PATENT DOCUMENT

Publication Number: US-10355514-B2
Application Number: US-201715485078-A
Country: US
Kind Code: B2

Title: Rectifier arbitration in wireless charging systems

Abstract:
A wireless power transmitting device may transmit power wirelessly to a wireless power receiving device. The wireless power receiving device may be a portable electronic device with an array of wireless power receiving coils that receive wireless power from wireless power transmitting coils in the wireless power transmitting device. Each receiving coil in the array of wireless power receiving coils may be coupled to a respective rectifier. Control circuitry of the wireless power receiving device may be configured to determine which rectifiers to enable for synchronous rectification. The control circuitry may be configured to enable at least one rectifier based on the alternating-current voltages produced by each coil in the array of receiving coils. The control circuitry may also be configured to enable at least one rectifier based on the output current from each rectifier.

Claims:
What is claimed is: 
     
       1. An electronic device configured to receive wireless power from a power transmitting device, comprising:
 first and second coils configured to receive alternating-current magnetic signals transmitted from the power transmitting device and configured to produce corresponding alternating-current voltages; 
 a first rectifier coupled to the first coil, wherein the first rectifier has transistors configured to rectify the alternating-current voltages from the first coil and produce a corresponding rectified direct-current voltage when active rectification in the first rectifier is enabled; 
 a second rectifier coupled to the second coil, wherein the second rectifier has transistors configured to rectify the alternating-current voltages from the second coil and produce a corresponding rectified direct-current voltage when active rectification in the second rectifier is enabled; and 
 control circuitry including a comparator that has first and second inputs, wherein a first node between the first coil and the first rectifier is coupled to the first input of the comparator, wherein a second node between the second coil and the second rectifier is coupled to the second input of the comparator, and wherein the control circuitry is configured to enable active rectification in at least one of the first rectifier and the second rectifier based on an output of the comparator. 
 
     
     
       2. The electronic device defined in  claim 1 , further comprising a first resistor and a first capacitor, wherein the first resistor is coupled between the first node and the first input of the comparator, wherein the first resistor is coupled to a third node that is interposed between the first node and the first input, and wherein the first capacitor is coupled between the third node and ground. 
     
     
       3. The electronic device defined in  claim 2 , further comprising a second resistor and a second capacitor, wherein the second resistor is coupled between the second node and the second input of the comparator, wherein the second resistor is coupled to a fourth node that is interposed between the second node and the second input, and wherein the second capacitor is coupled between the fourth node and ground. 
     
     
       4. The electronic device defined in  claim 1 , wherein the first rectifier and the second rectifier are both coupled to a common rectifier output node, the electronic device further comprising a first additional comparator that has first and second inputs, wherein the common rectifier output node is coupled to the first input of the first additional comparator and wherein a first threshold voltage is provided to the second input of the first additional comparator. 
     
     
       5. The electronic device defined in  claim 4 , further comprising a second additional comparator that has first and second inputs, wherein the common rectifier output node is coupled to the first input of the second additional comparator and wherein a second threshold voltage is provided to the second input of the second additional comparator. 
     
     
       6. The electronic device defined in  claim 1 , wherein the first rectifier has an output that is coupled to a common rectifier output node and wherein the second rectifier has an output that is coupled to the common rectifier output node, the electronic device further comprising a first sensing resistor coupled between the output of the first rectifier and the common rectifier node and a first voltage meter that measures a voltage drop across the first sensing resistor in order to measure an output current of the first rectifier. 
     
     
       7. The electronic device defined in  claim 6 , further comprising a second sensing resistor coupled between the output of the second rectifier and the common rectifier output node and a second voltage meter that measures a voltage drop across the second sensing resistor in order to measure an output current of the second rectifier. 
     
     
       8. The electronic device defined in  claim 6 , further comprising a second sensing resistor coupled to the common rectifier output node and a second voltage meter that measures a voltage drop across the second sensing resistor in order to measure a combined output current of the first and second rectifiers.

Description:
This application claims the benefit of provisional patent application No. 62/380,832, filed Aug. 29, 2016, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to charging systems that use inductive power, and, more particularly, to wireless power receiving devices in charging systems that include rectification circuitry. 
     BACKGROUND 
     In a wireless charging system, a power transmitting device may wirelessly transmit power to a power receiving device such as a portable electronic device. A portable device may have a receiving coil and rectifier circuitry for receiving wireless alternating-current (AC) power from a coil in the power transmitting device that is overlapped by the receiving coil. The rectifier converts the received AC power into direct-current (DC) power. 
     It can be challenging to effectively transmit power from a power transmitting device to a power receiving device. If care is not taken, the wireless charging system may not be sufficiently flexible and power may not be effectively transmitted in some circumstances. 
