Fail-safe Circuit for Wireless Power Transmission

Abstract

To provide a magnetic inductive resonance charging circuit having a mechanism shunting power when a fault occurs, and enhancing safety for electrical shock during a wireless power transmission.SOLUTION: A direct current battery charging circuit using magnetic inductive resonance includes an inductive secondary coil 104, a resonance network 101 converting a magnetic field which the inductive secondary coil received from an inductive primary coil into an alternating current (AC) signal, and a synchronous rectifier stage 102 that rectifies the AC signal to generate a direct current (DC) signal for application to a load. The synchronous rectifier stage shunts an AC waveform of the resonance network that is an AC power source when a fault occurs. An rectifier controller 115 holds a pair of normally open switches 107 and 108 of a rectifier off and a pair of normally closed switches 109 and 110 of the rectifier on to shunt the AC power source when an over-voltage, an over-current fault condition, or an over-temperature fault condition is detected. Capacitive electromagnetic interference produced in an electric vehicle is grounded when the resonance network is unbalanced.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This patent application is a continuation of U.S. Provisional Patent Application No. 63 / 010,771, filed April 16, 2020, and Claim that priority No. 16 / 952,933, filed November 19, 2020 Priority The benefit of which is claimed is to Wolgemuth, John, entitled "Safety Circuit for Wireless Power Transmission," which is incorporated herein by reference in its entirety.

[0002] This disclosure relates to the transfer of electrical energy by resonant induction, and more particularly to system designs, circuit architectures, and safety circuit implementation details that maximize safety in high power wireless power transfer systems. [Background technology]

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

[0004] The transfer of power between coils using magnetic resonance is well known. As described by Faraday's law of induction and Lenz's law, an alternating current in a primary (also called transmitter) coil creates a magnetic field that propagates through an air gap and generates a corresponding opposite current in a secondary (also called 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, into direct current (DC), which flows in only one direction.

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

[0006] As the demand for faster charging increases, the need for higher power charging leads to the use of higher voltages and currents. High current and voltage sources pose increased safety hazards, and safety circuits are desired to reduce the possibility of electric shock. Summary of the Invention [Means for solving the problem]

[0007] Various details regarding embodiments of the present subject matter are provided in the accompanying drawings and the detailed description below.

[0008] The systems and methods described herein enhance safety against electric shock during wireless power transfer by providing a mechanism to shunt power in the event of a fault. In an exemplary embodiment, a magnetic inductive resonant charging circuit is provided. The magnetic inductive resonant charging circuit includes a resonant network having an inductive secondary coil 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 produce a direct current (DC) signal for application to a load to be charged. The synchronous rectifier further includes means for shunting the AC waveform in the event of a fault. In an exemplary configuration, the secondary coil is attached to an electric vehicle and the load is a battery of the electric vehicle.

[0009] In an exemplary embodiment, the resonant network includes first and second balancing capacitors connected in series to each end of the secondary coil, such that the AC signal resonates in series with the first and second capacitors. The synchronous rectifier includes 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 balancing 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 balancing capacitor. The shunting means includes the normally closed switches shunting the secondary coil in the event of the fault. The normally open switches are configured to prevent shorting of the load in the event of the fault. A signal conditioning circuit may be provided to condition the DC signal and output a regulated DC signal for application to the load.

[0010] In an exemplary embodiment, 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 regulated DC waveform applied to the load. A rectifier controller may be configured to monitor the AC signal output by the resonant network in response to values ​​measured by the first and second current and voltage sensors. To phase synchronization and providing a control signal for controlling switching of the pair of normally open switches and the pair of normally closed switches in response to the measured values. A temperature sensor may be provided for detecting an over-temperature fault condition of the synchronous rectifier and providing a detection signal to the rectifier controller.

[0011] In another exemplary embodiment, the charging circuit further includes a charging processor that receives the input AC signal amplitude, the input AC signal frequency, the regulated DC waveform voltage, the regulated DC waveform current, and / or the temperature of the synchronous rectifier from the rectifier controller and commands operation of the rectifier controller, for example, to provide protection from a detected fault condition. The charging processor instructs the rectifier controller to turn the pair of normally open switches and the pair of normally closed switches on and off at approximately zero crossings 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, when a fault condition is detected, the charging processor disables the rectifier controller to hold the pair of normally open switches off and the pair of normally closed switches on. For example, the rectifier controller may hold the pair of normally open switches off and the pair of normally closed switches on when an over-voltage, over-current fault condition is detected by the second current and voltage sensor, or when an over-temperature fault condition is detected by the temperature sensor.

