KR20230025998A - Apparatus and method for transmitting power wirelessly - Google Patents

Abstract

Disclosed are a wireless power transmission method and an apparatus thereof. In accordance with one embodiment, the wireless power transmission method includes the following steps of: detecting a resonance frequency and a Q value of a resonance circuit included in a transmission device as a Q factor; determining whether a metallic foreign substance exists based on the Q factor; moving a threshold value level to determine whether a power loss occurs when determining that the metallic foreign substance exists; detecting the power loss while wirelessly transmitting power to a reception device; and continuing or stopping a power transmission operation through a comparison between the detected power loss and the threshold value level. Whether the metallic foreign substance exists can be determined based on whether a position of the Q factor belongs to a first area including a part of a foreign substance boundary line dividing an area in which charging is performed due to the nonexistence of a metallic foreign substance and an area in which charging is stopped due to the existence of a metallic foreign substance, on a Q plane using the Q value and a frequency as two axes. When determining that the metallic foreign substance exists, the threshold value level can be moved in a direction to increase the probability of determining the threshold value level as the metallic foreign substance. Therefore, the present invention is capable of preventing the risk of a fire and excessive heat due to output concentrated on a metallic foreign substance when power is wirelessly transmitted.

Description

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

This specification 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 if there is a small metal 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, the charging efficiency is reduced and heat is generated. can happen

This specification takes this situation into consideration, and an object of this specification is to provide a method for effectively determining whether or not a foreign object is present between a transmitting device and a receiving device.

A wireless power transmission method according to an embodiment of this specification for realizing the above object includes detecting a resonance frequency and a Q value of a resonance circuit included in a transmission device as a Q factor; Determining whether a metal foreign substance is present based on the Q factor; moving a threshold level for determining power loss when it is determined that there is a metal foreign substance; detecting power loss while wirelessly transmitting power to a receiving device; and continuing or stopping the power transfer operation through comparison between the detected power loss and the threshold level.

A wireless power transmission device according to another embodiment of the present specification 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, determining whether or not there is a metal foreign material based on the Q factor, moving a threshold level for determining whether or not power is lost when it is determined that there is a metal foreign material, and transmitting power wirelessly. It is characterized in that it is configured to include a control unit for controlling the power converter to continue or stop the power transmission operation through detecting power loss while transmitting to the receiving device and comparing the detected power loss with a threshold level.

Accordingly, it is possible to effectively determine whether a metal foreign object is on the transmitting device or between the transmitting device and the receiving device, and in particular, a small metal foreign object such as a document clip can be effectively detected and charging can be stopped. In addition, during wireless power transmission, it is possible to prevent in advance the danger of excessive heat generation and occurrence of fire due to concentration of output on metal foreign substances.

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 shows a graph in which a resonant frequency moves due to foreign matter;
7 conceptually illustrates calculating power loss as the difference between transmit power and receive power;
8 illustrates a graph for detecting foreign matter by setting a threshold level based on power loss;
9 shows coordinates of various situations in which the location of a receiving device and the type and location of a foreign object are changed in a graph for detecting foreign matter based on power loss;
10 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 measured for a Q factor while changing the location of a receiving device and the type and location of a foreign material, and an area in case there is a clip. is shown,
11 shows an example of moving a threshold level in a graph for detecting foreign matter based on power loss;
12 shows the configuration of a wireless power transmission device to which an embodiment of this specification is applied in blocks,
13 is a flowchart illustrating an operation of a method of wirelessly transmitting power while detecting a foreign material according to an embodiment of the present specification.

Hereinafter, an embodiment of a wireless power transmission apparatus and method 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.

Meanwhile, a wireless charger mounted on a vehicle or the like is easily exposed to foreign substances such as coins or document clips. In addition, 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 smart phone, and is also placed on a wireless charger in that state. Credit cards are also accepted. The RF module of these credit cards also acts as a foreign substance that interferes with the wireless charging operation.

