Wireless power receiver circuit and method for providing constant voltage or current to an electrical load

Abstract

A wireless power receiver circuit and method for use in a wireless power transmission system is provided to provide a constant current or voltage to an electrical load, depending on whether a constant current or a constant voltage is required. The wireless power receiver circuit is configured to turn off the resonant response of the receiver circuit when the load does not require electrical power to reduce power consumption and avoid unnecessary heat dissipation. In addition, the switching device of the wireless power receiver circuit for turning off the resonant response can operate at a relatively low frequency and, therefore, can be implemented using relatively low-speed, relatively inexpensive components.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. non-provisional application serial number 16 / 023,925, filed on June 29, 2018, entitled “WIRELESS POWER RECEIVER CIRCUITS THAT PROVIDE CONSTANT VOLTAGE OR CURRENT TO AN ELECTRICALLOAD, AND METHODS,” the entire contents of which are incorporated herein by reference. This application also claims priority to UK patent application serial number 1812900.7, filed on August 8, 2018, entitled “WIRELESS POWER RECEIVER CIRCUITS THAT PROVIDE CONSTANT VOLTAGE OR CURRENT TO AN ELECTRICAL LOAD, AND METHODS,” the entire contents of which are incorporated herein by reference.

[0003] The subject matter of this application is related to the subject matter disclosed in U.S. patent application No. 15 / 296,704, filed on October 18, 2016, entitled “Wireless Power Transfer To Multiple Receiver Devices Across A Variable-Sized Area,” and is related to the subject matter disclosed in U.S. patent application No. 15 / 644,802, filed on July 9, 2017, entitled “Integrated Power Transmitter for Wireless Power Transfer,” the entire contents of both U.S. patent applications are incorporated herein by reference. Background Art

[0004] Wireless power transmission is the transfer of electrical energy from a power source to an electrical load without the use of artificial conductors to connect the power source and the electrical load. A wireless power transmission system includes a transmitter and one or more receiver devices. The transmitter is electrically coupled to the power source and converts the power into a time-varying electromagnetic (EM) field. One or more receiver devices receive the power via the EM field and convert the received power back into current for use by an electrical load that is part of or electrically coupled to the receiver device.

[0005] The receiver device is configured to resonate at a characteristic frequency at which the transmitter is operating in order to receive power from the near EM field. The receiver device converts the received power from the near EM field into an electric current which can then be used to power an electrical load which is part of or electrically coupled to the receiver device.

[0006] One of the difficulties associated with current receiver devices used in wireless power transfer systems is ensuring that a constant voltage or current is provided to an electrical load, depending on whether a constant voltage or current is required. Another difficulty associated with current receiver devices used in wireless power transfer systems is the lack of a mechanism for turning off the resonant response of the receiver device when the load does not require electrical power. If the resonant response is not turned off when power is not required, the receiver device will waste power and dissipate heat as long as the load does not use a significant portion of the available power. In known receiver devices that provide a mechanism for turning off the resonant response, the mechanism typically includes a high speed switching circuit implemented using expensive high speed components.

[0007] A receiver device for use in a wireless power transmission system is needed, which can provide a constant current or voltage to a load depending on whether a constant current or voltage is required. A receiver device for use in a wireless power transmission system is needed, which can turn off the resonant response when the load does not need electrical power to reduce power consumption and avoid unnecessary heat dissipation. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Many aspects of the present disclosure may be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, but emphasis is placed on clearly illustrating the principles of the present disclosure. Moreover, in the drawings, the same reference numerals represent corresponding parts in several views.

[0009] Figure 1 is a block diagram of a wireless power receiver circuit that may be used to wirelessly receive power in a wireless power transfer system, according to a representative embodiment.

[0010] Figure 2is a schematic diagram of a wireless power receiver circuit according to a representative embodiment, which can be used to wirelessly receive power in a wireless power transfer system.

[0011] Figure 3 is a function of time Figure 2 The graph of the voltage across capacitor C1 shown in FIG. 1 shows that once the RF voltage across capacitor C1 reaches a high enough amplitude to begin to Figure 1 The rectifier diode D1 of the receiver circuit shown is forward biased and the receiver circuit enters a charging period.

[0012] Figure 4 is a function of time Figure 2 A graph of the voltage across the load of a receiver circuit is shown.

[0013] Figure 5 is a schematic diagram of a wireless power receiver circuit according to a representative embodiment, which can be used to wirelessly receive power in a wireless power transfer system.

[0014] Figure 6 is a function of time Figure 5 A graph of the voltage across capacitor C1.

[0015] Figure 7 is a schematic diagram of a wireless power receiver circuit according to another representative embodiment, which can be used to wirelessly receive power in a wireless power transmission system.

[0016] Figure 8 is a schematic diagram of a wireless power receiver circuit that provides a constant DC current to a load of the wireless power receiver circuit according to a representative embodiment.

[0017] Fig. 9 is a schematic diagram of a wireless power receiver circuit that provides a constant DC current to a load of the wireless power receiver circuit according to a representative embodiment.

[0018] Fig.10 is a schematic diagram of a wireless power receiver circuit that provides a constant DC current to a load of the wireless power receiver circuit according to a representative embodiment.

[0019] Fig.11 is a schematic diagram of a wireless power receiver circuit according to a representative embodiment, which can be used to wirelessly receive power in a wireless power transfer system and uses an n-channel MOSFET transistor as an electrically controllable switch for shutting down the resonant response of the receiver circuit.

[0020] Fig.12 is a schematic diagram of a wireless power receiver circuit according to a representative embodiment, which can be used to wirelessly receive power in a wireless power transfer system and uses an n-channel MOSFET transistor as an electrically controllable switch for shutting down the resonant response of the receiver circuit.

