KR102867840B1 - Apparatus and method for detecting foreign object in wireless power transmitting system - Google Patents

Abstract

The present invention relates to a device and method for detecting foreign substances in a wireless power transfer system. The present specification includes performing a foreign substance detection operation prior to initial charging, performing a foreign substance detection operation during charging if no foreign substance is detected before charging begins, and limiting power based on a temperature sensor if no foreign substance is detected while receiving the power signal.

Description

{APPARATUS AND METHOD FOR DETECTING FOREIGN OBJECT IN WIRELESS POWER TRANSMITTING SYSTEM}

The present invention relates to wireless power transmission, and more particularly, to a device and method for detecting foreign substances in a wireless power transmission system.

Typically, to charge portable terminals such as cell phones, laptops, and PDAs, they must receive electrical energy (or power) from an external charger. These portable terminals include battery cells that store the supplied electrical energy and circuits for charging and discharging the battery cells (supplying electrical energy to the portable terminal).

The electrical connection method between the charger and the battery cell for charging electric energy to the battery cell includes a terminal supply method that receives commercial power, converts it into voltage and current corresponding to the battery cell, and supplies electric energy to the battery cell through the terminal of the battery cell.

This terminal supply method involves the use of physical cables or wires. Therefore, when handling a large number of terminal-fed devices, the numerous cables take up significant workspace, are difficult to manage, and are visually unsightly. Furthermore, this terminal supply method can cause problems such as instantaneous discharge due to different potentials between terminals, damage and fire caused by foreign substances, spontaneous discharge, and reduced battery pack lifespan and performance.

Recently, charging systems (hereinafter referred to as wireless power transmission systems) and control methods utilizing wireless power transmission have been proposed to solve the above-mentioned problems. Wireless power transmission is also called contactless power transmission or no-point-of-contact power transmission. A wireless power transmission system is composed of a wireless power transmission device that supplies electric energy using wireless power transmission, and a wireless power reception device that receives the electric energy wirelessly supplied from the wireless power transmission device and charges a battery cell.

In the terminal-supply method, as long as the terminal connection between the charger and the terminal is secure, there is little chance of interference such as foreign substances interfering with charging. However, due to the contactless nature of wireless power transmission systems, foreign substances can be inserted between the wireless power receiver and the wireless power transmitter during charging. If a foreign substance, such as metal, becomes lodged between the wireless power transmitter and the wireless power receiver, not only can power transmission be impeded due to the foreign substance, but overload and foreign substance heat generation can also lead to problems such as product damage or explosion. Therefore, a device and method capable of detecting foreign substances in wireless power transmission systems are required.

The technical problem of the present invention is to provide a device and method for detecting foreign substances in a wireless power transmission system.

Another technical object of the present invention is to provide a device and method for detecting a foreign substance in an initial recognition stage.

Another technical problem of the present invention is to provide a device and method for detecting a foreign substance based on a current induced in a primary coil in a wireless power transmission system.

Another technical problem of the present invention is to provide a device and method for performing an operation of limiting power in response to detection of a foreign substance in a wireless power transmission system.

Another technical problem of the present invention is to provide a wireless power transmission device and method having a foreign substance detection function in a wireless power transmission system.

According to one aspect of the present invention, a method for detecting a foreign substance in a wireless power receiving device includes the steps of performing a foreign substance detection operation before initial charging, performing a foreign substance detection operation during charging using one-way communication or two-way communication if no foreign substance is detected until charging begins, and detecting a minute foreign substance that was not detected using a temperature sensor and limiting power if no foreign substance is detected in the foreign substance detection operation during charging.

According to another aspect of the present invention, a wireless power receiving device for detecting a foreign substance includes a second core block for receiving wireless power from a wireless power transmitting device by coupling with a first core block provided in the wireless power transmitting device through magnetic induction or magnetic resonance, a rectifying unit connected to the second core block and performing full-wave rectification on an AC waveform generated in the second core block to provide power to a control unit and an external load, and a control unit for measuring an initial voltage of an output terminal connected to the external load and controlling the wireless power receiving device to enter a foreign substance detection phase when the initial voltage exists within a reference voltage range, wherein the control unit performs a foreign substance detection operation before the initial charging, or performs a foreign substance detection operation during charging using one-way communication or two-way communication when no foreign substance is detected until charging begins, or, when no foreign substance is detected in the foreign substance detection operation during charging, detects a minute foreign substance that was not detected using a temperature sensor and limits power.

The wireless power transmission device according to the present invention can detect foreign substances at any point during charging, from before charging begins, thereby increasing the probability of detecting foreign substances. Furthermore, the method for detecting foreign substances at each stage is clearly defined, facilitating the implementation of foreign substance detection. Furthermore, the wireless power transmission device can detect foreign substances based on information exchanged with a wireless power receiving device, or can detect foreign substances on its own without such information, thereby enabling compatible foreign substance detection across a variety of products. In this way, if a foreign substance is detected, wireless power transmission can be halted or the user can be prompted to remove the foreign substance, thereby preventing damage to the device caused by the foreign substance.

FIG. 1 illustrates components of a wireless power transmission system according to an example of the present invention.
FIG. 2 is a flowchart illustrating a method for performing foreign substance detection in a wireless power transmission system according to an example of the present invention.
FIG. 3 is a flowchart illustrating a method for performing foreign substance detection in a wireless power transmission system according to another example of the present invention.
FIG. 4 is a flowchart illustrating a method for performing foreign substance detection in a wireless power transmission system according to another example of the present invention.
FIG. 5 is a flowchart illustrating a method for performing foreign substance detection in a wireless power transmission system according to an example of the present invention.
Figure 6 is an operation flowchart of a wireless power transmission system according to another example of the present invention.
Figure 7 is an operation flowchart of a wireless power transmission system according to another example of the present invention.
Figure 8 is a block diagram illustrating a wireless power transmission device according to an example of the present invention.
FIG. 9 is a block diagram illustrating a wireless power transmission device according to another example of the present invention.
FIG. 10 is a block diagram illustrating a wireless power receiving device according to an example of the present invention.

