Wireless power transfer device

Abstract

A wireless power transfer device is disclosed. In the wireless power transfer device (1), power is wirelessly transferred from the primary side (2) to the secondary side (3) across an air gap (8) by means of a primary resonator (6) that generates a magnetic field (9) and a secondary resonator (10) that receives power by picking up the magnetic field (9). The secondary side (3) includes an output stage (11) that receives AC power provided by the secondary resonator (10) and generates a DC output (13) to be provided to a load. A current sensing device (18) senses the AC current flowing from the secondary resonator (10) to the output stage (11) and provides a current sensing signal (16) to a power transfer controller (15), which controls the power transfer of the wireless power transfer device (1) based on the current sensing signal (16). Furthermore, the current sensing signal (16) is provided to the switch controller (20), which controls the switching of the synchronous rectifier of the output stage (11), which converts the AC power (12) provided by the secondary resonator (10) into DC output (13).

Description

Technical Field

[0001] This invention relates to a wireless power transfer device for wireless power transfer from a primary side across an air gap to a secondary side via inductive coupling. The primary side includes a power input for receiving input power, an input stage for converting the input power into primary AC power, and a primary resonator for receiving the primary AC power and sensing a magnetic field. The secondary side includes a secondary resonator for converting power received via the magnetic field into secondary AC power and an output stage for converting the secondary AC power into DC output power. The output stage includes a controllable rectifier for converting the secondary AC power into DC output power. The wireless power transfer device includes a current sensing device adapted to generate a current sensing signal, a power transfer controller adapted to control the wireless power transfer based on the current sensing signal, and a control device for controlling the controllable rectifier. The invention further relates to a secondary side for such a wireless power transfer device, a current sensing device for such a wireless power transfer device, and a corresponding method for wireless power transfer. Background Technology

[0002] Electrical energy is used in many different applications. To power electrically driven devices, articles, or objects that are not permanently connected to a power source, such devices, articles, or objects are often equipped with one or more batteries that store energy for use when they are not connected to a power source. Examples include mobile devices such as cell phones and PDAs (personal digital assistants); motor vehicles such as cars, trucks, motorcycles, trains, ships, cargo ships, airplanes, and helicopters; industrial vehicles such as forklifts, AGVs (automated guided vehicles), cleaning machines, and elevators; or electrical work equipment used to lift, move, or transport any kind of goods. All these devices, articles, or objects typically include batteries to enable them to operate.

[0003] While the primary side is most often fixed in place and connected to a power source, the secondary side is usually located inside the mobile device, as mentioned above, which is only occasionally placed near the primary side to charge its battery or otherwise supply power to it.

[0004] While lead-acid batteries have long been used to store electricity to power devices, items, or objects, lithium-ion batteries are now more commonly used for this purpose. One reason is that they can be charged at a much higher charge rate (c-rate). Lead-acid batteries can be charged at a rate of approximately 0.1c to 0.2c. This means a 600 Ah lead-acid battery can be charged with a current of approximately 60 to 120 amps and will take approximately 5 to 10 hours. Lithium-ion batteries can be charged at a rate up to 1c, so a 600 Ah lithium-ion battery can be charged with a current up to 600 amps, reducing the charging time to as low as approximately 1 hour. Furthermore, lithium-ion batteries can be charged occasionally without damaging the battery, whereas in the case of lead-acid batteries, this damage occurs when multiple short charge cycles are applied within just a few minutes.

[0005] However, the high charging current in the case of lithium-ion batteries can cause problems for wired chargers, where the charging current is fed from the power source to the battery via a cable—which is connected to the source and / or battery through connectors. High charging currents require charging cables with large copper diameters and heavy-duty connectors. Consequently, the charging cables become difficult to handle and the connectors wear out quickly. With infrequent charging, such connectors will wear out within weeks.

[0006] To overcome the problems associated with charging cables, charging such batteries is typically accomplished via wireless power transfer. When power is transferred wirelessly through inductive coupling, such a wireless power transfer system is called an inductive power transfer (IPT) system. Some IPT systems also work with loosely coupled inductors.

[0007] The primary side of such a wireless power transfer system includes an input stage and primary pads, wherein the input stage is connected to a power source and typically converts the input power into AC input power suitable for use as input to the primary pads, inducing a more or less directional magnetic field. The secondary side of such a wireless power transfer system includes secondary pads and an output stage, wherein the secondary pads are located within the magnetic field generated by the primary stage, and the output stage includes a rectifier that converts the AC power received from the secondary pads into DC current for charging a battery or powering other types of loads.

[0008] To control power transmission, it is known to control the input stage so that the power transmitted across the air gap and converted to DC power by the output stage meets specific criteria. Typically, the load current should meet a set value specified by the load, such as the load current specified by the battery management system of the battery to be charged. Therefore, the controller typically generates control signals for the input stage based on measurements of the load current. The current can be sensed, for example, using a shunt resistor or current transducer at the output of the wireless power transmission system.

[0009] To reduce losses in the secondary rectifier, synchronous rectifiers (SRs) are typically used. The control signal for the synchronous rectifier is typically derived by sensing the voltage across the synchronous switch. In the case of a MOSFET as the synchronous switch, the switch is turned on if the measured drain-source voltage is below a few millivolts (mV), and turned off once the drain-source voltage approaches zero volts (V). Control circuitry implemented as an integrated circuit (IC) is commonly used for such SR control.

[0010] However, in high magnetic AC field environments, such as in wireless power transmission systems used to charge batteries in electric vehicles, detecting a few mV is quite difficult. Therefore, detection errors can occur, leading to unstable switching.

[0011] Document US 8'947'041 B2 discloses a control method for wirelessly exchanging power from one wirelessly rechargeable device (primary side) to another wirelessly rechargeable device (secondary side). The power transceiver includes a transmitter (308T) and a receiver (308R). The transmitter (308T) has a power conversion circuit and a transmitting antenna (306T) for sensing a magnetic field. The receiver (308R) has a receiving antenna (306R) for receiving energy transmitted through the magnetic field and an output power conversion circuit for providing DC power to a load (battery 310R or host device electronics). The output power conversion circuit further includes a synchronous rectifier (Q2, Q2'), a frequency generator, and a control unit (322R) for controlling the synchronous rectifier (Q2, Q2') and for controlling the operating mode (i.e., transmitting mode or receiving mode). If the bidirectional output power conversion circuit is operating in receive mode, the synchronous rectifier (Q2, Q2') is controlled based on the voltage sensed on the rectifier switch (column 9, line 26).

[0012] One of the problems with this type of connection is the measurement of the load current. The load current is a DC current, and DC current may not be measured passively or only at high costs (such as by using an active transducer), thus increasing the cost. Another possibility for measuring high DC current is to use a suitable shunt; however, this increases losses. Summary of the Invention

[0013] The object of this invention is to create a wireless power transmission device relating to the initially mentioned technical field, which enables enhanced SR control, resulting in fewer switching errors and reduced losses. A further object of this invention is to create a secondary side for such a wireless power transmission device, a current sensing device for such a wireless power transmission device, and a method for wireless power transmission, relating to the initially mentioned technical field.

[0014] The solution of the present invention regarding a wireless power transmission device is specified by the features of the technical solution of the present invention. According to the present invention, the current sensing device includes a current sensing apparatus adapted to generate a current sensing signal by sensing AC current flowing from the secondary resonator to the output stage, and wherein a control device is adapted to control a controllable rectifier based on the current sensing signal.

[0015] That is, the control device generates control signals for controlling the controllable rectifier, such as control signals for turning the synchronous rectifier on and off. The control device generates these control signals taking into account a current sensing signal corresponding to the sensed AC current. The current sensing signal is, for example, a copy of the sensed AC current at different scales.

[0016] Depending on the design of the current sensing device, its output can be either current or voltage. Therefore, the current sensing signal can generally be either current or voltage. It should be further noted that if the current sensing device outputs current, it can be easily converted into voltage as the current sensing signal. Alternatively, if the current sensing device outputs voltage, it can be easily converted into current as the current sensing signal.

[0017] Furthermore, it should be noted that since the sensed AC current generally corresponds to the load current, the current sensing signal also corresponds to the load current, and is therefore very suitable for power transmission control.

[0018] Therefore, it is not necessary to sense a small voltage but rather a high current. However, sensing a high current in a high magnetic AC field environment is less prone to error than sensing a small voltage in such an environment. Thus, detection or sensing errors can be avoided or at least reduced, resulting in no switching errors or a reduced number of switching errors.

[0019] Furthermore, since the sensed current is AC current, it can be sensed passively, resulting in reduced losses.

[0020] The term AC current is used below to refer to the AC current flowing from the secondary resonator to the output stage, unless otherwise indicated or is clear to those skilled in the art in the given context.