[0021] Fig.13 is a schematic diagram of a wireless power receiver circuit according to a representative embodiment, which can be used to wirelessly receive power in a wireless power transfer system and uses an n-channel MOSFET transistor as an electrically controllable switch for shutting down the resonant response of the receiver circuit.

[0022] Fig.14 is a schematic diagram of a wireless power receiver circuit according to a representative embodiment, which can be used to wirelessly receive power in a wireless power transfer system and includes a rechargeable battery or electrochemical battery.

[0023] Fig.15 is a schematic diagram of a wireless power receiver circuit according to a representative embodiment, which can be used to wirelessly receive power in a wireless power transfer system and includes a rechargeable battery or electrochemical battery.

[0024] Fig.16 is a schematic diagram of a wireless power receiver circuit according to a representative embodiment, which can be used to wirelessly receive power in a wireless power transmission system and includes a low-pass RC circuit, which includes a resistor R3 and a capacitor C4, for reducing ripple in a load voltage.

[0025] Fig.17 is a schematic diagram of a wireless power PWM receiver circuit according to a representative embodiment, which can be used to wirelessly receive power in a wireless power transmission system and includes a low-pass LC circuit, which includes an inductor L2 and a capacitor C4, for reducing ripple in a load voltage.

[0026] Fig.18 is a schematic diagram of a wireless power receiver circuit according to a representative embodiment, which can be used to wirelessly receive power in a wireless power transmission system and includes a linear regulator IC2 for reducing ripple in a load voltage.

[0027] Fig.19is a schematic diagram of a wireless power PWM receiver circuit according to a representative embodiment, which wireless power PWM receiver circuit can be used to wirelessly receive power in a wireless power transmission system and includes a control circuit that is configured to shut down an LC tank of the receiver circuit at certain times or based on certain conditions.

[0028] Fig. 20 is a schematic diagram of a wireless power receiver circuit for use in a wireless power transfer system according to another representative embodiment, and the wireless power receiver circuit includes a thermal fuse or switch that prevents an LC energy tank of the receiver circuit from receiving power when the temperature exceeds a predetermined threshold.

[0029] Fig.21 is a schematic diagram of a wireless power receiver circuit for use in a wireless power transmission system according to another representative embodiment, and the wireless power receiver circuit includes a user-controllable switch that can be turned on and off by a user to allow the user to activate and deactivate the receiver circuit. DETAILED DESCRIPTION

[0030] According to the representative embodiments described herein, a wireless power receiver circuit for use in a wireless power transmission system is provided, which provides a constant current or voltage to an electrical load depending on whether a constant current or voltage is required. The wireless power receiver circuit is configured to turn off the resonant response when the load does not need electrical power to reduce power consumption and avoid unnecessary heat dissipation. In addition, the switching device of the wireless power receiver circuit for turning off the resonant response can operate at a relatively low frequency. Therefore, the switching device can be implemented at a relatively low cost using relatively low-speed, inexpensive components.

[0031] Exemplary or representative embodiments will now be described with reference to the accompanying drawings, wherein the same reference numerals represent the same components, elements or features. It should be noted that the features, elements or components in the accompanying drawings are not intended to be drawn to scale, but rather to focus on demonstrating the inventive principles and concepts.

[0032] In the following detailed description, for the purpose of explanation rather than limitation, exemplary or representative embodiments that disclose specific details are set forth in order to provide a thorough understanding of the principles and concepts of the invention. However, it is apparent to those of ordinary skill in the art who benefit from this disclosure that other embodiments according to the present teachings that are not explicitly described or shown herein fall within the scope of the appended claims. In addition, the description of well-known devices and methods may be omitted so as not to obscure the description of the exemplary embodiments. As will be understood by those skilled in the art, such methods and devices clearly fall within the scope of the present teachings. It should also be understood that the term "example" as used herein is intended to be non-exclusive and non-restrictive in nature.

[0033] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.In addition to the technical, scientific or ordinary meanings of the defined terms, the defined terms are commonly understood and accepted in the relevant context.

[0034] Unless the context clearly dictates otherwise, the terms "a," "an," and "the" include both singular and plural referents. Thus, for example, "a device" includes one device and a plurality of devices. As shown in the figures, relative terms may be used to describe the relationship of various elements to one another. These relative terms are intended to encompass different orientations of the device and / or elements in addition to the orientation depicted in the figures.

[0035] When the term "constant voltage" is used herein, the term "constant voltage" means that the voltage is substantially constant in that the voltage does not vary by more than about 10% of its average value over time. Similarly, when the term "constant current" is used herein, the term "constant current" means that the current is substantially constant in that the current does not vary by more than about 10% of its average value over time. Representative embodiments described herein are directed to a receiver device that delivers a constant voltage or a constant current to an electrical load electrically coupled to the receiver device, depending on whether a constant voltage or a constant current is needed or desired.

[0036] Where a first device is referred to as being connected or coupled to a second device, this encompasses examples where one or more intermediate devices may be employed to connect the two devices to each other. Conversely, where a first device is referred to as being directly connected or coupled to a second device, this encompasses examples where the two devices are connected together without any intermediate devices other than electrical connectors (e.g., wires, bonding materials, etc.). When the phrase "electrically coupled to" is used herein, the phrase "electrically coupled to" may represent a wireless electromagnetic coupling between two devices or a wired connection between the two devices, with or without an intermediate device for interconnecting the two devices.

[0037] Figure 1 1 is a block diagram of a wireless power receiver circuit 1 that can be used to wirelessly receive power in a wireless power transfer system, such as, for example, the wireless power transfer system 100 disclosed in the above-mentioned U.S. application Ser. No. 15 / 296,704 (hereinafter referred to as the "704" application) from a wireless power transmitter. Figure 1 In FIG. 1 , the wireless power receiver circuit 1 is a pulse width modulation (PWM) wireless power receiver circuit represented by a combination of four functional blocks 3 - 6 , each of which performs one or more functions and has at least one input and at least one output.

