KR20180016831A - Wireless Power Control Method and Wireless Power Transmitter for Wireless Charging - Google Patents

Abstract

A wireless power transmitter for wirelessly transmitting power to a wireless power receiver according to an embodiment of the present invention includes a control part which determines whether or not the power transmission mode of the wireless power transmitter can be changed to a medium power mode based on information on the required power of the wireless power transmitter, when the wireless power receiver detects an overheating during a power transmission in accordance with a low power mode; and a voltage regulator which boosts the output voltage of a DC/DC converter and transmits the boosted output voltage to an inverter when the power transmission mode of the wireless power transmitter cannot be changed to a medium power mode.

Description

Technical Field [0001] The present invention relates to a wireless power control method and a wireless power transmitter for wireless charging,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless power transmission technique, and more particularly, to a wireless power control method and apparatus for wireless charging.

Recently, as the information and communication technology rapidly develops, a ubiquitous society based on information and communication technology is being made.

In order for information communication devices to be connected anytime and anywhere, sensors equipped with a computer chip having a communication function must be installed in all facilities of the society. Therefore, power supply problems of these devices and sensors are becoming a new challenge. In addition, mobile devices such as Bluetooth handsets and iPods, as well as mobile phones, have been rapidly increasing in number, and charging the battery has required users time and effort. As a way to solve this problem, wireless power transmission technology has recently attracted attention.

The wireless power transmission technology (wireless power transmission or wireless energy transfer) is a technology to transmit electric energy from the transmitter to the receiver wirelessly using the induction principle of the magnetic field. In the 1800s, electric motor or transformer And thereafter, a method of transmitting electrical energy by radiating electromagnetic waves such as high frequency, microwave, and laser has also been attempted. Our electric toothbrushes and some wireless shavers are actually charged with electromagnetic induction.

Up to the present, energy transmission using radio may be roughly classified into a magnetic induction method, an electromagnetic resonance method, and an RF transmission method using a short wavelength radio frequency.

In the magnetic induction method, when two coils are adjacent to each other and a current is supplied to one coil, a magnetic flux generated at this time causes an electromotive force to the other coils. As a technology, . The magnetic induction method has the disadvantage that it can transmit power of up to several hundred kilowatts (kW) and the efficiency is high, but the maximum transmission distance is 1 centimeter (cm) or less, so it is usually adjacent to the charger or the floor.

The self-resonance method is characterized by using an electric field or a magnetic field instead of using electromagnetic waves or currents. The self-resonance method is advantageous in that it is safe to other electronic devices or human body since it is hardly influenced by the electromagnetic wave problem. On the other hand, it can be used only at a limited distance and space, and has a disadvantage that energy transfer efficiency is somewhat low.

Short wavelength wireless power transmission - simply, RF transmission - takes advantage of the fact that energy can be transmitted and received directly in radio wave form. This technology is a RF power transmission system using a rectenna. Rectena is a combination of an antenna and a rectifier, which means a device that converts RF power directly into direct current power. That is, the RF method is a technique of converting an AC radio wave into DC and using it. Recently, as the efficiency has improved, commercialization has been actively researched.

Wireless power transmission technology can be applied not only to mobile, but also to various industries such as IT, railroad, and household appliance industry.

As a variety of devices are equipped with a wireless charging function and the intensity of power required by the wireless power receiving device is increased, a heating phenomenon may occur in the driving circuit and the transmission coil, and the device may be damaged.

In order to prevent a heat generation phenomenon, various heat dissipation structures (for example, a heat dissipation fan, a heat dissipation material, etc.) are installed in the wireless power transmission device and the wireless power reception device. However, There are limits to the mechanism limitations.

In particular, it is important to quickly dissipate the generated heat. However, it is important to minimize the heat generated in the control circuit board and the coil itself.

It is an object of the present invention to provide a wireless power control method and a wireless power transmitter for wireless charging.

Another object of the present invention is to provide a wireless power control method and a wireless power transmitter capable of minimizing heat generation without interruption of charging even when it is impossible to change the power transmission mode.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, unless further departing from the spirit and scope of the invention as defined by the appended claims. It will be possible.

The present invention can provide a wireless power control method for wireless charging and an apparatus therefor.

A method of wireless power control in a wireless power transmitter for wirelessly transmitting power to a wireless power receiver according to an exemplary embodiment of the present invention includes sensing a temperature of the wireless power receiver and detecting an overheating during a power transmission according to a low power mode ; Determining whether a power transmission mode of the wireless power transmitter can be changed to a medium power mode based on information on a required power of the wireless power receiver when an overheating is detected; Reducing the current in the transmit coil if the power transmission mode of the wireless power transmitter can not be changed to the non-power mode; And a step of boosting the output voltage of the DC / DC converter and transmitting the boosted voltage to the inverter when the current of the transmission coil reaches the threshold value and the overheat is sensed.

A wireless power transmitter that wirelessly transmits power to a wireless power receiver in accordance with an embodiment of the present invention includes a wireless power transmitter configured to wirelessly transmit power to the wireless power receiver when the wireless power receiver detects an overheating during a power transmission according to a low power mode, A controller for determining whether or not the power transmission mode of the wireless power transmitter can be changed to a medium power mode based on information on the power demanded by the receiver; And a voltage regulator for boosting the output voltage of the DC / DC converter and transmitting the output voltage to the inverter when the power transmission mode of the wireless power transmitter can not be changed to the non-power mode.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, And can be understood and understood.

Effects of the method, apparatus and system according to the present invention will be described as follows.

An advantage of the present invention is to provide a wireless power control method and apparatus capable of preventing a charge disconnection at the time of adjustment according to heat generation of a wireless power transmission apparatus.

The present invention can minimize the heat generation while maintaining the power transmission state without the occurrence of the charge disconnection even when the overheating occurs during the power transmission to the wireless power receiver supporting only the low power mode.

The effects obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description will be.

