Abstract:
A MPPT management method in a receiver used for wireless power transmission may include the monitoring of the power extracted from RF waves at a dedicated antenna element in the receiver; detecting MPPT at an intelligent input boost converter in the receiver; comparing the detected MPPT with MPPT tables stored or calculated within a main system micro-controller in the receiver; adjusting the MPPT at the intelligent boost converter to find a suitable maximum peak that may enable an optimal power extraction from RF waves.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 14/272,207, filed on May 7, 2014, which is herein fully incorporated by reference in its entirety for all purposes. 
     This application is related to U.S. patent application Ser. No. 13/891,430, filed on May 10, 2013; U.S. patent application Ser. No. 13/946,082, filed on Jul. 19, 2013; U.S. patent application Ser. No. 13/891,399, filed on May 10, 2013; U.S. patent application Ser. No. 13/891,445, filed on May 10, 2013; and U.S. patent application Ser. No. 14/272,179, filed on May 7, 2014; U.S. Non-Provisional patent application Ser. No. 14/583,625, filed Dec. 27, 2014, entitled “Receivers for Wireless Power Transmission,” U.S. Non-Provisional patent application Ser. No. 14/583,630, filed Dec. 27, 2014, entitled “Methodology for Pocket-Forming,” U.S. Non-Provisional patent application Ser. No. 14/583,634, filed Dec. 27, 2014, entitled “Transmitters for Wireless Power Transmission,” U.S. Non-Provisional patent application Ser. No. 14/583,640, filed Dec. 27, 2014, entitled “Methodology for Multiple Pocket-Forming,” U.S. Non-Provisional patent application Ser. No. 14/583,641, filed Dec. 27, 2014, entitled “Wireless Power Transmission with Selective Range,” U.S. Non-Provisional patent application Ser. No. 14/583,643, filed Dec. 27, 2014, entitled “Method for 3 Dimensional Pocket-Forming,” all of which are incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure generally relates to wireless power transmission, and more specifically to a MPPT management method to effectively improve power extraction in receivers. 
     BACKGROUND 
     Wireless power transmission may be based on the extraction and conversion of power or energy from transmitted RF waves. One challenge that may be present during wireless power transmission is that power or energy extracted from RF waves may be variable due to inherent characteristics of the medium and environment. Moreover, the power that can be extracted from RF waves may be zero at some instances of the wireless power transmission. The variability of the power extracted from RF waves may be fueled by interference produced by electronic devices, walls, metallic objects, and electromagnetic signals, among others. 
     In order to extract suitable power from RF waves, it may be desirable that a receiver may work as close as possible to maximum points or peaks, despite the fact that external conditions may alter the transmission of RF waves. 
     According to the foregoing, there may be a need to provide a method and/or system for managing maximum power point tracking (MPPT) in a receiver capable of operating with a variable power source derived from RF waves for powering and/or charging the batteries for a plurality of electronic devices. 
     SUMMARY 
     The present disclosure provides an MPPT management method for enabling a receiver to extract maximum power from RF waves. 
     The receiver may include components that may be required for the efficient wireless power transmission. In one embodiment, the receiver system may include an intelligent input boost converter with a built-in micro-controller operatively coupled with a main micro-controller to deliver continuous and suitable power or voltage to a load. The receiver may also include a dedicated antenna for measuring the power received from RF waves. 
     According to the disclosed MPPT management method, the built-in micro-controller in the input boost converter may monitor the voltage levels received at the main antenna array. Consequently, the built-in micro-controller may detect the maximum power point by increasing or decreasing the current it is taking from the main antenna array until it has found a local power maximum. The built-in micro-controller in the intelligent input boost converter may send this MPPT data to the main system micro-controller, which may compare the measured MPPT data with MPPT tables residing in the memory of main system micro-controller or use it for further computation in algorithms located within the software of the main system micro-controller. The result from the tables or algorithms may be used for adjusting the MPPT executed in the intelligent input boost converter for maximizing power extraction from received RF waves. 
