DEVICE AND SYSTEM FOR WIRELESS POWER TRANSMISSION

Abstract

The invention relates to a wireless power transfer (WPT) device configured for installation in an electric vehicle for charging the vehicle's traction battery. The WPT device comprises a WPT receiver coil, a rectifier, and at least two safety switching units connected in parallel to the rectifier switching units of the full-bridge rectifier. A control unit controls the at least two safety switching units such that they are open during a charging process of the WPT device and closed at least during the activation of the WPT receiver coil and / or in the event of damage to or malfunction of the WPT device or any of its components.

Description

[0001] The present invention relates to a wireless power transfer device (WPT device) and a WPT system.

[0002] Wireless power transfer (WPT) using magnetic resonance is the technology that could free people from cumbersome cables. In fact, WPT adopts the same fundamental theory that has been developed over at least 30 years under the concept of inductive power transfer. WPT technology has advanced rapidly in recent years. At kilowatt power levels, the transmission distance increases from a few millimeters to several hundred millimeters, with a grid load efficiency exceeding 90%. These advancements make WPT highly attractive for electric vehicle (EV) charging applications in both stationary and dynamic charging scenarios. The adoption of WPT in EVs can easily reduce the barriers to charging time, range, and cost, and battery technology is not as critical in the EV market.

[0003] In power conversion, alternating current (AC) is conventionally rectified and smoothed to obtain a fixed voltage at a fixed frequency when AC is converted to low-voltage direct current (DC) or from one frequency to another. Once this is achieved, the power is passed to an inverter to obtain the final output with variable voltage and variable frequency.

[0004] EP 3 694 079 A1 discloses a WPT system for an electric vehicle (EV), wherein the WPT system comprises a ground assembly (GA) with a transmitting coil and a vehicle assembly (VA) with a receiver coil magnetically coupled to the GA transmitting coil to enable inductive power transfer from the GA to the VA and thus charge a traction battery of the EV.

[0005] The VA, which is a WPT device, includes a rectifier to convert the AC electrical power coupled into its receiver coil into DC electrical power, typically implemented as a full-bridge rectifier. Malfunctions or failures can occur in the VA or GA, which can lead to damage to the VA or GA's electronics.

[0006] One object of the present invention is to provide a safety mechanism to prevent such damage, in particular to the VA.

[0007] In a first aspect of the present invention, a WPT device is presented which is configured for installation in an electric vehicle for charging a traction battery of the electric vehicle, wherein the WPT device comprises: a WPT receiver coil configured to inductively receive alternating current electrical power from a WPT transmitter coil; a rectifier configured to convert alternating current electrical power into direct current electrical power, the rectifier comprising: - a pair of input terminals configured to receive alternating current electrical power; - a pair of output terminals configured to output DC electrical power; - four rectifier switching units forming a full-bridge rectifier; and - at least two safety switching units, wherein a first safety switching unit is coupled in parallel to a first rectifier switching unit of the full-bridge rectifier, which is coupled between a first input terminal and a first output terminal, and a second safety switching unit is coupled in parallel to a third rectifier switching unit of the full-bridge rectifier, which is coupled between a second input terminal and the first output terminal; and a control unit configured to control at least two safety switching units such that they are open during a charging process of the WPT device and closed at least during the switching on of the WPT receiver coil and / or in the event of damage or malfunction of the WPT device or any of its elements.

[0008] In another aspect of the present invention, a WPT system is presented comprising a WPT device as described herein and a traction battery coupled to the WPT device.

[0009] Preferred embodiments of the invention are defined in the dependent claims. It is understood that the claimed WPT system has similar and / or identical preferred embodiments to the claimed WPT device, in particular as defined in the dependent claims and as disclosed herein.

[0010] The present invention is based on the idea of ​​using additional safety switching units, at least within the rectifier of the WPT device configured for operation as a VA (voltage output) device, and controlling these additional safety switching units in such a way that the WPT receiver coil is short-circuited in the event of a malfunction in the WPT device or even in a second WPT device configured for operation as a GA (general output). During a charging process, the additional safety switching units in the rectifier are controlled to be open, so that they do not affect the desired (normal) operation of the rectifier.

