Wireless battery charging system and method for battery charging and handshaking

Abstract

Coordinated control and use of a transmitter circuit and a receiver circuit for wireless battery charging are provided, with an emphasis on using a power switch in the receiver circuit not only for handshaking with the transmitter circuit for compatibility checking and communication of information, but also for battery charging mode control. It utilizes an additional switching operation of the power switch in the receiver circuit (such as the switching operation commonly used in the Qi standard for handshaking with the transmitter circuit) to charge the battery directly from the output of the rectifier in a constant current mode or a constant voltage mode according to a threshold battery voltage, without using an additional battery management circuit between the rectifier and the battery of the receiver circuit. The coordinated operation of the transmitter and receiver circuits can be achieved without using any additional wireless communication system for signal synchronization between the two circuits.

Description

[0001] List of abbreviations

[0002] AC alternating current

[0003] ASK Amplitude Shift Keying

[0004] BMC battery management circuit

[0005] CC Constant Current

[0006] CV Constant Voltage

[0007] DC Direct current

[0008] FSK Frequency Shift Keying

[0009] LC Inductor-Capacitor

[0010] LUT Lookup Table

[0011] PI Proportional-Integral

[0012] RMS root mean square

[0013] Rx Receiver

[0014] SoC charging status

[0015] SoH State of Health

[0016] Tx Transmitter Technical Field

[0017] The present invention generally relates to wireless battery charging. In particular, the present invention relates to a wireless battery charging system and method for battery charging and handshaking between Tx and Rx. Background Art

[0018] Wireless charging systems usually require some form of wireless communication between the loads on the Tx and Rx sides. For example, in the Qi standard promoted by the Wireless Power Consortium, switch-mode modulation techniques are used in the Rx circuit to send information packets from the Rx side to the Tx side. Packets are data structures used for communication between the Tx and Rx circuits. Figure 1 In the example, switches S5 and S6 in the Rx circuit can be used to ground capacitors Cd1 and Cd2 in a switching manner. The switching action of S5 and S6 will change the impedance in the Rx circuit so that the reflected impedance affects the electrical variables (such as current) in the Tx circuit. Similarly, Figure 2 An alternative Rx circuit is shown with a switch S5 that can switch resistor Rd to ground in a switching manner. Typically, FSK or ASK can be used so that the digital signal ( Figure 3). The Qi standard specifies a list of packets for FSK-based codecs used for handshake purposes. These packets can be found in the Qi standard document and are not included here.

[0019] Generally speaking, Qi-compliant wireless chargers provide a voltage source at the rectifier output of the Rx circuit. Figure 1 and Figure 2 As shown in , in order to control the CC mode and CV mode of the battery according to the battery charging curve ( Figure 4 ), usually requires an additional BMC between this rectifier output and the battery load.

[0020] The conventional 2-coil series LC resonant circuit for wireless charging system can provide the following Figure 4 The "voltage-source" output of the CV mode indicated in the reference (C. S. Wang, OH. Stielau, G. Covic, "Design considerations for a contactless electric vehicle battery charger", IEEE Transactions on Industrial Electronics, Vol. 52, No. 5, October 2004, pp. 1308-1314, the disclosure of which is incorporated herein by reference) points out that "the series compensation secondary resembles a voltage source, while the parallel compensation secondary looks like a current source." For this reason, it is necessary to Figure 5 The battery charging circuit (also called a battery management system) shown in converts the voltage source of the rectifier output from Rx into either a current source for CC mode and a voltage source for CV mode. An example of an industrial battery charging circuit is the Texas Instruments bq5105 integrated circuit, such as Figure 6 as shown in .

[0021] While there are many existing wireless charging systems, there remains a need in the art for wireless battery charging technology that is improved in any practical way, such as eliminating the DC regulator on the Rx side of the system. In practical situations where there are more receivers for receiving battery charging than transmitters for providing power, eliminating the DC regulator may bring the advantage of reducing costs. For example, such a practical situation may be charging electric vehicles using roadside battery charging stations.

[0022] Furthermore, other desirable features and characteristics of the disclosed technology will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the disclosure. Summary of the invention

[0023] A first aspect of the present invention is to provide a wireless charging system for wirelessly charging a battery.

[0024] The system includes a transmitter circuit, a receiver circuit, a transmitter controller, and a receiver controller. The transmitter circuit includes a power inverter for driving a primary coil connected in series with a first resonant capacitor. The receiver circuit includes a secondary coil connected in series with a second resonant capacitor and a diode rectifier. The output of the diode rectifier is arranged to directly drive the battery without using an additional battery charging circuit to select a CC charging mode or a CV charging mode to charge the battery. The receiver circuit also includes a bidirectional switch, which has the dual functions of charging the battery and handshaking with the transmitter circuit. The transmitter controller is configured to control the power inverter to switch at a constant high frequency during normal wireless power transmission, and is also configured to receive information generated from the switching action of the bidirectional switch of the receiver circuit during handshake. The receiver controller is configured to: control the receiver circuit to switch at a constant high frequency during normal wireless power transmission, and switch at a low frequency during the handshake process to generate information; convert the battery voltage (V BAT ) and the battery voltage threshold (V OREG ) and compares the battery charging current (I BAT ) and the charging current reference (I BULK ) to automatically select a CC charging mode or a CV charging mode; and configuring the receiver circuit to switch at the same constant high frequency as the transmitter circuit during the battery charging process.

[0025] In certain embodiments, the transmitter controller and the receiver controller are jointly configured to perform at least a battery charging process and a handshake process such that wireless power is transmitted from the primary resonator to the secondary resonator during the battery charging process and such that communication and compatibility checks between the transmitter circuit and the receiver circuit occur during the handshake process.

