KR102653290B1 - Apparatus and method for detecting foreign object in wireless power transmitting system - Google Patents

Abstract

The present invention relates to an apparatus and method for detecting foreign matter in a wireless power transmission system. This specification performs a foreign matter detection operation before initial charging, if a foreign matter is not detected until charging is initiated, a foreign matter detection operation is performed during charging, and if a foreign matter is not detected while receiving the power signal, the temperature sensor Includes limiting power based on

Description

Apparatus and method for detecting foreign objects in a wireless power transmission system {APPARATUS AND METHOD FOR DETECTING FOREIGN OBJECT IN WIRELESS POWER TRANSMITTING SYSTEM}

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

Generally, in order for a portable terminal such as a mobile phone, laptop, or PDA to be charged, the portable terminal must receive electrical energy (or power) from an external charger. These portable terminals include battery cells that store supplied electrical energy and circuits for charging and discharging the battery cells (supplying electrical energy to the portable terminal).

The electrical connection method between a charger and a battery cell to charge electric energy to a battery cell is to receive commercial power, convert it into voltage and current corresponding to the battery cell, and supply electric energy to the battery cell through the terminal of the battery cell. Includes terminal supply method.

This terminal supply method involves the use of physical cables or wires. Therefore, when handling a lot of terminal-supplied equipment, many cables take up a considerable amount of work space, are difficult to organize, and do not look good. In addition, the terminal supply method can cause problems such as instantaneous discharge phenomenon due to different potential differences between terminals, burnout and fire caused by foreign substances, natural discharge, and deterioration of the life and performance of the battery pack.

Recently, in order to solve the above problems, charging systems (hereinafter referred to as wireless power transmission systems) and control methods using a wireless power transmission method have been proposed. The wireless power transmission method is also called a contactless power transmission method or a no point of contact power transmission method. The wireless power transmission system consists of a wireless power transmission device that supplies electrical energy through a wireless power transmission method and a wireless power reception device that charges battery cells by receiving electrical energy wirelessly supplied from the wireless power transmission device.

In the terminal supply method, as long as the terminal connection is made between the charger and the terminal, there is not a high possibility that there will be obstacles such as foreign substances that interfere with charging. On the other hand, due to the wireless power transmission system's non-contact charging characteristics, foreign substances may be inserted between the wireless power receiving device and the wireless power transmitting device during charging. If foreign substances such as metal get caught between the wireless power transmitter and the wireless power receiver, the foreign substances may not only prevent power transmission, but may also cause problems such as overload and product damage or explosion due to heat generation by the foreign substances. there is. Therefore, a device and method that can detect foreign substances in a wireless power transmission system is required.

The technical object of the present invention is to provide an apparatus 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 foreign substances in the initial recognition stage.

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

Another technical object of the present invention is to provide an apparatus and method for limiting power in response to detection of foreign substances in a wireless power transmission system.

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

According to one aspect of the present invention, a method of detecting a foreign substance in a wireless power receiver includes performing a foreign substance detection operation before initial charging, and if the foreign substance is not detected until charging is initiated, using one-way communication or two-way communication. A step of performing a foreign matter detection operation during charging, and if no foreign matter is detected in the foreign matter detection operation during charging, a step of detecting the undetected fine foreign matter with a temperature sensor and limiting power.

According to another aspect of the present invention, a wireless power receiving device for detecting foreign substances receives wireless power from the wireless power transmitting device by combining with the primary core block provided in the wireless power transmitting device through magnetic induction or magnetic resonance. A secondary core block, connected to the secondary core block, and performing full-wave rectification on the AC waveform generated by the secondary core block to provide power to the control unit and external load. It includes a control unit that measures the initial voltage of the output terminal connected to the unit and the external load, and controls the wireless power receiver to enter a foreign matter detection phase when the initial voltage is within the reference voltage range; , the control unit performs a foreign matter detection operation before initial charging, or, if a foreign matter is not detected until charging is initiated, performs a foreign matter detection operation during charging using one-way communication or two-way communication, or a foreign matter detection operation during charging. If no foreign matter is detected, the undetected fine foreign matter is detected with a temperature sensor and the power is limited.