     SUMMARY 
     A wireless power transmitting device may transmit power wirelessly to a wireless power receiving device. The wireless power transmitting device may be a wireless charging mat or other equipment with an array of wireless power transmitting coils. The wireless power receiving device may be a portable electronic device with a battery, an array of wireless power receiving coils that receive wireless power from the array of wireless power transmitting coils, and rectifiers that receive alternating-current signals from the wireless power receiving coils and provide a corresponding rectified direct-current voltage signal to circuitry in the wireless power receiving device. 
     Each receiving coil in the array of wireless power receiving coils may be coupled to a respective rectifier. Each rectifier may be coupled to a common rectifier output node. The control circuitry of the wireless power receiving device may be configured to determine which rectifiers to enable for synchronous rectification. 
     The control circuitry may be configured to enable at least one rectifier based on the alternating-current voltages produced by each coil in the array of receiving coils. The alternating-current voltages produced by each coil may be relied upon to determine which rectifier to enable during power-up of the power receiving circuitry in the wireless power receiving device. 
     The control circuitry may also be configured to enable at least one rectifier based on the output current from each rectifier. The control circuitry may measure an output current from each rectifier and enable that rectifier if the output current is greater than a threshold. The output currents of the rectifiers may be relied upon to determine which rectifiers to enable during power transfer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative wireless charging system that includes a wireless power transmitting device and a wireless power receiving device in accordance with an embodiment. 
         FIG. 2  is a circuit diagram of illustrative wireless power transmitting equipment in accordance with an embodiment. 
         FIG. 3  is a schematic diagram of an illustrative wireless charging system showing how control circuitry may be coupled to rectifier circuitry in accordance with an embodiment. 
         FIG. 4  is a circuit diagram of illustrative circuitry that performs rectifier arbitration based on the AC voltage of each coil in accordance with an embodiment. 
         FIG. 5  is a flowchart of illustrative method steps for enabling a rectifier in a wireless charging system during power-up in accordance with an embodiment. 
         FIG. 6  is a circuit diagram of illustrative circuitry that performs rectifier arbitration based on the envelope signal of the AC voltage of each coil in accordance with an embodiment. 
         FIG. 7  is a circuit diagram of illustrative circuitry that directly measures the output current from each rectifier to determine which rectifiers to enable and disable during power transfer in accordance with an embodiment. 
         FIG. 8  is a circuit diagram of illustrative circuitry that uses envelope detection and load-line compensation to determine which rectifiers to enable and disable during power transfer in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A wireless power system may have a wireless power transmitting device such as a wireless power adapter or other wireless power transmitting equipment. The wireless power transmitting device may wirelessly transmit power to a wireless power receiving device such as a wristwatch, cellular telephone, tablet computer, laptop computer, or other electronic equipment. The wireless power receiving device may use power from the wireless power transmitting device for powering the device and for charging an internal battery. 
     An illustrative wireless power system (wireless charging system) is shown in  FIG. 1 . As shown in  FIG. 1 , wireless power system  10  may include a wireless power transmitting device such as wireless power transmitting device  12  and may include a wireless power receiving device such as wireless power receiving device  24 . 
     Power transmitting device  12  may be a stand-alone power adapter (e.g., a wireless charging mat that includes power adapter circuitry), may be a wireless charging mat that is coupled to a power adapter or other equipment by a cable, may be a portable device, may be equipment that has been incorporated into furniture, a vehicle, or other system, or may be other wireless power transfer equipment. 
     Power receiving device  24  may be a portable electronic device such as a wristwatch, a cellular telephone, a laptop computer, a tablet computer, or other electronic equipment. Power transmitting device  12  may be coupled to a wall outlet (e.g., alternating current), may have a battery for supplying power, and/or may have another source of power. Power transmitting device  12  may have an AC-DC power converter such as power converter  14  for converting AC power from a wall outlet or other power source into DC power. DC power may be used to power control circuitry  16 . During operation, a controller in control circuitry  16  may use power transmitting circuitry  52  to transmit wireless power to power receiving circuitry  54  of device  24 . Power transmitting circuitry  52  may have switching circuitry (e.g., transistors) that are turned on and off based on control signals provided by control circuitry  16  to create AC current signals through one or more coils in coil array  42 . As the AC currents pass through coil array  42 , alternating-current magnetic fields (signals  44 ) are produced that are received by coils  48 ′ in corresponding coil array  48  in power receiving device  24 . When the alternating-current magnetic fields are received by the coil array, corresponding alternating-current voltages are induced in the coil array. Rectifier circuitry  50  may convert received AC signals (received alternating-current voltages associated with wireless power signals) from coil array  48  into DC voltage signals for powering device  24 . Each coil  48 ′ may have a corresponding rectifier  50 ′ that is used to convert the received AC signals into DC voltage signals. The DC voltages may be used in powering components in device  24  such as a display, touch sensor components, wireless circuits, audio components, and other components and may be used in charging an internal battery in device  24 . 
