit at least a portion of the wireless power signals while the control circuitry controls the variable capacitance of the adjustable circuitry of a second coil in the passive mode to reduce magnetic coupling into the second coil. 
 
     
     
       2. The wireless power transmitting device of  claim 1 , wherein the control circuitry is configured to control the variable capacitance of the adjustable circuitry for each coil of the plurality of coils in the active mode to be equal to a first capacitance. 
     
     
       3. The wireless power transmitting device of  claim 2 , wherein the control circuitry is configured to control the variable capacitance of the adjustable circuitry for each coil of the plurality of coils in the passive mode to be equal to a second capacitance that is different than the first capacitance. 
     
     
       4. The wireless power transmitting device of  claim 1 , wherein the control circuitry is configured to control the inverter of each coil of the plurality of coils in the active mode to generate an alternating current signal at the inverter output terminal. 
     
     
       5. The wireless power transmitting device of  claim 4 , wherein the control circuitry is configured to disable the inverter of each coil of the plurality of coils in the passive mode. 
     
     
       6. The wireless power transmitting device of  claim 1 , wherein the adjustable circuitry for each coil comprises:
 first and second capacitors coupled in series between the coil and ground. 
 
     
     
       7. The wireless power transmitting device of  claim 6 , wherein the adjustable circuitry for each coil comprises:
 a transistor that is coupled to a node that is interposed between the first and second capacitors. 
 
     
     
       8. The wireless power transmitting device of  claim 7 , wherein the transistor for each coil is coupled between the node and the ground. 
     
     
       9. The wireless power transmitting device of  claim 7 , wherein the transistor for each coil is coupled between the node and an additional node that is interposed between the first capacitor and the coil. 
     
     
       10. A wireless power transmitting device with a charging surface configured to receive a wireless power receiving device, the wireless power transmitting device comprising:
 a plurality of coils configured to transmit wireless power signals; 
 a plurality of inverters each having an output terminal coupled to a corresponding coil in the plurality of coils, wherein each coil of the plurality of coils is coupled to respective adjustable circuitry comprising:
 a capacitor coupled to the coil; and 
 a transistor coupled in series with the capacitor and the coil; and 
 
 control circuitry configured to control the transistor of each coil in a first portion of the plurality of coils to be in a first state while that coil in the first portion is in an active mode, and to control the transistor of each coil in a remaining portion of the plurality of coils to be in a second state while that coil in the remaining portion is in a passive mode. 
 
     
     
       11. The wireless power transmitting device of  claim 10 , wherein the control circuitry is configured to assert the transistor to couple the capacitor of the coil to ground in the first state. 
     
     
       12. The wireless power transmitting device of  claim 10 , wherein the control circuitry is configured to deassert the transistor to couple the capacitor to a floating node in the second state. 
     
     
       13. A wireless power transmitting device with a charging surface configured to receive a wireless power receiving device, the wireless power transmitting device comprising:
 wireless power transmitting circuitry having a plurality of coils that are configured to transmit wireless power signals, a plurality of inverters each having an output terminal directly connected to a corresponding coil in the plurality of coils, and a plurality of adjustable circuits each having a terminal directly connected to the output terminal of a corresponding inverter in the plurality of inverters and each coupled in parallel with the corresponding coil in the plurality of coils; and 
 control circuitry configured to operate a given coil in the plurality of coils as an active coil to transmit the wireless power signals in a first mode in which the adjustable circuit for the given coil exhibits a first capacitance and to operate the given coil as a nominally passive coil in a second mode in which the adjustable circuit for the given coil exhibits a second capacitance to mitigate radiated emissions from the given coil. 
 
     
     
       14. The wireless power transmitting device of  claim 13 , wherein the control circuitry is configured to vary a capacitance of the adjustable circuit for the given coil according to a predetermined pattern that includes at least the second capacitance and a third capacitance. 
     
     
       15. The wireless power transmitting device of  claim 14 , wherein the control circuitry is configured to vary the capacitance of the adjustable circuit for the given coil according to the predetermined pattern while the given coil is in the second mode. 
     
     
       16. The wireless power transmitting device of  claim 15 , wherein the control circuitry is configured to disable the inverter for the given coil while the given coil is in the second mode. 
     
     
       17. The wireless power transmitting device of  claim 13 , wherein the adjustable circuit for the given coil comprises a first capacitor and a first switch coupled in series between the output terminal of the inverter for the given coil and ground. 
     
     
       18. The wireless power transmitting device of  claim 17 , wherein the adjustable circuit for the given coil comprises a second capacitor and a second switch coupled in series between the output terminal of the inverter for the given coil and the ground, a third capacitor and a third switch coupled in series between the output terminal of the inverter for the given coil and the ground, and a fourth capacitor and a fourth switch coupled in series between the output terminal of the inverter for the given coil and the ground and wherein the first capacitor and the first switch, the second capacitor and the second switch, the third capacitor and the third switch, and the fourth capacitor and the fourth switch are coupled in parallel between the output terminal of the inverter for the given coil and the ground. 
     
