Fail-safe safety circuit for wireless power transmission

Abstract

To provide safety circuits that decrease the likelihood of an electric shock caused by a high current source and a high voltage source.SOLUTION: A magnetic inductive resonance charging circuit includes: a resonant network 101 having an inductive secondary coil 104 that converts a magnetic field received from an inductive primary coil into an alternating current (AC) signal; and a synchronous rectifier that rectifies the AC signal to generate a direct current (DC) signal for application to a load. The synchronous rectifier includes a variety of configurations for shunting the AC waveform of an AC current source in the event of a fault. For example, a rectifier controller 115 may hold a pair of normally open switches 107, 108 of the synchronous rectifier off and a pair of normally closed switches 109, 110 of the synchronous rectifier on to shunt the AC current source when an over-voltage, over-current fault condition in a current and voltage sensor 113 or an over-temperature fault condition in a temperature sensor 117 is detected. The capacitive electromagnetic interference produced in the chassis of an electric vehicle is grounded when the resonant network is unbalanced.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This patent application claims the benefit of U.S. Provisional Patent Application No. 63 / 010,771, filed on April 16, 2020, and U.S. Patent Application No. 16 / 952,933, filed on November 19, 2020. These are titled "Safety Circuit for Wireless Power Transmission" and were filed by Volgemuth, John, and are hereby incorporated by reference in their entirety.

[0002] This disclosure relates to the transmission of electrical energy by resonant induction. More specifically, this disclosure relates to system designs, circuit architectures, and details of the implementation of safety circuits that maximize the safety of high-power wireless power transmission systems.

Background Art

[0003] Inductive power transmission has many important applications across a number of industries and markets. The use of inductive power transmission to charge electrical storage devices such as batteries is becoming increasingly common in portable low-power consumer devices.

[0004] The transmission of power between coils using magnetic resonance is well known. As explained by Faraday's law of induction and Lenz's law, an alternating current in a primary (also known as a transmitter) coil forms a magnetic field, and that magnetic field propagates through an air gap to generate a corresponding reverse current in a secondary (also known as a receiver) coil. To charge a battery, the induced alternating current (AC) is converted to direct current (DC). A rectifier converts the alternating current (AC), which periodically reverses direction, to direct current (DC) that flows in only one direction.

[0005] Depending on the AC frequency, the desired DC voltage, or the desired efficiency, a passive rectifier (diode-based) or an active rectifier (MOSFET or switch-based) can be used. Rectifiers typically require additional circuitry to provide the uniform steady voltage and / or voltage level (DC / DC) conversion necessary to charge a battery.

[0006] As the demand for faster charging increases, the need for higher power charging leads to the use of higher voltages and higher currents. Because high current and high voltage sources increase safety hazards, safety circuits are desired to reduce the possibility of electric shock. The following are prior art documents related to the invention of this application (including documents cited in the international phase after the international filing date and documents cited when the application entered the national phase in other countries): (Prior art document) (Patent Document) (Patent Document 1) U.S. Patent Application Publication No. 2016 / 0294221 (Patent Document 2) U.S. Patent Application Publication No. 2015 / 0263511 (Patent Document 3) U.S. Patent Application Publication No. 2017 / 0346343 (Patent Document 4) U.S. Patent Application Publication No. 2010 / 0164296 (Patent Document 5) U.S. Patent Application Publication No. 2016 / 0025821 (Patent Document 6) U.S. Patent Application Publication No. 2019 / 0084433 [Overview of the project] [Means for solving the problem]

[0007] Various details relating to embodiments of the subject matter of the present invention are provided in the accompanying drawings and the following detailed description.

[0008] The systems and methods described herein enhance safety against electric shock during wireless power transmission by providing a mechanism for shunting power in the event of failure. In an exemplary embodiment, a magnetic induction resonant charging circuit is provided. This magnetic induction resonant charging circuit includes a resonant network having an inductive secondary coil, the inductive secondary coil converting a magnetic field received from an inductive primary coil into an alternating current (AC) signal, and a synchronous rectifier that rectifies the AC signal to generate a direct current (DC) signal for application to a load being charged. The synchronous rectifier further includes means for shunting the AC waveform in the event of failure. In an exemplary configuration, the secondary coil is mounted on an electric vehicle, and the load is the battery of the electric vehicle.

[0009] In an exemplary embodiment, the resonant network includes first and second balanced capacitors connected in series to each end of the secondary coil, so that the AC signal resonates in series with the first and second capacitors. The synchronous rectifier has a pair of normally open switches and a pair of normally closed switches, one of the pair of normally open switches and one of the pair of normally closed switches connected to the first balanced capacitor, and the other of the pair of normally open switches and the other of the pair of normally closed switches connected to the second balanced capacitor. The shunting means has the normally closed switches that shunt the secondary coil in the event of a failure. The normally open switches are configured to prevent a short circuit of the load in the event of a failure. A signal conditioning circuit may be provided that outputs a regulated DC signal for adjusting the DC signal and applying it to the load.

[0010] In exemplary embodiments, a first current and voltage sensor may be provided to monitor the AC signal input from the resonant circuit to the synchronous rectifier, and a second current and voltage sensor may be provided to monitor the adjusted DC waveform applied to the load. The rectifier controller may provide control signals that are phase-synchronized to the AC signal output by the resonant network in response to the values ​​measured by the first and second current and voltage sensors, and control the switching of the pair of normally open switches and the pair of normally closed switches according to the measured values. A temperature sensor may be provided to detect an overheating fault condition of the synchronous rectifier and provide a detection signal to the rectifier controller.