     Numerous other aspects, features, and benefits of the present disclosure may be made apparent from the following detailed description taken together with the drawing figures, which may illustrate the embodiments of the present disclosure, incorporated herein for reference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure can be better understood by referring to the following figures. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the disclosure. In the figures, reference numerals designate corresponding parts throughout the different views. 
         FIG. 1  illustrates wireless power transmission using pocket forming, according to an embodiment. 
         FIG. 2  illustrates a block diagram of a wireless power transmitter, which may be used in wireless power transmission, according to an embodiment. 
         FIG. 3  depicts a block diagram of wireless power receiver configuration that may be used for extracting and converting power from transmitted RF waves, according to an embodiment. 
         FIG. 4  illustrates the MPPT of characteristic curves, which may be used to change the voltage direction and adjust the operation of the receiver, according to an embodiment. 
         FIG. 5  shows a flowchart for the method enabled by the proprietary MPPT algorithm controlling maximum power point transfer and operation of the input boost converter, according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure is here described in detail with reference to embodiments illustrated in the drawings, which form a part here. Other embodiments may be used and/or other changes may be made without departing from the spirit or scope of the present disclosure. The illustrative embodiments described in the detailed description are not meant to be limiting of the subject matter presented here. 
     As used here, the following terms may have the following definitions: 
     “Pocket-forming” refers to generating two or more RF waves that converge in 3-d space, forming controlled constructive and destructive interference patterns. 
     “Pockets of energy” refers to areas or regions of space where energy or power may accumulate in the form of constructive interference patterns of RF waves. 
     “Transmitter” refers to a device, including a chip which may generate two or more RF signals, at least one RF signal being phase shifted and gain adjusted with respect to other RF signals, substantially all of which pass through one or more RF antenna such that focused RF signals are directed to a target. 
     “Receiver” refers to a device which may include at least one antenna, at least one rectifying circuit, at least one input boost converter, at least one storage element, at least one output boost converter, at least one switch, and at least one communication subsystem for powering or charging an electronic device using RF waves. 
     “MPPT or Maximum Power Point Tracking” refers to an algorithm included in micro-controllers of a receiver for extracting maximum available power from RF waves. 
       FIG. 1  illustrates a wireless power transmission  100  using pocket-forming. A transmitter  102  may transmit controlled Radio Frequency (RF) waves, which may converge in 3-d space. These RF waves  104  may be controlled through phase and/or relative amplitude adjustments to form constructive and destructive interference patterns (pocket-forming). Pockets of energy  106  may be formed at constructive interference patterns and can be 3-dimensional in shape, while null-spaces may be generated at destructive interference patterns. A receiver  108  may then utilize pockets of energy  106  produced by pocket-forming for charging or powering a cordless electronic device  110 , for example, a smartphone, a tablet, a laptop computer (as shown in  FIG. 1 ), a music player, an electronic toy, and the like. In some embodiments, there can be multiple transmitters  102  and/or multiple receivers  108  for powering various electronic devices  110  at the same time. In other embodiments, adaptive pocket-forming may be used to regulate the power transmitted to electronic devices  110 . 
       FIG. 2  illustrates the block diagram of transmitter  102 , which may be used in wireless power transmission  100 . Transmitter  102  may include a housing  202 , at least two or more antenna elements  204 , at least one RF integrated circuit (RFIC)  206 , at least one digital signal processor (DSP) or micro-controller  208 , and one communications component  210 . Housing  202  can be made of any suitable material which may allow for signal or wave transmission and/or reception, for example plastic or hard rubber. Antenna elements  204  may include suitable antenna types for operating in frequency bands such as 900 MHz, 2.5 GHz or 5.8 GHz as these frequency bands conform to Federal Communications Commission (FCC) regulations part  18  (Industrial, Scientific and Medical equipment). Antenna elements  204  may include vertical or horizontal polarization, right hand or left hand polarization, elliptical polarization, or other suitable polarizations as well as suitable polarization combinations. Suitable antenna types may include, for example, patch antennas with heights from about ⅛ inch to about 8 inches and widths from about ⅛ inch to about 6 inches. Other antenna elements  204  types that can be used include meta-materials based antennas, dipole antennas, and planar inverted-F antennas (PIFAs), among others. 