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

Conventionally, the presence or absence of a foreign substance is determined and based on this, whether to proceed with charging is determined. In the case of a metal foreign substance having a certain size, such as a coin, the discrimination power is good. However, it is difficult to detect a metal having a small cross-section, for example, a foreign object having a bent metal line such as a document clip.

This specification proposes a method for effectively detecting a small metal such as a document clip by combining Q factor characteristics and a power loss detection method.

FIG. 5 shows a graph of a circuit for detecting a Q factor using a ratio of input voltage to output voltage and a graph of the detected Q factor, and FIG. 6 shows a graph of a resonant frequency shifted by a foreign material.

As shown in FIG. 5, the AC voltage is input as the input voltage V1 while changing the frequency to the resonant circuit including the capacitor C and the coil L, and the voltage across the coil L is the output voltage ( V2), and the Q factor can be calculated using the ratio of the output voltage V2 and the input voltage V1. In the lower graph of FIG. 5 , it can be seen that the 100 kHz frequency becomes the resonance frequency (Q frequency), and the output voltage (Q value) to the input voltage is the highest at the resonance frequency.

When there is no receiving device around, the Q frequency and Q value of FIG. 5 correspond to the natural frequency of the resonant circuit, but when there is a receiving device or foreign matter around, the Q frequency and Q value change.

In FIG. 6, when there is only a transmitting device (TX), the Q value is the largest, and when a receiving device (RX) is placed around the transmitting device (TX) (TX+RX), the Q frequency (Fr) hardly changes. but the Q value decreases. On the other hand, if there is a metal foreign material (FO) as well as a receiving device (RX) around the transmitter (TX) (TX + RX + FO), the Q frequency shifts (Fr_shifted) and the Q value decreases.

In this way, the receiving device or the foreign material may be detected by using a phenomenon in which the Q frequency and/or the Q value change when the receiving device or the foreign material is present.

7 conceptually illustrates calculating power loss as a difference between transmit power and receive power.

The transmitting device detects transmit power (Tx Power) transmitted to the receiving device, and also detects received received power (Rx Power) received by the receiving device and transmits it to the transmitting device as a received power packet.

The transmitting device calculates power loss by calculating a difference between transmit power (Tx Power) that is directly detected and received power (Rx Power) received through a RPP from the receiving device.

The transmitting device may determine power transmission efficiency and whether there is a foreign substance based on the power loss, and if the power loss is large, it may be estimated that a metal foreign substance is present between the receiving device and the receiving device. That is, a method using power loss is generally used to detect foreign matter.

8 illustrates a graph in which a foreign substance is detected by setting a threshold level based on power loss.

In FIG. 8 , a horizontal axis is a power loss and a vertical axis is a threshold level. The power loss is a difference between transmit power and received power, and the threshold level is a value obtained by multiplying transmit power by a predetermined ratio.

In FIG. 8, the upper left area corresponds to a charging progress area (foreign matter detection area, Non-FOD Area) in which charging is in progress, and the lower right area corresponds to a charging stop area (foreign matter detection area, FOD Area) in which charging is stopped. , the threshold value boundary line dividing the charging progress area and the charging stop area is a straight line with a slope of 1.

For example, if the transmission power is 1,000 mW and the reception power is 600 mW for the first reception device (Rx No. 1), the power loss is 400 mW, and the transmission power is 2,000 mW for the second reception device (Rx No. 2). It may be assumed that if the received power is 1,600mW, the power loss is 400mW.

In this case, although both receiving devices have the same power loss of 400 mW, it can be seen that the first receiving device has a greater power loss than the second receiving device in terms of the ratio of the transmission power. Thus, the threshold level for determining charging interruption needs to be set in proportion to the transmission power.

When a certain ratio value for determining the threshold level is set to, for example, 0.3, the threshold level for the first receiving device (Rx No. 1) is 0.3 * 1,000mW = 300mW, and the first receiving device (Rx No. The threshold level for No.1) becomes 0.3*2,000mW=600mW.