[0038] Frame 3 is an LC resonator circuit, which includes at least a capacitor 7 and an inductor 8 connected in parallel, and an electrically controllable switch 9. The electrically controllable switch 9 is activated by the output signal of frame 6, as will be described in more detail below. According to this representative embodiment, when the electrically controllable switch 9 is in an off state, the LC resonator circuit receives RF power from the ambient magnetic field and outputs RF power. The RF power output from frame 3 is fed into the input terminal of frame 4, which is an RF rectifier circuit that rectifies the RF power, thereby converting the RF power into DC power. Figure 1 In FIG. 4 , the RF rectifier circuit is represented by a diode 11. The DC power output from block 4 is fed into the input terminals of block 5, which includes an energy storage device 12 connected in parallel with the DC load 2. For illustration purposes, the energy storage device 12 is Figure 1 is represented by a single capacitor.

[0039] Block 5 outputs an output signal at its output terminal to block 6. The output signal is proportional to a parameter (voltage or current) that is intended to be regulated so as to remain substantially constant. As will be described in more detail below, in some cases, the wireless power receiver circuit 1 is configured to deliver a substantially constant DC current to the DC load 2, and in other cases, the wireless power receiver circuit 1 is configured to deliver a substantially constant DC voltage to the DC load 2.

[0040] The output signal from the block 5 is fed as an input signal into an input terminal of a block 6, which includes a comparator 14 having a preselected amount of hysteresis and a reference terminal 15. The comparator 14 compares the input signal with a reference signal received at the reference terminal 15 and outputs a control signal whose value is based on whether the input signal is greater than the reference signal or less than or equal to the reference signal. The control signal output from the block 6 is fed into the control signal input terminal 16 of the block 3. As described above, the state of the electrically controllable switch 9 is controlled (i.e., activated or deactivated) based on the value of the control signal output from the block 6 and input to the block 3. The electrically controllable switch 9 can be any voltage-controlled switch, such as, for example, a metal oxide semiconductor field effect transistor (MOSFET), a relay, a complementary metal oxide semiconductor (CMOS), an RF switch, etc.

[0041] The closed feedback loop comprising four blocks 3-6 is used to adjust the load parameter measured by the signal output from block 5 to ensure that a substantially constant current or voltage is delivered to the DC load 2 even if the load impedance or the ambient magnetic field strength varies.

[0042] Depending on the state of the electrically controllable switch 9, the circuit 1 has two states: an idle state (the switch 9 is in a first state, e.g., the switch 9 is closed); and an active state (the switch 9 is in a second state, e.g., the switch 9 is open). According to this representative embodiment, the first state of the switch 9 is a closed state, and the second state of the switch 9 is an open state, and the idle state and the active state of the receiver circuit 1 correspond to the closed state and the open state of the switch 9, respectively. It should be noted that the opposite may be true in other embodiments. For the purpose of demonstrating the inventive principles and concepts, the following discussion assumes that when the switch 9 is in the open state, the circuit 1 is in the active state, and when the switch 9 is in the closed state, the circuit 1 is in the idle state.

[0043] When the circuit 1 is in an active state, the switch 9 is turned off (off state), and the LC resonator circuit 3 receives power due to the induced voltage Vind, so that the RF voltage appears across the capacitor 7. As the LC resonator circuit 3 accumulates energy, there will be an initial ring-up period. Once the RF voltage across the capacitor 7 reaches a sufficiently high amplitude to begin to forward bias the rectifier circuit 4, the circuit 1 enters a charging period. The rectifier circuit 4 rectifies the RF voltage across the capacitor 7 and charges the capacitor 12 of the frame 5, so that its DC voltage slowly rises. When the voltage on the non-inverting input terminal of the comparator 14 exceeds the reference voltage VREF, the output of the comparator 14 switches to its maximum output value (e.g., a logic high level), which causes the electrically controllable switch 9 to turn on (closed state). At this point, the circuit 1 enters an idle state.

[0044] When switch 9 is turned on, it shorts capacitor 7 to ground, and the RF voltage across capacitor 7 decreases to a very low level. Rectifier diode 11 is then reverse biased and prevents capacitor 12 from discharging through inductor 8. Capacitor 12 slowly discharges through load 21, thereby reducing the voltage across capacitor 12. Comparator 14 is designed to have a preselected amount of hysteresis so that when the voltage on the non-inverting input terminal of comparator 14 begins to decrease, it does not change state immediately. Once the voltage on the non-inverting input terminal of capacitor C3 29 decreases by a certain amount ΔV set by hysteresis, comparator 14 changes state and outputs its minimum output value (e.g., a logic low level). At this point, electrically controllable switch 9 is turned off. Circuit 1 reenters the active state, and the cycle repeats.

[0045] As can be seen from the above description, the LC resonator circuit is turned off during the idle period and does not receive power or dissipate heat. This allows the receiver circuit 1 to operate within a wide dynamic range of ambient magnetic field strengths. In a weak magnetic field, the receiver circuit 1 will be active for most of the PWM cycle. In a strong magnetic field, the receiver circuit 1 will be in an idle state for most of the PWM cycle. In the idle state, the LC resonator circuit is detuned or does not resonate. Therefore, its resonant response to the ambient magnetic field is very weak and / or negligible, and it will not receive power or dissipate heat. In other words, the resonant response of the receiver circuit 1 is turned off during the idle period to prevent the receiver circuit 1 from receiving power and dissipating heat. Not dissipating heat during the idle period improves both the safety and efficiency of the receiver circuit 1.