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

[0013] In a further exemplary embodiment, the resonant network may include an alternating current (AC) current source, and the synchronous rectifier may include a first pair of diodes connected to first and second leads, respectively, of the AC current source, and a second pair of diodes connected to the first and second leads, respectively, of the AC current source. and The second pair of diodes Between , the normally closed safety switch being configured to shunt the AC current source in the event of the fault.

[0014] In a further exemplary embodiment, the resonant network may include an alternating current (AC) current source, and the synchronous rectifier may include a first pair of normally open switches connected to first and second leads, respectively, of the AC current source, and a second pair of normally open switches connected to the first and second leads, respectively, of the AC current source. Yo The shunting means is and Second pair of normally open switches Chi , the normally closed safety switch being configured to shunt the AC current source in the event of the fault.

[0015] In an exemplary embodiment, the resonant network can be balanced or unbalanced. A variety of 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, the 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, the secondary coil, and a second resonant capacitor in series with the secondary coil.

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

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

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

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

[0022] The resonant network may be a balanced SSRN having an inductive primary coil, a first resonant capacitor in series with the primary coil at a first end of the primary coil, a second resonant capacitor in series with the primary coil at a second end of the primary coil, the secondary coil, a third resonant capacitor in series with the secondary coil at the first end of the secondary coil, and a fourth resonant 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, the rectangular coil winding being disposed on at least one side of an insulating substrate. The resonant capacitor may be connected in series with 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 with respect to ground that is half the voltage of the resonant capacitor, which may cause the rectangular coil winding to be a capacitive electromagnetic interference radiator.

[0024] In another exemplary embodiment, a first resonant capacitor may be connected in series with a first end of the rectangular coil winding and a second resonant capacitor may be connected in series with a second end of the rectangular coil winding, such that the midpoint between the first and second ends of the rectangular coil winding is substantially at ground, thereby causing the rectangular coil winding to not radiate capacitive electromagnetic interference.

[0025] In further exemplary embodiments, techniques are provided for mitigating 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 includes a ground cable that grounds the EMI during charging. According to a third technique, the electric vehicle includes a circuit powered by the electric vehicle battery that cancels out-of-phase voltages during charging.

[0026] According to another aspect, a magnetic induction resonant charging circuit is provided for charging a battery of an electric vehicle, the charging circuit including a resonant network having an inductive secondary coil in an electric vehicle, the resonant network 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 rectifying the AC signal to generate a direct current (DC) signal for application to the battery of the electric vehicle, and a means for grounding the EMI during charging. In an exemplary embodiment, the means for grounding the EMI during charging may include a tire of the electric vehicle, the tire including a conductive via for grounding the EMI during charging. Alternatively, the means for grounding the EMI during charging may include a ground cable connected to the electric vehicle to ground the EMI during charging. In another embodiment, the means for grounding the EMI during charging may include a circuit powered by the battery of the electric vehicle for canceling out-of-phase voltages during charging.

[0027] This Summary section is provided to introduce aspects of the inventive subject matter in a simplified form and is a further description of the inventive subject matter that follows the body of the Detailed Description. This Summary section is not intended to identify essential or required features of the claimed subject matter, nor is the particular combination and order of elements recited in this Summary section intended to limit the elements of the claimed subject matter. Rather, it will be understood that the following provides summarized illustrations of some of the embodiments described in the Detailed Description that follow. [Brief description of the drawings]