Therefore, the power loss of the first receiving device (Rx No. 1) is greater than the threshold level, that is, the coordinates of the power loss of the first receiving device (Rx No. 1) (power loss, threshold level) = In the foreign matter detection area where (400, 300) is below the threshold boundary, the transmission device stops charging the first reception device (Rx No. 1).

On the other hand, for the second receiving device (Rx No. 2), the power loss is smaller than the threshold level, that is, the coordinates for the power loss of the second receiving device (Rx No. 2) (power loss, threshold level) =(400, 600) is above the threshold boundary in the non-detected foreign matter area, the transmission device continues to charge the second reception device (Rx No. 2).

If charging of the first receiving device (Rx No. 1) is performed, a positive offset may be added to the threshold level (or an offset greater than 1 may be further multiplied) to move the coordinates to the foreign matter detection area. . Conversely, in order to stop charging the second receiver Rx No. 2, the coordinates may be moved to the foreign matter detection area by adding a negative offset to the threshold level (or by further multiplying the offset smaller than 1).

9 shows coordinates of various situations in which the location of a receiving device and the type and location of a foreign object are changed in a graph for detecting foreign matter based on power loss.

In FIG. 9 , circled dots are cases in which only a receiving device, for example, a smart phone, is charged without foreign matter, and the coordinates are shown on a plane having power loss as a horizontal axis and a threshold level as a vertical axis. The circled dots are wireless charging because the power loss is less than the threshold level and is in the foreign matter undetected area.

On the other hand, the square dots are cases when a smart phone is charged while one of several coins is placed around the primary coil of the transmission device. Charging stops.

The diamond (slanted square) dots are the case when the smartphone is charged while a document clip (or paper clip) is placed around the primary coil of the transmission device. The clip does not cause much power loss, and in most cases is located close to the line dividing the foreign matter detection area and the foreign matter non-detection area, that is, the threshold boundary line. Conventionally, charging is simply stopped when the coordinates are in the foreign matter detection area, and charging proceeds when the coordinates are in the foreign matter detection area.

As such, in the case of a document clip, there is not a large difference from the power loss when charging only the smart phone without foreign objects such as coins, so that charging cannot be stopped and the smart phone continues to heat up. That is, it is difficult to accurately determine whether there is a small foreign object such as a document clip using only power loss.

10 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 a location of a receiving device and a type and location of a foreign material, and an area in case there is a clip. it is depicted In the Q plane of FIG. 10 , the horizontal axis represents the Q value and the vertical axis represents the resonant frequency, that is, the Q frequency.

In FIG. 10, the circled dots indicate a case when only a receiving device, for example, a smart phone, is charged without any foreign matter, and the Q value and the resonance frequency measured while changing the position of the receiving device relative to the primary coil of the transmitting device are displayed on the horizontal axis. It is expressed as coordinates on the Q plane with ordinate and ordinate. As can be predicted from the description with reference to FIG. 6 , the circled points are generally located at the lower right of the Q plane, that is, in a region where the resonant frequency is low and the Q value is high.

On the other hand, the square dots are cases when charging a smart phone with one of several coins placed around the primary coil of the transmission device, and the Q factor measured while changing the size and position of the coins is displayed as coordinates on the Q plane. it did Likewise, as can be predicted from FIG. 6, the square points are generally located in the upper left corner of the Q plane, that is, in a region where the resonant frequency is high and the Q value is low.

The lower right area (or the first area) where the circle dots are located is in a state where there is no foreign matter, and charging can continue, and the upper left area (the second area) where the square dots are located is a case where there is a metal foreign material. should stop In the Q plane of FIG. 10, the first area and the second area can be distinguished to some extent so that a curve dividing the two areas can be determined, and can be expressed as a straight line (FOD line) as shown in FIG. Alternatively, it can be expressed as a higher-dimensional curve. Data on the FOD line (or foreign matter boundary line) may be measured in the process of shipping the wireless charger and stored in the non-volatile memory of the wireless charger.

