(19)
(11)EP 3 240 142 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
06.05.2020 Bulletin 2020/19

(21)Application number: 17163997.4

(22)Date of filing:  30.03.2017
(51)International Patent Classification (IPC): 
H02J 50/12(2016.01)

(54)

AUTOMATIC TUNING OF RESONANCE-BASED WIRELESS CHARGING RECEIVER

AUTOMATISCHE ABSTIMMUNG EINES RESONANZBASIERTEN DRAHTLOSEN LADEEMPFÄNGERS

SYNTONISATION AUTOMATIQUE D'UN RÉCEPTEUR DE CHARGE SANS FIL REPOSANT SUR LA RÉSONANCE


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 26.04.2016 US 201615138322

(43)Date of publication of application:
01.11.2017 Bulletin 2017/44

(73)Proprietor: NXP B.V.
5656 AG Eindhoven (NL)

(72)Inventors:
  • Crosby, Robert, Glenn ll
    Redhill, Surrey RH1 1QZ (GB)
  • Christiaans, Peter
    Redhill, Surrey RH1 1QZ (GB)
  • Wu, Qiong
    Redhill, Surrey RH1 1QZ (GB)

(74)Representative: Miles, John Richard 
NXP SEMICONDUCTORS Intellectual Property Group Abbey House 25 Clarendon Road
Redhill, Surrey RH1 1QZ
Redhill, Surrey RH1 1QZ (GB)


(56)References cited: : 
EP-A2- 0 829 940
WO-A2-2011/036659
US-A1- 2015 076 920
WO-A1-2015/005106
US-A1- 2011 193 417
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description


    [0001] This disclosure relates generally to wireless power transfer and more specifically to a method and apparatus for automatically tuning a resonance-based wireless charging receiver.

    [0002] Wireless charging and transfer technology has been developed to enable the efficient transistor of power to devices such as mobile phones and tablet PCs without the use of wires. The alliance for Wireless Power (A4WP) is a standards body set up to help enable the efficient transfer of power wirelessly. A typical wireless charging receiver includes a series-parallel resonator connected to a rectifier circuit. Typically, an inductor loop in each of the transmitter and the receiver functions as an antenna for the power transfer. The electrical coupling efficiency for a particular transmitter/receiver antenna combination varies both spatially and by operating conditions. Correspondingly, the power transfer is highly affected by the operating conditions, including rectifier voltage, power to the rectifier, and by the orientation and distance between the receiver and transmitter inductor loop antennas. The problem is compounded for relatively small antennas.

    [0003] WO 2011/036659 discloses an inductive power receiver for providing a regulated power output to an electric load. A receiver-side regulator is provided to regulate the output voltage of the inductive transfer system. The regulator has a resonance-altering component and a switching unit configured to selectively connect the resonance-altering component to the reception circuit such that the amplitude of the induced voltage is controlled. US 2011/0193417 discloses wireless a power transmission apparatus that includes: a transmitter that wirelessly transmits electric power; and a receiver that can receive, in a resonant relation with the transmitter, a transmission signal including the electric power transmitted from the transmitter, wherein the receiver includes a frequency variable unit that can change a reception resonant frequency; a detecting unit that detects reception power; and a control unit that controls the frequency variable unit to perform frequency adjustment such that the reception power detected by the detecting unit is maximized. US 2015/0076920 discloses a complementary metal oxide semiconductor wireless power receiver that may include a receiver chip with an inductor, a configurable capacitance, and a rectifier. A disclosed method may include receiving an RF signal utilizing the inductor, extracting a clock signal from the received RF signal, generating a DC voltage utilizing a rectifier circuit, sampling the DC voltage, and adjusting the configurable capacitance based on the sampled DC voltage. WO 2015/005106 discloses a control circuit, a resonance circuit, an electronic device, a control method, a control program, and a semiconductor element that are capable of taking into consideration the time constant during control voltage application by a variable capacitance capacitor and of measuring and adjusting circuits in a short time. EP 0829940 discloses a power transmission system, an IC card, and an information communication system using an IC card. In the IC card, the transmitted induced power is converted into a DC voltage, the transmitted induced power or a voltage corresponding to the induced power is detected, and a desired DC voltage to be supplied to the internal circuit is obtained in controlling impedance based on the detected induced power or the voltage corresponding to the induced power.

    [0004] Therefore, a need exists for a method that provides efficient wireless power transfer for varying operating conditions.

    [0005] The present invention is illustrated by way of example and is not limited by the accompanying figures, in which like references indicate similar elements. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale.

    FIG. 1 illustrates, in block diagram form, a wireless charging system in accordance with an embodiment.

    FIG. 2 illustrates a flowchart of a method for automatically adjusting the receiver antenna impedance in the wireless charging system of FIG. 1.

    FIG. 3 illustrates, in schematic diagram form, another embodiment of the impedance matching circuit of FIG. 1.

    FIG. 4 illustrates, in schematic diagram form, another embodiment of the impedance matching circuit of FIG. 1.



    [0006] A method according to the present invention in defined in claim 1. A wireless power receiver according to the present invention in defined in claim 9. Further embodiments are defined in the dependent claims.

    [0007] Generally, there is provided, an apparatus and method for automatically tuning the antenna impedance of a wireless charging receiver in a wireless charging system. The wireless charging system may be used, for example, to charge a battery in a portable handheld device. The apparatus includes a resonator network coupled between an antenna and a rectifier circuit. The resonator network has both series-connected and normally also has parallel-connected capacitors. At least one of the capacitors is a tunable variable capacitor. A capacitance value of the at least one variable capacitor is automatically adjusted based on an error voltage between a target rectifier voltage and a measured rectifier voltage. Automatically adjusting the resonator network impedance of the receiver provides the best power transfer for changing operating conditions. In one embodiment, one or more of the parallel-connected capacitors are variable capacitors. In another embodiment, one or more of the series-connected capacitors are variable capacitors.