The term "wireless power" as used hereinafter is used to mean any form of energy involving electric, magnetic, or electromagnetic fields that is transmitted from a transmitter to a receiver without the use of physical electromagnetic conductors. Wireless power, which may also be referred to as a power signal, may refer to an oscillating magnetic flux enclosed by a primary and secondary coil. Power conversion in a system is described herein for wirelessly charging devices including, for example, mobile phones, cordless phones, iPods, MP3 players, headsets, etc. In general, the basic principles of wireless energy transfer include both magnetic inductive coupling and magnetic resonant coupling (i.e., resonant induction) using frequencies below 30 MHz. However, various frequencies may be utilized, including frequencies that allow license-exempt operation at relatively high radiation levels, for example, below 135 kHz (LF) or at 13.56 MHz (HF).

FIG. 1 illustrates components of a wireless power transmission system according to an example of the present invention.

Referring to FIG. 1, a wireless power transmission system (100) includes a wireless power transmission device (110) and one wireless power reception device (150-1) or n wireless power reception devices (150-1,...,150-n).

The wireless power transmission device (110) includes a primary core block. The primary core block may include a core and one or more primary coils. The wireless power transmission device (110) may have any suitable shape, but one preferred shape is a flat platform having a power transmission surface, on or near which each of the wireless power reception devices (150-1,...,150-n) may be positioned.

The wireless power receiving devices (150-1,...,150-n) are separable from the wireless power transmitting device (110), and each wireless power receiving device (150-1,...,150-n) has a secondary core block that is coupled with an electromagnetic field generated by a primary core block of the wireless power transmitting device (110) when it is near the wireless power transmitting device (110). The secondary core block may include a core and one or more secondary coils.

The wireless power transmission device (110) transmits power to the wireless power reception devices (150-1,...,150-n) without direct electrical contact. At this time, the primary core block and the secondary core block are said to be magnetically coupled or resonantly coupled to each other. The primary coil or the secondary coil may have any suitable shape, but may be, for example, a copper wire wound around a high-permeability formation such as ferrite or an amorphous metal.

The wireless power receivers (150-1,...,150-n) are typically connected to an external load (not shown, also referred to as the actual load of the wireless power receiver here) and supply power wirelessly received from the wireless power transmitter (110) to the external load. For example, the wireless power receivers (150-1,...,150-n) can be carried by objects that consume or store power, such as portable electric or electronic devices or rechargeable battery cells or batteries, respectively.

FIG. 2 is a flowchart illustrating a method for performing foreign substance detection in a wireless power transmission system according to an example of the present invention.

Referring to FIG. 2, a foreign substance detection operation is performed before the first charge (S200). As an example, the foreign substance detection operation before the first charge is as shown in FIG. 5.

If a foreign substance is detected before the first charge (S205), a power limiting operation corresponding to the foreign substance detection is performed (S225).

If no foreign matter is detected before the first charge (S205), when charging begins, a foreign matter detection operation is performed during charging (S210).

For example, one-way communication can be performed during charging to detect foreign substances. For example, the foreign substance detection operation using one-way communication during charging is as shown in FIG. 6.

As another example, foreign matter can be detected by performing two-way communication during charging. As an example, the foreign matter detection operation using two-way communication during charging is as shown in Figure 7 below.

As another example, the one-way communication and the two-way communication may be performed simultaneously or independently during charging to detect foreign substances.

If a foreign substance is detected during charging (S215), a power limit operation in response to foreign substance detection is performed as in step S225 above.

If no foreign matter is detected during charging (S215), and if a problem occurs in power transmission due to a small foreign matter that is not detected, power is limited (e.g., power is cut off) based on a temperature sensor (or thermistor) to protect power transmission (S220). The temperature sensor may be attached to the receiving device or the transmitting device.

Alternatively, even after the power limiting operation in response to foreign matter detection is performed in step S225, if a problem occurs in power transmission due to a minute foreign matter that is not detected, the power is limited based on the temperature sensor (or thermistor) to protect power transmission.

FIG. 3 is a flowchart illustrating a method for performing foreign substance detection in a wireless power transmission system according to another example of the present invention.

Referring to FIG. 3, a foreign substance detection operation is performed before the first charge (S300). As an example, the foreign substance detection operation before the first charge is as shown in FIG. 5.

If a foreign substance is detected before the first charge (S305), a power limiting operation corresponding to the foreign substance detection is performed (S315).

If no foreign matter is detected prior to the initial charge (S305), and if a problem occurs in power transmission due to a small foreign matter that was not detected, power is limited (e.g., power is cut off) based on a temperature sensor (or thermistor) to protect power transmission (S310). The temperature sensor may be attached to the receiving device or the transmitting device.

Alternatively, even after the power limiting operation in response to foreign matter detection is performed in step S315, if a problem occurs in power transmission due to a minute foreign matter that is not detected, the power is limited based on the temperature sensor (or thermistor) to protect power transmission.

FIG. 4 is a flowchart illustrating a method for performing foreign substance detection in a wireless power transmission system according to another example of the present invention.

Referring to Fig. 4, when charging starts, a foreign substance detection operation is performed during charging (S400).

For example, one-way communication can be performed during charging to detect foreign substances. For example, the foreign substance detection operation using one-way communication during charging is as shown in FIG. 6.

As another example, foreign matter can be detected by performing two-way communication during charging. As an example, the foreign matter detection operation using two-way communication during charging is as shown in Figure 7 below.

As another example, the one-way communication and the two-way communication may be performed simultaneously or independently during charging to detect foreign substances.

If a foreign substance is detected during charging (S405), a power limiting operation corresponding to the detection of the foreign substance is performed (S415).

