Wireless charging device and method of operation

Abstract

According to a first aspect of the present disclosure, there is provided a wireless charging device including: a charging unit configured to charge an external device by wirelessly transmitting power to the external device; a detection unit configured to detect whether the external device is a passive near field communication (NFC) device or an active NFC device by analyzing a modulation characteristic of an NFC signal received by the external device; and a controller configured to control the charging unit according to an output of the detection unit, where the output indicates whether the external device is a passive NFC device or an active NFC device. According to a second aspect of the present disclosure, a corresponding method of operating a wireless charging device is conceived.

Description

Technical Field

[0001] The present disclosure relates to a wireless charging device and a corresponding method for operating the wireless charging device. Background Art

[0002] Near Field Communication (NFC) is a technology for close range communication established for various use cases. Using this technology, a primary device can generate a radio frequency (RF) field at a frequency of 13.56 MHz to power a secondary device. Modulation techniques are used to communicate in both directions. The secondary device can be a passive device (e.g., a tag or transponder) or an active, typically battery-powered device. The RF field generated by the NFC reader can be used to charge the battery of the secondary device. This process is called wireless charging. Some wireless charging devices can use a low frequency (LF) transmitter to charge the battery of the secondary device; an example of such a device is a so-called Qi charger. Qi is an open interface standard that defines wireless power transfer using inductive charging over a distance of up to 4 cm; this standard has been developed by the Wireless Power Consortium. Summary of the invention

[0003] According to a first aspect of the present disclosure, a wireless charging device is provided, comprising: a charging unit configured to charge an external device by wirelessly transmitting power to the external device; a detection unit configured to detect whether the external device is a passive near field communication (NFC) device or an active NFC device by analyzing a modulation characteristic of an NFC signal received by the external device; and a controller configured to control the charging unit according to an output of the detection unit, wherein the output indicates whether the external device is a passive NFC device or an active NFC device.

[0004] In one or more embodiments, the controller is further configured to prevent the charging unit from charging the external device if the detection unit has detected that the external device is a passive NFC device, or to reduce the amount of power transmitted by the charging unit if the detection unit has detected that the external device is a passive NFC device.

[0005] In one or more embodiments, the controller is further configured to permit the charging unit to charge the external device if the detection unit has detected that the external device is an active NFC device.

[0006] In one or more embodiments, the modulation characteristic indicates a modulation type applied to the NFC signal, and the modulation type is passive load modulation or active load modulation.

[0007] In one or more embodiments, the modulation characteristic is a minimum value of the NFC signal during a predefined time window.

[0008] In one or more embodiments, the detection unit is configured to detect that the external device is a passive NFC device if the minimum value of the NFC signal remains below a predefined threshold during the entire time window.

[0009] In one or more embodiments, the controller is further configured to maintain the charging unit in the charging mode by default.

[0010] In one or more embodiments, the charging unit includes a low frequency (LF) transmitter configured to transmit power to the external device.

[0011] According to a second aspect of the present disclosure, a method for operating a wireless charging device is contemplated, the method comprising: detecting, by a detection unit included in the wireless charging device, whether the external device is a passive near field communication (NFC) device or an active NFC device by analyzing a modulation characteristic of an NFC signal received by an external device; charging, by a charging unit included in the wireless charging device, the external device by wirelessly transmitting power to the external device; and controlling, by a controller included in the wireless charging device, the charging unit according to an output of the detection unit, wherein the output indicates whether the external device is a passive NFC device or an active NFC device.

[0012] In one or more embodiments, the controller permits the charging unit to charge the external device if the detection unit has detected that the external device is an active NFC device.

[0013] In one or more embodiments, the modulation characteristic indicates a modulation type applied to the NFC signal, and the modulation type is passive load modulation or active load modulation.

[0014] In one or more embodiments, the modulation characteristic is a minimum amplitude of the NFC signal during a predefined time window.

