US20150326070A1 - Methods and Systems for Maximum Power Point Transfer in Receivers - Google Patents

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
• The present disclosure is related to U.S. non-provisional patent application DWV-3DPF-010 entitled “Methodology for Pocket-forming”; DWV-3DPF-015 entitled “Method for 3 Dimensional Pocket-forming”; DWV-3DPF-027 entitled “Receivers for Wireless Power Transmission”; DWV-3DPF-029 entitled “Transmitters for Wireless Power Transmission” invented by Michael Leabman, and ENG-SYHW-001 entitled “Enhanced Receiver for Wireless Power Transmission” invented by Jason Petras and Michael A. Leabman, each of which is incorporated by reference in its entirety herein
BACKGROUND
• 1. 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.
• 2. Background Information
• 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.
Definitions
• 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.
DESCRIPTION OF THE DRAWINGS
• FIG. 1 illustrates awireless power transmission100 using pocket-forming. Atransmitter102 may transmit controlled Radio Frequency (RF) waves, which may converge in 3-d space. TheseRF waves104 may be controlled through phase and/or relative amplitude adjustments to form constructive and destructive interference patterns (pocket-forming). Pockets ofenergy106 may be formed at constructive interference patterns and can be 3-dimensional in shape, while null-spaces may be generated at destructive interference patterns. Areceiver108 may then utilize pockets ofenergy106 produced by pocket-forming for charging or powering a cordlesselectronic device110, for example, a smartphone, a tablet, a laptop computer (as shown inFIG. 1), a music player, an electronic toy, and the like. In some embodiments, there can bemultiple transmitters102 and/ormultiple receivers108 for powering variouselectronic devices110 at the same time. In other embodiments, adaptive pocket-forming may be used to regulate the power transmitted toelectronic devices110.
• FIG. 2 illustrates the block diagram oftransmitter102, which may be used inwireless power transmission100.Transmitter102 may include ahousing202, at least two ormore antenna elements204, at least one RF integrated circuit (RFIC)206, at least one digital signal processor (DSP) or micro-controller208, and onecommunications component210.Housing202 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 elements204 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 part18 (Industrial, Scientific and Medical equipment).Antenna elements204 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 elements204 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 forantenna elements204 for controlling pocket-forming. These RF signals may be produced using apower source212 and a local oscillator chip (not shown) using a suitable piezoelectric material. Micro-controller208 may then process information sent byreceiver108 throughcommunications component210 for determining optimum times and locations for pocket-forming.Communications component210 may be based on standard wireless communication protocols, which may include Bluetooth, Wi-Fi or ZigBee. In addition,communications component210 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 component210 may be possible, including radar, infrared cameras or sound devices for sonic triangulation ofelectronic device110 position.
• FIG. 3 shows a block diagram ofreceiver configuration300 which can be used for wireless powering or charging one or moreelectronic devices110 as exemplified inwireless power transmission100. According to some aspects of this embodiment,receiver108 may operate with the variable power source generated from transmitted RF waves104 to deliver constant and stable power or energy toelectronic device110. In addition,receiver108 may use the variable power source generated fromRF waves104 to power up electronic components withinreceiver108 for proper operation.
• Receiver108 may be integrated inelectronic device110 and may include a housing (not shown inFIG. 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.
• Receiver108 may include anantenna array302 which may convertRF waves104 or pockets ofenergy106 into electrical power.Antenna array302 may include one ormore antenna elements304 coupled with one ormore rectifiers306. RF waves104 may exhibit a sinusoidal shape within a voltage amplitude and power range that may depend on characteristics oftransmitter102 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 byantenna array302 at thereceiver108 may be variable. As an illustrative embodiment, and not by way of limitation, the alternating current (AC) voltage or power generated byantenna element304 fromRF waves104 or pocket ofenergy106 may vary from about 0 volts or 0 watt to about 5 volts at 3 watts.