Since the wireless power transmission device according to the present invention can detect foreign substances at any point during charging before starting charging, the probability of detecting foreign substances may increase. In addition, the method of detecting foreign substances at each stage is clearly defined, making it easier to implement detection of foreign substances. Furthermore, the wireless power transmitter can detect foreign substances based on information exchanged with the wireless power receiver, or it can detect foreign substances on its own without the information, making it possible to detect foreign substances compatible with various products. In this way, when a foreign substance is detected, damage to the device caused by the foreign substance can be prevented by stopping wireless power transmission or having the user remove the foreign substance.

Figure 1 shows components of a wireless power transmission system according to an example of the present invention.
Figure 2 is a flowchart showing a method of detecting foreign matter in a wireless power transmission system according to an example of the present invention.
Figure 3 is a flowchart showing a method of detecting foreign matter in a wireless power transmission system according to another example of the present invention.
Figure 4 is a flowchart showing a method of detecting foreign matter in a wireless power transmission system according to another example of the present invention.
Figure 5 is a flowchart explaining a method of detecting foreign matter 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 showing a wireless power transmission device according to an example of the present invention.
Figure 9 is a block diagram showing a wireless power transmission device according to another example of the present invention.
Figure 10 is a block diagram showing a wireless power reception device according to an example of the present invention.

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

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

Referring to FIG. 1, the 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 form, but one preferred form is a flat platform with a power transmission surface, on or near which each wireless power reception device 150-1, ...,150-n) can be located.

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 is It is provided with a secondary core block that is coupled to the electromagnetic field generated by the primary core block of the wireless power transmission device 110 when near the wireless power transmission device 110. The secondary core block may include a core and one or more secondary coils.

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

The wireless power receiving devices 150-1,..., 150-n are usually connected to an external load (not shown, also referred to as the actual load of the wireless power receiving device), and are transmitted wirelessly from the wireless power transmitting device 110. The received power is supplied to external loads. For example, the wireless power receiving devices 150-1,..., 150-n can be transported as objects that consume or store power, such as portable electric or electronic devices or rechargeable battery cells or batteries, respectively.

Figure 2 is a flowchart showing a method for detecting foreign matter in a wireless power transmission system according to an example of the present invention.

Referring to FIG. 2, a foreign matter detection operation is performed before initial charging (S200). As an example, the foreign matter detection operation before initial charging is shown in Figure 5.

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

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

As an example, foreign substances can be detected by performing one-way communication during charging. As an example, the foreign matter detection operation using one-way communication during charging is shown in FIG. 6.

As another example, foreign substances 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 shown in FIG. 7.

As another example, foreign matter may be detected by performing the one-way communication and the two-way communication simultaneously or independently during charging.

If a foreign object is detected during charging (S215), a power limiting operation in response to the foreign object detection is performed as in step S225.

If a foreign substance is not detected during charging (S215), if a problem occurs in power transmission due to a fine undetected foreign substance, the power is limited based on the temperature sensor (or thermistor) to protect power transmission (e.g., cut off the power) )(S220). The temperature sensor may be attached to a receiving device or may be attached to a 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 fine undetected foreign matter, the power is limited based on the temperature sensor (or thermistor) to protect power transmission.

Figure 3 is a flowchart showing a method of detecting foreign matter in a wireless power transmission system according to another example of the present invention.

Referring to FIG. 3, a foreign matter detection operation is performed before initial charging (S300). As an example, the foreign matter detection operation before initial charging is shown in Figure 5.

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

If foreign substances are not detected before initial charging (S305), if there is a problem with power transmission due to fine undetected foreign substances, the power is limited based on the temperature sensor (or thermistor) to protect power transmission (e.g., power Hang up)(S310). The temperature sensor may be attached to a receiving device or may be attached to a 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 fine foreign matter that has not been detected, the power is limited based on a temperature sensor (or thermistor) to protect power transmission.

Figure 4 is a flowchart showing a method of detecting foreign matter in a wireless power transmission system according to another example of the present invention.

Referring to FIG. 4, when charging begins, a foreign matter detection operation is performed during charging (S400).