     
       19. The wireless power transmitting device of  claim 13 , wherein the adjustable circuit for the given coil comprises a first capacitor coupled between the output terminal of the inverter for the given coil and a first bias voltage supply line. 
     
     
       20. The wireless power transmitting device of  claim 19 , wherein the adjustable circuit for the given coil comprises a second capacitor coupled between the output terminal of the inverter for the given coil and a second bias voltage supply line, a third capacitor coupled between the output terminal of the inverter for the given coil and a third bias voltage supply line, and a fourth capacitor coupled between the output terminal of the inverter for the given coil and a fourth bias voltage supply line.

Description:
This application claims the benefit of provisional patent application No. 62/652,124, filed Apr. 3, 2018, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to power systems, and, more particularly, to wireless power systems for charging electronic devices. 
     BACKGROUND 
     In a wireless charging system, a wireless charging mat wirelessly transmits power to a portable electronic device that is placed on the mat. The portable electronic device has a coil and rectifier circuitry. The coil receives alternating-current wireless power signals from a coil in the wireless charging mat that is overlapped by the coil in the portable electronic device. The rectifier circuitry converts the received signals into direct-current power. 
     SUMMARY 
     A wireless power system has a wireless power transmitting device and a wireless power receiving device. The wireless power transmitting device has an array of transmit coils that produce wireless power signals. The wireless power receiving device has a receive coil that receives wireless power signals from the wireless power transmitting device and has a rectifier that produces direct-current power from the received wireless power signals. 
     The wireless power transmitting device has respective wireless power transmitting circuitry coupled to each coil. Each coil and accompanying wireless power transmitting circuitry may be operable in an active mode in which the coil is used to transmit wireless power signals and a passive mode in which the coil is not used to transmit wireless power signals. The wireless power transmitting circuitry coupled to each coil may include adjustable circuitry that is configured to mitigated radiated emissions in nominally passive coils in the power transmitting device. 
     The wireless power transmitting circuitry coupled to each coil in the wireless power transmitting device may include adjustable circuitry coupled to an inverter output terminal in parallel with the coil. The adjustable circuitry may have a variable capacitance that is controlled based on whether the coil is in an active or passive mode. The adjustable circuitry may include one or more capacitors coupled between the inverter output terminal and ground. The capacitance of the adjustable circuitry may be varied in a repeating cycle when the coil is in a passive mode. 
     The wireless power transmitting circuitry coupled to each coil in the wireless power transmitting device may include adjustable circuitry coupled to an inverter output terminal in series with the coil. The adjustable circuitry may have a variable capacitance that is controlled based on whether the coil is in an active or passive mode. The adjustable circuitry may include one or more capacitors coupled between the coil and ground. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative wireless charging system that includes a wireless power transmitting device and a wireless power receiving device in accordance with an embodiment. 
         FIG. 2  is a top view of an illustrative wireless power transmitting device having a charging surface on which a wireless power receiving device has been placed in accordance with an embodiment. 
         FIG. 3  is a circuit diagram of illustrative wireless power transmitting circuitry and wireless power receiving circuitry in accordance with an embodiment. 
         FIG. 4  is a circuit diagram of illustrative wireless power transmitting circuitry with a filtering capacitor coupled in parallel with a coil in accordance with an embodiment. 
         FIG. 5  is a circuit diagram of illustrative wireless power transmitting circuitry with variable capacitance circuitry coupled in parallel with a coil in accordance with an embodiment. 
         FIG. 6  is a circuit diagram of illustrative wireless power transmitting circuitry with variable capacitance circuitry including fixed capacitors and switches coupled in parallel with a coil in accordance with an embodiment. 
         FIG. 7  is a circuit diagram of illustrative wireless power transmitting circuitry with variable capacitance circuitry including fixed capacitors coupled to bias voltage supply lines coupled in parallel with a coil in accordance with an embodiment. 
         FIG. 8  is a flow chart of illustrative operations involved in operating wireless power transmitting circuitry with variable capacitance circuitry coupled in parallel with a coil in accordance with an embodiment. 
         FIG. 9  is a state diagram showing illustrative operating modes for wireless power transmitting circuitry of the type shown in  FIGS. 4-7  in accordance with an embodiment. 
         FIG. 10  is a circuit diagram of illustrative wireless power transmitting circuitry with variable capacitance circuitry coupled in series with a coil in accordance with an embodiment. 