If no foreign matter is detected during charging (S405), and if a problem occurs in power transmission due to a small foreign matter that is not detected, power is limited (e.g., power is cut off) based on a temperature sensor (or thermistor) to protect power transmission (S410). The temperature sensor may be attached to the receiving device or the transmitting device.

Alternatively, even after the power limiting operation in response to foreign matter detection is performed in step S415, if a problem occurs in power transmission due to a minute foreign matter that is not detected, the power is limited based on the temperature sensor (or thermistor) to protect power transmission.

Now, according to the present invention, the operation of detecting a foreign substance is described by distinguishing between before the first charge and after the charge (e.g., using one-way communication or two-way communication).

<1. Foreign substance detection operation before first charge>

Fig. 5 is a flowchart illustrating a method for detecting foreign substances in a wireless power transmission system according to an example of the present invention. This corresponds to step S200 of Fig. 2 or step S300 of Fig. 3.

Referring to FIG. 5, in the ping phase, the wireless power transmission device performs a digital ping, and at this time, the wireless power transmission device transmits a power signal of the operating point to the wireless power reception device (S500).

When receiving a power signal of the ping phase, the wireless power receiving device generates a signal strength packet indicating the strength of the received power signal and transmits it to the wireless power transmitting device (S505). Then, the wireless power receiving device generates an identification packet indicating a unique ID of the wireless power receiving device and configuration information of the wireless power receiving device, and transmits the identification packet and the configuration information to the wireless power transmitting device (S510).

The wireless power receiver measures the received power (S515). From this point on, it enters the stage of setting the initial voltage V _i .

The wireless power receiver determines whether a termination reason, such as overvoltage power (OVP), overcurrent power (OCP), or full charge, has occurred (S520). If OVP, OCP, full charge, or any other type of charging reason has occurred, the wireless power receiver terminates charging (S525). If no type of reason has occurred, the wireless power receiver determines whether it is receiving wireless power from the wireless power transmitter, i.e., whether it is charging (S530).

In step S530, if charging is in progress, the wireless power receiver compares the received power with the required power, generates a power control packet based on the result, and transmits it to the wireless power transmitter (S535). In step S535, if charging is not in progress, the wireless power receiver determines whether the initial voltage V _i is in a hold state (S540). If the normal value of the initial voltage V _i is within the reference voltage range (e.g., 7.0 V to 10.5 V), the initial setting of the wireless power receiver is completed. As a result, the initial voltage V _i is in a hold state, and the wireless power receiver can enter the foreign substance detection phase.

If it is not in the V _i hold state, the wireless power receiver generates a power control packet and transmits it to the wireless power transmitter, just as it would during charging (S535). If it is in the V _i hold state, the wireless power receiver enters the foreign substance detection phase. Here, the wireless power receiver generates a foreign substance status packet and transmits it to the wireless power transmitter (S545).

The foreign substance status packet according to the present invention includes a preamble, a header, a message, and a checksum. The preamble may consist of a minimum of 11 bits and a maximum of 25 bits, and all bits may be set to 0. The preamble is used by the wireless power transmission device to accurately detect the start bit of the header of the foreign substance status packet and synchronize with incoming data.

The header indicates the type of the packet and may consist of 8 bits. As an example, the value of the header of the foreign substance status packet may be '0x00'. In this case, the message may be set to the value 0, i.e., '0x00'. As another example, the value of the header of the foreign substance status packet may be '0x05', which is the same as the header of the charge status packet. However, by setting the value of the 1-byte message of the charge status packet to '0x00', it may be indicated that it is a foreign substance status packet. That is, the foreign substance status packet is included in the charge status packet.

The wireless power transmission device determines whether the received packet is a foreign object packet based on the value of the header or message of the received packet. If a foreign object packet is determined to have been received, the wireless power transmission device performs foreign object detection (S550). The operation of checking for a foreign object packet and detecting the foreign object are performed by the control unit of the wireless power transmission device.

<2. Detection of foreign substances during charging>

<2-1. Detection of foreign substances using one-way communication during charging>

Fig. 6 is a flowchart of the operation of a wireless power transmission system according to another example of the present invention. It corresponds to step S210 of Fig. 2 or step S400 of Fig. 4.

Referring to FIG. 6, the wireless power transmission device searches for a wireless power reception device (S600). At this time, the wireless power transmission device is placed in a charging standby state until a wireless power reception device is found.

If the detected object is a wireless power receiver, the wireless power transmitter enters charging mode and transmits wireless power to the wireless power receiver (S605). In charging mode, the wireless power transmitter applies power to the primary coil, generating an induced magnetic field or resonance.

A wireless power transmission device measures a current flowing in a primary coil, and obtains a current measurement value from the current flowing in the primary coil (S610). The current measured by the wireless power transmission device may be an alternating current. The current measurement value may be converted into a DC value suitable for recognition by a control unit within the wireless power transmission device. That is, the wireless power transmission device measures a relatively high alternating current flowing in the primary coil, and maps the measured high current into a current measurement value, which is a value suitable for interpretation by the control unit, as shown in Table 1.

The wireless power transmission device performs foreign substance detection using one or a combination of two or more of the following parameters: reference current I _ref , reference range (I _low ~ I _high ), reference AC signal, and foreign substance detection time t (S615). In addition, parameters such as reference current I _ref , reference range (I _low ~ I _high ), reference AC signal, and foreign substance detection time t may be stored in advance in the wireless power transmission device as initial setting values.

If no foreign matter is detected, the wireless power transmission device continuously transmits power to the wireless power reception device (S620). Then, the wireless power transmission device obtains the current measurement value of the primary coil again at a time point t predetermined by the system or standard (S610), and based on this, attempts to detect the foreign matter (S615).

On the other hand, when a foreign substance is detected, the wireless power transmission device blocks the wireless power being transmitted to the wireless power reception device (S625).