[0021] The term "control device" can refer to a device that exclusively controls the synchronous rectifier in the secondary winding. However, it may not necessarily refer to such an exclusive control device. The control device can also control other aspects of the wireless power transmission device. For example, the control device can also perform control of the power transmission from the primary side to the secondary side of the wireless power transmission device. However, the wireless power transmission device may also include a separate controller for controlling the power transmission from the primary side to the secondary side of the wireless power transmission device and / or other aspects of the device.

[0022] In a preferred embodiment of the invention, the current sensing device is adapted to generate a current sensing signal representing the DC output current of the output stage—that is, the current supplied to the load connected to the output stage. In this case, the control of the power transmitted from the primary to the secondary can therefore also be based on the current sensing signal generated by the current sensing device. In this context, the term "represents" means that it should be possible to infer one or more characteristics of the DC output current supplied to the load from the current sensing signal. For example, certain characteristics of the current sensing signal may reflect certain characteristics of the DC output current, such as its amplitude. In a simple and therefore preferred embodiment, the current sensing signal is generated to be proportional to the DC output current. The current sensing signal may also include an offset. However, the current sensing signal may also be generated to have, for example, an exponential relationship with the amplitude of the DC output current used to control power transmission. The current sensing signal may actually have any desired, suitable, or otherwise conditional relationship with the DC output current, as long as it is clearly defined and the desired characteristics (e.g., its amplitude) of the DC output current can be determined. For example, it would also be possible to generate the current sensing signal as an encoded signal, which is transmitted to the power transmission controller, decoded by the power transmission controller, and then used to control power transmission.

[0023] However, power transmission control can also be based on separate current, voltage, or electrical measurements at the same location as the wireless power transmission device or at another suitable location. In this case, the current sensing signal may not necessarily represent the DC current supplied to the load. It will be sufficient that the current sensing signal is generated by the current sensing device such that the phase of the current sensing signal represents the phase of the output current in order to correctly generate the control signal for controlling the controlled rectifier. In this context, the term "represents" means that the phase of the current sensing signal corresponds to or is even equal to the phase of the output current.

[0024] The power delivery controller is preferably implemented as part of the secondary side, as outlined above, and is integrated into a mobile device or automotive device along with a load such as a battery. Since the mobile device or automotive device is only occasionally placed near the primary side for charging its battery or otherwise supplying power to it, control signals for power delivery control must be transmitted from the secondary side to the primary side. Therefore, a cable connection could be established to enable communication between the primary and secondary sides. However, since power delivery itself is wireless, it is preferable to also transmit control signals wirelessly from the power delivery controller to the primary side to avoid establishing a cable connection.

[0025] Therefore, in a preferred embodiment of the invention, the primary and secondary sides include transceivers for wireless communication with each other. Preferably, the communication link is a radio communication link, such as LTE, UMTS, GSM, WLAN, Bluetooth, or any other suitable radio communication technology. Since the primary and secondary sides are arranged close to each other during power transmission, the communication technology is preferably a short-range communication technology, such as WLAN or Bluetooth. Where different frequency ranges of radio communication technologies are available at the location of the system, each of these locally available frequency ranges can be selected. For example, if WLAN technology is to be used, the 2.4 GHz and / or 5 GHz bands can be used. Since each region in the world can identify specific frequency bands that can be freely used within a given, typically low, power transmission range, it is preferable to use radio communication technologies that utilize such free frequency bands.

[0026] In a preferred embodiment of the present invention, the current sensing device includes a first-stage current sensing device and a second-stage current sensing device linked to the output of the first-stage current sensing device.

[0027] First-level and second-level current sensing devices include, for example, current transformers, current sensors using the Hall effect, or other current sensors for sensing AC current.

[0028] The first-stage current sensing device senses the AC current and generates an output current or voltage. In this connection, the term "linked to the output of the first-stage current sensing device" means that the second-stage current sensing device senses the output current or voltage generated by the first-stage current sensing device to generate a current sensing signal as its output current or voltage.

[0029] Since the sensed AC current—after rectification—is used to charge a high-capacity battery at a high charging rate, the AC current to be sensed is a high current with values, for example, reaching hundreds or even thousands of amperes. Therefore, the first-stage current sensing device is preferably adapted to be used with such high currents.

[0030] In a preferred embodiment of the invention, both the first-stage current sensing device and the second-stage current sensing device include a current converter for sensing the AC current flowing from the secondary resonator to the output stage. Current converters are widely used in such applications and can be manufactured at a reasonable cost for the required high ampere ratings. Therefore, the first-stage current sensing device includes a first current converter, and the second-stage current sensing device includes a second current converter.

[0031] As is well known, a current converter typically includes a magnetic core, a primary winding with a certain number of turns through which the current to be sensed flows, and a secondary winding with a certain number of turns, wherein a load resistor is connected between the ends of the secondary winding and wherein the voltage across the load resistor represents the amount of current flowing in the primary winding. The ratio of the number of turns in the secondary winding to the number of turns in the primary winding is called the conversion ratio.

[0032] The first current converter preferably has a conversion ratio between 10:1 and 80:1. The conversion ratio is preferably between 15:1 and 50:1, and even more preferably between 20:1 and 30:1. The conversion ratio of the first current converter is hereinafter referred to as the first conversion ratio.

[0033] Generally, the first current converter has a low number of turns in the primary winding. If the number of turns in the primary winding is, for example, three, then the number of turns in the secondary winding is chosen somewhere between 30 and 240.

[0034] The second current converter preferably has a conversion ratio between 20:1 and 600:1, more preferably between 100:1 and 300:1, and even more preferably between 150:1 and 250:1. The conversion ratio of the second current converter is hereinafter referred to as the second conversion ratio. Generally, the second current converter has a low number of turns in its primary winding. If the number of turns in the primary winding is, for example, three, then the number of turns in the secondary winding is selected somewhere between 60 and 1800.

[0035] The conversion ratios of the two current converters are multiplied. This helps to convert the high primary current into a low current signal. Therefore, the first and second conversion ratios are preferably selected such that the current sensing device has a total conversion ratio between 100:1 and 30000:1, preferably between 500:1 and 15000:1, and more preferably between 2000:1 and 10000:1. Thus, a conversion ratio of 5000:1 can be achieved, for example, using a first conversion ratio of 25:1 and a second conversion ratio of 200:1.

[0036] The conversion ratio of the two current converters can be selected to achieve high-accuracy current sensing. Therefore, several aspects must be considered, such as metering accuracy at the desired current rating, matching the output of the first current converter with the input of the second current converter, and other factors such as the availability of commercial products and their current ratings.

[0037] However, if lower measurement accuracy is acceptable, the conversion ratio of the two current converters can also be selected to be higher or lower than those mentioned above.

[0038] In a preferred embodiment, the primary winding of the first current conductor comprises only a single winding. In other words, the conductor carrying the AC current to be sensed is fed only through the core of the first current converter. To achieve an overall conversion ratio of approximately 5000:1 and high-accuracy current sensing, the conversion ratio of the first current converter is selected to be approximately 25:1 and the conversion ratio of the second current converter is selected to be approximately 200:1, also having only a single turn in its primary winding.

[0039] Using two current transformers connected in series to form a two-stage current sensing device has the following advantages: a high conversion ratio can be achieved while the current sensing device has a high self-resonant frequency. This is preferred because the self-resonant frequency should be significantly higher than the operating frequency of the wireless power transmission device to reduce disturbances and interference and improve efficiency. Preferably, the current sensing device is configured such that its self-resonant frequency is at least ten times the operating frequency. If the operating frequency is, for example, 30 kHz, then the current sensing device is preferably configured to have a self-resonant frequency of at least 300 kHz.

[0040] The self-resonant frequency is proportional to the reciprocal of the square root of the inductance L of the device, where L and N are related. 2 Proportional, where N is the number of turns in the secondary winding of the transducer.

[0041] Therefore, to achieve a conversion ratio of, for example, 1000:1, assuming a single turn in the primary stage, a single-stage current sensor would require 1000 turns in the secondary stage. A two-stage current sensor would, for example, have 10 turns in the secondary stage of the first stage and 100 turns in the secondary stage of the second stage—again assuming a single turn in the primary stage. The resulting two-stage current sensor would therefore have a significantly higher total self-resonant frequency than the single-stage device.

[0042] In wireless power transmission devices used for wirelessly charging high-capacity batteries at high charging rates, the current-carrying conductors typically have a fairly large cross-section. Such conductors are often provided in the form of foil conductors, also referred to below as sheet conductors. Such foil conductors typically have a generally rectangular cross-section with a width much larger than their thickness. Their width is preferably at least 50 times their thickness.

[0043] Typically, such conductors have a thickness several times that of a tenth of a millimeter, for example, a thickness of 0.1 to 0.5 millimeters, and a width of tens of millimeters, for example, a width of 40 to 100 millimeters. Depending on the desired current, such conductors can also be thicker and wider or thinner and narrower.