         FIGS. 11 and 12  are circuit diagrams of illustrative wireless power transmitting circuitry with variable capacitance circuitry including a transistor and two fixed capacitors coupled in series with a coil in accordance with an embodiment. 
         FIG. 13  is a state diagram showing illustrative operating modes for wireless power transmitting circuitry of the type shown in  FIGS. 10-12  in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A wireless power system includes a wireless power transmitting device such as a wireless charging mat. The wireless power transmitting device wirelessly transmits power to a wireless power receiving device such as a wristwatch, cellular telephone, tablet computer, laptop computer, or other electronic equipment. The wireless power receiving device uses power from the wireless power transmitting device for powering the device and for charging an internal battery. 
     An illustrative wireless power system (wireless charging system) is shown in  FIG. 1 . As shown in  FIG. 1 , wireless power system  8  includes a wireless power transmitting device such as wireless power transmitting device  12  and includes a wireless power receiving device such as wireless power receiving device  24 . Wireless power transmitting device  12  includes control circuitry  16 . Wireless power receiving device  24  includes control circuitry  30 . Control circuitry in system  8  such as control circuitry  16  and control circuitry  30  is used in controlling the operation of system  8 . This control circuitry may include processing circuitry associated with microprocessors, power management units, baseband processors, digital signal processors, microcontrollers, and/or application-specific integrated circuits with processing circuits. The processing circuitry implements desired control and communications features in devices  12  and  24 . For example, the processing circuitry may be used in selecting coils, determining power transmission levels, processing sensor data and other data, processing user input, handling negotiations between devices  12  and  24 , sending and receiving in-band and out-of-band data, making measurements, and otherwise controlling the operation of system  8 . 
     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 device, 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 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 case for an accessory, 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. 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  (e.g., each coil may have respective power transmitting circuitry). Coils  42  may be arranged in a planar coil array (e.g., in configurations in which device  12  is a wireless charging mat). 
     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  may be used in powering a battery such as battery  58  and may 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, 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 ). 
     Device  12  and/or device  24  may communicate wirelessly using in-band or 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  may also use one or more coils  42  to transmit in-band signals that are received by wireless transceiver circuitry  46  using coil  48 . Similarly, wireless transceiver circuitry  46  may use one or more coils  48  to transmit in-band signals that are received by wireless transceiver circuitry  40  using coil  42 . Any suitable modulation scheme may be used to support in-band communications between device  12  and device  24 . 
     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, between 100 kHz and 200 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. 
     In some cases, wireless transceiver circuitry  40  in power transmitting device  12  and wireless transceiver circuitry  46  in power receiving device  24  may communicate in-band by modulating the AC drive signals that are used to transfer power. Frequency shift keying (FSK), amplitude shift keying (ASK), or any other desired modulation of the AC drive signals may be used to convey in-band data between device  12  and device  24  (e.g., while power is conveyed wirelessly from device  12  to device  24 ). Wireless transceiver circuitry  40  and wireless transceiver circuitry  46  may also be configured to inject one or more data carrier waves (that have a different frequency than the AC drive signals) to the AC drive signals used for wireless power transfer. The data carrier waves may be transmitted between devices  12  and  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 . 
     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 in control circuitry  30  and/or in control circuitry  16  may also be used in making current and voltage measurements. 
     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  FIG. 1  is present, which could increase the measured inductance of any overlapped coil  42 . Signal measurement circuitry  41  is configured to apply signals to the coil and measure corresponding signal responses. For example, signal measurement circuitry  41  may apply an alternating-current probe signal while monitoring a resulting signal at a node coupled to the coil. As another example, signal measurement circuitry  41  may apply a pulse to the coil and measure a resulting impulse response (e.g., to measure coil inductance). Using measurements from measurement circuitry  41 , the wireless power transmitting device can determine whether an external object is present on the coils. If, for example, all of coils  42  exhibit their expected nominal response to the applied signals, control circuitry  16  can conclude that no external devices are present. If one of coils  42  exhibits a different response (e.g., a response varying from a normal no-objects-present baseline), control circuitry  16  can conclude that an external object (potentially a compatible wireless power receiving device) is present. 