[0026] In certain embodiments, the bidirectional switch is configured to perform a handshake with the transmitter circuit to inform the transmitter circuit to select the CC charging mode or the CV charging mode to charge the battery.

[0027] In certain embodiments, both the transmitter circuit and the receiver circuit switch at the same high frequency during the battery charging process, while during the handshaking process the transmitter circuit switches at the same high frequency and the receiver circuit switches at a relatively low frequency.

[0028] In certain embodiments, the power inverter is a full-bridge inverter, a half-bridge inverter, or a multi-level inverter.

[0029] In some embodiments, the high frequency is set at the resonant frequency of the secondary resonator formed by the secondary coil and the second resonant capacitor, or at a frequency slightly higher than the resonant frequency of the secondary resonator, to achieve soft switching in the power inverter.

[0030] In certain embodiments, the receiver circuit further includes a first mechanism configured to determine a state of health of the battery after the battery is fully charged, and a second mechanism configured to communicate information related to the charging state to the transmitter circuit.

[0031] In certain embodiments, the transmitter circuit and the receiver circuit are arranged to automatically synchronize switching signals of the transmitter circuit and the receiver circuit at the same high frequency during the battery charging process without using a wireless communication system for feedback and synchronization purposes.

[0032] A second aspect of the present invention is to provide a method for wirelessly charging a battery.

[0033] The method comprises: providing a wireless charging system according to any one of the embodiments disclosed above in the first aspect of the present invention; when the battery voltage V BAT Below the battery voltage threshold (V OREG ) Fig.15 The battery voltage in the battery charging curve automatically selects CC mode and adjusts the battery charging current to I BAT(SC) or I PRECHG or I BULK value; and when V BAT Greater than or equal to V OREG When the battery voltage is adjusted to V OREG .

[0034] In certain embodiments, the method further includes configuring both the transmitter circuit and the receiver circuit to switch at the same high frequency during a battery charging process; and configuring the transmitter circuit to switch at the same high frequency and configuring the receiver circuit to switch at a relatively low frequency during a handshake process.

[0035] In some embodiments, the method further includes: controlling the receiver circuit to switch at a constant high frequency during normal wireless power transfer and to switch at a low frequency during the handshake process to generate information; BAT ) and the battery voltage threshold (V OREG ) and compares the battery charging current (I BAT ) and the charging current reference (I BULK ) to automatically select a CC charging mode or a CV charging mode; and configuring the receiver circuit to switch at the same constant high frequency as the transmitter circuit during the battery charging process.

[0036] In certain embodiments, the method further includes: determining a state of health of the battery after the battery is fully charged; and transmitting information related to the charging state to the transmitter circuit.

[0037] In certain embodiments, the method further includes automatically synchronizing switching signals of the transmitter circuit and the receiver circuit at the same high frequency during the battery charging process without using a wireless communication system for feedback and synchronization purposes.

[0038] Further aspects of the invention are disclosed as shown in the following examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings, in which like reference numerals refer to identical or functionally similar elements throughout the various views and which are incorporated into and form a part of the specification together with the following detailed description, serve to illustrate various embodiments and to explain various principles and advantages according to the present embodiments.

[0040] Figure 1 An example of a wireless charging system is depicted with secondary switches S5 and S6 for communicating based on the Qi standard (using capacitors to change the Rx circuit impedance).

[0041] Figure 2 An example wireless charging system is depicted with a secondary switch S5 for communicating based on the Qi standard (using a resistor to change the Rx circuit impedance).

[0042] Figure 3 Depicted is the use of switches in the Rx circuit to communicate with the Tx circuit.

[0043] Figure 4 The current and voltage characteristics of a typical initial CC and subsequent CV charging mode of a battery are depicted.

[0044] Figure 5 Depicted is a schematic diagram of a wireless charging system using a battery charging circuit with CC and CV mode control between the Rx circuit and the battery load.

[0045] Figure 6 Depicted is a schematic diagram of a Texas Instruments battery charging integrated control circuit that uses a "fixed" battery voltage threshold to select between CC and CV charging modes.

[0046] Figure 7 A first implementation example of the disclosed wireless battery charging system according to certain embodiments of the present invention is depicted (eliminating an additional power stage of a voltage regulator between the output rectifier of the Rx circuit and the battery).

[0047] Figure 8 A second implementation example of the disclosed system according to certain embodiments of the present invention is depicted.

[0048] Fig. 9 A simplified equivalent circuit of a series-series magnetic resonant wireless charging circuit is depicted.

[0049] Fig.10 Depicted are various switching states of the disclosed Rx circuit switches for charging a battery directly through a diode rectifier.

[0050] Fig.11 Various waveforms of the disclosed wireless charging circuit are depicted.

[0051] Fig.12 Typical waveforms for the disclosed Tx and Rx circuits are depicted.

[0052] Fig.13A Typical waveforms of the disclosed Tx and Rx circuits for 0≤γ<π / 2 are depicted.

[0053] Fig. 13B Typical waveforms of the disclosed Tx and Rx circuits for π / 2≤γ<3π / 2 are depicted.

[0054] Fig. 13C Typical waveforms of the disclosed Tx and Rx circuits for 3π / 2≤γ<2π are depicted.

[0055] Fig.14 The disclosed control scheme of the Rx switches S5 and S6 for automatically selecting CC and CV modes is depicted.

[0056] Fig.15 A diagram depicting the detailed battery charging process.