[0044] In a preferred embodiment of the invention, the first-stage current sensor is optimized to sense current in such a foil conductor. In this respect, the term "optimized" primarily refers to mechanical optimization. However, it can also refer to electrical optimization. Hereinafter, the term "transducer" is sometimes used instead of "current converter."

[0045] The core of this optimized first transducer comprises two rods arranged in parallel on different sides of a conductor carrying AC current. This conductor forms the primary winding of the first transducer and induces a magnetic field by the AC current flowing around it. The two rods are arranged within this magnetic field. They are made of a material with high permeability (e.g., ferrite). In this embodiment, the secondary winding of the first transducer comprises two winding portions connected to each other. A first winding portion is wound around a first rod, and a second winding portion is wound around a second rod, wherein the winding portions are wound around the rods such that the currents induced in the two winding portions flow in the same direction, i.e., they are added together to form the secondary current of the first transducer.

[0046] In this way, the current flowing in the primary winding, i.e., in the conductor carrying the AC current, generates a magnetic field around the conductor, which in turn induces a current flowing in the secondary winding, which is proportional to the AC current in the conductor.

[0047] In a further preferred embodiment, the bars are longer than the conductor and are arranged perpendicular to the longitudinal direction of the conductor, extending beyond the conductor on both sides. Further, the winding portions do not cover the ends of the bars so that each bar reliably forms a core with a gap on each side. More preferably, the winding portions are wound around the bars so that turns exist within the conductor. Or in other words, those portions of the bars that reliably extend beyond the conductor are left unused and do not carry turns of the secondary winding.

[0048] Such a gapped core has a relatively low self-inductance, so the voltage applied to it results in a magnetizing current. However, in this case, the voltage applied to the first transducer is very low. As further outlined below, the current sensing device is typically followed by a rectifier, which provides a rectified version of the sensed AC signal and determines the average value of the sensed current signal, as well as a control signal for generating a controllable rectifier for the output stage. Therefore, the second transducer reduces the reflected voltage from this rectifier by its slew rate. If the second transducer has a slew rate of 200, the reflected voltage is reduced from approximately 1–3 V to 5–15 mV.

[0049] As mentioned above, the advantage of such a transducer device is that the self-resonant frequency of the current transducer is very high, typically at least 10 times the operating frequency of a WL charger.

[0050] More preferably, the individual components forming the transducer are selected such that the resonant frequency of the current transducer is at least 20 times the operating frequency of the WL charger, or even more preferably about 30 times the operating frequency of the WL charger.

[0051] The second current transformer can be of any shape and typically has a higher number of secondary turns compared to the first current transformer. The second current transformer can, for example, be implemented as a standard ferrite core with two coils wound thereon.

[0052] Different methods exist for generating control signals for controlling a controllable rectifier. The control device may include, for example, an analog-to-digital (A / D) converter to convert the current-sensing signal into a digital signal, and a computing unit including, for example, a microprocessor to determine the switching time of the switches for the synchronous rectifier and to control the corresponding drive circuit based on the converted digital signal. However, due to the digital components, the cost will increase.

[0053] In another preferred embodiment of the invention, the control device therefore includes a first comparator for sensing the level of the current sensing signal, a second comparator for sensing the direction of the current sensing signal, i.e., the sign of the sensed current, and logic circuitry adapted to combine the outputs of the first and second comparators to control the controllable rectifier.

[0054] This makes it easy and cost-effective to generate control signals for the controlled rectifier.

[0055] In such an implementation, the current sensing device preferably includes a passive full-wave sensing rectifier for rectifying the output of the current sensing device so that a first comparator can sense the level of the output of the current sensing device. For this purpose, the first comparator is connected across a shunt connected across the output of the sensing rectifier. And to sense the sign of the current, a second comparator is connected across the input of the sensing rectifier.

[0056] In a further preferred embodiment of the invention, the sensing rectifier is a diode rectifier and the current sensing device is adapted to provide current as a current sensing signal. In the case of a full-wave diode rectifier with two diodes in each branch, the input voltage of the sensing rectifier is equal to the sum of the voltage across the shunt and twice the voltage of the diode across the rectifier. This results in a much more robust sensing of the sign of the current because the positive half-wave of the rectifier input voltage increases to twice the diode voltage, and its negative half-wave decreases to half the diode voltage, resulting in a much steeper slope of the rectifier input voltage near zero crossings. Or in other words, the voltage drop across the diode increases the signal-to-noise ratio and makes it possible to detect zero crossings of the current to be sensed more accurately and robustly.

[0057] As an alternative to passive full-wave rectifiers—which offer a low-cost solution with reduced filtering at their output—generally any other rectifier device can be used to provide a rectified version of the sensed current. For example, a half-wave rectifier such as a single diode can be used, as well as a full-wave rectifier with a controlled switch.

[0058] The controllable rectifier preferably includes a plurality of controllable switches, such as MOSFETs. However, other types of electrically controllable switches, such as other transistors, thyristors, or triacs, may also be used.

[0059] In such a controlled rectifier, the switches are typically grouped into at least two subsets, wherein logic circuitry is adapted to provide a first control signal to a first subset of the switches of the controlled rectifier and a second control signal to a second subset of the switches of the controlled rectifier. In the case of a two-switch rectifier, the logic circuitry provides a first control signal to the first switch and a second control signal to the second switch.

[0060] However, the controllable rectifier is preferably implemented as a full-bridge rectifier with two parallel branches, each branch comprising two controllable switches connected in series. In such a rectifier, the switches are controlled in pairs. A first diagonal switch, including the upper switch of the first branch and the lower switch of the second branch, forms a first subset of the switches and is controlled using a first control signal; and a second diagonal switch, including the lower switch of the first branch and the upper switch of the second branch, forms a second subset of the switches and is controlled using a second control signal.

[0061] As outlined above, the first comparator senses the level of the current sensing device's output. To do this, the first comparator is preferably adapted to provide a low signal at its output if the AC current flowing from the secondary resonator to the output stage is high, and a high signal if the AC current is low. In this configuration, the AC current is designated as high if it exceeds a given threshold—preferably selected as a fraction of the maximum output voltage of the sensing rectifier. Therefore, the comparator is used to determine the conduction angle, i.e., the angle at which a given switch is on during one cycle.

[0062] The goal is to control the switch to achieve the largest possible conduction angle to minimize losses. However, the conduction angle may not be 180°, as this could lead to erroneous switching. Therefore, the switch is preferably controlled to achieve a conduction angle between 120° and 180°, preferably between 150° and 179°, and even more preferably between approximately 165° and 177°.

[0063] In a charger with an operating frequency of, for example, 50 kHz, the half-cycle lasts for 10 μs. To achieve, for example, a 170° turn-on, the switch can be turned on for approximately 150 ns to 300 ns after crossing zero, and it can be turned off for approximately 150 ns to 300 ns before the next zero crossing.

[0064] Since the current is typically sinusoidal, the threshold level is preferably selected to be approximately 5% to 10% of the maximum amplitude of the rectifier's output. Of course, the first comparator can also be adapted to provide different thresholds for turning the switch on and off, such that the switch is turned on if the rectifier output reaches, for example, 6% of its maximum value, and the switch is turned off if the rectifier output drops to, for example, 9% of its maximum value.

[0065] The second comparator detects the direction of the sensed current. The result is used to determine the effective diagonal of the synchronous rectifier. Therefore, the second comparator must be located upstream of the sensed rectifier, i.e., at the input of the sensed rectifier, or more generally, in front of the sensed rectifier.

[0066] Preferably, the second comparator is adapted to provide a high signal if the AC current is positive and a low signal if the AC current is negative.

[0067] In a preferred embodiment of the invention having two comparators as described above, the logic circuit is adapted to provide:

[0068] - A first control signal is used to turn on a first subset of switches and turn off a second subset of switches if the first comparator provides a low signal at its output and the second comparator provides a high signal at its output.

[0069] - A first control signal, used to turn off a first subset of switches and turn on a second subset of switches if both the first and second comparators provide a low signal at their outputs.

[0070] - A first control signal and a second control signal are used to turn off both a first subset of switches and a second subset of switches, regardless of the output signal of the second comparator, if the first comparator provides a high signal at its output.

[0071] Or in other words, the logic circuit is adapted to provide:

[0072] - A first control signal, used to turn on a first subset of switches and turn off a second subset of switches if the AC current is positive and high (i.e., above a threshold).

[0073] - A second control signal, used to turn on a second subset of switches and turn off a first subset of switches if the AC current is negative and high (i.e., above a threshold), and

[0074] - First control signal and second control signal, used to turn off the first subset of switches and the second subset of switches if the AC current is low (i.e., below the threshold).