    [0008] There is provided, a method for adjusting an antenna resonance impedance network of a wireless charging receiver during a wireless charging operation, the wireless charging receiver being inductively coupled to a wireless charging transmitter, the method comprising: measuring an output voltage of a voltage rectifier, the voltage rectifier coupled to the antenna resonance impedance network; determining whether or not the output voltage is between upper and lower limits; if the output voltage is not between the upper and lower limits, determining an error voltage based on the output voltage and a target output voltage; changing a capacitance of a variable capacitive element in the antenna resonance impedance network; and determining if there is an improvement in the error voltage. Changing the capacitance of the variable capacitive element may further comprise changing a tuning voltage from a digital-to-analog converter to the variable capacitive element based on the error voltage. Measuring the output voltage may further comprise providing the output voltage to an analog-to-digital converter. If the output voltage is between the upper and lower limits, determining that an impedance of the antenna resonance impedance network is matched to an impedance of the wireless charging transmitter. Determining the error voltage may further comprise calculating a difference between the output voltage of the voltage rectifier and the target rectifier voltage. The method may further comprise converting the error voltage to a plurality of bits for being provided to a digital-to-analog converter, the digital-to-analog converter coupled to the variable capacitive element. Measuring the output voltage of the voltage rectifier may further comprise measuring an output voltage of a MOSFET bridge rectifier. Changing the capacitance of the variable capacitive element may further comprise changing a tuning voltage from a digital-to-analog converter to the variable capacitive element using a host controller. Determining the error voltage based on the output voltage and the target output voltage may further comprise determining the error voltage based on a magnitude of a difference between the output voltage and the target output voltage.

    [0009] There is provided, a method in a wireless charging receiver having an antenna coupled to an input of a resonance network, the resonance network having an output coupled to a rectifier circuit, and the resonance network including an adjustable impedance element, the method comprising: storing a target rectifier voltage; measuring a first output voltage of rectifier circuit; determining if the first output voltage of the rectifier circuit is within an upper limit and a lower limit; if the first output voltage is not within the upper and lower limits, calculating a first error voltage as a difference between the first output voltage and the target rectifier voltage; changing the impedance of the adjustable impedance element by a first set amount; measuring a second output voltage of the rectifier circuit; calculating a second error voltage as a difference between the second output voltage and the target rectifier voltage; determining if the second error voltage is lower than the first error voltage; changing the first set amount to a second set amount based on determining if the second error voltage is lower than the first error voltage; and changing the impedance of the adjustable impedance element by the second set amount. The method may further comprise: updating the target rectifier voltage; measuring a third output voltage of the rectifier circuit; and determining if the third output voltage is between the upper and lower limits. The method may further comprise updating the target rectifier voltage using a host controller. Calculating the first error voltage as a difference between the first output voltage and the target rectifier voltage may further comprise calculating the first error voltage as a magnitude of the different between the first output voltage and the target rectifier voltage. Changing the impedance of the adjustable impedance element by a first set amount may further comprise using a digital-to-analog converter to control the adjustable impedance element and wherein the first set amount comprises a least significant bit of the first error voltage. Measuring a first output voltage of rectifier circuit may further comprise using an analog-to-digital converter to receive the first output voltage from the rectifier circuit.

    [0010] There is provided, a wireless charging receiver comprising: an antenna; a resonance network having an input coupled to the antenna, and an output, the resonance network having an impedance matching circuit comprising a variable impedance element; a rectifier circuit having an input coupled to the output of the impedance matching circuit, and an output for providing a rectifier output voltage; an analog-to-digital converter having an input coupled to receive the rectifier output voltage, and an output; control logic having an input coupled to the output of the analog-to-digital, and an output; and a digital-to-analog converter having an input coupled to the output of the control logic, and an output coupled to provide a tuning voltage to the variable impedance element. The variable impedance element may be a variable capacitor. The impedance matching circuit may comprise: a first capacitor having a first terminal coupled to a first terminal of the antenna, and a second terminal; a second capacitor having a first terminal coupled to a second terminal of the antennal, and a second terminal; a third capacitor having a first terminal coupled to the second terminal of the first capacitor, and a second terminal, and a second terminal coupled to the second terminal of the second capacitor; and the variable impedance element has a first terminal coupled to the first terminal of the antenna, a second terminal coupled to the second terminal of the antenna, and a control terminal coupled to the output of the digital-to-analog converter. The rectifier circuit may be a MOSFET bridge rectifier, or one or more of the MOSFET transistors may be replaced with Schottky diodes. The wireless charging receiver may further comprise a host controller coupled to the control logic.

    [0011] FIG. 1 illustrates, in block diagram form, a wireless charging system 10 in accordance with an embodiment. Wireless charging system 10 includes wireless charging transmitter circuit 12, wireless charging receiver 14, and host controller 48. Wireless charging transmitter circuit 12 is connected to an inductor loop antenna 13. Wireless charging receiver 14 includes resonance network 16 and control circuit 18. Resonance network 16 includes inductor loop antenna 15, rectifier circuit 22, RC circuit 24, and rectifier logic 40. Impedance matching circuit 20 includes variable capacitor 26 and capacitors 28, 30, and 32. Rectifier circuit 22 is a MOSFET bridge rectifier circuit having MOSFET transistors 33, 34, 35, and 36. RC (resistance-capacitance) circuit 24 includes capacitor 38 and resistor 39. At least a portion of the resistance of resistor 39 represents the electrical load of the rectifier. Control circuit 18 includes analog-to-digital converter (ADC) 42, control logic 44, and digital-to-analog converter (DAC) 46. Control circuit 18 may be implemented as one or more integrated circuits. Alternately, other portions of wireless charging receiver 14 can be integrated with control circuit 18, such as rectifier circuit 22 and rectifier logic 40.