<2-2. Foreign substance detection using two-way communication during charging>

Fig. 7 is a flowchart illustrating the operation of a wireless power transmission system according to another example of the present invention. It corresponds to step S210 of Fig. 2 or step S400 of Fig. 4.

For example, performing two-way communication means that when power is transmitted from a transmitting device to a receiving device, the receiving device notifies the transmitting device of the received power value, and if the power loss is greater than a predetermined reference value, it is determined as FOD. For example, performing two-way communication means that when a transmitting device transmits 7 to 10 W of power to a receiving device and the receiving device receives 5 W of power, the receiving device notifies the transmitting device of the received power value of '5 W', and if the power loss is greater than 2 W, which is greater than the predetermined reference value of 1 W, it is determined as FOD. Through this, FOD can be detected during the power transmission stage.

Referring to Figure 7, a two-way communication is described in detail. The wireless power transmission device searches for a wireless power reception device (S700). At this time, the wireless power transmission device is placed in a charging standby state until the wireless power reception device is discovered.

If the detected object is a wireless power receiver, the wireless power transmitter enters charging mode and transmits wireless power to the wireless power receiver (S705). In charging mode, the wireless power transmitter applies power to the primary coil, generating an induced magnetic field or resonance.

The wireless power transmitter transmits a transmission power measurement report indicating the measured transmission power to the wireless power receiver (S710). For example, the wireless power transmitter transmits the transmission power measurement report to the wireless power receiver as an FSK signal. Here, the FSK signal refers to a signal transmitted using the FSK method.

The FSK signal may include a simple amount of power (e.g., a transmission power amount). In this case, the wireless power transmission device may transmit the FSK signal at a constant period. This is because the wireless power reception device may not be aware of the transmission time of the FSK signal. The constant period may be a section in which a constant number of data signals are transmitted (e.g., a constant ASK signal).

For example, the above transmission power amount may be a value obtained by measuring the power generated in the main coil according to the AC current signal of the wireless power transmission device.

The above FSK signal refers to a signal that transmits the values 0 and 1 by switching or selecting a variable frequency (e.g., 140 or 140.3 kHz) within a certain range that converts one fixed power frequency (f ₀ , e.g., 145 kHz) required by a receiving device. As another example, it refers to a signal that transmits a data signal including the values 0 and 1 using the phase.

For example, a wireless power transmitter can measure the power generated in the main coil according to an AC current signal, construct a transmission power measurement report indicating the measured generated power, and transmit it to a wireless power receiver. In this way, bidirectional communication is possible, in which control information is transmitted from the wireless power transmitter to the wireless power receiver (for example, the control information can be transmitted as an FSK signal), or in which control information is transmitted from the wireless power receiver to the wireless power transmitter.

The wireless power transmission device performs PWM using an inverter and generates a frequency allowed for the power required (or requested power) of the wireless power reception device.

The required power of a wireless power receiver generates a duty cycle or voltage, and the duty cycle or voltage value is the power value of the wireless power transmitter. In other words, the power of a wireless power transmitter can be expressed by the voltage applied to the inverter, the duty setting, and the frequency.

In the step of transmitting power by a wireless power transmission device, a set value (e.g., voltage, duty frequency) is transmitted to a wireless power reception device as a “transmission power value” using the FSK method.

At this time, the wireless power receiving device stops receiving existing data signals (e.g., ASK signals) and receives FSK signals. For example, the receiving operation of the FSK signal includes a demodulation operation of the FSK signal.

The above FSK signal can be transmitted at a constant cycle (750). For example, the constant cycle (750) can be a transmission period of a predetermined time (e.g., 3 seconds or 5 seconds) or a predetermined number of data signals (e.g., ASK signals).

The above FSK signal may be transmitted simultaneously with wireless power. That is, S705 and S710 may be performed simultaneously.

Next, the wireless power receiver detects foreign matter based on the transmission power measurement report (S715). For example, the wireless power receiver calculates the received power value measured by the wireless power receiver and the FSK signal including the generated power measurement report, and if the difference between them exceeds a predetermined threshold, it determines that there is an FOD. In another example, the wireless power receiver determines that there is an FOD if the 'received power - transmitted power' exceeds a predetermined threshold.

For example, the measured reception power value may be information indicating whether the difference between the power indicated by the transmission power measurement report and the requested power is greater than, equal to, or less than a threshold. For example, if the difference between the power indicated by the transmission power measurement report and the requested power is greater than the threshold, 'reception power measurement result = 1' may be set, and if the difference between the power indicated by the transmission power measurement report and the requested power is less than or equal to the threshold, 'reception power measurement result = 0' may be set. Or conversely, if the difference between the power indicated by the transmission power measurement report and the requested power is greater than or equal to the threshold, 'reception power measurement result = 1' may be set, and if the difference between the power indicated by the transmission power measurement report and the requested power is less than the threshold, 'reception power measurement result = 0' may be set. For example, let's say the threshold is 1W. In the above example, in a situation where the power indicated by the transmission power measurement report is 12W and the requested power is 10W, the difference is 2W, which is greater than the threshold of 1W. In this case, the reception power measurement result indicates 1. If the difference between the power indicated by the transmission power measurement report and the required power is greater than the threshold, this may indicate that a foreign substance has been detected. Accordingly, the wireless power transmission device (40) may recognize this as a declaration of foreign substance detection.

The wireless power receiving device transmits an ASK signal including the result of foreign substance detection to the wireless power transmitting device (S720).

The above ASK signal may include a power control signal, an FOD detection signal, an emergency signal, a buffer signal, etc.

In addition, the ASK signal may include power demand information of the wireless power receiver. The power demand information refers to information that requests the wireless power transmitter to generate wireless power based on a magnetic induction method, and is information that causes the wireless power transmitter to check the power demand information and generate a control signal so that the power indicated by the power demand information is induced. For example, when the power demand information indicates 10W, the wireless power transmitter generates a control signal so that 10W is transmitted.