[0075] However, it will be clear to those skilled in the art that the logic circuit can also be constructed in different ways, as long as it matches the output of the comparator and produces the same output signal for controlling the controllable rectifier.

[0076] For example, the first comparator can also be adapted to provide a low signal at its output if the AC current is low, and a high signal if the AC current is high. And the second comparator can be adapted to provide a high signal if the AC current stage is negative, and a low signal if the AC current is positive.

[0077] In this case, the logic circuit will have to be adapted to provide:

[0078] - A first control signal is used to turn on a first subset of switches and turn off a second subset of switches if the first comparator provides a high signal at its output and the second comparator provides a low signal at its output.

[0079] - A first control signal, used to turn off a first subset of switches and turn on a second subset of switches if both the first and second comparators provide a high signal at their outputs.

[0080] - A first control signal and a second control signal are used to turn off a first subset of switches and a second subset of switches regardless of the output signal of the second comparator if the first comparator provides a low signal at its output.

[0081] As mentioned above, the current sensing signal generated by the current sensing device can also be used for power transfer control from the primary to the secondary side of a wireless power transfer device. Power transfer control can be based on any suitable measurement of parameters representing the current, voltage, or power transmitted to the load (such as, for example, the DC current supplied to the load, or, as described above, the current flowing from the secondary resonator to the output stage).

[0082] The measurement signal provided to the power control device can be, for example, the AC output of a current sensing device. However, this would create a more complex controller, as the sensed signal would have to be processed by the controller to extract the information required to control the power transfer. The measurement signal provided to the power control device can also be any other signal representing the load current. However, again, depending on the type or kind of signal provided to the power control unit, there may be specific needs for processing the received signal to extract the information required for precise control of the power transfer from the primary side to the secondary side and further to the load.

[0083] To simplify and enhance power delivery control, in another preferred embodiment of the invention, a current signal provided to the power controller is preferably generated to represent the average value of the sensed AC current. In a further preferred embodiment of the invention, the current sensing device therefore includes an averaging device connected to the current sensing device for generating an average value of the current sensing signal representing the average value of the AC current flowing from the secondary resonator to the output stage. Therefore, the power delivery controller is preferably adapted to control wireless power delivery based on the average value of the current sensing signal.

[0084] The average value of the sensed current signal can be determined, for example, by sampling the sensed signal, converting it into a digital signal using an analog-to-digital converter and a digital processor, and then calculating the average value of the sample in a purely digital manner.

[0085] However, in another preferred embodiment of the invention, the averaging device includes an averaging rectifier for rectifying the current sensing signal and an averaging filter connected to the output of the sensing rectifier. The averaging filter converts the rectified AC output signal of the rectifier into a DC signal representing the average value of the output of the current sensing device.

[0086] Therefore, the average value of the current sensing signal is provided at the output of the averaging filter. The averaging filter thus provides at its output a current sensing signal representing the average value of the AC current to be sensed. Therefore, this average value is proportional to the current conducted to the battery. To avoid losses in the sensing / averaging rectifier, the conversion ratio of the current transducer is preferably selected to be quite high, such as, for example, 1000:1, or more preferably even higher, such as approximately 5000:1.

[0087] The average rectifier can be of any kind, with active or passive components. Active components include controlled switches in the form of transistors or other transistors based on semiconductor elements, while passive components include diodes. Hybrid implementations are also possible. The rectifier can also be a half-wave or full-wave rectifier. To provide an accurate picture of the sensed AC current, the rectifier is preferably a passive full-wave rectifier comprising four diodes in a full-bridge configuration. Due to the low power present at the output of the current sensing device, a synchronous rectifier with controlled switches is not necessary.

[0088] The averaging filter can include any type of filter used to smooth and / or filter the rectifier output. A simple RC circuit with a series resistor and a parallel capacitor is preferred, and it sufficiently reduces ripple to provide an accurate average value of the sensed signal. However, depending on the specific application and accuracy requirements, other filters such as a single parallel capacitor or an LC circuit can be used.

[0089] The average rectifier can be implemented as a component other than the sensing rectifier mentioned above, and it is used in the circuit to generate control signals for the controllable rectifier in the output stage.

[0090] However, in a further preferred embodiment of the invention, the sensing rectifier is also used as an averaging rectifier. Therefore, the output of the sensing rectifier is connected to an averaging filter. This helps reduce the number of required components.

[0091] The present invention further relates to a secondary side for a wireless power transfer device, comprising a secondary resonator for converting electricity received via a magnetic field into secondary AC power and an output stage for converting the secondary AC power into DC output power. According to the invention, the secondary side includes: a current sensing device adapted to generate a current sensing signal; a power transfer controller adapted to control the wireless power transfer based on the current sensing signal; and a control device for controlling a controllable rectifier, wherein the current sensing device includes a current sensing apparatus adapted to generate the current sensing signal by sensing AC current flowing from the secondary resonator to the output stage, and wherein the control device is adapted to control the controllable rectifier based on the current sensing signal.

[0092] The current sensing device according to the invention for a wireless power transmission device as described above is adapted to sense AC current flowing from the secondary resonator of the wireless power transmission device to the output stage of the wireless power transmission device.

[0093] Preferred embodiments of the current sensing device according to the present invention exhibit one or more of the features mentioned above.

[0094] In a preferred embodiment, the current sensing device includes, for example, a first-stage current sensing device and a second-stage current sensing device linked to the output of the first-stage current sensing device.

[0095] The solution of the present invention regarding a method for wireless power transmission is specified by the features of the technical solution of the present invention. The method includes the following steps:

[0096] a) The input stage converts the input power received at the power input on the primary side into primary AC power, and receives the primary AC power and induces a magnetic field using the primary resonator;

[0097] b) Use a secondary resonator to convert the power received through the magnetic field into secondary AC power, and use an output stage with a controllable rectifier to convert the secondary AC power into DC output power;

[0098] c) A current sensing signal is generated using a current sensing device, and a power delivery controller is used to control power delivery based on the current sensing signal.

[0099] d) Use a control device to control the controllable rectifier.

[0100] According to the present invention, the method further includes the following steps:

[0101] e) A current sensing signal is generated by sensing the AC current flowing from the secondary resonator to the output stage using a current sensing device, and

[0102] f) Controllable rectifier based on current sensing signal.

[0103] Other advantageous combinations of embodiments and features will emerge from the following detailed description and the overall technical solution of the invention. Attached Figure Description

[0104] The accompanying drawings, used to explain the embodiments, show:

[0105] Figure 1 This is a schematic representation of a wireless power transmission device according to the present invention;

[0106] Figure 2 This is a schematic representation of the input stage of the wireless power transmission device according to the present invention;

[0107] Figure 3 This is a schematic representation of a primary resonator used in a wireless power transmission device according to the present invention;

[0108] Figure 4 This is a schematic representation of a secondary resonator used in a wireless power transmission device according to the present invention;

[0109] Figure 5 This is a schematic representation of the output stage of the wireless power transmission device according to the present invention;

[0110] Figure 6 This is a schematic representation of a current sensing device for a wireless power transmission device according to the present invention;

[0111] Figure 7 This is a more detailed schematic representation of a current sensing device for a wireless power transmission device according to the present invention;

[0112] Figure 8 This is a schematic representation of a first current sensing device for a wireless power transmission device according to the present invention;

[0113] Figure 9 It is a schematic representation of a circuit used to generate a current sensing signal for controlling wireless power transmission;

[0114] Figure 10 It is a schematic representation of a control device used to control a controllable rectifier;

[0115] Figure 11 It is a schematic representation of a combination circuit for generating a current sensing signal for controlling wireless power transmission and a controllable rectifier; and

[0116] Figure 12 yes Figure 11 A more detailed schematic representation of the combinational circuit is shown below.

[0117] In each figure, the same components are given the same reference number. Detailed Implementation

[0118] Figure 1 A schematic representation of a wireless power transfer device 1 according to the present invention is shown. The wireless power transfer device 1 includes a primary side 2, a secondary side 3, and a power transfer controller 15. The primary side 2 includes an input stage 5 for converting input power 4 into AC primary output power 7 fed to a primary resonator 6. The primary resonator 6 induces a magnetic field 9 to wirelessly transmit power across an air gap 8. The secondary side 3 includes a secondary resonator 10 that picks up the magnetic field 9 and converts the power received through the magnetic field 9 into an AC secondary output 12. The output stage 11 AC receives the AC secondary output 12 of the secondary resonator 10 and converts the AC secondary output 12 into a DC secondary output 13, which is then provided as output power 14 at the output of the wireless power transfer device 1.

[0119] Controller 15 controls the power delivery from the primary side 2 through the air gap 8 to the secondary side 3 and thus to the load connected to the DC secondary output 13 to meet the requirements of a particular application. Controller 15 controls the primary side 2 to, for example, meet the specific output power 14 required by the device connected to the output stage 11. In cases where the load includes, for example, a battery to be charged by the wireless power delivery device 1, controller 15 may receive a power setting value from the load, such as a current setting value 19 from the battery management system (BMS) of the load battery.

