Efficient wireless charging

Abstract

A power supply device (18; 33) and a portable device (19; 34) and a system (17; 32) for wirelessly charging a battery (20) of a portable device (19, 34), the power supply device (18; 33) comprising a power transmitter stage and a power receiver stage connected to a power antenna (25), the portable device (19; 34) comprises a portable transmitter stage and a portable receiver stage connected to a portable antenna (31), where the power transmitter stage is configured to generate a magnetic field in the RFID frequency range and to modulate it with transmitter data and to transmit the modulated magnetic field with a power antenna (25), and the portable receiver stage is configured to receive the modulated magnetic field from the power antenna (25). The portable receiver stage is configured to receive an antenna signal (30) from a receiver antenna (31) exposed to a modulated magnetic field, and to demodulate transmitter data and to rectify the antenna signal to charge a battery (20) during a charging period, the portable transmitter stage is configured to modulate the magnetic field with portable transmitter data using amplitude modulation, and to charge the battery (20) during a charging period. The power receiver stage is configured to demodulate portable transmitter data, the portable transmitter stage is configured to transmit power adjustment data to increase or decrease the power required to charge the battery (20) transmitted with a magnetic field transmitted with a power antenna (25) of the power transmitter stage, the power receiver stage is configured to receive power adjustment data and to direct the power transmitter stage to transmit more or less power in the generated magnetic field, wherein the power supply device (18; 33) and a portable device (19; 34) is constructed in an active charging mode, and wherein the power transmitter stage in the active charging mode is constructed to add a function of modulating the magnetic field using frequency modulation to at least transmit power adjustment data, and wherein the portable receiver stage in the active charging mode is configured to process frequency demodulation of the antenna signal (30) to receive at least the power adjustment data.

Description

Technical Field

[0001] The present invention relates to a system for a power supply device and a portable device for wirelessly charging a battery of the portable device. The power supply device includes a power transmitter stage and a power receiver stage connected to a power antenna. The portable device includes a portable transmitter stage and a portable receiver stage connected to a portable antenna. The power transmitter stage is configured to generate a magnetic field in the RFID frequency range, modulate it with transmitter data, and transmit the modulated magnetic field with the power antenna. The portable receiver stage is configured to receive an antenna signal from a receiver antenna exposed to the modulated magnetic field, demodulate the transmitter data, and rectify the antenna signal to charge the battery during a charging cycle. The portable transmitter stage is configured to modulate a magnetic field with portable transmitter data using amplitude modulation. The power receiver stage is configured to demodulate the portable transmitter data. The portable transmitter stage is configured to transmit power adjustment data to increase or decrease the power transmitted by the magnetic field transmitted by the power antenna of the power transmitter stage and required for charging the battery. The power receiver stage is configured to receive the power adjustment data and direct the power transmitter stage to transmit more or less power in the generated magnetic field. Background Art

[0002] Wireless charging is used for various different portable devices, such as mobile phones or headphones. The portable device only needs to be close to the power supply device, and the power supply device generates and transmits a magnetic field through the antenna of the power supply device. The advantage is that there is no need for wires to charge the portable device. In some of these systems, the power supply device only transmits a magnetic field, while some newer systems include a feedback loop from the portable device to the power supply device to regulate the power of the magnetic field.

[0003] Figure 1 This kind of system of the power supply device 1 and the portable device 2 with a battery 3 known to those skilled in the art is shown. For example, such a system is described in the NFC Forum TM Technical Specification Version 1.0. The power supply device 1 called a "poller" includes an antenna 4 that transmits a magnetic field with a frequency of 13.56 MHz. The portable device 2 called a "listener" includes an antenna 5 exposed to the magnetic field transmitted by the power supply device 1. A matching circuit 15 matches the impedance of the output pin of the antenna 5 with the input pin of a rectifier 6. The rectifier 6 uses a bridge rectifier to rectify the antenna signal and provide a DC voltage. The charging stage 7 of the portable device 2 is used to charge the battery 3. Since the charging stage 7 includes a charger IC 8 that requires a power supply voltage of, for example, 5V + / - 10%, a DC / DC converter 9 is used to convert the DC voltage provided by the rectifier 6 into an appropriate input voltage U at the input pin 10 of the charging stage 7 I .