     Control circuitry  30  has measurement circuitry  43 . In an illustrative arrangement, measurement circuitry  43  of control circuitry  30  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, 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), provide 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. 
     A top view of an illustrative configuration for device  12  in which device  12  has an array of coils  42  is shown in  FIG. 2 . Device  12  may, in general, have any suitable number of coils  42  (e.g., 22 coils, at least 5 coils, at least 10 coils, at least 15 coils, fewer than 30 coils, fewer than 50 coils, etc.). Coils  42  of device  12  may be covered by a planar dielectric structure such as a plastic member or other structure forming charging surface  70 . The lateral dimensions (X and Y dimensions) of the array of coils  42  in device  12  may be 1-1000 cm, 5-50 cm, more than 5 cm, more than 20 cm, less than 200 cm, less than 75 cm, or other suitable size. Coils  42  may overlap or may be arranged in a non-overlapping configuration. In a non-overlapping configuration, the coils may be arranged in a single layer (e.g., in a plane parallel to the XY-plane) such that no part of any coil overlaps any of the other coils in the layer. Alternatively, in an overlapping arrangement (as shown in  FIG. 2 ), coils  42  may be organized in multiple layers. Within each layer, the coils do not overlap. However, coils in one layer may overlap coils in one or more other layers (e.g., when viewed from above the outline of a given coil in a given layer may intersect the outline of a coil in another layer). In one illustrative example, the device may have three layers of coils (e.g., a lower layer having eight coils, a middle layer having seven coils, and an upper layer having seven coils). In general, each layer may have any suitable number of coils (e.g., at least 2 coils, at least 5 coils, fewer than 9 coils, fewer than 14 coils, 6-9 coils, etc.). Device  12  may have one layer of coils, at least two layers of coils, at least three layers of coils, at least four layers of coils, fewer than five layers of coils, 4-6 layers of coils, etc. Coils  42  can be placed in a rectangular array having rows and columns and/or may be tiled using a hexagonal tile pattern or other pattern. 
     System  8  may be configured to accommodate the simultaneous charging of multiple devices  24 . However, illustrative operations involved in operating system  8  to provide power wirelessly to a single device  24  are described herein as an example. A user of system  8  may place wireless power receiving devices such as device  24  of  FIG. 2  on device  12  for charging. Magnetic coupling coefficient k represents the amount of magnetic coupling between transmitting and receiving coils in system  8 . Wireless power transfer efficiency scales with k, so optimum charging (e.g., peak efficiency) may be obtained by evaluating the coupling coefficient k for each coil and choosing appropriate coil(s) to use in transmitting wireless power to device  24  based on the coupling coefficients. 
     Illustrative circuitry of the type that may be used for forming power transmitting circuitry  52  and power receiving circuitry  54  of  FIG. 1  is shown in  FIG. 3 . As shown in  FIG. 3 , power transmitting circuitry  52  may receive a DC voltage Vin (e.g., from AC-DC converter  14  shown in  FIG. 1 ). Control circuitry  16  ( FIG. 1 ) may produce control signals that are applied to gate terminals  82  of transistors T 1  and T 2  of inverter  60 . With one illustrative configuration, the inverter circuitry includes multiple inverter circuits such as inverter  60  of  FIG. 3  each of which is controlled by control circuitry  16  of device  12  and each of which is coupled to a respective one of coils  42 . After coupling coefficients k have been determined for each coil  42 , control circuitry  16  can switch appropriate coil(s)  42  into use by selecting corresponding inverters  60  to use in driving signals into the coils. 
     Gates  82  of transistors T 1  and T 2  may receive complementary signals so that the gate of T 1  is high when the gate of T 2  is low and vice versa. With one illustrative configuration, transistors T 1  and T 2  may be supplied with an AC signal at 200 kHz or other suitable frequency that is modulated with a PWM envelope at 2 kHz or other suitable PWM frequency. Other suitable control signals may be applied to T 1  and T 2 , if desired. Transistors T 1  and T 2  may be characterized by an internal diode and drain-source capacitance (see, e.g., capacitances Cds 1  and Cds 2 ), as shown schematically in  FIG. 3 . Transistors T 1  and T 2  may be metal-oxide-semiconductor transistors or other suitable transistors. 
     Transistors T 1  and T 2  are coupled in series between a positive voltage terminal (at power supply voltage Vin) and a ground power supply terminal (at ground voltage Vss). Coil  42  has a first terminal coupled to an output terminal  92  between transistors T 1  and T 2  and a second terminal coupled to ground via capacitor Ctx. As the control signals are applied to gates  82  of output transistors T 1  and T 2 , the DC voltage Vin is converted into an AC current that passes through capacitor Ctx and coil  42  (having a self-inductance of Ltx). This produces corresponding electromagnetic signals  44  (magnetic fields), which are electromagnetically coupled into coil  48  in wireless power receiving circuitry  54 . In general, coil  42  in  FIG. 3  may represent one or more wireless power transmitting coils in device  12 , optionally arranged in an array as shown in  FIG. 2 . Similarly, coil  48  in  FIG. 3  may represent one or more wireless power receiving coils in device  24 . 