1 is a block diagram illustrating a wireless charging system according to an embodiment of the present invention.
2 is a block diagram illustrating a wireless charging system according to another embodiment of the present invention.
3 is a diagram for explaining a sensing signal transmission procedure in a wireless charging system according to an embodiment of the present invention.
4 is a state transition diagram for explaining the wireless power transmission procedure defined in the WPC standard.
5 is a state transition diagram for explaining a wireless power transmission procedure defined in the WPC (Qi) standard.
6 is a block diagram illustrating a structure of a wireless power transmitter according to an embodiment of the present invention.
7 is a block diagram illustrating a structure of a wireless power receiver interworking with the wireless power transmitter according to the FIG.
8 is a block diagram illustrating a voltage regulator of a wireless power transmitter according to an embodiment of the present invention.
9 is a circuit diagram showing a voltage regulator according to an embodiment of the present invention.
10 is a diagram for explaining the operation of the voltage regulator shown in FIG. 9 in the normal mode.
11 is a diagram for explaining the operation of the voltage regulator shown in Fig. 9 in the boost mode.
12 is a flowchart illustrating an operation of a wireless power transmitter according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an apparatus and various methods to which embodiments of the present invention are applied will be described in detail with reference to the drawings. The suffix "module" and " part "for the components used in the following description are given or mixed in consideration of ease of specification, and do not have their own meaning or role.

In the description of the embodiment, in the case where it is described as being formed "above" or "below" each element, the upper or lower (lower) And that at least one further component is formed and arranged between the two components. Also, in the case of "upper (upper) or lower (lower)", it may include not only an upward direction but also a downward direction based on one component.

In the description of the embodiments, an apparatus equipped with a function of transmitting wireless power on a wireless charging system includes a wireless power transmitter, a wireless power transmitter, a wireless power transmitter, a wireless power transmitter, a transmitter, a transmitter, , A transmitting side, a wireless power transmission device, a wireless power transmitter, and the like are used in combination. Further, for the sake of convenience of explanation, it is to be understood that a wireless power receiving apparatus, a wireless power receiving apparatus, a wireless power receiving apparatus, a wireless power receiving apparatus, a receiving terminal, a receiving side, A receiver, a receiver, and the like can be used in combination.

The transmitter according to the present invention may be configured as a pad type, a cradle type, an access point (AP) type, a small base type, a stand type, a ceiling embedded type, a wall type, Power can also be transmitted. To this end, the transmitter may comprise at least one radio power transmission means. Here, the radio power transmitting means may be various non-electric power transmission standards based on an electromagnetic induction method in which a magnetic field is generated in a power transmitting terminal coil and charged using an electromagnetic induction principle in which electricity is induced in a receiving terminal coil under the influence of the magnetic field. Here, the wireless power transmission means may include an electromagnetic induction wireless charging technique defined by Wireless Power Consortium (WPC) and Power Matters Alliance (PMA), which are standard wireless charging technologies.

Also, a receiver according to an embodiment of the present invention may include at least one wireless power receiving means, and may receive wireless power from two or more transmitters at the same time. Here, the wireless power receiving means may include an electromagnetic induction wireless charging technique defined by Wireless Power Consortium (WPC) and Power Matters Alliance (PMA), which are standard wireless charging technologies.

The receiver according to the present invention may be used in a mobile phone, a smart phone, a laptop computer, a digital broadcasting terminal, a PDA (Personal Digital Assistants), a PMP (Portable Multimedia Player), a navigation device, A portable electronic device such as a toothbrush, an electronic tag, a lighting device, a remote control, a fishing rod, a smart watch, etc. However, the present invention is not limited thereto. It suffices.

1 is a block diagram illustrating a wireless charging system according to an embodiment of the present invention.

Referring to FIG. 1, the wireless charging system includes a wireless power transmission terminal 10 for wirelessly transmitting power, a wireless power receiving terminal 20 for receiving the transmitted power, and an electronic device 30 Lt; / RTI >

For example, the wireless power transmitting terminal 10 and the wireless power receiving terminal 20 can perform in-band communication in which information is exchanged using the same frequency band as that used for wireless power transmission. In another example, the wireless power transmitting terminal 10 and the wireless power receiving terminal 20 perform out-of-band communication in which information is exchanged using a different frequency band different from the operating frequency used for wireless power transmission .

For example, information exchanged between the wireless power transmitting terminal 10 and the wireless power receiving terminal 20 may include control information as well as status information of each other. Here, the status information and the control information exchanged between the transmitting and receiving end will become more apparent through the description of the embodiments to be described later.

The in-band communication and the out-of-band communication may provide bidirectional communication, but the present invention is not limited thereto. In another embodiment, the in-band communication and the out-of-band communication may be provided.

 For example, the unidirectional communication may be that the wireless power receiving terminal 20 transmits information only to the wireless power transmitting terminal 10, but the present invention is not limited thereto, and the wireless power transmitting terminal 10 may transmit information Lt; / RTI >

In the half duplex communication mode, bidirectional communication is possible between the wireless power receiving terminal 20 and the wireless power transmitting terminal 10, but information can be transmitted only by any one device at any time.

The wireless power receiving terminal 20 according to an embodiment of the present invention may acquire various status information of the electronic device 30. [ For example, the status information of the electronic device 30 may include current power usage information, information for identifying a running application, CPU usage information, battery charge status information, battery output voltage / current information, And is information obtainable from the electronic device 30 and available for wireless power control.

In particular, the wireless power transmitting terminal 10 according to an embodiment of the present invention can transmit a predetermined packet indicating whether or not to support fast charging to the wireless power receiving terminal 20. The wireless power receiving terminal 20 can inform the electronic device 30 of the connected wireless power transmitting terminal 10 when it is confirmed that it supports the fast charging mode. The electronic device 30 may indicate that fast charging is possible through a predetermined display means, which may be, for example, a liquid crystal display.

Also, the user of the electronic device 30 may select the predetermined fast charge request button displayed on the liquid crystal display means to control the wireless power transmitting terminal 10 to operate in the fast charge mode. In this case, the electronic device 30 can transmit a predetermined fast charge request signal to the wireless power receiving terminal 20 when the quick charge request button is selected by the user. The wireless power receiving terminal 20 may generate a charging mode packet corresponding to the received fast charging request signal and transmit the same to the wireless power transmitting terminal 10 to switch the general low power charging mode to the fast charging mode.

2 is a block diagram illustrating a wireless charging system according to another embodiment of the present invention.