[0015] In one or more embodiments, the detection unit detects that the external device is a passive NFC device if the minimum amplitude of the NFC signal remains below a predefined threshold during the entire time window.

[0016] In one or more embodiments, the controller maintains the charging unit in the charging mode by default. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The embodiments will be described in detail with reference to the accompanying drawings.

[0018] Figure 1An example of a charging system is shown that includes a wireless charging device coupled to a device being charged.

[0019] Figure 2 An illustrative embodiment of a wireless charging device is shown.

[0020] Figure 3 An illustrative embodiment of a method of operating a wireless charging device is shown.

[0021] Figure 4 An illustrative embodiment of a communication system is shown.

[0022] Figure 5 An illustrative embodiment of an NFC front end is shown.

[0023] Figure 6 Another illustrative embodiment of a communication system is shown.

[0024] Figure 7 A graph showing the raw data of amplitude versus time is shown.

[0025] Figure 8 A graph showing moving minima of amplitude versus time is shown.

[0026] Fig. 9 Another illustrative embodiment of a method of operating a wireless charging device is shown. DETAILED DESCRIPTION

[0027] As mentioned above, Near Field Communication (NFC) is a technology for close-range communication established for various use cases. Using this technology, a primary device can generate a radio frequency (RF) field at a frequency of 13.56 MHz to power a secondary device. Modulation techniques are used to communicate in both directions. The secondary device can be a passive device (e.g., a tag or transponder) or an active, typically battery-powered device. The RF field generated by the NFC reader can be used to charge the battery of the secondary device. This process is called wireless charging. Some wireless charging devices can use a low frequency (LF) transmitter to charge the battery of the secondary device; an example of such a device is a so-called Qi charger. Qi is an open interface standard that defines wireless power transfer using inductive charging over a distance of up to 4 cm; this standard has been developed by the Wireless Power Consortium.

[0028] Figure 1An example of a charging system 100 is shown that includes a wireless charging device coupled to a device being charged. The wireless charging device is a low frequency (LF) transmitter device 102, such as a Qi charger, and the device being charged is a passive NFC device 104 inductively coupled to the LF transmitter device 102. The passive NFC device 104 may be, for example, a smart card that has been inadvertently brought into proximity with the LF transmitter device 102. More specifically, the LF transmitter device 102 is typically used to charge the battery of an active NFC device, such as a mobile phone. As used herein, the term "passive device" refers to a device that does not have an internal power source (e.g., a battery) and is powered by a field. It should be noted that a passive device may contain one or more small storage elements for temporarily storing energy extracted from the field.

[0029] Typically, a passive device is configured to perform passive load modulation. In contrast, the term "active device" refers to a device having an internal power source such as a battery. Typically, an active device is configured to perform active load modulation. Active load modulation can be defined as a type of modulation whereby the antenna current is provided by a driver amplifier circuit during modulation. This definition of active load modulation is given in the article "Active Load Modulation for Contactless Near-Field Communication" by Michael Gebhart et al. and published at the 2012 IEEE International Conference on RFID-Technology and Applications (RFID-TA) (DOI: 10.1109 / RFID-TA.2012.6404518). In contrast, passive load modulation can be defined as a type of modulation whereby the antenna current is not provided by a driver amplifier circuit.

[0030] Those skilled in the art will appreciate that the LF transmitter device 102 typically operates in a frequency range of about tens to hundreds of kHz, while the passive NFC device 104 typically operates at a frequency of 13.56 MHz. However, if the induced voltage becomes higher than the limiter voltage, the limiter 106 of the passive NFC device 104 will become active and short the NFC coil. As a result, a current of hundreds of milliamps up to several amps may be injected into the passive NFC device 104. This in turn may damage the passive NFC device 104 very quickly.

[0031] Discussion is now made of a wireless charging device and corresponding method of operating the wireless charging device that helps avoid damage to an external device, such as an external device that has been inadvertently brought into proximity with the wireless charging device.

