WO2018027590A1

WO2018027590A1 - Power receiver and power receiving method for wireless power transfer and terminal device using the same

Info

Publication number: WO2018027590A1
Application number: PCT/CN2016/094239
Authority: WO
Inventors: Tao Chen; Shiwei Liu; Penghui ZHOU
Original assignee: Zte Corporation
Priority date: 2016-08-09
Filing date: 2016-08-09
Publication date: 2018-02-15

Abstract

A power receiver for wireless power transfer comprises a secondary coil, a resonance module, a frequency modulation module and a wireless charging converter. The resonance module operates in different modes for different resonant frequencies, and outputs an alternating current signal. The frequency modulation module comprises a frequency adjuster that modifies an alternating current signal received from the resonance module to produce an alternating current signal having a frequency within a particular frequency range. The wireless charging converter converts an alternating current signal having a frequency in the particular frequency range into a direct current signal.

Description

POWER RECEIVER AND POWER RECEIVING METHOD FOR WIRELESS POWER TRANSFER AND TERMINAL DEVICE USING THE SAME

TECHNICAL FIELD

The present invention relates to wireless power transfer technologies, and in particular to a power receiver and power receiving method for wireless power transfer and a terminal device using the same.

BACKGROUND

Wireless charging uses an electromagnetic field to transfer energy from a power transmitter to a power receiver. Energy is sent through an inductive coupling to the power receiver. The energy can then be used to charge batteries or to run a device, for example.

Different interface standards for wireless charging have been developed by different organisations. In particular, the Wireless Power Consortium (WPC) , the Power Matters Alliance (PMA) and the Alliance For Wireless Power (A4WP) have developed mutually independent standards in wireless charging. Each standard has a specific charging method. As a result, a power receiver that satisfies one of the standards does not satisfactorily charge a battery based on a power transmitter of another standard.

Hence, there is a problem of a lack of compatibility between a power transmitter of one standard and a power receiver of another standard. Many terminal devices only support a single wireless charging method. As a result, when a user uses wireless charging, the user may not be aware that their terminal device is compatible with only a single wireless charging standard.

Users often purchase and use wireless chargers that cannot be used to charge their terminal device (e.g. mobile phone) because the wireless charger that they have purchased has a power transmitter that is of a different standard from the standard used by the power receiver in their terminal device.

It is desirable to address the problem of the lack of compatibility between the different standards. In particular, it is desirable to provide a low cost power receiver that can receive power according to different standards.

SUMMARY

According to the present invention there is provided a power receiver for wireless power transfer comprising:

a secondary coil；

a resonance module configured to operate in a first resonance mode in which the resonance module combines with the secondary coil to form a first resonant circuit having a first resonant frequency in a first frequency range and a second resonance mode in which the resonance module combines with the secondary coil to form a second resonant circuit having a second resonant frequency in a second frequency range, and for outputting an alternating current signal having a frequency in one of the first frequency range and the second frequency range；

a frequency modulation module comprising a frequency adjuster configured to modify an alternating current signal received from the resonance module and having a frequency in the second frequency range to produce an alternating current signal having a frequency within the first frequency range； and

a wireless charging converter configured to convert an alternating current signal having a frequency in the first frequency range received from the frequency modulation module into a direct current signal.

Optionally, the frequency modulation module is configured to operate in a first modulation mode in which the frequency modulation module is configured to transfer an alternating current signal from the resonance module to the wireless charging converter bypassing the frequency adjuster and a second modulation mode in which the frequency modulation module is configured to transfer an alternating current signal from the resonance module to the wireless charging converter via the frequency adjuster.

Optionally, the frequency modulation module comprises:

a frequency detector configured to detect a frequency of an alternating current signal received from the resonance module.

Optionally:

the frequency detector is configured to detect whether a frequency of an alternating current signal received from the resonance module is in the second frequency range； and

when the frequency detector detects that the frequency of the alternating current signal received from the resonance module is in the second frequency range, the resonance module is configured to operate in the second resonance mode and the frequency modulation module is configured to operate in the second modulation mode.

Optionally:

the frequency detector is configured to detect whether a frequency of an alternating current signal received from the resonance module is in the first frequency range； and

when the frequency detector detects that the frequency of the alternating current signal received from the resonance module is in the first frequency range, the resonance module is configured to operate in the first resonance mode and the frequency modulation module is configured to operate in the first modulation mode.

Optionally:

the frequency detector is configured to detect whether a frequency of an alternating current signal received from the resonance module is outside of both the first frequency range and the second frequency range； and

when the frequency detector detects that the frequency of the alternating current signal received from the resonance module is outside of both the first frequency range and the second frequency range, the wireless charging converter is configured to not convert an alternating current signal into a direct current signal.

Optionally, when the frequency detector detects that the frequency of the alternating current signal received from the resonance module is outside of both the first frequency range and the second frequency range, the power receiver is configured to output an alarm signal.

Optionally:

the resonance module comprises a first resonant capacitor for a first frequency range and a second resonant capacitor for a second frequency range；

in the first resonance mode the first resonant capacitor combines with the secondary coil to form a first LC circuit as the first resonant circuit； and

in the second resonance mode the second resonant capacitor combines with the secondary coil to form a second LC circuit as the second resonant circuit.

Optionally, the power receiver comprises:

a rectifier configured to convert an alternating current signal received from the resonance module into a direct current signal for powering the frequency modulation module.

Optionally, the frequency adjuster is configured to reduce the frequency of the alternating current signal received from the resonance module.

Optionally, the frequency adjuster is configured to halve the frequency of the alternating current signal received from the resonance module.

Optionally, the first frequency range is 100kHz to 205kHz.

Optionally, the second frequency range is 277kHz to 357kHz.

According to the present invention there is provided a terminal device comprising a power receiver of an embodiment of the invention.