On the other hand, the rhombus (slanted square) points are cases when the smartphone is charged while the document clip is placed around the primary coil of the transmission device, and the Q factor measured while changing the size and position of the document clip is placed on the Q plane indicated by coordinates. In the case of a document clip, the coordinates are mainly distributed around the foreign matter boundary line (FOD line) that divides the lower right area where charging is possible and the upper left area where charging should be stopped, especially in a specific area (eg, as indicated by a square box in FIG. 10). For example, it can be referred to as the clip Q area). Data on the clip Q area may also be measured in the process of shipping the wireless charger and stored in the non-volatile memory of the wireless charger.

Therefore, in the embodiment of this specification, when there is a document clip, it is possible to specify that the clip is a foreign substance by using a phenomenon in which the coordinates of the Q factor are concentrated in the clip Q area, which is a specific area of the FOD line in the Q plane. In addition, when it is confirmed that the clip is intervened with a foreign object, power loss is measured while power is transmitted to the receiving device, and a threshold level related to the power loss is shifted to more accurately determine charging progress or charging cessation.

FIG. 11 illustrates an example of shifting a threshold level in a graph for detecting foreign matter based on power loss.

If there is a clip foreign matter, it is basically reasonable to stop charging, so that the power loss and threshold level in the graph of FIG. You can adjust the value level down. That is, by adjusting the value of the ratio multiplied by the transmission power to a smaller value, the threshold level becomes smaller, so that the coordinates related to the power loss move in a downward direction (a direction with a higher probability of determining the metal foreign matter). .

In FIG. 11, when the clip is determined to be a foreign substance, the threshold level decreases, the diamond point moves downward, and the coordinates belong to the foreign substance detection area below the threshold boundary line, and based on this, the transmission device performs charging or power transmission. can be stopped

12 is a block diagram showing the configuration of a wireless power transmission device to which an embodiment of this specification is applied.

The transmission device of FIG. 12 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. 12 may further include a storage means for storing data related to the FOD line and the clip Q area, and an output means for notifying the user of attachment of foreign substances and stop of charging.

As shown in FIG. 12, 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 that controls each component of the transmission device may determine whether to continue or stop power transmission by using power loss. That is, the control unit 130 receives a received power packet (RPP) through the communication unit 120 while wirelessly transmitting power to the receiving module 200, and receives received power packets received by the receiving module 200 therefrom. Power may be calculated, and a difference between transmit power and received power delivered to the receiving module 200 may be calculated as power loss.

In addition, the control unit 130 obtains a threshold level by multiplying the transmission power by a predetermined ratio value, compares this with the power loss, determines that there is a foreign substance when the power loss is greater than the threshold level, and stops power transmission, Power transmission may continue when the power loss is less than the threshold level.

Alternatively, the control unit 130 may use the Q factor to determine whether or not there is a foreign substance and determine to stop or continue power transmission. That is, the controller 130 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 detector 150, and measures the FOD line and By comparison, it is checked whether the measured Q factor is in the area belonging to the Q plane formed by the Q value and the Q frequency, that is, in the first area without foreign matter or in the second area with foreign matter, and if the Q factor is in the first area, foreign matter If it is determined that there is no foreign matter and the Q factor is in the second area, it can be determined that there is a foreign material.

If the Q factor measured by the Q factor detector 150 is in the first 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 second area, the controller 130 may determine that there is a foreign substance and stop the charging operation of the receiving device or receiving module.

In addition, if the coordinates of the Q factor measured by the Q factor detector 150 are near the FOD line, which is the boundary between the first area and the second area in the Q plane, the control unit 130 stores the coordinates of the Q factor in a memory (not shown). ), and if it is in the clip Q area, proceed with the process of determining whether to stop or continue power transmission using the power loss, which is used to calculate the threshold level to be compared with the power loss You can adjust the percentage value down.

13 is a flowchart illustrating an operation of a method of wirelessly transmitting power while detecting a foreign material according to an embodiment of the present specification.