[0032] Figure 2An illustrative embodiment of a wireless charging device 200 is shown. The wireless charging device 200 includes a charging unit 202, a detection unit 204, and a controller 206. The charging unit 202 is configured to charge an external device (not shown) by wirelessly transmitting power to the external device. In addition, the detection unit 204 is configured to detect whether the external device is a passive NFC device or an active NFC device by analyzing the modulation characteristics of the NFC signal received by the external device. Finally, the controller 206 is configured to control the charging unit 202 according to the output of the detection unit 204, wherein the output indicates whether the external device is a passive NFC device or an active NFC device. By controlling the charging unit 202 according to the output of the detection unit 204, specifically, the output indicating the analyzed modulation characteristics of the NFC signal received by the external device, the risk of damage to the external device can be reduced.

[0033] In one or more embodiments, the controller is further configured to prevent the charging unit from charging the external device if the detection unit has detected that the external device is a passive NFC device, or to reduce the amount of power transmitted by the charging unit if the detection unit has detected that the external device is a passive NFC device. This further helps to avoid damage to the external device because it can be ensured that excessive power is not transmitted to the passive NFC device. In one or more embodiments, the controller is further configured to permit the charging unit to charge the external device if the detection unit has detected that the external device is an active NFC device. In this way, the charging process can be started relatively quickly after it has been verified that the external device is unlikely to be damaged.

[0034] In one or more embodiments, the modulation characteristic indicates a modulation type applied to the NFC signal, and the modulation type is passive load modulation or active load modulation. By controlling the charging unit according to whether the modulation type applied by the external device is passive load modulation or active load modulation, the risk of causing damage to the external device can be easily reduced. For example, if the modulation type is passive load modulation, the external device is most likely a passive NFC device. In this case, charging of the external device can be prevented to avoid damaging the external device.

[0035] In one or more embodiments, the modulation characteristic is a minimum amplitude of the NFC signal during a predefined time window. The minimum amplitude of the NFC signal provides a suitable indication of whether the external device is a passive NFC device. In a practical implementation, the detection unit is configured to detect that the external device is a passive NFC device if the minimum amplitude of the NFC signal remains below a predefined threshold during the entire time window. In one or more embodiments, the controller is further configured to keep the charging unit in a charging mode by default. In this way, unnecessary switching to a different mode (i.e., a mode that prevents charging) can be avoided. In addition, in a practical implementation, the charging unit includes a LF transmitter configured to transmit power to the external device.

[0036] Figure 3 An illustrative embodiment of a method 300 for operating a wireless charging device is shown. The method 300 includes the following steps. At 302, a detection unit included in the wireless charging device detects whether the external device is a passive NFC device or an active NFC device by analyzing a modulation characteristic of an NFC signal received by an external device. In addition, at 304, a charging unit included in the wireless charging device charges the external device by wirelessly transmitting power to the external device. In addition, at 306, a controller included in the wireless charging device controls the charging unit according to an output of the detection unit, wherein the output indicates whether the external device is a passive NFC device or an active NFC device. As mentioned above, by controlling the charging unit according to the output of the detection unit, specifically, the output indicating the analyzed modulation characteristic of the NFC signal received by the external device, the risk of damage to the external device can be reduced.

[0037] According to the present disclosure, a passive NFC device (e.g., an NFC-enabled smart card or NFC tag) can be protected based on detecting the reverse link characteristics of a PICC to a PCD, specifically, by the modulation characteristics of an NFC signal sent by the PICC. Typically, an NFC system includes a reader device that generates a high-frequency radio field, sometimes referred to as a reader, interrogator, or proximity coupling device (PCD), and a passive or active communication counterpart. The communication counterpart may be, for example, a passive transponder or an active card emulation device that may be referred to as a proximity integrated circuit card (PICC) or a listener. The reader device transmits a radio frequency field that may power the communication counterpart. Modulation schemes and signal encoding are applied to communications between devices. Specific implementation examples are described in particular in the technical standards published by the NFC Forum and the technical standards ISO / IEC 14443, ISO / IEC 15693, ISO / IEC 18092.