According to the present invention there is provided a method of receiving power by wireless power transfer comprising:

providing a secondary coil；

selectively operating a resonance module in one of a first resonance mode in which the resonance module combines with the secondary coil to form a first resonant circuit having a first resonant frequency in a first frequency range and a second resonance mode in which the resonance module combines with the secondary coil to form a second resonant circuit having a second resonant frequency in a second frequency range；

outputting an alternating current signal having a frequency in one of the first frequency range and the second frequency range from the resonance module；

receiving an alternating current signal from the resonance module at a frequency modulation module；

selectively operating a frequency adjuster of the frequency modulation module to modify an alternating current signal received from the resonance module and having a frequency in the second frequency range to produce an alternating current signal having a frequency within the first frequency range； and

converting an alternating current signal having a frequency in the first frequency range received from the frequency modulation module into a direct current signal.

Optionally, the frequency modulation module operates in a first modulation mode in which the frequency modulation module transfers an alternating current signal from the resonance module to the wireless charging converter bypassing the frequency adjuster and a second modulation mode in which the frequency modulation module transfers an alternating current signal from the resonance module to the wireless charging converter via the frequency adjuster.

Optionally, the method comprises:

a frequency detector detecting a frequency of an alternating current signal received from the resonance module.

Optionally:

the frequency detector detects whether a frequency of an alternating current signal received from the resonance module is in the second frequency range； and

when the frequency detector detects that the frequency of the alternating current signal received from the resonance module is in the second frequency range, the resonance module operates in the second resonance mode and the frequency modulation module operates in the second modulation mode.

Optionally:

the frequency detector detects whether a frequency of an alternating current signal received from the resonance module is in the first frequency range； and

when the frequency detector detects that the frequency of the alternating current signal received from the resonance module is in the first frequency range, the resonance module operates in the first resonance mode and the frequency modulation operates in the first modulation mode.

Optionally:

the frequency detector detects whether a frequency of an alternating current signal received from the resonance module is outside of both the first frequency range and the second frequency range； and

when the frequency detector detects that the frequency of the alternating current signal received from the resonance module is outside of both the first frequency range and the second frequency range, the wireless charging converter does not convert an alternating current signal into a direct current signal.

Optionally, when the frequency detector detects that the frequency of the alternating current signal received from the resonance module is outside of both the first frequency range and the second frequency range, the power receiver outputs an alarm signal.

Optionally:

Optionally, the method comprises:

a rectifier converting an alternating current signal received from the resonance module into a direct current signal for powering the frequency modulation module.

Optionally, the frequency adjuster reduces the frequency of the alternating current signal received from the resonance module.

Optionally, the frequency adjuster halves the frequency of the alternating current signal received from the resonance module.

Optionally, the first frequency range is 100kHz to 205kHz.

Optionally, the second frequency range is 277kHz to 357kHz.

According to the present invention there is provided a method of charging a terminal device using the method of an embodiment of the invention.

By providing the resonance module that can operate in different resonance modes, the power receiver can be compatible with power transmitters of different standards so as to generate an induction current. By providing the frequency adjuster, the frequency of the alternating current signal output by the resonance module can be adjusted so as to satisfy the charging requirements of the wireless charging converter. The wireless charging converter can then convert the alternating current signal into a direct current signal for charging a battery, for example.

The power receiver requires only one secondary coil, such that the cost of manufacturing the power receiver is kept low. Furthermore, by providing only one secondary coil, rather than two secondary coils for example, the possibility of interference between coils is eliminated. This reduces the possibility of damage to the power receiver and to the components of any device comprising the power receiver.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 schematically depicts a secondary coil and shielding assembly of a power receiver according to an embodiment of the invention；

Figure 2 is a circuit diagram for to a power receiver according to an embodiment of the invention；

Figure 3 is a circuit diagram for a power receiver according to an embodiment of the invention when the resonance module is operating in the second resonance mode and the frequency modulation module is operating in the second modulation mode；

Figure 4 is a circuit diagram for a power receiver according to an embodiment of the invention in which the resonance module is operating in the first resonance mode and the frequency modulation module is operating in the first modulation mode；

Figure 5 is a flow diagram showing a method of receiving power by wireless power transfer according to an embodiment of the invention；

Figure 6 schematically depicts an example of a secondary coil according to an embodiment of the invention； and

Figure 7 schematically depicts another example of a secondary coil according to an embodiment of the invention.

DETAILED DESCRIPTION

Figure 1 schematically depicts in cross-section a terminal device 20 comprising a power receiver 10 according to an embodiment of the invention. The terminal device 20 is a device that is able to consume near field inductive power. The terminal device 20 may be a mobile device such as a mobile phone. The power receiver 10 can alternatively be used in other types of device, such as a tablet, a laptop, or a wearable device, for example.

As depicted in Figure 1, the power receiver 10 comprises a secondary coil 21 (for example, a wireless charging coil) . The secondary coil 21 is configured to convert magnetic flux to electromotive force. In use, the secondary coil 21 couples to a primary coil in a power transmitter of a base station so as to receive magnetic flux. The base station is a device that is able to provide near field inductive power.

As depicted in Figure 1, the terminal device 20 comprises an interface surface 24. The interface surface 24 is a flat part of the surface of the terminal device 20. Optionally, the interface surface 24 is the flat part of the surface of the terminal device 20 that is closest to the secondary coil 21. Merely as an example, the distance from the secondary coil 21 to the interface surface 24 of the terminal device 20 may be at most 2.5mm across the bottom face (as viewed in Figure 1) of the secondary coil 21.

Alternatively, the terminal device 20 comprises an alignment aid 22. The alignment aid 22 may be provided to help a user to properly align the secondary coil 21 of the power receiver 10 to the primary coil of a power transmitter. The alignment aid 22 enables guided positioning. Guided positioning is a method of positioning the terminal device 20 on a corresponding interface surface of a base station (comprising a power transmitter) that provides the user with feedback to properly align the active area of the terminal device 20 to the active area of the base station. The active area is the part of the interface surface of a base station or a terminal device 20 in which a sufficiently high magnetic flux penetrates when the base station is providing power to the terminal device 20.

The alignment aid 22 provides the user with directional guidance, i.e. to where the user should move the terminal device 20, as well as alignment indication, i.e. feedback that the user has reached a properly aligned position.

Merely as an example, the alignment aid 22 may comprise a piece of hard or soft magnetic material. The piece of hard or soft magnetic material may be attracted to a corresponding magnet provided in the power transmitter in the base station. The attractive force between the magnetic material and the magnet provide the user with tactile feedback when the user is placing the terminal device 20 on the interface surface of the base station.