     Device  12  and/or device  24  may communicate wirelessly using in-band or out-of-band communications. Device  12  may, for example, have wireless transceiver circuitry  40  that wirelessly transmits out-of-band signals to device  24  using an antenna or that wirelessly transmits in-band signals to device  24  using coil array  42 . Wireless transceiver circuitry  40  may be used to wirelessly receive out-of-band signals from device  24  using the antenna or may be used to wirelessly receive in-band signals from device  24  using coil array  42 . Device  24  may have wireless transceiver circuitry  46  that transmits out-of-band signals to device  12  using an antenna or that transmits in-band signals to device  12  using coil array  48 . Receiver circuitry in wireless transceiver  46  may use an antenna to receive in-band signals from device  12  or may use coil array  48  to receive in-band signals from device  12 . 
     During power transmission operations, one or more coil  48 ′ may supply received AC voltages (i.e., receive wireless power signals) to a corresponding rectifier  50 ′. Each rectifier  50 ′ contains rectifying components such as synchronous rectification metal-oxide-semiconductor transistors arranged in a bridge network. Other configurations are possible for each rectifier  50 ′. For example, each rectifier  50 ′ may be arranged in a half-bridge or any other desired configuration. 
     Illustrative circuitry of the type that may be used for forming power transmitting circuitry  52  of  FIG. 1  is shown in  FIG. 2 . As shown in  FIG. 2 , power transmitting circuitry  52  may include drive circuitry such as drive circuitry  60  coupled to coils such as coil  42 ′ in coil array  42  ( FIG. 1 ). Drive circuitry  60  may receive direct-current (DC) voltage Vdc from AC-DC converter  14 . Drive circuitry  60  may have transistors such as transistors  62  (e.g., metal-oxide-semiconductor transistors or other suitable transistors). Transistors  62  may be coupled in series between a terminal that receives positive power supply voltage Vdc and a ground terminal that receives a ground voltage or any other desired reference voltage. Capacitor  64  may be coupled to node ND between transistors  62 . During operation, control circuitry  16  may apply control signals such as control signal IN and complementary (inverted) signal NIN to respective gates G of transistors  62 . Control circuitry  16  may modulate signals IN and NIN so that transistors  62  produce an AC drive signal. Capacitor  64  may be used to couple the AC drive signal to a coil such as coil  42 ′ in array  42  that is coupled to transistors  62 . As the AC signal flows through coil  42 ′, wireless power signal  44  ( FIG. 1 ) is produced and can be received by coil array  48  of device  24 . 
     In some situations, the wireless power receiving device may include multiple coils and rectifiers to ensure that power can be received when the wireless power receiving device is in different positions relative to the wireless power transmitting device. For example, wireless power transmitting device  12  may include one transmitting coil, while wireless power receiving device  24  may include two or more receiving coils. This type of arrangement increases the likelihood that one of the receiving coils in the wireless power receiving device will receive wireless signals  44  from the transmitting coil (relative to scenarios where only a single receiving coil is used). If the wireless power receiving device is in a first position relative to the wireless power transmitting device, a first receiving coil may receive the wireless signals  44  from the transmitting coil. However, if the wireless power receiving device is in a second position relative to the wireless power transmitting device, a second receiving coil may receive the wireless signals from the transmitting coil. 
       FIG. 3  shows a schematic diagram of portions of the power transmitting circuitry and power receiving circuitry of a wireless power system such as wireless power system  10  in  FIG. 1 . Wireless signals  44  may be transmitted from coil array  42  of wireless power transmitting device  12  to coil array  48  of wireless power receiving device  24 . As shown, coil array  48  may include multiple coils. Each coil in coil array  48  may be coupled to a respective rectifier in rectifier array  50 . Each rectifier may be capable of converting AC signals received by its respective coil into DC voltage signals for powering device  24 . However, if a receiving coil in coil array  48  is not receiving wireless signals from coil array  42 , it may be desirable to disable that coil&#39;s corresponding rectifier. There are a number of ways to determine which rectifiers in rectifier array  50  should be enabled or disabled. In some situations, only one rectifier in the array (e.g., the rectifier that is receiving the most power) may be enabled. In other situations, each rectifier may individually be enabled or disabled depending on the power received by the rectifier. More than one rectifier may be enabled at a time if desired. Control circuitry  30  may be coupled to rectifier circuitry  50  to control the operation of each rectifier. Control circuitry  30  may determine which rectifiers should be enabled and then enable those rectifiers. Similarly, circuitry  30  may determine which rectifiers should be disabled and then disable those rectifiers. 
     Coils in array  42  and coils in array  48  may be implemented using one or more loops of wire, using one or more loops of metal traces on a printed circuit or other suitable substrate, or may be formed from other looped signal paths. The coils may have circular outlines (footprints when viewed from above), hexagonal outlines, rectangular outlines, polygonal outlines, elliptical outlines, an outline that includes a combination of polygonal and curve shapes, or any other desired shape. The coils may have 1-100 turns, more than 5 turns, more than 15 turns, more than 30 turns, fewer than 75 turns, fewer than 50 turns, or other desired numbers of turns. The coils may have diameters of 5 mm or more, 10 mm or more, 15 mm or more, 20 mm or more, 30 mm or more, 50 mm or more, 100 mm or less, 60 mm or less, 35 mm or less, 5 mm or less, or other desired diameters. The frequency of the AC wireless signals in system  10  (e.g., signals  44 ) may be 100 kHz to 10 MHz, more than 200 kHz, more than 500 kHz, more than 1 MHz, more than 5 MHz, less than 20 MHz, less than 10 MHz, less than 1 MHz, or other desired frequency. 