[0057] Fig.16 Depicts the CC charging mode being regulated to follow the battery charging current reference (I BULK ) of the simulated battery charging current (I BAT )’s drawing.

[0058] Fig.17 In CV charging mode, it is regulated to follow the battery charging voltage reference (V OREG ) of the simulated battery charging voltage (V BAT ) of the graph, where V OREG are intentionally set to different levels to show that the controller can vary V BAT To follow V OREG .

[0059] Fig.18 is a flow chart showing the steps of a process performed by the Rx controller to estimate the SoH of a battery load.

[0060] Fig.19 Transmitting SoH information by switching the Rx switch is depicted.

[0061] Fig. 20A functional block diagram showing the steps of deriving a SoH is depicted.

[0062] Fig.21 Depicted is a collection of system waveforms during the process of deriving the state of health (after the charging process has ended).

[0063] Fig. 22 A block diagram of a disclosed wireless charging system is depicted in accordance with an exemplary embodiment of the present invention.

[0064] Fig.23A The simulated waveform of the correlation signal for SoH=0.95 is depicted.

[0065] Fig. 23B The waveform of a simulation of the correlation signal for SoH=0.85 is depicted.

[0066] Fig.24A A conventional example of a high power wireless power transfer (WPT) system with a battery management system (BMS) is depicted.

[0067] Fig. 24B A third implementation example of the disclosed wireless battery charging system for high power applications is depicted in accordance with certain embodiments of the present invention.

[0068] Fig.24C A fourth implementation example of the disclosed wireless battery charging system for high power applications is depicted in accordance with certain embodiments of the present invention.

[0069] Fig.24D An example of a SoH transporting a series of cells of a battery pack is depicted.

[0070] Those skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. DETAILED DESCRIPTION

[0071] The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description.

[0072] The present invention utilizes one or more switches in the Rx circuit not only for the originally intended communication purpose (e.g., as required in the Qi standard) Figure 1 and Figure 2 ), but also for functioning in the battery charging mode. As explained by Wang, OH Stielau and G. Covic, the series compensated secondary (Rx) circuit only provides a "voltage" source, which is only applicable to Figure 3In the present invention, the series-series compensation wireless charging system will use switches previously intended for communication purposes (such as Figure 1 and Figure 2 S5 and S6 in Figure 3 provides a "current" source at the output of the Rx circuit during CC mode in the Rx circuit without the need for an additional battery charging circuit such as Figure 4 and Figure 5 as shown in .

[0073] The present invention relates to a combination of the following aspects.

[0074] 1) Advantageously utilizing the combined use of both the Tx controller and the Rx controller. This combined use includes a newly disclosed switching action in the Rx circuit of the wireless charging system for providing CC and CV charging modes, wherein both the Tx circuit and the Rx circuit switch at the same resonant frequency as the Rx resonant frequency.

[0075] 2) The rectifier output of the Rx circuit is directly used to charge the battery without using an additional battery charging circuit.

[0076] 3) The coordinated use of Tx and Rx controllers and the switching actions of the Tx circuit and the Rx circuit for 1) and 2) can be achieved without any additional wireless communication between the Tx and Rx circuits for signal synchronization. That is, the signal synchronization between the Tx and Rx circuits is automatic.

[0077] 4) The selection of CC mode and CV mode in (i) may be determined by either comparing the battery threshold voltage with the actual battery voltage or comparing the battery SoH threshold with the estimated SoH of the battery.

[0078] Two embodiments of the disclosed wireless charging system involving a power inverter and a series primary resonant tank as a Tx circuit and a secondary resonant tank and a rectifier as an Rx circuit to directly feed the battery (without an additional DC regulator or battery charging circuit) are described in detail. Figure 7 and Figure 8 In the two embodiments, the Tx controller and the Rx controller are used to control the switching of the Tx circuit and the Rx circuit respectively.

[0079] The advantages of the present invention over the prior art are summarized as follows.

[0080] 1) No additional DC regulator or battery charging circuit is required between the output rectifier of the Rx circuit and the battery, making the disclosed wireless battery charging system more energy efficient and cost-reduced.

[0081] 2) No modulated capacitors or resistors are required (as required in the existing Qi standard), thus simplifying the Rx circuit.

[0082] 3) Communication functionality is maintained via modulation of switches in the Rx circuit (such as S5 and S6).

[0083] 4) Provide additional functionality including (i) battery current and voltage control, and (ii) front-end monitoring of the SoH of the battery load.

[0084] All functions, including coupling coefficient monitoring, output current / voltage control, and front-end monitoring of SoH, can be implemented without communication between Tx and Rx. According to some embodiments of the present invention, the coordinated use of Tx and Rx circuits and controllers without an additional wireless communication system is described in detail as follows.

[0085] The Tx circuit includes a power inverter driving a primary coil resonator, which includes a primary coil (L p ) and the series connected capacitor (C p ). p and C p The stray resistance in Figure 7 and Figure 8 Indicated as R p The power inverter includes the Tx (primary) coil (L p ) and the series connected capacitor (C p ) generates an AC rectangular voltage on the primary resonator. The Rx circuit includes an Rx (secondary) coil (L s ) and the series connected capacitor (C s ), L s and C s The stray resistance of this Rx resonator is expressed as R s The Rx resonator feeds a rectifier with a smoothing capacitor across its output, and this rectifier is directly connected to the battery load without using any battery management circuit between the rectifier and the battery. Figure 7 and Figure 8 Switches like S5 and S6 in the rectifier serve a dual purpose. They are used to communicate with the Tx circuit and also to provide a controlled current source output in the rectifier.