However, the alignment aid 22 is not necessary. When the alignment aid 22 is not provided, the user may perform free positioning. Free positioning is a method of positioning the terminal device 20 on the interface surface of a base station that does not require the user to align the active area of the terminal device 20 to the active area of the base station.

As depicted in Figure 1, optionally the terminal device 20 comprises shielding 23. The shielding is configured to restrict magnetic fields to other components of the terminal device 20.

As shown in Figure 1, the power receiver 10 comprises only one secondary coil 21. The secondary coil 21 has two contact points for electrically connecting the secondary coil 21 to the rest of the circuitry of the power receiver 10.

Figure 2 shows a circuit diagram for a power receiver 10 according to an embodiment of the invention. The secondary coil 21 is shown in the left hand side of Figure 2.

As depicted in Figure 2, the power receiver 10 comprises a resonance module 11. The resonance module 11 is configured to operate in a first resonance mode in which the resonance module 11 combines with the secondary coil 21 to form a first resonant circuit having a first resonant frequency in a first frequency range. The resonance module 11 is further configured to operate in a second resonance mode in which the resonance module 11 combines with the secondary coil 21 to form a second resonant circuit having a second resonant frequency in a second frequency range.

In the example shown in Figure 2, the resonance module 11 is configured to switch between the first resonance mode and the second resonance mode by using the switches K1 and K2. In the example shown in Figure 2, the resonance module 11 comprises a first resonant capacitor Cs1 with a first frequency range and a second resonant capacitor Cs2 with a second frequency range. In one embodiment, the first resonant capacitor Cs1 can be a resonant capacitor which conforms to the WPC standard, and the second resonant capacitor Cs2 can be a resonant capacitor which conforms to the PMA standard. In one embodiment, the switches K1 and K2 are used to control connections or disconnections for the Cs1 and Cs2.

In one example, capacitance C_s for each of the first resonant capacitor Cs1 and the second resonant capacitor Cs2 can be calculated by a formula of C_sf_s ＝ [ (f_s·2π) ²·Ls′] -1. “Ls′” represents an inductance value of a wireless charging coil which meets the WPC standard. The first resonant capacitor Cs1 is calculated according to selecting the “f_s” to be a first frequency (e.g. 100kHz) , and the second resonant capacitor Cs2 is calculated according to selecting the “f_s” to be a second frequency (e.g 277kHz) . In the first resonance mode, the first resonant capacitor Cs1 combines with the secondary coil 21 to form a first LC circuit as the first resonant circuit. In the second resonance mode, the second resonant capacitor Cs2 combines with the secondary coil 21 to form a second LC circuit as the second resonant circuit.

However, it is not essential for the resonance module 11 to comprise a first resonant capacitor Cs1 and a second resonant capacitor Cs2. For example, in an alternative embodiment the resonance module 11 comprises a variable capacitor. The capacitance of the variable capacitor can be changed mechanically or electronically so as to set the resonance frequency of the LC circuit formed by the variable capacitor and the secondary coil 21.

The resonance module 11 is for outputting an alternating current (AC) signal having a frequency in one of the first frequency range and the second frequency range. As will be described below, it is also possible for the resonance module 11 to output an AC signal having a frequency that is outside of both the first frequency range and the second frequency range.

When the terminal device 20 is positioned on the active area of the base station, magnetic flux penetrates through the active area of the base station and the active area of the interface surface 24 of the terminal device 20. The base station provides power to the terminal device 20. The secondary coil 21 converts the magnetic flux to electromotive force. The resonance module 11 outputs a corresponding AC signal. The resonance module 11 outputs an AC signal corresponding to the electromotive force that the secondary coil 21 produces from the magnetic flux.

As shown in Figure 2, the power receiver 10 further comprises a frequency modulation module 12. The resonance module 11 outputs the AC signal to the frequency modulation module 12. The electrical connections between the resonance module 11 and the frequency modulation module 12 are shown in Figure 2. The electrical connections may be formed by simple electrical wires, for example.

The frequency modulation module 12 comprises a frequency adjuster 15 (for example, a frequency divider) . The frequency adjuster 15 receives the AC signal from the resonance module 11. The frequency adjuster 15 is configured to modify an AC signal received from the resonance module 11. The AC signal may have a frequency in the second frequency range. The frequency adjuster 15 is configured to modify the AC signal that has a frequency in the second frequency range to produce an AC signal having a frequency within the first frequency range. The frequency adjuster 15 is configured to adjust frequencies from the second frequency range to the first frequency range. The frequency adjuster 15 outputs the modified AC signal having a frequency in the first frequency range.

As depicted in Figure 2, in an example the power receiver 10 comprises a pair of diodes between the frequency adjuster 15 and the wireless charging converter 16. Optionally, the diodes form part of the frequency modulation module 12. The purpose of the two diodes is to prevent the current flowing backward into the frequency adjuster 15.

As depicted in Figure 2, the power receiver 10 further comprises a wireless charging converter 16. The wireless charging converter 16 is configured to convert AC signals into direct current (DC) signals. In particular, the wireless charging converter 16 is configured to convert an AC signal having a frequency in the first frequency range received from the frequency modulation module 12 into a DC signal. The DC signal may be used for charging a battery of the terminal device 20, or for otherwise powering the terminal device 20, for example.

A power receiver 10 of the present invention can be used with base stations comprising power transmitters according to different wireless charging standards. The resonance module 11 can switch between different resonance modes so that induction currents having different frequencies can be generated.

By means of frequency modulation, a wireless charging signal (i.e. an AC signal) having one frequency can be converted to have a different frequency that satisfies the charging requirements of the wireless charging converter 16. The wireless charging converter 16 then converts the AC signal into a DC signal for use in terminal charging.

The present invention makes it possible to perform wireless charging according to different standards, such that a terminal device 20 can be charged using base stations that satisfy different standards.

An embodiment of the invention is expected to significantly reduce the cost of manufacturing a power receiver that can receive power under different standards. In particular, the power receiver 10 of the present invention only has a single secondary coil 21 and a single wireless charging converter 16.