    [0012] In wireless charging receiver 14, antenna 15 has a first terminal connected to a first terminal of variable capacitor 26, and a second terminal connected to a second terminal of variable capacitor 26. Variable capacitor 26 has a control terminal for receiving a control signal labeled "VTUNE". Capacitor 28 has a first terminal connected to the second terminal of antenna 15, and a second terminal. Capacitor 30 has a first terminal connected to the first terminal of antenna 15. Capacitor 32 has a first terminal connected to the second terminal capacitor 30, and a second terminal connected to the second terminal of capacitor 28.

    [0013] In rectifier circuit 22, N-channel transistor 33 has a first current electrode for providing a rectifier output voltage labeled "VRECT", a control electrode, and a second current electrode coupled to the second terminal of capacitor 30 for receiving a voltage labeled "AC1". N-channel transistor 34 has a first current electrode connected to the second current electrode of N-channel transistor 33, a control electrode, and a second current electrode connected to a power supply voltage terminal labeled "VSS". In the illustrated embodiment, VSS is connected to ground, or zero volts. N-channel transistor 35 has a first current electrode connected to the first current electrode of N-channel transistor 33, a control electrode, and a second current electrode connected to the second terminal of capacitor 28 for receiving a voltage labeled "AC2". Voltages AC1 and AC2 together are differential voltages. In another embodiment, one or more of the MOSFET transistors may be replaced with Schottky diodes.

    [0014] In RC circuit 24, capacitor 38 has a first terminal connected to the first current electrodes of N-channel transistors 33 and 35, and a second terminal connected to power supply voltage terminal VSS. Resistor 39 has a first terminal connected to the first terminal of capacitor 38, and a second terminal connected to the second terminal of capacitor 38. RC circuit 24 provides stability to rectifier voltage VRECT. Resistor 39 represents the electrical load of rectifier 22.

    [0015] In control circuit 18, ADC 42 has a first input connected to the first current electrodes of N-channel transistors 33 and 35 of rectifier circuit 22, and an output and a second input. Control logic 44 has a first output connected to the second input of ADC 42, a second output, a first input connected to the output of ADC 42, and a second input connected to an output of host controller 48. Digital-to-analog converter 46 has an output connected to the second output of control logic 44, and an output for providing control signal VTUNE to the control terminal of variable capacitor 26.

    [0016] In operation, loop antenna 15 is placed in proximity to antenna 13. An alternating electrical current in loop antenna 13 from transmitter circuit 12 causes an alternating electrical current in loop antenna 15. Power is transferred from antenna 12 to antenna 15 according to conventional electromagnetic theory. The power transfer is highly affected by the operating conditions, including rectifier voltage, power to the rectifier, and by the orientation and distance between the transmitter and receiver inductor loop antennas 13 and 15, respectively. Depending on the size and shape of loop antennas 13 and 15, the power transfer can be very sensitive to the positioning of receiver antenna 15 to transmitter antenna 13. To aid in making power transfer between transmitter 12 and receiver 14 more efficient, resonance network 16 includes a variable capacitor in impedance matching circuit 20. A capacitance of variable capacitor 26 is adjusted to control rectifier voltage VRECT to be equal to, or as near as possible, a target rectifier voltage (VTAR). Note that impedance matching circuit 20 is just one embodiment of an impedance matching circuit. Also, other elements of the impedance matching circuit may be adjusted to accomplish the same or similar result. For example, in other embodiments, one or more of inductors, capacitors, or resistors may be adjustable in a manner similar to that described herein. A method for adjusting the capacitance of variable capacitor 26 will be described with reference to both FIG. 1 and FIG. 2.