• Antenna element304 may include suitable antenna types for operating in frequency bands similar to the bands described fortransmitter102 fromFIG. 2.Antenna element304 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 exampleelectronic device110. 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 asreceiver108 may dynamically modify its antenna polarization to optimizewireless power transmission100.
• Rectifier306 may include diodes or resistors, inductors or capacitors to rectify the AC voltage generated byantenna element304 to direct current (DC) voltage.Rectifier306 may be placed as close as is technically possible toantenna element304 to minimize losses. In one embodiment,rectifier306 may operate in synchronous mode, in whichcase rectifier306 may include switching elements that may improve the efficiency of rectification. As an illustrative embodiment and not by way of limitationinput boost converter308 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 converter308 may reduce or eliminate rail-to-rail deviations and may operate as a step-up DC-to-DC converter to increase the voltage fromrectifier306 to a voltage level suitable for proper operation ofreceiver108. In one embodiment, intelligentinput boost converter308 may exhibit a synchronous topology to increase power conversion efficiency.
• As the voltage or power generated fromRF waves104 may be zero at some instants ofwireless power transmission100,receiver108 can include astorage element310 to store energy or electric charge from the output voltage produced byinput boost converter308. In this way,storage element310 may deliver a constant voltage or power to aload312 which may represent the battery or internal circuitry ofelectronic device110 requiring continuous powering or charging. For example, load312 may be the battery of a mobile phone requiring constant delivery of 5 volts at 2.5 watts.
• Storage element310 may include abattery314 to store power or electric charge from the voltage received frominput boost converter308.Battery314 may be of different types, including but not limited to, alkaline, nickel-cadmium (NiCd), nickel-metal hydride (NiHM), and lithium-ion, among others.Battery314 may exhibit shapes and dimensions suitable forfitting receiver108, while charging capacity and cell design ofbattery314 may depend onload312 requirements. For example, for charging or powering a mobile phone,battery314 may deliver a voltage from about 3 volts to about 4.2 volts.
• In another embodiment,storage element310 may include a capacitor (not shown inFIG. 3) instead ofbattery314 for storing and delivering electrical charge or power to load312. 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's power requirements.
• Receiver108 may also include anoutput boost converter316 operatively coupled withstorage element310 andinput boost converter308, where thisoutput boost converter316 may be used for matching impedance and power requirements ofload312. As an illustrative embodiment, and not by way of limitation,output boost converter316 may increase the output voltage ofbattery314 from about 3 or 4.2 volts to about 5 volts which may be the voltage required by thebattery314 or internal circuitry of a mobile phone. Similarly to inputboost converter308,output boost converter316 may be based on a synchronous topology for enhancing power conversion efficiency.
• Storage element310 may provide power or voltage to acommunication subsystem318 which may include a low-dropout regulator (LDO320), amain system micro-controller322, and an electrically erasable programmable read-only memory (EEPROM324).LDO320 may function as a DC linear voltage regulator to provide a steady voltage suitable for low energy applications as inmain system micro-controller322.Main system micro-controller322 may be operatively coupled withEEPROM324 to store data pertaining the operation and monitoring ofreceiver108.Main system micro-controller322 may also include a clock (CLK) input and general purpose inputs/outputs (GPIOs).
• In one embodiment, intelligentinput boost converter308 may include a built-in micro-controller (not shown inFIG. 3) operatively coupled with amain system micro-controller322. Themain system micro-controller322 may actively monitor the overall operation ofreceiver108 by taking one or more power measurements326 (ADC) at different nodes or sections as shown inFIG. 3. For example,main system micro-controller322 may measure how much voltage or power is being delivered atrectifier306,input boost converter308,battery314,output boost converter316,communication subsystem318, and/orload312.Main system micro-controller322 may communicate thesepower measurements326 to load312 so thatelectronic device110 may know how much power it can pull fromreceiver108. In another embodiment,main system micro-controller322, based onpower measurements326, may control the power or voltage delivered atload312 by adjusting the load current limits atoutput boost converter316.
