Methods and systems for maximum power point transfer in receivers

[0001] This application is a continuation of U.S. patent application Ser. No. 14/584,869, filed on Dec. 29, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 14/272,207, filed on May 7, 2014, which are herein fully incorporated by reference in their entirety.

[0002] 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.

[0003] The present disclosure generally relates to wireless power transmission, and more specifically to a MPPT management method to effectively improve power extraction in receivers.

[0004] 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.

[0005] 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.

[0006] 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.

[0007] The present disclosure provides an MPPT management method for enabling a receiver to extract maximum power from RF waves.

[0008] 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.

[0009] 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.

[0010] 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.

[0017] 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.

[0018] As used here, the following terms may have the following definitions:

[0019] “Pocket-forming” refers to generating two or more RF waves that converge in 3-d space, forming controlled constructive and destructive interference patterns.

[0020] “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.

[0021] “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.

[0022] “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.

[0023] “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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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's power requirements.

[0035] 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.

[0036] 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).

[0037] 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.

[0038] Main system micro-controller 322 may monitor the voltage levels at the output of the main antenna array 302 using ADC node point 307.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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 P1, and a local power maximum 408 at P2.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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 P2 to global power maximum 406 P1, at step 510.

[0049] 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.

[0050] 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.

[0051] 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.