The above ASK signal can be transmitted in the form of a control error packet, a rectified packet, or a charger state.

Next, the wireless power transmission device can transmit wireless power based on the received ASK signal (S725).

Data signals (e.g., ASK or FSK signals) cannot be transmitted and received simultaneously, so transmission and reception are performed sequentially. Conversely, because power is continuously generated through the induction frequency, simultaneous transmission of power and data signals is possible. Therefore, wireless power can be transmitted simultaneously or at any time, regardless of the timing of ASK and FSK signals being transmitted and received.

According to the above steps S720 and S725, the ASK signal and wireless power can be transmitted and received multiple times.

When a predetermined period (750) has elapsed for step S710, the wireless power transmitter transmits a transmission power measurement report indicating the measured transmission power to the wireless power receiver (S730). For example, the wireless power transmitter transmits the transmission power measurement report to the wireless power receiver as an FSK signal. The predetermined period (750) may be a transmission section of a predetermined time (e.g., 3 seconds or 5 seconds) or a predetermined number of data signals (e.g., ASK signals).

Meanwhile, if a foreign object is detected in the wireless power receiver, the wireless power transmitter can take action to detect the foreign object (not shown in the drawing). For example, the wireless power transmitter can enter a shutdown mode, reducing or stopping the operation of the main coil. This prevents heat generation in the parasitic load and limits or stops the supply of inefficient inductive power.

Figure 8 is a block diagram illustrating a wireless power transmission device according to an example of the present invention.

Referring to FIG. 8, a wireless power transmission device (800) includes a primary coil (810), an electric drive unit (820), a control unit (830), and a current measurement unit (840).

The electric drive unit (820) is connected to the primary coil (810) and applies an electric drive signal, for example, an AC signal, to the primary coil (810) to generate an electromagnetic field.

The control unit (830) is connected to the electric drive unit (820), generates a control signal (831) that controls the AC signal required when the primary coil (810) generates an induced magnetic field or causes magnetic resonance, and inputs the control signal (831) to the electric drive unit (820).

The control unit (830) controls the operation of the wireless power transmission device (800) in the ping phase, ID identification and configuration phase, foreign substance detection phase, and power transmission phase. In addition, the control unit (830) can generate necessary packets in each phase and transmit them to the wireless power reception device, or receive packets from the wireless power reception device.

Here, the ping phase can be defined as an attempt to discover an object capable of receiving wireless power. In the ping phase, the control unit (830) performs a digital ping, and the control unit (830) applies a control signal (831) to the electric drive unit (820) so that the primary coil (810) transmits a power signal at an operating point. Then, when a correct signal strength packet is received from the wireless power receiving device within a specific time window, the control unit (830) transitions the state of the wireless power transmitting device (800) to the ID identification and configuration phase.

Additionally, in the ID identification and configuration phase, the control unit (830) identifies the wireless power receiving device and collects configuration information of the wireless power receiving device. At this time, the control unit (830) receives an identification packet or an identification packet and configuration information from the wireless power receiving device.

In addition, in the foreign object detection phase, the control unit (830) performs foreign object detection (FOD), and if no foreign object is detected, transitions the wireless power transmission device (800) to the power transmission phase and applies a control signal (831) to the electric drive unit (820) so that wireless power is transmitted. On the other hand, if a foreign object is detected, the control unit (830) stops applying the control signal (831) and enters an emergency mode. Accordingly, foreign object detection is performed before the power transmission phase in which the wireless power transmission device (800) actively transmits wireless power to the wireless power reception device. That is, since foreign object detection is performed immediately after the wireless power transmission device (800) and the wireless power reception device complete identification (or recognition) of each other, the risk of performing foreign object detection during wireless power transmission can be prevented in advance.

Although this embodiment separates the foreign substance detection phase and the power transmission phase, the two phases can be integrated and controlled as a single phase. Alternatively, the foreign substance detection phase can be included in the power transmission phase and controlled as a single procedure. In the following description, the foreign substance detection phase is assumed to have an independent status.

The current measuring unit (840) obtains a current measurement value I _measured from the current flowing in the primary coil (810) and inputs it to the control unit (830). The current measurement value I _measured may be converted into a DC value suitable for recognition by the control unit (830). That is, the current measuring unit (840) measures a relatively high alternating current flowing in the primary coil (810), maps the measured high current into a current measurement value I _measured , which is a value suitable for interpretation by the control unit (830), and inputs the current measurement value I _measured to the control unit (830).

Below, the operation performed by each component of the wireless power transmission device (800) to detect a foreign object is specifically disclosed.

When the control unit (830) sends a control signal (831) corresponding to a reference AC signal to the electric drive unit (820), the electric drive unit (820) applies the reference AC signal to the primary coil (810). Here, the reference AC signal may be an experimentally obtained value as an AC signal that allows the transmission efficiency of wireless power to remain in a normal range (or can satisfy the required power level of the receiving device) in an environment without foreign substances, i.e., an environment without any obstacles to wireless power transmission. When the reference AC signal is applied to the primary coil (810), a reference current I _ref flows in the primary coil (810), and at this time, wireless power W _ref is transmitted.

However, if a foreign substance appears between the wireless power transmitter (800) and the wireless power receiver, the wireless power receiver receives only the remaining power W _ref -W _FO excluding the power W _FO consumed by the foreign substance. From the perspective of the wireless power receiver, if it does not receive as much as W _F0 , it transmits a power increase request message to the wireless power transmitter (800) to request more power. The power increase request message may also be called a control error packet. Conversely, if the wireless power receiver receives power exceeding the required power, it can transmit a power decrease request message to the wireless power transmitter (800).