[0011] In this context, it should be noted that the term "safety switching unit" is to be understood in the broadest sense as an additional switching unit provided in addition to the "rectifier switching units" and intended to contribute to the desired safety of the operation of the WPT device; that is, the terms "safety" in the expression "safety switching unit" and "rectifier" in the expression "rectifier switching unit" are therefore mainly used to distinguish the two different types of switching units, and not to restrict them to a specific type of switching unit.

[0012] In a preferred embodiment, the first and second safety switching units are normally closed. This ensures their desired function of always short-circuiting the WPT receiver coil except during a charging process. Alternatively or additionally, in one embodiment, the control unit for controlling the at least two safety switching units can be configured such that they are open only during the charging process of the WPT device and closed at all other times.

[0013] In another embodiment, the WPT device further comprises a third safety switching unit coupled to the second output terminal of the rectifier, wherein the control unit for controlling the third safety switching unit is configured to be closed during charging of the WPT device and open at least during the power-up of the WPT receiver coil and / or in the event of damage to or malfunction of the WPT device or any of its components. The addition of the third safety switching unit provides an additional safety mechanism to protect the traction battery and other electronics of the WPT device.It is closed during charging, but open at other times to prevent unwanted and potentially harmful current flow to the traction battery or other electronics while the WPT receiver coil is switched on, or if there is damage or malfunction to the WPT device or the second WPT device.

[0014] The WPT device may further comprise: a capacitor and / or a filter unit coupled to the rectifier output terminals; battery terminals at the output of the capacitor or filter unit configured to couple the traction battery to the WPT device; and a fourth safety switching unit coupled to a first battery terminal, and / or a fifth safety switching unit coupled to a second battery terminal, the control unit for controlling the fourth and / or fifth safety switching units configured to be closed during charging of the WPT device and open at least during the power-up of the WPT receiver coil and / or in the event of damage to or malfunction of the WPT device or any of its components. The fourth and fifth switching units provide additional safety to protect the traction battery.

[0015] Preferably, the third, fourth, and fifth safety switching units are normally open. This ensures their intended function of preventing current flow into the traction battery except during charging. Alternatively or additionally, the control unit for the third, fourth, and fifth safety switching units can be configured such that they are closed only during the charging process of the WPT device and open at all other times.

[0016] The fourth and fifth safety switching units can be part of the WPT device. In another embodiment, they can be part of the traction battery or the EV and not part of the WPT device. Even in such an embodiment, the control unit of the WPT device can be configured to provide a control signal to control one or more safety switching units coupled to one or more input terminals of the traction battery, so that they are closed during charging of the WPT device and open at least during the power-up of the WPT receiver coil and / or in the event of damage to or malfunction of the WPT device or any of its components.

[0017] In one embodiment, the control unit for the safety switching units is configured such that they change their state simultaneously. In another embodiment, they can be configured to change their state independently, which provides greater control flexibility and can offer increased safety, for example, if one or more switching units malfunction.

[0018] The WPT device may further include detection means configured to detect one or more of: - whether there is damage in the first and / or third rectifier switching unit, - whether no or insufficient AC electrical power is available at the first and / or third rectifier switching unit, in particular whether the voltage at one or more of the rectifier switching units is insufficient to switch them on, - whether there is a malfunction in the WPT device or in a second WPT device comprising a WPT transmitter coil configured to inductively couple AC electrical power into the WPT receiver coil of the WPT device, and - whether there is an overvoltage in a capacitor coupled between the output terminals of the rectifier.

[0019] Another possible malfunction could be, for example, overheating.