[0086] Part A: Using the Rx Controller to Regulate I BAT and V BAT

[0087] Adjustment I BAT and V BAT The goal is to make S R At high frequency (ω R=ω o ) on and off. Fig. 9 A simplified equivalent circuit of a series-series magnetic resonance wireless charging system is shown. R Refers to the switch in the Rx circuit of the present invention for controlling the charging mode of the battery. This Rx circuit switch S R It can be a bidirectional switch including two switches S5 and S6, such as Fig.10 As shown in the figure. Equivalent load R L1 A diode rectifier may be included to feed the battery load, such as Fig.10 as shown in .

[0088] Part A.1: Switching sequences and corresponding waveforms

[0089] Tx switch S T (S1 and S2) and Rx switch S R The switching sequence of (S5 and S6) and v p 、v s 、i s 、i REC ,I BAT and V BAT The corresponding waveform is Fig.11 where: β is v s and γ is the phase shift angle between the switching signals S1 and S5.

[0090] The Rx circuit can operate in four states (states 1 to 4), such as Fig.10 as shown in .

[0091] 1. During state 1 (0<ωt≤β), switch S6 is closed and switch S5 is open. Current i s In the negative direction, it flows through switch S6 and body diode D5, where i s <0,v s =0 and i REC =0.

[0092] 2. During state 2 (β<ωt≤π), switch S6 is closed and switch S5 is open. Current i s In the forward direction, it flows through switch S6 and diode D7, where i s >0,v s =V BAT And i REC =i s .

[0093] 3. During state 3 (π<ωt≤π+β), switch S6 is open and switch S5 is closed. Current i s In the forward direction, it flows through switch S5 and body diode D6, where i s >0,vs =0 and i REC =0.

[0094] 4. During state 4 (π+β<ωt≤2π), switch S6 is open and switch S5 is closed. Current i s In the negative direction, it flows through switch S5 and diode D9, where i s <0,v s =-V BAT And i REC =-i s .

[0095] Based on the equivalent circuit, at the resonant frequency,

[0096]

[0097] and

[0098]

[0099] Where: o is the switching angular frequency; v p1 、v s1 、i p1 and i s1 Yes p 、v s 、i p and i s The basic components of .

[0100] Based on the Fourier series expansion,

[0101]

[0102]

[0103] and

[0104]

[0105] in Yes p1 with i s1 By canceling the term i p1 To simplify (1) and (2), we get

[0106]

[0107] Generally speaking, the compensated capacitor C p and C s is designed near the resonant frequency, thus obtaining

[0108]

[0109] and

[0110]

[0111] Then, for equation (6)

[0112]

[0113] and

[0114]

[0115] By substituting equations (9) and (10) into equation (6), we obtain

[0116] jv p1 ≈ω o Mi s1 (11)

[0117] By substituting equations (3) and (5) into equation (11) and transforming the phasor domain expression into the time domain expression, we obtain

[0118]

[0119] In order to ensure that equation (12) holds, it is required

[0120]

[0121] and

[0122]

[0123] In addition, based on the operating principle of Rx, the following situations will occur. For 0≤γ<π / 2, refer to Fig.13A ,get

[0124]

[0125] For π / 2≤γ<3π / 2, refer to Fig. 13B ,get

[0126]

[0127] For 3π / 2≤γ<2π, refer to Fig. 13C ,get

[0128]

[0129] The charging current and charging voltage are given by the following formulas respectively:

[0130]

[0131] and

[0132]

[0133] Where Z BAT is the equivalent impedance of the battery load. By substituting equation (13) into equations (18) and (19), we obtain

[0134]

[0135] and

[0136]

[0137] Obviously, the charging current and voltage can be controlled by the phase difference (ie, γ) between the switching signals S1 and S5.

[0138] Part A2: Automatic signal synchronization of Tx circuit and Rx circuit and automatic change of CV and CV battery charging mode

[0139] Time synchronization can be achieved by the PI controller without any wireless communication between Tx and Rx. For example, at any operating point, the phase difference (γ) between the switching signals S1 and S5 satisfies 0<=γ<=2. For β satisfying equations (15)-(17) and for a given γ at an operating point, the phase shift β is unique. Fig.14 The feedback control scheme in provides an automatic process to find the value of γ for the reference output voltage. Fig.14 In, V BAT is the measured battery voltage, V OREG is the preset regulated battery voltage reference, I BAT is the measured battery charging current, I BULK It is the controlled charging current reference in CC mode. BAT Lower than V OREG When the CC mode is used, the charging current I BAT Adjusted to I BULK Otherwise (i.e., V BAT ≥V OREG ) should adopt the CV mode.

[0140] For example, the output voltage is 8V, but the reference is 5V. The output voltage measurement of the wireless charging system should detect this and add a phase shift β (e.g., from 45 degrees to 75 degrees). According to equations (15)-(17) (the linear relationship between β and γ), γ will be automatically adjusted to track the output voltage reference (e.g., from 45 degrees to 15 degrees). Since initially γ(0) is a constant value in the control strategy, it can be any degree between 0 and 2π (e.g., 0 degrees or 90 degrees). Then, Δγ will be controlled by the PI controller (e.g., from 45 degrees to 15 degrees for γ(0) = 0 degrees, and from 315 degrees to 285 degrees for γ(0) = 90 degrees).

