KR20230011607A - Apparatus and method for transmitting power wirelessly - Google Patents

Abstract

The present invention relates to a wireless power transmission method and device. The wireless power transmission method according to an embodiment of the present invention may comprise the steps of: transmitting power to a receiving device wirelessly; detecting a resonance frequency and Q value of a resonance circuit included in a transmitting device as a Q factor while transmitting power; and continuing or stopping a power transmission operation based on comparison of a position of the detected Q factor and a foreign object boundary curve in a plane with the frequency and the Q value as two axes. The power transmission operation may be continued or stopped according to whether the position of the Q factor is in a first area with a foreign object or a second area without the foreign object based on the foreign object boundary curve. When the position of the Q factor is within the first area, the distance between the Q factor and the foreign object boundary curve is calculated, wherein when the distance is greater than the first value, the power transmission operation stops but when the distance is less than the first value, the power transmission operation continues. In addition, when the position of the Q factor is within the second area, the power transmission operation may continue. Accordingly, it can be effectively determined whether a metallic foreign object is on the transmitting device or between the transmitting device and the receiving device.

Description

Wireless power transmission apparatus and method {Apparatus and method for transmitting power wirelessly}

The present invention relates to an apparatus and method for wirelessly transmitting power, and more particularly, to a method for effectively detecting a foreign object interposed between a receiving apparatus and the like.

With the development of communication and information processing technology, the use of smart terminals such as smart phones is gradually increasing. The current charging method, which is widely applied to smart terminals, supplies external power by directly connecting an adapter connected to a power source to the smart terminal. It is a method of charging by receiving USB power from the host by connecting it to a smart terminal through the USB terminal of the host.

Recently, in order to reduce the inconvenience of directly connecting the smart terminal to an adapter or a host through a connection line, a wireless charging method for wirelessly charging a battery using magnetic coupling without electrical contact is gradually being applied to smart terminals. .

There are several methods for wirelessly supplying or receiving electrical energy. Representatively, an inductive coupling method based on electromagnetic induction and a resonant coupling method based on an electromagnetic resonance phenomenon by a wireless power signal of a specific frequency There is a method of coupling.

In both methods, a communication channel is formed between an electronic device such as a wireless charging device and a smart terminal to exchange data, thereby ensuring stability of power transmission and increasing transmission efficiency. The inductive coupling method has a problem in that the power receiving device moves while power is transmitted wirelessly, thereby reducing transmission efficiency, and the resonant coupling method has a problem in that power transmission is stopped due to noise in a communication channel.

When there is a metal foreign object such as a coin between the transmitting device and the receiving device, power loss occurs and when the wireless transmission power is concentrated on the metal foreign object, there is a risk of overheating, which hinders stable power transmission. Therefore, a foreign object detection (FOD) function capable of detecting whether or not a metal foreign object is placed in a transmission device is necessarily implemented in a product to which the wireless charging standard of the inductive coupling method is applied.

A technique for determining whether the power difference is greater than or equal to a predetermined value by detecting the difference between the transmit power and the receive power, or the Q-Factor at the resonant frequency of the transmit coil measured while transmitting the power and transmitted by the receiving device A technique of comparing the Q factor to be used is generally used to detect metal contaminants.

However, in the latter case, there is a problem that is not applicable to a receiving device in which the Q factor is not stored. In addition, if the size of a metal material such as a clip is small or there is a foreign material in the case of a power receiving device, for example, a smart phone, the wireless charger may not detect it, and in this case, charging efficiency may decrease and heat may be generated. there is.

The present invention has been made in consideration of such a situation, and an object of the present invention is to provide a method for effectively determining whether or not a foreign substance is present between a transmitting device and a receiving device.

A wireless power transmission method according to an embodiment of the present invention for realizing the above object includes wirelessly transmitting power to a receiving device; Detecting a resonant frequency and a Q value of a resonant circuit included in a transmission device as a Q factor while transmitting power; and continuing the power transmission operation or stopping the power transmission operation based on a comparison between the detected Q factor position and the foreign matter boundary curve in a plane having the frequency and the Q value as two axes.

A wireless power transmission device according to another embodiment of the present invention includes a resonant circuit including a primary coil for transmitting power by magnetic induction coupling between an inverter for converting direct current power into alternating current and a secondary coil of a receiving device. Power conversion unit comprising a; a Q factor detector for detecting a resonance frequency and a Q value of the resonance circuit as a Q factor; and controlling the Q factor detection unit to detect the Q factor during power transmission, and continuing the power transmission operation based on the comparison between the detected position of the Q factor and the foreign matter boundary curve in a plane of which the frequency and the Q value are two axes. It is characterized in that it is configured to include a control unit for controlling the power conversion unit to stop the power transmission operation.

Therefore, it is possible to effectively determine whether a metal foreign substance is on the transmission device or between the transmission device and the reception device, and to prevent the risk of excessive heat generation and fire caused by concentration of output on the metal foreign substance during wireless power transmission. there is.