[0120] Since the secondary side and the load / battery are typically located at, on, or within the mobile device, i.e., in close proximity to each other, they preferably communicate with each other via a wired communication link. To avoid unnecessary wiring, such a communication link is preferably a wired bus communication system. Depending on the specific application, any suitable bus system (standardized or non-standardized) can be used. Examples of such buses are HIPPI (High Performance Parallel Interface), IEEE-488, PC Card (PCMCIA), CAN bus (Controller Area Network), eSATA, ExpressCard, Fieldbus, IEEE1394 interface (FireWire), Lightning, RS-232, RS-485, Thunderbolt, USB (Universal Serial Bus), or any predecessor, variant, or successor to these bus systems, and any other known bus system can be used. Furthermore, any suitable communication protocol can be used for communication using any of these buses. In vehicle or automation applications, a CAN bus system combined with the CANopen protocol is preferably used in connection with this invention.

[0121] The wireless power transmission device 1 further includes a current sensing device 18 for measuring the AC secondary output 12, particularly for measuring the current flowing from the secondary resonator 10 to the output stage 11. The current sensing device 18 provides a current sensing signal 16 to the controller 15, which generates a control signal 17 based on the current sensing signal 16 to control the primary side 2 to induce a magnetic field 9 to satisfy the required output power 14.

[0122] Based on the current sensing signal 16 and the current setpoint 19, the controller 15 determines a control signal 17 for the primary side 2. The controller 15 is configured, for example, to generate the control signal 17 by calculating the difference between the current setpoint 19 and the current sensing signal 16.

[0123] The wireless power transmission device 1 further includes a switch controller 20 for controlling the output stage 11, particularly for controlling the conversion from AC secondary output 12 to DC secondary output 13. This conversion is performed, for example, by a controlled rectifier. In such a configuration, one or more switches of the controlled rectifier are controlled by a control signal 21, which is provided to the output stage 11 by the switch controller 20. The switch controller 20 is adapted to generate these control signals 21 based on a current sensing signal 16 also fed to the switch controller 20 from the current sensing device 18.

[0124] Although the power delivery controller 15 and the switch controller 20 are shown as separate units, they can also be implemented as a single controller unit. Alternatively, they can be integrated (individually or in combination) into... Figure 1 In any of the units shown, the two controllers are preferably part of the secondary side of the wireless power transmission device. Each controller can also be divided into further sub-units to separately control, for example, the frequency and switching in the primary side. Each controller can also perform additional control functions of the wireless power transmission device or even functions of other devices not shown.

[0125] Input stage 5 includes, for example, a converter device for converting input power 4 into AC primary output power 7. In the case of AC input power 4, the converter device includes, for example, an AC / DC stage, a DC link, and a DC / AC inverter. In such a configuration, control signal 17 includes signals for controlling input stage 5, for example, by providing control signals 17 for switching the inverter.

[0126] As outlined above, the power delivery controller 15 is typically implemented as part of the secondary side, so the control signal 17 will be transmitted to the primary side. In this example, the control signal 17 is transmitted to the primary side using a wireless communication technology such as, for example, Bluetooth or WLAN. Therefore, both the secondary and primary sides include Bluetooth or WLAN transceivers to establish communication and, in particular, to transmit the control signal 17.

[0127] Figure 2 A schematic representation of an exemplary embodiment of the input stage for a wireless power transfer device according to the invention is shown. The input stage is connected to an AC power source providing AC input power 36. An AC / DC converter 35 converts the AC input power 36 into a fixed DC intermediate power 38', which is then converted into a variable DC intermediate power 38 by a DC / DC converter 37. The fixed DC intermediate power 38' can be, for example, power at 800V and the variable DC intermediate power 38 can be, for example, DC power between 0V and 800V, depending on the actual power requirements at the secondary. The variable DC intermediate power 38 is fed to an inverter 39, which converts the variable DC power 38 into AC output power 40. To convert the variable DC intermediate power 38 into AC output power 40, the inverter 39 includes four controllable switches 41 in a full-bridge configuration. Soft switching can be used for efficient operation of the inverter 39, instead of providing an additional DC / DC stage between the AC / DC converter and the DC / AC inverter for voltage control. However, in this case, soft switching may no longer be used to switch the DC / AC inverter.

[0128] The frequency and amount of power supplied at the output power 40 can be controlled by switching the control switch 41, for example by PWM (pulse width modulation), which can control not only the duty cycle of the pulse but also the frequency of the pulse.

[0129] Therefore, to control power delivery, the frequency can be controlled by controlling the frequency of inverter 39 and / or the variable DC intermediate power 38 at the input of inverter 39. Control of the frequency of inverter 39 and / or the variable DC intermediate power 38 is typically accomplished based on control signals received from the secondary side via wireless transmission. The input stage may further include a controller (not shown) for providing switching control signals for switching switch 41, wherein the switching control signals are derived from the control signals received from the secondary side.

[0130] MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) are frequently used as controllable switches in such converters and are also preferred in this invention. However, other types and kinds of controllable switches can be used, such as other transistors, thyristors, or triacs.

[0131] The input level can include not only Figure 2 The components shown in the diagram, and usually include further components such as filters to optimize their operation.

[0132] Generally, different types of input stages can be used on the primary side for use in the wireless power transmission device according to the invention, as long as it converts the supplied input power into controllable AC output power.

[0133] Figure 3 A schematic representation of a primary resonator 45 for use in a wireless power transmission device according to the invention is shown. The primary resonator 45 can, for example, be connected to, a device such as... Figure 2 The input stage is shown in the diagram. Therefore, the primary resonator 45 receives AC input power 46 at its input.

[0134] The primary resonator 45 essentially comprises a tuning circuit with a resistor 47, a capacitor 48, and a coil 49 connected in series. By applying AC power to the input of the primary resonator 45, the primary resonator 45 begins to oscillate, thereby inducing a magnetic field emitted into the region surrounding the resonator. However, the shape, orientation, and distribution of the magnetic field lines can be affected by certain measures. Therefore, one or more field guiding elements (in the form of a magnetic core 50 in this case) are provided to guide the magnetic field in the direction desired for a particular application. Typically, the magnetic field lines are modified so that most of the energy transferred into the magnetic field can be picked up by the receiving resonator to reduce or minimize losses.

[0135] Generally, a primary resonator may also include further or fewer elements, and some or all of its elements may be connected in parallel to form a resonant circuit for generating a magnetic field for power transmission.

[0136] Figure 4 A schematic representation of a secondary resonator for a wireless power transmission device according to the invention is shown. The secondary resonator 55 can, for example, be used to pick up signals from sources such as... Figure 3 The magnetic field generated by the primary resonator 45 is shown in the figure.

[0137] The secondary resonator 55 corresponds primarily to the primary resonator 45. It essentially also includes a tuning circuit with a resistor 57, a capacitor 58, and a coil 59 connected in series. By appropriately arranging the secondary resonator 55 within the magnetic field generated by the primary resonator 45, the secondary resonator 55 can pick up energy transferred via the magnetic field and convert that energy into AC output power 56 provided at its output. To pick up as much energy as possible from the magnetic field (i.e., as many magnetic field lines as possible), the secondary resonator 55 also includes one or more flux guiding elements (also in the form of a magnetic core 60).

[0138] Furthermore, the secondary resonator may also include further or fewer elements, and some or all of its elements may be connected in parallel to form a resonant circuit for picking up magnetic fields.

[0139] Figure 5 A schematic representation of an output stage for use in a wireless power transmission device according to the invention is shown.

[0140] The output stage includes an AC / DC converter 65, which is connected to, for example, in... Figure 4 The output of the secondary resonator 55 shown is illustrated. The AC / DC converter 65 converts AC power 66 received at its input into DC output power 70 provided at its output. AC power 66 includes, for example, a current 74 flowing into the AC / DC converter 65. In this embodiment of the invention, the AC / DC converter includes a synchronous rectifier 67 with four switches 71 in a full-bridge configuration, followed by a bulk capacitor 68 for shaping the DC output power 70 and an output filter 69. The AC / DC converter 65 may also include... Figure 10 Further components are not shown. Therefore, the DC output power 70 provides DC current at a specific DC voltage.

[0141] In this example, the output stage is also shown as including a current sensing device 78 and a controller 75 that receives a current setpoint 79. The current sensing device 78 determines the current 74 and provides a current sensing signal 76 to the controller 75. In this embodiment, the controller 75 is a combined controller. It not only generates a control signal 77 that is fed to the primary side of the wireless power transmission device to control the power transmission of the device, wherein the control signal 77 is determined, for example, by calculating the difference between the current setpoint 79 and the current sensing signal 76, but also generates control signals 72, 73 for controlling the AC / DC converter 65 that converts AC power 66 into DC output power 70. Therefore, control signal 77 and control signals 72, 73 are generated by the controller 75 taking into account the current sensing signal 76 provided by the current sensing device 78.