[0011] In other exemplary embodiments, the charging circuit further includes a charging processor that receives input AC signal amplitude, input AC signal frequency, regulated DC waveform voltage, regulated DC waveform current, and / or the temperature of the synchronous rectifier from the rectifier controller and instructs the rectifier controller to operate to provide, for example, protection from detected fault conditions. The charging processor instructs the rectifier controller to turn on and off the pair of normally open switches and the pair of normally closed switches at near zero crossing of the AC signal from the resonant network when the AC signal frequency is within an acceptable range, the root mean square of the AC signal is above a threshold, and no fault is detected. On the other hand, if a fault condition is detected, the charging processor disables the rectifier controller by keeping the pair of normally open switches off and the pair of normally closed switches on. For example, if the second current and voltage sensors detect an overvoltage or overcurrent fault condition, or if the temperature sensor detects an overheating fault condition, the rectifier controller may keep the pair of normally open switches off and the pair of normally closed switches on.

[0012] In further exemplary embodiments, the resonant network may have an alternating current (AC) current source, and the synchronous rectifier may have a first pair of diodes connected to the first and second leads of the AC current source, respectively, and a second pair of diodes connected to the first and second leads of the AC current source, respectively. The shunting means may have a first normally closed switch connected in parallel with the first diode of the second pair of diodes, and a second normally closed switch connected in parallel with the second diode of the second pair of diodes. The first and second normally closed switches shunt the AC current source in the event of failure.

[0013] In further exemplary embodiments, the resonant network may have an alternating current (AC) current source, and the synchronous rectifier may have a first pair of diodes connected to the first and second leads of the AC current source, respectively, and a second pair of diodes connected to the first and second leads of the AC current source, respectively. The shunting means may have a normally closed safety switch connected between the first and second pairs of diodes. The normally closed safety switch shunts the AC current source in the event of a failure.

[0014] In further exemplary embodiments, the resonant network may have an alternating current (AC) current source, and the synchronous rectifier may have a first pair of normally-open switches connected to the first and second leads of the AC current source, respectively, and a second pair of normally-open switches connected to the first and second leads of the AC current source, respectively. The shunting means may have a normally-closed safety switch connected between the first and second pairs of normally-open switches. The normally-closed safety switch shunts the AC current source in the event of a failure.

[0015] In exemplary embodiments, the resonant network can be balanced or unbalanced. Various configurations can be used.

[0016] The resonant network may be a balanced parallel-parallel resonant network (PPRN) having an inductive primary coil, a first resonant capacitor in parallel with the primary coil, a secondary coil, and a second resonant capacitor in parallel with the secondary coil.

[0017] The resonant network may be an unbalanced series-series resonant network (SSRN) having an inductive primary coil, a first resonant capacitor in series with the primary coil, a secondary coil, and a second resonant capacitor in series with the secondary coil.

[0018] The resonance network may be an unbalanced parallel - series resonance network (PSRN) having an inductive primary coil, a first resonance capacitor in parallel with the primary coil, the secondary coil, and a second resonance capacitor in series with the secondary coil.

[0019] The resonance network may be an unbalanced series - parallel resonance network (SPRN) having an inductive primary coil, a first resonance capacitor in series with the primary coil, the secondary coil, and a second resonance capacitor in parallel with the secondary coil.

[0020] The resonance network may be a balanced PSRN having an inductive primary coil, a first resonance capacitor in parallel with the primary coil, the secondary coil, a second resonance capacitor in series with the secondary coil at the first end of the inductive coil, and a third resonance capacitor in series with the secondary coil at the second end of the secondary coil.

[0021] The resonance network may be a balanced SPRN having an inductive primary coil, a first resonance capacitor in series with the primary coil at the first end of the primary coil, a second resonance capacitor in series with the primary coil at the second end of the primary coil, the secondary coil, and a third resonance capacitor in parallel with the secondary coil.

[0022] The resonance network may be a balanced SSRN having an inductive primary coil, a first resonance capacitor in series with the primary coil at the first end of the primary coil, a second resonance capacitor in series with the primary coil at the second end of the primary coil, the secondary coil, a third resonance capacitor in series with the secondary coil at the first end of the secondary coil, and a fourth resonance capacitor in series with the secondary coil at the second end of the secondary coil.

[0023] In an exemplary embodiment, the resonant network may further include an inductive primary coil having a rectangular coil winding, and the rectangular coil winding is disposed on at least one side of an insulating substrate. The resonant capacitor may be connected in series to a first end of the rectangular coil winding, and a second end of the rectangular coil winding may be connected to ground. As a result, the rectangular coil winding has a common-mode voltage that is half of the voltage of the resonant capacitor with respect to ground, whereby the rectangular coil winding can become a capacitive electromagnetic interference radiator.

[0024] In another exemplary embodiment, a first resonant capacitor may be connected in series to a first end of the rectangular coil winding, and a second resonant capacitor may be connected in series to a second end of the rectangular coil winding. In such a configuration, a midpoint between the first end and the second end of the rectangular coil winding becomes substantially ground, whereby the rectangular coil winding does not radiate capacitive electromagnetic interference.

[0025] In a further exemplary embodiment, techniques are provided for reducing capacitive electromagnetic interference (EMI) radiated when the resonant network is unbalanced. According to a first technique, the electric vehicle is equipped with tires having conductive vias that ground the EMI during charging. According to a second technique, the electric vehicle has a ground cable that grounds the EMI during charging. According to a third technique, the electric vehicle has a circuit powered by the battery of the electric vehicle and having a circuit that cancels out a phase-shifted voltage during charging.

