Patent Publication Number: US-11387689-B2

Title: Reconfigurable power in a wireless power transfer system

Description:
CROSS-REFERENCE 
     This application is a divisional application of and claims priority to and commonly-owned U.S. application Ser. No. 16/365,310, filed Mar. 26, 2019, which in turn claims the benefit, under 35 U.S.C. § 119(e), and commonly-owned U.S. provisional application No. 62/793,348, filed on Jan. 16, 2019, both of which are hereby expressly incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     Embodiments of the present invention are related to wireless transmission of power and, in particular, to a reconfigurable power supply mechanism at a wireless power transfer system. 
     DISCUSSION OF RELATED ART 
     Mobile devices, for example smart phones, tablets, wearables and other devices are increasingly using wireless power charging systems. In general, wireless power transfer involves a transmitter driving a transmitter coil and a receiver with a receiver coil placed proximate to the transmitter coil. The receiver coil receives the wireless power generated by the transmitter coil and uses that received power to drive a load, for example to provide power to a battery charger. 
     Typically, a wireless power system includes a transmitter coil that is driven to produce a time-varying magnetic field and a receiver coil, which can be part of a device such as a cell phone, PDA, computer, or other device, that is positioned relative to the transmitter coil to receive the power transmitted in the time-varying magnetic field. Conventionally, the received power at the wireless receiver is pre-determined by circuit design and remains unchanged during operation of the wireless power system. Any modification of the received power level requires time and labor to change the circuit configuration at the wireless receiver. 
     Therefore, there is a need to develop a mechanism for a wireless power system with flexible power transfer levels. 
     SUMMARY 
     In view of the wireless transfer power level issues, embodiments described herein provide a method for wireless power transmission of reconfigurable power levels. A wireless power receiver is used to receive power from a wireless power transmitter according to a negotiated power level. The wireless power receiver determines whether a re-negotiation condition is met at the wireless power receiver. The wireless power receiver then sends, to the wireless power transmitter, a re-negotiation request for an updated power level different from the negotiated power level. The wireless power receiver receives, from the wireless power transmitter, an acknowledgement that acknowledges the updated power level, and then operates to receive power from the wireless power transmitter according to the updated power level. 
     Embodiments described herein also provide a method for wireless power transmission of reconfigurable power level. The wireless power transmitter receives from a wireless power receiver, a negotiation request for a power level. The wireless power transmitter monitors a maximum available power level and a currently available power level no greater than the maximum available power level, based at least in part on a current environment of the wireless power transmitter. The wireless power transmitter acknowledges the negotiation request when the requester power level is lower than the currently available power level. The wireless power transmitter declines the negotiation request when the requester power level exceeds the maximum available power level. The wireless power transmitter configures an input power source to support the requested power level when the requester power level is between the currently available power level and the maximum available power level. 
     These and other embodiments are discussed below with respect to the following figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  illustrates an example wireless power transmission system with reconfigurable power transfer levels, according to some embodiments. 
         FIG. 2  illustrates an example logic flow for reconfigurable power negotiation at a receiver, according to some embodiments described herein. 
         FIG. 3  illustrates an example logic flow or reconfigurable power negotiation at a transmitter, according to some embodiments described herein. 
     
    
    
     These figures are further discussed below. 
     DETAILED DESCRIPTION 
     In the following description, specific details are set forth describing some embodiments of the present invention. It will be apparent, however, to one skilled in the art that some embodiments may be practiced without some or all of these specific details. The specific embodiments disclosed herein are meant to be illustrative but not limiting. One skilled in the art may realize other elements that, although not specifically described here, are within the scope and the spirit of this disclosure. 
     This description illustrates inventive aspects and embodiments should not be taken as limiting—the claims define the protected invention. Various changes may be made without departing from the spirit and scope of this description and the claims. In some instances, well-known structures and techniques have not been shown or described in detail in order not to obscure the invention. 