[0004] The battery 3 is a lithium-ion battery, which needs to be charged by the charging stage 7 with different charging currents I C and charging voltages during different time periods. To achieve this, the charging stage 7 includes a series ohmic resistance component 11 in the path between the input pin 10 and the battery 3 to generate a measurement voltage, which is measured by the current measurement stage 12 to measure the charging current I for charging the battery 3 C . The charging stage 7 also includes a digital control stage 13, which generates power adjustment information 16 when the input voltage U I at the input pin 10 and / or the charging current I for charging the battery 3 C is too low or too high. Such power adjustment information 16 is provided by the digital control stage 13 to the Cless communication stage 14 compliant with the NFC communication protocol to transmit the power adjustment information 16 to the power supply device 1. Through this feedback loop from the portable device 2 to the power supply device 1, the charging stage 7 can request more or less power in the magnetic field provided by the power supply device 1

[0005] Figure 2 Shows a time graph of the charging current Ic loaded to the battery 3 in three different time periods TA, TB, and TC Figure 2 Also shows the input voltage U at the input pin 10 of the charging stage 7 during the time periods TA, TB, and TC I and the actual battery voltage U loaded to the battery 3 BAT . To actually load to the battery 3, only the battery voltage U BAT is multiplied by the charging current Ic. The wireless transmission power from the power supply device to the portable device is in the range up to 1W as specified by, for example, the NFC-Forum specification. This amount of energy is sufficient to charge the battery of, for example, headphones, but not sufficient to charge a mobile phone within a reasonable time frame

[0006] The NFC communication protocol defines the use of amplitude modulation in wireless charging standards WLC (such as Qi and NFC-WLC). The disadvantage of such prior art systems is that during the "low" phase of AM, less power is transmitted. This in turn increases the charging time and reduces the power transfer efficiency, thus increasing power losses and raising the temperature of the devices involved. The NFC Forum defines two amplitude modulation systems, namely Class A and Class B

[0007] · Class A is characterized by the use of on / off keying with a 100% modulation depth. During modulation, the amplitude is zero, so the transmitted power is also zero. At the same time, both the power transmission device and the receiving device are powered on, so energy is consumed even when no power is being transmitted

[0008] ·Class B is characterized by a modulation depth of 10%. However, since the transmitted power is proportional to the square of the amplitude, this means that the transmitted power during modulation drops to 81% of the maximum value. This represents a lower power loss than when using Class A modulation, but it is still significant. Summary of the Invention

[0009] The object of the present invention is to provide a system for a power supply device and a portable device for wirelessly charging the battery of the portable device, which system is capable of wirelessly transmitting more power to enable faster charging and / or to be able to charge a portable device with a larger battery capacity.

[0010] This object is achieved in the system according to claim 1.

[0011] The claimed system can use amplitude modulation defined by the NFC standard or any other type of modulation defined in other standards in the RFID field to meet these conditions, but when the charging mode is activated, a function of using frequency modulation is added, so that even during the modulation of the magnetic field to transmit, for example, power adjustment information, maximum power transmission can be achieved through the magnetic field. The claimed system can be implemented to be backward compatible with the NFC charging system, which requests amplitude modulation to transmit power adjustment information, but if both the power supply device and the portable device are constructed to use frequency modulation during the activation of the charging mode, more power can be transmitted in a shorter charging time. Since the power transmitted in a frequency-modulated magnetic field does not change as in an amplitude-modulated magnetic field, the output voltage of the rectifier that rectifies the antenna signal does not change, which makes the further processing of the rectified voltage technically simpler and less complex, thus ensuring a stable power supply voltage at all levels of the portable device.

[0012] In a preferred embodiment of the present invention, the power transmitter stage includes an oversampling power amplifier, which is implemented as a switched-capacitor amplifier that generates a sine wave. Such an amplifier is known from EP 3 182 585 B, but is capable of producing an additional positive combined effect with the claimed system.

[0013] With reference to the embodiments described below, these and other aspects of the present invention will become apparent and be elucidated. Those skilled in the art will understand that various embodiments can be combined. Brief Description of the Drawings

[0014] Figure 1 A system known to those skilled in the art is shown, which system includes a power supply device and a portable device with a wirelessly charged battery.

[0015] Figure 2 Shows Figure 1 a time graph of the charging current for charging the battery of the portable device and the input voltage of the charging stage of the system according to

[0016] Figure 3 A system according to an embodiment of the present invention is shown, which includes a power supply device and a portable device with a wirelessly charged battery.

[0017] Figure 4 An amplitude - modulated signal and a frequency - modulated signal are shown.

[0018] Figure 5 Another system according to the present invention is shown, which includes a power supply device and a portable device with a wirelessly charged battery.