[0026] In another embodiment, a magnetic induction resonant charging circuit is provided for charging the battery of an electric vehicle, comprising: a resonant network having an inductive secondary coil in the electric vehicle, the inductive secondary coil converting a magnetic field received from an inductive primary coil into an alternating current (AC) signal, the resonant network being unbalanced and thereby radiating capacitive electromagnetic interference (EMI); a synchronous rectifier for rectifying the AC signal to generate a direct current (DC) signal for application to the battery of the electric vehicle; and means for grounding the EMI during charging. In an exemplary embodiment, the means for grounding the EMI during charging may be a tire of the electric vehicle, in which case the tire is provided with conductive vias for grounding the EMI during charging. Alternatively, the means for grounding the EMI during charging may be a grounding cable connected to the electric vehicle to ground the EMI during charging. In another embodiment, the means for grounding the EMI during charging may be a circuit powered by the battery of the electric vehicle that cancels out-of-phase voltages during charging.

[0027] This abstract is provided to introduce aspects of the subject matter of the invention in a simplified form and follows the main body of the detailed description, which provides a further description of the subject matter of the invention. This abstract is not intended to identify essential or necessary features of the claimed subject matter, and no particular combination or order of elements listed in this abstract is intended to limit the elements of the claimed subject matter. Rather, it will be understood that the following section provides some summarized examples of embodiments described in the following detailed description. [Brief explanation of the drawing]

[0028] The aforementioned and other beneficial features and advantages of the present invention will become apparent from the following detailed description relating to the accompanying drawings. [Figure 1] Figure 1 schematically shows an embodiment of a high-level circuit for a magnetic resonance induction system with enhanced safety. [Figure 2]Figure 2 schematically shows a typical safety circuit for a voltage source with a reactive load. [Figure 3] Figure 3 schematically shows a typical safety circuit for a current source with a reactive load. [Figure 4A] Figure 4A schematically shows switch-based synchronous rectification of an AC voltage source with complex load impedance. [Figure 4B] Figure 4B schematically shows switch-based synchronous rectification of an AC current source with complex load impedance. [Figure 4C] Figure 4C schematically shows switch-based synchronous rectification of an AC voltage source with a DC voltage load. [Figure 4D] Figure 4D schematically shows switch-based synchronous rectification of an AC current source with a DC voltage load. [Figure 5A] Figure 5A schematically shows passive rectification of an AC voltage source with an impedance load. [Figure 5B] Figure 5B schematically shows passive rectification of an AC current source with an impedance load. [Figure 5C] Figure 5C schematically shows an alternative embodiment of passive rectification of an AC current source with an impedance load. [Figure 6] Figure 6 schematically shows an alternative embodiment of switch-based synchronous rectification of an AC current source with an impedance load. [Figure 7A] Figure 7A schematically shows a parallel-parallel resonant induction circuit. [Figure 7B] Figure 7B schematically shows an unbalanced series-series resonant induction circuit. [Figure 7C] Figure 7C schematically shows a hybrid parallel-unbalanced series resonant induction circuit. [Figure 7D] Figure 7D schematically shows a hybrid unbalanced series-parallel resonant induction circuit. [Figure 7E] Figure 7E schematically shows a hybrid parallel-balanced series resonant induction circuit. [Figure 7F] Figure 7F schematically shows a hybrid balanced series-parallel resonant induction circuit. [Figure 7G] Figure 7G schematically shows a balanced series-series resonant induction circuit. [Figure 8] Figure 8 shows the geometry of a coil used in a magnetic resonance induction power system. [Figure 9] Figure 9 schematically shows an unbalanced circuit corresponding to a planar coil for use in a resonant induction power system. [Figure 10] Figure 10 schematically shows a balanced circuit corresponding to a planar coil used in a resonant induction power system. [Figure 11] Figure 11 shows the parasitic electric field of a resonant induced power system in an electric vehicle equipped with an unbalanced resonant network. [Modes for carrying out the invention]

[0029] Exemplary embodiments of the present invention are described with reference to the drawings. Current source safety circuits and related methods described herein can be more readily understood by referring to the following detailed description provided in conjunction with the accompanying drawings and examples that form part of this disclosure. This description is not limited to any specific product, method, condition, or parameter described and / or shown herein, and it will be understood that the terms used herein are intended to describe specific embodiments merely as examples and are not intended to limit the claimed subject matter. Similarly, descriptions of possible mechanisms or operating mechanisms or reasons for improvement are for illustrative purposes only, and the subject matter described herein should not be limited by the correctness of such proposed mechanisms or operating mechanisms or reasons for improvement. Throughout this text, it will be understood that this description refers to both methods and systems / software for carrying out such methods.

[0030] Next, a detailed description of exemplary embodiments will be given with reference to Figures 1 to 11. This description provides detailed examples of possible embodiments, but it should be noted that these details are illustrative and not in any way limit the scope of the subject matter of the present invention.

[0031] In wireless power transmission systems using open-air transformers, the resonant network used for magnetic / wireless charging (i.e., primary / transmitter and secondary / receiver) forms an AC current source for rectification in the vehicle. The presence of a current source largely reverses the voltage source-specific requirements for power supplies in household and industrial scenarios. The main difference from these scenarios is that short circuits are bad in voltage sources. Consequently, power conversion topologies are constructed with normally-off devices to avoid short circuits. However, the opposite is true for current sources; open circuits are bad. This means that typical rectification techniques are undesirable. Straight-passive (such as diode-based) rectifiers offer no protection. Conventional synchronous rectifiers can offer protection, but only if there is a reliable means of powering the device and turning it on.