[0046] Each of blocks 3-6 of the wireless power receiver circuit 1 may have a variety of configurations. Figures 2 to 21 Description Execute the above reference Figure 1 The functions described above and have the Figure 1 Several examples of wireless power receiver circuits with the described features. It should be noted that the inventive principles and concepts are not limited to Figures 2 to 21 Examples shown, and may create structures not specifically shown and described herein with reference to the above Figure 1 The features and implementations described above refer to Figure 1 It should also be noted that the wireless power receiver apparatus disclosed herein is not limited to use with any particular wireless power transmitter, but may be used with any suitable wireless power transmitter and in any suitable wireless power transfer system.

[0047] Figure 2 is a schematic diagram of a wireless power receiver circuit 20 according to a representative embodiment that can be used to wirelessly receive power in a wireless power transfer system (such as, for example, the wireless power transfer system 100 disclosed in the '704 application). According to the representative embodiment, the wireless power receiver circuit 20 is a PWM wireless power receiver circuit that provides a constant voltage to an electrical load 21. The ambient magnetic field drives an inductor L1 22, and a voltage (at Figure 2 Assuming that B represents the component of the ambient magnetic field parallel to the dipole moment of the inductor L1 22, the capacitor C1 24 and the inductor L1 22 form a resonant LC tank circuit in combination, which is tuned to resonate at the oscillation frequency of the ambient magnetic field B.

[0048] The circuit 20 has two states: active (switch S1 26 is open) and idle (switch S1 26 is on), depending on the state of the electrically controllable switch S1 26. The switch S1 26 may be any voltage controlled switch, such as, for example, one or more MOSFET transistors, a relay, one or more CMOS transistors, an RF switch, etc. When the circuit 20 is in the active state, the switch S1 26 is off, and the tank circuit including L1 22 and C1 24 receives power due to the induced voltage Vind, causing an RF voltage to appear across the capacitor C1 24. As the LC tank circuit accumulates energy, there will be an initial ring-up period.

[0049] Figure 3 is a graph of the voltage across capacitor C1 24 as a function of time. Once the RF voltage across capacitor C1 24 reaches a high enough amplitude to begin forward biasing rectifier diode D1 27, circuit 20 enters a charging period. Rectifier diode D1 27 rectifies the RF voltage across C1 24 and charges capacitor C3 29, causing its DC voltage to slowly rise. Two resistors R1 31 and R2 32 form a resistor divider that provides a portion of the voltage across capacitor C3 29 to the non-inverting input terminal of comparator IC1 33. When the voltage at the non-inverting input terminal of comparator IC1 33 exceeds the reference voltage VREF, the output of comparator IC1 33 will switch to a logic high level. Then the electrically controllable switch S1 26 will be turned on. At this point, circuit 20 enters an idle state.

[0050] When switch S1 26 is turned on, it shorts capacitor C1 24 to ground. Switch S1 26 preferably has a low resistance to ensure that the Q of the LC tank circuit is very low and the RF voltage across capacitor C1 24 is reduced to a very low level. Rectifier diode D1 27 is then reverse biased and prevents capacitor C3 29 from discharging through inductor L1 22. Capacitor C3 29 is slowly discharged through load 21, causing its voltage to decrease.

[0051] According to this representative embodiment, comparator IC1 33 is designed to have a preselected amount of hysteresis so that when the voltage on the non-inverting input terminal of comparator IC1 33 begins to decrease, it does not change state immediately. Once the voltage on the non-inverting input terminal of capacitor C3 29 decreases by a certain amount ΔV set by the hysteresis, comparator IC1 33 changes state and outputs a logic low level. At this time, the electrically controllable switch S1 26 turns off. Circuit 20 re-enters the active state, and the cycle repeats.

[0052] As can be seen from the above description, the LC tank circuit is turned off during the idle period and does not receive power or dissipate heat. This allows the receiver circuit 20 to operate within a wide dynamic range of ambient magnetic field strengths. In a weak magnetic field, the receiver circuit 20 will be active for most of the PWM cycle. In a strong magnetic field, the receiver circuit 20 will be in an idle state for most of the PWM cycle. In the idle state, the resonator (i.e., the LC tank) is detuned or non-resonant. Therefore, its resonant response to the ambient magnetic field is very weak and / or negligible, and it will not receive power or dissipate heat. In other words, the resonant response of the receiver circuit 20 is turned off during the idle period to prevent the receiver circuit 20 from receiving power and dissipating heat. Not dissipating heat during the idle period improves both the safety and efficiency of the receiver circuit 20.

[0053] Figure 4 is a graph of the voltage across load 21 as a function of time. The voltage across load 21 is regulated and is essentially constant over time, with a small triangular wave ripple. The voltage varies only slightly over time between approximately 19.9v and 21.7v. In this example, the average voltage is 20.8v. The amount of change in the voltage across load 21 is less than 10% of the average load voltage, and typically less than 5% of the average load voltage. The magnitude of the ripple is set by the hysteresis of comparator IC1 33, and can be made smaller by selecting a comparator with less hysteresis.

[0054] As described above, according to this representative embodiment, the comparator IC1 33 is designed to have a preselected amount of hysteresis so that when the voltage on the non-inverting input terminal of the comparator IC1 33 begins to decrease, it does not change state immediately. Instead, the comparator IC1 33 does not change state and outputs a logic low level until the voltage on the non-inverting input terminal of the capacitor C3 29 has decreased by a certain amount ΔV set by the hysteresis. This feature allows the receiver circuit 20 to switch between the active state and the idle state at a frequency significantly lower than the oscillation frequency of the ambient magnetic field. For example, the switching frequency of the receiver circuit according to the inventive principles and concepts can be one-tenth or even one-hundredth of a hundredth of a hundredth of a switching frequency of the ambient magnetic field. Therefore, the components of the receiver circuit 20 involved in the switching process can be relatively low-speed, relatively inexpensive components.

