Hardware and methods for enhancing wireless receiver output power

Abstract

Embodiments of the present disclosure relate to hardware and methods for enhancing wireless receiver output power. A power transmission system includes at least one wireless power transmission circuit. A first wireless power receiving circuit includes a first circuit that compares a reference voltage with a feedback voltage representing an output voltage generated from received power and delivered to an output node, and adjusts a first control terminal of a device that supplies a first rectified voltage until the feedback voltage and the reference voltage are equal. A second wireless power receiving circuit includes a second circuit that modifies a control terminal of a device that sources a second rectified current to the output node based on a comparison of a reference current with a current representing a second rectified current generated from the received power. The control circuitry adjusts the reference current until the first rectified voltage generated by the first wireless power receiving circuit and the second rectified voltage generated by the second wireless power receiving circuit are equal.

Description

Technical Field

[0001] The present disclosure relates to the field of wireless power transfer, and in particular to hardware, operating techniques, and methods for increasing the amount of power transferable via wireless power transfer in a given unit of time. Background Art

[0002] Portable electronic devices such as smartphones, smartwatches, audio output devices (earbuds, headphones), and wearable devices rely on batteries for power rather than wired power delivered to them via wired transmission lines and distribution systems. Batteries used in such devices are typically rechargeable, and therefore a method for charging such batteries is needed.

[0003] Most portable electronic devices include a charging port, which typically conforms to the Micro USB or USB-C standard, into which a power cord connected to a power source can be plugged to charge its battery. However, such charging ports may make it difficult to improve the water resistance of the electronic device and are easily damaged by repeated use. In addition, some smaller portable electronic devices (e.g., earbuds and smartwatches) lack available space for a charging port. In addition, some users may find it cumbersome to plug a power cord into the charging port of an electronic device to charge the battery of the device.

[0004] Therefore, to address these issues, wireless power transfer has been developed. Wireless power transfer systems utilize a coil transmitter (primary) and a coil receiver (secondary). The coil transmitter is driven by power from a power source (usually a wired connection, but in some cases a battery). The coil transmitter generates a time-varying electric field that induces a current in the coil receiver. The receiver hardware extracts the power transferred to the coil receiver and provides it to a load, such as a battery in an electronic device that incorporates the coil receiver and receiver hardware.

[0005] Standards governing the hardware and how transmitters and receivers communicate have been developed to allow for easy implementation of wireless charging in electronic devices. However, existing wireless transmission standards can only deliver a limited amount of power, which can be insufficient or undesirable in certain situations where it is desirable to transmit an increased amount of power per unit time. Therefore, despite the existence of well-established and well-functioning wireless transmission standards, further development is still needed in this area. Summary of the Invention

[0006] Disclosed herein is a wireless power transmission system comprising at least one wireless power transmission circuit, a first wireless power receiving circuit, a second wireless power receiving circuit, and a control circuit system. Note that the first wireless power receiving circuit is a master, while the second wireless power receiving circuit is a slave, and there can be multiple slaves. However, for the sake of brevity, only one second wireless power receiving circuit (slave) is described in this summary.

[0007] The first wireless power receiving circuit has a first amplifier circuit configured to compare a reference voltage with a feedback voltage representing an output node voltage generated based on power received from at least one wireless power transmitting circuit, and to regulate a first transistor supplying a first rectified voltage until the feedback voltage is equal to the reference voltage, wherein a first rectified current is delivered to the output node.

[0008] The second wireless power receiving circuit has a second amplifier circuit configured to modify a gate bias of a second transistor that sources a second rectified current based on a comparison of a reference current and a current representing a second rectified current generated based on power received from at least one wireless power transmitting circuit, thereby modifying the second rectified current, wherein the second rectified current is delivered to an output node.

[0009] The control circuitry is configured to adjust the reference current until a first rectified voltage generated by the first wireless power receiving circuit and a second rectified voltage generated by the second wireless power receiving circuit are equal.

[0010] The first wireless power receiving circuit may further include a first capacitor across which the first rectified voltage is developed, and the second wireless power receiving circuit may further include a second capacitor across which the second rectified voltage is developed.

[0011] The first amplifier circuit may further include a first n-channel transistor having a drain coupled to receive the first rectified voltage, a source coupled to the output node, and a gate. The first amplifier circuit may further include a voltage divider coupled between the output node and ground, and the first amplifier circuit may further include a first amplifier having a non-inverting terminal coupled to a reference voltage, an inverting terminal coupled to a tap of the voltage divider to receive a feedback voltage, and an output coupled to the gate of the first n-channel transistor.

[0012] The second amplifier circuit may include a second n-channel transistor having a drain coupled to the second rectified voltage, a source coupled to the output node, and a gate. The second amplifier circuit may also include a second amplifier having a non-inverting terminal coupled to receive a current representing the second rectified current, an inverting terminal coupled to receive a reference current, and an output coupled to the gate of the second n-channel transistor.

[0013] When the control circuitry is unable to regulate the reference current, the equalizer switch controlled by the control circuitry may selectively couple the first rectified voltage to the second rectified voltage until the feedback voltage equals the reference voltage and the current representing the second rectified current equals the reference current.

[0014] The first amplifier may be a low dropout amplifier.

[0015] The control circuit system may adjust the reference current until the first rectified voltage and the second rectified voltage are equal by: requesting the at least one power transmission circuit to transmit a portion of the power it is capable of transmitting to the first wireless power receiving circuit; and adjusting the reference current until a first equilibrium point is reached where the first rectified voltage and the second rectified voltage are equal. The reference current may be adjusted until the first equilibrium point is reached by: requesting the at least one power transmission circuit to increase the portion of the power it transmits to the first wireless power receiving circuit if the first rectified voltage is greater than the output voltage at the output node and if the output voltage is greater than the second rectified voltage; increasing the magnitude of the reference current if the second rectified voltage is greater than the first rectified voltage and the first rectified voltage is greater than the output voltage; and decreasing the magnitude of the reference current if the first rectified voltage is greater than the second rectified voltage and the second rectified voltage is greater than the output voltage.

[0016] The control circuit system can further adjust the reference current until the first rectified voltage and the second rectified voltage are equal by: requesting at least one power transmission circuit to transmit a portion of the power it is capable of transmitting to the second wireless power receiving circuit; and adjusting the reference current until a second equilibrium point where the first rectified voltage and the second rectified voltage are equal.