[0032] Figure 1 schematically shows a high-level schematic diagram of a DC battery charging circuit using magnetic induction resonance. The resonant network 101 (also known as the receiver or secondary) has an inductive secondary coil 104 and balanced capacitors 105 and 106. The secondary coil 104 converts the magnetic field from a charging transmitter (not shown) into an alternating current (AC) signal that resonates in series with the voltage domain balanced capacitors 105 and 106. As will be explained below with respect to Figures 7A to 7G, the primary side of the resonant network can be balanced or unbalanced. Next, the AC signal from the resonant network 101 is rectified into a direct current (DC) signal by a rectifier stage 102. The rectifier stage 102 has a synchronous rectification circuit using a pair of normally open (NO) switches 107 and 108 and a pair of normally closed (NC) switches 109 and 110. As described below, the paired NC switches 109 and 110 function to shunt the secondary coil 104 in case of failure. The DC signal is passed to the adjustment circuit 111, which outputs an adjusted DC signal used to charge the battery 112.

[0033] The rectifier controller 115 is phase-locked to the resonant network current at the first current and voltage sensor 113 as a reference for controlling the timing of the rectifier switches 107-110 (for example, for detected zero crossings). The rectifier controller 115 (nominal, field-programmable gate array (FPGA) or conventional microcomputer) generates estimates of the amplitude, frequency, and instantaneous phase of the input AC waveform from the secondary coil 104 via the first current and voltage sensor 113, provided that the AC waveform has sufficient amplitude and the switching frequency is within its acquisition range. The rectifier controller 115 also monitors the amplitude of the output DC current waveform applied to the battery 112 via the second current and voltage sensor 114.

[0034] The vehicle charging processor 116 (typically implemented as software running on a microprocessor) can handle communication between the internal subsystem (Wireless Power Transfer (WPT) system) and the external vehicle system via an interface (e.g., a Controller Area Network (CAN) bus) and can instruct the operation of the rectifier controller 115. For example, when queried by the vehicle charging processor 116, the rectifier controller 115 may report the amplitude of the input AC signal, the frequency of the input AC signal, the voltage and current of the DC output, and the temperature of the switching devices. If the reported input switching frequency is within an acceptable closed range (e.g., 79 kHz to 90 kHz), the AC root mean square (RMS) exceeds a threshold (e.g., 5 amperes), and no faults have been detected, the vehicle charging processor 116 can instruct the rectifier controller 115 to maximize rectification efficiency by turning the upper pair of NO switches 107 and 108 and the lower pair of NC switches 109 and 110 on and off at appropriate zero crossings of the input AC waveform. The nominal state is "started" or "safe," in which case the upper pair of NO switches 107 and 108 are open and the lower pair of NC switches 109 and 110 are closed. When the secondary coil 104 is generating a positive signal, the first set of switches 107 and 109 are opened and the second set of switches 108 and 110 are closed. When the signal from the secondary coil 104 is reversed, the first set of switches 107 and 109 are closed and the second set of switches 108 and 110 are opened. This sequence is repeated to generate the output signal, which is mathematically the absolute value of the input AC signal.

[0035] If disabled by the vehicle charging processor 116, the rectifier controller 115 holds the upper NO switch pair 107 and 108 off and the lower NC switch pair 109 and 110 on. Also, if an overvoltage or overcurrent fault condition is detected by the current and voltage sensor 114, or if an overheating fault condition is detected by the temperature sensor 117, the rectifier controller 115 holds the upper NO switch pair 107 and 108 off and the lower NC switch pair 109 and 110 on to shunt the current from the secondary coil 104.

[0036] The rectifier controller 115 monitors the output DC voltage from the rectifier stage 102 using current and voltage sensors 114. The rectifier controller 115 also measures the output DC current using current and voltage sensors 114 and reports this output DC current to the vehicle charging processor 116, so that the total power supplied by the system to the battery 112 can be calculated. Furthermore, the rectifier controller 115 may monitor the temperature sensors or a set of sensors (e.g., a thermistor or a network of thermistors) 117 that measure the temperature of the mounting plates of the rectifier switching devices 107-110. This mounting plate temperature represents the case temperature of the switching devices 107-110, which is related to the power loss by the switching devices 107-110.

[0037] When combined with a series-to-series resonant transmitter (not shown), the resonant network 101 is an AC current source. Open-circuiting the resonant network 101 results in a dangerous condition. However, the aforementioned selection of NO switches 107 and 108 and NC switches 109 and 110 of the synchronous rectifier stage 102 makes the system inherently safe. Under normal conditions, the NC switches 109 and 110 can be closed, either accidentally or specifically controlled, to shunt the secondary coil 104, thus providing a means to shunt the AC current source of the resonant network 101. NO switches 107 and 108 prevent short circuits of the output network 103, particularly the battery 112.

[0038] In the event of a malfunction, the battery 112 is disconnected from the signal adjustment circuit 111. The current flowing through the adjustment circuit 111 remains unchanged, but the current flowing out of the adjustment circuit 111 decreases to zero. As a result, the voltage through the adjustment circuit 111 and the rectifier stage 102 increases at a rate proportional to the rectified current and the impedance of the adjustment circuit 111.