    [0017] FIG. 2 illustrates a flowchart of method 50 for automatically adjusting the receiver antenna impedance in wireless charging system 10 of FIG. 1. At step 52, default values for the target rectifier voltage (VTAR), step-size, upper limit, lower limit, and DAC setpoint are loaded and stored in memory locations (not shown) to initialize wireless charger receiver 14. At step 54, target rectifier voltage VTAR is updated, if necessary. Note that the target rectifier voltage VTAR is not necessarily the highest voltage that can be obtained, but is the voltage calculated to provide the most efficient power transfer. At step 56, rectifier voltage VRECT is measured, or sampled, using ADC 42. At decision step 58, it is determined if rectifier voltage VRECT is between an upper voltage limit and a lower voltage limit. If rectifier voltage VRECT is between the upper and lower limits, then the YES path is taken to step 60. At step 60, processing is delayed for a predetermined time period to minimize the power consumed by control circuit 18 and then steps 54, 56, and 58 are repeated. If at decision step 58, voltage VRECT is determined to be outside the upper and lower limits, then the NO path is taken to step 62. At step 62, an error voltage VERR is calculated to be a magnitude, or absolute value, of the difference between rectifier voltage VRECT and stored target rectifier voltage VTAR. Generally, for the most efficient power transfer, error voltage VERR should be small, or close to zero volts. At step 64, a digital input code representing a setpoint of DAC 46 is decremented by a step-size. If the setpoint is already zero, the setpoint is not reduced below zero. In one embodiment, the step-size is equal to one least significant bit (LSB). In other embodiments, the step-size may be different. Decrementing the DAC input code changes the output voltage provided by DAC 46. For example, in one embodiment, decrementing the digital input code of DAC 46 causes the output voltage VTUNE to be lower. In one embodiment, lowering voltage VTUNE causes the capacitance of variable capacitor 26 to be less. At step 66, processing of the method is delayed by a predetermined delay to minimize power consumption of control circuit 18. In one embodiment, the predetermined delay is 10 milliseconds (ms). At step 68, rectifier voltage VRECT is measured again. At step 70, error voltage VERR is updated by performing the calculation of step 62 with the value of VRECT measured at step 68. At decision step 72, it is determined if the value of error voltage VERR is less than when it was previously calculated at step 62. If VERR is less, then the YES path is taken to step 74. At step 74, the step-size is set to one LSB if it is not already at one LSB. Referring back to decision step 58, when it was determined that VRECT was not between the upper and lower limits, it was not known whether the resonant frequency of resonance network 16 should be adjusted higher or lower to approach target rectifier voltage VTAR. A guess has to be made about whether to increase or decrease the capacitance of variable capacitor 26. The step-size is one LSB because an improvement was made in error voltage VERR, indicating that the guess was correct. After step 74 and the predetermined delay of step 60, flow returns to step 54. If at decision step 72, it is determined that error voltage VERR is not less, then the guess was wrong and the variable capacitance was changed in the wrong direction. From step 72, the NO path is taken to step 76, the step-size is doubled to two LSBs to make up for the wrong correction made in step 64 and the DAC setpoint is incremented by the new step-size. After the predetermined delay at step 78, rectifier output voltage VRECT is measured again using ADC 42 at step 80. At step 82, error voltage VERR is updated using the current voltage for VRECT. The current rectifier voltage VRECT is measured at step 80 and error voltage VERR is calculated using the calculation of step 62. At decision step 84, it is determined if the latest calculated error voltage VERR is less than the previously calculated VERR. If yes, then the YES path is taken to step 90 where the step-size is set to one LSB if it is not already one LSB, and method 50 proceeds again at delay step 60. If the error voltage VERR is not less, then the NO path is taken to step 86. At step 86 DAC setpoint is decremented by the step-size. At step 88, the step-size is incremented by one LSB, and method 50 continues at step 60.

    [0018] Method 50 automatically runs when a voltage is detected at antenna 15 and runs for as long as a charging voltage is being produced. The method and apparatus provide the advantage of improved charging efficiency for the current operating conditions. In the illustrated embodiment, rectifier voltage is measured as an indicator for efficient power transfer.

    [0019] FIG. 3 illustrates, in schematic diagram form, another embodiment 20' of the impedance matching circuit 20 of FIG. 1. In FIG. 3, antenna 15 is connected to impedance matching circuit 20'. Impedance matching circuit 20' includes capacitors 100, 102, 104, and 106 in the same circuit configuration as impedance matching circuit 20 in FIG. 1. Impedance matching circuit 20' is generally the same as impedance matching circuit 20 except that a variable impedance is provided by series capacitors 102 and 104. Variable capacitors 102 and 104 are adjusted using voltage VTUNE from DAC 46. As compared to impedance matching circuit 20, impedance matching circuit 20' allows variable capacitors to be used that have a lower voltage rating. The disadvantage is that the capacitors require a larger value and two are needed instead of just one.

    [0020] FIG. 4 illustrates, in schematic diagram form, another embodiment 20" of the impedance matching circuit 20 of FIG. 1. In FIG. 4, antenna 15 is connected to impedance matching circuit 20". Impedance matching circuit 20" includes capacitors 200, 202, 204, 206, 208, and 210. Capacitors 208 and 210 are variable capacitors tunable using voltage VTUNE from DAC 46. Capacitors 202 and 208 may be a series impedance equivalent of capacitor 102 in FIG. 3 and Capacitors 204 and 210 may be a series impedance equivalent of capacitor 104 in FIG. 3. As compared to impedance matching circuit 20 in FIG.1, impedance matching circuit 20" requires variable capacitors with a lower voltage rating. The disadvantage is that the capacitors require a larger value and two are needed instead of one.

    [0021] A wireless charging receiver operates on a resonance principle and includes an impedance matching circuit coupled between an antenna and a rectifier circuit. The impedance matching circuit has both series-connected and parallel-connected capacitors. At least one of the capacitors is a tunable variable capacitor. A method is provided for automatically adjusting a capacitance value of the at least one variable capacitor based on an error voltage between a target rectifier voltage and a measured rectifier voltage. Automatically adjusting the antenna impedance of the receiver provides for improved power transfer efficiency for changing operating conditions. In one embodiment, one or more of the parallel-connected capacitors are variable capacitors. In another embodiment, one or more of the series-connected capacitors are variable capacitors.

    [0022] Because the apparatus implementing the present invention is, for the most part, composed of electronic components and circuits known to those skilled in the art, circuit details will not be explained in any greater extent than that considered necessary as illustrated above, for the understanding and appreciation of the underlying concepts of the present invention and in order not to obfuscate or distract from the teachings of the present invention.

    [0023] Although the invention is described herein with reference to specific embodiments, various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present invention. Any benefits, advantages, or solutions to problems that are described herein with regard to specific embodiments are not intended to be construed as a critical, required, or essential feature or element of any or all the claims. Generally, in the above described embodiment, a current electrode is a source or drain and a control electrode is a gate of a metal-oxide semiconductor (MOS) transistor. Other transistor types may be used in other embodiments.