[0055] In contrast, known PWM receiver circuits do not incorporate a preselected amount of hysteresis in the comparators sufficient to allow them to operate at a frequency much lower than the frequency of oscillation of the ambient magnetic field. Therefore, they switch at a frequency comparable to the frequency of oscillation of the ambient magnetic field. Because this frequency can be relatively high, the circuit elements involved in the switching process are also relatively high-speed components, which are generally more complex and expensive than low-speed components.

[0056] Figure 5 FIG. 4 is a schematic diagram of a wireless power PWM receiver circuit 40 according to a representative embodiment, which can be used to wirelessly receive power in a wireless power transmission system. Figure 5 The receiver circuit 40 shown includes, in addition to an additional capacitor C0 41 connected in series with the inductor L1 22 and an additional rectifier diode D2 42 connected in parallel with the capacitor C1 24, Figure 4 The wireless power PWM receiver circuit 40 shown is Figure 2 The operation of the receiver circuit 40 is the same as that of the wireless power PWM receiver circuit 20 shown in FIG. 1 , except that the ratio of C1 24 to C0 40 is preselected to more effectively match the impedance of the LC tank circuit including C1 24, L1 22 and C0 41 to the impedance of the load 24. Figure 2 The operation of the receiver circuit 20 shown is substantially the same.

[0057] Figure 6 is a graph of the voltage across capacitor C1 24 as a function of time. The purpose of rectifier diode D2 42 is to provide a DC path for the load current, since capacitor C0 41 blocks this DC current from flowing through inductor L1 22. Rectifier diode D2 42 causes a DC charge to accumulate on capacitor C1 24 during the active state, which can be seen from Figure 6 This can be seen from the waveform drawn in .

[0058] Figure 7 FIG. 1 is a schematic diagram of a wireless power PWM receiver circuit 50 according to another representative embodiment, which can be used to wirelessly receive power in a wireless power transmission system. The PWM receiver circuit 50 is similar to the wireless power receiver circuit 50 except that the position of the switch S1 26 has been changed. Figure 5 The operation of the receiver circuit 50 is the same as that of the PWM receiver circuit 40 shown. Figure 2 The operation of the receiver circuit 20 shown is substantially the same.

[0059] If the capacitance ratio C1 24 / C0 41 is too large, then when the PWM circuit 40 is in an idle state, Figure 5 The receiver circuit 40 shown will not be able to adequately detune the resonant LC tank circuit. If the LC tank circuit is not adequately detuned, the induced voltage Vind will generate a large circulating RF current which will dissipate heat. This will not only waste power, but may also cause heat dissipation problems in the receiver circuit 40. By shorting the inductor L1 22 directly to ground instead of just shorting the capacitor C1 24 to ground, Figure 7 The illustrated receiver circuit 50 solves this problem. This ensures that the LC tank circuit is detuned from resonance in the idle state, regardless of the ratio of C1 to C0.

[0060] References Figure 2 , 5 The three PWM receiver circuits 20, 40 and 50 described in Figures 1 and 7 are all designed to provide a constant DC voltage to the load 21. However, in some cases, the load requires a constant DC current, rather than a constant DC voltage. Figure 8 , 9 10 respectively show wireless power PWM receiver circuits 60 , 70 , and 80 according to representative embodiments, which provide a constant DC current to the load 21 .

[0061] exist Figure 8 , 9 In the PWM receiver circuits 60, 70 and 80 shown in FIGS. 10 and 11 respectively, the load 21 is placed in series with the resistor R1 31. The comparator IC1 33 provides feedback which keeps the voltage across the resistor R1 31 very close to the reference voltage Vref. Because the current through the resistor R1 31 is equal to the current through the load 21, these circuits will force the current through the load 21 to remain constant.

[0062] Figure 2 , 5 The electrically controllable switch S1 26 shown in FIG. 7-10 may be implemented by, for example, an n-channel MOSFET transistor Q1 92, as shown in FIG. Fig.11 , 12 and 13. Fig.11 , 12 13 are schematic diagrams of wireless power PWM receiver circuits 90, 100, and 110, respectively, according to representative embodiments, which can be used to wirelessly receive power in a wireless power transmission system. The PWM receiver circuits 90, 100, and 110 are similar to the wireless power receiver circuits 100, 100, and 110, except that the switch S126 has been replaced by an n-channel MOSFET transistor Q1 92. Figure 2 , 5 7-10. The operation of receiver circuits 90, 100, and 110 is very similar to the PWM receiver circuits shown in FIG. Figure 2 The operation of the receiver circuit 20 shown is substantially the same to deliver a constant DC voltage to the load 21 .

[0063] In the receiver circuits 90, 100 and 110, the n-channel MOSFET transistor Q1 92 plays the role of the above reference Figure 1The function of the electrically controllable switch 9 described above. However, unlike an ideal switch, the MOSFET transistor Q1 92 can still conduct current when in its off state due to the internal body diode of the MOSFET, which points from the source to the drain. Therefore, in order for the MOSFET Q1 92 to operate as a switch, the voltage at the drain cannot be allowed to become lower than a voltage that is one diode drop below the source voltage. In order to achieve this condition, Fig.11 and Fig.13 In the receiver circuits 90 and 110 shown respectively, an additional capacitor C2 91 has been placed in series with the MOSFET Q1 92. When the circuit is active, capacitor C2 91 accumulates a DC charge which keeps the drain of the MOSFET Q1 92 positive with respect to the source. The value of capacitor C2 91 should be chosen to be large enough so that it appears as an RF short circuit at the resonant frequency of the LC tank circuit.

[0064] exist Fig.12 Capacitor C2 91 is not used in the illustrated receiver circuit 100. In the receiver circuit 100, capacitor C1 24 accumulates DC charge and performs the role that capacitor C2 91 performs in the other two receiver circuits 90 and 110.