[0019] Figure 6 A general explanation of I / Q modulation for a system that can be used for Figure 5 is shown. Detailed Description of the Invention

[0020] Figure 3 A schematic embodiment of a system 17 of a power supply device 18 and a portable device 19 for wirelessly charging a battery 20 is shown. In this embodiment, a power transmitter and receiver stage 21 of the power supply device 18 is shown, which includes a magnetic - field generation stage 22 and a power - data generation and extraction stage 23 connected to a processor 24 of the power supply device 18. The power supply device 18 can be implemented as, for example, a charging station to charge the batteries of wireless earphones or mobile phones or other portable devices. The power transmitter and receiver stage 21 can be powered by mains electricity or a larger battery of the power supply device 18. The magnetic - field generation stage 22 is configured to generate a magnetic field with a frequency of 13.52 MHz in the RFID frequency range, modulate it with transmitter data received from the power - data generation and extraction stage 23, and transmit the modulated magnetic field with a power antenna 25.

[0021] The portable device 19 includes a portable transmitter and receiver stage 26, which includes a portable power extraction and modulation stage 27 and a portable data generation and extraction stage 28 connected to a processor 29 of the portable device 19. The portable data generation and extraction stage 28 is configured to receive an antenna signal 30 from a receiver antenna 31 exposed to the modulated magnetic field to demodulate the transmitter data. The portable power extraction and modulation stage 27 is configured to rectify the antenna signal 30 required to power a charging stage (not shown) to charge the battery 20 during a charging cycle.

[0022] System 17 is capable of enabling data transfer from the portable device 19 to the power supply device 18. Such data can be transmitter data, for example, transmitting the serial number of the portable device or information about the type of the portable device 19 to the power supply device 18. In addition, such transmitter data can be power adjustment data for increasing or decreasing the power transmitted by the magnetic field transmitted by the power supply transmitter and receiver stage 21 with the power antenna 25 and required for charging the battery 20. To achieve this, the portable power extraction and modulation stage 27 is constructed to modulate the magnetic field using the transmitter data or power adjustment data provided by the portable data generation and extraction stage 28. The power supply transmitter and receiver stage 21 is constructed to demodulate the transmitter data to provide information about the portable device 19 to the power supply device 18, or to demodulate the power adjustment data and direct the part of the power supply transmitter and receiver stage 21 responsible for generating the magnetic field and the power transmitted by the magnetic field. Depending on the amplitude and / or form of the magnetic field wave (such as SIN, square, triangle, etc.), the power supply transmitter and receiver stage 21 is constructed to transmit more or less power in the generated magnetic field.

[0023] Prior art systems, such as those based on Figure 1 and Figure 2 described systems, use amplitude modulation, particularly load modulation, for these communications between the power supply device and the portable device. This is the case for both the transmitter data in application-related communications and the communication of the above-mentioned power adjustment data when the charging mode for charging the portable device is activated. In addition, for example, such application-related communication of the transmitter data can be communication between a payment terminal (power supply device) and a mobile phone (portable device) for payment applications.

[0024] As a first embodiment of the present invention, system 17 is further capable of enabling the power supply transmitter and receiver stage 21 in the activated charging mode to be constructed to add the function of modulating the magnetic field using frequency modulation. To demodulate such a frequency-modulated magnetic field, the portable transmitter and receiver stage 26 in the activated charging mode is constructed to process the frequency demodulation of the antenna signal 30 from the antenna signal of the portable antenna 31. This enables the power supply device 18 to transmit various transmitter data to the portable device 19 in a manner that basically does not affect, particularly does not reduce, the power transmitted in the magnetic field. This effect can be explained according to Figure 4 which shows an amplitude-modulated signal and a frequency-modulated signal. Since the power transmitted in these signals is related to the area under the modulation signal, each time the amplitude-modulated signal transmits the information in the transmitter data, the amplitude of the modulation signal decreases, and the power transmitted in the magnetic field also decreases. Since in the activated charging mode, the power transmitted in the magnetic field is basically not affected by the frequency-modulated communication of the transmitter data from the power supply device 18 to the portable device 19, the charging time can be shortened compared to the prior art charging systems.

[0025] In some embodiments, the portable transmitter and receiver stage 26 may also be configured to use frequency modulation to, for example, frequency-modulate power adjustment data, and in these embodiments the power transmitter and receiver stage 21 is configured to demodulate such transmitter data. Although the magnetic field is generated by the magnetic field generation stage 22 of the power transmitter and receiver stage 21, its frequency and / or phase may be affected (modulated) by elements (such as capacitors or coils) in the magnetic field, and the portable transmitter and receiver stage 26 may switch these elements to frequency- and / or phase-modulate the magnetic field with the transmitter data.

