Mobile device with short circuit switch for handling wireless communication and wireless charging applications

Abstract

A mobile device (16) for implementing a wireless communication application with another device and for implementing an energy harvesting application to charge a battery (17) or to power a processing stage of the mobile device (16), both applications being based on a magnetic field having a particular carrier frequency in the HF band, the mobile device (16) comprising an integrated circuit (18) having a communication stage (19), the device comprises a modulator (20) and a demodulator (21), which are configured to realize load-modulated wireless communication with another device; and a harvesting stage (22) constructed for wireless energy harvesting for the mobile device (16), the harvesting stage (22) comprising a rectifier (23) for providing a rectified DC voltage (VDDC), the rectifier (23) being connected to a matching circuit (26) of the mobile device (16) via a first pin (27) and a second pin (28) of the integrated circuit (18), the matching circuit (26) being connected to an antenna (25) of the mobile device (16), wherein the communication stage (19) and the collection stage (22) are configured to handle the magnetic field at the same specific carrier frequency in both applications, and wherein the modulator (20) and the demodulator (21) are directly connected to the antenna (25) via a third pin (31) and a fourth pin (32) of the integrated circuit (18), and the integrated circuit (18) comprises a switch (33), the switch (33) is connected in parallel and directly to the rectifier (23) and directly to the first pin (27) and the second pin (28) of the integrated circuit (18), and wherein the switch (33) switches to its connected state, shorting the first pin (27) and the second pin (28) to enable wireless communication applications only with capacitors (29, 30) arranged in parallel with the antenna (25) in the matching circuit (26), and wherein the switch (33) switches to its open state to implement the charging application only with capacitors (29, 30) arranged in series with the antenna (25) in the matching circuit (26).

Description

TECHNICAL FIELD

[0001] The invention relates to a mobile device for implementing a wireless communication application with another device and for implementing an energy harvesting application for charging a battery or for powering a processing stage of the mobile device, both applications being based on a magnetic field having a specific carrier frequency within the HF frequency band, the mobile device comprising an integrated circuit having:

[0002] a communication stage comprising a modulator and a demodulator, the modulator and the demodulator being built for implementing a load-modulated wireless communication with another device, and

[0003] a harvesting stage built for wireless energy harvesting for the mobile device, the harvesting stage comprising a rectifier for providing a rectified DC voltage, the rectifier being connected via a first pin and a second pin of the integrated circuit to a matching unit of the mobile device, the matching unit being connected to an antenna of the mobile device. BACKGROUND

[0004] There are mobile devices on the market, such as the Samsung Galaxy Watch Active2 or the Samsung Galaxy Watch4 (SM-R870NZKKASIO) or Galaxy Fit SM-R370 device, which are smartwatches that can be worn on the wrist of a person. Mobile devices like these smartwatches comprise a communication stage implemented by a dedicated payment communication integrated circuit connected via a first antenna matching unit to a first antenna for communication at a frequency of 13.56 MHz. Most of these smartwatches have a poor performance in terms of communication range. Some of these smartwatches implement a payment application in compliance with the Near Field Communication standard ISO / IEC 18000-3 to be able to make payments on a point-of-sale card reader device. These smartwatches further comprise a charging stage implemented by a dedicated charging integrated circuit connected via a second antenna matching unit to a second antenna for charging a battery of the smartwatch with energy harvested from an electromagnetic or HF field at a frequency of 13.56 MHz or other HF field frequency, such as the typical frequency of 100 kHz to 300 kHz for Qi wireless charging. Some of these smartwatches implement a proprietary system of the smartwatch for wireless charging, while for other charging applications the NFC Forum provides a “Wireless Charging Technical Specification” based on the NFC standard. Some of these wireless charging applications further comprise a communication channel for communicating information related to the wireless charging. Those smartwatches using an antenna with an antenna matching unit, whose antenna is tuned for both energy harvesting applications and communication applications without any modification, have a poor performance in terms of communication range.