     The degree of electromagnetic (magnetic) coupling between coils  42  and  48  is represented by magnetic coupling coefficient k. Signals  44  are received by coil  48  (having a self-inductance of Lrx). Coil  48  and capacitor Crx are connected to rectifier  50 . During operation, the AC signals from coil  48  that are produced in response to received signals  44  are rectified by rectifier  50  to produce direct-current output power (e.g., direct-current rectifier output voltage Vo) across output terminals  65 . Terminals  65  are connected to and provide power to the load of power receiving device  24  (e.g., battery  58  and other components in device  24  that are being powered by the direct-current power supplied from rectifier  50 ). 
     As previously discussed, control circuitry  16  can switch appropriate coil(s)  42  into use by selecting corresponding inverters  60  to use in driving signals at the power transmission frequency into the coils. The coils that are switched into use by the control circuitry  16  (and therefore transmit wireless power signals) may be referred to as active coils. Coils that are not used to transmit wireless power signals may be referred to as passive (or inactive) coils. Control circuitry  16  may disable the inverters that are associated with passive coils, for example. Controlling whether a coil is active or passive may be important to operation of wireless power transmission device  12 . Active coils may be specifically selected to prevent wireless power signals from being delivered to incompatible electronic devices or foreign objects, for example. Additionally, active coils may be selected to meet radiated emission limits for the wireless power transmitting device. Therefore, it is desirable for the coils that are nominally passive to actually be passive. 
     However, in a power transmitting device with multiple coils (e.g., as shown in  FIG. 2 ), magnetic coupling and leakage from the active coils to the passive coils may cause the nominally passive coils to have high levels of radiated emissions (i.e., unintentional release of electromagnetic energy). Magnetic coupling and leakage from the active coils to the passive coils may occur at both the fundamental frequency (e.g., the power transmission frequency) and at harmonic frequencies of the fundamental frequency. Power transmission circuitry  52  of power transmitting device  12  may therefore include circuitry to mitigate radiated emissions in nominally passive coils in the power transmitting device. 
     Illustrative circuitry of the type that may be used for forming power transmitting circuitry  52  is shown in  FIG. 4 . Each coil  42  may have respective power transmitting circuitry (sometimes referred to as a respective power transmitting circuit). The circuitry of  FIG. 4  has an inverter  60  with direct-current power supply input terminals  63 , output terminal  92 , and ground terminal  94 . As previously discussed coil  42  may be coupled in series with capacitor  102  (Ctx) between inverter output terminal  92  and ground (e.g., ground terminal  94 ). As shown in  FIG. 4 , transistor  104  may also be coupled in series with coil  42  and capacitor  102 . Control circuitry  16  ( FIG. 1 ) may produce control signals that are applied to gate terminal  105  of transistor  104 . Transistor  104  may be asserted when power transmitting circuitry  52  is being used to transmit wireless power (e.g., coil  42  is active) and may be deasserted when power transmitting circuitry  52  is not being used to transmit wireless power (e.g., coil  42  is passive or inactive). Transistor  104  may be used to mitigate leakage at the fundamental frequency from active coils to passive coils in wireless power transmitting device  12 . This will be discussed in greater detail later (in connection with  FIG. 9 ). First, mitigating leakage due to cross-coupling of harmonics will be discussed. 
     As shown in  FIG. 4 , wireless power transmitting circuitry may include a capacitor  106  that is coupled between output terminal  92  of inverter  60  and ground. Capacitor  106  may be a low-pass filter that filters out high frequencies. For example, capacitor  106  may filter signals having a frequency greater than 30 MHz (or any other desired frequency). Capacitor  106  may be coupled in parallel with coil  42 , capacitor  102 , and transistor  104  (e.g., between inverter output terminal  92  and ground). Although capacitor  106  may be useful in filtering out high frequency signals from wireless power transmission circuitry  52 , capacitor  106  may cause unintentional resonance in the circuitry at harmonic frequencies (e.g., at the fifth harmonic). 
     To reduce radiated emissions caused by capacitor  106 , wireless power transmitting circuitry may instead include adjustable circuitry having a variable capacitance coupled in parallel with coil  42 , capacitor  102 , and transistor  104 . An arrangement of this type is shown in  FIG. 5 . As shown in  FIG. 5 , adjustable circuitry  108  (sometimes referred to as adjustable capacitance circuitry or variable capacitance circuitry) is coupled between output terminal  92  of inverter  60  and ground. Adjustable circuitry  108  may include any desired components that allow the capacitance coupled to output terminal  92  to be changed. For example, adjustable circuitry  108  may include one or more fixed capacitors, one or more variable capacitors, one or more switches (e.g., that switch fixed capacitors or variable capacitors into or out of the circuit), one or more bias voltage supply lines, etc. 