       FIG. 4  is a circuit diagram showing illustrative circuitry of the type that may be used in implementing power receiving circuitry and control circuitry in a wireless power receiving device. As shown in  FIG. 4 , the power receiving circuitry may include at least first and second receiving coils  48 - 1  and  48 - 2 . Each receiving coil may be configured to receive wireless signals from transmitting coil  42 ′. Each receiving coil may be coupled to a respective rectifier circuit. For example, receiving coil  48 - 1  may be coupled to rectifier  50 - 1 , whereas receiving coil  48 - 2  is coupled to rectifier  50 - 2 . As previously discussed, each receiving coil may generate alternating-current voltages in response to alternating-current magnetic fields generated by transmitting coil  42 ′. Each rectifier may then convert the received AC signals into DC voltage signals (e.g., V RECT1  and V RECT2 ) for powering device  24 . The rectifiers may be coupled to a common DC output node  96  such that a single DC voltage signal (V RECT ) is output from the rectifier circuitry. 
     In general, a rectifier circuit is a circuit that converts alternating current into direct current. There are a number of ways to form a rectifier. In  FIG. 4 , each rectifier is depicted as having four diodes ( 72 ) in a bridge circuit configuration. In some cases, diodes may be used to form each rectifier. However, it may be desirable for the rectifiers to be active rectifiers that perform active rectification. In active rectification (sometimes referred to as synchronous rectification), the diodes of  FIG. 4  are replaced with transistors that are controlled by a separate controller. The transistors may be controlled to translate an alternating current into direct current with minimum power loss. The transistors may be transistors with back gate diodes. The transistors may be coupled to comparators and controlled by a controller such as controller  51 . When it is desired to enable rectifier  50 - 1 , controller  51  may send an enable signal to the comparator associated with each transistor in rectifier  50 - 1  such that the transistors are alternately turned on and off in a synchronous rectification scheme. Rectifiers  50 - 1  and  50 - 2  in  FIG. 4  may include transistors with back gate diodes that are coupled to comparators. Controller  51  may control the transistors of each rectifier. However, for simplicity of the drawing these transistors are represented with the diode circuit diagram symbol in  FIG. 4 , and the connections between the transistors  72  and controller  51  are not shown. In general, any desired rectifier circuits may be used. 
     Control circuitry  30  may include controller  51  and rectifier arbitration circuitry  53 . Control circuitry  30  may be used to determine whether to enable rectifier  50 - 1  or  50 - 2 . There may be multiple ways of determining which rectifier to enable depending on the status of the power receiving circuitry. During power-up of power receiving circuitry  54  (when the output load is not yet enabled), voltage measurement may be used to determine which rectifier should be enabled. In other words, the magnitude of voltage produced by coils  48 - 1  and  48 - 2  may be compared to determine whether to enable rectifier  50 - 1  or rectifier  50 - 2 . During power transfer, however, an output current will flow from the rectifiers to an output load (e.g., an internal battery). Consequently, the voltages of each coil may appear to be nearly equal. Therefore, during power transfer the output current of each rectifier may be examined directly to determine which rectifiers should be enabled. 
     In the example of  FIG. 4 , rectifier arbitration circuitry uses voltage measurement to determine which rectifier should be enabled during power-up of the power receiving circuitry. As shown, the AC signal produced by coil  48 - 1  (AC 1 ) may be sampled at node  74 . Similarly, the AC signal produced by coil  48 - 2  (AC 2 ) may be sampled at node  76 . The voltages from each coil may be compared by control circuitry  30 . Control circuitry  30  may include low-pass filters for each AC signal. For example, resistor  78  and capacitor  80  may form a low-pass filter that filters AC 1 , whereas resistor  82  and  84  may form a low-pass filter that filters AC 2 . Resistor  78  may be coupled to node  81 , whereas capacitor  80  may be coupled between node  81  and ground. Resistor  82  may be coupled to node  85 , whereas capacitor  84  may be coupled between node  85  and ground. Each low-pass filter may attenuate signals with frequencies greater than a selected cutoff frequency. This may reduce noise in the AC signals produced by each coil. 
     After passing through the low-pass filter formed by resistor  78  and capacitor  80 , the voltage at node  81  (AC 1 _AV) may be considered a representation of the magnitude of the AC signal produced by coil  48 - 1  (AC 1 ). The voltage at node  85  (AC 2 _AV) may be considered a representation of the magnitude of the AC signal produced by coil  48 - 2  (AC 2 ). The magnitude of each AC signal may be determined in a number of different ways. For example, the magnitude of each AC signal may be considered the average voltage of the AC signal for a predetermined time period (such as half of a cycle) or the root-mean squared of the AC signal. 