[0142] Switch 71 is implemented using a FET (Field-Effect Transistor), although other switches such as other transistors can also be used. Control signals 72 and 73 are fed to the gate of switch 71. (As in...) Figure 5 As shown, control signal 72 is fed to the control inputs of switches 71 at the upper left and lower right of rectifier 67, and another control signal 73 is fed to the control inputs of switches 71 at the upper right and lower left of rectifier 67. Thus, and as is known in the art, the diagonally arranged switches are controlled by the same control signal.

[0143] Generally, different types of converters can be used to convert an AC input provided by a secondary resonator into a DC output. The DC output can also be gradually increased or decreased as required by a particular application. It is also possible to convert the DC output back into an AC output with given characteristics required by a particular application.

[0144] Figure 6 A schematic representation of a current sensing device 118 for a wireless power transmission device according to the present invention is shown. The current sensing device 118 is a two-stage current sensing device 118 having a first-stage current sensing device 101 and a second-stage current sensing device 102. The first-stage current sensing device 101 senses a current 104 flowing in a conductor 103 and provides an output signal representing the current 104. In this case, the first-stage current sensing device 101 provides an output current 114 representing the current 104. The second-stage current sensing device 102 then senses the output current 114 of the first-stage current sensing device 101 and provides an output signal representing the current 114 and thus also representing the current 104. In this case, the second-stage current sensing device 102 provides an output voltage 115 representing the current 114 and thus also representing the current 104.

[0145] The first-stage current sensing device 101 and the second-stage current sensing device 102 are typically adapted to provide an output signal proportional to the sensed current. In this case, current 114 is therefore proportional to current 104, and voltage 115 is proportional to current 114, and thus voltage 115 is also proportional to current 104.

[0146] Figure 7 A more detailed schematic representation of the current sensing device 128 for a wireless power transmission device according to the invention is shown. In this example, the current sensing device 128 is again a two-stage current sensing device 128, wherein the first-stage current sensing device is a current converter 121, and wherein the second-stage current sensing device is also a current converter 122.

[0147] The first-stage current converter 121 senses a current 124 flowing in the conductor 123 and provides an output current 134 proportional to the current 124. The first-stage current converter 121 includes a closed-loop magnetic core 125 through which the conductor 123 is fed to form the primary winding of the first-stage current converter 121. The current 124 flowing in the conductor 123 thereby induces a magnetic flux within the magnetic core 125. The first-stage current converter 121 further includes a secondary winding 126 wound around the closed-loop magnetic core 125, wherein the ends of the secondary winding 126 are connected to each other. Therefore, the magnetic flux flowing within the magnetic core 125 induces a current 134 flowing through the secondary winding 126.

[0148] In this example, the second-stage current converter 122 is quite similar to the first-stage current converter 121. The second-stage current converter 122 senses the current flowing in the conductor and provides an output current proportional to the sensed current.

[0149] The second-stage current converter 122 includes a closed-loop magnetic core 135, through which the secondary winding 126 of the first-stage current converter 121 is fed to form the primary winding of the second-stage current converter 122. The current 134 flowing in the secondary winding 126 thereby induces a magnetic flux within the magnetic core 135. The second-stage current converter 122 further includes a secondary winding 136 wound around the closed-loop magnetic core 135, and wherein the ends of the secondary winding 136 are connected to the ends of a resistor 139. Therefore, the magnetic flux flowing within the magnetic core 135 induces a current 144 flowing through the secondary winding 136 and the resistor 139. Thus, the second-stage current converter 122 senses the current 134 flowing in the secondary winding 126 and provides an output current 144 proportional to the current 134. Furthermore, since current 134 is proportional to the current 124 flowing in conductor 123, current 144 is also proportional to current 124. The output of current sensing device 128 can be current 144, or it can also be the voltage across resistor 139. Further, the output of current sensing device 128 can also be provided as the voltage across a capacitor connected between the ends of secondary winding 136. In another example, the ends of secondary winding 136 can be provided as the output of current sensing device 128 to subsequent circuitry.

[0150] Closed-loop magnetic core 125 and closed-loop magnetic core 135 in Figure 7 The core is shown as a toroidal core, particularly a hypertoroidal core. However, cores do not have to be identical to each other or necessarily toroidal. Closed-loop cores can have any shape, as long as they allow magnetic flux to flow within the core. Therefore, rectangular cores can also be used. Furthermore, cores can be implemented with or without features such as, for example, in… Figure 8 The air gap is shown in the image.

[0151] Figure 8 A schematic representation of a first-stage current converter 158 used in a wireless power transmission device according to the invention is shown. The current converter 158 is used, for example, as a first-stage current sensing device used in the invention.

[0152] The current converter 158 is therefore adapted to sense the current flowing in the conductors on the secondary side of the wireless power transmission device according to the invention, particularly the current flowing in the conductors carrying the current flowing from the secondary resonator to the output stage. In such a wireless power transmission device, the current flowing from the secondary resonator to the output stage is typically high, and therefore this conductor is often implemented as a foil conductor 153. Figure 8 The cross-section of the foil conductor 153 is shown, so that the current flowing in the foil conductor flows perpendicular to the plane of the figure.

[0153] The magnetic core of the current converter 158 includes two rods 155.1 and 155.2, wherein the first rod 155.1 is arranged on the upper side of the foil conductor 153, and the second rod 155.2 is arranged on the lower side of the foil conductor 153. Both rods 155.1 and 155.2 are shown arranged parallel to the plane of the drawing, which means that they are arranged perpendicular to the longitudinal direction of the foil conductor 153.

[0154] Both rods 155.1 and 155.2 are longer than the width of foil conductor 153 so that an air gap 157 is created on both sides of foil conductor 153 between the ends of the two rods 155.1 and 155.2.

[0155] Therefore, the foil conductor forms the primary winding of the current converter 158. The secondary winding 156 is formed by a first coil 156.1 wound around a first rod 155.1 and a second coil 156.2 wound around a second rod 155.2, wherein the first coil 156.1 and the second coil 156.2 are connected to each other or even wound around the rods 155.1 and 155.2 using a single wire. The first coil 156.1 and the second coil 156.2 are wound around the rods 155.1 and 155.2 such that the currents induced in these coils are added together.

[0156] The primary winding of the current converter 158, i.e., the foil conductor 153, comprises a single turn, and the secondary winding 156 is shown as comprising 24 turns, wherein the first coil 156.1 comprises half of the turns and the second coil 156.2 comprises half of the turns. Therefore, the current converter 158 has a conversion ratio of approximately 24:1.

[0157] To achieve a total conversion ratio of approximately 5000:1 when the current sensing device has a current converter 158 as its first-stage current sensing device, the second-stage current sensing device must have a conversion ratio of approximately 208:1. The second-stage current sensing device can be, for example, as shown in... Figure 7 The current sensor shown has approximately 210 turns in its secondary winding.

[0158] Figure 9 A schematic representation of circuitry 160 for generating a current-sensing signal for controlling wireless power transmission is shown. Circuitry 160 includes a rectifier 161 and a filter 162 connected to the output of rectifier 161. Rectifier 161 receives a sensed current signal 163. Rectifier 161 is connected, for example, to a filter such as... Figure 6 or Figure 7 The output of the current sensing device shown in the figure, wherein the sensed current signal 163 can be in the form of current or voltage.

[0159] The sensed current signal 163 is provided as the current fed to the rectifier 161.

[0160] The rectified output of rectifier 161 is fed to filter 162 for smoothing and / or filtering of the rectifier output to provide an average value of the sensed current signal 163 at the filter output. Rectifier 161 comprises, for example, a simple four-diode full-bridge rectifier, and filter 162 comprises, for example, an RC filter with a series circuit of resistors and capacitors, wherein an average value is provided across the capacitors. This average value thus represents the current flowing from the secondary resonator to the output stage and is designated as the current sensing signal 167. This current sensing signal can then be fed to a controller for controlling the power delivery of the power delivery device according to the invention.

[0161] Figure 10 A schematic representation of a control device 170 for controlling a controllable rectifier of an output stage is shown. The control device 170 includes a rectifier 171, a first comparator 174, a second comparator 175, and logic circuitry 176.

[0162] Rectifier 171 receives the sensed current signal 173, which is again provided as current. Rectifier 171 is connected, for example, to a... Figure 6 or Figure 7 The output of the current sensing device shown in the figure is similar to that of... Figure 9 The rectifier 161 shown is similar.