    [0024] Generally, the term "coupled," as used herein, is not intended to be limited to a direct coupling or a mechanical coupling. More specifically, the term "coupled" is not intended to be limited to magnetic resonance coupling, a direct coupling or an inductive coupling.

    [0025] Furthermore, the terms "a" or "an," as used herein, are defined as one or more than one. Also, the use of introductory phrases such as "at least one" and "one or more" in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim element to inventions containing only one such element, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an." The same holds true for the use of definite articles.

    [0026] Unless stated otherwise, terms such as "first" and "second" are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements.


    Claims

    1. A method (50) for adjusting an antenna resonance impedance network, having an impedance matching circuit comprising an adjustable impedance element, of a wireless charging receiver during a wireless charging operation, the wireless charging receiver for being inductively coupled to a wireless charging transmitter, the method comprising:

    measuring (56) a first output voltage of a rectifier circuit having an input coupled to the output of the impedance matching circuit, and an output for providing a rectifier output voltage;

    determining (58) if the first output voltage of the rectifier circuit is within an upper limit and a lower limit;

    if the first output voltage is not within the upper and lower limits:

    calculating (62) a first error voltage as a difference between the first output voltage and a stored target rectifier voltage;

    changing (64) the impedance of the adjustable impedance element by a first set amount;

    measuring (68) a second output voltage of the rectifier circuit;

    calculating (70) a second error voltage as a difference between the second output voltage and the target rectifier voltage;

    determining (72) if the second error voltage is lower than the first error voltage;

    and if it is determined that the second error voltage is not lower than the first error voltage:

    changing (76) the first set amount to a second set amount, wherein the second set amount has twice the magnitude and opposite sign of the first set amount; and

    changing the impedance of the adjustable impedance element by the second set amount.


     
    2. The method (50) of claim 1, wherein changing the impedance of the adjustable impedance element further comprises changing a tuning voltage from a digital-to-analog converter provided to the adjustable impedance element based on the first error voltage.
     
    3. The method (50) of claim 1 or 2, wherein measuring the first output voltage further comprises providing the first output voltage to an analog-to-digital converter.
     
    4. The method (50) of any preceding claim, wherein if the first output voltage is between the upper and lower limits, determining that an impedance of the antenna resonance impedance network is matched to an impedance of the wireless charging transmitter.
     
    5. The method (50) of any preceding claim, further comprising adjusting a plurality of bits based on the first error voltage, the plurality of bits for being provided to a digital-to-analog converter, the digital-to-analog converter coupled to the adjustable impedance element.
     
    6. The method (50) of any preceding claim, wherein measuring the first output voltage of the voltage rectifier further comprises measuring an output voltage of a MOSFET bridge rectifier.
     
    7. The method (50) of any of claims 1, 3, 4 or 6 wherein changing the impedance of the adjustable impedance element further comprises changing a tuning voltage from a digital-to-analog converter provided to the adjustable impedance element using a host controller.
     
    8. The method (50) of any preceding claim, wherein determining the first error voltage based on the first output voltage and the target output voltage further comprises determining the first error voltage based on a magnitude of the difference between the first output voltage and the target output voltage.
     
    9. A wireless charging receiver (14) comprising:

    an antenna (15);

    an antenna resonance impedance network (16) having an input coupled to the antenna, and an output, the antenna resonance impedance network having an impedance matching circuit (20) comprising an adjustable impedance element (26);

    a rectifier circuit (22) having an input coupled to the output of the impedance matching circuit, and an output for providing a rectifier output voltage;

    and a control circuit (18) comprising

    an analog-to-digital converter (42) having an input coupled to receive the rectifier output voltage, and an output;

    control logic (44) having an input coupled to the output of the analog-to-digital converter, and an output; and

    a digital-to-analog converter (46) having an input coupled to the output of the control logic, and an output coupled to provide a tuning voltage to the adjustable impedance element; wherein

    the wireless charging receiver is configured to:

    store a target rectifier voltage;

    measure a first output voltage of the rectifier circuit;

    determine if the first output voltage of the rectifier circuit is within an upper limit and a lower limit;

    if the first output voltage is not within the upper and lower limits:

    calculate a first error voltage as a difference between the first output voltage and the target rectifier voltage;

    change the impedance of the adjustable impedance element by a first set amount;

    measure a second output voltage of the rectifier circuit;

    calculate a second error voltage as a difference between the second output voltage and the target rectifier voltage;

    determine if the second error voltage is lower than the first error voltage;

    and if it is determined that the second error voltage is not lower than the first error voltage:

    change the first set amount to a second set amount, wherein the second set amount has twice the magnitude and opposite sign of the first set amount; and

    change the impedance of the adjustable impedance element by the second set amount.


     
    10. The wireless charging receiver (14) of claim 9, wherein the adjustable impedance element (26) is a variable capacitor.
     
    11. The wireless charging receiver of claim 9 or 10, wherein the impedance matching circuit (20) comprises:

    a first capacitor (30) having a first terminal coupled to a first terminal of the antenna (15), and a second terminal;

    a second capacitor (28) having a first terminal coupled to a second terminal of the antenna, and a second terminal;

    a third capacitor (32) having a first terminal coupled to the second terminal of the first capacitor, and a second terminal coupled to the second terminal of the second capacitor; and wherein

    the adjustable impedance element (26) has a first terminal coupled to the first terminal of the antenna, a second terminal coupled to the second terminal of the antenna, and a control terminal coupled to the output of the digital-to-analog converter (46).