The wireless power receiver can continuously transmit a power increase request message or a power decrease request message to the wireless power transmitter (800) until the required power is satisfied. For example, the wireless power transmitter (800) that receives the power increase request message increases the intensity of the current flowing in the primary coil (810) so that higher power can be transmitted in response thereto. More specifically, in order to allow a greater current to flow in the primary coil (810), the control unit (830) can adjust the control signal (831) so that an AC signal greater than the reference AC signal can be applied to the primary coil (810). This series of processes is collectively referred to as power control.

As a result of power control, a state in which the current measurement value in the primary coil (810) becomes larger than a certain range may occur. If a current I _measured greater than the reference current I _ref flows in the primary coil (810) for transmission of the required power, this means that the transmission efficiency of the wireless power is reduced, and at the same time, this may mean that a certain amount of power is continuously consumed by a foreign substance other than the wireless power receiving device. In this case, when a relatively excessive amount of current flows in the primary coil (810), the control unit (830) determines that a foreign substance exists. That is, the control unit (830) can detect an element that causes an obstacle to the transmission of wireless power, such as a foreign substance such as metal, based on the current measurement value I _measured .

The control unit (830) may use one or a combination of two or more of the following parameters for detecting foreign substances: a reference current I _ref , a reference range (I _low to I _high ), a reference AC signal, and a foreign substance detection time t . Parameters such as the reference current I _ref , the reference range (I _low to I _high ), the reference AC signal, and the foreign substance detection time t may be stored in the control unit (830) as initial values. The reference current I _ref and the reference range (I _low to I _high ) may be referred to as reference values.

As an example, the control unit (830) compares the current measurement value I _measured with the reference current I _ref . If the current measurement value I _measured exceeds the reference current I _ref (i.e., I _measured > I _ref ), it is determined that a foreign substance is detected. On the other hand, if the current measurement value I _measured is less than or equal to the reference current I _ref (i.e., I _measured ≤ I _ref ), it is determined that no foreign substance is present. Here, the reference current I _ref can be defined, for example, as follows, depending on the rated power (W) of the wireless power receiving device.

Rx power
(unit: W) Tx AC current
(unit: A) Max AC current
(unit: A) 2.5 0.998 1.05 3 1.328 1.5 4 1.664 1.85 5 1.925 2.05

Referring to Table 1, when the rated power (W) of the wireless power receiver (Rx) is 2.5 W, 3 W, 4 W, and 5 W, the AC currents flowing in the primary core block of the wireless power transmitter (Tx) are experimentally 0.998 A, 1.328 A, 1.664 A, and 1.925 A, respectively. In addition, the allowable reference currents in the primary core block, i.e., I _ref , are 1.05 A, 1.5 A, 1.85 A, and 2.05 A, respectively.

As another example, the control unit (830) checks whether the current measurement value I _measured falls within the reference range (I _low to I _high ). If the current measurement value I _measured falls within the reference range (i.e., I _low ≤ I _measured ≤ I _high ), it is determined that there is no foreign substance. On the other hand, if the current measurement value I _measured does not fall within the reference range (i.e., I _measured > I _high or I _measured < I _low ), it is determined that a foreign substance has been detected.

The control unit (830) may attempt to detect a foreign substance at a point in time t predetermined by the system or standard.

As an example, the point in time t at which the control unit (830) attempts to detect a foreign substance may be after each power control point in time. For example, after the wireless power transmission device (800) receives a power increase request message or a power decrease request message from the wireless power reception device and increases or decreases the AC signal, the foreign substance detection may be attempted using the current measurement value flowing in the primary coil (810).

As another example, the time point t at which the control unit (830) attempts to detect a foreign substance may be a predetermined, constant detection period. For example, the detection period should be at least shorter than the time it takes for the foreign substance to heat up to a certain temperature or higher. This is because if the foreign substance heats up too much, it may cause serious safety problems such as fire and body burns. Therefore, it is preferable that the detection period be set to a value whose stability has been verified through experiments, thereby preventing various risks that may arise during charging, such as heat generation due to a foreign substance during wireless charging.

When a foreign substance is detected, the control unit (830) controls the electric drive unit (820) to not apply an AC signal to the primary coil (810), thereby blocking the transmission of wireless power.

FIG. 9 is a block diagram illustrating a wireless power transmission device according to another example of the present invention.

Referring to FIG. 9, a wireless power transmission device (900) includes a primary core block (910) including m primary coils (910-1,...910-m), a switching unit (920), an electric drive unit (930), a control unit (940), and a current measurement unit (950).

The switching unit (920) selectively connects all or at least one of the m primary coils (910-1,...910-m) to the electric drive unit (930) by means of a switching method.

The electric drive unit (930) can be connected to m primary coils (910-1,...910-m) via a switching unit (920), and applies electric drive signals to n primary coils (910-1,...310-n) simultaneously or to at least one primary coil selected from among n primary coils (910-1,...310-n) to generate an electromagnetic field.

The control unit (940) is connected to the electric drive unit (930) and generates a control signal (941) that controls the AC signal required when n primary coils (910-1,...310-n) generate an induced magnetic field or cause resonance.

The current measuring unit (950) measures the current flowing through m primary coils (910-1,...910-m) individually or in total. In particular, the current measured by the current measuring unit (840) may be an alternating current. The current measuring unit (840) may be a current sensor. Alternatively, the current measuring unit (840) may be a transformer that reduces the high current flowing through the primary coil to a low current.

As an example, the current measurement unit (950) selects only primary coils in which current flows from m primary coils (910-1,...910-m), individually measures the current flowing in each of the selected primary coils, and obtains a plurality of individual current measurement values I ₁ , I ₂ ,...I _m and inputs them to the control unit (940). The current measurement values I ₁ , I ₂ ,...I _m may be converted into DC values suitable for recognition by the control unit (940). That is, the current measurement unit (950) measures a relatively high alternating current flowing in the primary coil (910-1,...,910-m), maps the measured high current into current measurement values I ₁ , I ₂ ,...I _m , which are suitable values for interpretation by the control unit (940), as shown in Table 1, and inputs the current measurement values I ₁ , I ₂ ,...I _m to the control unit (940).