For example, as shown in 200a, the wireless power receiving terminal 20 may include a plurality of wireless power receiving devices, and a plurality of wireless power receiving devices may be connected to one wireless power transmitting terminal 10, Charging may also be performed. At this time, the wireless power transmitting terminal 10 can distribute power to a plurality of wireless power receiving apparatuses in a time division manner, but it is not limited thereto. In another example, the wireless power transmitting terminal 10 can distribute power to a plurality of wireless power receiving apparatuses using different frequency bands allocated to the wireless power receiving apparatuses.

At this time, the number of wireless power receiving apparatuses connectable to one wireless power transmitting apparatus 10 is set to at least one of the required power amount for each wireless power receiving apparatus, the battery charging state, the power consumption amount of the electronic apparatus, Can be determined adaptively based on

As another example, as shown in 200b, the wireless power transmitting terminal 10 may be composed of a plurality of wireless power transmitting apparatuses. In this case, the wireless power receiving terminal 20 may be connected to a plurality of wireless power transmission apparatuses at the same time, and may simultaneously receive power from connected wireless power transmission apparatuses to perform charging. At this time, the number of wireless power transmission apparatuses connected to the wireless power receiving terminal 20 is adaptively set based on the required power amount of the wireless power receiving terminal 20, the battery charging status, the power consumption amount of the electronic apparatus, Can be determined.

3 is a diagram for explaining a sensing signal transmission procedure in a wireless charging system according to an embodiment of the present invention.

As an example, the wireless power transmitter may be equipped with three transmit coils 111, 112, 113. Each transmit coil may overlap a portion of the transmit coil with a different transmit coil, and the wireless power transmitter may include a predetermined sense signal 117, 127 for sensing the presence of the wireless power receiver through each transmit coil - And sequentially transmits digital ping signals in a predefined order.

As shown in FIG. 3, the wireless power transmitter sequentially transmits the detection signal 117 through the primary sensing signal transmission procedure shown in reference numeral 110, and receives a signal strength indicator (Signal Strength Indicator 116 may identify the received transmit coil 111, 112. Subsequently, the wireless power transmitter sequentially transmits the detection signal 127 through the secondary detection signal transmission procedure shown in the reference numeral 120, and the signal strength indicator 126 is transmitted to the transmission coils 111 and 112 It is possible to control the efficiency (or charging efficiency) - that is, the state of alignment between the transmitting coil and the receiving coil - to identify a good transmitting coil and to allow power to be delivered through the identified transmitting coil, .

As shown in FIG. 3, the reason why the wireless power transmitter performs the two detection signal transmission procedures is to more accurately identify to which transmission coil the reception coil of the wireless power receiver is well aligned.

If the signal strength indicators 116 and 126 are received at the first transmission coil 111 and the second transmission coil 112 as shown in the aforementioned numerals 110 and 120 of FIG. 3, Selects a transmission coil having the best alignment based on the received signal strength indicator 126 in each of the first transmission coil 111 and the second transmission coil 112 and performs wireless charging using the selected transmission coil .

4 is a state transition diagram for explaining the wireless power transmission procedure defined in the WPC standard.

Referring to FIG. 4, power transmission from a transmitter to a receiver according to the WPC standard is largely divided into a selection phase 410, a ping phase 420, an identification and configuration phase 430, And a power transfer phase (step 440).

The selection step 410 may be a phase transition when a specific error or a specific event is detected while initiating a power transmission or maintaining a power transmission. Here, the specific error and the specific event will become clear through the following description. Also, in a selection step 410, the transmitter may monitor whether an object is present on the surface of the charging interface. If the transmitter detects that an object is placed on the charging interface surface, it can transition to the zipping step 420 (S401). In a selection step 410, the transmitter can transmit an analog ping signal of a very short pulse and, based on the change in current of the transmitting coil, It is possible to detect whether or not an object exists.

At step 420, when the transmitter senses an object, it activates (i.e., boot) the receiver and sends a Digital Ping to identify if the receiver is compatible with the WPC standard. If the transmitter does not receive a response signal for the digital ping (e.g., a signal strength indicator) from the receiver in step 420, then the transmitter may transition back to the selection step 410 (S402). Also, in step 420, the transmitter may transition to a selection step 410 when receiving a signal indicating completion of power transmission from the receiver, i.e., a charging completion signal (S403).

Once the ping step 420 is complete, the transmitter may transition to identification and configuration step 430 to identify the receiver and to collect receiver configuration and status information (S404).

In the identifying and configuring step 430, the sender may determine whether the packet is unexpected, whether a desired packet is received during a predefined period of time (time out), a packet transmission error (transmission error) (No power transfer contract), the process can be shifted to the selection step 410 (S405).

Once the identification and configuration for the receiver is complete, the transmitter may transition to power transfer step 440, which transmits the wireless power (S406).

In the power transfer step 440, the transmitter determines whether an unexpected packet is received, a desired packet is received for a predefined period of time (time out), a violation of a predetermined power transmission contract occurs transfer contract violation, and if the charging is completed, the selection step 410 can be performed (S407).

In addition, in the power transfer step 440, if the transmitter needs to reconfigure the power transfer contract according to changes in the transmitter state, etc., it may transition to the identification and configuration step 430 (S408).

The power transmission contract may be set based on the status and characteristic information of the transmitter and the receiver. For example, the transmitter status information may include information on the maximum amount of transmittable power, information on the maximum number of receivable receivers, and the receiver status information may include information on the requested power and the like.

5 is a state transition diagram for explaining a wireless power transmission procedure defined in the WPC (Qi) standard.

Referring to FIG. 5, power transmission from a transmitter to a receiver according to the WPC (Qi) standard is largely divided into a selection phase 510, a ping phase 520, an identification and configuration phase, 530, a negotiation phase 540, a calibration phase 550, a power transfer phase 560, and a renegotiation phase 570.

The selection step 510 may be a transition step, for example, S502, S504, S506, S509, S, when a specific error or a specific event is detected while initiating a power transmission or maintaining a power transmission. Here, the specific error and the specific event will become clear through the following description. Also, in a selection step 510, the transmitter can monitor whether an object is present on the interface surface. If the transmitter detects that an object has been placed on the interface surface, it may transition to a ping step 520. In the selection step 510, the transmitter transmits an analog ping signal of a very short pulse and, based on the current change of the transmission coil or the primary coil, It is possible to detect whether or not there is an error.