     The magnitude of each AC signal may be compared by comparator  86 . Comparator  86  may receive voltage AC 1 _AV at a first input and voltage AC 2 _AV at a second input. The comparator may compare the magnitude of voltage AC 1 _AV to the magnitude of voltage AC 2 _AV. The output of comparator  86  may be an arbitration signal (ARB) that is provided to controller  51 . The arbitration signal may have a value indicative of which coil has a higher voltage (e.g., signal ARB may be asserted at a logic high level “1” if AC 1 _AV is greater than AC 2 _AV whereas ARB may be provided at a logic low level “0” if AC 2 _AV is greater than AC 1 _AV). If desired, an offset voltage source  88  may provide an offset voltage (VOS) that offsets voltage AC 1 _AV. The offset voltage may have any desired value (i.e., 50 mV, less than 50 mV, greater than 50 mV, between 25 and 75 mV, etc.). 
     Sampling the AC signals from each coil and determining which coil has a higher voltage may not be the only criteria in selecting a rectifier to enable during power-up. For example, each rectifier may have a respective direct current voltage threshold for selection. Before enabling a rectifier for synchronous rectification, the rectifiers may operate in a passive rectification mode. Accordingly, the rectifiers may produce a DC voltage output (V RECT ). The DC voltage signal V RECT  may be compared to respective threshold values by comparators  90  and  92 . For example, comparator  90  may receive V RECT  at a first input and a first threshold V TH1  at a second input. When V RECT  is greater than the threshold V TH1 , the output from comparator  90  (V R1   _   START ) may be high. When V RECT  is less than the threshold V TH1 , the output from comparator  90  may be low. V TH1  may be a predetermined threshold associated with rectifier  50 - 1 . Comparator  92  may receive V RECT  at a first input and a second threshold V TH2  at a second input. When V RECT  is greater than the threshold V TH2 , the output from comparator  92  (V R2   _   START ) may be high. When V RECT  is less than the threshold V TH2 , the output from comparator  92  may be low. V TH2  may be a predetermined threshold associated with rectifier  50 - 2 . V TH1  and V TH2  may be different threshold voltages or may be the same threshold voltage if desired. Any desired threshold voltage level may be used for each threshold (i.e., 4V, 6V, between 1V and 10V, less than 1V, more than 1V, etc.). The outputs from comparators  90  and  92  may be provided to controller  51 . Using ARB, V R1   _   START , and V R2   _   START , the controller may determine which rectifier to enable during power-up. 
       FIG. 5  is a flowchart showing illustrative processing steps for determining which rectifier in  FIG. 4  to enable during power-up. These processing steps may be performed by control circuitry  30 , for example. At step  102 , control circuitry  30  may begin processing operations. At step  104 , control circuitry  30  may determine whether V RECT  is greater than an initialization threshold voltage. This initialization threshold voltage may be a small predetermined voltage that is used to determine when power is being received by wireless power receiving circuitry  54 . The initialization threshold voltage may have any desired value. If it is determined that V RECT  is not greater than the initialization threshold voltage, the step may be repeated after some time delay. If it is determined that V RECT  is greater than the initialization threshold voltage, the processing may proceed to step  106 . 
     At step  106 , control circuitry  30  may be determined whether V RECT  is greater than the first rectifier threshold voltage (V TH1 ) and the first coil has a greater voltage than the second coil. If both of these conditions are met, the first rectifier may be enabled at step  107 . The conditions of step  106  may ensure that rectifier  50 - 1  is enabled only if coil  48 - 1  has a greater voltage than coil  48 - 2  and V RECT  is greater than V TH1  (i.e., both ARB and V R1   _   START  would need to be true for rectifier  50 - 1  to be enabled at step  107 ). 
     If the conditions of step  106  are not met, the processing may proceed to step  108 . At step  108 , control circuitry  30  may determine whether V RECT  is greater than the second rectifier threshold voltage (V TH2 ) and the second coil has a greater voltage than the first coil. If both of these conditions are met, the second rectifier may be enabled at step  110 . The conditions of step  108  may ensure that rectifier  50 - 2  is enabled only if coil  48 - 2  has a greater voltage than coil  48 - 1  and V RECT  is greater than V TH2  (i.e., ARB would need to be false and V R2   _   START  would need to be true for rectifier  50 - 2  to be enabled at step  110 ). If the conditions of step  108  are not met, the processing may proceed to step  112 . 