[0017] The reference current can be adjusted until a second equilibrium point is reached by increasing the magnitude of the reference current if the second rectified voltage is greater than the first rectified voltage and the first rectified voltage is greater than the output voltage; and decreasing the magnitude of the reference current if the first rectified voltage is greater than the second rectified voltage and the second rectified voltage is greater than the output voltage.

[0018] The control circuitry may further adjust the reference current until the first rectified voltage and the second rectified voltage are equal by requesting at least one power transmission circuit to transmit all of its transmittable power to the first wireless power receiving circuit and the second wireless power receiving circuit; and adjusting the reference current until a third equilibrium point is reached where the first rectified voltage and the second rectified voltage are equal. The reference current may be adjusted until the third equilibrium point is reached by increasing the reference current if the second rectified voltage is greater than the first rectified voltage and the first rectified voltage is greater than the output voltage; and decreasing the reference current if the first rectified voltage is greater than the second rectified voltage and the second rectified voltage is greater than the output voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of a first wireless power transfer system disclosed herein, wherein two transmitters transfer power to two receivers operating in parallel;

[0020] Figure 2A It shows Figure 1 A flowchart of the operation of the wireless power transmission system;

[0021] Figure 2B It shows Figure 2A Flowchart of details of step 115;

[0022] Figure 2C It shows Figure 2A A flowchart of the details of step 124;

[0023] Figure 2D is shown for execution Figure 2A A flowchart of the details of a technique for step 102;

[0024] Figure 2E is shown for execution Figure 2A A flowchart of another technical detail of step 102;

[0025] Figure 3 is a schematic diagram of a second wireless power transfer system disclosed herein, in which a single transmitter transfers power to two receivers operating in parallel. DETAILED DESCRIPTION

[0026] The following disclosure enables those skilled in the art to make and use the subject matter disclosed herein. The general principles described herein may be applied to embodiments and applications other than those described in detail above without departing from the spirit and scope of the present disclosure. The present disclosure is not intended to be limited to the embodiments shown, but rather to the widest scope consistent with the principles and features disclosed or suggested herein.

[0027] Now refer to Figure 1An embodiment of a wireless transmission system 1 is described in which a first transmitter 5 and a second transmitter 7 wirelessly transmit power to a first receiver 6 and a second receiver 8 respectively operating in parallel. First, the hardware itself will be described, and then the operation of the hardware will be described.

[0028] A. Hardware of Wireless Power Transfer System 1

[0029] The transmitter 5 comprises an AC power source 14 connected to a primary coil (schematically represented by a capacitor Cp1 in series with an inductor Lp1 and a resistor Rp1).

[0030] Receiver 6 includes a secondary coil (schematically represented by a capacitor Cs1 in series with an inductor Ls1 and a resistor Rs1) connected to a rectifier 11. The rectifier 11 rectifies the AC current Is output by the secondary coil to produce a DC output current I1. The input of the rectifier 11 is connected to the secondary coil, and the output of the rectifier 11 is coupled between a node N1 and ground.

[0031] Current sensor 16 is coupled between nodes N1 and N2 and is configured to sense current I1 output by rectifier 11. Current sensor 16 includes a resistor R1 coupled between nodes N1 and N2, and an amplifier 12. Amplifier 12 has a non-inverting terminal coupled to node N1 and an inverting terminal coupled to node N2. The output of amplifier 12 is a first sensed current I1_s, which represents current I1 output by rectifier 11. The output of amplifier 12 is selectively connected to the inverting terminal of amplifier 13 via a switch S2 controlled by a mode signal Mode.

[0032] The drain of the n-channel MOSFET transistor T1 is connected to the node N2, the source thereof is connected to the node N3, and the gate thereof is connected to be biased by the output of the amplifier 13. The non-inverting terminal of the amplifier 13 is selectively connected to the reference voltage Vref or the reference current Iref via the switch S4 controlled by the mode signal Mode, and the inverting terminal of the amplifier 13 is selectively connected to the node N4 through the switch S3 controlled by the Mode signal.

[0033] Resistor R2 is connected between nodes N3 and N4, and resistor R3 is connected between node N4 and ground. Load 15 (e.g., a battery of an electronic device in which receivers 6 and 8 are incorporated) is connected between node N3 and ground. Capacitor C1 is connected between node N2 and ground, and a first rectified voltage Vrect1 is formed across capacitor C1.

[0034] Note that switches S2, S3, and S4 in receiver 6 all operate based on mode signal Mode, but in different ways. When mode signal Mode indicates that receiver 6 is to operate in an output voltage control mode (hereinafter referred to as voltage feedback), mode signal Mode is used to open switch S2, close switch S3 to receive feedback voltage Vfbk1 from node N4, and set switch S4 to connect the non-inverting terminal of amplifier 13 to reference voltage Vref. On the other hand, when mode signal Mode indicates that receiver 6 is to operate in an output current control mode (hereinafter referred to as current feedback), mode signal Mode is used to close switch S2, open switch S3, and set switch S4 to connect the non-inverting terminal of amplifier 13 to reference current Iref.

[0035] The transmitter 7 further comprises an AC power source 24 connected to the primary coil (schematically represented by a capacitor Cp2 in series with an inductor Lp2 and a resistor Rp2).

[0036] Receiver 8 also includes a secondary coil connected to a rectifier 21 (schematically represented by a capacitor Cs2 in series with an inductor Ls2 and a resistor Rs2). Rectifier 21 rectifies the AC current Is output by the secondary coil to produce a DC output current I2. The input of rectifier 21 is connected to the secondary coil, and the output of rectifier 21 is coupled between node N5 and ground.

[0037] Current sensor 17 is coupled between nodes N5 and N6 and is configured to sense current I2 output by rectifier 21. Current sensor 17 includes a resistor R4 coupled between nodes N5 and N6, and an amplifier 22. Amplifier 22 has a non-inverting terminal coupled to node N5 and an inverting terminal coupled to node N6. The output of amplifier 22 is a second sense current I2_s, which represents current I2 output by rectifier 21. The output of amplifier 22 is selectively connected to the inverting terminal of amplifier 23 via a switch S7 controlled by a mode signal Mode.