At step 520, the transmitter activates the receiver when an object is detected, and transmits a digital ping to identify whether the receiver is a WPC compliant receiver. If the transmitter does not receive a response signal to the digital ping (e. G., A signal strength packet) from the receiver in step 520, then the receiver may transition back to step 510 again. Also, in the step of the ping 520, the transmitter may transition to the selection step 510 upon receiving a signal indicating that the power transmission has been completed from the receiver, that is, the charge completion packet.

Once the ping step 520 is complete, the transmitter may transition to an identification and configuration step 530 for identifying the receiver and collecting receiver configuration and status information.

In the identifying and configuring step 530, the transmitter determines whether a packet is received (unexpected packet), a desired packet is not received during a predefined period of time (time out), a packet transmission error, (No power transfer contract) can be made to the selection step 510.

The transmitter may determine whether an entry to the negotiation step 540 is required based on the negotiation field value of the configuration packet that was made in the identification and configuration step 530. [

If it is determined that negotiation is required, the transmitter may enter negotiation step 540 and perform a predetermined FOD detection procedure.

On the other hand, if it is determined that negotiation is not required, the transmitter may immediately enter the power transmission step 560.

At negotiation step 540, the transmitter may receive a Foreign Object Detection (FOD) status packet including a reference quality factor value. At this time, the transmitter can determine a threshold for FO detection based on the reference quality factor value.

The transmitter can detect whether the FO exists in the charging area using the determined threshold value for FO detection and the currently measured quality factor value, and can control the power transmission according to the FO detection result. As an example, if FO is detected, power transmission may be interrupted, but is not limited thereto.

If FO is detected, the transmitter may return to selection step 510. If, on the other hand, no FO is detected, the transmitter may enter power transfer step 560 via calibration step 550. In detail, if the FO is not detected, the transmitter determines the strength of the power received at the receiving end in the correcting step 550 and determines the power loss at the receiving end and the transmitting end to determine the strength of the power transmitted at the transmitting end Can be measured. That is, the transmitter can predict the power loss based on the difference between the transmitting power of the transmitting end and the receiving power of the receiving end in the correcting step 550. A transmitter according to one embodiment may compensate the threshold for FOD detection by reflecting the predicted power loss.

In the power transfer step 560, the transmitter determines whether an unexpected packet is received, a desired packet is received for a predefined time (time out), a violation of a predetermined power transmission contract occurs transfer contract violation, and if the charging is completed, the selection step 510 can be performed.

Also, in the power transfer step 560, the transmitter may transition to the renegotiation step 570 if it is necessary to reconfigure the power transfer contract according to the transmitter state change or the like. At this time, if the renegotiation is normally completed, the transmitter may return to power transfer step 560. [

The power transmission contract may be set based on the status and characteristic information of the transmitter and the receiver. For example, the transmitter status information may include information on the maximum amount of transmittable power, information on the maximum number of receivable receivers, and the receiver status information may include information on the requested power and the like.

6 is a block diagram illustrating a structure of a wireless power transmitter according to an embodiment of the present invention.

6, the wireless power transmitter 600 may include a power conversion unit 610, a power transmission unit 620, a communication unit 630, a control unit 640, and a sensing unit 650 . It should be noted that the configuration of the wireless power transmitter 600 described above is not necessarily an essential configuration, and may be configured to include more or less components.

6, when the DC power is supplied from the power supply unit 660, the power converting unit 610 may convert the DC power into AC power having a predetermined intensity.

The power converter 610 may include a DC / DC converter 611, a voltage regulator 612, an inverter 613, and a frequency generator 613. Here, the inverter 613 may be a half bridge inverter or a full bridge inverter. However, the present invention is not limited to this, and a circuit configuration capable of converting DC power into AC power having a specific operating frequency is sufficient.

The DC / DC converting unit 611 may convert DC power supplied from the power supply unit 650 into DC power having a specific intensity according to a control signal of the controller 640. [

At this time, the sensing unit 650 may measure the voltage / current of the DC-converted power and provide the measured voltage / current to the controller 640. In addition, the sensing unit 650 may measure the internal temperature of the wireless power transmitter 600 and may provide the measurement result to the controller 640 in order to determine whether overheating occurs. For example, the control unit 640 may adaptively cut off the power supply from the power supply unit 650 or block the supply of power to the amplifier 612 based on the voltage / current value measured by the sensing unit 650 . To this end, a power cutoff circuit may be further provided at one side of the power conversion unit 610 to cut off power supplied from the power supply unit 650 or to cut off power supplied to the amplifier 612.

The voltage regulator 612 outputs the DC power of the specific intensity supplied from the DC / DC converter 611 as it is according to the control signal of the controller 640, or outputs the DC power that is boosted to DC power of another intensity have. The detailed configuration and operation of the voltage regulator 612 will be described later with reference to FIGS. 8 to 12. FIG.

The inverter 613 can convert the DC power output from the voltage regulator 612 to AC power based on the reference AC signal generated by the frequency generator 614. [ At this time, the frequency of the reference AC signal - that is, the operating frequency - can be dynamically changed according to the control signal of the controller 640. The wireless power transmitter 600 according to an exemplary embodiment of the present invention may adjust the operating frequency to adjust the intensity of the transmitted power. For example, the control unit 640 may receive the power reception status information and / or the power control signal of the wireless power receiver through the communication unit 630 and may receive the power control information based on the received power reception status information and / To determine the operating frequency, and to dynamically control the frequency generator 614 to produce the determined operating frequency. For example, the power reception status information may include, but is not limited to, the intensity information of the rectifier output voltage, the intensity information of the current applied to the reception coil, and the like. The power control signal may include a signal for requesting power increase, a signal for requesting power reduction, and the like.

The power transmitting unit 620 may be configured to include a multiplexer 621 (or a multiplexer), a transmitting coil unit 622, and the like. Here, the transmission coil section 622 may be composed of first to n-th transmission coils. In addition, the power transmitting unit 620 may further include a carrier generator (not shown) for generating a specific carrier frequency for power transmission. In this case, the carrier generator may generate a specific carrier frequency for mixing with the output AC power of the inverter 613 transmitted through the multiplexer 621. It should be noted that one embodiment of the present invention may have different frequencies of AC power delivered to each transmit coil. In another embodiment of the present invention, the resonance frequencies of the respective transmission coils may be set differently by using a predetermined frequency controller provided with a function of controlling LC resonance characteristics for different transmission coils.