[0026] In some embodiments of the present invention, the power device 18 and the portable device 19 may use frequency modulation as the sole modulation method during various types of application-related communications and during activation and deactivation of the charging mode. In a preferred embodiment of the present invention, the power transmitter and receiver stage 21 and the portable transmitter and receiver stage 26 are configured to use amplitude modulation to modulate and demodulate the magnetic field when the charging mode is disabled for communications for various different applications, such as payment or identification, which may be based on various different RFID standards, such as the ISO18.092 standard or the NFC Forum specification. Only after activating the charging mode that requires maximum power transfer from the power device 18 to the portable device 19 is frequency modulation used solely for communications between the power device 18 and the portable device 19. In another embodiment of the present invention, amplitude modulation and frequency modulation may be used simultaneously during activation and / or deactivation of the charging mode to enable the power device 18 and the portable device 19 to communicate in two parallel communication channels.

[0027] In another embodiment of the present invention, even during activation of the charging mode, the power device 18 may use amplitude modulation to transfer power adjustment data to portable devices 19 that are not enabled by the portable transmitter and receiver stage 26 for communication based on frequency modulation. This enables backward compatibility with portable devices of prior art systems such as the portable device 2 shown in Figure 1 . Advantageously, in addition to amplitude modulation, the power device 18 is also capable of communicating with portable devices such as the portable device 19 shown in Figure 3 by frequency modulation during activation of the charging mode. This enables the power device 18 and the portable device 19 of the present invention that use frequency modulation during the charging mode to achieve a faster charging mode, thereby reducing overhead and increasing efficiency. In addition, charging at a constant power is more efficient than using variable power.

[0028] Figure 5 A system 32 showing another embodiment of the present invention includes a power device 33 and a portable device 34 with a battery 20 for wireless charging. The system 32 is related toFigure 3 The system 17 shown differs in that it implements a power transmitter stage 35 and a portable receiver stage 36, which are only capable of frequency modulation communication from the power device 33 to the portable device 34. However Figure 5 than Figure 3 shows in more detail how the power transmitter stage 35 and the portable receiver stage 36 are implemented.

[0029] The power transmitter stage 35 includes a power amplifier 37, which is an oversampling power amplifier implemented as a sine wave generating switched capacitor amplifier. Such a power amplifier 37 is known from EP 3 182 585 B. In another embodiment, the power amplifier can be implemented as a class C amplifier that requires external filtering.

[0030] The power transmitter stage 35 also includes a reference oscillator 38, which consists of a crystal oscillator that generates a frequency in the range of 10 - 60 MHz defined by the oscillation mode of the deployed quartz crystal.

[0031] The power transmitter stage 35 also includes a power transmitter PLL 39, which consists of a phase detector, a loop filter, a voltage controlled oscillator, and a feedback divider. It converts the frequency from the reference oscillator 38 into an appropriate output frequency. In a standard NFC device with a square wave output, the output frequency of the PLL is typically directly the 13.56 MHz RF output frequency. In the case of the power transmitter PLL 39 with an oversampling power amplifier 36, due to the oversampling power amplifier 37, this frequency is in the range of 433 to 868 MHz.

[0032] The feedback division ratio is controlled digitally, which results in a change in the output frequency, thus generating frequency shift keying modulation. This control can be achieved through a Σ-Δ modulator, which converts the power transmitter PLL 38 into a so-called fractional-N PLL, thus allowing a large PLL loop bandwidth and therefore enabling a high data rate, or it can be directly controlled in the case of integer-N PLL operation. However, the latter requires a low PLL input reference frequency and thus a low PLL bandwidth, which limits the data rate of the frequency modulation communication.

[0033] The PLL divider control is processed by the power data generation stage 40. The power data generation stage 40 also utilizes data preprocessing, which adds physical NFC protocol layers, anti-collision details, etc. When using a fractional-N PLL and / or a (Gaussian) filtering stage to limit the spectral bandwidth of the FSK modulation, it can also include the above-mentioned Σ-Δ modulator.

[0034] The portable receiver stage 36 of the portable device 34 includes a portable receiver PLL 41, which consists of a phase detector, a loop filter, a voltage-controlled oscillator, and a feedback frequency divider. Its main purpose is to extract the clock from the magnetic field and supply it to the power extraction stage 42. Since the portable receiver PLL 41 follows the frequency of the magnetic field, any frequency change in the magnetic field, such as frequency modulation, can be regarded as an AC signal AC supplied to the input of the slicer 43.