[0038] N-channel transistor T2 has its drain connected to node N6, its source connected to node N3, and its gate connected to be biased by the output of amplifier 23. Note that instead of n-channel transistor T2, any three-terminal device or combination of devices may be used.

[0039] The resistor R5 is connected between the nodes N3 and N8 , and the resistor R6 is connected between the node N8 and the ground.

[0040] The non-inverting terminal of the amplifier 23 is selectively connected to the reference current Iref via the switch S9 controlled by the mode signal Mode, and the inverting terminal of the amplifier 23 is connected through the switch S7 controlled by the mode signal Mode to selectively receive the current I2_s from the output of the amplifier 22, or is selectively connected through the switch S8 controlled by the mode signal Mode to receive the feedback voltage Vfbk2 from the node N8.

[0041] The capacitor C2 is connected between the node N6 and the ground, and a second rectified voltage Vrect2 is developed across the capacitor C2 .

[0042] Note that switches S7, S8, and S9 in receiver 8 all operate based on mode signal Mode, but in different ways. When mode signal Mode indicates that receiver 8 is to operate based on voltage feedback, mode signal Mode is used to open switch S7, close switch S8, and set switch S9 to connect the non-inverting terminal of amplifier 23 to reference voltage Vref. On the other hand, when mode signal Mode indicates that receiver 8 is to operate based on current feedback, mode signal Mode is used to close switch S7, open switch S8, and set switch S9 to connect the non-inverting terminal of amplifier 23 to reference current Iref.

[0043] Those skilled in the art will note that, in voltage feedback, elements 13, T1, R2, R3, S2, S3, S4 (and their corresponding counterparts 23, T2, R5, R6, S7, S8, S9) form a conventional voltage regulator configuration, represented here using n-channel MOSFETs. However, this functionality can also be implemented using a conventional p-channel LDO structure. The drain of p-channel transistor T1 is connected to node N3, its source is connected to node N2, and its gate is connected to be biased by the output of amplifier 13, the positive and negative inputs of amplifier 13 being swapped. The p-channel transistor structure will also accommodate current feedback functionality. And more generally, any receiver configured to be configurable between a voltage control mode (conceptually a voltage source) and an output current control mode (conceptually a current source) can be used to implement the disclosure herein.

[0044] A switch S1 operated by a control signal Eq is connected between nodes N2 and N6. When the switch S1 is closed, Vrect1 and Vrect2 are equal.

[0045] The control unit 31 receives a reference voltage Vref, an output voltage Vout, a first rectified voltage Vrect1 , a second rectified voltage Vrect2 , a first rectified current I1_s, and a second rectified current I2_s, and thereby generates a reference current Iref and a control signal Eq for the switch S1 .

[0046] The control unit 32 receives a reference voltage Vref, a first rectified voltage Vrect1 , a second rectified voltage Vrect2 , a first rectified current I1_s, and a second rectified current I2_s, and thereby generates a reference current Iref and a control signal Eq for the switch S1 .

[0047] Note that only one control unit 31 or 32 may be present, or both control units 31 and 32 may be present. When both control units 31 and 32 are present, each is associated with one of the receivers 6 or 8. As will be explained below, one receiver 6 or 8 operates as a master, while the other receiver 8 or 6 operates as a slave. In the case where both control units 31 and 32 are present, the control unit 31 or 32 associated with the receiver 6 or 8 designated as the master is operational, while the other control unit is idle.

[0048] The master control unit (non-idle) is responsible for directly controlling the Vref of the master and the Iref of the slave and requests power up / down of both transmitters.

[0049] In the case of in-band communication, even if the control unit is idle as a slave, the master control unit can still request it to wake up and communicate with the associated transmitter (e.g., ASK modulation in the Qi standard) to adjust the power, simply because the master control unit does not have access to the physical communication link to the transmitter. This may not apply to the case of out-of-band communication.

[0050] B. Operation of Wireless Power Transmission System 1

[0051] 1. Operation Overview

[0052] In operation, one of the receivers 6 or 8 operates as a "master" in a voltage-mode feedback loop, while the other receiver operates as a "slave" in a current-mode feedback loop. Figure 1 As shown, receiver 6 operates as a master, while receiver 8 operates as a slave. In particular, receiver 6 (operating as a master) sets and controls the rectified output voltage Vout (conceptually as a voltage source would do), while receiver 8 (operating as a slave) increases the power delivered at that output voltage Vout (conceptually as a current source would do).

[0053] In more detail, amplifier 13, transistor T1, and resistors R2 and R3 form a voltage regulator. Amplifier 13 compares reference voltage Vref with feedback voltage Vfbk1 at node N4 and modulates the bias voltage applied to the gate of n-channel transistor T1 so that feedback voltage Vfbk1 equals Vref. This has the effect of modulating current I1 supplied by transistor T1 to the load, thereby maintaining output voltage Vout at a set, stable voltage.

[0054] By adding current I2 to the output current I1 of receiver 6 without changing the voltage Vout, receiver 8 operates as a "slave" in a current mode loop. The parameters of this system are linked together by the following relationship:

[0055] Vout=Vref and I1=Vout / Rload-Iref.

[0056] The control unit 31 monitors Vrect1 and Vrect2 and adjusts Iref so that the second rectified voltage Vrect2 matches the first rectified voltage Vrect1 when the amplifier 23 modulates the bias voltage on the gate of the n-channel transistor T2 to keep the current I2_s equal to the reference current Iref. When Vrect1 and Vrect2 match, I1 and I2 are controlled by I2 = Iref and I1 = Vout / Rload-Iref, where k1 (and correspondingly k2) represents the power transfer factor from TX1 to RX1 (and correspondingly TX2 to RX2), and α represents the ratio between the amount of power P2 provided by TX2 and the amount of power P1 provided by TX1, such that P2 = α.P0 and P1 = P0. In order for the system to reach the equilibrium point (Vrect1 = Vrect2), the total incoming power P1 + P2 = (1 + α)P0 should be sufficient so that Vout can reach Vref while delivering Vref2 / Rload. In the event of insufficient incoming power, the system will change the parameters Iref and Vref to conform to the relationship between these two parameters. It should be emphasized that in the case of k1 = k2 and α = 1, Iref = 2x I1 = 2x I2 = Vout / (2.R1).

[0057] Receivers 6 and 8 each facilitate providing power to load 15 at an output voltage Vout, effectively increasing the power provided to load 15 in the event that only one of receivers 6 or 8 is operational.