1 conceptually shows that power is wirelessly transmitted from a wireless power transmission device to an electronic device;
2 conceptually illustrates a circuit configuration of a power conversion unit of a transmission module for wirelessly transmitting power by an electromagnetic induction method;
3 shows a configuration for exchanging power and messages between a wireless power transmission module and a reception module;
4 shows a loop for controlling power transmission between a wireless power transmission module and a reception module in blocks;
5 shows a graph of a circuit for detecting a Q factor using a ratio of an input voltage to an output voltage and a detected Q factor;
6 illustrates the concept of determining whether a foreign substance is present by detecting signal attenuation,
7 shows an example of setting an FOD line that distinguishes between a case in which a foreign material is present and a case in which charging is possible based on a value obtained by measuring a Q factor while changing the location of a receiving device and the type and location of a foreign material,
8 shows an example of adjusting the level of foreign matter determination based on the distance from the FOD line;
9 shows the configuration of a wireless power transmission device to which the present invention is applied in blocks,
10 is a flowchart illustrating an operation of a method of wirelessly transmitting power while detecting a foreign object according to the present invention.

Hereinafter, embodiments of a wireless power transmission apparatus and method according to the present invention will be described in detail based on the accompanying drawings.

1 conceptually shows that power is wirelessly transmitted from a wireless power transmitter to an electronic device.

The wireless power transmission device 1 may be a power transmission device that wirelessly transfers power required by the electronic device 2 or a wireless charging device for charging the battery of the electronic device 2 by wirelessly transferring power. Alternatively, it may be implemented in various types of devices that deliver power to the electronic device 2 requiring power in a non-contact state.

The electronic device 2 is a device capable of operating by receiving power wirelessly from the wireless power transmitter 1, and may charge a battery using the power wirelessly received. Electronic devices that receive power wirelessly include portable electronic devices such as smart phones, smart terminals, tablet computers, multimedia terminals, input/output devices such as keyboards, mice, video or audio auxiliary devices, and auxiliary batteries. can do.

Resonance occurs in the electronic device 2 by the inductive coupling method based on the electromagnetic induction phenomenon by the wireless power signal of the wireless power transmitter 1, that is, the wireless power signal transmitted from the wireless power transmitter 1 and the resonance phenomenon Power can be transmitted wirelessly from the wireless power transmitter 1 to the electronic device 2 without contact. By changing the magnetic field by alternating current in the primary coil due to the electromagnetic induction phenomenon, the current flows toward the secondary coil. transfers power by induction.

When the intensity of the current flowing in the primary coil of the wireless power transmitter 1 changes, the current changes the magnetic field passing through the primary coil or transmission coil (primary coil, TX coil), and the changed magnetic field is (2) An induced electromotive force is generated on the secondary coil or receiving coil (secondary coil, RX coil) side.

The wireless power transmitter 1 and the electronic device 2 are disposed so that the primary coil of the wireless power transmitter 1 and the secondary coil of the electronic device 2 are close to each other, and the wireless power transmitter 1 When the current of the primary coil is controlled to change, the electronic device 2 supplies power to a load such as a battery using the electromotive force induced in the secondary coil.

Since the efficiency of wireless power transfer by the inductive coupling method is affected by the arrangement and distance between the wireless power transmitter 1 and the electronic device 2, the wireless power transmitter 1 includes a flat interface surface. A primary coil is mounted on the bottom of the interface surface, and one or more electronic devices may be placed on the interface surface. By making the space between the primary coil mounted below the interface surface and the secondary coil located above the interface surface sufficiently small, the efficiency of wireless power transfer by inductive coupling can be increased.

A mark indicating a position where an electronic device is to be placed may be displayed on the upper part of the interface surface, and may indicate a position of an electronic device that properly arranges between a primary coil and a secondary coil mounted on the lower part of the interface surface. . A protrusion-shaped structure for guiding the location of the electronic device may be formed on the upper surface of the interface, and a magnetic body such as a magnet is formed on the lower surface of the interface, and the primary coil is attracted by the magnetic body of the other pole provided inside the electronic device. and the secondary coil may be guided to be well aligned.

2 conceptually illustrates a circuit configuration of a power conversion unit of a transmission module for wirelessly transmitting power using an electromagnetic induction method.

The wireless power transmission module may include a power converter composed of a power source, an inverter, and a resonance circuit. The power source may be a voltage source or a current source, and the power converter converts the power supplied from the power source into a wireless power signal and converts it into a wireless power signal. It is transmitted to the power receiving module. The wireless power signal is formed in the form of a magnetic field or electromagnetic field having resonance characteristics, and the resonance circuit includes a coil that generates the wireless power signal.

The inverter converts a direct current input into an alternating current waveform of a desired voltage and frequency through a switching element and a control circuit. In FIG. 2, a full-bridge inverter is shown, and other types of inverters such as a half-bridge inverter are also possible .

The resonance circuit includes a primary coil (Lp) and a capacitor (Cp) that transmit power in a magnetic induction method, and the coil and capacitor determine the basic resonance frequency of power transmission. The primary coil forms a magnetic field corresponding to a wireless power signal according to a change in current, and may be implemented in a flat plate shape or a solenoid shape.

The alternating current converted by the inverter drives the resonant circuit so that a magnetic field is formed in the primary coil. By controlling the on/off timing of the switch including the inverter, an alternating current with a frequency close to the resonant frequency of the resonant circuit is generated to transmit the module. The transmission efficiency of can be increased, and the transmission efficiency of the transmission module can be changed by controlling the inverter.