     
    12. The wireless charging receiver (14) of any of claims 9 to 11, wherein the rectifier circuit (22) is a MOSFET bridge rectifier.
     
    13. The wireless charging receiver (14) of any of claims 9 to 12, further comprising a host controller (48) coupled to the control logic (44).
     


    Ansprüche

    1. Verfahren (50) zum Einstellen eines eine Impedanzanpassungsschaltung mit einstellbarem Impedanzelement aufweisenden Antennenresonanzimpedanznetzes eines drahtlosen Ladeempfängers während eines drahtlosen Ladevorgangs, wobei der drahtlose Ladeempfänger induktiv an einen drahtlosen Ladesender gekoppelt ist, wobei das Verfahren Folgendes umfasst:

    Messen (56) einer ersten Ausgangsspannung einer Gleichrichterschaltung, die einen Eingang, der an den Ausgang der Impedanzanpassungsschaltung gekoppelt ist, und einen Ausgang zum Bereitstellen einer Gleichrichterausgangsspannung aufweist;

    Bestimmen (58), ob die erste Ausgangsspannung der Gleichrichterschaltung innerhalb einer oberen Grenze und einer unteren Grenze liegt;

    falls die erste Ausgangsspannung nicht innerhalb der oberen und der unteren Grenze liegt:

    Berechnen (62) einer ersten Fehlerspannung als eine Differenz zwischen der ersten Ausgangsspannung und einer gespeicherten Zielgleichrichterspannung;

    Ändern (64) der Impedanz des einstellbaren Impedanzelements um einen ersten gesetzten Wert;

    Messen (68) einer zweiten Ausgangsspannung der Gleichrichterschaltung;

    Berechnen (70) einer zweiten Fehlerspannung als eine Differenz zwischen der zweiten Ausgangsspannung und der Zielgleichrichterspannung;

    Bestimmen (72), ob die zweite Fehlerspannung niedriger als die erste Fehlerspannung ist;

    und falls bestimmt ist, dass die zweite Fehlerspannung nicht niedriger als die erste Fehlerspannung ist:

    Ändern (76) des ersten gesetzten Wertes auf einen zweiten gesetzten Wert, wobei der zweite gesetzte Wert den doppelten Betrag und das entgegengesetzte Vorzeichen des ersten gesetzten Wertes aufweist, und

    Ändern der Impedanz des einstellbaren Impedanzelements um den zweiten gesetzten Wert.


     
    2. Verfahren (50) nach Anspruch 1, wobei das Ändern der Impedanz des einstellbaren Impedanzelements ferner das Ändern einer Abstimmspannung von einem Digital/Analog-Umsetzer, die dem einstellbaren Impedanzelement auf der Grundlage der ersten Fehlerspannung bereitgestellt wird, umfasst.
     
    3. Verfahren (50) nach Anspruch 1 oder 2, wobei das Messen der ersten Ausgangsspannung ferner das Bereitstellen der ersten Ausgangsspannung für einen Analog/Digital-Umsetzer umfasst.
     
    4. Verfahren (50) nach einem der vorhergehenden Ansprüche, wobei dann, wenn die erste Ausgangsspannung zwischen der oberen und der unteren Grenze liegt, bestimmt wird, dass eine Impedanz des Antennenresonanzimpedanznetzes an eine Impedanz des drahtlosen Ladesenders angepasst wird.
     
    5. Verfahren (50) nach einem der vorhergehenden Ansprüche, das ferner das Einstellen von mehreren Bits auf der Grundlage der ersten Fehlerspannung umfasst, wobei die mehreren Bits einem Digital/Analog-Umsetzer bereitgestellt werden, wobei der Digital/Analog-Umsetzer an das einstellbare Impedanzelement gekoppelt ist.
     
    6. Verfahren (50) nach einem der vorhergehenden Ansprüche, wobei das Messen der ersten Ausgangsspannung des Spannungsgleichrichters ferner das Messen einer Ausgangsspannung eines MOSFET-Brückengleichrichters umfasst.
     
    7. Verfahren (50) nach einem der Ansprüche 1, 3, 4 oder 6, wobei das Ändern der Impedanz des einstellbaren Impedanzelements ferner das Ändern einer Abstimmspannung von einem Digital/Analog-Umsetzer, die dem einstellbaren Impedanzelement unter Verwendung einer Host-Steuereinheit bereitgestellt wird, umfasst.
     
    8. Verfahren (50) nach einem der vorhergehenden Ansprüche, wobei das Bestimmen der ersten Fehlerspannung auf der Grundlage der ersten Ausgangsspannung und der Zielausgangsspannung ferner das Bestimmen der ersten Fehlerspannung auf der Grundlage eines Betrags der Differenz zwischen der ersten Ausgangsspannung und der Zielausgangsspannung umfasst.
     