[0058] If it is not possible under given operating conditions (for example, but not limited to, when the incoming power is too low) to sufficiently regulate Iref for a given Vref so that Vrect2 is substantially equal to Vrect1, the control unit 31 may assert the equalization signal Eq to close the switch S1 to short-circuit the nodes N2 and N6, resulting in Vout possibly being away from the target and some current possibly flowing from Vrect1 to Vrect2 (or vice versa) through S1.

[0059] The current flowing from one of the two Vrect voltages (Vrect1, Vrect2) to the other can be read by a current sensor, and these two and the Vout information (captured by the Vout voltage measurement) can be used by the system to understand which parameters to use to achieve stable operation. Ultimately, stable operation is governed by the following equation:

[0060]

[0061] When P0, Iref, and Vref are set correctly, this results in zero current flowing through switch S1 and the system is able to de-balance.

[0062] If receiver 8 is instead configured as a master, the operations performed by receiver 6 are instead performed by receiver 8 , and if receiver 6 is instead configured as a slave, the operations performed by receiver 8 are instead performed by receiver 6 .

[0063] 2. Detailed description of the operation

[0064] Now refer to Figures 2A-2B The flowchart is used to describe the operation of the wireless power transmission system 1 in more detail. Figures 2A-2B One potential operating technique for the wireless power transfer system 1 is shown, and it should be understood that other operating techniques may also be used. To begin wireless power transfer, receivers 6 and 8 are placed in position to receive power from transmitters 5 and 7 (block 101). For example, if receivers 6 and 8 are within a smartphone and transmitters 5 and 7 are within a wireless charging pad, the smartphone would be placed on the wireless charging pad.

[0065] Then, a master / slave assignment operation is performed (block 102). Figure 1 In the example shown, receiver 6 is configured as a master and receiver 8 is configured as a slave. Details regarding this master / slave assignment (block 102) will be given below.

[0066] Next, transmitters 5 and 7 ping receivers 6 and 8 (block 103), causing receivers 6 and 8 to wake up, control unit 31 to set reference current Iref to a set initial value, and hardware within the electronic device comprising system 1 to set reference voltage Vref to a set initial value (block 104). Controller 31 then sends a power request to transmitter 5 via receiver 6 using in-band or out-of-band data communication, and load 15 is connected to node N3 (block 105).

[0067] Thereafter, a first feedback loop process (block 106) is executed to find a first equilibrium point, in which the output voltage Vout is approximately equal to the reference voltage Vref, the current I2 is approximately equal to the reference current Iref (which is set to approximately zero), the current I1 is approximately equal to the output voltage Vout divided by the impedance of the load 15, the power delivered by the second transmitter 7 to the second receiver 8 is approximately equal to Vout*I2, the power delivered by the first transmitter 5 to the first receiver 6 is approximately equal to Vout*I1, the current flowing into the load is equal to I1+I2, I1 provides the majority of the load current, and I2 remains approximately zero. The goal of the first feedback loop process is to achieve a Vout=Vref output voltage for transmitter 5 and deliver approximately 50% of its capable power to receiver 6, while transmitter 7 delivers a small amount of power to bias receiver 8, and Vrect2 is effectively balanced with Vrect1. In other words, when loop 106 is exited, receiver 8 receives only enough power to be energized and powered without contributing to the load current, while receiver 6 does provide 50% of its capable power to the load.

[0068] The first feedback loop begins with controller 31 reading rectified voltages Vrect1 and Vrect2, and reading output voltage Vout. If Vrect1 is greater than Vout and Vout is greater than Vrect2, controller 31 requests power transfer from transmitter 7 to receiver 8 by transmitting a request from receiver 8 to transmitter 7 (block 108), considering that increasing Vrect2 as incoming power to receiver 8 will at some point exceed the receiver's requirements, which are set to a low Iref value. After transmitter 7 power is increased, when the first feedback loop restarts, the system will proceed to block 112 or even block 110. On the other hand, if Vrect2 is greater than Vrect1 and Vrect1 is greater than Vout (block 110), controller 31 increases Iref to change the operation of amplifier 23, causing n-channel transistor T2 to increase I2, resulting in a decrease in Vrect2 (block 111), and the feedback loop restarts. Conversely, if Vrect1 is greater than Vrect2 and Vrect2 is greater than Vout (block 112), the controller 31 decreases Iref to change the operation of the amplifier 23 so that the n-channel transistor T2 decreases I2, causing Vrect2 to increase (block 113), and the first feedback loop restarts. Once Vrect1 is equal to Vrect2 and greater than Vout (block 109), the first equilibrium point is reached and the first feedback loop process is complete (block 114).

[0069] After reaching the first equilibrium point, controller 31 (acting as the master) requests additional power to be transferred from transmitter 7 to receiver 8. In the case of in-band communication, controller 31 may not have the ability to control the receiver 8 hardware communication channel to its associated transmitter 6. Therefore, controller 31 can instruct controller 32 to wake up and do so. Controller 31 accordingly ramps up reference current Iref (block 115) to increase the power delivered to load 15. This ramp-up (block 115) will be described in more detail below. After the ramp-up, the second feedback loop process begins (block 116).

[0070] A second feedback loop is executed to find a second equilibrium point in which the output voltage Vout is approximately equal to the reference voltage Vref, the current I2 is approximately equal to the reference current Iref, the current I1 is approximately equal to the output voltage Vout divided by the load impedance Zload, where the current I2 is subtracted from the result, the power delivered by the second transmitter 7 to the second receiver 8 is approximately equal to Vout*I2, and the power delivered by the first transmitter 5 to the first receiver 6 is approximately equal to Vout*I1 (block 122). The goal of the second feedback loop process is for transmitters 5 and 7 to deliver approximately 50% of the power they are capable of delivering to receivers 6 and 8, respectively.

[0071] The second feedback loop begins when controller 31 reads rectified voltages Vrect1 and Vrect2 and reads output voltage Vout. If Vrect2 is greater than Vrect1 and Vrect1 is greater than Vout (block 117), controller 31 increases Iref to change the operation of amplifier 23, causing n-channel transistor T2 to increase I2, resulting in a decrease in Vrect2 (block 118), and the second feedback loop restarts. Conversely, if Vrect1 is greater than Vrect2 and Vrect2 is greater than Vout (block 120), controller 31 decreases Iref to change the operation of amplifier 23, causing n-channel transistor T2 to decrease I2, resulting in an increase in Vrect2 (block 121), and the second feedback loop restarts. Once Vrect1 equals Vrect2 and is greater than Vout (block 119), the second equilibrium point has been reached and the second feedback loop process is complete (block 122).