As an example, foreign substances can be detected by performing one-way communication during charging. As an example, the foreign matter detection operation using one-way communication during charging is shown in FIG. 6.

As another example, foreign substances 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 shown in FIG. 7.

As another example, foreign matter may be detected by performing the one-way communication and the two-way communication simultaneously or independently during charging.

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), if there is a problem with power transmission due to fine foreign matter that has not been detected, the power is limited based on the temperature sensor (or thermistor) to protect power transmission (e.g., cut off power) )(S410). The temperature sensor may be attached to a receiving device or may be attached to a 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 fine foreign matter that has not been detected, the power is limited based on a temperature sensor (or thermistor) to protect power transmission.

Now, the operation of detecting foreign substances according to the present invention will be described separately before and after initial charging (e.g., using one-way communication or two-way communication).

<1. Foreign matter detection operation before initial charging>

Figure 5 is a flowchart explaining a method of detecting foreign matter 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 digital ping, and at this time, the wireless power transmission device transmits a power signal at 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 received strength of the 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 configuration information to the wireless power transmitting device (S510).

The wireless power receiving device measures the received power (S515). From this point on, the step of setting the initial voltage V _i is entered.

The wireless power receiver determines whether a reason for termination occurs, such as over voltage power (OVP), over current power (OCP), or full charge (S520). If OVP, OCP, full charge, or any other type of charging reason occurs, the wireless power receiving device terminates charging (S525). If the type reason does not occur, the wireless power receiving device determines whether it is receiving wireless power from the wireless power transmitting device, that is, charging (S530).

If it is charging in step S530, the wireless power receiving device compares the received power with the required power, generates a power control packet based on the result, and transmits it to the wireless power transmitting device (S535). If it is not charging in step S535, the wireless power receiving device determines whether the initial voltage V _i is in a hold state (S540). If the steady-state value of the initial voltage V _i is within the reference voltage range (for example, 7.0V to 10.5V), the initial setup of the wireless power receiving device is completed. As a result, the initial voltage _Vi is in a hold state, and the wireless power receiving device can enter the foreign matter detection phase.

If V _i is not in the hold state, the wireless power receiving device generates a power control packet and transmits it to the wireless power transmitting device as in the case of charging (S535). If V _i is in the hold state, the wireless power receiver enters the foreign matter detection phase. Here, the wireless power receiving device generates a foreign matter status packet and transmits it to the wireless power transmitting device (S545).

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

The header indicates the type of packet and can be composed of 8 bits. As an example, the value of the header of the foreign matter status packet may be '0x00'. In this case, the message may have its value set to 0, that is, '0x00'. As another example, the header value of the foreign matter status packet may be '0x05', which is the same as the header of the charge status packet. However, the value of the 1-byte message of the charging state packet is set to '0x00', thereby indicating that it is a foreign matter state packet. That is, the foreign matter status packet is included in the charging status packet.

The wireless power transmission device determines whether the received packet is a foreign object packet based on the header or message value of the received packet. And if it is determined that the foreign matter status packet has been received, the wireless power transmission device performs foreign matter detection (S550). The operation of checking the foreign matter status packet and detection of the foreign matter are performed by the control unit of the wireless power transmission device.

<2. Foreign object detection during charging>

<2-1. Foreign matter detection using one-way communication during charging>

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

Referring to FIG. 6, the wireless power transmitter searches for the wireless power receiver (S600). At this time, the wireless power transmitting device is in a charging standby state until the wireless power receiving device is searched.

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 to generate an induced magnetic field or resonance.

The wireless power transmitter measures the current flowing in the primary coil, and the wireless power transmitter 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 alternating current. The current measurement value may be converted to a DC value suitable for recognition by the control unit in 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 to a current measurement value that is suitable for interpretation by the control unit, as shown in Table 1.

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

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

On the other hand, when a foreign substance is detected, the wireless power transmitter blocks the wireless power transmitted to the wireless power receiver (S625).

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

Figure 7 is an operation flowchart of a wireless power transmission system according to another example of the present invention. This 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 informs the transmitting device of the received power value, and if the power loss is greater than a predetermined standard value, it is determined to be FOD. It says what to do. For example, performing two-way communication means that if 7 to 10W of power is transmitted from the transmitting device to the receiving device and the receiving device receives 5W of power, the received power value '5W' is notified to the transmitting device, and the power loss is 2W. Since it is greater than the predetermined standard value of 1W, it is judged as FOD. Through this, FOD can be detected in the power transmission stage.