An embodiment of the invention is expected to reduce the area on the terminal device 20 required for wireless charging. This is because only one secondary coil 21 is required. An embodiment of the invention is expected to make it easier to reduce the size of the terminal device 20.

The power receiver 10 of the present invention has only one secondary coil 21 and can charge using different standards such as the WPC standard and the PMA standard. This is different from known handsets that comprise an independent inner coil for charging using the WPC standard and an outer coil for charging using the PMA standard. In such a known handset, each coil is connected to the motherboard by means of two contact points. In contrast, the power receiver 10 of the present invention has only one secondary coil 21, which has two contact points.

The known handset mentioned above has the problem that there can be interference between the two coils, requiring an intermediate magnetic separating material. An embodiment of the invention is expected to eliminate such interference because only one secondary coil 21 is provided.

The two coils can interfere with each other because charging using one of the coils causes a change in the electric field on the other coil. The change in electric field generates an alternating current. The alternating current causes the power receiver to radiate heat. Radiation of heat leads to unnecessary power consumption. An embodiment of the invention is expected to reduce power consumption by avoiding interference between coils.

The known handset mentioned above has a problem that the total surface area of the coils in more or less the same as the width of the rear casing of the handset. An embodiment of the invention is expected to reduce the total surface area required for the power receiver 10. This makes it easier to make smaller mobile phones 20 that can use wireless power transfer.

The known handset mentioned above has the problem that the cost of manufacture is relatively high. An embodiment of the invention is expected to reduce the cost of manufacturing a power receiver for wireless power transfer. In particular, by requiring only one secondary coil 21 and only one wireless charging converter 16 configured for a particular frequency range, the cost can be reduced compared to a handset that requires two coils.

In an embodiment, the first frequency range can be 100 kHz to 205 kHz. This frequency range is according to the WPC standard. In an embodiment, the second frequency range can be 277 kHz to 357 kHz. This is the frequency range for the PMA standard.

However, it is not necessary for these frequency ranges to be used. In an alternative embodiment of the invention, other frequency ranges are used, which may be according to other standards or may not be according to any particular standard.

According to a further alternative embodiment, the first frequency range may be 277 kHz to 357 kHz, namely for the PMA standard and the second frequency range may be 100 kHz to 205 kHz, namely according to the WPC standard. Hence, according to this further alternative embodiment, the wireless charging converter 16 is configured to convert an AC signal into a DC signal according to the PMA standard. When the AC signal has a frequency according to the WPC standard, the frequency adjuster 15 adjusts the frequency to be according to the PMA standard so that the wireless charging converter 16 can convert the AC signal into a DC signal.

Optionally, the frequency modulation module 12 is configured to operate in a first modulation mode and a second modulation mode. In the first modulation mode, the frequency modulation module 12 is configured to transfer an AC signal from the resonance module 11 to the wireless charging converter 16 bypassing the frequency adjuster 15. In the second modulation mode, the frequency modulation module 12 is configured to transfer an AC signal from the resonance module 11 to the wireless charging converter 16 via the frequency adjuster 15.

In the example shown in Figure 2, the frequency modulation module 12 can be switched between the first modulation mode and the second modulation mode by using the switches K3 and K4. When the switches K3 and K4 are closed, the frequency modulation module 12 is configured to operate in the first modulation mode. The AC signal can transfer from the resonance module 11 along the electrical lines comprising the switches K3 and K4 and reach the wireless charging converter 16 without passing through the frequency adjuster 15. However, when the switches K3 and K4 are open, the AC signal must pass through the frequency adjuster 15 to reach the wireless charging converter 16. If the frequency of the AC signal is within the second frequency range (e.g. 277-357kHz) , the switches K3 and K4 are opened for making the frequency adjuster 15 divide the frequency before transfer to the wireless charging converter 16.

However, it is not essential for the frequency modulation module 12 to have a first modulation mode and a second modulation mode as described above. In an alternative embodiment, the AC signal from the resonance module 11 always passes through the frequency adjuster 15. The frequency adjuster 15 is configured, where necessary, to adjust the frequency of the AC signal, and to output an AC signal that has a frequency in the first frequency range. The wireless charging converter 16 then converts the AC signal into a DC signal.

As depicted in Figure 2, in an embodiment the frequency modulation module 12 comprises a frequency detector 14. The frequency detector 14 is configured to detect a frequency of an AC signal received from the resonance module 11.

As depicted in Figure 2, optionally the resonance module 11 comprises a resonant detection capacitor Cd. The purpose of the resonant detection capacitor Cd is for a resonant detection method. In contrast, the first resonant capacitor Cs1 and the second resonant capacitor Cs2 are for enhancing the power transfer efficiency. When the resonance module 11 is provided with the resonant detection capacitor Cd, the resonance module 11 may combine with the secondary coil 21 to form a dual resonant circuit. The dual resonant circuit has the following resonant frequencies:

In the first equation, L′_s is the self-inductance of the secondary coil 21 when placed on the interface surface of a power transmitter, f_s is a resonant frequency, and C_s is the capacitance of whichever of the first resonant capacitor Cs1 and the second resonant capacitor Cs2 is forming an LC circuit with the secondary coil 21.

In the second equation, f_d is another resonant frequency, L_s is the self-inductance of the secondary coil 21 without magnetically active material that is not part of the power receiver 10 close to the secondary coil 21 (e.g. when the power receiver 10 is away from the interface surface of any power transmitter) , and C_d is the capacitance of the resonant detection capacitor Cd.

Based on the first equation, for a secondary coil 21 of known inductance and for a given target resonant frequency (e.g. within the first frequency range or the second frequency range) , the required capacitance C_s for the first resonant capacitor Cs1 and the second resonant capacitor Cs2 can be calculated.

Optionally, a switch may be provided adjacent to the resonant detection capacitor Cd. This switch is not shown in Figure 2. When the switch is not provided, the resonant detection capacitor Cd has a fixed connection to the secondary coil 21. When the switch is provided, the switch may be configured to remain closed until the wireless changing converter 16 starts to produce and output a DC signal.