[0163] A first comparator 174 is connected to the output of rectifier 171 and compares the rectified output with a threshold to provide a specified output signal representing the level of the sensed current signal 173. If the rectifier output is above a specific voltage level, the first comparator 174 provides a high signal at its output, for example. Alternatively, if the rectifier output is above that voltage level, the first comparator 174 provides a low signal at its output.

[0164] The sensed current signal 173 is also fed to a second comparator 175, which compares the sensed current signal 173 with another threshold to determine whether the sensed current signal 173 is currently in its negative half-wave or its positive half-wave. If the sensed current signal 173 is in its negative half-wave, the second comparator 175 provides a high signal at its output, for example, and if the sensed current signal 173 is in its positive half-wave, the second comparator 175 provides a low signal at its output, or vice versa.

[0165] The outputs of each comparator 174 and 175 are then fed to logic circuit 176, which in turn generates control signal 177 for controlling the switching of a controllable rectifier in the output stage of the wireless power transmission device according to the invention.

[0166] Therefore, the first comparator 174 determines at what angle the switches are turned on and off, and the second comparator 175 determines which switches of the controlled rectifier will be turned on and off. In the case of a full-bridge rectifier, the second comparator determines which diagonal of the switches will be turned on and off.

[0167] Figure 11 A schematic representation of a control circuit 180 for generating current sensing signals for controlling wireless power transmission and for controlling a controllable rectifier is shown. The control circuit is... Figure 9 The circuit 160 shown in the figure and Figure 10 The combination of control devices 170 shown in the figure, wherein control circuit 180 includes only a common rectifier for both circuits.

[0168] Control circuit 180 includes a single rectifier 181 and a filter 182 for smoothing and filtering the output of rectifier 181. Rectifier 181 receives signals such as... Figure 9 The sensed current signal 183 is described in relation to this. The sensed current signal 183 is then rectified by rectifier 181 and filtered by filter 182 to provide a current sensing signal 187 at the filter output. The current sensing signal 187 can then be fed to a controller for controlling the power delivery of the power delivery device according to the invention.

[0169] Furthermore, the control circuit 180 includes a first comparator 184, a second comparator 185, and logic circuit 186. Similar to... Figure 10 The control circuit 170 shown includes a first comparator 184 that determines the angle at which the switches are turned on and off, and a second comparator 185 that determines which switches of the controlled rectifier will be turned on and off. Logic circuit 186 generates control signals 188 for the switches of the controlled rectifier in the output stage on the secondary side.

[0170] Figure 12 Shown in Figure 11 A more detailed schematic representation of the combinational circuit 180 shown is provided. The sensed current signal 183 is fed to rectifier 181 in the form of current. In this example, rectifier 181 is a simple diode rectifier with four diodes in a full-bridge configuration. The output of rectifier 181 is fed to filter 182, which is an RC filter with a series circuit of resistor 182.1 and capacitor 182.2 connected across the output terminals of rectifier 181. The resistor can also be split into two resistors connected across capacitor 182.2. The voltage across filter 182 corresponds to the average value of the sensed current signal 183, and therefore also to the sensed AC current flowing from the secondary resonator to the output stage of the power transmission device. This average value output across filter 182 forms a current sensing signal 187, which is fed to the controller of the power transmission device to enable control of the transmitted power based on the sensed AC current.

[0171] The combinational circuit 180 may also include additional scaling elements connected to the output of the filter 182 to provide the power transmission controller with a current sensing signal 187 of appropriate level. Such a scaling stage may include, for example, a differential amplifier to multiply the current sensing signal 187 by an appropriate factor such that the current sensing signal 187 meets the requirements of the controller input.

[0172] The combinational circuit 180 further includes a shunt 189 connected across the output of the rectifier 181 to determine the rectifier output voltage. The positive terminal 192 of the shunt 189 is connected to the inverting terminal of a first comparator 184, and a reference voltage 194 is connected to the non-inverting terminal of the comparator 184. Therefore, when the voltage at the inverting terminal of the comparator 184 becomes higher than the voltage at the non-inverting terminal of the comparator 184, the output 196 of the comparator 184 becomes low, and otherwise it is high.

[0173] Additional components may be connected to one or both terminals of comparator 184, or connected in the wiring to the terminals of shunt 189 or to the terminal of reference voltage 194 leading to the input terminals of comparator 184, to ensure that the comparator input signals have appropriate levels for proper comparison with each other. For example, a resistor may be provided in the wiring from the positive terminal 192 of shunt 189 to the inverting terminal of comparator 184. The reference voltage 194 may be provided, for example, by a suitable voltage source. Alternatively, the reference voltage 194 may be generated using a voltage divider from the supply voltage of comparator 184 to ground (e.g., the negative terminal 193 of shunt 189).

[0174] Since the first comparator 184 determines the on-time and off-time of the controllable rectifier in the output stage, the output of comparator 184 indicates when the rectified voltage value of the sensed current signal 183 is higher than a given threshold. The additional circuitry is therefore selected such that the output 196 of comparator 184 goes low when the sensed current signal 183 is high (i.e., above the threshold) and goes high when the sensed current signal 183 is low (i.e., below the threshold). Therefore, the positive terminal of shunt 189 is fed directly to the inverting terminal of comparator 184, for example, via a resistor, but a voltage divider is provided between the negative terminal of shunt 189 and the non-inverting terminal of comparator 184 to appropriately adjust the threshold. The choice of the threshold directly affects the switching angle. Therefore, specific values ​​for the components of the additional circuitry are selected depending on the application and the selection of other components such as the comparator. They are thus selected to achieve a reasonable switching angle, for example, approximately 170°.

[0175] The sensed current signal 183 is provided to the combination circuit 180 as the current flowing into the combination circuit 180. The positive input terminal 190 is fed to the non-inverting terminal of the comparator 185, and the negative input terminal 191 is fed to the inverting terminal of the comparator 185. Therefore, when the voltage at the non-inverting terminal of the comparator 184 becomes higher than the voltage at the inverting terminal of the comparator 184, the output 197 of the comparator 185 becomes low, and otherwise it is high.

[0176] Again, additional components may be connected to one or both inputs of comparator 185 or in the wiring from the positive input terminal 190 or from the negative input terminal 191 to the input terminal of comparator 185 to ensure that the two comparator input signals have appropriate levels to be suitably comparable to each other. For example, a resistor may be provided in the wiring from the positive terminal 190 and / or the negative terminal 191 to the input terminal of comparator 185, or a voltage divider may be provided between the supply voltage and one or both of terminals 190 and 191 to provide an input signal to comparator 184 at a suitable level for comparison.

[0177] The second comparator 185 determines which switches of the controlled rectifier should be turned on and off. Therefore, it is adapted to detect zero crossings of the input signal by directly comparing the voltage at the non-inverting terminal with the voltage at the inverting terminal.

[0178] Therefore, additional circuitry is selected such that the output 197 of comparator 185 goes high when the sensed current signal 183 becomes positive and goes low when the sensed current signal 183 becomes negative. Thus, two generally identical voltage dividers are used to feed input terminals 190, 191 to the terminals of comparator 185, possibly with small differences in the voltage division to enable hysteresis and / or a small delay until the output level of comparator 185 changes.

[0179] Logic circuit 186 combines the outputs 196 and 197 of two comparators 184 and 185 to provide control signals 188.1 and 188.2. Logic circuit 186 typically includes multiple logic gates, which are preferably selected to be identical. Figure 12 In the example, logic circuit 186 includes three NOR gates 186.1, 186.2, and 186.3.

[0180] The first NOR gate 186.1 receives two outputs 197 of the second comparator 185, and thus provides a low output 198 if the output 197 of the second comparator 185 is high, and provides a high output 198 if the output 197 of the second comparator 185 is low.

[0181] The second NOR gate 186.2 receives the output of the first NOR gate 186.1 and the output 196 of the first comparator 184, and therefore provides a high output 188.1 if both the output of the first NOR gate 186.1 and the output 196 of the first comparator 184 are low, and otherwise provides a low output 188.1.

[0182] The third NOR gate 186.2 receives the output 196 of the first comparator 184 and the output 197 of the second comparator 185. Therefore, if both the output 196 of the first comparator 184 and the output 197 of the second comparator 185 are low, it provides a high output 188.2; otherwise, it provides a low output 188.2. For example, control signal 188.1 is used to control... Figure 5 The first diagonal of the synchronous full-bridge power rectifier is shown, and control signal 188.2 is used to control the second diagonal of such a synchronous full-bridge power rectifier, wherein the first diagonal includes the upper left and lower right switches of the synchronous full-bridge power rectifier, and the second diagonal includes the upper right and lower left switches of the synchronous full-bridge power rectifier.

[0183] This yields the following truth table for control signals 188.1 and 188.2:

[0184] .

[0185] V 183 This specifies the voltage of the sensed current signal 183, and V 189 Specify the voltage across shunt 189, where V 189 The related "high" means V 189 Above the threshold, where "low" means V 189 Below the threshold.