[0065] Fig.14 1 is a schematic diagram of a wireless power PWM receiver circuit 120 according to a representative embodiment, which can be used to wirelessly receive power in a wireless power transmission system. In addition to the receiver circuit 120 including a battery or electrochemical battery (in Fig.14 In addition to the PWM receiver circuit 120 and the Figure 2 The receiver circuit 120 operates the same as the PWM receiver circuit 20 shown, except that the receiver circuit 120 charges the battery or electrochemical cell B1 121. Figure 2 The operation of the receiver circuit 20 shown is substantially the same.

[0066] The battery or electrochemical cell B1 121 is connected in parallel with the capacitor C3 29 and effectively behaves like a very large capacitor. Therefore, the receiver circuit 120 can be made to have a very low PWM frequency. When the voltage of the battery or electrochemical cell B1 121 is low, the receiver circuit 120 is active and continuously charges the battery or electrochemical cell B1 121 with a constant DC current. The magnitude of the constant DC current depends on the magnitude of Vind, which is proportional to the strength of the ambient magnetic field. In a stronger field, the charging current will be higher and the battery or electrochemical cell B1 121 will charge faster.

[0067] Once the voltage of the battery or electrochemical cell B1 121 becomes high enough to trigger the comparator IC1 33, the electrically controllable switch S1 26 is turned on and the circuit 120 enters the idle state. When the receiver circuit 120 is in the idle state, the battery or electrochemical cell B1 121 is continuously discharged through the load 21, causing its voltage to decrease. Once the voltage on the battery or electrochemical cell B1 121 decreases by a certain amount determined by the hysteresis of the comparator IC1 33, the electrically controllable switch S1 26 is deactivated and the circuit 120 re-enters the active state.

[0068] It should be noted that if a battery or electrochemical cell B1 121 is placed in parallel with capacitor C3 29 in these circuits, and if the power level is selected so that the DC charging current does not exceed the maximum allowable charging current of the battery or electrochemical cell B1 121, then Figure 2 , 5 The constant voltage PWM circuit topologies shown in Figure 7 will all work equally well as battery charging circuits.

[0069] Fig.15 1 is a schematic diagram of a wireless power PWM receiver circuit 130 that can be used to wirelessly receive power in a wireless power transmission system according to another representative embodiment. According to this representative embodiment, the receiver circuit 130 uses a current limiting resistor R3 131 to charge a battery or electrochemical cell B1 121. If Fig.14 If the DC charging current of the receiver circuit 120 shown exceeds the maximum allowable charging current of the battery or electrochemical cell B1 121, then one option is to modify the circuit 120 by adding a current limiting resistor R3 131 in series with the battery or electrochemical cell B1 121, as shown in FIG. Fig.15 shown.

[0070] Fig.15 Another benefit of the receiver circuit 130 shown is that the combination of the battery or electrochemical cell B1 121 and the current limiting resistor R3 131 acts as a low pass filter that substantially smoothes the voltage at the load 21 and eliminates Figure 4 The triangle ripple on the load voltage is shown.

[0071] It should be noted that Fig.14 The receiver circuit 120 shown is different. Fig.15 The PWM frequency of the receiver circuit 130 shown is determined by the value of capacitor C3 29, and Fig.14 In the receiver circuit 120 shown, the PWM frequency is determined by the capacity of the battery or electrochemical cell B1 121. This means that Fig.15 The PWM frequency of the receiver circuit 130 shown may be greater than Fig.14The PWM frequency of the receiver circuit 120 shown is much higher.

[0072] Reference again Figure 4 As described above, the periodic switching of the receiver circuit 20 causes a small triangular wave ripple on the voltage across capacitor C3 29. The amplitude of this ripple is set entirely by the hysteresis of the comparator 33, and the amplitude of this ripple can be made smaller or larger by selecting a comparator with less or greater hysteresis, respectively. However, the hysteresis cannot be eliminated because it partially determines the frequency of the PWM. If the load 21 is connected in parallel with the capacitor C3 29, the load 21 will also have the same triangular wave ripple on its voltage.

[0073] In some applications, this ripple may be undesirable. Fig.15 The receiver circuit 130 shown has the following characteristics: the combination of resistor R3 131 and battery or electrochemical cell B1 121 acts as a low pass filter to smooth the voltage across the load 21. The same effect can be achieved using a low pass RC or LC filter without a battery, as will now be described with reference to Fig.16 and 17 described.

[0074] Fig.16 1 is a schematic diagram of a wireless power PWM receiver circuit 140 according to a representative embodiment, which can be used to wirelessly receive power in a wireless power transmission system. According to the representative embodiment, the receiver circuit 140 includes a low-pass RC circuit, which includes a resistor R3 131 and a capacitor C4 141. The low-pass RC circuit including the resistor R3 131 and the capacitor C4 141 reduces the ripple in the load voltage.

[0075] Fig.17 1 is a schematic diagram of a wireless power PWM receiver circuit 150 according to a representative embodiment, which can be used to wirelessly receive power in a wireless power transmission system. According to the representative embodiment, the receiver circuit 150 includes a low-pass LC circuit, which includes an inductor L2 151 and a capacitor C4 141. The low-pass LC circuit including the resistor inductor L2 151 and the capacitor C4 141 reduces the ripple in the load voltage.

[0076] It is also possible to use a linear regulator to provide a constant voltage to the load, as now referenced Fig.18 described. Fig.181 is a schematic diagram of a wireless power PWM receiver circuit 160 according to a representative embodiment, which can be used to wirelessly receive power in a wireless power transmission system. According to the representative embodiment, the receiver circuit 160 includes a linear regulator IC2 161, which reduces ripple in the load voltage.

[0077] In some applications, it may be desirable to turn off the LC tank of the receiver circuit resonance at certain times or based on certain conditions. Fig.19 Describes an example of how the LC tank of a receiver circuit may be shut down.