[0039] The rectifier controller 115 uses current and voltage sensors 114 to monitor voltage and / or current to detect disconnection of the battery 112. In case of failure, the rectifier controller 115 can respond by opening NO switches 107 and 108 and closing NC switches 109 and 110. This acts to disconnect the resonant network 101 from the regulating circuit 111 and the battery 112. Power transmission immediately stops when the flow of rectified current from the rectifier stage 102 to the regulating circuit 101 and the battery 112 is interrupted by NO switches 107 and 108, and the flow of current from the resonant network 101 is shunted to NC switches 109 and 110.

[0040] In a passive state where there is no control force to operate the controller or synchronously rectify, NO switches 107 and 108 open the output network 103, and NC switches 109 and 110 shunt the resonant network 101. This protects the charger, load, and service personnel from spurious energy picked up by the resonant network 101, whether the spurious energy is accidental or intentional.

[0041] Figure 2 schematically illustrates a typical safety circuit for a voltage source with a reactive load. Figure 2 shows a protection solution for a typical voltage source supply where the voltage source 201 and load 202 share a common ground 203. The voltage source 201 provides a fixed voltage that is constant with respect to the source current. The source current is set by the load impedance of load 202. A current sensor 205 monitors the source current. If the source current exceeds the permissible limit, the current sensor 205 provides protection by triggering a normally open switch 204 to the open position. The normally open switch 204 remains open until reset. When the normally open switch 204 is triggered to close, the voltage and current across load 202 are reduced to zero. The normally open (NO) switch 204 and current sensor 205 shown herein are just one implementation option with a variety of widely used relays, circuit breakers, and fuses. As shown in Figure 2, virtually all power and distribution networks operate with voltage sources and implement some kind of current limiting scheme using some form of breaker or fuse. In voltage-source power systems, it is understood that open circuits are good and short circuits are bad.

[0042] The current source supply embodiment shown in Figure 3 is not very common. In constant current power supplies, the best safety protection measures found in more common voltage source power supplies must be faithfully implemented. In current source power systems, unlike voltage source power systems, it will be understood that open circuits are not good, and shunts (intentional short circuits) are a good implementation. Therefore, the different embodiments of safety circuits described herein should be considered based on whether the power supply is a current source power system or a voltage source power system.

[0043] Figure 3 schematically shows a typical safety circuit for a current source with a reactive load. The current source 301 supplies current to the reactive load 302 regardless of the voltage across it. In this example, all circuit paths share a common ground 303. The current source 301 provides a fixed current that is invariant with respect to voltage current.

[0044] A voltage-sensitive disconnector is placed in parallel with the reactive load 302 to provide a current shunt and isolation of the load from its source (and vice versa). The normally closed (NC) switch shunt 304 and voltage sensor 305 shown in Figure 3 are just one implementation option of a widely used shunting mechanism with various switches, relays, circuit breakers, and fuses. When the NC switch shunt 304 is triggered by the voltage sensor 305, the NC switch shunt 304 opens, moving the voltage and current flow through the reactive load 302 to zero.

[0045] Figures 4A to 4D all illustrate alternative embodiments of safety rectifier circuits and additional subsystems required for wireless power transmission.

[0046] Figure 4A schematically illustrates switch-based synchronous rectification of an AC voltage source with complex load impedance. Specifically, Figure 4A shows a conventional AC voltage source and a safety-enhanced synchronous rectification circuit for forming a DC voltage source. The AC voltage source 401 is synchronously rectified by a set of normally open (NO) switches 402, 403, 404, and 405. A power regulating network 406 filters the rectified DC voltage to provide a DC voltage source for the load 407. In case of failure, the NO switches open as faults, protecting the load 407 by disconnecting it from the AC voltage source 401.

[0047] Figure 4B schematically illustrates switch-based synchronous rectification of an AC current source with complex load impedance in an exemplary embodiment. Specifically, Figure 4B shows an AC current source and a safety-enhanced synchronous rectification circuit for forming a DC current source. The AC current source 410 is synchronously rectified by a set of NO switches 403 and 404 and normally closed (NC) switches 408 and 409. A power regulating network 406 filters the rectified current to make it a DC current source for the load 407. The AC current source 410 needs to open the set of NC switches 408 and 409 to provide a means of shunting the current in the event of a fault. In a fault condition, the closed switches 408 and 409 isolate the load 407 from the AC current source 410 to prevent power backflow.

[0048] Figure 4C schematically illustrates switch-based synchronous rectification of an AC voltage source with a DC voltage load. Specifically, Figure 4C shows an AC voltage source and a safety-enhanced synchronous rectification circuit for forming a DC voltage source for battery charging. The AC voltage source 401 is synchronously rectified by a set of NO switches 402, 403, 404, and 405. A power regulating network 406 filters the rectified voltage to make it a DC voltage source for the power conversion stage 411. The power conversion stage 411 adapts the DC voltage source to the voltage required to charge the battery 412.

[0049] Figure 4D schematically illustrates switch-based synchronous rectification of an AC source with a DC voltage load in an exemplary embodiment. Specifically, Figure 4D shows an AC current source and a safety-enhanced synchronous rectification circuit for forming a DC voltage source for battery charging. The AC current source 410 is synchronously rectified by a set of NO switches 402 and 403 and NC switches 408 and 409. A power regulating network 406 filters the rectified current to make it a DC current source for the battery 412. The AC current source 410 requires the set of NC switches 408 and 409 to provide a means of shunting the current in case of failure. However, since this system is powered from the current source, the power conversion stage 411 in Figure 4C is not required for battery charging.