    9. Drahtloser Ladeempfänger (14), der Folgendes umfasst:

    eine Antenne (15);

    ein Antennenresonanzimpedanznetz (16), das einen Eingang, der an die Antenne gekoppelt ist, und einen Ausgang aufweist, wobei das Antennenresonanzimpedanznetz eine Impedanzanpassungsschaltung (20) aufweist, die ein einstellbares Impedanzelement (26) umfasst;

    eine Gleichrichterschaltung (22), die einen Eingang, der an den Ausgang der Impedanzanpassungsschaltung gekoppelt ist, und einen Ausgang zum Bereitstellen einer Gleichrichterschaltung aufweist,

    und eine Steuerschaltung (18), die Folgendes umfasst:

    einen Analog/Digital-Umsetzer (42), der einen Eingang, der gekoppelt ist, um die Gleichrichterausgangsspannung zu empfangen, und einen Ausgang aufweist;

    Steuerlogik (44), die einen Eingang, der an den Ausgang des Analog/Digital-Umsetzers gekoppelt ist, und einen Ausgang aufweist, und

    einen Digital/Analog-Umsetzer (46), der einen Eingang, der an den Ausgang der Steuerlogik gekoppelt ist, und einen Ausgang, der gekoppelt ist, um dem einstellbaren Impedanzelement eine Abstimmspannung bereitzustellen, aufweist; wobei

    der drahtlose Ladeempfänger konfiguriert ist zum:

    Speichern einer Zielgleichrichterspannung;

    Messen einer ersten Ausgangsspannung der Gleichrichterschaltung;

    Bestimmen, ob die erste Ausgangsspannung der Gleichrichterschaltung innerhalb einer oberen Grenze und einer unteren Grenze liegt;

    falls die erste Ausgangsspannung nicht innerhalb der oberen und der unteren Grenze liegt:

    Berechnen einer ersten Fehlerspannung als einer Differenz zwischen der ersten Ausgangsspannung und der Zielgleichrichterspannung;

    Ändern der Impedanz des einstellbaren Impedanzelements um einen ersten gesetzten Wert;

    Messen einer zweiten Ausgangsspannung der Gleichrichterschaltung;

    Berechnen einer zweiten Fehlerspannung als einer Differenz zwischen der zweiten Ausgangsspannung und der Zielgleichrichterspannung;

    Bestimmen, ob die zweite Fehlerspannung niedriger als die erste Fehlerspannung ist;

    und falls bestimmt wird, dass die zweite Fehlerspannung nicht niedriger als die erste Fehlerspannung ist:

    Ändern des ersten gesetzten Wertes auf einen zweiten gesetzten Wert, wobei der zweite gesetzte Wert den doppelten Betrag und das entgegengesetzte Vorzeichen des ersten gesetzten Wertes aufweist, und

    Ändern der Impedanz des einstellbaren Impedanzelements um den zweiten gesetzten Wert.


     
    10. Drahtloser Ladeempfänger (14) nach Anspruch 9, wobei das einstellbare Impedanzelement (26) ein variabler Kondensator ist.
     
    11. Drahtloser Ladeempfänger nach Anspruch 9 oder 10, wobei die Impedanzanpassungsschaltung (20) Folgendes umfasst:

    einen ersten Kondensator (30), der einen ersten Anschluss, der an einen ersten Anschluss der Antenne (15) gekoppelt ist, und einen zweiten Anschluss aufweist;

    einen zweiten Kondensator (28), der einen ersten Anschluss, der an einen zweiten Anschluss der Antenne gekoppelt ist, und einen zweiten Anschluss aufweist;

    einen dritten Kondensator (32), der einen ersten Anschluss, der an den zweiten Anschluss des ersten Kondensators gekoppelt ist, und einen zweiten Anschluss, der an den zweiten Anschluss des zweiten Kondensators gekoppelt ist, umfasst; und wobei

    das einstellbare Impedanzelement (26) einen ersten Anschluss, der an den ersten Anschluss der Antenne gekoppelt ist, einen zweiten Anschluss, der an den zweiten Anschluss der Antenne gekoppelt ist, und einen Steueranschluss, der an den Ausgang des Digital/Analog-Umsetzers (46) gekoppelt ist, aufweist.


     
    12. Drahtloser Ladeempfänger (14) nach einem der Ansprüche 9 bis 11,
    wobei die Gleichrichterschaltung (22) ein MOSFET-Brückengleichrichter ist.
     
    13. Drahtloser Ladeempfänger (14) nach einem der Ansprüche 9 bis 12, der ferner eine Host-Steuereinheit (48) umfasst, die an die Steuerlogik (44) gekoppelt ist.
     


    Revendications

    1. Procédé (50) de réglage d'un réseau d'impédance de résonance d'antenne, présentant un circuit d'adaptation d'impédance comprenant un élément d'impédance réglable, d'un récepteur de charge sans fil durant une opération de charge sans fil, le récepteur de charge sans fil étant destiné à être couplé inductivement à un émetteur de charge sans fil, le procédé comprenant :

    la mesure (56) d'une première tension de sortie d'un circuit redresseur présentant une entrée couplée à la sortie du circuit d'adaptation d'impédance, et une sortie pour fournir une tension de sortie de redresseur ;

    la détermination (58) que la première tension de sortie du circuit redresseur est ou non comprise en-deçà d'une limite supérieure et d'une limite inférieure ;

    si la première tension de sortie n'est pas comprise en-deçà des limites supérieure et inférieure :

    le calcul (62) d'une première tension d'erreur comme différence entre la première tension de sortie et une tension de redresseur cible mémorisée;

    la modification (64) de l'impédance de l'élément d'impédance réglable par une première quantité définie ;

    la mesure (68) d'une seconde tension de sortie du circuit redresseur ;

    le calcul (70) d'une seconde tension d'erreur comme différence entre la seconde tension de sortie et la tension de redresseur cible ;

    la détermination (72) que la seconde tension d'erreur est ou non inférieure à la première tension d'erreur ;

    et s'il est déterminé que la seconde tension d'erreur n'est pas inférieure à la première tension d'erreur :

    la modification (76) de la première quantité définie en une seconde quantité définie, la seconde quantité étant le double de la première quantité définie et de signe opposé à celle-ci ; et

    la modification de l'impédance de l'élément d'impédance réglable par la seconde quantité définie.