[0072] After reaching the second equilibrium point, the controller 31 evaluates the value k1, which is calculated as the power delivered to the receiver 6 divided by the power transmitted by the transmitter 5, and the value k2, which is calculated as the power delivered to the receiver 8 divided by the power transmitted by the transmitter 7 (block 123). These values ​​of k1 and k2 may be stored and used in step 102 (the next time the system 1 is used) to determine the master / slave assignment—the receiver 6 or 8 with the higher value of k may be set as the master in step 102.

[0073] Thereafter, controller 31 can instruct controller 32 to request additional power from transmitter 7 to receiver 8. In the case of out-of-band communication, it can also send a power request directly to either transmitter. Controller 31 accordingly ramps up reference current Iref (block 124). This ramp-up will be described in detail below (block 124) and is intended to cause transmitters 5 and 7 to deliver 100% of their capable power to receivers 6 and 8. After the ramp-up, a third equilibrium point is reached, at which the output voltage Vout is approximately equal to the reference voltage Vref, the current I2 is approximately equal to the reference current Iref, and the current I1 is approximately equal to the output voltage Vout divided by the load impedance Zload, with current I2 subtracted from the result. The power delivered by second transmitter 7 to second receiver 8 is approximately equal to Vout*I2, and the power delivered by first transmitter 5 to first receiver 6 is approximately equal to Vout*I1 (block 125). Thereafter, transmitters 5 and 7 each deliver 100% of their capable power to receivers 6 and 8, and no further adjustments are required. Power transfer continues until the battery in the electronic device is fully charged, or until the receivers 6 and 8 are no longer in proximity to the transmitters 5 and 7, for example by removing the electronic device from a charging pad.

[0074] It will be appreciated that in some cases, currents I1 and I2 may not balance, and thus transmitters 5 and 7 may not each achieve 100% of their potential power output, and receivers 6 and 8 may not each deliver 100% of their potential power to load 115. However, the feedback loop described above will still serve to balance the rectified voltages Vrect1 and Vrect2, thereby allowing each transmitter 5 and 7 to provide a different amount of power.

[0075] 3. Detailed description of step 115

[0076] Step 115 involves three events that will occur simultaneously. The load demand is adjusted to a higher value, while the transmitter provides the additional required power, and the control unit adjusts Iref to help ensure a smooth transition. This involves three independent hardware and time constant terms, and without proper synchronization between demand, supply, and balance, it can cause Vrect to increase or decrease excessively. Step 115 divides this process into two phases. In the first case, power demand and Iref adjustments (supply and balance) are performed while the dummy load is connected (steps 115a, 115b, 115c), which now allows two pieces of hardware (i.e., transmitter and receiver) to be handled simultaneously and makes sequencing easier to manage because the dummy load is part of the receiver, which is also the device issuing instructions to the transmitter. Once the system is stable in the first case, in the second case (step 115d), the dummy load is disconnected and the actual load demand is set, which again allows two pieces of hardware (i.e., receiver and its load, which can be the host in the case of a battery charger, for example) to be handled at once.

[0077] Now we will refer to Figure 2B The controller 31 further describes a power request (block 115) for the transmitter 7 to send 50% of the power it can deliver to the receiver 8. First, a dummy load is connected to the receiver 8, and the controller 31 increases the reference current Iref to match the current through the dummy load (block 115a).

[0078] Controller 31 then requests (or, in the case of in-band communication, instructs controller 32 to do so) that second transmitter 7 deliver additional power to second receiver 8. Specifically, controller 31 requests that second transmitter deliver up to 50% of the power it is capable of delivering to receiver 8 (block 115b). Controller 31 then reads rectified voltages Vrect1 and Vrect2, as well as output voltage Vout (block 115c). If Vrect1 is greater than Vrect2 (at block 115c-1, which occurs if controller 31 requests less than 50% power from second transmitter 7), controller 31 again requests additional power from second transmitter 7 (block 115b). Once Vrect1 equals Vrect2 and is greater than Vout (block 115c-2), controller 31 disconnects the dummy load after ensuring that the actual load requests the same amount of power (e.g., via I2C to the receiver hosting the transaction), resulting in load 15 actually requesting additional current (block 115d).

[0079] 4. Detailed description of step 124

[0080] Now we will refer to Figure 2CThe following describes a power request by controller 31 for transmitters 5 and 7 to increase the power they deliver to receivers 6 and 8 (block 124). First, as described above, controller 31 requests transmitters 5 and 7 (either directly through out-of-band communication or via controller 32) to increase the power they deliver to receivers 6 and 8 by 100%, so that they are delivering the maximum power they are capable of providing (block 124a). Consequently, the power delivered by transmitter 5 is increased by 100%, the power delivered by transmitter 7 is increased by 100%, and current I2 is correspondingly increased by 100% (block 124b). Thereafter, a third feedback loop process is executed (block 124c).

[0081] A third feedback loop is executed to find a third equilibrium point in which the output voltage Vout is approximately equal to the reference voltage Vref, the current I2 is approximately equal to the reference current Iref, the current I1 is approximately equal to the output voltage Vout divided by the load impedance Zload, with the current I2 subtracted from the result, the power delivered by the second transmitter 7 to the second receiver 8 is approximately equal to Vout*I2, and the power delivered by the first transmitter 5 to the first receiver 6 is approximately equal to Vout*I1 (block 124c). The goal of the third feedback loop process is for transmitters 5 and 7 to deliver 100% of the power they are capable of delivering to receivers 6 and 8, respectively.

[0082] The third feedback loop begins when controller 31 reads rectified voltages Vrect1 and Vrect2 and reads output voltage Vout. If Vrect2 is greater than Vrect1 and Vrect1 is greater than Vout (block 124c-1), controller 31 increases Iref to change the operation of amplifier 23, causing n-channel transistor T2 to increase I2, resulting in a decrease in Vrect2 (block 124c-2), and the third feedback loop restarts. Conversely, if Vrect1 is greater than Vrect2 and Vrect2 is greater than Vout (block 124c-3), controller 31 decreases Iref to change the operation of amplifier 23, causing n-channel transistor T2 to decrease I2, resulting in an increase in Vrect2 (block 124c-4), and the third feedback loop restarts. Once Vrect1 equals Vrect2 and is greater than Vout (block 125c-5), the third equilibrium point has been reached and the third feedback loop process is complete (block 133).