3 illustrates a configuration for exchanging power and messages between a wireless power transmission module and a reception module.

Since the power converter only transmits power unilaterally regardless of the reception status of the reception module, the wireless power transmission module needs a configuration for receiving feedback related to the reception status from the reception module in order to transmit power in accordance with the status of the reception module. Do.

The wireless power transmission module 100 may include a power conversion unit 110, a communication unit 120, a control unit 130, and a power supply unit 140, and the wireless power reception module 200 may include a power reception unit 210 , It may be configured to include a communication unit 220 and a control unit 230, and may be configured to further include a load (or power supply unit) 240 to which received power is supplied. The load 240 may include a charger for charging an internal battery with power supplied from the power receiver 210 .

The power conversion unit 110 is composed of the inverter and the resonance circuit of FIG. 2 and may be configured to further include a circuit capable of adjusting characteristics such as frequency, voltage, and current used to form a wireless power signal.

The communication unit 120 is connected to the power conversion unit 110 and demodulates a wireless power signal modulated by the receiving module 200 that wirelessly receives power according to magnetic induction from the transmission module 100 to send a power control message. can be detected.

The control unit 130 determines one or more characteristics of the operating frequency, voltage, and current of the power conversion unit 110 based on the message detected by the communication unit 120, and controls the power conversion unit 110 to convert power. The unit 110 may generate a wireless power signal suitable for the message. The communication unit 120 and the control unit 130 may be configured as one module.

The power receiver 210 includes a matching circuit composed of a capacitor and a secondary coil generating an induced electromotive force according to a change in the magnetic field generated in the primary coil of the power converter 110, and an AC flowing through the secondary coil. It may include a rectifier circuit that rectifies the current and outputs a DC current.

The communication unit 220 of the receiving module is connected to the power receiving unit 210 and adjusts the load of the power receiving unit in a manner of adjusting the resistive load in DC and/or the capacitive load in AC, so that the transmission module and the receiving module A power control message may be transmitted to the transmission module by changing a wireless power signal between the terminals.

The control unit 230 of the receiving module controls each component included in the receiving module, measures the output of the power receiving unit 210 in the form of current or voltage, and controls the communication unit 220 based on this measurement to transmit power wirelessly. A power control message may be communicated to module 100 . The message may instruct the wireless power transmission module 100 to start or end transmission of the wireless power signal and also to adjust characteristics of the wireless power signal.

The wireless power signal formed by the power converter 110 of the transmission module is received by the power receiver 210, and the control unit 230 of the receiving module controls the communication unit 220 to modulate the wireless power signal. 230 may perform a modulation process to change the amount of power received from the wireless power signal by changing the reactance of the communication unit 220 . When the amount of power received from the wireless power signal changes, the current and/or voltage of the power conversion unit 110 that forms the wireless power signal also changes, and the communication unit 120 of the wireless power transmission module 100 changes the power conversion unit 110. A demodulation process may be performed by detecting a change in current and/or voltage.

The control unit 230 of the receiving module generates a packet including a message to be transmitted to the wireless power transmission module 100 and modulates the wireless power signal to include the generated packet, and the control unit 130 of the transmission module is a communication unit A power control message can be obtained by decoding the packet extracted through 120. The controller 230 of the receiving module generates a wireless power signal based on the amount of power received through the power receiver 210 to adjust the received power. A message requesting a change in the characteristics of can be transmitted.

4 is a block diagram illustrating a loop for controlling power transmission between a wireless power transmission module and a reception module.

Current is induced in the power receiving unit 210 of the receiving module 200 according to the change in the magnetic field generated by the power conversion unit 110 of the transmitting module 100 and power is transmitted, and the control unit 230 of the receiving module A control point, that is, a desired output current and/or voltage is selected, and an actual control point for power received through the power receiver 210 is determined.

The controller 230 of the receiving module 100 calculates a control error value using a desired control point and an actual control point while power is being transmitted. For example, the difference between two output voltages or currents is taken as a control error value. can The control error value may be determined such that it becomes, for example, a negative value when less power is required to reach the desired control point, and a positive value when more power is required to reach the desired control point. The control unit 230 of the receiving module 200 generates a packet including a control error value calculated by changing the reactance of the power receiving unit 210 over time through the communication unit 220 and transmits the packet to the transmission module 100. can transmit

The communication unit 120 of the transmission module demodulates a packet included in the wireless power signal modulated by the reception module 200 to detect a message, and may demodulate a control error packet including a control error value.

The controller 130 of the transmission module decodes the control error packet extracted through the communication unit 120 to obtain a control error value, and uses the actual current value that actually flows in the power conversion unit 110 and the control error value to A new current value can be determined to transmit the desired power.

When the system is stabilized from the process of receiving the control error packet from the receiving module, the control unit 130 of the transmission module applies a new operating point, that is, to the primary coil so that the actual current value flowing in the primary coil becomes a new current value. The power conversion unit 110 is controlled so that the magnitude, frequency, duty ratio, etc. of the AC voltage reach a new value, and the new operating point is maintained so that the receiving module can additionally communicate control information or status information.