To describe the two-way communication in detail with reference to FIG. 7, the wireless power transmitter searches for the wireless power receiver (S700). At this time, the wireless power transmitting device is in a charging standby state until the wireless power receiving device is searched.

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 to generate an induced magnetic field or resonance.

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

The FSK signal may include a simple amount of power (eg, amount of transmit power). At this time, the wireless power transmission device can transmit the FSK signal at a constant cycle. This is because the wireless power receiving device may not know the transmission time of the FSK signal. The constant period may be a section in which a certain number of data signals are transmitted (eg, the ASK signal is constant).

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

The FSK signal switches or selects a certain range of variable frequencies (e.g., 140 or 140.3Khz) that converts one fixed power frequency (f ₀ , e.g., 145kHz) required by the receiving device. So, it refers to a signal that transmits 0 and 1 values. As another example, it refers to a signal that transmits a data signal containing 0 and 1 values using phase.

As an example, the wireless power transmission device can measure the power generated in the main coil according to the AC current signal, construct a transmission power measurement report indicating the measured generated power, and transmit it to the wireless power reception device. In this way, control information may be transmitted through a path from the wireless power transmission device to the wireless power reception device (for example, control information may be transmitted as an FSK signal), or through a path from the wireless power reception device to the wireless power transmission device. Two-way communication in which control information is transmitted is possible.

The wireless power transmitter performs PWM using an inverter and generates a frequency allowed for the required power (or required power) of the wireless power receiver.

The required power of the wireless power receiving device generates a duty cycle or voltage, and the duty cycle or voltage value is the power value of the wireless power transmitting device. In other words, the power of the wireless power transmission device can be expressed as the voltage applied to the inverter, duty setting, and frequency.

In the step of transmitting power, the wireless power transmitter transmits a “transmission power value” of a set value (e.g., voltage, duty frequency) to the wireless power receiver using the FSK method.

At this time, the wireless power receiving device stops receiving the existing data signal (eg, ASK signal) and receives the FSK signal. As an example, a reception operation of an FSK signal includes a demodulation operation of the FSK signal.

The FSK signal may be transmitted at regular intervals (750). For example, the constant period 750 may be a transmission period of a predetermined time (eg, 3 seconds and 5 seconds) or a predetermined number of data signals (eg, ASK signal).

The 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 substances based on the transmission power measurement report (S715). For example, the FSK signal including the received power value measured by the wireless power receiver and the generated power measurement report is calculated, and if the difference value is greater than a predetermined reference value, it is determined to be FOD. As another example, the wireless power receiving device determines it to be FOD if 'received power - transmitted power' is greater than a predetermined standard value.

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

The wireless power receiver transmits an ASK signal including the foreign substance detection result to the wireless power transmitter (S720).

The ASK signal may include a power control signal, FOD detection signal, emergency signal, or buffer signal.

Additionally, the ASK signal may include required power information of the wireless power receiver. Required power information refers to information that requires a wireless power transmitter to generate wireless power based on magnetic induction. The wireless power transmitter checks the required power information and sends a control signal to induce the power indicated by the required power information. This is information that causes it to occur. For example, when the required power information indicates 10W, the wireless power transmitter generates a control signal to transmit 10W.

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

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

Since it is impossible to simultaneously transmit and receive a data signal (eg, ASK signal or FSK signal), transmission or reception is performed sequentially. On the other hand, because power continues to be generated through the induced frequency, it is possible for the power signal and data signal to be transmitted simultaneously. Therefore, wireless power can be transmitted simultaneously or at any time, regardless of when the ASK signal and the FSK signal are transmitted and received.

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

When a certain period (750) has elapsed in step S710, the wireless power transmission device transmits a transmission power measurement report indicating the measured transmission power to the wireless power reception device (S730). For example, the wireless power transmission device transmits a transmission power measurement report as an FSK signal to the wireless power reception device. The constant period 750 may be a transmission period of a predetermined time (eg, 3 seconds and 5 seconds) or a predetermined number of data signals (eg, ASK signal).