The control unit 130 detects 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 (S1310).

When the controller 130 displays the detected Q factor as one coordinate on the Q plane having one of the Q value and the Q frequency as the horizontal axis and the other as the vertical axis, the coordinates of the Q factor are the clip Q region. It is checked whether it belongs to (S1320). The clip Q area is a value stored in the memory when the transmission device is shipped. Based on the Q factor, the clip Q area is located in a specific area near the FOD line that divides the area where foreign matter is not detected (or the area where charging is possible) and the area where foreign matter is detected (or the area where charging is stopped). applicable

When confirming that the Q factor coordinates belong to the clip Q region (YES in S1320), the control unit 130 determines that there is a document clip near the primary coil, and determines whether to continue or stop charging using power loss. The threshold level is moved by downwardly adjusting the ratio value used to calculate the threshold level to be compared with the loss (S1330). For reference, the threshold level is calculated by multiplying the transmission power by a certain ratio value.

When the Q factor coordinates do not belong to the clip Q region (NO in S1320), the step S1330 of moving the threshold level is omitted.

The control unit 130 controls the strategy switching unit 110 and the communication unit 120 to wirelessly transmit power to the receiving module or the receiving device, while receiving power packets corresponding to the received power from the receiving device (Received Power Packet, RPP) is received, and the difference between the transmit power and the received power is calculated as power loss (S1340).

The control unit 130 calculates a threshold level by multiplying the transmission power by a predetermined ratio value (adjusted in step S1330 or not adjusted because step S1330 is omitted), and compares it with the power loss (S1350).

If the power loss is greater than the threshold level (YES in S1350), the control unit 130 determines that the power loss data for the receiving device is in the foreign matter detection area in the graph of FIG. 8 related to power loss, and charges or transmits power. It can be stopped (S1360).

On the other hand, if the power loss is less than the threshold level (NO in S1350), the control unit 130 determines that the power loss data for the receiving device in the graph of FIG. 8 related to power loss is in the foreign matter detection area and charges. Alternatively, power transmission may be continued (S1370).

In step S1320, it is determined whether the coordinates of the Q factor are in the clip Q area, but if the coordinates of the Q factor are in the first area without foreign matter far from the FOD line or in the second area with foreign matter, the steps below are performed. It is also possible to immediately start or stop power transmission without doing so.

In the conventional method, a method of determining charging stop/continuation using Q frequency and Q value and a method of comparing power loss with a threshold level were separately used, but both methods judged small metals such as document clips as foreign substances. It was often not possible to do so.

However, in the above-described embodiment, the document clip can be specified using the clip Q area in the Q plane, and the presence of foreign matter can be determined more strictly by moving the threshold level in the method using additional power loss. . Therefore, it is possible to more accurately detect the document clip and stop power transmission, thereby solving the problem of excessive heat generation by proceeding with wireless charging when the clip is intervened.

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 detecting a resonance frequency and a Q value of a resonance circuit included in a transmission device as a Q factor; Determining whether a metal foreign substance is present based on the Q factor; moving a threshold level for determining power loss when it is determined that there is a metal foreign substance; detecting power loss while wirelessly transmitting power to a receiving device; and continuing or stopping the power transfer operation by comparing the detected power loss with the threshold level.

In one embodiment, the metal foreign material may be a bent metal line.

In one embodiment, the moving step may shift the threshold level in a direction that increases the probability of determining a metal contaminant.

In one embodiment, when calculating the threshold level, a ratio value applied to transmit power may be adjusted to be small.

In one embodiment, the determining step may determine whether a metal foreign material is present or not based on whether the position of the Q factor belongs to the first region in the Q plane having two axes of the Q value and the frequency.

In an exemplary embodiment, the first region may include a part of a foreign substance boundary line dividing a region in which charging is performed because there is no metal foreign substance in the Q plane and a region where charging is stopped because there is a metal foreign substance.