[0141] In the present invention, it is not necessary to change the operating frequency as a means of changing the CC and CV modes. A control block (a sub-control unit within the overall control scheme) is allowed to control the change of the charging mode. Again, such a control block can be implemented in analog form, digital form, or a combination of both. The CV mode is controlled by Controller-1, which generates Δ γv the phase shift angle during the CV mode. Conversely, the CC mode is controlled by Controller-2, which provides Δ γi the phase shift angle during the CC mode. The selection of the CC mode or the CV mode is determined by the comparison of V BAT with the reference V OREG . The phase shift angle is given by

[0142] Δγ = Δγv + Δγi (22)

[0143] where: Δγi is the change in the phase shift angle between the switching signals S1 and S5 generated by Controller-2 during the CC mode; Δγv is the change in the phase shift angle between the switching signals S1 and S5 generated by Controller-1 during the CV mode; and Δγ is the sum of the control signals Δγi and Δγv. When V BAT < V OREG , that is, in the CC mode, the output of Controller-1 becomes 0, that is, the change in the phase shift angle Δγ = Δγi. Controller-2 will control the charging current to follow the preset current level I BULK . When V BAT ≥ V OREG , that is, in the CV mode, the output of Controller-2 becomes 0, that is, the change in the phase shift angle Δγ = Δγv. Controller-1 will control the charging voltage near the preset value V OREG to charge the battery.

[0144] If the battery is deeply discharged and the voltage satisfies V BAT < V BAT(SC) (for example, for a healthy NCR18650, V BAT(SC) = 2.7V), then the wireless charging system enters the deep pre-charging stage (i.e., 0 < t < t1), and the deep pre-charging current is I BAT(SC) . Generally, I BAT(SC) < 0.05 * I BULK , where I BULK is the charging current reference in the CC stage.

[0145] If the battery voltage satisfies V BAT(SC) ≤ V BAT ≤ V LOWV (for example, for a healthy NCR18650, V LOWV=3V), then the wireless charging system enters the pre-charging stage (i.e., t1≤t≤t2), and the pre-charging current is I PRECHG Generally speaking, I PRECHG <0.1*I BULK .

[0146] If the battery voltage meets V LOWV <V BAT <V OREG (For example, for health NCR18650, V OREG =4.2V), then the wireless charging system enters the CC stage (i.e., t2≤t≤t3), and the constant charging current is I BULK , where V OREG It is the charging voltage reference in the CV stage. Generally speaking, it is 0.2C≤I BULK ≤1C, where C is the rated capacity of the battery.

[0147] If the battery voltage is charged to V OREG , then the wireless charging system enters the CV stage (i.e., t3≤t≤t4), and the constant charging voltage is V OREG At the same time, the charging current gradually decreases until the termination threshold I TERM-TH Once I BAT Drop below I TERM-TH , charging stops and the Rx controller sends SoH information and charging completion notification to the front end.

[0148] Part A3: Verification with simulation results:

[0149] In the simulation study, the duty cycle of S1 and S2 is 0.5. They switch in a complementary manner, such as Fig.11 The inverters in the Tx circuit and the Rx circuit switch at the same constant frequency for battery charging. Fig.16 The evaluation shown in Figure 2 shows how to adjust the battery charge current (I BAT ) to follow the battery charging current (I BULK ). BULK Gradually increase. Fig.16 It can be seen that I BAT Can be adjusted to I BULK . Fig.16 The results in confirm that Fig.14 The controller disclosed in can be applied to Figure 8 The wireless charging circuit in Fig.10 The Rx circuit is used for CC charging mode.

[0150] Another simulation study was performed for CV mode. The battery voltage reference (V OREG ) gradually increase, such as Fig.17As shown in . Fig.17 It can be seen that the battery voltage (V BAT ) to follow V OREG Therefore, it can be seen that Fig.14 Same controller and wireless charging system as the Figure 8 and Fig.10 ) can also be used in CV charging mode without any changes to the switching frequency in the Tx and Rx circuits.

[0151] Part B: Additional information transmission of the SoH from the Rx circuit to the Tx circuit

[0152] In addition to the normal handshake function between the Tx circuit and the Rx circuit, the switch in the Rx circuit can also be used to obtain the SoH to the Tx side for the user's reference. It is important to emphasize that the switching frequency of the Rx switch for handshake or communication purposes can be much lower than the switching frequency used for wireless power transfer. Typically, this frequency can be one-tenth of the frequency used for wireless power transfer. It is also emphasized that the estimation of SoH is performed at the end of the charging cycle (i.e., based on the Fig.15 The charging curve in the figure is after the battery is fully charged).

[0153] Although there are many methods for determining SoH, this section takes the enhanced coulomb counting algorithm as an example. The main content of this section is to demonstrate how to transmit the SoH as information to the Tx side after obtaining it, as information for control purposes or for consumer reference.

[0154] Part B1: Analysis: Estimation of SoH based on the enhanced Coulomb counting algorithm

[0155] SoC is defined as the releasable capacity (C releasable ) relative to the battery rated capacity (C rated ), that is,

[0156]

[0157] A fully charged battery has a maximum releasable capacity (C max ), which can be different from the rated capacity. It can be used to estimate the SoH of the battery. Given

[0158]

[0159] Depth of discharge (DoD) can be expressed as the discharged capacity relative to C rated Therefore,

[0160]

[0161] Among them C released It is the capacity discharged by any amount of current.

[0162] Using the measured charge and discharge current (I BAT ), the difference in DoD during the operating period (τ) can be calculated by the following formula:

[0163]

[0164] Among them I BAT For charging, it is positive. Over time, DoD accumulates, making

[0165] DoD(t)=DoD(t0)+η c ΔDoD (27)

[0166] where η c is the charging efficiency. So

[0167] SoC(t)=SoH(t)-DoD(t) (28)

[0168] If V BAT Reaching the upper limit V OREG And I BAT Drop to lower limit I TERM-Th , then the SoH can be re-evaluated when the battery is fully charged. The new SoH is obtained by accumulating the total amount of power put into the battery, which is equal to the SoC. (Reference: A Closer Look at State of Charge (SOC) and State of Health (SOH) Estimation Techniques for Batteries.)