Meanwhile, if it is determined that a foreign substance has been detected in the wireless power receiving device, the wireless power transmitting device may take action to detect the foreign material (not shown). For example, the wireless power transmission device may enter a blocking mode in which operation of the main coil is reduced or stopped. This prevents the parasitic load from generating heat, and the supply of inefficient induced power can be limited or stopped.

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

Referring to FIG. 8, the 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, such as 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 and 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. , which is input to the electric drive unit 820.

The control unit 830 controls operations in the ping phase, ID identification and configuration phase, foreign matter detection phase, and power transmission phase of the wireless power transmitter 800. Additionally, the control unit 830 may generate packets necessary for each phase and transmit them to the wireless power receiver, or receive packets from the wireless power receiver.

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, where the control unit 830 controls the primary coil 810 to transmit a power signal at an operating point. A signal 831 is applied to the electric drive unit 820. And when a correct signal strength packet is received from the wireless power receiver within a specific time window, the control unit 830 identifies the status of the wireless power transmitter 800 by ID and Transition to 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 identification packet and configuration information from the wireless power receiver.

Additionally, in the foreign object detection phase, the control unit 830 performs foreign object detection (FOD), and when no foreign object is detected, transitions the wireless power transmitter 800 to the power transmission phase, and the wireless power is The control signal 831 is applied to the electric drive unit 820 to be transmitted. On the other hand, when a foreign substance is detected, the control unit 830 stops applying the control signal 831 and enters an emergency mode. According to this, foreign matter is detected before the power transmission phase in which the wireless power transmitter 800 transmits wireless power to the wireless power receiver in earnest. In other words, since foreign matter detection is performed immediately after the wireless power transmitter 800 and the wireless power receiver complete identification (or recognition) of each other, the risk of foreign matter detection during wireless power transmission is prevented in advance. It can be prevented.

In this embodiment, the foreign matter detection phase and the power transmission phase are separated, but the two phases can be integrated and controlled as one phase. Alternatively, the foreign matter detection phase may belong to the power transmission phase and be controlled through one procedure. Hereinafter, the foreign matter detection phase will be described as having an independent status.

The current measurement 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 to a DC value suitable for recognition by the control unit 830. That is, the current measurement unit 840 measures a relatively high alternating current flowing in the primary coil 810, and maps the measured high current to a current measurement value I _measured, which is a value suitable for interpretation by the control unit 830 ( mapping), and the current measured value I _measured is input to the control unit 830.

Below, the operation performed by each component of the wireless power transmission device 800 to detect foreign objects will be described in detail.

When the control unit 830 sends the control signal 831 corresponding to the 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 is used to ensure that the transmission efficiency of wireless power remains within the normal range (or that can satisfy the required power level of the receiving device) in an environment without foreign substances, that is, in an environment without obstacles to wireless power transmission. It may be a value obtained experimentally as an AC signal. When a 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 only receives W _ref -W _FO , which is the remaining power excluding the power W _FO consumed by the foreign substance. From the perspective of the wireless power receiver, if W _F0 is not received, a power increase request message is transmitted to the wireless power transmitter 800 to request more power. The power increase request message may also be called a control error packet. Conversely, when the wireless power receiving device receives power exceeding the required power, a power down request message may be transmitted to the wireless power transmitting device 800.

The wireless power receiving device may continuously transmit a power increase request message or a power decrease request message to the wireless power transmitting device 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 is transmitted in response. More specifically, in order to allow a larger current to flow in the primary coil 810, the control unit 830 applies a control signal 831 so that an AC signal larger than the reference AC signal can be applied to the primary coil 810. ) can be adjusted. This series of processes is collectively referred to as power control.

As a result of power control, a state may occur in which the current measured value in the primary coil 810 becomes greater than a certain period. The fact that I _measured , which is a larger current than the reference current I _ref , is flowing in the primary coil 810 for transmission of the required power means that the transmission efficiency of wireless power is reduced, and at the same time, it is harmful to foreign substances other than the wireless power receiver. This may mean that a certain amount of power is being consumed continuously. In this way, when relatively excessive current flows through the primary coil 810, the control unit 830 determines that foreign matter exists. That is, the control unit 830 can detect elements that cause interference in wireless power transmission, for example, foreign substances such as metal, based on the current measurement value I _measured .