The interaction between the wireless power transmission module 100 and the wireless power reception module 200 includes four steps including selection, ping, identification & configuration, and power transfer can be made with The select step is for the transmitting module to discover the object placed on the interface surface, the ping step is for checking whether the object contains the receiving module or not, and the identification/configuration step is the preparation step for sending power to the receiving module. It receives appropriate information from the receiving module and concludes a power transfer contract with the receiving module based on this, and the power transfer step is the interaction between the transmitting module and the receiving module to actually transmit power to the receiving module wirelessly. It is a step.

In the ping step, the receiving module 200 transmits a Signal Strength Packet (SSP) indicating the degree of flux coupling between the primary coil and the receiving coil to the transmitting module 100 through modulation of the resonance waveform. The packet SSP is a message generated by monitoring the voltage rectified by the receiving module, and the transmitting module 100 can receive it from the receiving module 200 and use it to select an initial driving frequency for power transmission.

In the identification/configuration step, configuration including information such as an identification packet including the version of the receiving module 200, manufacturer code, and device identification information, the maximum power of the receiving module 200, and a power transmission method. The receiving module 200 transmits a packet (Configuration Packet) to the transmitting module 100.

In the power transmission step, a control error packet (CEP) indicating the difference between the operating point at which the receiving module 200 receives the power signal and the operating point determined in the power transmission contract, and the receiving module 200 transmits the interface surface The receiving module 200 transmits to the transmitting module 100 a received power packet (RPP) indicating an average value of received power through .

The received power packet (RPP) is received power amount data considering the rectified voltage, load current, offset power, etc. of the power receiving unit 210 of the receiving module. ), and the transmission module 100 receives it and uses it as an operation factor for power control.

The communication unit 120 of the transmission module extracts packets from changes in the resonance waveform, and the control unit 130 decodes the extracted packets to obtain a message and controls the power conversion unit 110 based on this to obtain a message. Power can be wirelessly transmitted while changing the power transmission characteristics as requested.

On the other hand, in the method of wirelessly transmitting power by inductive coupling, the efficiency is less affected by frequency characteristics, but is affected by the arrangement and distance between the transmission module 100 and the reception module 200.

The area where the wireless power signal can reach can be divided into two areas. When the transmission module 100 wirelessly transfers power to the reception module 200, the part of the interface surface through which a high-efficiency magnetic field can pass is active. An area in which the transmission module 100 can detect the presence of the reception module 200 may be referred to as a sensing area.

The control unit 130 of the transmission module can detect whether the reception module 200 is placed or removed in the active area or the sensing area, using a wireless power signal formed in the power conversion unit 110 or provided separately. It is possible to detect whether the receiving module 200 is disposed in the active area or the sensing area by the sensor.

For example, the control unit 130 of the transmission module is influenced by the wireless power signal due to the reception module 200 present in the sensing area, and the characteristics of power for forming the wireless power signal of the power conversion unit 110 are changed. It is possible to detect the presence of the receiving module 200 by monitoring whether or not the The control unit 130 of the transmission module may determine whether to perform a process of identifying the reception module 200 or start wireless power transmission according to a result of detecting the existence of the reception module 200 .

The power conversion unit 110 of the transmission module may further include a positioning unit. The positioning unit may move or rotate the primary coil in order to increase the efficiency of wireless power transfer by inductive coupling. In particular, the receiving module ( 200) may be used when it does not exist within the active area of the transport module 100.

The positioning unit moves the primary coil so that the distance between the centers of the primary coil of the transmission module 100 and the secondary coil of the reception module 200 is within a certain range, or the centers of the primary coil and the reception coil overlap. It may be configured to include a driving unit for moving the primary coil. To this end, the transmission module 100 may further include a sensor or detection unit for detecting the position of the reception module 200, and the control unit 130 of the transmission module controls information about the reception module 200 received from the sensor of the detection unit. Based on the location information, the location determining unit may be controlled.

Alternatively, the control unit 130 of the transmission module may receive control information about the arrangement or distance to the reception module 200 through the communication unit 120 and control the position determination unit based on this.

In addition, the transmission module 100 is formed to include two or more plural primary coils and selectively uses some of the plural primary coils that are suitably arranged with the receiving coils of the receiving module 200 to increase transmission efficiency. In this case, the positioning unit may determine which of the plurality of primary coils is to be used for power transmission.

A single primary coil or a combination of one or more primary coils forming a magnetic field passing through the active region may be referred to as a primary cell. Detect and determine the active area based on this, connect the transmission module constituting the main cell corresponding to the active area, and so that the primary coil of the corresponding transmission module and the secondary coil of the receiving module 200 are inductively coupled. You can control it.

On the other hand, the receiving module 200 is built into an electronic device such as a smart phone or a smart device including a smart phone or a multimedia playback terminal, and the electronic device is not constant in a vertical or horizontal direction on the interface surface of the transmitting module 100 Being oriented or positioned, the transport module requires a large active area.

When a plurality of primary coils are used to widen the active area, as many driving circuits as the number of primary coils are required and control of the plurality of primary coils becomes complicated, the cost of the transmission module, that is, the wireless charger, increases when commercialized. . In addition, even in the case of applying a method of changing the location of the transmission coil to expand the active area, since a transfer mechanism for moving the location of the primary coil must be provided, there are problems in that the volume and weight increase and the manufacturing cost increases.