     When a particular coil  42  is passive, the adjustable circuitry  108  in the wireless power transmitting circuitry of that coil may be dynamically changed to reduce the voltage induced into the coil at harmonic frequencies. For example, the adjustable circuitry  108  may vary between a minimum capacitance value and a maximum capacitance value with any desired number of intervening capacitances (evenly spaced or unevenly spaced). The minimum capacitance value may be below 10 nanofarads (nF), below 6 nanofarads, below 4 nanofarads, between 3 and 5 nanofarads, between 2 and 6 nanofarads, between 5 and 7 nanofarads, between 2 and 8 nanofarads, below 1 nanofarads, below 0.1 nanofarad, below 0.01 nanofarads, below 100 nanofarads, below 1000 nanofarads, greater than 10 nanofarads (nF), greater than 6 nanofarads, greater than 4 nanofarads, greater than 1 nanofarads, greater than 0.1 nanofarads, greater than 0.01 nanofarads, greater than 100 nanofarads, greater than 1000 nanofarads, etc. The maximum capacitance value may be below 10 nanofarads (nF), below 6 nanofarads, below 4 nanofarads, between 8 and 12 nanofarads, between 9 and 11 nanofarads, between 5 and 15 nanofarads, between 7 and 10 nanofarads, below 1 nanofarads, below 0.1 nanofarads, below 0.01 nanofarads, below 100 nanofarads, below 1000 nanofarads, greater than 10 nanofarads (nF), greater than 6 nanofarads, greater than 4 nanofarads, greater than 1 nanofarad, greater than 0.1 nanofarads, greater than 0.01 nanofarads, greater than 100 nanofarads, greater than 1000 nanofarads, etc. 
     The length of time the capacitance of adjustable circuitry  108  remains constant (before being changed to a different capacitance) may be any desired time interval. For example, the time interval may be less than 10 seconds, less than 1 second, less than 0.1 seconds, less than 0.01 seconds, less than 1 millisecond, less than 0.1 milliseconds, less 0.01 milliseconds, greater than 10 seconds, greater than 1 second, greater than 0.1 seconds, greater than 0.01 seconds, greater than 1 millisecond, greater than 0.1 milliseconds, less 0.01 milliseconds etc. The time interval may be fixed or may vary. 
     Adjustable circuitry  108  may consistently cycle through any desired number of capacitances. For example, adjustable circuitry  108  may have two, more than four, more than eight, more than twelve, more than sixteen, sixteen, more than twenty, less than four, less than eight, less than twelve, less than sixteen, or less than twenty different states (each with a corresponding unique capacitance). The components of adjustable circuitry  108  may receive control signal(s)  110  (e.g., from control circuitry  16 ) that place the components into a desired state with a corresponding desired capacitance. The capacitance of adjustable circuitry  108  may be varied in a repeating cycle or in any other desired way. When coil  42  is active, adjustable circuitry  108  may be fixed (e.g., may remain in a single state with a single corresponding capacitance) or may be varied (e.g., in the same manner as when coil  42  is passive or in a different manner as when coil  42  is passive). If desired, when coil  42  is passive, control circuitry  16  may set adjustable circuitry  108  to a fixed capacitance value (instead of cycling through different capacitances). For example, based on the position of the passive coil relative to the active coils in the power transmitting device, the control circuitry may select a capacitance for adjustable circuitry  108  that minimizes radiated emissions. 
       FIGS. 6 and 7  show examples of components that may be used to implement variable capacitance circuitry  108 . As shown in  FIG. 6 , variable capacitance circuitry  108  may include a plurality of fixed capacitors that are enabled or disabled using corresponding switches. Capacitor  112 - 1  and switch  114 - 1  are coupled in series between inverter output terminal  92  and ground. Capacitor  112 - 2  and switch  114 - 2  are coupled in series between inverter output terminal  92  and ground. Capacitor  112 - 3  and switch  114 - 3  are coupled in series between inverter output terminal  92  and ground. Capacitor  112 - 4  and switch  114 - 4  are coupled in series between inverter output terminal  92  and ground. Capacitors  112 - 1 ,  112 - 2 ,  112 - 3 , and  112 - 4  (and their corresponding switches) are all connected in parallel (between output terminal  92  and ground). 
     Each switch may receive a corresponding control signal (e.g., from control circuitry  16 ) that is used to connect (e.g., enable) or disconnect (e.g., disable) the associated capacitor. Switch  114 - 1  receives control signal  110 - 1 , switch  114 - 2  receives control signal  110 - 2 , switch  114 - 3  receives control signal  110 - 3 , and switch  114 - 4  receives control signal  110 - 4 . Connecting and disconnecting different subsets of the capacitors will change the effective capacitance of variable capacitance circuitry  108 . In  FIG. 6 , variable capacitance circuitry  108  may be referred to as a capacitor bank (e.g., a 4-bit digital capacitor bank). The example of the capacitor bank in  FIG. 6  including four capacitors is merely illustrative. Any desired number of capacitors may be included in the capacitor bank of  FIG. 6 . 