     At step  112 , control circuitry  30  may determine whether V RECT  is less than the second rectifier threshold voltage (V TH2 ) and the second coil has a greater voltage than the first coil. If both of these conditions are met, the second rectifier may be enabled in a half-bridge mode at step  114 . The conditions of step  112  may ensure that rectifier  50 - 2  is enabled in the half-bridge mode if coil  48 - 2  has a greater voltage than coil  48 - 1  and V RECT  is less than V TH2  (i.e., both ARB and V R2   _   START  would need to be false for rectifier  50 - 2  to be enabled at step  114 ). In the half-bridge mode, the direct current voltage output of the rectifier may be doubled. To enable half-bridge mode, one of the two low-side transistors in rectifier  50 - 2  may be turned on to ground one end of the coil, and the two transistors on the other end of the coil may operate synchronously under the control of control circuitry  30 . If the conditions of step  112  are not met, the first rectifier may be enabled at step  116 . This may be a fail-safe to ensure that at least one rectifier is always enabled during power-up. 
     The aforementioned operations of device  24  of system  10  may be performed by control circuitry  30 . During operation, this control circuitry (which may sometimes be referred to as processing circuitry, processing and storage, computing equipment, a computer, etc.) may be configured to perform the operations of  FIG. 5  (e.g., using dedicated hardware and/or using software code running on hardware in system  10  such as control circuitry  30 ). The software code for performing these methods, which may sometimes be referred to as program instructions, code, data, instructions, or software, may be stored on non-transitory (tangible) computer readable storage media in control circuitry  30  such as read-only memory, random-access memory, hard drive storage, flash drive storage, removable storage medium, or other computer-readable media and may be executed on processing circuitry such as microprocessors and/or application-specific integrated circuits with processing circuits in control circuitry  30 . 
     The example in which the voltage produced by each coil is used to determine which rectifier is enabled during power-up is merely illustrative. If desired, other operations may be performed to determine which rectifier to enable during power-up. As shown in  FIG. 4 , a load may optionally be connected to each coil in the coil array. Load  94 - 1  may be coupled to coil  48 - 1  while load  94 - 2  may be coupled to coil  48 - 2 . To help determine which rectifier should be enabled, dummy load  94 - 1  may be applied to coil  48 - 1  and the corresponding load line may be measured at the common rectifier node  96 . Then, dummy load  94 - 2  may be applied to coil  48 - 2  and the corresponding load line may be measured at common rectifier node  96 . In this way, it may be possible to determine which coil has a higher available power and enable a rectifier accordingly. For example, this method may be most appropriate when the voltages received by each coil are nearly equal at the no-load condition, but the available power from each is different. 
       FIG. 6  is a circuit diagram of illustrative rectifier arbitration circuitry that uses the envelope of the voltage from each coil to determine which rectifier should be enabled during power-up of the power receiving circuitry. As shown, the AC voltage from coil  48 - 1  (AC 1 ) may be sampled at node  74 . Diode  122 , resistor  124 , and capacitor  126  may extract the envelope of signal AC 1  received from node  74 . Resistor  124  and capacitor  126  may be connected in parallel between diode  122  and ground. The extracted envelope of signal AC 1  may be output at node  128  as signal AC 1 _ENV. The envelope signal (AC 1 _ENV) may be used to determine the peak voltage of the voltage from coil  48 - 1 . Similarly circuitry may be included to extract the envelope of the AC voltage from coil  48 - 2  (AC 2 ). As shown, signal AC 2  may be sampled at node  76 . Diode  132 , resistor  134 , and capacitor  136  may extract the envelope of signal AC 2  received from node  76 . Resistor  134  and capacitor  136  may be connected in parallel between diode  132  and ground. The extracted envelope signal of AC 2  may be output at node  138  as signal AC 2 _ENV. The envelope signal (AC 2 _ENV) may be used to determine the peak voltage of the voltage from coil  48 - 2 . 
     The envelope signals from each coil (AC 1 _ENV and AC 2 _ENV) may then be compared using comparator  142 . Comparator  142  may receive AC 1 _ENV at a first input and AC 2 _ENV at a second input. The comparator may determine whether a peak magnitude of AC 1 _ENV or AC 2 _ENV is greater. Comparator  142  may output an arbitration signal (ARB) that is provided to additional circuitry. The arbitration signal (ARB) may have a value indicative of which coil has a higher peak voltage (i.e., ARB may be high when AC 1 _ENV is greater than AC 2 _ENV and ARB may be low when AC 2 _ENV is greater than AC 1 _ENV). In one suitable arrangement, comparator  142  may be a Schmitt trigger, which is a comparator with hysteresis. Due to the use of hysteresis, the output of the Schmitt trigger may remain constant until the input changes sufficiently to trigger a change. This may prevent ARB from having high frequency fluctuations to help stabilize the arbitration signal. 