If there is a way to expand the active area even with one primary coil with a fixed position, it is effective, but if the size of the primary coil is simply increased, the magnetic flux density per unit area of the primary coil decreases and the magnetic coupling force between the transmitting and receiving coils increases. As it weakens, the active area does not increase as expected and the transmission efficiency decreases.

As such, it is important to determine an appropriate shape and size of the primary coil in order to expand the active area and improve transmission efficiency. A multi-coil method employing two or more primary coils is effective as a method of expanding the active area of the wireless power transmission module.

On the other hand, one of the methods for detecting whether or not a foreign substance, particularly a metal foreign substance, is placed between the receiving device and the transmitting device is to determine whether the Q factor of the transmitting device or the receiving device is changed. If the detected Q factors are different, it can be determined that there is a foreign substance.

5 illustrates a circuit for detecting a Q factor using a ratio of an input voltage to an output voltage and a graph of a detected Q factor.

The voltage across the coil (L) is detected as the output voltage (V2) by inputting the alternating voltage as the input voltage (V1) while changing the frequency to the resonant circuit including the capacitor (C) and the coil (L), and output voltage The Q factor can be calculated using the ratio of (V2) and the input voltage (V1). In the graph on the right of FIG.

로 표현되고, 여기서

이고,

이다.6 illustrates a concept of determining whether there is a foreign substance by detecting signal attenuation. When an input voltage with a resonant frequency or a frequency close to the resonant frequency is supplied to the resonant circuit, the output signal of the resonant circuit is

is expressed as, where

ego,

to be.

If there is no foreign matter near the resonant circuit (NO FO), the output signal gradually decreases due to a slight natural attenuation caused by the resistive component constituting the circuit over time, but when there is a foreign material near the resonant circuit (With FO), the output signal is rapidly attenuated due to the interaction between the foreign matter and the resonant circuit.

In this way, when the resonance circuit is driven at a frequency near the resonance frequency, the degree of attenuation of the output signal may be detected to determine whether a foreign material is nearby.

Although the wireless charger may have a means for determining the proximity of a foreign object as shown in FIGS. 5 and 6, the wireless charger does not know the Q factor or resonant frequency of the receiving device, so it accurately determines whether a foreign object is present between the charger and the receiving device. It's not easy to do.

Recently, a receiving device such as a smart phone capable of wireless charging is used in a state covered in a dedicated case to protect the device, and is also placed on a wireless charger, and a credit card including an RF module having an RF function such as NFC is stored inside the case do. The RF module of these credit cards acts as a foreign substance that interferes with the wireless charging operation.

In this way, rather than in the case where the receiving device is placed on the interface surface of the wireless charger in a state where a coin or clip is placed on the wireless charger and foreign matter interferes with charging, the receiving device is placed in a state where a credit card or clip is stored inside the case of the receiving device. is placed on top of the wireless charger, and foreign objects are more likely to interfere with charging.

In the present invention, a criterion related to the Q factor capable of distinguishing a state in which a foreign substance is present and a state in which charging is possible is prepared and stored, and when the receiving device is charged, the Q factor is measured and compared with the stored criterion, so that the current charging situation is determined by the foreign matter It can be determined whether there is a state or a state in which charging is possible.

More specifically, when the wireless power transmission device is shipped, a plurality of first Q factors in various situations with foreign substances and a plurality of second Q factors in various situations in which there are no foreign substances and charging is possible, and the first Q factor and A criterion for distinguishing the second Q factor may be obtained and the criterion may be stored. When transmitting power wirelessly to a receiving device, the wireless power transmission device storing the reference may obtain a Q factor and compare it with the stored reference to determine whether a foreign substance is present or whether charging is possible.

The Q factor is obtained in various situations where there is foreign matter or charging is possible, and the obtained Q factors are placed on the plane with the X and Y axes of the resonance frequency and Q value constituting the Q factor. A line dividing the coordinates of the possible situation can be determined, and this can be used as a criterion for distinguishing the foreign matter situation from the charging possible situation.

FIG. 7 illustrates an example of setting an FOD line that distinguishes between a case in which a foreign material is present and a case in which charging is possible based on a value obtained by measuring a Q factor while changing a location of a receiving device and a type and location of a foreign material.

Prior to charging the receiving device, the wireless power transmitter or wireless charger measures a Q factor, that is, a Q frequency that is a resonant frequency and a Q value at that time.

Afterwards, various situations are simulated and the Q factor is measured at each time. Various types of metal foreign substances in the wireless power receiving device, for example, a smartphone, for example, various sizes of coins, clips, and RF modules such as NFC The Q factor is measured while charging the smart phone by attaching a lamp, and the smartphone and the transmission device, that is, the center of the wireless charger, are measured on a plane at predetermined length intervals with or without metal foreign matter attached. You can measure the Q factor while moving.

The Q factors measured in various situations are displayed as coordinates on the Q plane where the horizontal axis (X axis) is the Q frequency and the vertical axis (Y axis) is the Q value. A line that can distinguish a state in which there is no foreign matter and can be charged can be extracted from the plane.