[0028] The foregoing and other beneficial features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings. [Figure 1] FIG. 1 illustrates a high-level circuit embodiment of a safety enhanced magnetic resonant inductive system. [Diagram 2]FIG. 2 shows a schematic diagram of a typical safety circuit of a voltage source with a load. [Diagram 3] FIG. 3 shows a schematic diagram of a typical safety circuit of a current source with a load. [Figure 4A] FIG. 4A illustrates a schematic of switch-based synchronous rectification of an AC voltage source with a complex load impedance. [Figure 4B] FIG. 4B illustrates a schematic of switch-based synchronous rectification of an alternating current source with a complex load impedance. [Figure 4C] FIG. 4C illustrates a schematic of switch-based synchronous rectification of an AC voltage source with a load. [Figure 4D] FIG. 4D illustrates a schematic of switch-based synchronous rectification of an alternating current source with a load. [Figure 5A] FIG. 5A illustrates a schematic diagram of passive rectification of an AC voltage source with a load. [Figure 5B] FIG. 5B illustrates a schematic diagram of passive rectification of an alternating current source with a load. [Figure 5C] FIG. 5C illustrates a schematic representation of an alternative embodiment of passive rectification of an alternating current source with a load. [Figure 6] FIG. 6 illustrates generally an alternative embodiment of a switch-based synchronous rectification of an alternating current source with a load. [Figure 7A] FIG. 7A shows a schematic of a parallel-parallel resonant inductive circuit. [Figure 7B] FIG. 7B illustrates a schematic of an unbalanced series-series resonant inductive circuit. [Figure 7C] FIG. 7C shows a schematic of a hybrid parallel-unbalanced series resonant inductive circuit. [Figure 7D] FIG. 7D shows a schematic of a hybrid unbalanced series-parallel resonant inductive circuit. [Figure 7E] FIG. 7E shows a schematic of a hybrid parallel-balanced series resonant inductive circuit. [Figure 7F] FIG. 7F shows a schematic of a hybrid balanced series-parallel resonant inductive circuit. [Figure 7G] FIG. 7G illustrates a schematic of a balanced series-series resonant inductive circuit. [Figure 8] FIG. 8 shows the geometry of a coil for use in a magnetic resonant inductive power system. [Figure 9] FIG. 9 shows a schematic of an unbalanced circuit corresponding to a planar coil for use in a resonant inductive power system. [Figure 10] FIG. 10 shows a schematic of a balanced circuit equivalent to a planar coil for use in a resonant inductive power system. [Figure 11] FIG. 11 shows the parasitic electric fields for an electric vehicle resonant inductive power system with an unbalanced resonant network. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Exemplary embodiments of the present invention are described with reference to the figures. The current source safety circuits and related methods described herein may be more readily understood by reference to the following detailed description provided in conjunction with the accompanying drawings and examples that form a part of this disclosure. It will be understood that this description is not limited to the specific products, methods, conditions, or parameters described and / or shown herein, and that the terminology used herein is intended to describe specific embodiments by way of example only, and is not intended to limit the claimed subject matter. Similarly, any explanations of possible mechanisms or modes of action or reasons for improvements are for illustrative purposes only, and the subject matter described herein should not be limited by the correctness or inaccuracy of such proposed mechanisms or modes of action or reasons for improvements. It will be understood that throughout this text, the description refers to both methods and systems / software for implementing such methods.

[0030] A detailed description of exemplary embodiments will now be provided with reference to Figures 1 to 11. While this description provides detailed examples of possible embodiments, it should be noted that these details are intended as examples and in no way limit the scope of the inventive subject matter.

[0031] In a wireless power transfer system using an open-air transformer, 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 almost reverses the voltage source specific provisions of domestic and industrial scenarios for power supply. The main difference with these scenarios is that in a voltage source, short circuits are bad. As a result, power conversion topologies are built with normally-off devices to avoid short circuits. However, for a current source, the opposite is true: an open circuit is bad. This means that typical rectification techniques are undesirable. A straight passive (e.g., diode-based) rectifier offers no protection. A traditional synchronous rectifier can offer protection, but only if there is a reliable means of powering the device to turn it on.

[0032] FIG. 1 shows a schematic high-level schematic diagram of a DC battery charging circuit using magnetic induction resonance. Resonant network 101 (also called receiver or secondary) has an inductive secondary coil 104 and balancing capacitances 105 and 106. Secondary coil 104 converts a magnetic field from a charging transmitter (not shown) into an alternating current (AC) signal that resonates in series with balancing capacitances 105 and 106 in the voltage domain. As described below with respect to FIGS. 7A-7G, the primary side of the resonant network can be balanced or unbalanced. The AC signal from resonant network 101 is then rectified into a direct current (DC) signal in rectification stage 102. Rectification 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 pair of NC switches 109 and 110 are used to provide a synchronous rectification circuit in the event of a fault. Resonant Networks 101 The DC signal is passed to a conditioning circuit 111 which outputs a regulated DC signal that is used to charge a battery 112.

[0033] The rectifier controller 115 senses the resonant network current at the first current and voltage sensor 113 as a reference (e.g., with respect to detected zero crossings) for controlling the timing of the rectifier switches 107-110. To phase synchronization The rectifier controller 115 (nominally a 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 a first current and voltage sensor 113, as long as 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 a second current and voltage sensor 114.