[0169] Fig.18 The process of estimating SoH is depicted in the flowchart of . It is summarized as follows.

[0170] When V BAT =V OREG , I BAT =I TERM-Th , when SoH = SoC, the battery is fully charged.

[0171] • Close both S5 and S6 and let the battery sit for a while.

[0172] Measure V as the open circuit voltage BAT and battery temperature T, the LUT can be used to estimate the battery's SoH, which is more accurate than other methods.

[0173] SoH=LUT(V BAT ,T) (29)

[0174] The SoH of the battery load, i.e., SoH(t0), ranges from 0 to 1, while the duty cycle of the switching signal S5 also ranges from 0 to 1. Therefore, by modulating the duty cycle D R = SoH switch S5, the SoH information of the battery load can be encoded into the power flow and transmitted from the current i p or compensation capacitor or coil voltage measurement to decode. p The duty cycle is D ip , D ip +D R =1. Therefore, SoH = 1-D ip .

[0175] Part B2: Wireless transmission of SoH information to Tx side

[0176] Once the SoH value has been obtained, such information can be communicated to the Tx circuitry through relatively low-frequency switching of the Rx switch. Fig.19 The simplified circuit in Fig. 20 Functional block diagram and Fig.21 The mechanism is described by a collection of system waveforms in . The essence of this mechanism is to enable the SoH to be able to p1 ) of the fundamental current (i p1 ) export method uses the switching actions of both the Tx switch and the Rx switch.

[0177] and Fig.21 Compared with the Tx switches S1 and S2 indicated in the Rx circuit Fig.19 The bidirectional switch SR in Fig.10 The Tx switches S1 and S2 are still switched at the resonant frequency with a duty cycle of 0.5.

[0178] The steps to derive the SoH value are given below.

[0179] 1. Use a bandpass filter to obtain i p The fundamental component at the resonant frequency (i.e., i p1 )( Fig. 20 ). Due to the low frequency switching of S5 and S6, i p1 It changes accordingly with the low frequency.

[0180] 2.Detect i p1 The peak value (envelope) or RMS value (i.e., i p1_peak ). p1 It is a sinusoidal waveform, so the peak or RMS value can be easily obtained.

[0181] 3. In the current envelope i p1_peak Use the differentiator on to get i p1_diff, which is then compared to a zero voltage level or ground to obtain i p1_pulse . (Note: i p1-peak Form i p1 The “envelope” of

[0182] 4. Use a duty cycle detector (e.g., a pulse width counter) to obtain i p1_pulse The duty cycle (i.e., D ip ).

[0183] 5. Calculate SoH based on the following formula

[0184] SoH=1-D ip (30)

[0185] The overall block diagram of the disclosed wireless charging system having the following features is shown in Fig. 22 The system is characterized by:

[0186] 1. No wireless communication system required;

[0187] 2. During the wireless charging process, for both CC mode and CV charging mode, both the Tx circuit (power inverter) and the Rx circuit have a constant switching frequency;

[0188] 3. The Tx circuit and the Rx circuit switch in coordination and are automatically synchronized;

[0189] 4. Ability to monitor the SoH of the battery at the end of the charging process; and

[0190] 5. Capability to transmit SoH value to Tx circuit.

[0191] Some simulation results are given. The switching frequency of Rx is one thousandth of the switching frequency of Tx (i.e., ω R =ω o / 1000 or f R =f o / 1000). Based on the disclosed method, two case studies with SoH=0.95 and SoH=0.85 have been conducted. The simulated waveforms of the relevant signals are respectively Fig.23A and Fig. 23B From these two result sets, the SoH value matches the target SoH value.

[0192] Part C: The present invention

[0193] The present invention is developed based on further elaboration of the embodiments disclosed above.

[0194] A first aspect of the present invention is to provide a wireless charging system for wirelessly charging a battery. Figure 7 and Figure 8 Explain exemplarily the disclosed wireless charging system, Figure 7 and Figure 8 Both depict exemplary embodiments of the invention.

[0195] Wireless charging system for wirelessly charging batteries 780, 880 (for Figure 7 The system shown in is 700, for Figure 8 The system shown in FIG. 800 includes a transmitter circuit 701, 801, a receiver circuit 702, 802, a transmitter controller 720, 820, and a receiver controller 750, 850. The battery 780, 880 can be a single rechargeable battery, or a series connection of multiple rechargeable batteries, or any arrangement of multiple rechargeable batteries that results in a single equivalent battery. The transmitter circuit 701, 801 includes a power inverter 710, 810 for driving a primary coil 730, 830 connected in series with a first resonant capacitor 732, 832. The receiver circuit 702, 802 includes a secondary coil 740, 840 connected in series with a second resonant capacitor 742, 842 and a diode rectifier 755, 855. The output of the diode rectifier 755, 855 is arranged to directly drive the battery 780, 880 without using an additional battery charging circuit to select a CC charging mode or a CV charging mode to charge the battery 780, 880. The receiver circuit 702, 802 also includes a bidirectional switch 745, 845, which has the dual functions of charging the battery 780, 880 and handshaking with the transmitter circuit 701, 801. The transmitter controller 720, 820 is configured to control the power inverter 710, 810 to switch at a constant high frequency during normal wireless power transmission, and is also configured to receive information generated from the switching action of the bidirectional switch 745, 845 of the receiver circuit 702, 802 during the handshake. The receiver controller 750, 850 is configured to: control the receiver circuit 702, 802 to switch at a constant high frequency during normal wireless power transmission, and to switch at a low frequency during the handshake process to generate information; convert the battery voltage (V BAT ) and the battery voltage threshold (V OREG ) and compares the battery charging current (I BAT ) and the charging current reference (I BULK ) to automatically select the CC charging mode or the CV charging mode; and configuring the receiver circuit 702, 802 to switch at the same constant high frequency as the transmitter circuit 701, 801 during the battery charging process.