As another example, the current measuring unit (950) selects only the primary coils in which current flows from m primary coils (910-1,...910-m), measures the current flowing through the entire selected primary coils, and inputs one overall current measurement value I _SELECTED to the control unit (940).

As another example, the current measuring unit (950) measures the total current flowing through all m primary coils (910-1,...910-m) and inputs one total current measurement value I _TOTAL to the control unit (940).

The control unit (940) may use one or a combination of two or more of the following parameters for detecting foreign substances: a reference current I _ref , a reference range (I _{low to} I _{high )} , a reference AC signal, and _a foreign substance detection time t. The following parameters may be stored in the control unit (940) as initial values:

As an example, the control unit (940) compares the current measurement values I ₁ , I ₂ ,...I _m with the reference current I _ref . If at least one of the current measurement values I ₁ , I ₂ ,...I _m exceeds the reference current I _ref (i.e., I ₁ or I ₂ or...I _m > I _ref ), it is determined that a foreign substance is detected. On the other hand, if all of the current measurement values I ₁ , I ₂ ,...I _m are less than or equal to the reference current I _ref (i.e., I ₁ and I ₂ and...I _m ≤ I _ref ), it is determined that no foreign substance is present.

As another example, the control unit (830) checks whether the current measurement values I ₁ , I ₂ ,...I _m each fall within a reference range (I _low to I _high ). If at least one of the current measurement values I ₁ , I ₂ ,...I _m falls within the reference range (i.e., I _low ≤ I ₁ or I ₂ or...I _m ≤ I _high ), it is determined that there is no foreign substance. On the other hand, if all of the current measurement values I ₁ , I ₂ ,...I _m do not fall within the reference range (i.e., I ₁ and I ₂ and...I _m > I _high or I ₁ and I ₂ and...I _m < I _low ), it is determined that a foreign substance is detected.

As another example, the control unit (940) compares the current measurement value I _SELECTED with the reference current I _ref . If the current measurement value I _SELECTED exceeds the reference current I _ref (i.e., I _SELECTED > I _ref ), it is determined that a foreign substance has been detected. On the other hand, if the current measurement value I _SELECTED is less than or equal to the reference current I _ref (i.e., I _SELECTED ≤ I _ref ), it is determined that no foreign substance is present.

As another example, the control unit (940) checks whether the current measurement value I _SELECTED falls within the reference range (I _low to I _high ). If the current measurement value I _SELECTED falls within the reference range (i.e., I _low ≤ I _SELECTED ≤ I _high ), it is determined that there is no foreign matter. On the other hand, if the current measurement value I _SELECTED does not fall within the reference range (i.e., I _SELECTED > I _high or I _SELECTED < I _low ), it is determined that a foreign matter has been detected.

As another example, the control unit (940) compares the current measurement value I _TOTAL with the reference current I _ref . If the current measurement value I _TOTAL exceeds the reference current I _ref (i.e., I _TOTAL > I _ref ), it is determined that a foreign substance has been detected. On the other hand, if the current measurement value I _TOTAL is less than or equal to the reference current I _ref (i.e., I _TOTAL ≤ I _ref ), it is determined that no foreign substance is present.

As another example, the control unit (940) checks whether the current measurement value I _TOTAL falls within the reference range (I _low to I _high ). If the current measurement value I _TOTAL falls within the reference range (i.e., I _low ≤ I _TOTAL ≤ I _high ), it is determined that there is no foreign matter. On the other hand, if the current measurement value I _TOTAL does not fall within the reference range (i.e., I _TOTAL > I _high or I _TOTAL < I _low ), it is determined that a foreign matter has been detected.

The control unit (940) may attempt to detect a foreign substance at a predetermined time t by the system or standard.

As an example, the point in time t at which the control unit (940) attempts to detect a foreign substance may be after each power control point in time. For example, after the wireless power transmission device (900) receives a power increase request message or a power decrease request message from the wireless power reception device and increases or decreases the AC signal, the foreign substance detection may be attempted using the current measurement value flowing in the primary core block (910).

As another example, the time point t at which the control unit (940) attempts to detect a foreign substance may be a predetermined, constant detection period. For example, the detection period should be at least shorter than the time it takes for the foreign substance to heat up to a certain temperature or higher. This is because if the foreign substance heats up too much, it may cause serious safety problems such as fire and body burns. Therefore, it is preferable that the detection period be set to a value whose stability has been verified through experiments, thereby preventing various risks that may arise during charging, such as heat generation due to a foreign substance during wireless charging.

When a foreign substance is detected, the control unit (940) controls the electric drive unit (930) to not apply an AC signal to the primary core block (910), thereby blocking the transmission of wireless power.

The wireless power transmission device (110) of FIG. 1 may be the wireless power transmission device (800) of FIG. 8 or the wireless power transmission device (900) of FIG. 9.

According to the present invention, signaling overhead can be reduced because the wireless power receiving device does not need to transmit specific information to the wireless power transmitting device based on the promised information transmission standard for foreign substance detection.

Detecting a foreign substance with minimal delay before it generates heat is a very important technical issue. This is because, if the foreign substance is easily heated by nature, a long delay until detection of the foreign substance can cause serious problems. However, according to the present invention, since the wireless power transmission device can detect the foreign substance on its own, there is an effect that the delay for detecting the foreign substance, such as the time for the wireless power reception device to generate specific information, the time for the specific information to be transmitted to the wireless power transmission device, and the time for the wireless power transmission device to decode and interpret the specific information, is unnecessary.

Furthermore, even if the wireless power receiving device is a low-version model that cannot transmit the specific information, the wireless power transmission system according to the present invention can provide compatibility with the model.