As shown in FIG. 7, the first area formed in the direction in which the Q frequency decreases and the Q value increases corresponds to a situation in which foreign matter is present, and the second area formed in the direction in which the Q frequency increases and the Q value decreases is free of foreign matter and It can respond to situations where charging is possible.

In a plane formed by the Q factor, a curve dividing a first area with foreign matter and a second area where charging is possible without foreign matter may be determined, and it may be expressed as a straight line (FOD line) as shown in FIG. It can also be expressed as a quadratic curve or a higher-dimensional curve.

The FOD line (or foreign matter boundary curve) may be measured in the process of shipping the corresponding wireless charger and stored in the non-volatile memory of the wireless charger.

The wireless charger measures the Q factor when the receiving device is detected and starts wireless charging, and compares the measured Q factor with the FOD line to determine whether the coordinates of the Q factor are in the first area with foreign matter or in the second area without foreign matter. If it is in the first area, charging may be stopped or notified to the user if it is in the first area, and charging may proceed immediately or continue if it is in the second area.

In addition, if the Q factor measured while transmitting power to the receiving device is in the first region, it can be determined that there is a metal foreign substance, but it is not necessary to stop charging unconditionally because the metal foreign substance is nearby, so charging can be stopped. It may be necessary to decide whether to maintain a charge or adjust the power transfer strength while maintaining a charge.

In order to determine whether to continue charging, the distance between the measured Q factor and the FOD line may be further considered. It was confirmed through experimentation, that the farther away from the FOD line, the higher the probability of FOD and the higher the possibility that the foreign substance interferes with charging.

In FIG. 7, it is advantageous to stop charging as the coordinates at which the Q factor is located in the first area are farther to the left of the FOD line, that is, in the minus direction, from the FOD line, and the closer to the FOD line, the more carefully It is advantageous to judge

8 illustrates an example of adjusting the level of foreign matter determination based on the distance from the FOD line.

In FIG. 8, the horizontal axis indicates a plurality of cases in which the Q factor is measured by performing the test in the presence of metal foreign substances, the vertical axis indicates the distance between the Q factor measured in each case and the FOD line, and the horizontal line indicates the distance between the FOD line and the Q factor measured in each case. Indicates the corresponding Q factor.

The further away from the FOD line in the minus direction on the vertical axis, that is, the lower the graph in FIG. Charging may be continued by changing the judgment level or the foreign matter judgment level.

9 shows the configuration of a wireless power transmission device to which the present invention is applied in functional blocks.

The transmission device of FIG. 9 may further include a Q factor detector for detecting a Q factor in addition to the transmission module shown in FIG. 3 . In addition, the transmission device of FIG. 9 may further include a storage means for storing information related to the FOD line and an output means for notifying the user of attachment of foreign substances.

As shown in FIG. 9, the wireless power transmitter 100 or transmission module 100 includes a power converter 110, a communication unit 120, a controller 130, a power supply unit 140, and a Q factor detector 150. ).

The power conversion unit 110 is composed of the inverter and the resonance circuit of FIG. 2 and may be configured to further include a circuit capable of adjusting characteristics such as frequency, voltage, and current used to form a wireless power signal.

The communication unit 120 may be connected to the power conversion unit 110 and detect a power control message by demodulating a wireless power signal modulated by a receiving device that wirelessly receives power according to magnetic induction. The communication unit 120 of the transmission module capable of transmitting more than medium power may communicate with the reception module by including a short-range communication means such as Bluetooth.

The control unit 130 determines one or more characteristics of the operating frequency, voltage, and current of the power conversion unit 110 based on the message detected by the communication unit 120, and controls the power conversion unit 110 to convert power. The unit 110 may generate a wireless power signal suitable for the message. The communication unit 120 and the control unit 130 may be configured as one module.

The power supply unit 140 may supply power to components of the transmission device.

The Q factor detector 150 determines the Q factor of the resonance circuit composed of the primary coil and the capacitor, that is, the resonance frequency and the Q value at that time, while transmitting power to the receiving device according to the method described with reference to FIG. 5 . It may be detected, and may include a voltage sensor for detecting the input voltage of the resonance circuit and the output voltage applied to the primary coil.

The transmission module 100 may further include an output unit (not shown) to inform the user that there is a foreign substance. The output unit includes a display unit outputting a message through an image or light, a sound unit transmitting a message through sound, It may be configured to include at least one or more of vibration units that deliver a message through vibration.

The control unit 130 for controlling each component of the transmission device measures the Q factor of the resonance circuit, that is, the resonance frequency (or Q frequency) and the Q value at that time through the Q factor detection unit 150, and the memory (not shown) compared with the FOD line stored at), it is checked whether the measured Q factor is in the area belonging to the plane formed by the Q frequency and Q value, that is, in the first area with foreign matter or in the second area without foreign matter, and the Q factor is If it is in the first area, it is determined that there is a foreign material, and if the Q factor is in the second area, it can be determined that the receiving device is in a charging area without any foreign material.

If the Q factor measured by the Q factor detector 150 is in the second area, the control unit 130 may determine that there is no foreign material and continue charging the receiving device or receiving module.