[0005] The wireless communication application and the wireless charging application of a smartwatch are different applications with completely different requirements for the wireless transmission and the HF field. For the communication application of a smartwatch with load modulation by a low field strength HF field, the input impedance of the communication stage of the first antenna in the HF field needs to have an impedance range of several thousand Ohms. For the wireless charging application, the mobile device needs to collect as much energy as possible from the HF field to charge the internal battery. To achieve this, the charging stage with its second antenna needs to have a very low impedance in the HF field and the second antenna needs to be tuned to the same resonant frequency as the carrier frequency of the magnetic field by a second matching circuit. For the different applications, these different impedances of the first antenna and the second antenna in the HF field, and in most applications also different resonant frequencies, define the requirements for different matching circuits of the first matching unit and the second matching unit to ensure that both the first antenna and the second antenna work optimally for the different applications.

[0006] For small devices like smartwatches, it is a considerable disadvantage to implement two different antennas and two different matching circuits in the limited volume available for a wristwatch. This increases the technical complexity and the cost of such mobile devices. In addition, the two antennas influence each other in the HF field, thus reducing the possible efficiency.

[0007] Figure 1 A prior art mobile phone 1 is disclosed, which comprises an integrated circuit 2 with a communication stage 3, which comprises a modulator 4 and a demodulator 5 to enable wireless communication with another NFC device based on the NFC standard. The mobile phone 1 further comprises a harvesting stage, which is implemented as a charging stage 6 with a rectifier 7 and a battery charger 8 for wireless charging of a battery 9 of the smartwatch 1. An antenna 10 is connected via a matching circuit 11 to a first pin 12 and a second pin 13 of the integrated circuit 2, wherein a first contact of the antenna 10 is connected via a first capacitor 14 of the matching circuit 11 to the first pin 12 and a second contact of the antenna 10 is connected via a second capacitor 15 of the matching circuit 11 to the second pin 13. This known concept of a smartwatch 1, which enables both NFC communication applications and NFC charging applications, has the disadvantage that the matching circuit 11 can only be optimized for one of the two applications. For high power charging above a power level of 0.75 W, the NFC wireless charging application requires a series matching circuit. The series matching is not suitable for the NFC communication application due to the low quality factor of the series matching circuit because of the high impedance of the rectifier 7 with no or low charging power, resulting in a low voltage between the first pin 12 and the second pin 13, which is the input voltage for the communication stage 3 and the charging stage 6.

[0008] US 2015 / 0054345 A1 discloses a mobile device for implementing a wireless communication application with another device at a carrier frequency of 13.56 MHz and for implementing an energy harvesting application at another carrier frequency of 6.78 MHz for charging a battery of the mobile device. In order to achieve a resonance match to both different carrier frequencies, the matching circuit of the mobile device comprises four switches for switching several inductors and capacitors of the matching circuit in order to tune to these different carrier frequencies. Furthermore, two of these switches are also used as overvoltage protection to protect the harvesting stage. SUMMARY

[0009] It is an object of the present invention to provide a mobile device and a method implementing an optimized wireless communication application and a wireless charging application with less volume consumption and higher efficiency in the mobile device.

[0010] The mobile device according to claim 1 and the method according to claim 6 achieve this object.

[0011] The integrated circuit of the inventive mobile device comprises a switch short-circuiting the antenna input pin of the charging application in the wireless communication application to ensure an optimal match of the wireless communication application, which can be achieved by having no capacitance of the matching circuit in the signal path to the communication stage. Thus, the matching circuit of the wireless communication application only implements a parallel match of the capacitance in parallel to the antenna and the communication stage. When the switch is in its open state, the match of the antenna at the input pin of the charging application is optimized for the charging application, which is only achieved by a series match. Thus, the matching circuit of the charging application only implements a series match of the capacitance in series in the connection from the antenna to the harvesting stage. Furthermore, both applications are handled with the same magnetic field and one specific carrier frequency, in particular with a carrier frequency of 13.56 MHz. These features ensure a large communication range in the communication application and a maximum energy transfer in the charging application and all this with the same carrier frequency, reducing the technical complexity of another device (card reader) and the mobile device using two different carrier frequencies.