[0186] A "low" value for control signals 188.1 and 188.2 means that the corresponding switch is turned off, and a "high" value means that they are turned on. A "high" value, for example, corresponds to a positive supply voltage of the comparator, and a "low" value, for example, corresponds to a negative supply voltage of the comparator.

[0187] As will be apparent to those skilled in the art, one or both of the comparators can also be connected separately to the current sensor output or the sensing rectifier output in different ways, such that their output signals are inverted. In such a case, the logic circuit is thus adapted to deliver appropriate control signals to the rectifier switch.

[0188] In summary, it should be noted that the present invention enables the creation of wireless power transmission devices with enhanced synchronous rectifier control, resulting in fewer switching errors and reduced losses, and thus a reduced number of components, since some modules such as the power transmission controller and the synchronous rectifier controller utilize common components such as sensing rectifiers.

Claims

1. A wireless power transmission device (1) for wireless power transmission from a primary side (2) across an air gap (8) to a secondary side (3) via inductive coupling, wherein a) The primary side (2) includes a power input for receiving input power (4), an input stage (5) for converting input power (4) into primary AC power (7), and a primary resonator (6) for receiving primary AC power (7) and inducing a magnetic field (9). b) The secondary side (3) includes a secondary resonator (10) for converting the power received through the magnetic field (9) into secondary AC power (12), and an output stage (11) for converting the secondary AC power (12) into DC output power (13). c) The output stage (11) includes a controllable rectifier (67) for converting secondary AC power (12) into DC output power (13). d) Wireless power transmission device (1) includes - Current sensing device (18), which is adapted to generate a current sensing signal, - A power transfer controller (15) adapted to control wireless power transfer based on current sensing signals, and - Control device (20) for controlling the controllable rectifier (67), Its features are: The current sensing device (18) includes a current sensing device adapted to generate a current sensing signal by sensing an AC current flowing from the secondary resonator (10) to the output stage (11), and the control device (20) is adapted to control a controllable rectifier (67) based on the current sensing signal, wherein the current sensing device (118) includes a first-stage current sensing device (101) and a second-stage current sensing device (102) linked to the output of the first-stage current sensing device (101). The first-stage current sensing device includes a first current converter having a first conversion ratio between 10:1 and 80:1, and the second-stage current sensing device includes a second current converter (122) having a second conversion ratio between 20:1 and 600:1, wherein the first and second conversion ratios are selected such that the current sensing device has a total conversion ratio between 100:1 and 30000:

1. The first current converter includes a magnetic core and a secondary winding (156), wherein the magnetic core includes two rods (155.1, 155.2) of a material with high permeability, the two rods (155.1, 155.2) being arranged in parallel and on different sides of a conductor (153) carrying AC current flowing from the secondary resonator to the output stage, such that the conductor (153) forms the primary winding of the first current converter, and wherein the secondary winding (156) includes a first winding portion (156.1) wound on the first rod (155.1) and a second winding portion (156.2) wound on the second rod (155.2) and connected to the first winding portion (156.1).

2. The wireless power transmission device according to claim 1, wherein the control device comprises: The first comparator (174) is used to sense the level of the current sensing signal; The second comparator is used to sense the direction of the current sensing signal; And logic circuitry adapted to combine the outputs of the first comparator (174) and the second comparator to provide one or more control signals (177) for controlling the controllable rectifier.

3. The wireless power transmission device according to claim 2, wherein the current sensing device includes a sensing rectifier for rectifying the current sensing signal, wherein a first comparator (174) is connected across a shunt, the shunt is connected across the output of the sensing rectifier, and wherein a second comparator is connected across the input of the sensing rectifier.

4. The wireless power transmission device according to claim 2, wherein the controllable rectifier (67) includes a plurality of controllable switches (71), and wherein logic circuitry is adapted to provide a first control signal (188.1) for a first subset of the switches (71) of the controllable rectifier and a second control signal (188.2) for a second subset of the switches (71) of the controllable rectifier.

5. The wireless power transmission device of claim 2, wherein the first comparator is adapted to provide a low signal if the AC current flowing from the secondary resonator to the output stage is high, and is adapted to provide a high signal if the AC current flowing from the secondary resonator to the output stage is low.

6. The wireless power transmission device according to claim 2, wherein, The second comparator is adapted to provide a high signal if the AC current flowing from the secondary resonator to the output stage is positive, and is adapted to provide a low signal if the AC current flowing from the secondary resonator to the output stage is negative.

7. The wireless power transmission device according to claim 2, wherein, The logic circuit is adapted to provide a first control signal (188.1) to turn on a first subset of switches and turn off a second subset of switches if the AC current flowing from the secondary resonator to the output stage is positive and above a threshold; to provide a second control signal (188.2) to turn on the second subset of switches and turn off the first subset of switches if the AC current flowing from the secondary resonator to the output stage is negative and above a threshold; and to provide a first control signal and a second control signal to otherwise turn off the first subset of switches and the second subset of switches.

8. The wireless power transmission device according to claim 1, wherein the current sensing device includes an averaging device connected to the current sensing device for generating an average value (187) of the current sensing signal, and wherein the power transmission controller is adapted to control the wireless power transmission based on the average value (187).

9. The wireless power transmission device according to claim 8, wherein the averaging device includes an averaging rectifier (181) for rectifying the current sensing signal and an averaging filter (182) connected to the output of the sensing rectifier, wherein an average value (187) is provided at the output of the averaging filter (182).

10. The wireless power transmission device according to claim 1, wherein the first conversion ratio is between 15:1 and 50:

1.

11. The wireless power transmission device according to claim 10, wherein the first conversion ratio is between 20:1 and 30:

1.

12. The wireless power transmission device according to claim 1, wherein the second conversion ratio is between 100:1 and 300:

1.

13. The wireless power transmission device according to claim 12, wherein the second conversion ratio is between 150:1 and 250:

1.

14. The wireless power transmission device according to claim 1, wherein the total conversion ratio is between 500:1 and 15000:

1.

15. The wireless power transmission device according to claim 14, wherein the total conversion ratio is between 2000:1 and 10000:

1.

16. The wireless power transmission device according to claim 1, wherein the material having high magnetic permeability is ferrite.

17. The wireless power transmission device according to claim 1, wherein the conductor (153) comprises a foil conductor.

18. A secondary side for a wireless power transmission device according to any one of claims 1 to 17, wherein, Secondary side includes - A current sensing device adapted to generate a current sensing signal. - A power delivery controller adapted to control wireless power delivery based on current sensing signals, and - Control device for controlling the controllable rectifier. The current sensing device includes a current sensing device adapted to generate a current sensing signal by sensing the AC current flowing from the secondary resonator to the output stage, and the control device is adapted to control the controllable rectifier based on the current sensing signal.

19. A current sensing device for a wireless power transmission device according to any one of claims 1 to 17, adapted to sense AC current flowing from the secondary resonator of the wireless power transmission device to the output stage of the wireless power transmission device.

20. A method for wireless power transfer from a primary side (2) across an air gap (8) to a secondary side (3) via inductive coupling, comprising: a) The input stage (5) converts the input power (4) received at the power input on the primary side into primary AC power (7), and the primary AC power (7) is received and a magnetic field (9) is induced using the primary resonator (6). b) The power received through the magnetic field (9) is converted into secondary AC power (12) using a secondary resonator (10), and the secondary AC power (12) is converted into DC output power (13) using an output stage (11) with a controllable rectifier. c) A current sensing signal is generated using a current sensing device (18), and a power delivery controller is used to control power delivery based on the current sensing signal. d) Use control device (20) to control the controllable rectifier. Its features The following steps are required: e) A current sensing signal is generated by sensing the AC current (12) flowing from the secondary resonator (10) to the output stage (11) using the current sensing device of the current sensing device (18), and f) Controlling the controllable rectifier based on current sensing signals. The current sensing device (118) includes a first-stage current sensing device (101) and a second-stage current sensing device (102) connected to the output of the first-stage current sensing device (101). The first-stage current sensing device includes a first current converter having a first conversion ratio between 10:1 and 80:1, and the second-stage current sensing device includes a second current converter (122) having a second conversion ratio between 20:1 and 600:1, wherein the first and second conversion ratios are selected such that the current sensing device has a total conversion ratio between 100:1 and 30000:

1. The first current converter includes a magnetic core and a secondary winding (156), wherein the magnetic core includes two rods (155.1, 155.2) of a material with high permeability, the two rods (155.1, 155.2) being arranged in parallel and on different sides of a conductor (153) carrying AC current flowing from the secondary resonator to the output stage, such that the conductor (153) forms the primary winding of the first current converter, and wherein the secondary winding (156) includes a first winding portion (156.1) wound on the first rod (155.1) and a second winding portion (156.2) wound on the second rod (155.2) and connected to the first winding portion (156.1).

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