[0038] It should be noted that passive devices typically apply different modulation types than active NFC devices, e.g., emulating a card. The PICC modulator signal may be measured as part of a receiver signal, which may then be post-processed to analyze which type of device (passive or active NFC) is used. For example, when a cell phone behaves like a card (e.g., a bank card), it may be very difficult to identify at the protocol level which type of device is present. By analyzing the NFC signals sent by the PICC as set forth above, a low-cost and simple solution may be implemented to overcome existing limitations and protect passive NFC devices in a less complex manner. For example, the presently disclosed apparatus and method may provide a simple and effective solution compared to solutions using complex decision matrices or algorithms.

[0039] Figure 4 An illustrative embodiment of a communication system 400 is shown. The communication system 400 includes a wireless charging device 402 and an NFC endpoint 410 (i.e., a PICC or a listener) configured to communicate with each other. To this end, the wireless charging device 404 includes an NFC reader 404 (i.e., a PCD or a poller) configured to establish NFC with the NFC endpoint 410. In addition, the wireless charging device 402 includes a low frequency transmitter device 406 configured to wirelessly charge the NFC endpoint 410. In addition, the wireless charging device 402 includes a microcontroller 408 configured to analyze an NFC signal received from the NFC endpoint 410 through the NFC reader 404. In addition, the microcontroller 408 can control the charging unit (i.e., the low frequency transmitter device 406) according to the result of the analysis performed on the NFC signal.

[0040] Figure 5 An illustrative embodiment of an NFC front end 500 is shown. The NFC front end 500 includes an automatic receiver voltage level (RCV) level control block 502, as well as a mixer 504 divided into an I channel and a Q channel, a baseband amplifier 506, and an analog / digital converter 508. In order to protect the passive NFC device from power generated, for example, by an LF transmitter, the modulation characteristics of the reverse link between the PICC and the PCD can be analyzed. More specifically, the reverse link (i.e., the NFC signal sent by the PICC) can be measured by the NFC front end 500, which can be integrated into the PCD. The measured raw data from the I channel and the Q channel can then be post-processed by the microcontroller to determine the modulation type used by the PICC.

[0041] Figure 6Another illustrative embodiment of a communication system 600 is shown. The communication system 600 includes a microcontroller 602 and an NFC front end 604 that may form part of a wireless charging device of the type set forth above. The wireless charging device is configured to establish near field communication with an external PICC 606. The microcontroller 602 and the NFC front end 604 are connected to each other via a serial peripheral interface (SPI). The microcontroller 602 is configured to analyze I data and Q data obtained from the NFC front end 604 based on an NFC signal received from the PICC 606. For example, the microcontroller 602 may calculate an amplitude characteristic of the reverse link.

[0042] Figure 7 and 8 A graph 700 showing raw data of amplitude versus time is shown, as well as a graph 800 showing a moving minimum of amplitude versus time. Specifically, example measurements for calculations of NFC signals sent by a phone (i.e., an active NFC device) and an NFC-A type card (i.e., a passive NFC device) are shown. It can be seen that the reverse link response from the mobile phone has a higher minimum during the "low state" (i.e., valley) of the subcarriers than in the case of the card. Therefore, by performing a sliding window minimum determination, for example, with a window length of k, the response can be evaluated based on the minimum during the "low state" of the reverse link communication. By doing so, the processed response from the mobile phone will have a peak, and the processed response from the card will be fairly flat. Therefore, the processed response can be used to distinguish the mobile phone from the card.