[0196] In certain embodiments, the transmitter controller 720, 820 and the receiver controller 750, 850 are jointly configured to perform at least a battery charging process and a handshake process, such that wireless power is transmitted from the primary resonator (formed by the primary coil 730, 830 and the first resonant capacitor 732, 830) to the secondary resonator (formed by the secondary coil 740, 840 and the second resonant capacitor 742, 842) during the battery charging process and such that communication and compatibility checks between the transmitter circuit 701, 801 and the receiver circuit 702, 802 occur during the handshake process.

[0197] In certain embodiments, the bidirectional switch 745 , 845 is configured to perform handshake with the transmitter circuit 701 , 801 to inform the transmitter circuit 701 , 801 to select the CC charging mode or the CV charging mode to charge the battery.

[0198] In certain embodiments, both the transmitter circuit 701 , 801 and the receiver circuit 702 , 802 switch at the same high frequency during the battery charging process, while during the handshake process the transmitter circuit 701 , 801 switches at the same high frequency but the receiver circuit 702 , 802 switches at a relatively low frequency.

[0199] The power inverters 710 , 810 may be full-bridge inverters, half-bridge inverters, or multi-level inverters.

[0200] In certain embodiments, the high frequency is set at a resonant frequency of the secondary resonator or at a frequency slightly higher than the resonant frequency of the secondary resonator to achieve soft switching in the power inverter.

[0201] In some embodiments, the receiver circuit 702 , 802 also includes a first mechanism configured to determine the health status of the battery 780 , 880 after the battery 780 , 880 is fully charged, and a second mechanism configured to transmit information related to the charging status of the transmitter circuit 701 , 801 .

[0202] In certain embodiments, the transmitter circuit 701, 801 and the receiver circuit 702, 802 are arranged to automatically synchronize the switching signals of the transmitter circuit 701, 801 and the receiver circuit 702, 802 at the same high frequency during the battery charging process without using a wireless communication system for feedback and synchronization purposes.

[0203] A second aspect of the present invention is to provide a method for wirelessly charging a battery.

[0204] The method comprises: providing a wireless charging system according to any one of the embodiments disclosed above (such as system 700 or system 800) according to the first aspect of the present invention; when the battery voltage V BATBelow the battery voltage threshold (V OREG ) Fig.15 The battery voltage in the battery charging curve automatically selects CC mode and adjusts the battery charging current to I BAT(SC) or I PRECHG or I BULK value; and when V BAT Greater than or equal to V OREG When the battery voltage is adjusted to V OREG .

[0205] In some embodiments, the method further includes: configuring both the transmitter circuit 701, 801 and the receiver circuit 702, 802 to switch at the same high frequency during the battery charging process; and configuring the transmitter circuit 701, 801 to switch at the same high frequency and configuring the receiver circuit 702, 802 to switch at a relatively low frequency during the handshake process.

[0206] In some embodiments, the method further includes: controlling the receiver circuit 702, 802 to switch at a constant high frequency during normal wireless power transmission, and to switch at a low frequency during the handshake process to generate information; BAT ) and the battery voltage threshold (V OREG ) and compares the battery charging current (I BAT ) and the charging current reference (I BULK ) to automatically select the CC charging mode or the CV charging mode; and configuring the receiver circuit 702, 802 to switch at the same constant high frequency as the transmitter circuit 701, 801 during the battery charging process.

[0207] In certain embodiments, the method further includes determining a state of health of the battery 780 , 880 after the battery 780 , 880 is fully charged; and transmitting information related to the charging state to the transmitter circuit 701 , 801 .

[0208] In certain embodiments, the method further includes automatically synchronizing switching signals of the transmitter circuit 701 , 801 and the receiver circuit 702 , 802 at the same high frequency during the battery charging process without using a wireless communication system for feedback and synchronization purposes.

[0209] Section D: Application of the Invention in High Power Applications (eg, EV)

[0210] Fig.24A A conventional example of a high power WPT system with a BMS is depicted. Fig.24AAs shown in , even with a battery management system (BMS), conventional WPT systems always require a DC regulator for high-power applications (i.e., EV). The function of the DC regulator is to regulate the charging current and voltage (i.e., I BAT and V BAT ), and the function of BMS is to balance the SoC of each single cell in the battery pack.

[0211] Fig. 24B and Fig.24C Depicted are third and fourth implementation examples of the disclosed wireless battery charging system for high power applications. Fig. 24B and Fig.24C As shown in , the strategy proposed in Part A of the present invention is still effective for controlling the charging current and voltage of the entire battery pack.

[0212] For part B of the present invention, the proposed strategy can be directly used to convert the average SoH of the entire battery pack (i.e., ) is sent to the primary side of the high-power WPT system, such as Fig. 24B This strategy can also be extended to be a predefined sequence (ie, SoH = {SoH1, SoH2, ..., SoH n}) Send the SoH of each single battery to the front end, such as Fig.24C as shown in .