On the other hand, if the Q factor is in the first area, the controller 130 determines that there is a foreign material, calculates the distance between the Q factor and the FOD line to determine how much the foreign material affects the charging operation, and calculates the Based on the distance, the foreign matter judgment standard is adjusted. The farther the distance in the negative direction is, the more the foreign matter affects charging, and the charging operation is stopped. can

FIG. 10 is a flowchart illustrating an operation of a method of wirelessly transmitting power while detecting a foreign substance according to the present invention, and the operation of FIG. 10 may be performed by the control unit 130 of the transmission device.

The controller 130 resets the timer and starts the timer again (S1010). The timer provides a time counting function for the transmission module to periodically detect the presence or absence of foreign substances.

The control unit 130 compares the timer output value and the threshold value THD to determine whether the timer output value has become greater than the threshold value THD, that is, whether or not the period for detecting whether foreign substances are attached has reached (S1020), and the timer If the output value is less than the threshold value (THD), it returns to step S1020.

The controller 130 measures the Q factor through the Q factor detector 150 (S1030).

The control unit 130 compares the measured Q factor with the FOD line stored in a memory (not shown) to determine whether the Q factor is in the first area with foreign matter or in the second area where there is no foreign material and can be charged (S1040). ).

If a foreign material is detected, that is, if the measured Q factor is in the first area (YES in S1040), the controller 130 sets a flag value indicating the attachment of the foreign material to 1 (S1050).

The control unit 130 calculates the distance between the measured Q factor and the FOD line, and determines that the foreign matter has a great effect on charging if the distance is greater than a predetermined value, and stops charging, or if the distance is less than a predetermined value, the foreign matter It is determined that this has little effect on charging, and the charging operation may be continued by adjusting the foreign matter judgment criteria loosely (S1060).

In addition, the controller 130 may output an alarm message notifying the attachment of a foreign substance through an output unit (not shown) to notify the user (S1070).

On the other hand, the control unit 130 compares the measured Q factor with the FOD line stored in a memory (not shown) when no foreign matter is detected, that is, when the Q factor is in the second area where there is no foreign matter and can be charged (NO in S1040). ), check whether the flag (FLAG) value of the memory (not shown) is set to 1 (S1080), and if the flag (FLAG) value is set to 1 (YES in S1080), reset the flag (FLAG) value to 0 (S1090), and if the value of the flag (FLAG) is not set to 1 (NO in S1080), the process proceeds to step S1010.

According to the operation flow chart of FIG. 10 , the controller 130 may periodically control the Q factor detector 150 based on the timer value to measure the Q factor and compare the Q factor with the FOD line to detect foreign matter.

In addition, the controller 130 may check a flag indicating whether or not a foreign substance is attached, and if there is no foreign substance, the control unit 130 may transmit power until the battery of the receiving device is fully charged.

In addition, the controller 130 sets a flag value to 1 when a foreign substance is detected, calculates a distance between the measured Q factor and the FOD line, and operates power transmission when the distance is greater than the first value, for example. is stopped, and when the distance is short, for example, less than the first value, the foreign matter detection level is loosely adjusted to continue the power transmission operation, but a message informing of attachment of the foreign matter may be output.

In this way, it is possible to more accurately and efficiently determine whether or not there is a foreign substance, and even when there is a foreign substance, it is possible to determine whether charging is to a degree to be stopped or to the extent that charging can be continued.

In addition, when there is a foreign substance, it is possible to notify the existence of the foreign substance through an image or sound or stop power transmission to prevent excessive heat or fire caused by the foreign substance. The intermittent interruption of the charging operation is prevented, and the electronic device can be quickly charged.

The wireless power transmission method and apparatus described in this specification can be described as follows.

A wireless power transmission method according to an embodiment includes wirelessly transmitting power to a receiving device; Detecting a resonant frequency and a Q value of a resonant circuit included in a transmission device as a Q factor while transmitting power; and continuing the power transmission operation or stopping the power transmission operation based on a comparison between the detected position of the Q factor and the foreign matter boundary curve in a plane having the frequency and the Q value as two axes.

In an embodiment, continuing or stopping may include determining whether a Q factor is located in a first area with a foreign material or a second area without a foreign material based on a foreign material boundary curve.

In one embodiment, the first region is formed in a region having a lower frequency and a higher Q value with respect to the foreign object boundary curve in the plane, and the second region has a higher frequency and a higher Q value with respect to the foreign object boundary curve in the plane. It can be formed in a lower area.

In an embodiment, continuing or stopping includes: calculating a Q factor and a foreign object boundary curve distance when the position of the Q factor belongs to the first region; and adjusting a criterion for judging the foreign matter based on the distance.

In one embodiment, the adjusting step may stop the power transfer operation when the distance is greater than the first value and continue the power transfer operation when the distance is less than the first value.

In one embodiment, the continuing or stopping step may continue the power transfer operation when the position of the Q factor belongs to the second region.