     RF integrated circuit (RFIC)  206  may include a proprietary chip for adjusting phases and/or relative magnitudes of RF signals, which may serve as inputs for antenna elements  204  for controlling pocket-forming. These RF signals may be produced using a power source  212  and a local oscillator chip (not shown) using a suitable piezoelectric material. Micro-controller  208  may then process information sent by receiver  108  through communications component  210  for determining optimum times and locations for pocket-forming. Communications component  210  may be based on standard wireless communication protocols, which may include Bluetooth, Wi-Fi or ZigBee. In addition, communications component  210  may be used to transfer other information such as an identifier for the device or user, battery level, location or other such information. Other communications component  210  may be possible, including radar, infrared cameras or sound devices for sonic triangulation of electronic device  110  position. 
       FIG. 3  shows a block diagram of receiver configuration  300  which can be used for wireless powering or charging one or more electronic devices  110  as exemplified in wireless power transmission  100 . According to some aspects of this embodiment, receiver  108  may operate with the variable power source generated from transmitted RF waves  104  to deliver constant and stable power or energy to electronic device  110 . In addition, receiver  108  may use the variable power source generated from RF waves  104  to power up electronic components within receiver  108  for proper operation. 
     Receiver  108  may be integrated in electronic device  110  and may include a housing (not shown in  FIG. 3 ) that can be made of any suitable material to allow for signal or wave transmission and/or reception, for example plastic or hard rubber. This housing may be an external hardware that may be added to different electronic equipment, for example in the form of cases, or can be embedded within electronic equipment as well. 
     Receiver  108  may include an antenna array  302  which may convert RF waves  104  or pockets of energy  106  into electrical power. Antenna array  302  may include one or more antenna elements  304  coupled with one or more rectifiers  306 . RF waves  104  may exhibit a sinusoidal shape within a voltage amplitude and power range that may depend on characteristics of transmitter  102  and the environment of transmission. The environment of transmission may be affected by changes to or movement of objects within the physical boundaries, or movement of the boundaries themselves. It is also affected by changes to the medium of transmission; for example, changes to air temperature or humidity. As a result, the voltage or power generated by antenna array  302  at the receiver  108  may be variable. As an illustrative embodiment, and not by way of limitation, the alternating current (AC) voltage or power generated by antenna element  304  from RF waves  104  or pocket of energy  106  may vary from about 0 volts or 0 watt to about 5 volts at 3 watts. 
     Antenna element  304  may include suitable antenna types for operating in frequency bands similar to the bands described for transmitter  102  from  FIG. 2 . Antenna element  304  may include vertical or horizontal polarization, right hand or left hand polarization, elliptical polarization, or other suitable polarizations as well as suitable polarization combinations. Using multiple polarizations can be beneficial in devices where there may not be a preferred orientation during usage or whose orientation may vary continuously through time, for example electronic device  110 . On the contrary, for devices with well-defined orientations, for example a two-handed video game controller, there might be a preferred polarization for antennas which may dictate a ratio for the number of antennas of a given polarization. Suitable antenna types may include patch antennas with heights from about ⅛ inch to about 6 inches and widths from about ⅛ inch to about 6 inches. Patch antennas may have the advantage that polarization may depend on connectivity, i.e. depending on which side the patch is fed, the polarization may change. This may further prove advantageous as receiver  108  may dynamically modify its antenna polarization to optimize wireless power transmission  100 . 
     Rectifier  306  may include diodes or resistors, inductors or capacitors to rectify the AC voltage generated by antenna element  304  to direct current (DC) voltage. Rectifier  306  may be placed as close as is technically possible to antenna element  304  to minimize losses. In one embodiment, rectifier  306  may operate in synchronous mode, in which case rectifier  306  may include switching elements that may improve the efficiency of rectification. As an illustrative embodiment and not by way of limitation input boost converter  308  may operate with input voltages of at least 0.6 volts to about 5 volts to produce an output voltage of about 5 volts. In addition, input boost converter  308  may reduce or eliminate rail-to-rail deviations and may operate as a step-up DC-to-DC converter to increase the voltage from rectifier  306  to a voltage level suitable for proper operation of receiver  108 . In one embodiment, intelligent input boost converter  308  may exhibit a synchronous topology to increase power conversion efficiency. 