[0050] Figure 5A schematically illustrates passive rectification of an AC voltage source with an impedance load. Specifically, Figure 5A schematically illustrates a conventional passive full-wave rectifier circuit for an AC voltage source 501. Diodes 502, 503, 504, and 505 function as one-way gates to generate full-wave rectification of the AC signal. A power adjustment stage 506 helps to smooth the rectifier voltage output applied to the load 507, enabling charging of the load 507.

[0051] As with all diode circuits, the reverse recovery time and voltage drop in the forward bias state affect the efficiency of the rectifier circuit. Passive rectifier circuits do not require a controller stage. However, in the event of a failure, the AC voltage source 501 remains connected to the load 507 via the power adjustment stage 506, exposing the load 507 to the voltage source failure (and vice versa).

[0052] Figure 5B schematically illustrates passive rectification of an AC current source with an impedance load in an exemplary embodiment. Specifically, Figure 5B shows a hybrid embodiment of a safety-enhanced circuit for rectifying the AC current source 508. Full-bridge passive rectifier diodes 502, 503, 510, and 512 are complemented by normally closed (NC) switches 509 and 511. Diodes 502, 503, 510, and 512 function as one-way gates to generate full-wave rectification. NC switches 509 and 511 function as means to shunt in case of failure, preventing overvoltage damage between the AC current source 508 and diodes 502, 503, 510, and 512. A power regulating stage 506 helps to smooth the rectifier voltage output applied to the load 507, enabling charging of the load 507.

[0053] As with all diode-based rectifier circuits, the reverse recovery time and voltage drop in the forward bias state affect the efficiency of the rectifier circuit. This passive rectifier circuit does not require a controller stage, but a controller (e.g., rectifier controller 115) is required to command the NC switches 509 and 511.

[0054] Figure 5C schematically illustrates an alternative passive rectifier for an AC current source with an impedance load in an exemplary embodiment. Figure 5C shows an alternative semi-passive embodiment of a safety-enhanced full-wave rectifier circuit for the AC current source 508. Diodes 502, 503, 510, and 512 function as one-way gates to generate full-wave rectification. A power regulating stage 506 helps to smooth the rectifier voltage output applied to the load 507, enabling charging of the load 507. In this embodiment, a normally closed (NC) shunt switch 513 is located in the circuit. In the event of a failure or command option, the shunt switch 513 shunts the current in the rectifier circuit, preventing damage to the power regulating stage 506 and the load 507.

[0055] This embodiment is a less expensive implementation with simpler control. However, its efficiency is lower. Furthermore, it produces a high dV / dt across the isolated control boundary of the shunt switch 513. As with all diode-based rectifier circuits, the reverse recovery time and voltage drop in the forward bias state affect the efficiency of the rectifier circuit.

[0056] Figure 6 schematically illustrates an alternative switch-based synchronous rectification of an AC current source with an impedance load in an exemplary embodiment. Specifically, Figure 6 shows an alternative safety circuit for active rectification of the AC current source 601. A power regulating stage 606 helps to smooth the rectifier voltage output applied to the load 607 being charged. Full-wave rectification is achieved by alternately switching at the zero crossing of the sinusoidal output of the AC current source 601. A normally closed (NC) safety switch 608 is positioned between the upper normally open (NO) rectifier switches 602 and 604 and the lower normally open (NO) rectifier switches 603 and 605 to provide a means for shunting the current in the rectifier circuit in the event of a failure or command option, thereby preventing damage to the power regulating stage 606 and the load 607.

[0057] In the event of a fault or loss of rectification control, the NO rectifier switches 602, 603, 604, and 605 fail in the open position (or are commanded to be open), while the NC safety switch 608 fails in the closed position. Thus, while the load is isolated by the NC safety switch 608, the current is shunted back to the AC current source 601. This embodiment reduces the demand for normally closed (NC) switches by using an additional switch 608.

[0058] In resonant induction wireless charging, there are four possible two-pole networks: parallel-parallel resonant networks (PPRN) and series-series resonant networks (SSRN). Galvanic isolation also allows for the formation of parallel-series resonant networks (PSRN) and series-parallel resonant networks (SPRN). PPRN, PSRN, and SPRN all operate as AC Voltage Controlled Voltage Sources (VCVS) when the load impedance is greater than the network impedance, and as AC Voltage Controlled Current Sources (VCCS) when the load impedance is less than the network impedance. SSRN, on the other hand, operates as a VCCS for all load impedances. A constant voltage load, such as a battery, behaves as a variable load impedance as the power level changes. A battery behaves as a high-impedance load at low power and as a low-impedance load at high power. At high power, all four resonant networks will operate as VCCS.

[0059] When operating as VCCS, the transconductance (G) of the PPRN is k / (w*L) in units of amperes / volt, where k is the unitless magnetic coupling coefficient of the primary and secondary inductors in the range of 0 to 1, w is the resonant frequency of the network in units of radians / second, and L is Henry's geometric mean of the primary and secondary inductors. When operating as VCCS, the G of the PSRN, SPRN, and SSRN is 1 / (w*L*k). This is because, with a fixed G, the inductor of the PPRN is k 2 It is only small, and the PPRN capacitor is k -2 This simply means it's much larger. This is undesirable because capacitors are far more expensive components.