In one embodiment, the foreign matter boundary curve is extracted based on a plurality of Q factors measured while changing the type and location of the receiving device and the type, size, and location of foreign substances when the transmission device is shipped, and stored in the memory of the transmission device. can be stored

A wireless power transmission device according to another embodiment includes a resonant circuit including a primary coil for transmitting power by magnetic induction coupling between an inverter for converting direct current power into alternating current and a secondary coil of a receiving device. power converter; a Q factor detector for detecting a resonance frequency and a Q value of the resonance circuit as a Q factor; and controlling the Q factor detection unit to detect the Q factor during power transmission, and continuing the power transmission operation based on the comparison between the detected position of the Q factor and the foreign matter boundary curve in a plane of which the frequency and the Q value are two axes. It may be configured to include a control unit that controls the power conversion unit to stop the power transmission operation.

In one embodiment, the controller may determine whether the location of the Q factor is in a first area with the foreign material or a second area without the foreign material based on the foreign material boundary curve.

In one embodiment, the first region is formed in a region having a lower frequency and a higher Q value with respect to the foreign object boundary curve in the plane, and the second region has a higher frequency and a higher Q value with respect to the foreign object boundary curve in the plane. It can be formed in a lower area.

In one embodiment, the control unit calculates the Q factor and the foreign matter boundary curve distance when the position of the Q factor belongs to the first area, and stops the power transmission operation when the distance is greater than the first value, and the distance is greater than the first value. The power transfer operation may be continued when the Q factor is small, and the power transfer operation may be continued when the position of the Q factor belongs to the second region.

In one embodiment, a memory for storing a foreign matter boundary curve is further included, and the foreign matter boundary curve includes a plurality of pieces measured while changing the type and location of the receiving device and the type, size, and location of the foreign object when the transmission device is shipped. It may be extracted based on the Q factor and stored in memory.

The present invention is not limited to the described embodiments, and it is obvious to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the present invention. Accordingly, it should be said that such modifications or variations fall within the scope of the claims of the present invention.

1: wireless power transmission device 2: electronic device
100: wireless power transmission module 110: power conversion unit
120: communication unit 130: control unit
140: power supply unit 150: Q factor detection unit
200: wireless power receiving module 210: power receiving unit
220: communication unit 230: control unit
240: load

Claims (12)

wirelessly transmitting power to a receiving device;
Detecting a resonant frequency and a Q value of a resonant circuit included in a transmission device as a Q factor while transmitting power; and
Continuing the power transmission operation or stopping the power transmission operation based on a comparison of the detected position of the Q factor and the foreign matter boundary curve in a plane with frequency and Q value as two axes. Wireless power transmission method. According to claim 1,
The continuing or stopping step,
and determining whether the Q factor is located in a first area with a foreign material or a second area without a foreign material based on the foreign material boundary curve. According to claim 2,
The first region is formed in a region in which the frequency is lower and the Q value is higher with respect to the foreign matter boundary curve in the plane, and the second region is formed in an region in which the frequency is lower with respect to the foreign matter boundary curve in the plane. A wireless power transmission method, characterized in that formed in an area where the Q value is high and the Q value is lower. According to claim 2,
The continuing or stopping step,
calculating the distance between the Q factor and the foreign matter boundary curve when the position of the Q factor belongs to the first area; and
Wireless power transmission method further comprising the step of adjusting the foreign matter determination criterion based on the distance. According to claim 4,
In the adjusting, the power transmission operation is stopped when the distance is greater than the first value, and the power transmission operation is continued when the distance is less than the first value. According to claim 2,
The continuing or stopping step continues the power transmission operation when the position of the Q factor belongs to the second region. According to claim 1,
The foreign matter boundary curve is extracted based on a plurality of Q factors measured while changing the type and location of the receiving device and the type, size, and location of the foreign object when the transmission device is shipped, and stored in the memory of the transmission device A wireless power transmission method, characterized in that. A power conversion unit including a resonant circuit including a primary coil for transmitting power by magnetic induction coupling between an inverter for converting DC power into AC and a secondary coil of a receiving device;
a Q factor detector for detecting a resonance frequency and a Q value of the resonance circuit as a Q factor; and
The Q factor detection unit is controlled to detect the Q factor during power transmission, and a power transmission operation is performed based on a comparison between the detected position of the Q factor and a foreign object boundary curve in a plane having two axes of frequency and Q value. A wireless power transmitter configured to include a control unit for controlling the power conversion unit to continue or stop the power transmission operation. According to claim 8,
The control unit checks whether the Q factor is in a first area with a foreign material or a second area without a foreign material based on the foreign material boundary curve. According to claim 9,
The first region is formed in a region in which the frequency is lower and the Q value is higher with respect to the foreign matter boundary curve in the plane, and the second region is formed in an region in which the frequency is lower with respect to the foreign matter boundary curve in the plane. A wireless power transmission device, characterized in that formed in an area where the Q value is high and the Q value is lower. According to claim 9,
The control unit calculates a distance between the Q factor and the foreign matter boundary curve when the position of the Q factor belongs to the first area, stops the power transmission operation when the distance is greater than a first value, and continue the power transfer operation when the distance is less than the first value;
The control unit continues the power transmission operation when the position of the Q factor belongs to the second area. According to claim 8,
Further comprising a memory for storing the foreign matter boundary curve,
The foreign matter boundary curve is extracted based on a plurality of Q factors measured while changing the type and location of the receiving device and the type, size and location of the foreign matter when the transmission device is shipped, and stored in the memory. wireless power transmission device.

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