[0083] 5. Detailed description of step 102

[0084] Now refer to Figure 2DThe master / slave assignment operation (block 102) is described in detail. Initially, transmitters 5 and 7 ping receivers 6 and 8 (block 102a), and receivers 6 and 8 wake up in turn and identify themselves to the controller 31 (block 102b). Initially, the first receiver 5 starts up as a master, with the reference voltage Vref set to an initial startup value, and the second receiver 7 starts up as a slave, with the reference current Iref set to an initial startup value. When the load 15 is not yet connected to the node N3 and the controller reads the rectified voltage Vrect1 (block 102c) and stores the value of Vrect1, the controller 31 requests power transfer from the transmitter 5 to the receiver 6. When the receiver 6 is set up as the master, it has the following information: Figure 1 When the receiver 8 is set as a slave, it has the following electrical components and connections: Figure 1 Electrical components and connections shown.

[0085] Next, the receiver 8 is switched to the master and the receiver 6 is switched to the slave, and then the receivers 6 and 8 are turned off (block 102d). Note that by setting the receiver 8 as the master, the receiver 8 has the same Figure 1 The same electrical components and connections as the receiver 6 shown, and by setting the receiver 6 as a slave, the receiver 6 has the same Figure 1 The receiver 8 shown has the same electrical components and connections.

[0086] Now, transmitters 5 and 7 ping receivers 6 and 8 again (block 102e), Vref and Iref are reinitialized to their initial startup values, load 15 is still not connected to node N3, controller 31 requests power transfer from transmitter 7 to receiver 8, and controller 31 reads the rectified voltage Vrect2 (block 102f) and stores the value of Vrect2. Finally, controller 31 determines which receiver 6 or 8 will be the master and which will be the slave based on whether Vrect1 or Vrect2 is higher (block 102g). Note that the control turns the receivers on and off as the master / slave evaluation proceeds. Therefore, in order to be able to track the master / slave assignment, the receivers should have embedded NVM capabilities or use host memory capabilities to store and retrieve information.

[0087] Now refer to Figure 2E An alternative technique for master / slave assignment operation (block 102) is described in detail. Initially, transmitters 5 and 7 ping receivers 6 and 8 (block 102a'), and receivers 6 and 8 wake up and identify themselves to controller 31 in turn (block 102b'). Here, receivers 6 and 8 are initially both started in a slave configuration (e.g., both have Figure 18 shown), the load 15 is not connected to node N3, and the controller 31 requests power transfer from the transmitters 5 and 7 to the receivers 6 and 8 while reading Vrect1 and Vrect2 and storing their values ​​(block 102c').

[0088] After this, receiver 8 switches to the master and receiver 7 switches to the slave, and the controller 31 requests power transfer from transmitters 5 and 7 to receivers 6 and 8 while reading Vrect1 and storing its value (block 102d'). Receivers 6 and 8 are then turned off. Controller 31 then determines at block 102c' which receiver 6 or 8 will be the master and which will be the slave based on whether Vrect1 or Vrect2 is higher (block 102e') and whether Vrect2 from block 102c' is higher than Vrect1 from block 102d'.

[0089] C. Alternative Hardware, Wireless Power Transfer System 1'

[0090] Now refer to Figure 3 A second embodiment of a wireless transmission system 1' is described in which a single transmitter 2 wirelessly transmits power to a first receiver 6 and a second receiver 8 operating in parallel. The transmitter 2 comprises an AC power source 44 connected to a primary coil (schematically represented by a capacitor Cp in series with an inductor Lp and a resistor Rp).

[0091] Receivers 6 and 8 are as described above.

[0092] D. Operation of Wireless Power Transmission System 1'

[0093] The operation of the wireless power transmission system 1 ′ is performed in the same manner as the wireless power transmission system 1 described above, except that the transmitter 2 is turned on when either transmitter 5 or 7 is turned on and is turned off when both transmitters 5 and 7 are turned off.

[0094] E. Other alternative hardware configurations

[0095] While one transmitter is paired with two receivers, and two transmitters are paired with two receivers, it should be understood that other configurations are possible. For example, there may be three or more receivers, one of which acts as a master (and performs the functions described above), and two or more of which act as slaves (and perform the functions described above).

[0096] While the present disclosure has been described with respect to a limited number of embodiments, those skilled in the art having benefit of this disclosure will appreciate that other embodiments can be conceived without departing from the scope of the present disclosure as disclosed herein. Accordingly, the scope of the present disclosure should be limited only by the appended claims.

Claims

1. A wireless power transmission system, comprising: at least one wireless power transfer circuit; a first wireless power receiving circuit comprising a first amplifier circuit configured to compare a reference voltage with a feedback voltage representing a voltage at an output node generated based on power received from the at least one wireless power transmitting circuit, and to regulate a first transistor sourcing a first rectified current until the feedback voltage equals the reference voltage, wherein the first rectified current is delivered to the output node; a second wireless power receiving circuit comprising a second amplifier circuit configured to modify a gate bias of a second transistor sourcing a second rectified current based on a comparison of a reference current and a current representing a second rectified current generated based on power received from the at least one wireless power transmitting circuit, thereby modifying the second rectified current, wherein the second rectified current is delivered to the output node; as well as The control circuit system is configured to adjust the reference current until a first rectified voltage generated by the first wireless power receiving circuit and a second rectified voltage generated by the second wireless power receiving circuit are equal.

2. The wireless power transmission system of claim 1 , wherein the first wireless power receiving circuit further comprises a first capacitor, the first rectified voltage being formed across the first capacitor; and wherein the second wireless power receiving circuit further comprises a second capacitor, the second rectified voltage being formed across the second capacitor.

3. The wireless power transmission system of claim 1 , wherein the first amplifier circuit comprises: a first n-channel transistor having a drain coupled to receive the first rectified voltage, a source coupled to the output node, and a gate; a voltage divider coupled between the output node and ground; as well as A first amplifier has a non-inverting terminal coupled to the reference voltage, an inverting terminal coupled to a tap of the voltage divider to receive the feedback voltage, and an output coupled to the gate of the first n-channel transistor.