[0078] Fig.19 1 is a schematic diagram of a wireless power PWM receiver circuit 170 according to a representative embodiment, which can be used to wirelessly receive power in a wireless power transmission system. According to the representative embodiment, the receiver circuit 170 is configured to shut down the LC energy tank including the inductor L1 22 and the capacitor C1 24 at certain times or based on certain conditions to prevent the receiver circuit from resonating. The receiver circuit 170 has an OR gate IC2 171, which activates the switch S1 26 whenever a logic high signal is received from the comparator IC133 or from the control circuit IC3 173, and the control circuit IC3 173 can be, for example, a microcontroller integrated circuit (IC) chip, an RF communication chip, an optical communication chip, a thermometer chip with a binary output based on a temperature threshold, etc.

[0079] In some cases, it is necessary or desirable to protect the PWM receiver circuit or load from excessive heat. For example, if the circuit is exposed to abnormally high magnetic field strengths, or if comparator IC1 33 fails, the LC energy tank of the PWM receiver circuit may absorb power and generate excessive heat. Fig. 20 1 is a schematic diagram of a wireless power PWM receiver circuit 180 for use in a wireless power transmission system according to another representative embodiment, which provides such thermal protection. A thermal fuse F1 181 is placed in series with a resonant LC tank circuit including a capacitor C1 24 and an inductor L1 22. When fuse F1 181 is exposed to a temperature exceeding a certain predetermined threshold (TH), it becomes an open circuit (placed in an open state), thereby preventing the LC tank circuit from receiving any power. When fuse F1 181 is in the open state, the resonant response of the resonant circuit is turned off, so that the receiver circuit 180 receives only a minimum amount of electrical power (if any). Otherwise, fuse F1 181 is in a PWM state.

[0080] In some cases, thermal fuse F1 181 may be replaced by a thermal switch that returns to normal operation once the temperature has dropped below a predetermined TH value. Thus, element 181 represents a thermal fuse or a thermal switch. It should be noted that in the above reference to Figure 2 , 5 In any of the PWM topologies described in 7-19, a thermal fuse or switch F1 181 may be placed in series with the LC tank circuit.

[0081] Fig.21 1 is a schematic diagram of a wireless power receiver circuit 190 for use in a wireless power transmission system according to another representative embodiment, and the wireless power receiver circuit 190 includes a user-controllable switch S2 191 that can be turned on and off by the user to allow the user to activate and deactivate the receiver circuit 190. In all other aspects, the receiver circuit 190 is similar to Figure 2 When switch S2 191 is open (placed in the off state), the resonant response of the receiver circuit 190 is turned off, so that the receiver circuit 190 cannot receive any power regardless of the strength of the ambient magnetic field. Fig.21 In the disconnected position shown, the receiver circuit 190 is safe or protected from any kind of over-voltage or over-temperature fault.

[0082] It should be emphasized that the above-mentioned embodiments of the present disclosure are merely possible examples of implementations set forth for a clear understanding of the principles of the present disclosure. Many changes and modifications may be made to the above-mentioned embodiments without substantially departing from the spirit and principles of the present disclosure. Here, all these modifications and changes are intended to be included within the scope of the present disclosure and protected by the appended claims.

Claims

1. A wireless power receiver circuit for use in a wireless power transmission system, the wireless power receiver circuit comprising: a resonator circuit configured to resonate at a frequency of an ambient magnetic field generated by a wireless power transmitter of the wireless power transfer system and output a radio frequency (RF) output signal when the wireless power receiver circuit is in an active state, the resonator circuit comprising an electrically controllable switch controllable by a control signal to switch the resonator circuit from a first state to a second state and from the second state to the first state; an alternating current (AC) to direct current (DC) rectifier circuit, into which a radio frequency (RF) output signal output from the resonator circuit is input, and the alternating current (AC) to direct current (DC) rectifier circuit converts the radio frequency (RF) output signal into a direct current (DC) power signal and outputs the direct current (DC) power signal; a direct current (DC) load circuit having a DC load and an energy storage device, wherein during an active state, a DC power signal output by the alternating current (AC) to direct current (DC) rectifier circuit charges the energy storage device, thereby delivering a substantially constant direct current (DC) current or a substantially constant direct current (DC) voltage to the DC load, depending on whether the DC load uses a substantially constant direct current (DC) current or a substantially constant direct current (DC) voltage; a comparator circuit that receives an output signal output from the direct current (DC) load circuit, compares the received output signal with a preselected reference voltage signal, and generates the control signal, which is fed back to the resonator circuit to control the state of the electrically controllable switch; and Fuses or switches are connected in a row in the resonator circuit, wherein a resonant response of the resonator circuit is turned off when the wireless power receiver circuit is in an off state, and wherein the wireless power receiver circuit receives a minimum amount of electrical power when the wireless power receiver circuit is in the off state.

2. The wireless power receiver circuit according to claim 1, wherein: The first state and the second state of the resonator circuit correspond to a closed state and an open state of the resonator circuit, respectively, wherein switching the resonator circuit from the closed state to the open state causes the wireless power receiver circuit to switch from an idle state to an active state, and switching the resonator circuit from the open state to the closed state causes the wireless power receiver circuit to switch from an active state to an idle state, and wherein, when the wireless power receiver circuit is in the idle state, the resonant response of the resonator circuit is turned off, and wherein, when the wireless power receiver circuit is in the idle state, the wireless power receiver circuit receives a minimum amount of electrical power.

3. The wireless power receiver circuit according to claim 2, wherein: When the output signal output from the direct current (DC) load circuit has dropped to a value that is a predetermined amount lower than the preselected reference voltage signal, the control signal generated by the comparator circuit has a low value, which causes the electrically controllable switch to switch from a closed state to an open state, thereby placing the wireless power receiver circuit in an active state.