The multiplexer 621 may perform a switch function to transmit AC power to the transmission coil selected by the controller 640. [ The controller 640 may select a transmission coil to be used for power transmission to the corresponding wireless power receiver based on the signal strength indicator received for each transmission coil.

The controller 640 according to an exemplary embodiment of the present invention may transmit power through time division multiplexing for each transmission coil when a plurality of wireless power receivers are connected. For example, if the wireless power transmitter 600 has three wireless power receivers-i. E., The first through third wireless power receivers, respectively, identified through three different transmit coils, i. E., First through third transmit coils , The control unit 640 controls the multiplexer 621 to control the AC power to be transmitted only through a specific transmission coil in a specific time slot. At this time, the amount of power transmitted to the corresponding wireless power receiver can be controlled according to the length of the time slot allocated for each transmission coil, but this is only one embodiment. DC power of the DC / DC converter 611 to control the transmission power of each wireless power receiver.

The control unit 640 may control the multiplexer 621 so that the detection signals may be sequentially transmitted through the first through n'th transmission coils 622 during the first detection signal transmission procedure. At this time, the control unit 640 can identify the time at which the detection signal is transmitted using the timer 655. When the time of the transmission of the trashed signal arrives, the control unit 640 controls the multiplexer 621 to output a detection signal It can be controlled to be transmitted. For example, the timer 650 can transmit a specific event signal to the control unit 640 at predetermined intervals during the ping transmission step. The control unit 640 controls the multiplexer 621 every time the corresponding event signal is detected So that the digital ping can be transmitted through the corresponding transmission coil.

In addition, the control unit 640 may transmit a predetermined transmission coil identifier for identifying a signal strength indicator (Signal Strength Indicator) through a transmission coil from the demodulation unit 632 during the first detection signal transmission procedure, Lt; / RTI > received signal strength indicator. In the second sensing signal sending process, the controller 640 controls the multiplexer 621 so that the sensing signal can be transmitted only through the transmitting coil (s) on which the signal strength indicator is received during the first sensing signal sending procedure You may. In another example, when there are a plurality of transmit coils in which the signal strength indicator is received during the first differential sense signal transmission procedure, the control unit 640 transmits the received transmit coil with the signal strength indicator having the largest value as the second differential sense signal In the procedure, the detection signal may be determined as a transmission coil to be transmitted first, and the multiplexer 621 may be controlled according to the determination result.

The communication unit 630 may include at least one of a modulation unit 631 and a demodulation unit 632.

The modulator 631 may modulate the control signal generated by the controller 640 and transmit the modulated control signal to the multiplexer 621. Here, the modulation scheme for modulating the control signal includes a frequency shift keying (FSK) modulation scheme, a Manchester coding modulation scheme, a phase shift keying (PSK) modulation scheme, a pulse width modulation scheme, A differential bi-phase modulation method, and the like.

The demodulator 632 can demodulate the detected signal and transmit the demodulated signal to the controller 640 when a signal received through the transmission coil is detected. Here, the demodulated signal may include a signal strength indicator, an error correction (EC) indicator for power control during wireless power transmission, an end of charge indicator (EOC), an overvoltage / overcurrent / overheat indicator, But is not limited to, various status information for identifying the status of the wireless power receiver.

Also, the demodulator 632 can identify which of the transmit coils the demodulated signal is received, and provide the control unit 640 with a predetermined transmit coil identifier corresponding to the identified transmit coil.

 The demodulation unit 632 can demodulate the signal received through the transmission coil 623 and transmit the demodulated signal to the control unit 640. In one example, the demodulated signal may include, but is not limited to, a signal strength indicator, and the demodulated signal may include various status information of the wireless power receiver.

In one example, the wireless power transmitter 600 may obtain the signal strength indicator through in-band communication that uses the same frequency used for wireless power transmission to communicate with the wireless power receiver.

In addition, the wireless power transmitter 600 may transmit wireless power using the transmit coil portion 622, as well as exchange various control signals and status information with the wireless power receiver via the transmit coil portion 622 . As another example, a separate coil corresponding to each of the first to n-th transmission coils of the transmission coil section 622 may be additionally provided in the wireless power transmitter 600, and wireless power It should be noted that it may also perform in-band communication with the receiver.

Although the wireless power transmitter 600 and the wireless power receiver perform in-band communication in the description of FIG. 6, this is merely an example, and the frequency band used for the wireless power signal transmission Directional communication through different frequency bands. For example, the near-end bi-directional communication may be any one of low-power Bluetooth communication, RFID communication, UWB communication, and Zigbee communication.

6, the power transmission unit 620 of the wireless power transmitter 600 includes a multiplexer 621 and a plurality of transmission coils 622, but this is only one embodiment, It should be noted that the power transmission unit 620 according to the embodiment may be composed of one transmission coil.

7 is a block diagram illustrating a structure of a wireless power receiver interworking with the wireless power transmitter according to the FIG.

7, the wireless power receiver 700 includes a receiving coil 710, a rectifier 720, a DC / DC converter 730, a load 740, a sensing unit 750, 760, and a main control unit 770. Here, the communication unit 760 may include at least one of a demodulation unit 761 and a modulation unit 762.

Although the wireless power receiver 700 shown in the example of FIG. 7 is shown as being capable of exchanging information with the wireless power transmitter 600 through in-band communication, this is only one embodiment, The communication unit 760 according to another embodiment of the present invention may provide short-distance bidirectional communication through a frequency band different from the frequency band used for wireless power signal transmission.

AC power received through the receiving coil 710 may be transmitted to the rectifying unit 720. [ The rectifier 720 may convert the AC power to DC power and transmit it to the DC / DC converter 730. [ The DC / DC converter 730 may convert the intensity of the rectifier output DC power to a specific intensity required by the load 740 and then forward it to the load 740.

The sensing unit 750 may measure the intensity of the DC power output from the rectifier 720 and provide it to the main control unit 770. Also, the sensing unit 750 may measure the intensity of the current applied to the reception coil 710 according to the wireless power reception, and may transmit the measurement result to the main control unit 770. The sensing unit 750 may measure the internal temperature of the wireless power receiver 700 and provide the measured temperature value to the main control unit 770.