[0034] The vehicle charging processor 116 (typically implemented as software running on a microprocessor) can handle communication with internal subsystems (such as a wireless power transfer (WPT) system) and external vehicle systems via an interface (e.g., a controller area network (CAN) bus) and can command 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 device. 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) is above a threshold (e.g., 5 amps), and no faults are detected, the vehicle charging processor 116 can instruct the rectifier controller 115 to turn on and off the upper pair of NO switches 107 and 108 and the lower pair of NC switches 109 and 110 at the appropriate zero crossings of the input AC waveform to maximize the efficiency of rectification. The nominal state is "start" or "safe", in which 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 producing a positive signal, switches 107 and 108The first set of switches is opened. 109 and the second set of switches 107 and 110 are closed. When the signal from the secondary coil 104 reverses, the switches 107 and 108 The first set of switches is closed. 109 and a second set of 110 are opened. This sequence is repeated to produce an output signal that is mathematically the absolute value of the input AC signal.

[0035] When disabled by the vehicle charging processor 116, the rectifier controller 115 holds the upper pair of NO switches 107 and 108 off and the lower pair of NC switches 109 and 110 on. Also, if an over-voltage, over-current fault condition is detected by the current and voltage sensor 114, or an over-temperature fault condition is detected by the temperature sensor 117, the rectifier controller 115 holds the upper pair of NO switches 107 and 108 off and the lower pair of NC switches 109 and 110 on to Resonant Networks 101 Shunts current from

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

[0037] When combined with a series-series resonant transmitter (not shown), the resonant network 101 is an AC current source. Any condition that would cause the resonant network 101 to be open circuited would result in a dangerous condition. However, the selection of the NO switches 107 and 108 and the NC switches 109 and 110 of the synchronous rectifier stage 102 results in an intrinsically safe system. Under normal conditions, the NC switches 109 and 110 can be closed 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. The NO switches 107 and 108 prevent shorting the output network 103, and in particular the battery 112.

[0038] In the event of a fault, battery 112 is disconnected from signal conditioning circuit 111, the current into conditioning circuit 111 remains unchanged, but the current out of conditioning circuit 111 decreases to zero. This causes the voltage across conditioning circuit 111 and rectification stage 102 to increase at a rate proportional to the rectified current and the impedance of conditioning circuit 111.

[0039] The rectifier controller 115 monitors the voltage and / or current using the current and voltage sensors 114 to detect disconnection of the battery 112. In the event of a fault, the rectifier controller 115 can respond by opening the NO switches 107 and 108 and closing the NC switches 109 and 110. This acts to disconnect the resonant network 101 from the regulating circuit 111 and the battery 112. When the flow of rectified current from the rectification stage 102 to the regulating circuit 101 and the battery 112 is interrupted by the NO switches 107 and 108 and the current flow from the resonant network 101 is shunted to the NC switches 109 and 110, power transfer will immediately cease.

[0040] Control to manipulate controllers and synchronously commutate electricIn the passive state with no power, NO switches 107 and 108 open output network 103 and NC switches 109 and 110 shunt resonant network 101. This protects the charger, the load and service personnel from spurious energy picked up by resonant network 101, whether the spurious energy is accidental or deliberate.

[0041] Figure 2 shows ,negative A typical safety circuit of a voltage source with a load is shown diagrammatically in FIG. 2. A typical voltage source supply protection solution is shown in which the voltage source 201 and the load 202 share a common ground 203. The voltage source 201 provides a fixed voltage that does not change with respect to the source current. The source current is set by the load impedance of the load 202. The current sensor 205 monitors the source current. If the source current exceeds an acceptable limit, the current sensor 205 provides a protection function by triggering the normally open switch 204 to an open state. The normally open switch 204 remains open until it is reset. When the normally open switch 204 is triggered to disconnect, the voltage and current across the load 202 are forced to zero. The normally open (NO) switch 204 and current sensor 205 shown herein are just one implementation option with a variety of relays, circuit breakers, and fuses being widely used. As shown in FIG. 2, virtually all power sources and power distribution networks operate from a voltage source and implement some type of current limiting scheme using some form of breaker or fuse. It will be appreciated that in a voltage source power system, an open circuit is good and a short circuit is bad.

[0042] The current source supply embodiment shown in FIG. 3 is not very common. In a constant current power supply, the best measures of safety protection in the more common voltage source power supply should be faithfully manifested. It will be understood that in a current source power system, unlike a voltage source power system, an open circuit is not good and a shunt (intentional short circuit) is a good implementation. Therefore, the different embodiments of the safety circuit 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 shows ,negative 3 shows a schematic of a typical safety circuit for a current source with a load. The current source 301 is independent of the voltage across it. Negative It supplies a current to a load 302. In this example, all circuit paths share a common ground 303. Current source 301 provides a fixed current that is invariant to the voltage and current.