[0020] The detection means may include an electronic circuit arrangement configured to measure an output voltage of the WPT device and / or rectifier and / or to detect a malfunction in the WPT device, particularly the rectifier. A malfunction or damage to the WPT device (the VA) can be transmitted to the second WPT device (GA) so that the second WPT device can use this information. The VA can detect a malfunction on the VA side or indirectly on the GA side. In such a situation, the VA can send appropriate information, such as a warning or error message, to the GA. Once the GA receives this information, it can stop power transmission, while the VA can enter a safe state.

[0021] There are different ways to implement the various switching units. In one embodiment, the rectifier switching units are semiconductor switches. In another embodiment, the safety switching units are relay units, in particular electromagnetically controlled switches.

[0022] The WPT system according to the present invention comprises at least one WPT device as disclosed herein and a traction battery coupled to the WPT device. In one embodiment, the WPT system may further comprise a second WPT device (a GA) comprising a WPT transmitter coil configured for inductively coupling alternating current electrical power into the WPT receiver coil of the WPT device (the VA).

[0023] The preceding paragraphs were provided for general introduction only and are not intended to limit the scope of protection of the following claims. A more comprehensive understanding of the disclosure and many of its associated advantages is readily achieved by referring to the following detailed description in conjunction with the accompanying drawings, whereby: Fig. Figure 1 shows a schematic representation of the general structure of a WPT system for an EV. Fig. Figure 2 shows a circuit diagram of the typical circuit arrangement of a WPT device. Fig. Figure 3 shows a circuit diagram of the typical circuit arrangement of a WPT device, including active protection devices. Fig. Figure 4 shows a diagram of the drain current versus the drain-source voltage of a MOSFET. Fig. Figure 5 shows a circuit diagram of a first embodiment of a WPT device according to the present invention. Fig. Figure 6 shows a circuit diagram of a second embodiment of a WPT device according to the present invention in a safe state. Fig. Figure 7 shows the circuit diagram of the second embodiment of a WPT device according to the present invention in a normal operating state. Fig. Figure 8 shows a circuit diagram of a third embodiment of a WPT device according to the present invention. Fig. Figure 9 shows a flowchart of the different states for the second embodiment of the in Fig. 6 and Fig. 7 WPT device shown. Fig. Figure 10 shows a circuit diagram of a fourth embodiment of a WPT device according to the present invention.

[0024] Fig. Figure 1 shows a schematic representation of a generally known WPT system 100 for an EV 120, as disclosed, for example, in EP 3694079 A1. In this WPT system 100, the basic functional blocks for inductive charging are shared by a ground assembly (GA) 101 and a vehicle assembly (VA) 102, each of which represents a separate WPT device of the WPT system 100. The WPT system 100 comprises an inductive charging coil arrangement 112, which includes a transmitter coil (also called transmit coil or GA coil) 107 located on the GA side and a receiver coil (also called receive coil or VA coil) 108 located on the vehicle side.

[0025] The GA 101 of the WPT system 100 comprises a DC / AC converter 104 with power factor correction (PFC), which converts the single- or three-phase power source 103 into a regulated DC power source. The GA 101 further comprises a DC-to-RF (high frequency) AC converter 105, which generates a square wave voltage with a nearly constant frequency and constant duty cycle. A primary compensation circuit 106, which is a passive circuit network, compensates for the inductance of the transmitter coil to reduce the amount of reactive power supplied by the DC-to-RF AC converter 105. The transmitter coil 107 transmits power through a magnetic field and adds isolation between the AC input and the vehicle's HV battery 111.

[0026] The VA 102 comprises a receiver coil 108, which absorbs power via the magnetic field and provides isolation between the AC input and the vehicle's HV battery 111. A secondary compensation circuit 109, a passive circuit network, compensates for the receiver coil's inductance to maximize the transferred power at electrical resonance. The VA 102 includes an (active or passive) AC / DC rectifier 110, which converts high-frequency AC to DC to charge the vehicle's HV battery. A DC / DC battery charging device (which may or may not include battery charging algorithms / strategies) can be provided. Finally, the VA 102 includes the high-voltage battery 111 (also called the traction battery).