     As the voltage or power generated from RF waves  104  may be zero at some instants of wireless power transmission  100 , receiver  108  can include a storage element  310  to store energy or electric charge from the output voltage produced by input boost converter  308 . In this way, storage element  310  may deliver a constant voltage or power to a load  312  which may represent the battery or internal circuitry of electronic device  110  requiring continuous powering or charging. For example, load  312  may be the battery of a mobile phone requiring constant delivery of 5 volts at 2.5 watts. 
     Storage element  310  may include a battery  314  to store power or electric charge from the voltage received from input boost converter  308 . Battery  314  may be of different types, including but not limited to, alkaline, nickel-cadmium (NiCd), nickel-metal hydride (NiHM), and lithium-ion, among others. Battery  314  may exhibit shapes and dimensions suitable for fitting receiver  108 , while charging capacity and cell design of battery  314  may depend on load  312  requirements. For example, for charging or powering a mobile phone, battery  314  may deliver a voltage from about 3 volts to about 4.2 volts. 
     In another embodiment, storage element  310  may include a capacitor (not shown in  FIG. 3 ) instead of battery  314  for storing and delivering electrical charge or power to load  312 . As a way of example, in the case of charging or power a mobile phone, receiver may include a capacitor with operational parameters matching the load device&#39;s power requirements. 
     Receiver  108  may also include an output boost converter  316  operatively coupled with storage element  310  and input boost converter  308 , where this output boost converter  316  may be used for matching impedance and power requirements of load  312 . As an illustrative embodiment, and not by way of limitation, output boost converter  316  may increase the output voltage of battery  314  from about 3 or 4.2 volts to about 5 volts which may be the voltage required by the battery  314  or internal circuitry of a mobile phone. Similarly to input boost converter  308 , output boost converter  316  may be based on a synchronous topology for enhancing power conversion efficiency. 
     Storage element  310  may provide power or voltage to a communication subsystem  318  which may include a low-dropout regulator (LDO  320 ), a main system micro-controller  322 , and an electrically erasable programmable read-only memory (EEPROM  324 ). LDO  320  may function as a DC linear voltage regulator to provide a steady voltage suitable for low energy applications as in main system micro-controller  322 . Main system micro-controller  322  may be operatively coupled with EEPROM  324  to store data pertaining the operation and monitoring of receiver  108 . Main system micro-controller  322  may also include a clock (CLK) input and general purpose inputs/outputs (GPIOs). 
     In one embodiment, intelligent input boost converter  308  may include a built-in micro-controller (not shown in  FIG. 3 ) operatively coupled with a main system micro-controller  322 . The main system micro-controller  322  may actively monitor the overall operation of receiver  108  by taking one or more power measurements  326  (ADC) at different nodes or sections as shown in  FIG. 3 . For example, main system micro-controller  322  may measure how much voltage or power is being delivered at rectifier  306 , input boost converter  308 , battery  314 , output boost converter  316 , communication subsystem  318 , and/or load  312 . Main system micro-controller  322  may communicate these power measurements  326  to load  312  so that electronic device  110  may know how much power it can pull from receiver  108 . In another embodiment, main system micro-controller  322 , based on power measurements  326 , may control the power or voltage delivered at load  312  by adjusting the load current limits at output boost converter  316 . 
     Main system micro-controller  322  may monitor the voltage levels at the output of the main antenna array  302  using ADC node point  307 . 
     In another embodiment, main system micro-controller  322  may regulate how power or energy can be drained from storage element  310  based on the monitoring of power measurements  326 . For example, if the power or voltage at input boost converter  308  runs too low, then main system micro-controller  322  may direct output boost converter  316  to drain battery  314  for powering load  312 . 