• Main system micro-controller322 may monitor the voltage levels at the output of themain antenna array302 usingADC node point307.
• In another embodiment,main system micro-controller322 may regulate how power or energy can be drained fromstorage element310 based on the monitoring ofpower measurements326. For example, if the power or voltage atinput boost converter308 runs too low, thenmain system micro-controller322 may directoutput boost converter316 to drainbattery314 for poweringload312.
• Yet in another embodiment,receiver108 may have a dedicatedantenna element330 operatively coupled with acorresponding rectifier332, where thesededicated antenna element330 andrectifier332 may be used for continuously monitoring the surrounding pocket ofenergy106. Thisdedicated antenna element330 may be separate from themain antenna array302. More specifically, themain system micro-controller322 may measure power level atADC node point334 to compare against actual DC power levels extracted from thereceiver108 system.
• Receiver108 may include aswitch328 for resuming or interrupting power being delivered atload312. In one embodiment,main system micro-controller322 may control the operation ofswitch328 according to terms of services contracted by one or more users ofwireless power transmission100 or according to administrator policies.
• FIG. 4 illustrates agraph400, 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 curve402 that may be obtained fromreceiver108 operation and which may vary according to the characteristics ofreceiver108.FIG. 4 also shows acorresponding power curve404 which may represent the power available (current x voltage) from themain antenna array302.
• In one embodiment, voltage levels measured atADC node point307 may not necessarily exhibit a linear relationship with the available current from themain antenna array302. Thus,power curve404 may have multiple local peaks, including aglobal power maximum406 at P1, and alocal power maximum408 at P2.
• The MPPT algorithm running in theinput boost converter308 may continuously track for aglobal power maximum406 ingraph400, so thatinput boost converter308 may be able to extract the maximum amount of power fromantenna array302. However, in some circumstances, the MPPT algorithm may be stuck at alocal power maximum408 which may not correspond to theglobal power maximum406 ingraph400. When operating at alocal power maximum408, intelligentinput boost converter308 may not be able to maximize the amount of power that can be extracted fromantenna array302.
• It may be an object of embodiments described herein to adjust the MPPT algorithm to control the operation of intelligentinput boost converter308 so that it can continuously operate atglobal power maximum406 to make the best use of the power that can be extracted fromantenna array302 inreceiver108 system.
• FIG. 5 shows aMPPT management method500 that may be used for maximizing the amount of power that can be extracted fromantenna array302 to deliver continuous and suitable power toreceiver108.
• At monitoringstep502, the built-in micro-controller in the intelligentinput boost converter308 may monitor voltage fromantenna array302 and search for aglobal power maximum406 orlocal power maximum408.
• Atstep504, themain system micro-controller322 may read the result from theinput boost converter308 or useADC node point307 to establish theinput boost converter308 current operational MPPT. Subsequently, atstep506, themain system micro-controller322 may read the voltage ofdedicated antenna element330 atADC node point334. Atstep508, the combination of theinput boost converter308 MPP and the output value of dedicatedantenna element330 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 theinput boost converter308 MPPT algorithm. Once action is determined, themain system micro-controller322 may adjust the MPPT algorithm executed byinput boost converter308, thus moving the operation ofinput boost converter308 fromlocal power maximum408 P2 toglobal power maximum406 P1, atstep510.
• The predefined MPPT tables may include a characterization of a plurality ofreceivers108 in terms of ability to extract power from a particular field. For example, the capability ofreceiver108 for extracting power fromRF waves104 may vary according to the configuration ofantenna array302. In one embodiment, these MPPT tables may be determined by laboratory measurements ofdifferent receivers108 in a way that aparticular receiver108 may be mapped to an optimal MPPT.
• In one embodiment,main system micro-controller322 may use the information contained in MPPT tables to provide initial conditions for running an optimal MPPT at intelligentinput boost converter308 according to the specific characteristics or configuration ofreceiver108.
• 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.