     In some cases, signal ARB may be provided directly to controller  51  from comparator  142 . If desired, ARB may be provided to additional circuitry coupled between comparator  142  and controller  51 . As shown in  FIG. 6 , control circuitry  30  may include logic AND gates  144  and  146  and an inverter  148  coupled between comparator  142  and controller  51 . Logic AND gates  144  and  146  may receive a signal (RECT_PG) from controller  51  that is high when V RECT  is at a suitable voltage for rectifier arbitration. RECT_PG may therefore ensure that arbitration only occurs when the coils are receiving a suitable amount of power. Logic AND gate  144  may receive signal ARB at a first input and signal RECT_PG at a second input. If both ARB and RECT_PG are high, logic AND gate  144  will assert signal EN_R 1  at a logic high level, otherwise EN_R 1  is output at a logic low level. Effectively, EN_R 1  may be high if the envelope of AC 1  is higher than the envelope of AC 2  and the RECT_PG signal is high. Logic AND gate  146  may receive an inverted version of signal ARB from inverter  148  at a first input and may receive signal RECT_PG at a second input. If both the inverted version of signal ARB and signal RECT_PG are high, gate  146  may assert signal EN_R 2  at a logic high level, otherwise EN_R 2  is output at a logic low level. Effectively, EN_R 2  may be high if the envelope of AC 2  is higher than the envelope of AC 1  and the RECT_PG signal is high. EN_R 1  and EN_R 2  may be provided to controller  51 . Controller  51  may enable rectifier  50 - 1  or  50 - 2  based on signals EN_R 1  and EN_R 2 . As discussed in connection with  FIG. 4 , V RECT  may be compared to respective thresholds V TH1  and V TH2  to additionally help decide which rectifier to enable. 
     The aforementioned embodiments may be used to determine which rectifier to enable during power-up of the power receiving circuitry. However, once power transfer is occurring, an output current will flow to the output load. This may result in the voltages of each coil being nearly equal (i.e., AC 1  may be similar to AC 2 ). In these cases, comparing the magnitudes of AC 1  and AC 2  may be insufficient to determine which rectifier should be enabled. Consequently, additional circuitry may be used to determine which rectifier to enable while power transfer is occurring. 
       FIG. 7  is a circuit diagram of illustrative circuitry that may be used to determine which rectifiers to enable during power transfer. It may be desirable to directly measure the output current of each rectifier. The output current of each rectifier may be compared to a predetermined threshold current, and the rectifier may be enabled if the output current is higher than the threshold current. This method has the benefit of enabling both rectifiers to be enabled if both rectifiers are receiving a suitable amount of power. 
     To determine the output current from each rectifier, various sensing resistors and voltage meters may be included. As shown, a first sensing resistor  162  (RSNS 1 ) may be included to measure the output current from rectifier  50 - 1 . A corresponding voltage meter  168  may be used in conjunction with sensing resistor  162  to determine the output current from rectifier  50 - 1 . The resistor  162  may have a known resistance. Therefore, by determining the voltage drop across the resistor using voltage meter  168 , control circuitry  30  may be able to determine the output current from rectifier  50 - 1  using Ohm&#39;s law. The output current may then be compared to a predetermined threshold by control circuitry  30 . If the output current from rectifier  50 - 1  is higher than the predetermined threshold, rectifier  50 - 1  may be enabled. A second sensing resistor  164  (RSNS 2 ) may be included to measure the output current from rectifier  50 - 2 . A corresponding voltage meter  170  may be used in conjunction with sensing resistor  164  to determine the output current from rectifier  50 - 2 . The output current may then be compared to a predetermined threshold by control circuitry  30 . If the output current from rectifier  50 - 2  is higher than the predetermined threshold, rectifier  50 - 2  may be enabled. 
     As shown in  FIG. 7 , an additional sensing resistor  166  (RSNS 3 ) and corresponding voltage meter  172  may be included that measures the output current from both rectifiers  50 - 1  and  50 - 2 . Only two of the three sensing resistors shown in  FIG. 7  need to be included for the output current of rectifiers  50 - 1  and  50 - 2  to be determined. For example, if only sensing resistors  162  and  166  were included, sensing resistor  162  would determine the output current from rectifier  50 - 1  and sensing resistor  166  would determine the combined output current from rectifier  50 - 1  and  50 - 2 . The control circuitry could then use these two known currents to solve for the output current from rectifier  50 - 2 . In general, measuring two of the three currents will enable the third current to be calculated. Accordingly, any one of the three sensing transistors shown in  FIG. 7  may be omitted without detrimental effects. 
     The circuitry shown in  FIG. 7  for measuring the output currents from rectifiers  50 - 1  and  50 - 2  is merely illustrative. In general, any desired circuitry may be used to determine the output currents from rectifiers  50 - 1  and  50 - 2 . The measured output currents may then be used to determine which rectifiers should be enabled using any desired scheme. 
     In addition to directly measuring the output currents of the rectifiers, there are other methods that may be used for rectifier arbitration during power transfer. As discussed previously, simply looking at the voltage at each coil may not be sufficient to accurately determine which rectifier should be enabled during power transfer. However, a compensation circuit may be included that mimics the load applied to the unconnected coil such that the voltages from each coil may be compared for rectifier arbitration. 