4. The wireless power transmission system according to claim 3, wherein the second amplifier circuit comprises: a second n-channel transistor having a drain coupled to the second rectified voltage, a source coupled to the output node, and a gate; as well as A second amplifier has a non-inverting terminal coupled to receive the current representing the second rectified current, an inverting terminal coupled to receive the reference current, and an output coupled to the gate of the second n-channel transistor.

5. The wireless power transmission system according to claim 4 further includes an equalizer switch, which is controlled by the control circuit system to selectively couple the first rectified voltage to the second rectified voltage until the first rectified voltage and the second rectified voltage are equal when the control circuit system cannot adjust the reference current. The wireless power transmission system of claim 1 , wherein the first amplifier circuit comprises a low-dropout amplifier.

7. The wireless power transmission system of claim 1 , wherein the control circuitry adjusts the reference current until the first rectified voltage and the second rectified voltage are equal by: requesting the at least one wireless power transmission circuit to transmit a portion of the power that can be transmitted by the at least one wireless power transmission circuit to the first wireless power reception circuit; as well as The reference current is adjusted in the following manner until a first equilibrium point is reached where the first rectified voltage and the second rectified voltage are equal: requesting the at least one wireless power transmission circuit to increase the portion of power transmitted by the at least one wireless power transmission circuit to the first wireless power reception circuit if the first rectified voltage is greater than the output voltage at the output node and if the output voltage is greater than the second rectified voltage; If the second rectified voltage is greater than the first rectified voltage and the first rectified voltage is greater than the output voltage, increasing the magnitude of the reference current; as well as If the first rectified voltage is greater than the second rectified voltage and the second rectified voltage is greater than the output voltage, the magnitude of the reference current is reduced.

8. The wireless power transmission system of claim 7 , wherein the control circuitry further adjusts the reference current until the first rectified voltage and the second rectified voltage are equal by: requesting the at least one wireless power transmission circuit to transmit a portion of the power that can be transmitted by the at least one wireless power transmission circuit to the second wireless power reception circuit; as well as The reference current is adjusted in the following manner until a second equilibrium point is reached where the first rectified voltage and the second rectified voltage are equal: If the second rectified voltage is greater than the first rectified voltage and the first rectified voltage is greater than the output voltage, increasing the magnitude of the reference current; as well as If the first rectified voltage is greater than the second rectified voltage and the second rectified voltage is greater than the output voltage, the magnitude of the reference current is reduced.

9. The wireless power transmission system of claim 8 , wherein the control circuitry further adjusts the reference current until the first rectified voltage and the second rectified voltage are equal by: requesting the at least one wireless power transmission circuit to transmit all power that the at least one wireless power transmission circuit can transmit to the first wireless power receiving circuit and the second wireless power receiving circuit; as well as The reference current is adjusted in the following manner until a third equilibrium point is reached where the first rectified voltage and the second rectified voltage are equal: If the second rectified voltage is greater than the first rectified voltage and the first rectified voltage is greater than the output voltage, increasing the magnitude of the reference current; as well as If the first rectified voltage is greater than the second rectified voltage and the second rectified voltage is greater than the output voltage, the magnitude of the reference current is reduced.

10. A wireless power transmission system, comprising: at least one wireless power transfer circuit; a main wireless power receiving circuit comprising a voltage reference circuit configured to regulate an output voltage at an output node until a feedback voltage equals a reference voltage, wherein the feedback voltage represents a first output voltage generated based on power received from the at least one wireless power transmitting circuit; as well as a plurality of slave wireless power receiving circuits, each slave wireless power receiving circuit including a current reference circuit configured to regulate a corresponding rectified current generated by the slave wireless power receiving circuit from power received from the master wireless power receiving circuit and delivered to the output node until a first rectified voltage generated by the master wireless power receiving circuit is equal to a second rectified voltage generated by the slave wireless power receiving circuit.

11. A wireless power transmission system according to claim 10, wherein the main wireless power receiving circuit further includes a first capacitor, and the first rectified voltage is formed across the first capacitor; and wherein each wireless power receiving circuit further includes a second capacitor, and the second rectified voltage is formed across the second capacitor.

12. The wireless power transmission system according to claim 10, wherein the voltage reference circuit comprises: a three-terminal device or group of devices having a first terminal coupled to receive the first rectified voltage, a second terminal coupled to an output node, and a control terminal; a voltage divider coupled between the output node and ground; as well as A first amplifier has a non-inverting terminal coupled to the reference voltage, an inverting terminal coupled to a tap of the voltage divider to receive the feedback voltage, and an output coupled to the control terminal of the three-terminal device or device group.

13. The wireless power transmission system of claim 12 , wherein each current source circuit comprises: a three-terminal device or group of devices having a first terminal coupled to the second rectified voltage, a second terminal coupled to the output node, and a control terminal; as well as A second amplifier has a non-inverting terminal coupled to receive a current representative of the rectified current, an inverting terminal coupled to receive a reference current, and an output coupled to the control terminal of the three-terminal device or devices of the current source circuit.

14. The wireless power transmission system according to claim 13 further includes an equalizer switch, which is used to selectively couple the first rectified voltage to the second rectified voltage when the current reference circuit cannot adjust the reference current until the first rectified voltage and the second rectified voltage are equal.

15. A method for wirelessly transmitting power, the method comprising: causing at least one power transmission circuit to transmit a portion of the power capable of being transmitted by the at least one power transmission circuit to the primary wireless power receiving circuit; Adjusting the operation of at least one slave wireless power receiving circuit until a first rectified voltage generated by the master wireless power receiving circuit and a second rectified voltage generated by the at least one slave wireless power receiving circuit are equal by: requesting the at least one power transmission circuit to increase the portion of power transmitted by the at least one power transmission circuit to the master wireless power receiving circuit if the first rectified voltage is greater than an output voltage at an output node and if the output voltage is greater than the second rectified voltage; regulating operation of the at least one slave wireless power receiving circuit if the second rectified voltage is greater than the first rectified voltage and the first rectified voltage is greater than the output voltage; as well as If the first rectified voltage is greater than the second rectified voltage and the second rectified voltage is greater than the output voltage, operation of the at least one slave wireless power receiving circuit is adjusted.