[0027] The architecture of the VA can vary depending on many criteria, including grid compensation or charging / discharging strategy. Charging the high-voltage battery 111 can potentially be handled by both assemblies, the GA 101 and the VA 102 of the WPT system 100, with this design potentially determining an optimal WPT architecture.

[0028] Fig. Figure 2 shows a circuit diagram of the typical circuit arrangement of a WPT device 200, which is used for operation as a VA, e.g. as the VA 102 of the in Fig. The WPT system shown in Figure 1 is configured as follows: The receiving coil 201 and the passive electronics 202, which mainly function as a compensation circuit arrangement, maximize the received transmission power of the VA 200. A rectifier 203, implemented as a full bridge 203 and formed from switches (hereinafter also referred to as rectifier switches), e.g., the MOSFETs Q1, Q2, Q3, Q4, can rectify the received transmitted power from the GA and thus increase the efficiency of the WPT system. A DC coupling capacitor 204 and passive electronics 205, such as an electromagnetic interference (EMI) filter, are coupled between the full bridge 203 and the battery 206.

[0029] Assuming that both WPT devices (GA and VA) are powered separately, safety mechanisms (SM) should be provided to protect GA and VA in case of a fault. Fig. Figure 3 shows a circuit diagram of a WPT 300 configured for operation as a VA and includes means for active protection. Both rectifier switches Q1 and Q3 are fully enabled, while switches Q2 and Q4 remain fully disabled (fault state). This state protects all electronics in the event of a fault (e.g., battery disconnection). This state can also be used during WPT system startup to prevent uncontrolled power transfer to the battery until the WPT system has stabilized.

[0030] Due to a possible malfunction in the GA and / or a fault in the VA, the voltage to control MOSFETs Q1-Q4 may be insufficient (less than 10-15 volts), and therefore MOSFETs Q1 and Q3 may not be activated at their lowest conduction resistance (RDSON), i.e., the nominal value of the MOSFET when fully turned on. This can occur with these MOSFETs due to their high power dissipation (IDS(on)). rms 2 *RDSON) can lead to a fatal temperature increase, as the resistance increases and the electronics can be destroyed as a result. Fig. Figure 4 shows a graph of the drain current (IDS) versus the drain-source voltage (VDS) of a MOSFET for different VGS (gate-to-source) voltages. It is evident that a lower VGS voltage across the MOSFET leads to an increase in power dissipation and a shift from the linear region to the saturation region, where higher conduction losses are to be expected. While IGBT (bipolar junction transistor) and BJT (bipolar junction transistor) transistors can be used instead of MOSFETs, MOSFET transistors may be more suitable for this type of application.

[0031] The above described and in Fig. 2 and Fig. The three known circuit arrangements shown therefore have the following disadvantages. There is no protection against damage; that is, the power amplifier (GA) continues to perform power transfer while the voltage amplifier (VA) cannot ensure correct control of the rectifier MOSFETs, in particular MOSFETs Q1 and Q3. Protection may be required in various scenarios, including a load shedding event, damaged electronics, etc. The present invention therefore aims to increase the safety of the entire electronics assembly.

[0032] Fig. Figure 5 shows a circuit diagram of a first embodiment of a WPT device 400 according to the present invention, which is suitable for operation as a VA, e.g. the VA 102 of the in Fig. The WPT system shown in section 1 is configured. In addition to the elements shown in Fig. In the circuit arrangement shown in Figure 3, the WPT device 400 provides means that, during a malfunction or during the start-up of the VA, an additional safety state is achieved by means of two safety switching units S1, S2, e.g., two relay units (such as electromagnetically controlled switches or a single electromagnetically controlled relay). The embodiment of the WPT device 400 comprises a receiving coil 401, passive electronics 402, a rectifier 403, an intermediate circuit capacitor 404, and passive electronics 405 to which the battery 406 is connected.