[0044] Potential-sensitive disconnectors to provide current shunting and isolation of load from source (and vice versa) is negative 3 is simply one implementation option of a commonly used shunt means involving a variety of switches, relays, circuit breakers, and fuses. When the NC switch shunt 304 is triggered by the voltage sensor 305, the NC switch shunt 304 Closed Be ,negative The voltage and current flow through the load 302 are driven to zero.

[0045] 4A-4D all show alternative embodiments of the safety rectification circuitry and additional subsystems required for wireless power transfer.

[0046] FIG. 4A shows a schematic diagram of switch-based synchronous rectification of an AC voltage source with a complex load impedance. Specifically, FIG. 4A shows a conventional AC voltage source and a safety-enhanced synchronous rectification circuit to form a direct current (DC) voltage source. An AC voltage source 401 is synchronously rectified by a set of normally open (NO) switches 402, 403, 404, and 405. A power conditioning network 406 filters the rectified DC voltage into a DC voltage source for a load 407. In the event of a fault, the NO switches open as a fault and disconnect and protect the load 407 from the AC voltage source 401.

[0047] FIG. 4B illustrates a schematic of switch-based synchronous rectification of an AC current source with a complex load impedance in an exemplary embodiment. Specifically, FIG. 4B illustrates an AC current source and a safety-enhanced synchronous rectification circuit to form a DC current source. The AC current source 410 includes a NO switch. 402 and 403 and a set of normally closed (NC) switches 408 and 409. A power conditioning network 406 filters the rectified current into a DC current source for a load 407. An AC current source 410 controls the set of NC switches 408 and 409 to provide a means to shunt the current in the event of a fault. close In a fault condition, Open switch 402 and 403 isolates the load 407 from the AC current source 410 to prevent backfeeding of power.

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

[0049] FIG. 4D shows an example embodiment of the NegativeFIG. 4D shows a schematic of switch-based synchronous rectification of an AC source with a load. Specifically, FIG. 4D shows an AC current source and a safety-enhanced synchronous rectification circuit to form a DC voltage source for battery charging. An AC current source 410 is synchronously rectified by a set of NO switches 402 and 403 and NC switches 408 and 409. A power conditioning network 406 filters the rectified current into a DC current source for a battery 412. The AC current source 410 requires a set of NC switches 408 and 409 to provide a means to shunt the current in case of a fault. However, the power conversion stage 411 of FIG. 4C is not required for battery charging since the system is powered from the current source.

[0050] Figure 5A is ,negative 5A illustrates a schematic of a passive rectification of an AC voltage source with a load. Specifically, FIG. 5A illustrates a schematic of a conventional passive full-wave rectifier circuit for an AC voltage source 501. Diodes 502, 503, 504, and 505 act as unidirectional gates to generate a full-wave rectification of the AC signal. Power conditioning stage 506 serves to smooth the rectifier voltage output applied to load 507, allowing charging of load 507.

[0051] As with all diode circuits, the reverse recovery time and voltage drop under forward bias conditions affect the efficiency of the rectifier circuit. A passive rectifier circuit does not require a controller stage. However, in the event of a fault, the AC voltage source 501 remains connected to the load 507 through the power conditioning stage 506, exposing the load 507 to the voltage source fault (and vice versa).

[0052] FIG. 5B shows an example embodiment. Negative5A and 5B show schematic diagrams of passive rectification of an AC current source with a load. Specifically, FIG. 5B shows a hybrid embodiment of a safety-enhanced circuit for rectification of an AC current source 508. Full-bridge passive rectifier diodes 502, 503, 510, and 512 are supplemented by normally closed (NC) switches 509 and 511. Diodes 502, 503, 510, and 512 act as unidirectional gates to generate full-wave rectification. NC switches 509 and 511 act as a means to shunt in case of a fault, preventing overvoltage damage between AC current source 508 and diodes 502, 503, 510, and 512. Power conditioning stage 506 helps smooth the rectifier voltage output applied to load 507, allowing charging of load 507.