     Yet in another embodiment, receiver  108  may have a dedicated antenna element  330  operatively coupled with a corresponding rectifier  332 , where these dedicated antenna element  330  and rectifier  332  may be used for continuously monitoring the surrounding pocket of energy  106 . This dedicated antenna element  330  may be separate from the main antenna array  302 . More specifically, the main system micro-controller  322  may measure power level at ADC node point  334  to compare against actual DC power levels extracted from the receiver  108  system. 
     Receiver  108  may include a switch  328  for resuming or interrupting power being delivered at load  312 . In one embodiment, main system micro-controller  322  may control the operation of switch  328  according to terms of services contracted by one or more users of wireless power transmission  100  or according to administrator policies. 
       FIG. 4  illustrates a graph  400 , depicting the intensity (I) of current available from main antenna array, (P) the power available from main antenna array, and (V) the voltage from main antenna array.  FIG. 4  shows a current-to-voltage curve  402  that may be obtained from receiver  108  operation and which may vary according to the characteristics of receiver  108 .  FIG. 4  also shows a corresponding power curve  404  which may represent the power available (current×voltage) from the main antenna array  302 . 
     In one embodiment, voltage levels measured at ADC node point  307  may not necessarily exhibit a linear relationship with the available current from the main antenna array  302 . Thus, power curve  404  may have multiple local peaks, including a global power maximum  406  at P 1 , and a local power maximum  408  at P 2 . 
     The MPPT algorithm running in the input boost converter  308  may continuously track for a global power maximum  406  in graph  400 , so that input boost converter  308  may be able to extract the maximum amount of power from antenna array  302 . However, in some circumstances, the MPPT algorithm may be stuck at a local power maximum  408  which may not correspond to the global power maximum  406  in graph  400 . When operating at a local power maximum  408 , intelligent input boost converter  308  may not be able to maximize the amount of power that can be extracted from antenna array  302 . 
     It may be an object of embodiments described herein to adjust the MPPT algorithm to control the operation of intelligent input boost converter  308  so that it can continuously operate at global power maximum  406  to make the best use of the power that can be extracted from antenna array  302  in receiver  108  system. 
       FIG. 5  shows a MPPT management method  500  that may be used for maximizing the amount of power that can be extracted from antenna array  302  to deliver continuous and suitable power to receiver  108 . 
     At monitoring step  502 , the built-in micro-controller in the intelligent input boost converter  308  may monitor voltage from antenna array  302  and search for a global power maximum  406  or local power maximum  408 . 
     At step  504 , the main system micro-controller  322  may read the result from the input boost converter  308  or use ADC node point  307  to establish the input boost converter  308  current operational MPPT. Subsequently, at step  506 , the main system micro-controller  322  may read the voltage of dedicated antenna element  330  at ADC node point  334 . At step  508 , the combination of the input boost converter  308  MPP and the output value of dedicated antenna element  330  may be used to either index a predefined look-up table or be used in an algorithm. This result may or may not require an adjustment of the operational input parameters of the input boost converter  308  MPPT algorithm. Once action is determined, the main system micro-controller  322  may adjust the MPPT algorithm executed by input boost converter  308 , thus moving the operation of input boost converter  308  from local power maximum  408  P 2  to global power maximum  406  P 1 , at step  510 . 
     The predefined MPPT tables may include a characterization of a plurality of receivers  108  in terms of ability to extract power from a particular field. For example, the capability of receiver  108  for extracting power from RF waves  104  may vary according to the configuration of antenna array  302 . In one embodiment, these MPPT tables may be determined by laboratory measurements of different receivers  108  in a way that a particular receiver  108  may be mapped to an optimal MPPT. 
     In one embodiment, main system micro-controller  322  may use the information contained in MPPT tables to provide initial conditions for running an optimal MPPT at intelligent input boost converter  308  according to the specific characteristics or configuration of receiver  108 . 
     While various aspects and embodiments have been disclosed, other aspects and embodiments may be contemplated. The various aspects and embodiments disclosed here are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.