[0033] The rectifier 403 comprises a pair of input terminals 403a, 403b configured to receive AC electrical power from the compensation unit 402, a pair of output terminals 403c, 403d configured to output DC electrical power to the intermediate circuit capacitor 404, four rectifier switching units Q1, Q2, Q3, Q4 forming a full-bridge rectifier, and at least two safety switching units S1, S2. The first safety switching unit S1 is connected in parallel to a first rectifier switching unit, in which in Fig. The second safety switching unit S2 is connected in parallel to a third rectifier switching unit, in which in Fig. 5 shown embodiment of the rectifier switching unit Q3, which is coupled between a second input terminal 403b and the first output terminal 403d.

[0034] A control unit 407 is provided, which is configured to control the at least two safety switching units S1, S2 such that they are open during a charging process of the WPT device 400 and closed at least during the switching on of the WPT receiver coil 401 and / or in the event of damage or malfunction of the WPT device 401 or one of its elements, or optionally in the event of damage or malfunction of another WPT device configured for operation as a GA. Preferably, the control unit 407 is also configured to control the rectifier switching units Q1-Q4. The control can be such that the two safety switching units S1, S2 are controlled simultaneously or individually. Similarly, the rectifier switching units Q1-Q4 can be controlled simultaneously or individually.Preferably the safety switching units S1, S2 and the rectifier switching units Q1-Q4 are controlled simultaneously, but can also be controlled individually.

[0035] The safety switching units S1, S2 can normally be closed-circuit relay units short-circuited in parallel with the low-side MOSFETs Q1, Q3. In another embodiment, the safety switching units S1, S2 can be arranged in parallel with the high-side MOSFETs Q2, Q4. The safety switching units S1, S2 can be implemented by a single relay having two operating contact terminals. Fig. Figure 6 shows a circuit diagram of a second embodiment of a WPT device 500 according to the present invention. In this embodiment, a third safety switching unit S3, e.g., a third relay unit, is provided, which is coupled to the second output terminal 403c of the rectifier 403, in particular between the second output terminal 403c and the positive input terminal 406a of the battery 406 or, as shown in Figure 6, ... Fig. Figure 6 shows an input terminal 405a of the EMI filter 405. The control unit 407 is configured to control the third safety switching unit S3 such that it is closed during a charging process of the WPT device and open at least during the switching on of the WPT receiver coil 401 and / or in the event of damage to or malfunction of the WPT device 400 or one of its elements, or optionally in the event of damage to or malfunction of another WPT device configured for operation as a GA. In one embodiment, the third safety switching unit S3 can be part of a single relay having three pairs of operating contact terminals representing the three safety switching units S1, S2, S3, i.e., two operating contact terminals per safety switching unit.This third safety switching unit S3, which can be implemented as a normally open relay unit, provides additional protection by preventing a cross-circuit via Q2 and S1 (or Q4 and S2).

[0036] Fig. Figure 6 shows the circuit arrangement, in particular the state of the rectifier switching units Q1-Q4 and the safety switching units S1-S3, in a safety state of the WPT device 500, in which a high current flow through the rectifier switching units Q1 and Q3 is prevented and the WPT receiver coil 401 is short-circuited. Fig. Figure 7 shows essentially the same circuit arrangement as Fig. 6, however, in a normal operating state in which the rectifier switching units Q1-Q4 and the safety switching units S1-S3 are in a different switching state (S1 and S2 remain open while S3 is closed), so that the charging process takes place and is not affected by the state of the safety switching units S1-S3. It should be noted that in Fig. 6. The switching units S1-S3 and Q1-Q4 are represented as switches to make it easier to visually recognize that they are statically switched on (RSON statically fully switched on), while in Fig. 7 are represented as MOSFETs because they are no longer statically switched. No commutation pattern is applied in the rectifier at all; that is, when S1 and S2 are closed, the active rectifier switches Q1 and Q3 on in parallel while switching Q2 and Q4 off.