       FIG. 1  illustrates an example wireless power transmission system  100  with reconfigurable power transfer levels, according to some embodiments. As illustrated in  FIG. 1 , a power transmitter TX  102  is coupled to drive a transmitter coil  106  to produce a time varying magnetic field. The time varying magnetic field induces a current in receiver coil  108 . Receiver coil  108  is coupled to power receiver RX  104 , which receives the transmitted wireless power. RX  104  is coupled to a load  114 , for example, a battery charger, which is configured to charge a battery with the received power. 
     As is further illustrated in  FIG. 1 , TX  102  and RX  104  communicate through a communications channel  110 , via their respective communication interfaces  113  and  115 . Channel  110  can be any wireless communications channel, including the back-channel available through modulation of the transmitted wireless power itself. Through channel  110 , RX  104  may request power transmission changes from TX  102 , for example, a different power level. Further, TX  102  is coupled to a power supply  112  that provides power to drive TX  102 . In some embodiments, the power supply  112  may provide adjustable power levels. In some embodiments, Tx  102  includes a circuit that adjusts the input voltage from the power supply  112  to configure an input power level. 
     Various power levels may be used for a wireless power system  100  for transmitting reconfigurable power levels from Tx  102  to Rx  104 . As used herein, the potential power (PP) is defined as the highest power TX  102  is designed to provide at the best conditions and configurations. The PP value is used as a reference during the certification process. For example, TX  102  can be issued a certificate that it meets the Wireless Power Consortium (WPC) specification up to the level of PP. 
     As used herein, the maximum available power (MAP) is defined as the maximum power that TX  102  can deliver in the current environment using its best configuration (if configuration is available), for example, when supply  112  is tuned to provide the maximum input voltage. The MAP is usually no higher than the PP. The MAP can be temporarily reduced due to an over-temperature condition at Tx  102 , which impairs the performance of Tx  102 . MAP can also be limited by the power supply  112  currently in use. RX  104  may request a power contract from TX  102  up to the MAP level. 
     As used herein, the available power (AP) is defined as the maximum power the TX  102  can deliver at the current condition. Usually AP equals MAP, but if the TX  102  power supply supports configuration of different input voltage levels, AP may be different (lower) than MAP, for example, when power supply  112  is not tuned to the maximum. 
     As used herein, the requested power (RP) is defined as the power level the RX  104  tries to negotiate with Tx  102 . The RP is limited by MAP, for example, consequently, Rx  104  should negotiate RP that is lower than MAP when knowledge of MAP is available to Rx  104 . If the RP is acknowledged by Tx  102 , the RP is also referred to as the negotiated power (NP). 
     Rx  104  and Tx  102  each include a controller  107  and  109 , respectively. Controller  107  is coupled to the power supply  112  to adjust an input power level from the power supply  112 . Controller  109  is coupled to the load  114 , e.g., to control a charging application. The controllers  107  and  109  are coupled to the communication interfaces  113  and  115 , respectively, to control message passing between Rx  104  and Tx  102 . For example, the controller  109  may initiate a negotiation request for RP and send the negotiation request via communication interface  115  to Tx  102 . For another example, the controller  107  may obtain information of MAP or AP and send indications of MAP or AP to Rx  104  via communication interface  113 . Further implementations of the power negotiation mechanism between Tx  102  and Rx  104  are discussed in relation to  FIGS. 2-3 . 
       FIG. 2  illustrates an example logic flow  200  for reconfigurable power negotiation at Rx  104 , according to some embodiments described herein. At step  202 , a negotiation request is sent from Rx  104  to Tx  102 , that requests for a RP, which is usually no greater than the MAP. For example, Rx  104  may periodically, intermittently or constantly receive indications from Tx  102 , via communication interfaces  113  and  115 , of current MAP or AP at Tx  102 . Rx  104  in turn configures the RP in a negotiation request to be no greater than the current MAP. 