[0012] These and other aspects of the present invention will become apparent from and elucidated with respect to the embodiments described hereinafter. It will be appreciated by the skilled in the art that various embodiments can be combined. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 A mobile device according to the prior art is shown.

[0014] Figure 2 A mobile device according to a preferred embodiment of the present invention is shown.

[0015] Figure 3The schematic diagrams of a poller device and a listener device are shown to simulate a first use case for a wireless communication application, wherein, according to Figure 1 Using existing mobile devices as eavesdroppers.

[0016] Figure 4 The schematic diagrams of a poller device and a listener device are shown to simulate a second use case for a wireless communication application, wherein, according to Figure 2 A mobile device with a switch is used as a listener.

[0017] Figure 5 The schematic diagrams of the poller and listener devices are shown to simulate a third use case for a charging application, wherein, according to Figure 2 A mobile device with a switch is used as a listener. Detailed Implementation

[0018] Figure 2 A mobile device 16 according to a preferred embodiment of the invention is shown, which wirelessly communicates with other devices via a magnetic field at a carrier frequency of 13.56 MHz and charges the battery of the mobile device 16. Such wireless communication applications are known, for example, from standards such as ISO 14443 or ISO 15693. Other frequencies in the HF band can also be used. The mobile device 16 can be a mobile phone, a smartwatch, or any other mobile smart device that combines various functions to enable wireless communication applications with another device and to enable energy harvesting (especially charging applications) to charge the battery 17 of the mobile device 16.

[0019] Mobile device 16 includes an integrated circuit 18 with a communication stage 19, which includes a modulator 20 and a demodulator 21 to enable wireless communication with another NFC-enabled device based on the NFC standard. The communication partner initiating the communication is called the poller, the other communication partner is called the listener, and the communication partner providing the magnetic field is active. Furthermore, mobile device 16 includes a collection stage 22 with a rectifier 23 that generates and provides, for example, a 5-volt rectified DC voltage VDDC, which is supplied to a battery charger 24 of collection stage 22 for wireless charging of battery 17 of mobile device 16. Additionally, the DC voltage VDDC is supplied from rectifier 23 to power pin 40 of integrated circuit 18, to which a microcontroller unit or other processing stage of mobile device 16 can be attached to power pin 40 to power the processing stage. Antenna 25 is connected to a first pin 27 and a second pin 28 of integrated circuit 18 via a matching circuit 26. The first pin 27 and the second pin 28 within integrated circuit 18 are directly connected to the rectifier 23 of collection stage 22. The first contact of antenna 25 is connected to the first pin 27 via the first capacitor 29 of matching circuit 26, and the second contact of antenna 25 is connected to the second pin 28 via the second capacitor 30 of matching circuit 26.

[0020] Furthermore, the integrated circuit 18 of the mobile device 16 includes a third pin 31 and a fourth pin 32 for directly connecting the communication stage 19 to the antenna 25; and a first pin 27 and a second pin 28 are arranged on the integrated circuit 18 for connecting the collection stage 22 to the single antenna 25 via a matching circuit 26. The integrated circuit 18 also includes a switch 33 connected in parallel and directly connected to the rectifier 23, and directly connected to the first pin 27 and the second pin 28 of the integrated circuit 18. The switch 33 can be switched to its on or off state, shorting the first pin 27 and the second pin 28 to enable a wireless communication mode or application with increased communication range. This increased communication range is achieved through parallel matching only, where the first capacitor 29 and the second capacitor 30 are connected in series with each other and in parallel with the antenna 25, and there is no capacitor in the direct signal path from the antenna 25 to the communication stage 19. The switch 33 can also be switched to its off or on state to enable charging applications that transfer high-power energy from other devices in their active mode. This high-power transmission is achieved through series-only matching, wherein the signal path is from antenna 25 to first capacitor 29 to rectifier 23, and from rectifier 23 to second capacitor 30 to antenna 25.