The control unit 830 may use any one or a combination of two or more of parameters such as a reference current I _ref , a reference range (I _low to I _high ), a reference AC signal, and a foreign matter detection time t to detect foreign matter. And parameters such as reference current I _ref , reference range (I _low to I _high ), reference AC signal, and foreign matter detection time t may be stored in the control unit 830 as initial setting values. The reference current I _ref and the reference range (I _low to I _high ) may be called a reference value.

As an example, control unit 830 compares the current measurement I _measured with a reference current I _ref . And 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 has been detected. On the other hand, if the current measurement value I _measured is less than the reference current I _ref (i.e., I _measured ≤ I _ref ), it is determined that there is no foreign matter. Here, the reference current I _ref can be defined as follows, for example, depending on the rated power (W) of the wireless power receiver.

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 2.5W, 3W, 4W, and 5W, the AC current flowing in the primary core block of the wireless power transmitter (Tx) is experimentally They are 0.998A, 1.328A, 1.664A, and 1.925A, respectively. And, the size of the reference current allowed in the primary core block, that is, I _ref, is 1.05A, 1.5A, 1.85A, and 2.05A, 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 ). And if the current measurement value I _measured falls within the standard range (i.e., I _low ≤ I _measured ≤ I _high ), it is determined that there is no foreign matter. On the other hand, if the current measurement value I _measured does not fall within the standard 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 the foreign object at a time point t predetermined by the system or standard.

As an example, the time point t at which the control unit 830 attempts to detect foreign matter may be after every power control time point. For example, after the wireless power transmitter 800 receives a power increase request message or a power decrease request message from the wireless power receiver and increases or decreases the AC signal, the current measured value flowing in the primary coil 810 You can try to detect foreign substances using .

As another example, the time point t at which the control unit 830 attempts to detect foreign matter may be a predetermined constant detection period. For example, the detection period should be at least shorter than the time it takes for a foreign substance to heat up above a certain temperature. This is because if the heat generation of foreign substances becomes severe, it can cause serious safety problems such as fire and burns of the body. Therefore, it is desirable to set the detection cycle to a value whose stability has been verified through experimentation, which can prevent various risks that may occur during charging, such as heat generation due to foreign substances during wireless charging.

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

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

Referring to FIG. 9, the wireless power transmission device 900 includes a primary core block 910 including m primary coils 910-1,...910-m, a switching unit 920, and an electric drive. It includes a 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 a switching method.

The electric drive unit 930 may be connected to the m primary coils 910-1,...910-m through the switching unit 920, and may be connected to the n primary coils 910-1 to generate an electromagnetic field. ,...310-n) simultaneously or to at least one primary coil selected from among the n primary coils 910-1,...310-n.

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

The current measurement unit 950 measures the current flowing through the m primary coils 910-1,...910-m individually or in sum. In particular, the current measured by the current measurement unit 840 may be alternating current. Current measurement unit 840 may be a current sensor. Alternatively, the current measurement unit 840 may be a transformer that lowers the high current flowing in the primary coil to a low current.

As an example, the current measurement unit 950 selects only the primary coil through which the current flows among the m primary coils 910-1,...910-m, and individually measures the current flowing in each selected primary coil. And, a number of individual current measurement values I ₁ , I ₂ ,...I _m are obtained and input to the control unit 940. The current measurement values I ₁ , I ₂ ,...I _m may be converted to 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 coils 910-1,...,910-m, and is suitable for the control unit 940 to interpret the measured high current. The numerical current measurement values I ₁ , I ₂ ,...I _m are mapped as shown in Table 1, and the current measurement values I ₁ , I ₂ ,...I _m are input to the control unit 940. do.

As another example, the current measurement unit 950 selects only the primary coil through which the current flows among the m primary coils 910-1,...910-m, measures the current flowing through all of the selected primary coils, and , one total current measurement value I _SELECTED is input to the control unit 940.