[0043] For example, if Figure 7 If the minimum value (i.e., valley value) of the signal wave shown in remains below the predefined threshold value during the predefined time window, it can be inferred that the signal is sent by a passive NFC device such as a card. Otherwise, it can be inferred that the signal is sent by an active NFC device such as a mobile phone. It should be noted that the time window may cover the low state of the subcarrier to facilitate accurate distinction between passive and active NFC devices. Figure 8 A predefined threshold 806 is shown, as well as graphs 802, 804 representing the moving minimum values ​​(i.e., valley values) of the signal waves of the mobile phone and the card, respectively. In this way, passive NFC devices and active NFC devices can be easily distinguished. Alternatively, passive NFC devices and active NFC devices can be distinguished in the following manner. If the difference between the maximum value and the minimum value of the moving minimum value is less than the predefined threshold value, it can be inferred that the signal is sent by a passive NFC device. Otherwise, it can be inferred that the signal is sent by an active NFC device. This alternative implementation can achieve a more accurate determination of the type of NFC device.

[0044] Fig. 9Another illustrative embodiment of a method 900 for operating a wireless charging device is shown. Specifically, a flow chart is shown that depicts an NFC polling cycle that includes NFC device differentiation based on characteristics of reverse link modulation. First, an NFC scan 906 for the desired NFC technology is performed by the PCD. If no device is detected, the result is "charging allowed" 920 because no device is placed on the charger. If a device is detected via the NFC scan 906, a second request for the specific detected device is sent 910 by the PCD. The detected device will in turn respond to the second request after a specified time, and the NFC front-end device will capture the I data and Q data of the reverse link response and send the I data and Q data to the microcontroller for further processing. Next, the peak amplitude (A) based on the received I data and Q data can be calculated as shown in Equation 1 below. p ).

[0045]

[0046] The next step is to perform a sliding window minimum with a window length k of the calculated amplitude of the response 914. If the difference between the maximum and minimum of the moving minimum is less than a predefined threshold, the detected NFC device will be classified as a passive NFC device and the result will be "Charging is prohibited" 918. Otherwise, the detected NFC device will be classified as a mobile phone and the result will be "Charging is allowed" 920.

[0047] It should be noted that the above embodiments have been described with reference to different subject matters. Specifically, some embodiments may be described with reference to method-type claims, while other embodiments may be described with reference to apparatus-type claims. However, those skilled in the art should understand from the above that, unless otherwise indicated, any combination of features related to different subject matters, in addition to any combination of features belonging to one type of subject matter, in particular, a combination of features of a method-type claim with features of an apparatus-type claim, is also considered to be disclosed with this document.

[0048] In addition, it should be noted that the drawings are schematic. In different drawings, similar or identical elements are represented by the same reference numerals. In addition, it should be noted that in order to provide a concise description of the illustrative embodiments, the implementation details that belong to the customary practices of those skilled in the art may not be described. It should be understood that in the development of any such implementation, as in any engineering or design project, a large number of implementation-specific decisions must be made in order to achieve the specific goals of the developer, such as complying with system-related and business-related constraints, which may be different between different implementations. In addition, it should be understood that such development work may be complex and time-consuming, but it is nothing more than a routine task for those skilled in the art to design, manufacture and produce.

[0049] Finally, it should be noted that the skilled person should be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed in parentheses should not be construed as limiting the claims. The words "comprise(s)" or "comprising" do not exclude the presence of other elements or steps than those listed in the claim. The words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements. The measures recited in the claims may be implemented by means of hardware comprising several different elements and / or by means of a suitably programmed processor. In a device claim listing several components, several of these components may be embodied by the same item of hardware. The mere fact that certain measures are recited in different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0050] List of reference numerals:

[0051] 100 Charging System

[0052] 102 Low frequency transmitter device

[0053] 104 NFC passive device

[0054] 106 Limiter

[0055] 200 Wireless Charging Device

[0056] 202 Charging unit

[0057] 204 Detection Unit

[0058] 206 Controller

[0059] 300 Method of operating a wireless charging device

[0060] 302 A detection unit included in the wireless charging device detects whether the external device is a passive NFC device by analyzing the modulation characteristics of the NFC signal received by the external device.