16. The method of claim 15 , wherein the operations of the plurality of slave wireless power receiving circuits are adjusted until the first rectified voltage and the second rectified voltage generated by each of the plurality of slave wireless power receiving circuits are equal by: requesting the at least one power transmission circuit to increase the portion of power transmitted by the at least one power transmission circuit to the master wireless power receiving circuit if the first rectified voltage is greater than an output voltage at an output node and if the output voltage is greater than the second rectified voltage; regulating operation of the plurality of slave wireless power receiving circuits if the second rectified voltage is greater than the first rectified voltage and the first rectified voltage is greater than the output voltage; as well as If the first rectified voltage is greater than the second rectified voltage and the second rectified voltage is greater than the output voltage, operations of the plurality of slave wireless power receiving circuits are adjusted.

17. A method for wirelessly transmitting power, comprising: causing at least one power transmission circuit to transmit a portion of the power capable of being transmitted by the at least one power transmission circuit to the primary wireless power receiving circuit; adjusting the operation of at least one slave wireless power receiving unit until a balance point is reached where a first rectified voltage generated by the master wireless power receiving circuit and a second rectified voltage generated by the at least one slave wireless power receiving unit are equal; connecting a dummy load to the at least one slave wireless power receiving unit; causing the at least one power transfer circuit to transfer additional power to the at least one slave wireless power receiving unit after connecting the dummy load to the at least one slave wireless power receiving unit, resulting in the first rectified voltage and the second rectified voltage being unequal; as well as after causing the at least one power transfer circuit to transfer additional power to the at least one slave wireless power receiving unit, adjusting operation of the at least one slave wireless power receiving unit until the first rectified voltage and the second rectified voltage are again equal, and disconnecting the dummy load from the at least one slave wireless power receiving unit once the first rectified voltage and the second rectified voltage are again equal; Wherein adjusting the operation of the at least one slave wireless power receiving unit until the first rectified voltage and the second rectified voltage are equal again includes: if the first rectified voltage is greater than the second rectified voltage, adjusting the operation of the at least one slave wireless power receiving unit to request more additional power from the at least one power transmission circuit.

18. The method according to claim 17, further comprising: causing the at least one power transfer circuit to transfer further additional power to the at least one slave wireless power receiving unit, resulting in the first rectified voltage and the second rectified voltage being unequal; After causing the at least one power transfer circuit to transfer further additional power to the at least one slave wireless power receiving unit, operation of the at least one slave wireless power receiving unit is adjusted until the first rectified voltage and the second rectified voltage are again equal.

19. The method of claim 18, wherein adjusting the operation of the at least one slave wireless power receiving unit until the first rectified voltage and the second rectified voltage are again equal comprises: adjusting operation of the at least one slave wireless power receiving unit if the second rectified voltage is greater than the first rectified voltage and the first rectified voltage is greater than an output voltage; as well as If the first rectified voltage is greater than the second rectified voltage, and the second rectified voltage is greater than the output voltage, an operation of the at least one slave wireless power receiving unit is adjusted.

20. A wireless power transmission system, comprising: a first wireless power receiving circuit configured to compare a reference voltage with a feedback voltage representing a voltage generated at an output node from wirelessly received power, and to adjust a first current source that supplies a first rectified current until the feedback voltage is equal to the reference voltage, the first rectified current being delivered to the output node; as well as The second wireless power receiving circuit is configured to modify operation of a second current source that sources the second rectified current generated from the wirelessly received power based on a comparison of a reference current and a current representative of the second rectified current, thereby modifying the second rectified current, the second rectified current being delivered to the output node.

21. The wireless power transmission system according to claim 20, further comprising: The control circuit system is configured to adjust the reference current until a first rectified voltage generated by the first wireless power receiving circuit and a second rectified voltage generated by the second wireless power receiving circuit are equal.

22. The wireless power transmission system of claim 21 , wherein the control circuitry adjusts the reference current until the first rectified voltage and the second rectified voltage are equal by: requesting an additional wireless power transfer to the second wireless power receiving circuit, resulting in the first rectified voltage and the second rectified voltage being unequal; and Thereafter, the reference current is adjusted until a first equilibrium point is reached where the first rectified voltage and the second rectified voltage are equal.

23. The wireless power transmission system of claim 22, wherein the reference current is adjusted until the first equilibrium point is reached by: requesting an increase in wireless power transmission to the second wireless power receiving circuit if the first rectified voltage is greater than the output voltage at the output node and if the output voltage is greater than the second rectified voltage; If the second rectified voltage is greater than the first rectified voltage and the first rectified voltage is greater than the output voltage, increasing the reference current; as well as If the first rectified voltage is greater than the second rectified voltage and the second rectified voltage is greater than the output voltage, the reference current is reduced.

24. The wireless power transmission system of claim 23 , wherein the control circuitry further adjusts the reference current until the first rectified voltage and the second rectified voltage are equal by: requesting an increase in wireless power transmission to the second wireless power receiving circuit, with the result that the first rectified voltage and the second rectified voltage are again unequal; and The reference current is adjusted until a second equilibrium point is reached where the first rectified voltage and the second rectified voltage are equal again.

25. The wireless power transmission system of claim 24, wherein the reference current is adjusted until the second equilibrium point is reached by: If the second rectified voltage is greater than the first rectified voltage and the first rectified voltage is greater than the output voltage, increasing the magnitude of the reference current; and If the first rectified voltage is greater than the second rectified voltage and the second rectified voltage is greater than the output voltage, the magnitude of the reference current is reduced.

26. The wireless power transmission system of claim 25 , wherein the control circuitry further adjusts the reference current until the first rectified voltage and the second rectified voltage are equal by: requesting maximum wireless power transfer to the first wireless power receiving circuit and the second wireless power receiving circuit; and The reference current is adjusted until a third equilibrium point is reached where the first rectified voltage and the second rectified voltage are equal.

27. The wireless power transmission system of claim 26, wherein the reference current is adjusted until the third equilibrium point is reached by: If the second rectified voltage is greater than the first rectified voltage and the first rectified voltage is greater than the output voltage, increasing the magnitude of the reference current; and If the first rectified voltage is greater than the second rectified voltage and the second rectified voltage is greater than the output voltage, the magnitude of the reference current is reduced.

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