In one embodiment, the data related to the foreign matter boundary line 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 material when the transmission device is shipped, and is stored in the memory of the transmission device. can be stored in

In one embodiment, continuing or stopping the power transfer operation includes continuing the power transfer operation when the detected power loss is less than the threshold level and stopping the power transfer operation when the detected power loss is greater than the threshold level. can

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, determining whether or not there is a metal foreign material based on the Q factor, moving a threshold level for determining whether or not power is lost when it is determined that there is a metal foreign material, and transmitting power wirelessly. It may be configured to include a control unit for controlling the power converter to continue or stop the power transmission operation through detecting power loss while transmitting to the receiving device and comparing the detected power loss with a threshold level.

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 (16)

Detecting a resonance frequency and a Q value of a resonance circuit included in the transmission device as a Q factor;
Determining whether a metal foreign substance is present based on the Q factor;
moving a threshold level that is a criterion for determining power loss when it is determined that the metal foreign matter is present;
detecting power loss while wirelessly transmitting power to a receiving device; and
A wireless power transmission method comprising the step of continuing or stopping a power transmission operation through comparison of the detected power loss and the threshold level. According to claim 1,
The metal foreign material is a wireless power transmission method, characterized in that the metal wire is a bent shape. According to claim 2,
The moving of the wireless power transmission method, characterized in that for moving the threshold value level in a direction to increase the possibility of determining the metal foreign matter. According to claim 3,
In the step of moving, when calculating the threshold value level, the wireless power transmission method characterized in that for adjusting a small ratio value applied to the transmission power. According to claim 2,
In the determining step, wireless power transmission characterized in that the existence of the metal foreign matter is determined based on whether the location of the Q factor belongs to a first area in a Q plane having two axes of a Q value and a frequency. method. According to claim 5,
The first region includes a portion of a foreign matter boundary line dividing a region in which charging is performed because there is no metal foreign substance in the Q plane and a region where charging is stopped because there is a metal foreign substance. According to claim 6,
The data related to the foreign matter boundary line 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 material when the transmission device is shipped, and stored in the memory of the transmission device. Wireless power transmission method, characterized in that stored. According to claim 1,
Continuing or stopping the power transfer operation may include continuing the power transfer operation when the detected power loss is less than the threshold level, and continuing the power transfer operation when the detected power loss is greater than the threshold level. Wireless power transmission method characterized in that for stopping. 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
Controls the Q factor detection unit to detect the Q factor, determines whether or not there is a metal foreign material based on the Q factor, and sets a threshold level that is a criterion for determining whether or not power is lost when it is determined that the metal foreign material is present. and a control unit for controlling the power conversion unit to continue or stop a power transmission operation through a comparison between the detected power loss and the threshold value level while detecting power loss while transferring power to the receiving device wirelessly. wireless power transmission device. According to claim 9,
The metal foreign material is a wireless power transmission device, characterized in that the metal wire is a bent shape. According to claim 10,
The wireless power transmission device, characterized in that the control unit moves the threshold value level in a direction to increase the possibility of determining the metal foreign matter. According to claim 11,
In the step of moving, when calculating the threshold value level, the wireless power transmission device, characterized in that for adjusting a small ratio value applied to the transmission power. According to claim 10,
The control unit determines whether or not the metal foreign material exists based on whether the position of the Q factor belongs to a first area in a Q plane having two axes of Q value and frequency. According to claim 13,
The first region includes a part of a foreign matter boundary line dividing a region in which charging is performed because there is no metal foreign substance in the Q plane and a region where charging is stopped because there is a metal foreign substance. According to claim 14,
Further comprising a memory for storing data related to the foreign substance boundary line 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 substance when the transmission device is shipped Wireless power transmission device, characterized in that configured. According to claim 9,
The controller controls the power conversion unit to continue the power transmission operation when the detected power loss is less than the threshold level and to stop the power transmission operation when the detected power loss is greater than the threshold level. A wireless power transmission device characterized in that for doing.

Images