     In another example, shown in  FIG. 7 , adjustable circuitry  108  may include a plurality of fixed capacitors that are coupled to respective bias voltage supply lines. Capacitor  122 - 1  is coupled between inverter output terminal  92  and bias voltage supply line  124 - 1 . Capacitor  122 - 2  is coupled between inverter output terminal  92  and bias voltage supply line  124 - 2 . Capacitor  122 - 3  is coupled between inverter output terminal  92  and bias voltage supply line  124 - 3 . Capacitor  122 - 4  is coupled between inverter output terminal  92  and bias voltage supply line  124 - 4 . Each bias voltage supply line provides a respective bias voltage (e.g., using control circuitry  16 ). Bias voltage supply line  124 - 1  provides bias voltage V BIAS1 , bias voltage supply line  124 - 2  provides bias voltage V BIAS2 , bias voltage supply line  124 - 3  provides bias voltage V BIAS3 , and bias voltage supply line  124 - 4  provides bias voltage V BIAS4 . 
     The bias voltages supplied by the bias voltage supply lines may be controlled to change the capacitance of adjustable circuitry  108 . For example, V BIAS1  may be changed from ground to a different bias voltage to change the effective capacitance of capacitor  122 - 1 . In this way, the capacitance may be controlled by the bias voltage supply lines (this technique is sometimes referred to as bottom plate sampling). The example in  FIG. 7  of including four capacitors to form adjustable circuitry  108  is merely illustrative. Any desired number of capacitors may be included in the variable capacitance of  FIG. 7 . 
       FIG. 8  is a flow chart of illustrative operations involved in using wireless power transmitting device  12 . In particular,  FIG. 8  shows illustrative operations involved in controlling adjustable circuitry  108  in a passive coil (e.g., while the coil is in a passive mode). During the operations of block  202 , control circuitry  16  may set adjustable circuitry  108  to a first capacitance for a first length of time. After the first length of time, control circuitry  16  may set adjustable circuitry  108  to a second capacitance that is different than the first capacitance for a second length of time. The first and second lengths of time may be any desired lengths of time (and may be the same or may be different). These steps may repeat for as many capacitance values as desired. At step  206 , control circuitry  16  may set adjustable circuitry  108  to an n th  capacitance. After progressing through the desired number (n) of capacitances for adjustable circuitry  108 , the method may loop back to step  202 . This cycle may proceed continuously. Control circuitry  16  may set adjustable circuitry  108  to the various capacitances using any desired techniques (e.g., opening and closing switches as in  FIG. 6 , controlling bias voltages as in  FIG. 7 , etc.). 
     As previously discussed, adjustable circuitry  108  is used to mitigate leakage due to cross-coupling of harmonics. Transistor  104  (in  FIGS. 4-7 ) may be used to mitigate leakage at the fundamental frequency from active coils to passive coils in wireless power transmitting device. Transistor  104  is in series with coil  42  and capacitor  102 . Capacitor  102  may have a first terminal coupled to coil  42  and a second terminal coupled to transistor  104 . When transistor  104  is asserted, the second terminal of capacitor  102  is coupled to ground. However, there may be magnetic coupling between active and passive coils at the fundamental frequency when transistor  104  is asserted. When transistor  104  is deasserted, the second terminal of capacitor  102  will be floating (e.g., the second terminal is coupled to a floating node), reducing magnetic coupling into coil  42 . Therefore, transistor  104  may be asserted when power transmitting circuitry  52  is being used to transmit wireless power (e.g., coil  42  is active) and may be deasserted when power transmitting circuitry  52  is not being used to transmit wireless power (e.g., coil  42  is passive or inactive). 
     A state diagram showing illustrative operating modes for wireless power transmitting circuitry  52  of the type shown in  FIGS. 4-7  is shown in  FIG. 9 . As shown, the wireless power transmitting circuitry may be operable in an active mode  302  (e.g., when the wireless power transmitting circuitry is used to transmit wireless power using coil  42 ). In active mode  302 , the wireless power transmitting circuitry may assert transistor  104 , coupling capacitor  102  to ground. Also in the active mode, the inverter  60  of the wireless power transmitting circuitry may be used to generate an AC signal at the inverter output terminal. The wireless power transmitting circuitry may also be operable in passive mode  304  (when the wireless power transmitting circuitry is not used to transmit wireless power using coil  42 ). In passive mode  304  (sometimes referred to as inactive mode  304 ), the wireless power transmitting circuitry may deassert transistor  104 , causing capacitor  102  to be coupled to a floating node. Also in the passive mode, the inverter  60  of the wireless power transmitting circuitry may be disabled. 
     The example of using a transistor to switch a capacitor between being coupled to ground and being coupled to a floating node to mitigate radiated emissions is merely illustrative. In another embodiment, adjustable circuitry having a variable capacitance may be coupled in series with coil  42 . Examples of this type are shown in  FIGS. 10-12 . 