4. The wireless power receiver circuit according to claim 3, wherein: The comparator circuit exhibits a preselected amount of hysteresis that determines the predetermined amount that an output signal output from the direct current (DC) load circuit drops below the preselected reference voltage signal before the comparator circuit outputs the control signal.

5. The wireless power receiver circuit of claim 4, wherein: The preselected amount of hysteresis is preselected to delay switching of the wireless power receiver circuit from an idle state to an active state, and wherein the delay ensures that switching of the wireless power receiver circuit is performed at a frequency lower than a frequency of the ambient magnetic field.

6. The wireless power receiver circuit of claim 1 , wherein: When the energy storage device is fully charged, the wireless power receiver circuit switches from an active state to an idle state, and wherein, when the wireless power receiver circuit is in the idle state, the resonator circuit is turned off and has no resonant response to ambient magnetic fields, and wherein, when the charge on the energy storage device decreases to below a predetermined level, the wireless power receiver circuit switches from the idle state to an active state, and wherein, when the wireless power receiver circuit is in the active state, the resonator circuit has a resonant response to ambient magnetic fields.

7. The wireless power receiver circuit of claim 6, wherein: The resonator circuit includes at least a first capacitor and a first inductor connected in series with each other.

8. The wireless power receiver circuit of claim 7, wherein: The electrically controllable switch is connected in parallel with the first capacitor.

9. The wireless power receiver circuit of claim 6, wherein: The resonator circuit includes at least a first capacitor and a first inductor connected in series with each other and a second capacitor connected in parallel with the electrically controllable switch.

10. The wireless power receiver circuit of claim 1, wherein: The alternating current (AC) to direct current (DC) rectifier circuit includes a first rectifier diode, wherein the resonator circuit includes at least a first capacitor and a first inductor connected in series with each other and a second capacitor connected in parallel with the electrically controllable switch, and the wireless power receiver circuit further includes: A second rectifier diode is connected in parallel with the second capacitor and the electrically controllable switch.

11. The wireless power receiver circuit of claim 1 , wherein: The direct current (DC) load circuit also includes: A resistor network including at least one resistor is connected to an output node of the direct current (DC) load circuit and to at least one of the direct current (DC) load and the energy storage device.

12. The wireless power receiver circuit of claim 11, wherein: The direct current (DC) load circuit also includes: A battery or electrochemical cell is connected in parallel with the direct current (DC) load.

13. The wireless power receiver circuit of claim 12, wherein: The direct current (DC) load circuit further includes: A capacitor is connected in parallel with the direct current (DC) load.

14. The wireless power receiver circuit of claim 13, wherein: The direct current (DC) load circuit also includes: A resistor connected in series with the battery or electrochemical cell.

15. The wireless power receiver circuit of claim 11, wherein: The direct current (DC) load circuit also includes: A low pass resistor-capacitor (RC) filter is connected in series with the direct current (DC) load.

16. The wireless power receiver circuit of claim 11, wherein: The direct current (DC) load circuit further includes: A low pass inductor-capacitor filter is connected in series with the direct current (DC) load.

17. The wireless power receiver circuit of claim 11, wherein: The direct current (DC) load circuit further includes: A linear regulator has an input terminal connected to the resistor network and has an output terminal connected to the direct current (DC) load.

18. The wireless power receiver circuit of claim 17, wherein: The direct current (DC) load circuit at least includes: A first capacitor is connected in parallel with the direct current (DC) load.

19. The wireless power receiver circuit of claim 11, further comprising: A control circuit is electrically coupled to the electrically controllable switch, the control circuit being configured to detect whether a predetermined event or condition has occurred, and upon detecting that the predetermined event or condition has occurred, to place the electrically controllable switch such that the resonator circuit is in a first state.

20. The wireless power receiver circuit of claim 1, in, The fuse or switch is configured to create an open circuit in the resonator circuit if the temperature exceeds a predetermined temperature to switch the wireless power receiver circuit from a pulse width modulation (PWM) state to an off state.

21. The wireless power receiver circuit of claim 1, in, The switches of the fuse are user-controllable switches connected in a row in the resonator circuit, wherein the user-controllable switches can be turned on and off by a user to allow the user to switch the wireless power receiver circuit from a pulse width modulation (PWM) state to an off state and from an off state to a pulse width modulation (PWM) state.

22. A method for receiving wireless power in a wireless power transmission system, the wireless power transmission system comprising: Utilizing a resonator circuit of a wireless power receiver circuit, operating in an active state or an idle state, wherein in the active state, the resonator circuit resonates at a frequency of an ambient magnetic field generated by a wireless power transmitter of the wireless power transmission system and outputs a radio frequency (RF) output signal, the resonator circuit comprising an electrically controllable switch, the electrically controllable switch being controllable by a control signal to switch the resonator circuit from a first state to a second state and from the second state to the first state, during the first state, the resonator circuit is in an idle state, and during the second state, the resonator circuit operates in the active state; Converting the RF output signal into a DC power signal using an AC to DC rectifier circuit and outputting the DC power signal; Utilizing a DC load circuit having a DC load and an energy storage device, the energy storage device is charged when the resonator circuit is in an active state, thereby delivering a substantially constant DC current or a substantially constant DC voltage to the DC load depending on whether the DC load uses a substantially constant DC current or a substantially constant DC voltage; and A comparator circuit is used to receive an output signal output from the direct current (DC) load circuit, compare the received output signal with a preselected reference voltage signal, generate a control signal, and feed the control signal back to the resonator circuit to control the state of the electrically controllable switch, wherein the comparator circuit exhibits a preselected amount of hysteresis, which determines the predetermined amount by which the output signal output from the direct current (DC) load circuit drops below the preselected reference voltage signal before the comparator circuit outputs the control signal.

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