The method of measuring the frequency of the AC signal output from the resonance module 11 is not particularly limited. For example, the frequency detector 14 can include circuits for shaping the AC signal into rectangular waves firstly (squaring circuit) , and comparing the shaped waves with an input threshold signal of a comparator, and counting the output signal of the comparator to calculate the frequency of the AC signal.

In an embodiment the power receiver 10 has a default setting in which the resonance module 11 operates in the first resonance mode and outputs an AC signal which is not frequency modulated before being converted by the wireless charging converter 16. For example, when the first frequency range corresponds to the WPC standard, the power receiver 10 may have a default setting of attempting to charge using the WPC standard. If the base station coupled to the power receiver 10 is in accordance with the WPC standard, then wireless charging continues using the power receiver 10 in the default setting. However, if the base station is not in accordance with WPC standard, then it may not be possible to perform wireless charging when the power receiver 10 is in the default setting.

In an example, the default setting of the power receiver 10 is that switch K1 is closed and switch K2 is open. If the detected frequency of the AC signal is greater than or equal to 100kHz and less than or equal to 205 kHz (that is, this detected frequency meets the charging requirements of the WPC standard) , switch K3 and switch K4 are closed to execute the first resonance mode. If the detected frequency of the AC signal is greater than or equal to 277 kHz and less than or equal to 357 kHz (that is, this detected frequency meets the charging requirements of the PMA standard) , switches K1, K3, and K4 are opened, and switch K2 is closed to execute the second resonance mode. If the detected frequency of the AC signal is less than 100kHz, greater than 205kHz and less than 277kHz, or greater than the 357kHz, that means the charger is non-standard charger, and there is no need to execute wireless charging.

Optionally, when it is determined that charging is not possible with the resonance module 11 in the first resonance mode, the resonance module 11 is switched to the second resonance mode. In the example shown in Figure 2, the switching may be performed by opening the switch K1 and closing the switch K2. If the detected frequency is in the second frequency range, then the frequency adjuster 15 is used to adjust the frequency of the AC signal so that the frequency is within the first frequency range. The wireless charging converter 16 then converts the adjusted AC signal into a DC signal.

Optionally, the frequency detector 14 is configured to detect whether a frequency of an AC signal received from the resonance module 11 is in the first frequency range. When the frequency detector 14 detects that the frequency of the AC signal received from the resonance module 11 is in the first frequency range, the resonance module 11 is configured to operate in the first resonance and the frequency modulation module 12 is configured to operate in the first modulation mode. Hence, the resonance module 11 outputs an AC signal having a frequency within the first frequency range. This AC signal is not modified before it is received by the wireless charging converter 16 that converts the AC signal into a DC signal.

In an alternative embodiment, the default setting of the power receiver 10 is for the resonance module 11 to operate in the second resonance mode and for the frequency modulation module 12 to operate in the second modulation mode. If wireless charging is possible in the default setting, then wireless charging continues. However, if it is determined that wireless charging is not possible in the default setting, then the resonance module 11 is switched to operate in the first resonance mode and the frequency modulation module 12 is switched to the first modulation mode.

Optionally, the frequency detector 14 is configured to detect whether a frequency of an AC signal received from the resonance module 11 is in the second frequency range. When the frequency detector 14 detects that the frequency of the AC signal received from the resonance module 11 is in the second frequency range, the resonance module 11 is configured to operate in the second resonance mode and the frequency modulation module 12 is configured to operate in the second modulation mode.

However, it is not essential for the frequency detector to detect whether a frequency of the AC signal received from the resonance module 11 is in the first frequency range or the second frequency range. In particular, in alternative embodiments the power receiver 10 has a default setting for attempting wireless charging within one of the frequency ranges. If wireless charging is not possible in that frequency range, then the power receiver 10 switches to attempt wireless charging according to the other frequency range. In such an embodiment it is not necessary to detect the frequency in order to attempt wireless charging according to two different standards.

The method of determining whether or not wireless charging is possible is not particularly limited. One possibility is that the resonance module 11 does not output an AC signal of sufficient magnitude for it to be detected. This may be an indication that wireless charging is not possible.

Optionally, the frequency detector 14 is configured to detect whether a frequency of an AC signal received from the resonance module 11 is outside of both the first frequency range and the second frequency range. When the frequency detector 14 detects that the frequency of the AC signal received from the resonance module 11 is outside of both the first frequency range and the second frequency range, the wireless charging converter 16 is configured to not convert an AC signal into a DC signal. Hence, if the detected frequency is within any frequency range other than the first frequency range and the second frequency range, then wireless charging is stopped.

However, it is not essential for the wireless charger to not convert an AC signal into a DC signal when the frequency is outside of both frequency ranges. In an alternative embodiment, the power receiver 10 may continue to attempt to perform wireless charging regardless of the frequency of the AC signal output by the resonance module 11.

An embodiment of the invention is expected to provide mode effective protection to the power receiver 10 and the terminal device 20 comprising the power receiver 10. Otherwise, if wireless charging is attempted to be continued even though the frequency is non-standard, this can damage the power receiver 10 and/or the terminal device 20 comprising the power receiver 10.

Optionally, when the frequency detector 14 detects that the frequency of the AC signal received from the resonance module 11 is outside of both the first frequency range and the second frequency range, the power receiver 10 is configured to output an alarm signal. For example, the alarm signal may be a message that the base station is a non-standard charger. The alarm signal helps the user to understand why wireless charging is not possible using the base station.

As depicted in Figure 2, optionally the power receiver 10 comprises a rectifier 13. The rectifier 13 is configured to convert an AC signal received from the resonance module 11 into a DC signal for powering the frequency modulation module 12. In particular, the rectifier 13 is configured to convert the AC signal into a DC signal which is fed to the frequency detector 14 and the frequency adjuster 15. The electrical connections are shown in Figure 2.

Optionally, the rectifier 13 is a full-wave rectifier configured to convert the whole of the input AC signal to a DC signal at its output. As depicted in Figure 2, optionally the rectifier 13 is a bridge rectifier using four diodes. However, other types of rectifier can also be used. For example, in an alternative embodiment the rectifier 13 is a full-wave rectifier using a centre tap transformer and two diodes. As a further alternative, the rectifier 13 may be a half-wave rectifier using a single diode.