For example, the main control unit 770 may compare the measured rectifier output DC power with a predetermined reference value to determine whether an overvoltage is generated. As a result of the determination, if an overvoltage is generated, a predetermined packet indicating that the overvoltage has occurred can be generated and transmitted to the modulating unit 762. Here, the signal modulated by the modulating unit 762 may be transmitted to the wireless power transmitter 600 through the receiving coil 710 or a separate coil (not shown). The main control unit 770 may determine that the detection signal is received when the intensity of the rectifier output DC power is equal to or greater than a predetermined reference value and when the signal strength indicator corresponding to the detection signal is received by the modulation unit 762 To be transmitted to the wireless power transmitter 600 via the wireless network. The demodulation unit 761 demodulates the AC power signal between the reception coil 710 and the rectifier 720 or the DC power signal output from the rectifier 720 to identify whether or not the detection signal is received, (770). At this time, the main control unit 770 may control the signal intensity indicator corresponding to the detection signal to be transmitted through the modulation unit 762. [

8 is a block diagram illustrating a voltage regulator of a wireless power transmitter according to an embodiment of the present invention.

8, the voltage regulator 820 of the wireless power transmitter 800 is implemented between the DC / DC converter 810 and the inverter 830 and controls the DC voltage output from the DC / (840) according to the mode selection signal (SEL) of the inverter (840). The DC / DC converter 810, the voltage regulator 820, the inverter 830 and the control unit 840 are respectively connected to the DC / DC converter 611, the voltage regulator 612, the inverter 613, (640).

The control unit 840 may receive the result of measuring the internal temperature of the wireless power transmitter 800 from the sensing unit 650 and determine whether the wireless power transmitter 800 is overheated. In addition, the controller 840 may determine whether overheating of the wireless power receiver occurs from an over-temperature indicator received from the wireless power receiver. The controller 840 may change the power transmission mode when it is determined that the wireless power transmitter 800 or the wireless power receiver has overheated.

Here, the power transmission mode may include a low power mode and a medium power mode, and the < RTI ID = 0.0 > medium power mode < / RTI & It means the mode that can transmit.

The wireless power receiver may be determined to support a particular power transmission mode and the specific power transmission mode may be determined according to information about the required power of the wireless power receiver indicating the power required for the wireless power receiver. For example, a device such as a notebook with a high demand power can support both a low power mode that receives high power and a low power mode that receives low power. As another example, a particular smartphone with a low demand power may support only a low power mode without supporting a low power mode.

The inverter 830 may include a half bridge inverter and / or a full bridge inverter. The controller 840 can dynamically determine whether to drive the half bridge inverter or the full bridge inverter according to the power transmission mode determined according to the required power of the wireless power receiver. For example, if the wireless power receiver requires a low power of 5 W, the controller 840 may determine the power transmission mode to be a low power mode and control the half bridge circuit of the inverter 840 to be driven. On the other hand, if the wireless power receiver requires a high power of 15 W, the controller 840 may determine the power transmission mode to be a mid-power mode and control the full bridge circuit of the inverter 830 to be driven.

This is because the voltage range of the half bridge circuit (for example, 0 to VDD (V)) is narrower than the voltage range of the full bridge circuit (for example, -VDD (V) to VDD (V)) and the full bridge circuit is connected to the half bridge circuit As compared to the same current.

If the control unit 840 determines that the wireless power transmitter 800 or the wireless power receiver has overheated when the current power transmission mode is the low power mode, the controller 840 sets the power transmission mode to the mid power Mode. Since the heat of the wireless power transmitter or the wireless power receiver depends on the current flowing in the transmitting coil or the receiving coil, the current flowing to the transmitting coil or the receiving coil must be reduced in order to reduce heat generation. However, in order to lower the current flowing to the transmission coil or the reception coil while maintaining the power transmitted by the wireless power transmitter 800, the controller 840 controls the current power You can change the transfer mode.

The control unit 840 can control the full bridge circuit of the inverter 830 to be driven according to the low power mode and the reduced power (for example, 1/2) while the wireless power transmitter 800 transmits the same power, Lt; / RTI > This allows a reduced current to flow in the receive coil of the wireless power receiver.

If the wireless power receiver does not support the non-power mode according to the information on the power demanded by the receiver, the controller 840 changes the power transmission mode to change the currents of the transmission coil and the reception coil, Can not be reduced. Accordingly, the control unit 840 can reduce the currents of the transmission coil and the reception coil by adjusting the impedance of the resonance circuit connected to the inductor 830. [

The resonance circuit is a circuit for realizing resonance by connecting an inductor and a capacitor in series or in parallel. Here, the inductor may mean a transmitting coil. In the case of a series resonance circuit in which an inductor and a capacitor are connected in series, the intensity IR of the current flowing in the resonance circuit is inversely proportional to the inductance value RL of the inductor, i.e., the transmission coil, It is proportional to the amplitude (EV). That is, IR = EV / RL. Accordingly, when overheating occurs, the control unit 840 can control the inductance value of the resonance circuit to be increased. In this case, if the inductance value of the resonance circuit is increased, the overall impedance of the resonance circuit is increased, and the current flowing in the resonance circuit is reduced.

The resonance circuit may include an impedance adjustment circuit for adjusting the overall impedance value of the resonance circuit in accordance with a predetermined control signal of the controller 840. In one example, the impedance adjustment circuit may comprise a switch and an inductor. Here, the number of switches and inductors may differ depending on the design of the impedance adjustment unit and the adjustment range.

That is, when the wireless power receiver is a receiver that does not support the low power mode, the controller 840 can reduce the currents of the transmitting coil and the receiving coil by adjusting the impedance of the resonant circuit through the impedance adjusting circuit.

However, if the current in the transmit coil is reduced, the power output through the transmit coil will decrease together, and if the power received by the wireless power receiver drops below a certain power, the wireless power receiver will violate the pre- It can be judged that it is a power transfer contract violation. In this case, the wireless power receiver enters the selection phase from the power transfer phase, and the wireless power transmitter 800 also stops power delivery.

That is, wireless charging may be interrupted for a wireless power receiver supporting only a low power mode when an overheating occurs. However, this phenomenon can be prevented by the wireless power transmitter 800 including the voltage regulator 820 according to an embodiment of the present invention.

The voltage regulator 820 may include a voltage transfer circuit 821 and a boost converter 822.