[0037] Fig. Figure 8 shows a circuit diagram of a third embodiment of a WPT device 600 according to the present invention, configured for operation as a VA. In this embodiment, the safety switching unit S3 is not used, but additional safety switching units S4 and S5 are coupled between the rectifier 403 and the battery 406, in this exemplary implementation between the output terminals 405c, 405d (also called battery terminals) of the EMI filter 405 and the input terminals 406a, 406b of the battery 406.The safety switching units S4 and S5, which can be implemented as normally open relay units, are controlled to be closed during the charging process of the WPT device 600 and open at least during the activation of the WPT receiver coil 401 and / or in the event of damage to or malfunction of the WPT device 600 or one of its components, or optionally in the event of damage to or malfunction of another WPT device configured for operation as a GA. The safety switching units S4 and S5 can be part of the WPT device 600 or part of the EV, i.e., located outside the WPT device.If the safety switching units S4 and S5 are part of the EV, they can be controlled either directly by the vehicle electronics or by the WPT device 600, depending on the vehicle configuration, in which case the control unit 407 can be configured to provide a control signal to control the safety switching units S4 and S5.

[0038] In one embodiment, the control unit 407 is configured to control the safety switching units S1 and S2 such that they are open only during the charging process of the WPT device and closed at all other times. It is also configured to control the third, fourth, and fifth safety switching units S3, S4, and S5 such that they are closed only during the charging process of the WPT device and open at all other times. The safety switching units S1-S5 can be controlled to change their state simultaneously or independently.

[0039] Fig. Figure 9 shows a flowchart of 700 of the different states for the second embodiment of the in Fig. 6 and Fig. Figure 7 shows the WPT device 500. Embedded software can be used to execute these steps to control the various switching units Q1-Q4 and S1-S3. When the WPT device is not performing a charging operation, it is in safety state 701, in which rectifier switching units Q1 and Q3 are 100% on, rectifier switching units Q2 and Q4 are 0% on (i.e., off), safety switching units S1 and S2 are closed, and safety switching unit S3 is open. In step 702, fault detection is performed to identify any malfunctions, (potential) damage, or other problems. If a fault is detected, the WPT device remains in safety state 701.If no fault is detected (and a charging process is to be carried out), the WPT device is returned to the normal state in which the rectifier switching units Q1-Q4 are modulated to rectify the supplied AC power, the safety switching units S1 and S2 are open and the safety switching unit S3 is closed.

[0040] In step 704, further fault detection is performed, which may be the same fault detection as in step 702, to detect any malfunctions, (potential) damage, or other problems. If no fault is detected, the WPT device remains in the normal state 703. If a fault is detected, the WPT device is placed in a fault state 705, in which the rectifier switching units Q1 and Q3 are 100% switched on, the rectifier switching units Q2 and Q4 are 0% switched on (i.e., switched off), the safety switching units S1 and S2 are still open, and the safety switching unit S3 is closed. Therefore, when fault state 705 is activated in this exemplary embodiment, S1-S3 are not yet in the safe state, as it is still possible to prevent damage to the system because Q1-Q4 can still be controlled correctly.

[0041] Error detection is performed in step 706 to determine whether the number of errors is below or above a predefined error threshold (in this example, "max_error"). If no further errors are detected in step 706, the WPT device returns to normal mode 704, allowing the loading process to continue. If another error is detected in step 706, the number of errors is compared to the error threshold in step 707. If the error threshold is exceeded, the WPT device enters safety state 701. Otherwise, error state 705 persists, and error detection step 706 is executed again.

[0042] The WPT can include one or more detection means for detecting one or more faults or problems. A circuit diagram of a corresponding embodiment of a WPT device 800 is shown in Fig. 10 shown. In this embodiment, in addition to the features shown in Fig. In the eight elements shown, a malfunction detector 801 is provided to detect a malfunction of one or more of the rectifier switching units Q1-Q4 based on measurements of voltage measuring elements D1-D4. Furthermore, an overvoltage detector 802 is provided, which may be provided in addition to or instead of the malfunction detector 801, to detect an overvoltage across the capacitor 404 based on a measurement of a voltage measuring element D5. Additional detection means may be provided in addition to or instead of the malfunction detector 801.