[0021] The following explains use cases for mobile device 16 implemented via a wristwatch, which implements a method for enabling wireless communication with another device and for implementing a charging application to charge the battery 17 of mobile device 16. For example, the wristwatch can handle fitness applications, monitoring and storing motion data and heart rate data throughout the day, which can be downloaded to a computer via an NFC reader connected to the computer. Figure 2 An NFC reader, not shown, is in its active state and generates a magnetic field with a carrier frequency of 13.56 MHz. It is activated as a poller to query whether the watch (such as mobile device 16) has entered the magnetic field in order to start a wireless communication application to download motion data from the watch.

[0022] The first step of this method is for the mobile device 16 to activate the connection state of switch 33 to achieve an increased communication range for the communication application. The closed switch 33 short-circuits the first pin 27 and the second pin 28, creating a low-impedance path and resulting in high-quality resonance. The transmission of data modulated by modulator 20 to antenna 25, and the transmission of modulated data received by antenna 25 to demodulator 21, are accomplished via third pin 31 and fourth pin 32, which directly connect modulator 20 and demodulator 21 to antenna 25, thereby achieving high voltage and a large communication range. Once the mobile device 16 enters the magnetic field of the NFC reader, stable and high-quality communication between the NFC reader and the mobile device 16 is achieved. During this wireless communication, motion data is downloaded from the mobile device 16 to the computer.

[0023] In the second step of this method, the mobile device 16 communicates with the NFC reader via the magnetic field generated by the NFC reader and determines whether to activate the charging application of the mobile device 16 to charge the battery 17 of the mobile device 16. This decision can be made by the computer / NFC reader or the mobile device 16. Like the communication application, the charging application is processed using the same specific carrier frequency of 13.56 MHz.

[0024] In the third step of the method, the mobile device 16 activates the off state of switch 33 to achieve high-power charging of battery 17 using the energy transferred in the magnetic field during the charging application, since it has been decided to charge battery 17. The open switch 33 enables series matching from the first contact of antenna 25 via the first capacitor 29 and the first pin 27 to rectifier 23, and via the second pin 28 and the second capacitor 30 to the second contact of antenna 25. This series matching enables wireless high-power charging above 0.75 power levels. Although the communication range in the charging application is not as large as in the communication application, communication can still occur between the NFC reader and the mobile device 16. For example, this communication can be used to adjust the signal strength of the magnetic field during different stages of the charging process.

[0025] In the fourth step of the method, after the battery 17 is fully charged, the mobile device 16 activates the connection state of switch 33 to restore the increased communication range for the communication application. This increased communication range allows the mobile device 16 to be positioned a few centimeters away from the NFC reader, thus facilitating manual input by the user, for example, on a wristwatch.

[0026] Figure 3 A schematic diagram 34 of the poller device 35 and the listener device 36 is shown to simulate a first use case of a wireless communication application, wherein, according to Figure 1 The existing mobile phone 1 is used as a listening device 36. The first capacitor 14 and the second capacitor 15 of the matching circuit 11 are both simulated with 275 pF, and the input impedance of the rectifier 7 is simulated with 1k ohms.

[0027] Figure 4 A schematic diagram 37 shows the poller device 38 and the listener device 39, simulating a second use case of a wireless communication application, wherein according to Figure 2 The mobile device 16 with switch 33 in its connected state serves as a listener 39. The first capacitor 29 and the second capacitor 30 of the matching circuit 26 are both simulated with 275 pF, and the input impedance of the rectifier 23 is also simulated with 1k ohms, but switch 33 is closed in its connected state and the input impedance of the rectifier 23 used for antenna 25 is short-circuited.

[0028] Figure 5 It shows the relationship with Figure 4 The polling device 38 and the listening device 39 have the same schematic diagram 37, but in order to simulate the third use case of charging application, the switch 33 of the mobile device 16 is in its off state, and the input impedance of the communication stage 19 is simulated with 50 ohms.