Each of the voltage transfer circuit 821 and the boost converter 822 can be activated or deactivated according to the mode selection signal SEL and the mode selection signal SEL is a signal for selecting the mode of the voltage regulator 820. [

The voltage regulator 820 may operate in either a normal mode or a boost mode. The boost mode refers to a mode in which the voltage applied to the inverter 830 is stepped up to prevent the disconnection of the charger when the current of the transmission coil is reduced due to overheating during operation of the wireless power transmitter in the low power mode. That is, when the wireless power receiver supports only the low power mode, the controller 840 increases the voltage range of the half bridge circuit by boosting the voltage applied to the inverter 830 (VDD-> VDD '; VDD <VDD' (0 to VDD (V) - > 0 to VDD '(V)), it is possible to prevent a decrease in the transmission power due to the decrease in the current of the transmission coil.

The normal mode may mean an operation mode in a time domain except for the boost mode.

According to one embodiment, the control unit 840 can reduce the current of the transmission coil step by step when the overheat occurs, and even if the current of the transmission coil reaches a predetermined threshold value (a current at which the occurrence of the charge-breaking phenomenon may occur) It is possible to operate the voltage regulator 820 in the boost mode before further reducing the current of the transmission coil.

According to another embodiment, the controller 840 can reduce the current of the transmission coil to a predetermined threshold value (a current that can cause the occurrence of a charge disconnection phenomenon) at the time of occurrence of overheating, and even if the predetermined threshold is reached, The voltage regulator 820 can be operated in the boost mode before further reducing the current of the transmission coil.

The voltage transfer circuit 821 is activated in accordance with the mode selection signal SEL indicating the normal mode and the activated voltage transfer circuit 821 can transfer the output voltage of the DC / DC converter 810 directly to the inverter 830 have.

The voltage transfer circuit 821 is deactivated in accordance with the mode selection signal SEL indicating the boost mode and the deactivated voltage transfer circuit 821 is controlled such that the output voltage of the DC / DC converter 810 is not transmitted to the inverter 830 Can be blocked.

The boost converter 822 is activated in accordance with the mode selection signal SEL indicating the boost mode and the activated boost converter 822 boosts the output voltage of the DC / DC converter 810 and outputs the boosted voltage to the inverter 830. [ .

The boost converter 822 is deactivated in accordance with the mode selection signal SEL indicating the normal mode and the deactivated boost converter 822 may not perform the boost operation with respect to the output voltage of the DC / DC converter 810. [

According to the wireless power transmitter 800 according to the embodiment of the present invention, even when a wireless power receiver that supports only a low power mode generates overheating during power transmission, the heat can be minimized while maintaining the power transmission state have.

9 is a circuit diagram showing a voltage regulator according to an embodiment of the present invention. 10 is a diagram for explaining the operation of the voltage regulator shown in FIG. 9 in the normal mode. 11 is a diagram for explaining the operation of the voltage regulator shown in Fig. 9 in the boost mode.

9-11, a wireless power transmitter 900 illustrates one embodiment of the configuration of the wireless power transmitter 800 shown in FIG.

The DC / DC converter 910 is shown as one DC voltage source in terms of the voltage regulator 920.

The voltage regulator 920 may be implemented in a circuit configuration as shown in FIG. 9, but the scope of the present invention is not limited thereto.

The voltage regulator 920 may include a voltage transfer circuit 921 and a boost converter 922.

The voltage transfer circuit 921 may include a first power transistor Px1 and a second power transistor Px2 connected between the DC / DC converter 910 and the inverter 930. The first power transistor Px1 may be a PNP transistor and the second power transistor Px2 may be an NPN transistor. Each of the first power transistor Px1 and the second power transistor Px2 is connected to the gate input of the mode selection signal SEL and the mode selection signal SEL is inverted by the inverter 925, Lt; / RTI &gt;

The boost converter 922 includes a first switch SW1, a first inductor L1, a first diode D1, a first capacitor C1, a third power transistor Px3) and a PWM (Power Width Modulation) signal generator operating in accordance with the inverted mode selection signal SEL_b. The inverted mode selection signal SEL_b is a signal having a phase opposite to that of the mode selection signal SEL_b and can be generated by the inverter 925 which inverts the mode selection signal SEL.

The third power transistor Px3 may be implemented as a PNP type transistor. The PWM signal generator may be activated according to the inversion mode selection signal SEL_b to generate a PWM signal having a phase, frequency, and duty rate determined in accordance with the control of the controller 840.

The inverter 930 is connected to the voltage regulator 920 and can operate by receiving the output voltage Vout.

10, it is assumed that the voltage regulator 920 receives a first level (e.g., high level) mode selection signal SEL indicating normal mode operation.

The first switch SW1 of the boost converter 922 is turned off to receive the second level (e.g., low level) inversion mode selection signal SEL_b. As a result, no current flows into the boost converter 922, so that the boost converter 922 does not operate as shown in FIG.

When the mode selection signal SEL of the first level is applied to the voltage transfer circuit 921, the first power transistor Px1 and the second power transistor Px2 turn on and flow current, respectively. Assuming that the voltage drop due to the first power transistor Px1 and the second power transistor Px2 is neglected, the output voltage Vout becomes equal to the output voltage Vdc of the DC / DC converter 910. [

That is, when the voltage regulator 920 receives the first level (e.g., high level) mode selection signal SEL indicating normal mode operation, the voltage regulator 920 outputs the output voltage of the DC / DC converter 910 It can be output to the inverter 930 as it is.

11, it is assumed that the voltage regulator 920 receives a second level (e.g., low level) mode selection signal SEL indicating the boost mode operation.

When the mode selection signal SEL of the second level is applied to the voltage transfer circuit 921, the first power transistor Px1 and the second power transistor Px2 are turned off, do. The first power transistor Px1 to the second power transistor Px2 and the second power transistor Px2 from the diode inside each of the first power transistor Px1 and the second power transistor Px2 The current does not flow to the first power transistor Px1, so that the voltage transfer circuit 921 does not operate as shown in Fig.

The first switch SW1 of the boost converter 922 is turned on to receive the inverted mode selection signal SEL_b of the first level (e.g., high level). Accordingly, current flows into the boost converter 922, and the PWM signal generator is also activated to generate the PWM signal having the first duty ratio.