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

The control unit 940 may use any one or a combination of two or more of parameters such as a reference current I _ref , a reference range (I _low to I _high ), a reference AC signal, and a foreign matter detection time t to detect foreign matter. And parameters such as reference current I _ref , reference range (I _low to I _high ), reference AC signal, and foreign matter detection time t may be stored in the control unit 940 as initial setting values.

As an example, the control unit 940 compares the current measurements I ₁ , I ₂ ,...I _m with the reference current I _ref , respectively. And 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 ), foreign matter It is judged that this has been detected. On the other hand, if the current measurement values I ₁ , I ₂ ,...I _m are all less than the reference current I _ref (i.e., I ₁ and I ₂ and...I _m ≤ I _ref ), it is determined that there is no foreign matter. .

As another example, the control unit 830 checks whether the current measurement values I ₁ , I ₂ ,...I _m fall within the reference range (I _low to I _high ), respectively. And if at least one of the current measurement values I ₁ , I ₂ ,...I _m falls within the standard range (i.e., I _low ≤ I ₁ or I ₂ or ...I _m ≤ I _high ), it is considered that there is no foreign matter. judge. On the other hand, if the current measurements I ₁ , I ₂ ,...I _m do not all 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 has been detected.

As another example, control unit 940 compares the current measurement I _SELECTED with the reference current I _ref . And 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 the reference current I _ref (i.e., I _SELECTED ≤ I _ref ), it is determined that there is no foreign matter.

As another example, control unit 940 checks whether the current measurement value I _SELECTED falls within the reference range (I _low to I _high ). And if the current measurement value I _SELECTED falls within the standard 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 standard range (i.e., I _SELECTED > I _high or I _SELECTED < I _low ), it is determined that a foreign substance has been detected.

As another example, control unit 940 compares the current measurement I _TOTAL to a reference current I _ref . And 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 the reference current I _ref (i.e., I _TOTAL ≤ I _ref ), it is determined that there is no foreign matter.

As another example, control unit 940 checks whether the current measurement value I _TOTAL falls within the reference range (I _low to I _high ). And if the current measurement value I _TOTAL falls within the standard 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 standard range (i.e., I _TOTAL > I _high or I _TOTAL < I _low ), it is determined that a foreign substance has been detected.

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

As an example, the time point t at which the control unit 940 attempts to detect foreign matter may be after every power control time point. For example, after the wireless power transmitter 900 receives a power increase request message or a power decrease request message from the wireless power receiver and increases or decreases the AC signal, the current flowing in the primary core block 910 is measured. You can try to detect foreign substances using the value.

As another example, the time point t at which the control unit 940 attempts to detect foreign matter may be a predetermined constant detection period. For example, the detection period should be at least shorter than the time it takes for a foreign substance to heat up above a certain temperature. This is because if the heat generation of foreign substances becomes severe, it can cause serious safety problems such as fire and burns of the body. Therefore, it is desirable to set the detection cycle to a value whose stability has been verified through experimentation, which can prevent various risks that may occur during charging, such as heat generation due to foreign substances during wireless charging.

When a foreign substance is detected, the control unit 940 controls the electric drive unit 930 not to apply an AC signal to the primary core block 910 to block 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 detecting foreign substances.

Detecting foreign substances with minimal delay before they generate heat is a very important technical issue. This is because, if the nature of the foreign material is such that it easily generates heat, a prolonged delay until the foreign material is detected can cause serious problems. However, according to the present invention, since the wireless power transmitter can detect foreign substances on its own, there is a delay for detecting foreign substances, for example, the time when the wireless power receiver generates specific information, and the specific information is transmitted through wireless power. This has the effect of eliminating the need for transmission time to the device and time for the wireless power transmission device to decode and interpret the specific information.

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 even for the model.

Figure 10 is a block diagram showing a wireless power reception device according to an example of the present invention.

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

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

The control unit 1030 receives power from the rectification unit 1020 and performs operations such as packet generation and transmission and wireless power transmission control in each phase. 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 that 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 packets are transmitted through techniques such as RFID (radio frequency identification), Bluetooth, or NFC (near field communication). This can be transmitted.