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

[0054] FIG. 5C shows an example embodiment of the Negative 5C shows an alternative semi-passive embodiment of a safety-enhanced full-wave rectifier circuit for an AC current source 508. Diodes 502, 503, 510, and 512 act as unidirectional gates to generate full-wave rectification. A power conditioning stage 506 helps smooth the rectifier voltage output applied to a load 507, allowing the load 507 to be charged. In this embodiment, a normally closed (NC) shunt switch 513 is placed in the circuit. In the event of a fault or command option, the shunt switch 513 shunts the current in the rectifier circuit, preventing damage to the power conditioning stage 506 and the load 507.

[0055] This embodiment is a cheaper implementation with simpler control, but the efficiency is lower. Furthermore, it produces 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 under forward bias conditions affect the efficiency of the rectifier circuit.

[0056] FIG. 6 illustrates, in schematic form, an alternative switch-based synchronous rectification of an AC current source with a load in an exemplary embodiment. Specifically, FIG. 6 illustrates an alternative safety circuit for active rectification of an AC current source 601. A power conditioning stage 606 serves to smooth the rectifier voltage output for application to a load 607 to be charged. Full-wave rectification is achieved by alternating at the zero crossings of the sinusoidal output of the AC current source 601. A normally closed (NC) safety switch 608 is connected to the upper normally open (NO) rectifier switches 602 and 604. and Lower normally open (NO) rectifier switches 603 and 60 5 hours to provide a means to shunt current in the rectifier circuit in the event of a fault or command option, preventing damage to the power conditioning stage 606 and load 607.

[0057] In the event of a fault condition or loss of commutation control If, NO rectifier switches 602, 603, 604, and 605 are open Broken down at (or In the open position commanded), while the NC safety switch 608 is in the closed state. Breaks down at Thus, while the load is isolated by switches 602-605, the current is shunted back to the AC current source 601 by the NC safety switch 608. This embodiment reduces the demand for normally closed (NC) switches by using the additional switch 608.

[0058] In resonant inductive wireless charging, there are four possible two-pole networks: Parallel-Parallel Resonant Network (PPRN) and Series-Series Resonant Network (SSRN). With galvanic isolation, it is also possible to form Parallel-Series Resonant Network (PSRN) and Series-Parallel Resonant Network (SPRN). PPRN, PSRN, and SPRN all behave as AC Voltage Controlled Voltage Sources (VCVS) when the load impedance is large compared to the network impedance, and as AC Voltage Controlled Current Sources (VCCS) when the load impedance is small compared to the network impedance. On the other hand, SSRN behaves as a VCCS for all load impedances. A constant voltage load, e.g. a battery, behaves as a variable load impedance when the power level changes. At low power, the battery behaves as a high impedance load, and at high power, it behaves as a low impedance load. At high power, all four resonant networks will behave as a VCCS.

[0059] When operating as a VCCS, the transconductance (G) of the PPRN is k / (w*L) in Amperes / Volt, where k is the magnetic coupling coefficient of the primary and secondary inductors in the range 0 to 1 and is unitless. w is the resonant frequency of the network in radians / second, and L is the geometric mean of the primary and secondary inductors in Henrys. When operating as a VCCS, the G of the PSRN, SPRN, and SSRN is 1 / (w*L*k). This means that for a fixed G, the PPRN inductors have a transconductance of k 2 The capacitor PPRN is smaller by k -2 This is undesirable because the capacitor is a much more expensive component.

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

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

[0062] 7A shows a schematic of a balanced PPRN circuit in an exemplary embodiment. The 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] 7B shows a schematic of an unbalanced SSRN circuit in an exemplary embodiment. The 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] 7C illustrates a schematic of an unbalanced PSRN circuit in an exemplary embodiment. The 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] 7D illustrates a schematic of an unbalanced SPRN circuit in an exemplary embodiment. The 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] 7E shows a schematic of a balanced PSRN circuit in an exemplary embodiment. The 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] 7F shows a schematic of a balanced SPRN circuit in an exemplary embodiment. The 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] 7G shows a schematic of a balanced SSRN circuit in an exemplary embodiment. The 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] FIG. 8 illustrates a geometric representation of a planar coil 801 for use as a primary coil in a magnetically resonant inductive power system in an exemplary embodiment. Although shown as a rectangular coil, other shapes (e.g., a classical round coil or rectangular) are possible. The coil windings 803 are disposed on an insulating substrate 805 and may include individual conductive ribbons (e.g., a printed circuit board), insulated wire strands (e.g., Litz wire), etc. Vias 802 and 804 allow connection to other coils on the other side of the insulating substrate 805.