[0043] The detection means can generally be configured to detect: - whether there is damage in the first and / or third rectifier switching unit Q1, Q3, in particular the rectifier switching unit(s) to which the safety switching unit(s) S1, S2 is / are connected in parallel; - whether no or insufficient AC electrical power is available at the first and / or third rectifier switching unit Q1, Q3, in particular whether the voltage at one or more of the rectifier switching units is insufficient to switch them on; - whether a malfunction (e.g., overtemperature) exists in the WPT device (VA) or in a second WPT device (GA) comprising a WPT transmitting coil configured to inductively couple an AC electrical power into the WPT receiver coil of the WPT device; and - whether there is an overvoltage in a capacitor, e.g. the intermediate circuit capacitor optionally coupled between the output terminals of the rectifier.

[0044] The detection means comprise an electronic circuit arrangement configured to measure the output voltage of the WPT device and / or rectifier and / or to detect a malfunction in the WPT device, in particular the rectifier.

[0045] In summary, the present invention provides effective countermeasures against or in the event of malfunctions, ensuring that the WPT receiver coil remains short-circuited during a malfunction or other problem in the VA or GA. Furthermore, the additional safety features can also protect the battery during such an event by isolating the battery from the power stage, which has the advantage of reducing leakage current and protecting the battery in the event of damage to the power stage.

[0046] Providing the additional safety switching units S4 and S5 and controlling them independently of the safety switching units S1 and S2 can offer the advantage that, if S1 and S2 become blocked and can no longer be opened, the additional safety mechanism using S4 and S5 is useful.

[0047] Although the invention has been illustrated and described in detail in the drawings and the preceding description, these illustrations and descriptions are to be regarded as illustrative or exemplary and not as limiting; the invention is not limited to the embodiments described. Other variations of the disclosed embodiments can be understood and carried out by persons skilled in the art in practical application of the claimed invention by studying the drawings, the disclosure and the accompanying claims.

[0048] In the claims, the word "comprising" does not exclude any other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit can perform the functions of several elements mentioned in the claims. The mere fact that certain measures are listed in different dependent claims does not mean that a combination of these measures cannot be used advantageously.

[0049] Any reference numerals in the claims should not be interpreted as limiting the scope of protection. List of reference symbols 100 WPT system 101 Floor assembly (GA) 102 Vehicle assembly group (VA) 103 Power source 104 AC / DC converter 105 DC-to-RF AC converters 106 Primary compensation circuit 107 Transmitter coil 108 Receiver coil 109 Secondary compensation circuit 110 AC / DC rectifiers 111 High-voltage battery 112 Inductive charging coil arrangement 200 WPT device (as VA) 201 Receiving coil 202 Passive Electronics 203 Rectifier (full bridge) 204 Intermediate circuit capacitor 205 Passive Electronics (EMI Filter) 206 Battery 300 WPT device (as VA with active protection) 400 WPT device 401 Receiving coil 402 Passive Electronics 403 Rectifier 404 Intermediate circuit capacitor 405 Passive Electronics 406 Battery 407 Control unit 500 WPT device 600 WPT device 700 Flowchart 800 WPT device 801, 802 Identification devices Q1-Q4 rectifier switching units S1-S5 safety switching units QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 3 694 079 A1 [0004, 0024]