     As shown in  FIG. 10 , adjustable circuitry  132  (sometimes referred to as adjustable capacitance circuitry or variable capacitance circuitry) may be coupled in series with coil  42  between inverter output terminal  92  and ground. Variable capacitance circuitry  132  and coil  42  may be parallel to adjustable circuitry  108 . Variable capacitance circuitry  132  may include any desired components that allow the capacitance coupled in series with coil  42  to be changed. For example, variable capacitance circuitry  132  may include one or more fixed capacitors, one or more variable capacitors, one or more switches (e.g., that switch fixed capacitors or variable capacitors into or out of the circuit), one or more bias voltage supply lines, etc. 
     When a particular coil  42  is active, the adjustable circuitry  132  in the wireless power transmitting circuitry of that coil may be set to a capacitance that causes the coil to resonate at the fundamental frequency. In contrast, when a particular coil is passive, the adjustable circuitry  132  in the wireless power transmitting circuitry of that coil may be changed to a different capacitance that causes the coil to resonate at a different frequency than the fundamental frequency. Adjustable circuitry  132  may have any desired capacitance in the active mode and in the passive mode. 
       FIGS. 11 and 12  are examples of components that may be used to implement adjustable circuitry  132  in  FIG. 10 .  FIG. 11  shows an example where fixed capacitors  134  and  136  are coupled in series between coil  42  and ground. Additionally, a transistor  138  is coupled between ground and a node  140  that is interposed between capacitors  134  and  136 . Control circuitry  16  ( FIG. 1 ) may produce a control signal that is applied to gate terminal  139  of transistor  138 . When transistor  138  is asserted, capacitor  136  will be bypassed and capacitor  134  will set the effective capacitance of variable capacitance  132 . When transistor  138  is deasserted, capacitors  134  and  136  will both contribute to the effective capacitance of adjustable circuitry  132 . The capacitances of capacitors  134  and  136  may be selected such that coil  42  resonates when the transistor is either asserted or deasserted. 
       FIG. 12  shows another example, similar to  FIG. 11 , where fixed capacitors  134  and  136  are coupled in series between coil  42  and ground. In this example, however, transistor  138  is coupled between node  140  and node  142  (that is interposed between coil  42  and capacitor  134 ). Therefore, when transistor  138  is asserted, capacitor  134  will be bypassed and capacitor  136  will set the effective capacitance of variable capacitance  132 . When transistor  138  is deasserted, capacitors  134  and  136  will both contribute to the effective capacitance of adjustable circuitry  132 . The capacitances of capacitors  134  and  136  may be selected such that coil  42  resonates when the transistor is either asserted or deasserted. 
     A state diagram showing illustrative operating modes for wireless power transmitting circuitry  52  of the type shown in  FIGS. 10-12  is shown in  FIG. 13 . As shown, the wireless power transmitting circuitry may be operable in an active mode  402  (e.g., when the wireless power transmitting circuitry is used to transmit wireless power using coil  42 ). In active mode  402 , the wireless power transmitting circuitry may set adjustable circuitry  132  to a first capacitance. Also in the active mode, the inverter  60  of the wireless power transmitting circuitry may be used to generate an AC signal at the inverter output terminal. The wireless power transmitting circuitry may also be operable in passive mode  404  (when the wireless power transmitting circuitry is not used to transmit wireless power using coil  42 ). In passive mode  404  (sometimes referred to as inactive mode), the wireless power transmitting circuitry may set adjustable circuitry  132  to a second capacitance that is different than the first capacitance. Also in the passive mode, the inverter  60  of the wireless power transmitting circuitry may be disabled. In the examples of  FIGS. 11 and 12 , transistor  138  may be in an opposite state in the active mode and the passive mode. For example, if transistor  138  is asserted in the active mode, transistor  138  is deasserted in the passive mode. If transistor  138  is deasserted in the active mode, transistor  138  is asserted in the passive mode. 
     The above embodiments referring to component  138  as a transistor are merely illustrative. In general, for any switch or transistor referred to herein, any desired component capable of electrically connecting/disconnecting two terminals may be used (e.g., a transistor, a mechanical switch, etc.). 
     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.

Metadata:
Filing Date: 20180604
Publication Date: 20210105
Grant Date: 20210105
Priority Date: 20180403
Inventors: MANTHA, SOUMYA
WALIA, MANJIT S.
SABNANI, RAHUL A.
XU, YILING
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J7/00712", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M3/33571", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M3/33571", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M1/0064", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M1/0058", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M1/44", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/00712", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y02B70/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M7/537", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M7/537", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/025", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01F38/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/12", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 68053962