     At step  204 , when the RP in the negotiation request is no greater than the MAP, Rx  104  may repeat the request with Tx  102  until an acknowledgement is received from Tx  102 . At step  206 , Rx  104  may then operate to receive power (through receiver coil  108 ) at the NP. 
     At step  208 , Rx  104  monitors the Rx power consumption status and receives updated indications of MAP or AP from Tx  102 . At step  210 , Rx  104  determines whether a re-negotiation condition is met. For example, Rx  104  is usually required to maintain the power consumption under the NP, and Rx  104  may determine whether a higher power level is required than the current NP. When Rx  104  determines that a higher power level is needed, Rx  104  may send a re-negotiate request with updated RP, at step  214 . The updated RP again is no greater than the MAP. For another example, Rx  104  may receive an updated MAP from Tx  102  and determine whether the current NP is still below the updated MAP. When MAP drops below the current NP, Rx  104  may send a re-negotiation request as soon as possible, at step  214 , for a new power contract with updated RP that meets the new limit of MAP. For another example, Rx  104  may also monitor power consumption at the Rx device, and determine whether the power consumption is reduced below a threshold level, for example, when Rx  104  is operated on a low power mode. When the power consumption is reduced below the threshold, the Rx  104  also re-negotiates a suitable lower power level contract in case of reduced power demand. If none of the re-negotiation conditions occurs, Rx  104  maintains the power transfer level at NP at step  212 . 
       FIG. 3  illustrates an example logic flow  300  for reconfigurable power negotiation at Tx  102 , according to some embodiments described herein. At step  302 , Tx  102  receives from Rx  104  a negotiation request for a power level at RP. At step  304 , Tx  102  monitors the current MAP and AP based on the current environment of Tx  102  and the power configuration. For example, the MAP may be impacted by the environment (e.g., temperature, humidity, etc.) of Tx  102 . For another example, depending on power supply  112  configuration, AP may be lower than MAP. 
     At step  306 , Tx  102  determines whether RP is no greater than the current AP. At step  308 , when RP is no greater than the current AP, Tx  102  acknowledges the negotiation request, for example, by sending an acknowledgment to Rx  104 . Once Tx  102  acknowledges the RP as NP, Tx  102  is configured to maintain the power transfer level at the NP as long as the current MAP is greater than NP. 
     Alternatively, when RP is greater than the current AP, at step  310 , Tx  102  further determines whether the RP is greater than the current MAP. At step  312 , when the RP is greater than the current MAP, Tx  102  declines the negotiation request. At step  314 , when the RP is no greater than the current MAP, i.e., AP&lt;RP≤MAP, Tx  102  configures the power supply  112 , for example, to increase the AP to support the RP. 
     At step  316 , Tx  120  determines whether a time lapse is greater than a threshold while the power supply  112  is being configured to boost the AP. If the time lapse is too long (e.g., greater than the threshold) before the power configuration is not completed, process  300  proceeds to step  312 , at which the negotiation request is declined. In this case, Rx  104  may resend the negotiation request for the same RP (at step  204 ) because the RP is lower than MAP. If the time lapse has not reached the threshold when power configuration is completed, process  300  proceeds to step  308 , at which the negotiation request is acknowledged. 
     In some embodiments, TX  102  may adjust the AP level, e.g., by configuring the power supply  112 , to improve the system efficiency, while still meeting the NP requirement, e.g., the adjusted AP is still sufficient to support the NP. 
     The various steps of process  200 , which are implemented at Rx  104 , and the various steps of process  300 , which are implemented at Tx  102 , may be implemented separately, concurrently, sequentially or intermittently. For example, after step  202  in process  200  is implemented at Rx  104 , process  300  can be implemented at Tx  102 . For another example, when step  304  is implemented at Tx  102 , step  208  of process  200  may be implemented concurrently. 
     The above detailed description is provided to illustrate specific embodiments of the present invention and is not intended to be limiting. Numerous variations and modifications within the scope of the present invention are possible. The present invention is set forth in the following claims.