[0035] The slicer 43 consists of the following parts

[0036] 1) A low-pass filter (LPF) for extracting (averaging) the slicing level from the output of the PLL loop filter, and

[0037] 2) A comparator for comparing the output of the loop filter with the output of the LPF

[0038] The portable receiver stage 36 also includes a data post-processing stage 44, which receives the output of the slicer 43 and processes the physical NFC protocol layer, anti-collision details, etc.

[0039] The power extraction stage 42 generally consists of a passive or active rectifier, a voltage-limiting stage using a shunt regulator, and a (battery) charger.

[0040] By Figure 5 In the specific implementation of the system 32 shown in, frequency shift keying can be used as a digital implementation of frequency modulation for transmitting transmitter data from the power device 33 to the portable device 34 during the active charging mode. The charging mode can be activated by the power device 33 and / or the portable device 34, and can be automatically activated when the portable device 34 moves into the magnetic field of the power device 33. Appropriate stages required to implement frequency modulation communication from the portable device 34 to the power device 33 can be added to the system 32.

[0041] In another alternative embodiment of the present invention, instead of modulating the division ratio of the PLL as described above, IQ modulation can also be used, where the in-phase and quadrature (0 and 90 degrees) RF signals generated by the power transmitter PLL 39 are mixed with two 90-degree phase-shifted (I&Q) data signals, and then an addition stage is performed before entering the power amplifier 37. IQ modulation results in frequency conversion, which can be used to generate an FSK-modulated RF signal. As Figure 6 shown in, the resulting signal is an intermediate frequency (IF), however, it can also be directly mixed to the radio frequency (RF).

[0042] Instead of using the portable receiver PLL 41 for the portable device 34, an orthogonal demodulator can also be used to demodulate the FSK signal. In this case, the input signal can be directly obtained from the portable antenna 31 or from the intermediate frequency (IF) mixing stage and converted to baseband using an IQ demodulator for further processing to extract the FSK data.

[0043] In other embodiments of the present invention, various different combinations of activating or deactivating the charging mode and using amplitude modulation and / or frequency modulation for transmitter data transmission between the power device and the portable device can be implemented.

Claims

1. A system (17; 32) of a power supply device (18; 33) and a portable device (19; 34) for wirelessly charging a battery (20) of the portable device (19, 34), the power supply device (18; 33) comprising a power transmitter stage and a power receiver stage connected to a power antenna (25), and the portable device (19; 34) comprising a portable transmitter stage and a portable receiver stage connected to a portable antenna (31), wherein the power transmitter stage is configured to generate a magnetic field in the RFID frequency range, modulate it with transmitter data, and transmit the modulated magnetic field with the power antenna (25), and the portable receiver stage is configured to receive an antenna signal (30) from the receiver antenna (31) exposed to the modulated magnetic field, demodulate the transmitter data, and rectify the antenna signal to charge the battery (20) during a charging cycle, and the portable transmitter stage is configured to modulate the magnetic field with portable transmitter data using amplitude modulation, and the power receiver stage is configured to demodulate the portable transmitter data, and the portable transmitter stage is configured to transmit power adjustment data to increase or decrease the power required to charge the battery (20) transmitted by the magnetic field transmitted by the power antenna (25) of the power transmitter stage, and the power receiver stage is configured to receive the power adjustment data and direct the power transmitter stage to transmit more or less power in the generated magnetic field, characterized in that the power supply device (18; 33) and the portable device (19; 34) are configured to activate a charging mode, and wherein the power transmitter stage in the activated charging mode is configured to add a function of modulating the magnetic field using frequency modulation to transmit the transmitter data, and wherein the portable receiver stage in the activated charging mode is configured to process frequency demodulation of the antenna signal (30) to receive the transmitter data.

2. The system (17; 32) according to claim 1, wherein the power supply device (18; 33) and the portable device (19; 34) are configured to use both amplitude modulation and frequency modulation to transmit / receive data when the charging mode is activated and / or when the charging mode is deactivated.

3. The system (17; 32) according to claim 1, wherein the power supply device (18; 33) and the portable device (19; 34) are configured to use only frequency modulation to transmit / receive data when the charging mode is activated.

4. The system (17; 32) according to any one of claims 1 to 3, wherein the power supply device (18; 33) and the portable device (19; 34) are configured to use frequency shift keying or IQ modulation as the frequency modulation.

5. The system (32) according to any one of claims 1 to 4, wherein the power transmitter stage includes an oversampling power amplifier (37) implemented as a sinusoidal generating switched capacitor amplifier.

6. The system (17; 32) according to any one of claims 1 to 5, wherein the wireless data interfaces of the power supply device (18; 33) and the portable device (19; 34) are implemented as NFC interfaces compliant with the ISO 18092 standard.

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