Claims

[1] Wireless power transfer (WPT) device configured for installation in an electric vehicle for charging a traction battery of the electric vehicle, the WPT device comprising: a WPT receiver coil (401) configured to inductively receive alternating current electrical power from a WPT transmitter coil; a rectifier (403) configured to convert alternating current electrical power into direct current electrical power, the rectifier comprising: - a pair of input terminals (403a, 403b) configured to receive alternating current electrical power; - a pair of output terminals (403c, 403d) configured to output DC electrical power; - four rectifier switching units (Q1, Q2, Q3, Q4) that form a full-bridge rectifier; and - at least two safety switching units (S1, S2), wherein a first safety switching unit is coupled in parallel to a first rectifier switching unit of the full-bridge rectifier, which is coupled between a first input terminal and a first output terminal, and a second safety switching unit is coupled in parallel to a third rectifier switching unit of the full-bridge rectifier, which is coupled between a second input terminal and the first output terminal; and a control unit (407) configured to control at least two safety switching units such that they are open during a charging process of the WPT device and closed at least during the switching on of the WPT receiver coil and / or in the event of damage or malfunction of the WPT device or any of its elements. [2] WPT device according to claim 1, wherein the first and second safety switching units (S1, S2) are normally closed safety switching units. [3] WPT device according to claim 1 or 2, wherein the control unit (407) for controlling the at least two safety switching units (S1, S2) is configured such that they are open only during the charging process of the WPT device and closed at all other times. [4] WPT device according to any of the preceding claims, furthermore, comprising a third safety switching unit (S3) which is coupled to the second output terminal of the rectifier, wherein the control unit (407) for controlling the third safety switching unit is configured such that it is closed during a charging process of the WPT device and is open at least during the switching on of the WPT receiver coil and / or in the event of damage or malfunction of the WPT device or any of its elements. [5] WPT device according to any of the preceding claims, further comprising: - a capacitor (404) and / or a filter unit (405) coupled to the output terminals of the rectifier; - Battery terminals (406a, 406b) at the output of the capacitor or filter unit configured to couple the traction battery to the WPT device; and - a fourth safety switching unit (S4) coupled to a first battery terminal and / or a fifth safety switching unit (S5) coupled to a second battery terminal, wherein the control unit (407) for controlling the fourth and / or fifth safety switching unit is configured such that they are closed during a charging process of the WPT device and are open at least during the switching on of the WPT receiver coil and / or in the event of damage or malfunction of the WPT device or any of its elements. [6] WPT device according to claim 4 and / or 5, wherein the third, fourth and fifth safety switching units (S3, S4, S5) are normally open safety switching units. [7] WPT device according to any one of claims 4 to 6, wherein the control unit (407) for controlling the third, fourth and fifth safety switching unit (S3, S4, S5) is configured such that they are closed only during the charging process of the WPT device and open at all other times. [8] WPT device according to any one of claims 1 to 4, wherein the control unit (407) is configured to provide a control signal to control one or more safety switching units (S4, S5) coupled to one or more input terminals of the traction battery, such that they are closed during a charging process of the WPT device and open at least during the switching on of the WPT receiver coil and / or in the event of damage or malfunction of the WPT device or one of its elements. [9] WPT device according to one of the preceding claims, wherein the control unit (407) for controlling the safety switching units (S1-S5) is configured such that they change their state simultaneously or independently. [10] WPT device according to any of the preceding claims, further comprising detection means (801, 802) configured to detect one or more of: - whether there is damage in the first and / or third rectifier switching unit, - whether no or insufficient AC electrical power is available at the first and / or third rectifier switching unit, in particular whether the voltage at one or more of the rectifier switching units is insufficient to switch them on, - whether there is a malfunction in the WPT device or in a second WPT device comprising a WPT transmitter coil configured to inductively couple AC electrical power into the WPT receiver coil of the WPT device, and - whether there is an overvoltage in a capacitor coupled between the output terminals of the rectifier. [11] WPT device according to claim 10, wherein the detection means (801, 802) comprise an electronic circuit arrangement configured to measure the output voltage of the WPT device and / or the rectifier and / or to detect a malfunction in the WPT device, in particular the rectifier. [12] WPT device according to one of the preceding claims, wherein the rectifier switching units (Q1, Q2, Q3, Q4) are semiconductor switches and / or the safety switching units are relay units, in particular electromagnetically controlled switches. [13] WPT system comprising a WPT device (101, 400) according to one of the preceding claims and a traction battery (111, 406) coupled to the WPT device. [14] WPT system according to claim 13, further comprising a second WPT device (101) comprising a WPT transmitter coil (107) configured to inductively couple an alternating current electrical power into the WPT receiver coil (108; 401) of the WPT device according to any one of claims 1 to 12.

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