FIG. 10 is a block diagram illustrating a wireless power receiving device according to an example of the present invention.

Referring to FIG. 10, a wireless power receiving device (1000) includes a secondary coil (1010), a rectifying unit (1020), and a control unit (1030).

The rectifier unit (1020) provides full-wave rectification for the AC waveform generated by the secondary coil (1010). For example, the rectifier unit (1020) may use four diodes in a full-fridge configuration. The rectifier unit (1020) may also provide power to the control unit (1030) and an external load (1040).

The control unit (1030) receives power from the rectifier unit (1020) and performs operations such as packet generation and transmission in each phase and wireless power transmission control. As an example, a load modulation technique may be used to transmit packets. In this case, packets are transmitted through the secondary coil (1010), and the same frequency band as the frequency band for wireless power transmission is used. As another example, a separate frequency band different from the frequency band for wireless power transmission is used to transmit packets, and the packets may be transmitted through techniques such as RFID (radio frequency identification), Bluetooth, or NFC (near field communication).

In the ID identification and configuration phase, the control unit (1030) generates an identification packet indicating a unique ID of the wireless power receiving device (1000) and configuration information of the wireless power receiving device (1000), and transmits the identification packet and configuration information to the wireless power transmitting device.

And the control unit (1030) can measure the initial voltage V _i of the output terminal connected to the external load. The initial voltage V _i is a voltage measured by the control unit (1030) before the power transmission phase for receiving wireless power after completing the ID identification and configuration phase. Alternatively, the initial voltage V _i may be defined as the voltage of the output terminal in a standby state before wireless charging starts.

If the steady-state value of the initial voltage V _i is within the reference voltage range (e.g., 7.0 V to 10.5 V), the control unit (1030) enters the foreign object detection phase and generates a foreign object status packet for foreign object detection and transmits it to the wireless power transmission device. The foreign object status packet is used to initiate or trigger foreign object detection in the wireless power transmission device.

In the power transmission phase, the control unit (1030) can measure the power received through the secondary coil (1010), generate a power control packet, and transmit it to the wireless power transmission device. That is, the control unit (1030) can receive the required power using the packet required for wireless power transmission control.

All of the functions described above can be performed by a processor such as a microprocessor, controller, microcontroller, ASIC (Application Specific Integrated Circuit), etc., according to software or program code coded to perform the functions described above. The design, development, and implementation of the code will be apparent to those skilled in the art based on the description of the present invention.

Although the present invention has been described with reference to specific embodiments, those skilled in the art will appreciate that various modifications and variations can be made to the present invention without departing from the technical spirit and scope of the invention. Therefore, the present invention is not limited to the above-described embodiments, and encompasses all embodiments within the scope of the following claims.

Claims (10)

In a method for detecting foreign substances in a wireless power receiving device,
A step of performing a foreign substance detection operation before charging; and
Step for performing foreign substance detection during charging using two-way communication
Including,
The step of performing a foreign substance detection operation during charging using the above two-way communication is as follows:
A step of receiving a transmission power measurement report indicating measured transmission power from a wireless power transmission device that generates an induced magnetic field or resonance by applying power to a primary coil in a charging mode;
A step of detecting a foreign substance based on the difference between the measured transmission power and the measured reception power; and
A step of transmitting an ASK signal including the foreign substance detection result to the wireless power transmission device.
A method comprising: In the first paragraph, the transmission power measurement report is transmitted as an FSK signal transmitted using the FSK method,
A method wherein the above FSK signal includes a transmission power amount measured by the power generated in the primary coil according to an AC signal. In the second paragraph,
The above FSK signal is transmitted repeatedly at regular intervals,
A method, characterized in that the above predetermined period is a section in which a predetermined number of data signals are transmitted. In the second paragraph,
A method characterized in that the above FSK signal is a signal that transmits 0 or 1 by switching or selecting a variable frequency within a certain range that converts a required fixed power frequency. In the first paragraph,
A method wherein the ASK signal includes power demand information, which is information requesting the wireless power transmission device to generate wireless power based on a magnetic induction method. As a wireless power receiving device for detecting foreign substances,
A secondary core block that receives wireless power from a wireless power transmission device by coupling with a primary core block provided in the wireless power transmission device through magnetic induction or magnetic resonance;
A rectifier unit connected to the secondary core block and performing full-wave rectification on an AC waveform generated from the secondary core block to provide power to the control unit and an external load; and
A control unit that measures the voltage of the output terminal connected to the external load and controls the wireless power receiving device to enter a foreign substance detection phase when the voltage exists within the reference voltage range.
Including,
The above control unit performs a foreign substance detection operation before charging and performs a foreign substance detection operation during charging using two-way communication.
The control unit receives a transmission power measurement report indicating measured transmission power from the wireless power transmission device that applies power to a primary coil in a charging mode to generate an induced magnetic field or resonance, detects a foreign substance based on a difference value between the measured transmission power and the measured reception power, and controls the wireless power reception device to transmit an ASK signal including the foreign substance detection result, thereby performing a foreign substance detection operation during charging using the two-way communication. In the 6th paragraph, the transmission power measurement report is transmitted as an FSK signal transmitted using the FSK method,
A wireless power receiving device, wherein the FSK signal includes a transmission power amount measured by the power generated in the primary coil according to an AC signal. In paragraph 7,
The above FSK signal is transmitted repeatedly at regular intervals,
A wireless power receiving device, characterized in that the above predetermined period is a section in which a predetermined number of data signals are transmitted. In paragraph 7,
A wireless power receiving device characterized in that the above FSK signal is a signal that transmits 0 or 1 by switching or selecting a variable frequency of a certain range that converts a required fixed power frequency. In paragraph 6,
A wireless power receiving device, wherein the ASK signal includes required power information, which is information requesting the wireless power transmitting device to generate wireless power based on a magnetic induction method.