[0060] A resonant network resonates an energy S proportional to P / k, where P is the power passing through the network. For typical values ​​of k (e.g., 0.05 to 0.2), S is 5 to 20 times higher than P. In a parallel resonant branch, the resonant power is considered to be the current flowing through the capacitive and inductive elements. In a series resonant branch, the resonant power is considered to be the additional voltage across the capacitive and inductive elements. For example, in a 500V, 125A system with k = 0.1, in parallel resonance, 125A / 0.1 or 1,250A resonates in the inductor and capacitor, while in series resonance, 500V / 0.1 or 5,000V resonates in the inductor and capacitor. Series resonance is preferable because it requires additional insulation at higher voltages and additional conductors at higher currents, and the higher voltages allow for lighter and more compact products.

[0061] With these considerations in mind, PSRN, SPRN, and SSRN can each have both balanced and unbalanced topologies. PPRN has only a balanced topology. Each of these topologies is shown in Figures 7A to 7G.

[0062] Figure 7A schematically shows a balanced PPRN circuit in an exemplary embodiment. This resonant network includes a ground induction coil 701, a ground parallel resonant capacitor 703, a vehicle induction coil 702, and a vehicle parallel resonant capacitor 704.

[0063] Figure 7B schematically shows an unbalanced SSRN circuit in an exemplary embodiment. This resonant network includes a ground induction coil 701, a ground series resonant capacitor 705, a vehicle induction coil 702, and a vehicle series resonant capacitor 706.

[0064] Figure 7C schematically shows an unbalanced PSRN circuit in an exemplary embodiment. This resonant network includes a ground induction coil 701, a ground parallel resonant capacitor 707, a vehicle induction coil 702, and a vehicle series resonant capacitor 708.

[0065] Figure 7D schematically shows an unbalanced SPRN circuit in an exemplary embodiment. This resonant network includes a ground induction coil 701, a ground series resonant capacitor 709, a vehicle induction coil 702, and a vehicle parallel resonant capacitor 710.

[0066] Figure 7E schematically shows a balanced PSRN circuit in an exemplary embodiment. This resonant network includes a ground induction coil 701, a ground parallel resonant capacitor 711, a vehicle induction coil 702, and a pair of vehicle series resonant capacitors 712 and 713.

[0067] Figure 7F schematically shows a balanced SPRN circuit in an exemplary embodiment. This resonant network includes a ground induction coil 701, a pair of ground series resonant capacitors 714 and 715, a vehicle induction coil 702, and a vehicle parallel resonant capacitor 716.

[0068] Figure 7G schematically shows a balanced SSRN circuit in an exemplary embodiment. This resonant network includes a ground induction coil 701, a pair of ground series resonant capacitors 717 and 718, a vehicle induction coil 702, and a pair of vehicle series resonant capacitors 719 and 720.

[0069] Figure 8 geometrically shows a planar coil 801 for use as a primary coil in a magnetic resonant induction power system in an exemplary embodiment. Although shown as a rectangular coil, other shapes (e.g., classic round coils or rectangles) are also possible. The coil winding 803 is arranged on an insulating substrate 805 and may include individual conductive ribbons (e.g., printed circuit boards), insulated wire strands (e.g., Litz wire), etc. Vias 802 and 804 allow connection to other coils on the opposite side of the insulating substrate 805.

[0070] Figure 9 schematically shows an unbalanced circuit equivalent to the planar coil 801 used in the series resonant network 901 in an exemplary embodiment. The series resonant network 901 is a transmitter. Terminals 906 and 907 of the network are connected to an inverter. The resonant capacitor 905 has a high-voltage, high-frequency voltage across it when the series resonant network 901 resonates. The same voltage is observed across the inductor 903. The first terminal 904 of the inductor 903 is efficiently held at ground potential. The second terminal 902 of the inductor is exposed to the full voltage of the resonant capacitor 905 relative to ground. That is, the voltage across the inductor 903 has a common-mode voltage relative to ground that is half the voltage across the resonant capacitor 905, thereby making the inductor 903 a capacitive electromagnetic interference (EMI) radiator. In this configuration, techniques for mitigating EMI radiation are desirable, as shown below with respect to Figure 11.

[0071] Figure 10 schematically shows a balanced circuit equivalent to the planar coil 801 used in the series resonant network 1001 in an exemplary embodiment. The series resonant network 1001 is also a transmitter. Terminals 1007 and 1008 of the network are connected to an inverter. Capacitors 1005 and 1006 have high-voltage, high-frequency voltages across them when the series resonant network 1001 resonates. The sum of these voltages is seen across the inductor 1003. However, since the series resonant network 1001 is in a balanced state, the midpoint of the inductor 1003 between terminals 1002 and 1004 is substantially grounded. Therefore, there is a differential voltage across the inductor 1003, but no high-frequency common-mode voltage to ground. The inductor 1003 does not radiate capacitive EMI and does not require a mechanism to handle EMI.

[0072] Figure 11 shows the parasitic electric field for a resonant induced power system of an electric vehicle 1101 with an unbalanced resonant network leading to EMI radiation in an exemplary embodiment. The electric vehicle 1101 has a small conductance between the chassis 1106 and ground 1108 via the tires 1102. The high-frequency admittance between the chassis 1106 and ground 1108 depends on the capacitance between the chassis 1106 and ground 1108. Common-mode capacitive EMI generated by the transmitter 1104 or receiver 1103 must be minimized because the electric field 1105 generated in the gap 1107 between the chassis 1106 and ground 1108 will excite the capacitance and bring a voltage to the chassis 1106. At the very least, this capacitive coupling can exacerbate the EMI problem and, in the worst case, pose a risk of shock.