The third power transistor Px3 is turned on at the high level of the PWM signal and the current flows from the DC / DC converter 910 to the first inductor L1 so that the first inductor L1 Energy is accumulated. At this time, the first diode D1 becomes a reverse bias and is turned off.

The third power transistor Px3 is turned off at the low level of the PWM signal and the energy stored in the first inductor L1 through the first diode D1 in the on state can be accumulated in the first capacitor C1 .

This operation is repeated with the switching period as one cycle, and the output voltage Vout may have a relation of Vdc, which is the output voltage of the DC / DC converter 910, and Vout = Vdc / (1-D). Here, D means a duty ratio (a time ratio of a high level during one period).

The control unit 840 can deliver the output voltage Vout of a certain level to the inverter 930 by adjusting the duty ratio. For example, the control unit 840 may control the boost converter 922 to boost the 12V Vdc to 14V, but the scope of the present invention is not limited thereto. The specific level may be determined based on information on the required power of the wireless power receiver and the current of the transmitting coil.

That is, when the voltage regulator 920 receives the second level (e.g., low level) mode selection signal SEL indicating the boost mode operation, the voltage regulator 920 outputs the output voltage of the DC / DC converter 910 It is possible to increase the voltage by a predetermined ratio and output it to the inverter 930.

12 is a flowchart illustrating an operation of a wireless power transmitter according to an embodiment of the present invention.

Referring to FIG. 12, the wireless power transmitter 800 may enter a power transmission stage and transmit power to a wireless power receiver in a low power mode (S1201).

The controller 840 may sense whether a temperature sensing result in the wireless power transmitter 800 or an overheat indication is generated from the overheat indicator of the wireless power receiver (S1202).

The controller 840 may determine whether the power transmission mode of the wireless power transmitter can be changed to the non-power mode based on the information about the required power of the wireless power receiver (S1203).

If the wireless power receiver is a device supporting the &lt; RTI ID = 0.0 &gt; non-powered mode &lt; / RTI &gt; according to information on the required power of the wireless power receiver, the controller 840 may transmit power by changing the power transmission mode of the wireless power transmitter to the & (S1204). At this time, the operation of the half bridge inverter of the inverter 830 is stopped and the full bridge inverter can be driven.

If the wireless power receiver does not support the mid-power mode according to the information about the required power of the wireless power receiver, the controller 840 controls the impedance of the resonant circuit connected to the inductor 830, (S1205).

If the overheat phenomenon is not solved even when the current of the transmission coil reaches a predetermined threshold value, the control unit 840 operates the voltage regulator 820 in the boost mode to boost the voltage applied to the inverter, (S1206).

The methods according to the above-described embodiments may be implemented as a program for execution in a computer and stored in a computer-readable recording medium. Examples of the computer-readable recording medium include ROM, RAM, CD- , A floppy disk, an optical data storage device, and the like, and may also be implemented in the form of a carrier wave (for example, transmission over the Internet).

The computer readable recording medium may be distributed over a networked computer system so that computer readable code can be stored and executed in a distributed manner. And, functional program, code, and code segments for implementing the above-described method can be easily inferred by programmers in the technical field to which the embodiment belongs.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof.

Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention.

Claims (13)

A method of wireless power control in a wireless power transmitter for wirelessly transmitting power to a wireless power receiver,
Sensing overheating during power transmission in accordance with a low power mode with the wireless power receiver;
Determining whether a power transmission mode of the wireless power transmitter can be changed to a medium power mode based on information on a required power of the wireless power receiver when an overheating is detected;
Reducing the current in the transmit coil if the power transmission mode of the wireless power transmitter can not be changed to the non-power mode; And
And boosting the output voltage of the DC / DC converter and transmitting the boosted voltage to the inverter when the current of the transmission coil reaches the threshold value and the overheat is sensed. The method according to claim 1,
The method of claim 1,
Detecting overheating in accordance with a result of sensing the temperature in the wireless power transmitter or an overheat indicator received from the wireless power receiver. The method according to claim 1,
Wherein the step of reducing the current of the transmitting coil comprises:
And reducing the current of the transmitting coil by adjusting the impedance of the resonant circuit including the transmitting coil. The method according to claim 1,
Further comprising the step of driving a full bridge circuit of the inverter when the power transmission mode of the wireless power transmitter can be changed to the non-power mode. A wireless power transmitter for wirelessly transmitting power to a wireless power receiver,
The power transmission mode of the wireless power transmitter to the power mode of the wireless power transmitter based on information on the power demand of the wireless power receiver when the wireless power receiver detects an overheating during power transmission according to a low power mode, a medium power mode); And
And a voltage regulator that boosts the output voltage of the DC / DC converter and transfers it to the inverter when the power transmission mode of the wireless power transmitter can not be changed to the non-power mode. 6. The method of claim 5,
Wherein the control unit reduces the current of the transmitting coil by adjusting the impedance of the resonant circuit including the transmitting coil when the power transmission mode of the wireless power transmitter can not be changed to the non-powered mode. The method according to claim 6,
Wherein the controller operates the voltage regulator in a boost mode when an overheat is detected even when the current of the transmission coil reaches a threshold value. 8. The method of claim 7,
The voltage regulator includes:
A voltage transfer circuit for transmitting an output voltage of the DC / DC converter to the inverter in a normal mode other than the boost mode; And
And a boost converter for boosting the output voltage of the DC / DC converter in the boost mode and delivering it to the inverter. 9. The method of claim 8,
The voltage transfer circuit includes:
And a first power transistor and a second power transistor, each of which is turned on by the mode selection signal of the control unit in the normal mode. 9. The method of claim 8,
The boost converter includes:
A PWM signal generator activated by a mode selection signal of the controller to generate a PWM signal; And
And a third power transistor that is switched in accordance with the duty ratio of the PWM signal to step up the output voltage of the DC / DC converter. 11. The method of claim 10,
Wherein the duty ratio determines a rate of stepping up the output voltage of the DC / DC converter. 6. The method of claim 5,
Wherein the controller detects an overheating in accordance with a result of sensing a temperature in the wireless power transmitter or an overheat indicator received from the wireless power receiver. 6. The method of claim 5,
Wherein the control unit drives the full bridge circuit of the inverter when the power transmission mode of the wireless power transmitter can be changed to the non-power mode.

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