Claims (20)

What is claimed is:

1. A receiver, comprising:

a first antenna element for receiving wireless signals comprising energy resulting from constructive interference patterns of radio-frequency (RF) waves;

a first rectifier, operatively coupled to the antenna element for converting the energy received by the first antenna element;

a second antenna element for receiving wireless signals comprising energy resulting from constructive interference patterns of RF waves;

a second rectifier, operatively coupled to the second antenna element for converting the energy received by the second antenna element;

an input boost converter, operatively coupled to the first rectifier, the input boost converter being configured to step up the energy converted by the first rectifier and to determine at least one of (i) a global power maximum and (ii) a local power maximum produced in the first rectifier;

a controller, operatively coupled to the input boost converter and the second rectifier, wherein the controller is configured to

determine available energy at the second rectifier,

determine at least one maximum power point (MPP) value from the first rectifier, and

transmit an operational instruction to the first rectifier to further step up the energy converted by the first rectifier

2. The receiver ofclaim 1, wherein the input boost converter comprises a microcontroller operatively coupled to the controller.

3. The receiver ofclaim 1, wherein the operational instruction comprises data for configuring the input boost converter to further step up the energy to the global power maximum.

4. The receiver ofclaim 1, wherein the controller is further configured to index a combination of the determined available energy and at least one MPP value in a look-up table.

5. The receiver ofclaim 1, wherein the controller is configured to compare the available energy at the second rectifier to the at least one maximum power point (MPP) value from the first rectifier to determine the operational instruction.

6. The receiver ofclaim 1, further comprising an output boost converter, wherein the controller is configured to process and determine load requirements for the receiver and control operation of the input boost converter and output boost converter based on the determined load requirements.

7. The receiver ofclaim 1, further comprising a storage element, operatively coupled to the input boost converter, the storage element being configured to receive and store at least a portion of the energy from the input boost converter;

8. The receiver ofclaim 1, wherein the controller comprises a communication portion, the controller being further configured to measure voltage from at least one of (i) the rectifier, (ii) the input boost converter, (iii) the storage element, and (iv) the output boost converter, wherein the controller is configured to communicate, via the communication portion, the measurements to a load.

9. The receiver ofclaim 1, wherein the controller is configured to control operation of the output boost converter by adjusting load current limits at the output boost converter.

10. A method for operating a receiver, comprising:

receiving, in a first antenna element, wireless signals comprising energy resulting from constructive interference patterns of radio-frequency (RF) waves;

converting the energy received by the first antenna element in a first rectifier;

receiving, in a second antenna element, wireless signals comprising energy resulting from constructive interference patterns of RF waves;

converting the energy received by the second antenna element in a second rectifier;

stepping up the energy converted by the first rectifier via an input boost converter and determining in the input boost converter at least one of (i) a global power maximum and (ii) a local power maximum produced in the first rectifier;

determining available energy at the second rectifier via a controller,

determining at least one maximum power point (MPP) value from the first rectifier via the controller, and

transmitting an operational instruction from the controller to the first rectifier to further step up the energy converted by the first rectifier

11. The method ofclaim 10, wherein the input boost converter comprises a microcontroller operatively coupled to the controller.

12. The method ofclaim 10, wherein the operational instruction comprises data for configuring the input boost converter to further step up the energy to the global power maximum.

13. The method ofclaim 10, further comprising the steps of indexing a combination of the determined available energy and at least one MPP value in a look-up table via the controller.

14. The method ofclaim 10, further comprising the steps of comparing, via the controller, the available energy at the second rectifier to the at least one maximum power point (MPP) value from the first rectifier to determine the operational instruction.

15. A receiver comprising a plurality of antenna elements for receiving wireless signals comprising energy resulting from constructive interference patterns of radio-frequency (RF) waves, and a respective plurality of rectifiers configured to convert the energy received by each of the antenna elements, the receiver comprising:

an input boost converter, operatively coupled to a first of the plurality of rectifiers, the input boost converter being configured to step up the energy converted by the first rectifier and to determine at least one of (i) a global power maximum and (ii) a local power maximum produced in the first rectifier;

a controller, operatively coupled to the input boost converter and a second of the plurality of rectifiers, wherein the controller is configured to

determine available energy at the second rectifier,

determine at least one maximum power point (MPP) value from the first rectifier, and

transmit an operational instruction to the first rectifier to further step up the energy converted by the first rectifier

16. The receiver ofclaim 15, wherein the input boost converter comprises a microcontroller operatively coupled to the controller.

17. The receiver ofclaim 15, wherein the operational instruction comprises data for configuring the input boost converter to further step up the energy to the global power maximum.

18. The receiver ofclaim 15, wherein the controller is further configured to index a combination of the determined available energy and at least one MPP value in a look-up table.

19. The receiver ofclaim 15, wherein the controller is configured to compare the available energy at the second rectifier to the at least one maximum power point (MPP) value from the first rectifier to determine the operational instruction.

20. The receiver ofclaim 15, further comprising an output boost converter, wherein the controller is configured to process and determine load requirements for the receiver and control operation of the input boost converter and output boost converter based on the determined load requirements.

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