As mentioned above, a specific embodiment of the invention is a power receiver 10 configured to be able to perform wireless charging according to the WPC standard and the PMA. The wireless charging converter 16 may be configured to convert an AC signal into a DC signal according to the WPC standard. In such an embodiment, the frequency adjuster 15 is configured to reduce the frequency of the AC signal received from the resonance module 11. This is because the second frequency range is lower than the first frequency range. Of course, the frequency adjuster 15 may be configured to reduce the frequency of the AC signal in other embodiments of the invention that are not limited to the WPC standard or the PMA standard. Optionally, the frequency adjuster 15 can be a frequency divider. Reducing the frequency is lower cost and reduces power consumption I other components compared to increasing the frequency.

However, it is not essential for the frequency adjuster 15 to reduce the frequency of the AC signal received from the resonance module 11. For example, if the first frequency range is higher than the second frequency range, then the frequency adjuster 15 may be configured to increase the frequency of the AC signal received from the resonance module 11.

Optionally, the frequency adjuster 15 is configured to halve the frequency of the AC signal received from the resonance module 11. A simple circuit can be provided to halve the frequency of the AC signal received from the resonance module 11. A frequency divider that halves the frequency is a particularly simple and efficient circuit. Such a simple circuit can be used when halving the second frequency range falls within the first frequency range. For example, if the second frequency range is 277 kHz to 357 kHZ then halving the frequencies in the second frequency range results in a narrower frequency range that falls within the first frequency range of 100 kHz to 205 kHz.

However, it is not necessary for the frequency adjuster 15 to halve the frequency of the AC signal received from the resonance module 11. In an alternative embodiment, the frequency adjuster 15 is configured to change the frequency of the AC signal received from the resonance module 11 according to a different factor or according to a fraction or a percentage. The method of adjusting the frequency of the AC signal is not particularly limited. In an example, a frequency divider is used to adjust the frequency.

Figure 5 is a flowchart showing a method of receiving power by wireless power transfer according to an embodiment of the invention. In step S11, wireless charging is started. This means that the power receiver 10 or the terminal device 20 comprising the power receiver 10 is positioned on the interface surface of a base station comprising a power transmitter.

In step S12, the power receiver 10 is switched to its default setting. In the example shown in Figure 5, the default setting is that switch K1 is closed and switch K2 is open. This means that the resonance module 11 is set to operate in the first resonance mode when the power receiver 10 is in its default setting. In an alternative embodiment, the default setting could be for the resonance module 11 to operate in the second resonance mode.

In step S13, the frequency of the AC signal output by the resonance module 11 is detected by the frequency detector 14. In step S14, it is determined whether the frequency of the AC signal is within the first frequency range. For example, in the example of the WPC standard, step 14 involves determining whether the frequency is greater than 100 kHz and less than 205 kHz.

If it is determined that the frequency of the AC signal is within the first frequency range, then processing proceed to step S15. In step S15, the frequency modulation module 12 is switched to the first modulation mode. In the example shown in Figure 2, this involves closing switches K3 and K4. It may be that switches K3 and K4 are closed as a default, in which case it may not be necessary to close switches K3 and K4. When switches K3 and K4 are closed, the AC signal output from the resonance module 11 reaches the wireless charging converter 16 without having its frequency adjusted. Figure 4 is a circuit diagram for the power receiver 10 when the resonance module 11 is operating in the first resonance mode and the frequency modulation module 12 is operating in the first modulation mode.

In step S16, wireless changing is performed. This involves the wireless charging converter 16 converting the AC signal into a DC signal. The DC signal may be used to charge a battery or otherwise power the terminal device 20, for example.

If it is determined in step S14 that the frequency of the AC signal output by the resonance module 11 is not within the first frequency range, then processing proceed to step S17. In step S17, it is determined whether the frequency is within the second frequency range. In the example of the PMA standard, step S17 involves determining whether the frequency is greater than 277 kHz and less than 357 kHz.

If it is determined in step S17 that the frequency is within the second frequency range, then the processing proceeds to step S18. In step S18, the resonance module 11 is switched to operate in the second resonance mode and the frequency modulation module 12 is switched to operate in the second modulation mode. In the example shown in Figure 2, this involves closing switch K2, opening switch K1 and opening switches K3 and K4. It may be that switches K3 and K4 are open as a default, in which case it may not be necessary to open switches K3 and K4 in order for the frequency modulation module 12 to operate in the second modulation mode. Figure 3 is a circuit diagram for the power receiver 10 when the resonance module 11 is operating in the second resonance mode and the frequency modulation module 12 is operating in the second modulation mode.

In step S19, the frequency adjuster 15 adjusts the frequency of the AC signal output by the resonance module 11. As a result, the AC signal is adjusted so that its frequency is within the first frequency range. Processing then proceeds to step S16.

If in step S17 it is determined that the frequency is not within the second frequency range, then the processing proceeds to step S20. In step S20 wireless charging is stopped. This is because the frequency is not within the first frequency range or within the second frequency range. Hence, the wireless charging stops so that the power receiver 10 and the terminal device 20 comprising the power receiver 10 are protected. As an example, wireless charging may be stopped by opening both switch K1 and switch K2. Alternatively, wireless charging may be stopped by disconnecting the terminal device 20 from the charger or by controlling the wireless charging converter 16 to stop charging.

In step S21, the power receiver 10 outputs an alarm signal. The alarm signal may indicate that the base station is a non-standard charger.

The process described above is merely one exemplary embodiment. Other process flows are possible. Below, further optional features of the power received 10 of the present invention are described.

As depicted in Figure 2, optionally the power receiver comprises a terminal charging management module 17. Alternatively, the terminal charging management module 17 may be part of the terminal device 20 rather than the power receiver 10. The terminal charging management module may be a communications and control unit for the power receiver 10. Optionally, the terminal charging management module 17 comprises the digital logic part of the power receiver 10. Optionally, the terminal charging management module 17 is configured to monitor sensing circuits in the power receiver 10 or elsewhere in the terminal device 20. For example, in an embodiment the terminal charging management module 17 is configured to monitor a sensing circuit that measures the temperature of a rechargeable battery of the terminal device 20. Optionally, the terminal charging management module 17 comprises two capacitors in series with two switches.