[0061] 304 The charging unit included in the wireless charging device charges the external device by wirelessly transmitting power to the external device.

[0062] 306 A controller included in the wireless charging device controls the charging unit according to the output of the detection unit, wherein the output indicates whether the external device is a passive NFC device.

[0063] 400 Communication Systems

[0064] 402 Wireless Charging Device

[0065] 404NFC Reader (PCD / Poller)

[0066] 406 LF transmitter device

[0067] 408 Microcontroller

[0068] 410NFC endpoint (PICC / listener)

[0069] 500NFC front end

[0070] 502 Automatic RCV Level Control

[0071] 504 Mixer

[0072] 506 Baseband Amplifier

[0073] 508 A / D Converter

[0074] 600 Communication System

[0075] 602 Microcontroller

[0076] 604NFC front end 606PICC

[0077] 700 Amplitude vs. Time (raw data)

[0078] 702 Telephone Amplitude

[0079] 704 Card Amplitude 800 Amplitude vs. Time (Minimum Moving Value)

[0080] 802 Minimum amplitude for calls

[0081] Minimum amplitude for 804 cards

[0082] 806 Threshold

[0083] 900 Method of operating a wireless charging device

[0084] 902 Start

[0085] 904 Measure the received amplitude level during RF on 906 Scanning for NFC devices 908 Device detected?

[0086] 910 Send Request

[0087] 912 Capture received amplitude

[0088] 914 Execute Moving Minimum

[0089] 916 Amplitude < Threshold

[0090] 918 Charging is prohibited 920 Charging is allowed.

Claims

1. A wireless charging device, characterized in that: include: a charging unit configured to charge an external device by wirelessly transmitting power to the external device; a detection unit configured to detect whether the external device is a passive near field communication NFC device or an active NFC device by analyzing a modulation characteristic of an NFC signal received by the external device; A controller is configured to control the charging unit according to an output of the detection unit, wherein the output indicates whether the external device is a passive NFC device or an active NFC device.

2. The wireless charging device according to claim 1, characterized in that: The controller is additionally configured to prevent the charging unit from charging the external device if the detection unit has detected that the external device is a passive NFC device, or to reduce an amount of power transferred by the charging unit if the detection unit has detected that the external device is a passive NFC device.

3. The wireless charging device according to claim 1 or 2, characterized in that: The controller is additionally configured to permit the charging unit to charge the external device if the detection unit has detected that the external device is an active NFC device.

4. A wireless charging device according to any of the preceding claims, characterized in that The modulation characteristic indicates a type of modulation applied to the NFC signal, and wherein the modulation type is passive load modulation or active load modulation.

5. A wireless charging device according to any of the preceding claims, characterized in that The modulation characteristic is a minimum value of the NFC signal during a predefined time window.

6. The wireless charging device according to claim 5, characterized in that: The detection unit is configured to detect that the external device is a passive NFC device if the minimum value of the NFC signal remains below a predefined threshold during the entire time window.

7. A wireless charging device according to any of the preceding claims, characterized in that The controller is additionally configured to maintain the charging unit in a charging mode by default.

8. A wireless charging device according to any of the preceding claims, characterized in that The charging unit includes a low frequency (LF) transmitter configured to transmit power to the external device.

9. A method for operating a wireless charging device, characterized in that: include: The detection unit included in the wireless charging device detects whether the external device is a passive near field communication NFC device or an active NFC device by analyzing a modulation characteristic of an NFC signal received from the external device; charging the external device by wirelessly transmitting power to the external device by a charging unit included in the wireless charging device; The charging unit is controlled by a controller included in the wireless charging device according to an output of the detection unit, wherein the output indicates whether the external device is a passive NFC device or an active NFC device.

10. The method according to claim 9, characterized in that The controller prevents the charging unit from charging the external device if the detection unit has detected that the external device is a passive NFC device, or reduces an amount of power transferred by the charging unit if the detection unit has detected that the external device is a passive NFC device.

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