[0029] The simulation results for the three use cases mentioned above can be seen in the table below:

[0030]

[0031] The simulation results prove Figure 2 The technical advantages of the embodiments of the invention are that... Figure 4 In wireless communication applications, the voltage at antenna 25 is high, which results in high-quality communication, and Figure 5 In the charging application, the coupling and voltage at receiver 23 are high, which is beneficial for high power transmission.

[0032] In a further embodiment of the invention, during energy harvesting applications, the DC voltage VDDC provided at power pin 40 is used to power the watch's processing stage. This processing stage can be a microcontroller unit for processing sensor data or a sensor for measuring heart rate. The advantage of this is that during battery 17 charging, the NFC reader, in its active state, provides the power to power the internal processing stage of the device.

Claims

1. A mobile device (16) for implementing wireless communication applications with another device and for implementing energy harvesting applications to charge a battery (17) or to power a processing stage of the mobile device (16), both applications being based on a magnetic field having a specific carrier frequency within the HF band, the mobile device (16) including an integrated circuit (18) having: A communication stage (19) includes a modulator (20) and a demodulator (21), said modulator (20) and demodulator (21) being configured to enable load-modulated wireless communication with said other device, and A harvesting stage (22), constructed for wireless energy harvesting for a mobile device (16), comprising a rectifier (23) for providing a rectified DC voltage (VDDC), the rectifier (23) being connected via a first pin (27) and a second pin (28) of the integrated circuit (18) to a matching circuit (26) of the mobile device (16), the matching circuit (26) being connected to an antenna (25) of the mobile device (16), characterized in that: The communication stage (19) and the collection stage (22) are constructed to operate at the same specific carrier frequency in both applications, and The modulator (20) and demodulator (21) are directly connected to the antenna (25) via the third pin (31) and the fourth pin (32) of the integrated circuit (18), and The integrated circuit (18) includes a switch (33) connected in parallel and directly connected to the rectifier (23), and directly connected to the first pin (27) and the second pin (28) of the integrated circuit (18). The switch (33) is switched to its connected state to short-circuit the first pin (27) and the second pin (28), so that the wireless communication application can be realized using only the capacitors (29, 30) arranged in parallel with the antenna (25) in the matching circuit (26), and The switch (33) is switched to its off state so that the charging application can be realized using only the capacitors (29, 30) arranged in series with the antenna (25) in the matching circuit (26).

2. The mobile device (16) according to claim 1, wherein, The matching circuit consists of only two capacitors, namely the first capacitor (29) and the second capacitor (30).

3. The mobile device (16) according to claim 1 or 2, wherein, The communication level is configured to communicate with the other device even when the switch (33) is switched to its off state to enable the charging application.

4. The mobile device (16) according to any one of claims 1 to 3, wherein, The collection stage (22) includes a battery charger (24) which is powered by a rectified DC voltage (VDDC) and connected to the battery (17) to charge the battery (17) using the collected energy.

5. The mobile device (16) according to any one of claims 1 to 4, wherein, The collection stage (22) is connected to the power supply pin (40) of the integrated circuit (18) to provide a rectified DC voltage (VDDC) at the power supply pin (40) and to use the collected energy to power the processing stage of the mobile device (16).

6. A method for implementing a wireless communication application with another device and for implementing a charging application to charge a battery (17) of the mobile device (16), both applications being based on a magnetic field having the same specific carrier frequency within the HF band, the method being performed by the mobile device (16) according to any one of claims 1 to 4, and comprising the steps of: Activate the connection state of the switch (33) to achieve an increased communication range for the communication application; Communicate with another device in the same magnetic field and decide whether to activate the charging application to charge the battery (17) of the mobile device (16); If it is decided to charge the battery (17), the off state of the switch (33) is activated to achieve high-power charging of the battery (17) using the energy transferred in the magnetic field during the charging application.

7. The method according to claim 6, further comprising the following step: After the battery (17) is fully charged, the connection state of the switch (33) is activated to enable an increased communication range for the communication application.

8. The method according to claim 6 or 7, further comprising the step of: During the charging application, when the switch (33) is in its open state, it communicates with the other device in the same magnetic field with a reduced communication range.

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