As depicted in Figure 2, in an embodiment the power receiver 10 comprises a control module 18. Alternatively, the control module 18 may be part of the terminal device 20 rather than the power receiver 10. The frequency detector 14 is configured to output detection results to the control module 18. The control module 18 is configured to control switching of the resonance module 11 between the first resonance mode and the second resonance mode. The control module 18 is configured to control switching of the frequency modulation module 12 between the first modulation mode and the second modulation mode. For example, in an embodiment the control module 18 is configured to control the switches K1, K2, K3 and K4.

In an embodiment the control module 18 is configured to control the frequency detector 14. For example, in an embodiment the control module 18 is configured to control the frequency detector 14 to detect the frequency of the AC signal output from the resonance module 11 when it is determined that wireless charging is not possible using the default setting of the power receiver 10.

In an embodiment the control module 18 is configured to control the frequency adjuster 15. For example, in an embodiment the control module 18 is configured to control the frequency adjuster 15 to adjust the frequency of the AC signal output from the resonance module 11 when it is determined that the frequency of the AC signal output from the resonance module 11 is within the second frequency range.

In an embodiment the control module 18 is configured to control the wireless charging converter 16. For example, in an embodiment the control module 18 is configured to control the wireless charging converter to stop wireless charging when it is determined that the frequency of the AC signal output from the resonance module 11 is not within the first frequency range or the second frequency range.

Figures 6 and 7 show examples for the secondary coil 21. As shown in Figure 6, in an embodiment the secondary coil 21 has a rectangular shape and consists of a single layer. The secondary coil 21 may be of the wire-round type. In an embodiment the secondary coil 21 has a thickness of about 0.6mm, an outer length of about 44mm and an outer width of about 30mm.

As shown in Figure 7, in an alternative embodiment the secondary coil 21 has a circular shape and comprises multiple layers stacked together. The secondary coil 21 shown in Figure 7 may have two layers, a thickness of about 0.9mm and an outer diameter of about 32mm.

The coil designs shown in Figure 6 and Figure 7 are merely exemplary. Other coil signs are also possible having different shapes, different numbers of layers and different sizes.

Optionally, the frequency modulation module 12 is formed on a wireless charging chip. Optionally, the resonance module 11 is provided on the chip. Optionally, the wireless charging converter 16 is provided on the chip. When the rectifier 13 is provided, it may be provided on the chip. When the terminal charging management module 17 is provided, it may be provided on the chip. When the control module 18 is provided, it may be provided on the chip.

Merely as an example, the secondary coil 21 may have a self-inductance L_s of about 15μH when it is away from the base station and a self-inductance L′_s of about 20μH when placed on the interface surface of the power transmitter. For a resonant frequency f_s of 100 kHz, the first resonant capacitor Cs1 may be calculated to have a capacitance of about 127nF. Optionally, in order to calculate the capacitance of the second resonant capacitor Cs2, the resonant frequency is set to 277 kHz. This leads to a capacitance for the second resonant capacitor Cs2 of about 17nF. When the resonant detection capacitor Cd is provided, it may have a capacitance of about 1.6nF, for example. When the rectifier 13 is provided, it may have a low-pass filtering capacitance of 20μF.

According to the present invention, wireless charging can either be started immediately or after reducing the resonance frequency of the AC signal. The present invention makes it possible to establish a multi-mode wireless charging by providing the resonance module 11 and the frequency modulation module 12.

In an alternative embodiment, the power receiver 10 is configured to receive power according to three or more different standards (e.g. by having a capacitor for each standard and having a frequency adjuster that can adjust the frequency of each standard to be in the right frequency range for the wireless charging converter. For example, in an example the power receiver 10 is configured to receive power according to the WPC standard, the PMA standard and the A4WP standard. The frequency range of the A4WP standard is in the region of about 6.87MHz. The frequency of an AC signal for the A4WP standard could be reduced to correspond to the WPC standard or the PMA standard. However, efficiency would be lower because of the big difference between the frequency for the A4WP standard and the frequency for the WPC standard or the PMA standard.

Each of the resonance module 11 and the frequency modulation module 12 may be called a function unit. Furthermore, each of the rectifier 13, the frequency detector 14, the frequency adjuster 15, the wireless charging converter 16, the terminal charging management module 17 and the control module 18 may be called a function unit. In addition, each function unit in each embodiment of the disclosure may be integrated into one processing unit, or may also exist independently and physically, or two or more than two units may also be integrated into one unit. The integrated units may be implemented by hardware comprising circuitry, or may also be implemented by software function units (e.g. the functions of the control module 18 may be implemented in software) or by firmware or a combination of hardware and software. The units may be implemented as application specific circuitry or may be implemented using general purpose processing circuitry controlled by machine-readable instructions to perform the associated functions.

The integrated units, when implemented in the form of software function units and sold or used as independent products, may be stored in a computer-readable storage medium. For example, a software function unit stored in a computer-readable medium may perform the functions of the control module 18, e.g. determining when to switch the mode of the resonance module 11 and the frequency modulation module 12. The medium may be a transitory or a non-transitory machine readable medium. The transitory medium may be a transmission medium. Based on such understanding, the technical solutions of the disclosure, or the parts making a contribution to the art, may be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a plurality of instructions configured to enable a computer device (which may be a personal computer, server, network device or the like) or a processor to execute all or part of process elements of the method of each embodiment of the disclosure. The storage medium includes: various media capable of storing program codes such as a U disk, a mobile hard disk, a Read-Only Memory (ROM) , a Random Access Memory (RAM) , a magnetic disk, or a compact disc.

The above description is only of preferred embodiments of the invention and is not intended to limit the scope of protection beyond the definition of the invention in the claims. Variations and equivalent structures to the specific examples described above also fall within the scope of the claims.