[0070] FIG. 9 shows a schematic of an unbalanced circuit equivalent to the planar coil 801 used in a 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. This same voltage is seen across the inductor 903. The first terminal 904 of the inductor 903 is effectively held at ground potential. The second terminal 902 of the inductor is exposed to the full voltage of the resonant capacitor 905 with respect to ground. That is, the voltage of the inductor 903 has a common mode voltage with respect to ground that is half the voltage across the resonant capacitor 905, which makes the inductor 903 a capacitive electromagnetic interference (EMI) radiator. In this configuration, techniques to mitigate EMI radiation are desirable, as shown below with respect to FIG. 11.

[0071] FIG. 10 shows a schematic of 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 said 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 those 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. Thus, 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] FIG. 11 illustrates the parasitic electric field for a resonant inductive power system of an electric vehicle 1101 with an unbalanced resonant network that leads to EMI radiation in an exemplary embodiment. The electric vehicle 1101 has a small conductance between the chassis 1106 and ground 1108 through the tires 1102. The admittance at high frequencies between the chassis 1106 and ground 1108 is dominated by 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 excites the capacitance and induces a voltage on the chassis 1106. At the very least, this capacitive coupling can increase the EMI problem and at worst can pose a shock hazard.

[0073] By adding a conductive path to ground, the chassis voltage can be lowered, which acts as a means to ground EMI while charging. Low resistance conductive vias in the tire material 1109 The electrically conductive material in the tire (carbon black) may be reinforced by adding a ground cable or wire. Ya: Tail" 1110 Chassis voltage can also be mitigated during charging by adding circuitry powered by the wireless charging system or the vehicle battery system that cancels out-of-phase voltages during charging.

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

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

[0076] In one embodiment, the monitoring and control functions described herein may be implemented in software. The software may consist of computer-executable instructions stored in one or more non-transitory memories or other types of hardware-based storage devices, such as local or networked. Moreover, such functions correspond to modules, which may be software, hardware, firmware, or any combination thereof. Where appropriate, multiple functions may be performed in one or more modules, and the described embodiments are merely exemplary. The software may be executed on a digital signal processor, ASIC, microprocessor, or other type of processor operating on a computer system, such as a personal computer, server, or other computer system, and may turn such a computer system into a specifically programmed machine.

[0077] An embodiment as described herein may include or operate on a processor, logic, or a number of components, modules, or mechanisms (herein "modules"). A module is a tangible entity (e.g., hardware) capable of performing a particular operation and may be configured or arranged in a particular manner. In one example, a circuit may be arranged (e.g., internally or with respect to an external entity, such as other circuits) in a manner designated as a module. In one example, all or a portion of one or more computer systems (e.g., standalone, client or server computer systems) or one or more hardware processors may be configured by firmware or software (e.g., instructions, portions of an application, or applications) as modules that operate to perform specified operations. In one example, the software may reside on a machine-readable medium. The software, when executed by the underlying hardware of the module, causes the hardware to perform the specified operations.

[0078] Thus, the term "module" is understood to include a tangible hardware and / or software entity that is physically constructed and specifically configured (e.g., hardwired) or configured (e.g., programmed) for a limited period of time (e.g., temporarily) to operate in a specified manner or to perform some or all of the operations described herein. Considering examples where modules are temporarily configured, each module need not be instantiated at any one time. For example, if the modules have a general-purpose hardware processor configured with software, the general-purpose hardware processor may be configured as different respective modules at different times. Thus, the software may configure the hardware processor, for example, to configure certain modules at some times and other modules at other times.

[0079] Those skilled in the art will appreciate that the topology and circuit implementation methodology described herein allows for effective realization as a single application specific integrated circuit. Additionally, while the disclosure contained herein is directed to providing power to a vehicle, it should be understood that this is only one of many possible applications and that other embodiments are possible, including non-vehicle applications. For example, those skilled in the art will appreciate that there are many applications for providing a current source safety circuit, such as inductive charging applications other than vehicles, for example, chargers for portable consumer electronics such as those used to charge toothbrushes, cell phones, and other devices (e.g., Powermat®). Accordingly, these and other such applications are intended to be within the scope of the following claims.