[0213] Fig.24D An example of sending a series of SoHs of single cells is shown in FIG. Fig.24D As shown in , if the SoH value detected on the primary side is a sequence from 0 to 1 with an interval of 0.1, it indicates that the monitoring of the SoH of each single cell is started or stopped; if the SoH value detected on the primary side is a sequence from 1 to 0 with an interval of 0.1, it indicates that there is an interruption between two monitorings; and if the SoH value detected on the primary side is constant within N cycles (i.e., N=11 in this example), it indicates the SoH of the nth single cell (i.e., n=1,2,…,n). Therefore, in this example, the SoH of the 1st single cell is 0.5, the SoH of the 2nd single cell is 0.85, and the SoH of the nth single cell is 0.95.

[0214] Although exemplary embodiments have been presented in the foregoing detailed description of the present invention, it should be recognized that there are a large number of variations. It should also be recognized that the exemplary embodiments are merely examples and are not intended to limit the scope, applicability, operation or configuration of the present invention in any way. Rather, the foregoing detailed description will provide a convenient roadmap for implementing exemplary embodiments of the present invention for those skilled in the art, and it should be understood that various changes may be made to the functions and arrangements of the steps and methods of operation described in the exemplary embodiments without departing from the scope of the present invention as set forth in the appended claims.

Claims

1. A wireless charging system for wirelessly charging a battery, the system comprising: a transmitter circuit including a power inverter for driving a primary coil connected in series with a first resonant capacitor; A receiver circuit comprising: a secondary coil connected in series with a second resonant capacitor and a diode rectifier, the output of the diode rectifier being arranged to directly drive the battery without using an additional battery charging circuit to select a constant current (CC) charging mode or a constant voltage (CV) charging mode to charge the battery; and a bidirectional switch having the dual functions of charging the battery and handshaking with the transmitter circuit; a transmitter controller configured to control the power inverter to switch at a constant high frequency during normal wireless power transfer and further configured to receive information generated from switching actions of the bidirectional switch of the receiver circuit during handshaking; and The receiver controller is configured to: controlling the receiver circuit to switch at a constant high frequency during normal wireless power transfer and to switch at a low frequency during a handshake process to generate the information; The battery voltage (V BAT ) and the battery voltage threshold (V OREG ) and compares the battery charging current (I BAT ) and the charging current reference (I BULK ) to compare so as to automatically select the CC charging mode or the CV charging mode; and The receiver circuit is configured to switch at the same constant high frequency as the transmitter circuit during the battery charging process.

2. The system of claim 1 , wherein the transmitter controller and the receiver controller are jointly configured to perform at least the battery charging process and the handshake process such that wireless power is transmitted from the primary resonator to the secondary resonator during the battery charging process and such that communication and compatibility checking between the transmitter circuit and the receiver circuit occurs during the handshake process. 3 . The system of claim 1 , wherein the bidirectional switch is configured to perform a handshake with the transmitter circuit to inform the transmitter circuit to select the CC charging mode or the CV charging mode to charge the battery.

4. The system of claim 2, wherein both the transmitter circuit and the receiver circuit switch at the same high frequency during the battery charging process, and during the handshake process the transmitter circuit switches at the same high frequency and the receiver circuit switches at a relatively low frequency.

5. The system of claim 1, wherein the power inverter is a full-bridge inverter, a half-bridge inverter, or a multi-level inverter.

6. The system of claim 1, wherein the high frequency is set at a resonant frequency of a secondary resonator formed by the secondary coil and the second resonant capacitor, or at a frequency slightly higher than the resonant frequency of the secondary resonator, to achieve soft switching in the power inverter.

7. The system of claim 1, wherein the receiver circuit further comprises a first mechanism configured to determine a state of health of the battery after the battery is fully charged, and a second mechanism configured to transmit information related to the charging state to the transmitter circuit.

8. The system of claim 2, wherein the transmitter circuit and the receiver circuit are arranged to automatically synchronize switching signals of the transmitter circuit and the receiver circuit at the same high frequency during the battery charging process without using a wireless communication system for feedback and synchronization purposes.

9. A method for wirelessly charging a battery, comprising: Providing a wireless charging system as claimed in claim 1; When the battery voltage V BAT Below the battery voltage threshold (V OREG ), the CC mode is automatically selected according to the battery voltage in the battery charging curve and the battery charging current is adjusted to I BA(SC) or I PRECHG or I BULK and When V BAT Greater than or equal to V OREG When the CV mode is selected, the battery voltage is adjusted to V OREG .

10. The method of claim 9, further comprising: configuring both the transmitter circuit and the receiver circuit to switch at the same high frequency during the battery charging process; as well as The transmitter circuit is configured to switch at the same high frequency and the receiver circuit is configured to switch at a relatively low frequency during the handshake process.

11. The method of claim 9, further comprising: controlling the receiver circuit to switch at the constant high frequency during normal wireless power transfer and to switch at the low frequency during the handshake process to generate the information; The battery voltage (V BAT ) and the battery voltage threshold (V OREG ) and compares the battery charging current (I BAT ) and the charging current reference (I BULK ) to compare so as to automatically select the CC charging mode or the CV charging mode; as well as The receiver circuit is configured to switch at the same constant high frequency as the transmitter circuit during the battery charging process.

12. The method of claim 9, further comprising: determining a state of health of the battery after the battery is fully charged; as well as Information related to the charging status is transmitted to the transmitter circuit.

13. The control method according to claim 9, further comprising: Switching signals of the transmitter circuit and the receiver circuit are automatically synchronized at the same high frequency during the battery charging process without using a wireless communication system for feedback and synchronization purposes.

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