Claims

A power receiver for wireless power transfer comprising:

a secondary coil；

a resonance module configured to operate in a first resonance mode in which the resonance module combines with the secondary coil to form a first resonant circuit having a first resonant frequency in a first frequency range and a second resonance mode in which the resonance module combines with the secondary coil to form a second resonant circuit having a second resonant frequency in a second frequency range, and for outputting an alternating current signal having a frequency in one of the first frequency range and the second frequency range；

a frequency modulation module comprising a frequency adjuster configured to modify an alternating current signal received from the resonance module and having a frequency in the second frequency range to produce an alternating current signal having a frequency within the first frequency range； and

a wireless charging converter configured to convert an alternating current signal having a frequency in the first frequency range received from the frequency modulation module into a direct current signal.
The power receiver of claim 1, wherein the frequency modulation module is configured to operate in a first modulation mode in which the frequency modulation module is configured to transfer an alternating current signal from the resonance module to the wireless charging converter bypassing the frequency adjuster and a second modulation mode in which the frequency modulation module is configured to transfer an alternating current signal from the resonance module to the wireless charging converter via the frequency adjuster.
The power receiver of claim 2, wherein the frequency modulation module comprises:

a frequency detector configured to detect a frequency of an alternating current signal received from the resonance module.
The power receiver of claim 3 wherein:

the frequency detector is configured to detect whether a frequency of an alternating current signal received from the resonance module is in the second frequency range； and

when the frequency detector detects that the frequency of the alternating current signal received from the resonance module is in the second frequency range, the resonance module is configured to operate in the second resonance mode and the frequency modulation module is configured to operate in the second modulation mode.
The power receiver of claim 3 or 4, wherein:

the frequency detector is configured to detect whether a frequency of an alternating current signal received from the resonance module is in the first frequency range； and

when the frequency detector detects that the frequency of the alternating current signal received from the resonance module is in the first frequency range, the resonance module is configured to operate in the first resonance mode and the frequency modulation module is configured to operate in the first modulation mode.
The power receiver of any of claims 3 to 5, wherein:

the frequency detector is configured to detect whether a frequency of an alternating current signal received from the resonance module is outside of both the first frequency range and the second frequency range； and

when the frequency detector detects that the frequency of the alternating current signal received from the resonance module is outside of both the first frequency range and the second frequency range, the wireless charging converter is configured to not convert an alternating current signal into a direct current signal；

optionally wherein when the frequency detector detects that the frequency of the alternating current signal received from the resonance module is outside of both the first frequency range and the second frequency range, the power receiver is configured to output an alarm signal.
The power receiver of any preceding claim, wherein:

the resonance module comprises a first resonant capacitor for a first frequency range and a second resonant capacitor for a second frequency range；

in the first resonance mode the first resonant capacitor combines with the secondary coil to form a first LC circuit as the first resonant circuit； and

in the second resonance mode the second resonant capacitor combines with the secondary coil to form a second LC circuit as the second resonant circuit.
The power receiver of any preceding claim, wherein the frequency adjuster is configured to reduce the frequency of the alternating current signal received from the resonance module.
The power receiver of any preceding claim, wherein:

the first frequency range is 100kHz to 205kHz； and/or

the second frequency range is 277kHz to 357kHz.
A terminal device comprising the power receiver of any of claims 1 to 9.
A method of receiving power by wireless power transfer comprising:

providing a secondary coil；

selectively operating a resonance module in one of a first resonance mode in which the resonance module combines with the secondary coil to form a first resonant circuit having a first resonant frequency in a first frequency range and a second resonance mode in which the resonance module combines with the secondary coil to form a second resonant circuit having a second resonant frequency in a second frequency range；

outputting an alternating current signal having a frequency in one of the first frequency range and the second frequency range from the resonance module；

receiving an alternating current signal from the resonance module at a frequency modulation module；

selectively operating a frequency adjuster of the frequency modulation module to modify an alternating current signal received from the resonance module and having a frequency in the second frequency range to produce an alternating current signal having a frequency within the first frequency range； and

converting an alternating current signal having a frequency in the first frequency range received from the frequency modulation module into a direct current signal.
The method of claim 11, wherein the frequency modulation module operates in a first modulation mode in which the frequency modulation module transfers an alternating current signal from the resonance module to the wireless charging converter bypassing the frequency adjuster and a second modulation mode in which the frequency modulation module transfers an alternating current signal from the resonance module to the wireless charging converter via the frequency adjuster.
The method of claim 12, comprising:

a frequency detector detecting a frequency of an alternating current signal received from the resonance module.
The method of claim 13 wherein:

the frequency detector detects whether a frequency of an alternating current signal received from the resonance module is in the second frequency range； and

when the frequency detector detects that the frequency of the alternating current signal received from the resonance module is in the second frequency range, the resonance module operates in the second resonance mode and the frequency modulation module operates in the second modulation mode.
The method of claim 13 or 14wherein:

the frequency detector detects whether a frequency of an alternating current signal received from the resonance module is in the first frequency range； and

when the frequency detector detects that the frequency of the alternating current signal received from the resonance module is in the first frequency range, the resonance module operates in the first resonance mode and the frequency modulation operates in the first modulation mode.
The method of any of claims 13 to 15, wherein:

the frequency detector detects whether a frequency of an alternating current signal received from the resonance module is outside of both the first frequency range and the second frequency range； and

when the frequency detector detects that the frequency of the alternating current signal received from the resonance module is outside of both the first frequency range and the second frequency range, the wireless charging converter does not convert an alternating current signal into a direct current signal；

optionally wherein when the frequency detector detects that the frequency of the alternating current signal received from the resonance module is outside of both the first frequency range and the second frequency range, the power receiver outputs an alarm signal.
The method of any of claims 11 to 16, wherein:

the resonance module comprises a first resonant capacitor for a first frequency range and a second resonant capacitor for a second frequency range；

in the first resonance mode the first resonant capacitor combines with the secondary coil to form a first LC circuit as the first resonant circuit； and

in the second resonance mode the second resonant capacitor combines with the secondary coil to form a second LC circuit as the second resonant circuit.
The method of any of claims 11 to 17, wherein the frequency adjuster reduces the frequency of the alternating current signal received from the resonance module.
The method of any of claims 11 to18, wherein:

the first frequency range is 100kHz to 205kHz； and/or

the second frequency range is 277kHz to 357kHz.
A method of charging a terminal device using the method of any of claims 11 to 19.