     
    2. Procédé (50) selon la revendication 1, dans lequel la modification de l'impédance de l'élément d'impédance réglable comprend en outre la modification d'une tension de syntonisation provenant d'un convertisseur numérique-analogique fournie à l'élément d'impédance réglable sur la base de la première tension d'erreur.
     
    3. Procédé (50) selon la revendication 1 ou 2, dans lequel la mesure de la première tension de sortie comprend en outre la fourniture de la première tension de sortie à un convertisseur analogique-numérique.
     
    4. Procédé (50) selon n'importe quelle revendication précédente, dans lequel si la première tension de sortie est comprise entre les limites supérieure et inférieure, il est déterminé qu'une impédance du réseau d'impédance de résonance d'antenne est adaptée à une impédance de l'émetteur de charge sans fil.
     
    5. Procédé (50) selon n'importe quelle revendication précédente, comprenant en outre le réglage d'une pluralité de bits sur la base de la première tension d'erreur, la pluralité de bits étant fournie à un convertisseur numérique-analogique, le convertisseur numérique-analogique étant couplé à l'élément d'impédance réglable.
     
    6. Procédé (50) selon n'importe quelle revendication précédente, dans lequel la mesure de la première tension de sortie du redresseur de tensions comprend en outre la mesure d'une tension de sortie d'un redresseur pont MOSFET.
     
    7. Procédé (50) selon l'une quelconque des revendications 1, 3, 4 ou 6, dans lequel la modification de l'impédance de l'élément d'impédance réglable comprend en outre la modification d'une tension de syntonisation provenant d'un convertisseur numérique-analogique fournie à l'élément d'impédance réglable au moyen d'un contrôleur hôte.
     
    8. Procédé (50) selon n'importe quelle revendication précédente, dans lequel la détermination de la première tension d'erreur sur la base de la première tension de sortie et de la tension de sortie cible comprend en outre la détermination de la première tension d'erreur sur la base d'une grandeur de la différence entre la première tension de sortie et la tension de sortie cible.
     
    9. Récepteur de charge sans fil (14) comprenant :

    une antenne (15) ;

    un réseau d'impédance de résonance d'antenne (16) présentant une entrée couplée à l'antenne, et une sortie, le réseau d'impédance de résonance d'antenne présentant un circuit d'adaptation d'impédance (20) comprenant un élément d'impédance réglable (26) ;

    un circuit redresseur (22) présentant une entrée couplée à la sortie du circuit d'adaptation d'impédance, et une sortie pour fournir une tension de sortie de redresseur ;

    et un circuit de commande (18) comprenant

    un convertisseur analogique-numérique (42) présentant une entrée couplée pour recevoir la tension de sortie de redresseur, et une sortie ;

    une logique de commande (44) présentant une entrée couplée à la sortie du convertisseur analogique-numérique, et une sortie ; et

    un convertisseur numérique-analogique (46) présentant une entrée couplée à la sortie de la logique de commande, et une sortie couplée pour fournir une tension de syntonisation à l'élément d'impédance réglable ; dans lequel

    le récepteur de charge sans fil est configuré pour :

    stocker une tension de redresseur cible ;

    mesurer une première tension de sortie du circuit redresseur;

    déterminer que la première tension de sortie du circuit redresseur est comprise ou non en-deçà d'une limite supérieure et d'une limite inférieure ;

    si la première tension de sortie n'est pas comprise en-deçà des limites supérieure et inférieure :

    calculer une première tension d'erreur comme différence entre la première tension de sortie et la tension de redresseur cible ;

    modifier l'impédance de l'élément d'impédance réglable par une première quantité définie ;

    mesurer une seconde tension de sortie du circuit redresseur;

    calculer une seconde tension d'erreur comme différence entre la seconde tension de sortie et la tension de redresseur cible ;

    déterminer que la seconde tension d'erreur est inférieure ou non à la première tension d'erreur ;

    et s'il est déterminé que la seconde tension d'erreur n'est pas inférieure à la première tension d'erreur :

    modifier la première quantité définie en une seconde quantité définie, dans lequel la seconde quantité définie est le double de la première quantité définie et de signe opposé à celle-ci ; et

    modifier l'impédance de l'élément d'impédance réglable par la seconde quantité définie.


     
    10. Récepteur de charge sans fil (14) selon la revendication 9, dans lequel l'élément d'impédance réglable (26) est un condensateur variable.
     
    11. Récepteur de charge sans fil selon la revendication 9 ou 10, dans lequel le circuit d'adaptation d'impédance (20) comprend :

    un premier condensateur (30) présentant une première borne couplée à une première borne de l'antenne (15), et une seconde borne ;

    un deuxième condensateur (28) présentant une première borne couplée à une seconde borne de l'antenne, et une seconde borne ;

    un troisième condensateur (32) présentant une première borne couplée à la seconde borne du premier condensateur, et une seconde borne couplée à la seconde borne du deuxième condensateur ; dans lequel

    l'élément d'impédance réglable (26) présente une première borne couplée à la première borne de l'antenne, une deuxième borne couplée à la seconde borne de l'antenne, et une borne de commande couplée à la sortie du convertisseur numérique-analogique (46).


     
    12. Récepteur de charge sans fil (14) selon l'une quelconque des revendications 9 à 11, dans lequel le circuit redresseur (22) est un redresseur pont MOSFET.
     
    13. Récepteur de charge sans fil (14) selon l'une quelconque des revendications 9 à 12, comprenant en outre un contrôleur hôte (48) couplé à la logique de commande (44) .
     




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    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description