[0073] The chassis voltage can be lowered by adding a conductive path to ground, which serves as a means of grounding EMI during charging. Low-resistance conductive vias are used in the tire material. 1109 The existing conductive material (carbon black) of the tire may be reinforced by adding this. Grounding cable or wire Ya Tail 1110 The chassis voltage during charging can also be reduced by the arrangement of these components. Furthermore, the chassis voltage can be reduced by adding circuits that cancel out-of-phase voltages during charging, which are powered by the wireless charging system or the vehicle battery system.

[0074] Those skilled in the art will understand that the embodiments described herein provide various means for shunting a DC waveform in the event of a failure to minimize the possibility of electric shock during charging. This technique can be used in balanced or unbalanced resonant network topologies. The rectifier circuit may include diodes and / or switches in a configuration designed to shunt power in the event of a failure, which leads to improved safety during the charging process, particularly in high-power transmission applications such as charging electric vehicles.

[0075] As described herein, logic, commands, or instructions for implementing aspects of the method herein can be provided on computing systems including any number of form factors of computing systems, such as desktop or notebook personal computers, mobile devices such as tablets, netbooks, and smartphones, as well as client terminals and machine instances hosted on servers. Other embodiments described herein include incorporating the technology described herein into other forms including other forms of programmed logic, hardware configurations, or specific components or modules including devices equipped with respective means for performing the functions of such technology. Each algorithm used to perform the functions of such technology may include some or all sequences of electrical operations described herein, or other forms shown in the accompanying drawings and the following detailed description. Such systems and computer-readable media including instructions for implementing the method herein also constitute exemplary embodiments.

[0076] In one embodiment, the monitoring and control functions described herein can be implemented in software. The software may consist of computer-readable media or computer-readable storage devices, such as one or more non-temporary memories or other types of hardware-based storage devices, whether local or networked. Furthermore, such functions may correspond to modules that may be software, hardware, firmware, or any combination thereof. Multiple functions may be performed by one or more modules as needed, and the embodiments described herein are merely examples. The software may run on digital signal processors, ASICs, microprocessors, or other types of processors operating on computer systems such as personal computers, servers, or other computer systems, and may transform such computer systems into specifically programmed machines.

[0077] Embodiments described herein may include, or operate on, a processor, logic, or several components, modules, or mechanisms (hereinafter referred to as "modules"). A module is a tangible entity (e.g., hardware) capable of performing a specific operation and can be configured or arranged in a specific manner. In one example, a circuit may be arranged in a manner designated as a module (e.g., internally or relative to an external entity such as other circuits). In one example, one or more computer systems, or parts thereof (e.g., standalone, client, or server computer systems) or one or more hardware processors may be configured by firmware or software (e.g., instructions, parts of an application, or an application) as modules that operate to perform a specified operation. In one example, the software may be in a machine-readable medium. When the software is executed by the underlying hardware of the module, it causes the hardware to perform the specified operation.

[0078] Therefore, the term “module” is understood to include tangible hardware and / or software entities that operate in a specified manner or perform some or all of the operations described herein, and that are physically constructed, specifically configured (e.g., hardwired), or configured (e.g., programmed) for a limited period of time (e.g., temporarily). In the case of a temporarily configured module, each module does not need to be instantiated at any given point in time. For example, if a module has a general-purpose hardware processor configured with software, that general-purpose hardware processor may be configured as different modules at different times. Thus, software can configure a hardware processor, for example, to constitute a particular module at one point in time and another module at another.

[0079] Those skilled in the art will understand that the topologies and circuit implementation methodologies described herein enable effective implementation as a single, application-specific integrated circuit. Furthermore, while the disclosures contained herein relate to the supply of power to vehicles, this is only one of many possible applications, and other embodiments, including those for applications other than vehicles, are possible. For example, those skilled in the art will understand that there are many applications that provide current source safety circuits, such as inductive charging applications other than vehicles, e.g., chargers for portable home electronic devices used to charge toothbrushes, mobile phones, and other devices (e.g., Power Mat®). Accordingly, these and other such applications are included in the following claims.

Claims

[Claim 1] A magnetic induction resonant charging circuit, A resonant network having an inductive secondary coil, wherein the inductive secondary coil converts the magnetic field received from the inductive primary coil into an alternating current (AC) signal, and the resonant network is an AC current source, and the resonant network and A rectifier that rectifies the AC signal to generate a direct current (DC) signal for application to a load to be charged, the rectifier having a first pair of normally open switches connected to the first and second leads of the AC current source, and a second pair of normally open switches connected to the first and second leads of the AC current source, the charging circuit further having a normally closed safety switch connected between the first and second pairs of normally open switches, the normally closed safety switch shunts the AC current source in the event of failure or loss of rectification control, the rectifier and A rectifier controller that monitors at least one of the voltage or current in the resonant network to detect the fault or loss of rectification control, and disconnects the resonant network from the charging load when the fault or loss of rectification control is detected, A charging processor, wherein if a failure or loss of rectification control is detected through monitoring by the rectifier controller, the charging processor disables the rectifier controller, and the rectifier controller holds the first and second pairs of normally open switches off and the normally closed safety switch on, and the charging processor and It has, The normally closed safety switch shunts the current flow from the resonant network if the fault or loss of rectification control is detected during active rectification. If there is no control force to operate the rectifier controller or perform synchronous rectification, the normally open switch disconnects the resonant network from the load, and the normally closed safety switch shunts the current flow from the resonant network. charging circuit.

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