Claims

1. A magnetic induction resonant charging circuit, comprising: a resonant network having an alternating current source including an inductive secondary coil, the inductive secondary coil converting a magnetic field received from the inductive primary coil into an alternating current (AC) signal; a first pair of diodes connected to first and second leads, respectively, of the AC current source, and a second pair of diodes connected to the first and second leads, respectively, of the AC current source, the first and second pairs of diodes rectifying the AC signal to produce a direct current (DC) signal for application to a load to be charged; means for shunting an AC signal current from said AC current source when a fault or loss of rectification control is detected during rectification by said first and second pairs of diodes; having the shunting means comprising a first normally closed switch connected in parallel with a first diode of the second pair of diodes and a second normally closed switch connected in parallel with a second diode of the second pair of diodes, the first and second normally closed switches shunting the AC current source in the event of the failure or loss of rectification control. charging circuit.

2. 2. The charging circuit of claim 1, wherein the shunting means comprises a normally closed safety switch connected across the first and second pairs of diodes, the normally closed safety switch shunting the AC current source in the event of the failure or loss of rectification control.

3. 2. The charging circuit of claim 1, wherein when no power is applied to the first and second pairs of diodes, the resonant network is disconnected from the load and current flow from the resonant network is shunted.

4. 2. The charging circuit of claim 1, wherein the resonant network further comprises first and second balancing capacitors connected in series to each end of the secondary coil, whereby the AC signal resonates in series with the first and second capacitors.

5. 2. The charging circuit of claim 1, wherein the resonant network includes an inductive primary coil, a first resonant capacitor in parallel with the primary coil, the secondary coil, a second resonant capacitor in series with the secondary coil at a first end of the secondary coil, and a third resonant capacitor in series with the secondary coil at a second end of the secondary coil.

6. 2. The charging circuit of claim 1, wherein the resonant network includes an inductive primary coil, a first resonant capacitor in series with the primary coil at a first end of the primary coil, a second resonant capacitor in series with the primary coil at a second end of the primary coil, the secondary coil, a third resonant capacitor in series with the secondary coil at the first end of the secondary coil, and a fourth resonant capacitor in series with the secondary coil at the second end of the secondary coil.

7. 2. The charging circuit of claim 1, further comprising a signal conditioning circuit for conditioning the DC signal into a regulated DC signal for application to the load.

8. 2. The charging circuit of claim 1, wherein the resonant network comprises an inductive primary coil, a first resonant capacitor in parallel with the primary coil, the secondary coil, and a second resonant capacitor in parallel with the secondary coil.

9. 2. The charging circuit of claim 1, wherein the resonant network comprises an inductive primary coil, a first resonant capacitor in series with the primary coil, the secondary coil, and a second resonant capacitor in series with the secondary coil.

10. 2. The charging circuit of claim 1, wherein the resonant network comprises an inductive primary coil, a first resonant capacitor in parallel with the primary coil, the secondary coil, and a second resonant capacitor in series with the secondary coil.

11. 2. The charging circuit of claim 1, wherein the resonant network comprises an inductive primary coil, a first resonant capacitor in series with the primary coil, the secondary coil, and a second resonant capacitor in parallel with the secondary coil.

12. 2. The charging circuit of claim 1, wherein the resonant network includes an inductive primary coil, a first resonant capacitor in series with the primary coil at a first end of the primary coil, a second resonant capacitor in series with the primary coil at a second end of the primary coil, the secondary coil, and a third resonant capacitor in parallel with the secondary coil.

13. 10. The charging circuit of claim 1, wherein the resonant network further comprises an inductive primary coil having a coil winding, the coil winding disposed on at least one side of an insulating substrate.

14. 14. The charging circuit of claim 13, further comprising a resonant capacitor connected in series with a first end of the coil winding, the second end of the coil winding being connected to ground or driven by an inverter, the coil winding having a common mode voltage with respect to ground that is half the voltage of the resonant capacitor, thereby making the coil winding a capacitive electromagnetic interference radiator.

15. 14. The charging circuit of claim 13, further comprising a first resonant capacitor connected in series with a first end of the coil winding and a second resonant capacitor connected in series with a second end of the coil winding, wherein a midpoint between the first end and the second end of the coil winding is substantially at ground, whereby the coil winding does not radiate capacitive electromagnetic interference.

16. 2. The charging circuit of claim 1, wherein the secondary coil is attached to an electric vehicle and the load is a battery of the electric vehicle.

17. 17. The charging circuit of claim 16, wherein the resonant network is unbalanced, thereby radiating capacitive electromagnetic interference (EMI), and the electric vehicle has tires with conductive vias that ground the EMI during charging.

18. 17. The charging circuit of claim 16, wherein the resonant network is unbalanced, thereby radiating capacitive electromagnetic interference (EMI), and the electric vehicle has a ground cable that grounds the EMI during charging.

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