       FIG. 8  is a circuit diagram of rectifier arbitration circuitry having envelope detection and load-line compensation capabilities.  FIG. 8  may have similar circuitry to  FIG. 6 , with the envelope (AC 1 _ENV) of the voltage from coil  48 - 1  (AC 1 ) being determined at node  128  and the envelope (AC 2 _ENV) of the voltage from coil  48 - 2  (AC 2 ) being determined at node  138 . Additionally, a comparator  142  (which may be a Schmitt trigger) may be included with additional circuitry that generates signals EN_R 1  and EN_R 2  as described in connection with  FIG. 6 . However, instead of the inputs of comparator  142  receiving envelope signals AC 1 _ENV and AC 2 _ENV, the inputs may receive compensated versions of AC 1 _ENV and AC 2 _ENV (AC 1 _COMP and AC 2 _COMP respectively). 
     The compensation circuitry may include a current mirror  180  that uses load current replica  182  to provide a scaled imitation of the load current. The load current may be the output current (at node  96  for example) that is used to power an additional component such as an internal battery. Switches  184  and  186  may be included to ensure that only one coil (e.g., the coil whose rectifier is disabled) is compensated. If signal EN_R 1  is high (indicating that rectifier  50 - 1  is enabled), it may be desirable to compensate the envelope signal from rectifier  50 - 2 . Therefore, switch  184  may be closed when EN_R 1  is high and open when EN_R 1  is low. If EN_R 2  is high (indicating that rectifier  50 - 2  is enabled), it may be desirable to compensate the envelope signal from rectifier  50 - 1 . Therefore, switch  186  may be closed when EN_R 2  is high and open when EN_R 2  is low. 
     When switch  184  is closed, the current mirror may be coupled to the gate of transistor  188  and AC 2 _ENV may be compensated. Resistor  190  and transistor  188  may be used in combination to replicate the load and compensate AC 2 _ENV. The compensated signal (AC 2 _COMP) at node  192  may be used as an input into comparator  142 . Resistor  190  and transistor  188  may be tuned so that the load is accurately imitated using the scaled replica from current mirror  180 . When switch  186  is closed, the current mirror may be coupled to the gate of transistor  196  and AC 1 _ENV may be compensated. Resistor  194  and transistor  196  may be used in combination to replicate the load and compensate AC 1 _ENV. The compensated signal (AC 1 _COMP) at node  198  may be used as an input into comparator  142 . Resistor  194  and transistor  196  may be tuned so that the load is accurately imitated using the scaled replica from current mirror  180 . 
       FIG. 8  shows compensation of the envelopes of the voltages from coils  48 - 1  and  48 - 2 . However, this example is merely illustrative and compensation circuitry as described in connection with  FIG. 8  may be included in other circuits. For example, the circuit shown in  FIG. 4  may include compensation circuitry as described in connection with  FIG. 8 , with AC 1 _AV and AC 2 _AV being compensated instead of AC 1 _ENV and AC 2 _ENV. 
     Various embodiments have been described where control circuitry may be used to determine which rectifiers to enable both during power-up, and various embodiments have been described where control circuitry may be used to determine which rectifiers to enable during power transfer. It should be understood that circuitry for rectifier arbitration during both power-up and during power transfer may be included in a single embodiment. As examples, the circuitry of  FIG. 4  and the circuitry of  FIG. 7  may be included in a single embodiment, or the circuitry of  FIG. 6  and the circuitry of  FIG. 7  may be included in a single embodiment. 
     The components of control circuitry  30  and power receiving circuitry  54  described in connection with  FIGS. 4, 6, 7, and 8  (i.e., transistors, logic gates, comparators, etc.) may be incorporated into any suitable electronic device or system of electronic devices. For example, the components may be incorporated into a printed circuit board or integrated circuit (IC). Exemplary ICs include programmable array logic (PAL), field programmable logic arrays (FPLAs), application specific standard products (ASSPs), application specific integrated circuits (ASICs), digital signal processors (DSPs), etc. Different components may be incorporated into different devices if desired (i.e., more than one IC may be included). For example, control circuitry  30  and power receiving circuitry  54  may be formed on the same integrated circuit or on different integrated circuits. In another example, different portions of control circuitry  30  may be formed on different integrated circuits, and power receiving circuitry  54  may be formed on yet another integrated circuit. 
     In the illustrative examples of  FIGS. 4, 6, 7, and 8 , two receiving coils and two rectifiers are shown. It should be noted that these examples are not meant to be limiting in any way, and more than two receiving coils and rectifiers may be used if desired. In general, any desired number (n) of receiving coils and corresponding rectifiers may be included in the power receiving device. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20170411
Publication Date: 20190716
Grant Date: 20190716
Priority Date: 20160829
Inventors: TERRY, STEPHEN C.
JANI, NILAY D.
GU, BIN
HU, Yongxuan
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J7/045", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M7/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/025", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M7/32", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/402", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J50/402", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02M7/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M7/32", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J50/10", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 61243607