In the ID identification and configuration phase, the control unit 1030 generates an identification packet indicating a unique ID of the wireless power receiver 1000 and configuration information of the wireless power receiver 1000, and generates the identification packet and configuration information. Transmitted to a wireless power transmission 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 after completing the ID identification and configuration phase and before the power transmission phase of receiving wireless power. Alternatively, the initial voltage V _i may be defined as the voltage of the output terminal in a standby state before wireless charging begins.

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

In the power transmission phase, the control unit 1030 may 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 packets required for wireless power transmission control.

All of the above-described functions can be performed by a processor such as a microprocessor, controller, microcontroller, application specific integrated circuit (ASIC), etc. according to software or program code coded to perform the above functions. The design, development and implementation of the above 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 above with reference to examples, those skilled in the art can make various modifications and changes to the present invention without departing from the technical spirit and scope of the present invention. You will understand. Therefore, without being limited to the above-described embodiments, the present invention will include all embodiments within the scope of the following claims.

Claims (13)

In a method of detecting foreign substances in a wireless power receiving device,
Performing a foreign matter detection operation during charging using two-way communication; and
If no foreign matter is detected in the foreign matter detection operation during charging, detecting fine foreign matter using a temperature sensor to limit power.
Including,
The step of performing a foreign matter detection operation during charging using the two-way communication is,
Receiving a transmission power measurement report indicating the measured transmission power from a wireless power transmission device that generates an induced magnetic field or resonance by applying power to the primary coil in a charging mode;
detecting a foreign substance based on the difference between the measured transmission power and the measured reception power; and
Transmitting an ASK signal including the foreign substance detection result to the wireless power transmitter
Method, including. delete delete The method of claim 1, wherein the transmission power measurement report is transmitted as an FSK signal transmitted using the FSK method,
The FSK signal includes the amount of transmission power measured by measuring the power generated by the primary coil according to the AC signal. According to claim 4,
The FSK signal is transmitted repeatedly at predetermined periods,
The method is characterized in that the predetermined period is a section in which a predetermined number of data signals are transmitted. According to claim 4,
The FSK signal is a signal that transmits 0 or 1 by switching or selecting a variable frequency in a certain range that converts the required fixed power frequency. According to claim 1,
The ASK signal includes required power information, which is information requesting that the wireless power transmitter generate wireless power based on a magnetic induction method. A wireless power receiving device that detects foreign substances,
A secondary core block that receives wireless power from the wireless power transmission device by combining with the primary core block provided in the wireless power transmission device through magnetic induction or magnetic resonance;
a rectification unit connected to the secondary core block and providing power to a control unit and an external load by performing full-wave rectification on the AC waveform generated in the secondary core block; and
A control unit that measures the voltage of the output terminal connected to the external load and, if the voltage is within the reference voltage range, controls the wireless power receiver to enter the foreign matter detection phase.
Including,
The control unit performs a foreign matter detection operation during charging using two-way communication, and if no foreign matter is detected in the foreign matter detection operation during charging, detects fine foreign matter using a temperature sensor to limit power,
The control unit receives a transmission power measurement report indicating the measured transmission power from the wireless power transmission device that generates an induced magnetic field or resonance by applying power to the primary coil in charging mode, and Detects foreign matter based on the difference between the received power and the measured received power, controls to transmit an ASK signal including the foreign matter detection result to the wireless power transmitter, and performs a foreign matter detection operation during charging using the two-way communication. A wireless power receiving device. delete The method of claim 8, wherein the transmission power measurement report is transmitted as an FSK signal transmitted using the FSK method,
The FSK signal includes a transmission power amount measured by measuring the power generated by the primary coil according to the AC signal. According to claim 10,
The FSK signal is transmitted repeatedly at predetermined periods,
A wireless power receiving device, characterized in that the predetermined period is a section in which a predetermined number of data signals are transmitted. According to claim 10,
The FSK signal is a wireless power receiving device characterized in that it is a signal that transmits 0 or 1 by switching or selecting a variable frequency in a certain range that converts the required fixed power frequency. According to claim 8,
The ASK signal includes required power information, which is information requesting the wireless power transmission device to generate wireless power based on magnetic induction.