Wireless power transmission apparatus and method and wireless power reception apparatus

A wireless power transmission apparatus includes a measurer configured to measure a value of a current flowing in a source resonator, a communication unit configured to receive a value of a charging current of a battery from a wireless power reception apparatus, and a power controller configured to control an amount of power to be transmitted by the source resonator based on either one or both of the value of the current measured by the measurer and the value of the charging current received by the communication unit. The value of the charging current of the battery varies as the battery is charged.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 USC 119(a) of Korean Patent Application No. 10-2012-0100867 filed on Sep. 12, 2012, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes.

BACKGROUND

The following description relates to an apparatus and method for transmitting power wirelessly, and an apparatus for receiving power wirelessly.

2. Description of Related Art

Research on wireless power transmission has been conducted to overcome an increase in the inconvenience of wired power supplies and the limited capacity of conventional batteries due to a rapid increase in various electronic devices including electric vehicles, mobile devices, and the like. One wireless power transmission technology uses resonance characteristics of radio-frequency (RF) devices. A wireless power transmission system using resonance characteristics may include a source configured to supply power, and a target configured to receive the supplied power.

SUMMARY

In one general aspect, a wireless power transmission apparatus includes a measurer configured to measure a value of a current flowing in a source resonator; a communication unit configured to receive a value of a charging current of a battery from a wireless power reception apparatus; and a power controller configured to control an amount of power to be transmitted by the source resonator based on either one or both of the value of the current measured by the measurer and the value of the charging current received by the communication unit; wherein the value of the charging current of the battery varies as the battery is charged.

The power controller may include a charging mode determiner configured to determine a charging mode of the battery based on a change in the value of the charging current received by the communication unit; and a pulse signal generator configured to generate a pulse signal having a pulse width adjusted based on the determined charging mode of the battery.

The charging mode determiner may be further configured to determine whether the charging mode of the battery is a constant current (CC) mode in which the value of the charging current of the battery is constant, or a constant voltage (CV) mode in which the value of the charging current of the battery is variable and a value of a charging voltage of the battery is constant.

The apparatus may further include an alternating current-to-direct current (AC/DC) converter configured to convert an AC power supplied from a power supply to a DC power based on the pulse width of the pulse signal; and a DC-to-AC (DC/AC) converter configured to convert the DC power to an AC power based on a resonant frequency of the source resonator.

The communication unit may be further configured to receive, from the wireless power reception apparatus, a value of a current flowing in a target resonator; and the power controller may include an offset calculator configured to calculate a power transmission efficiency offset by comparing the value of the current measured by the measurer with the value of the current flowing in the target resonator received by the communication unit, and calculating the power transmission efficiency offset based on a result of the comparing; and a pulse signal generator configured to generate a pulse signal having a pulse width adjusted based on the calculated power transmission efficiency offset.

The communication unit may be further configured to receive, from the wireless power reception apparatus, a value of a current flowing in a target resonator; and the power controller may include a charging mode determiner configured to determine a charging mode of the battery based on a change in the value of the charging current received by the communication unit; an offset calculator configured to calculate a power transmission efficiency offset by comparing the value of the current measured by the measurer with the value of the current flowing in the target resonator received by the communication unit, and calculating the power transmission efficiency offset based on a result of the comparing; and a pulse signal generator configured to generate a pulse signal having a pulse width adjusted based on the determined charging mode of the battery and the calculated power transmission efficiency offset.

The apparatus may further include a first comparator configured to compare the value of the current measured by the measurer with a reference current value; and a second comparator configured to compare the value of the current flowing in the target resonator received by the communication unit with the reference current value; wherein the pulse signal generator may be further configured to adjust the pulse width of the pulse signal based on a difference between a result of the comparing by the first comparator and a result of the comparing by the second comparator.

The communication unit may be further configured to receive, from the wireless power reception apparatus, a value of a current flowing in a rectifier as the value of the charging current of the battery.

The wireless power reception apparatus may be configured to receive power from a target resonator; the source resonator may include a coil; the target resonator may include a coil; and a ratio of a number of turns of the coil of the source resonator to a number of turns of the coil of the target resonator is a 1:1 ratio.

In another general aspect, a wireless power reception apparatus includes a rectifier configured to rectify an alternating current (AC) power received from a wireless power transmission apparatus by a target resonator through a mutual resonance with a source resonator to a direct current (DC) power; a measurer configured to measure a value of a current flowing in the target resonator; and a communication unit configured to transmit the value of the current measured by the measurer to the wireless power transmission apparatus.

The measurer may be further configured to measure a value of a current flowing from the rectifier into a battery; and the communication unit may be further configured to transmit the value of the current flowing into the battery to the wireless power transmission apparatus.

The apparatus may further include a controller configured to determine a charging mode of the battery based on a change in the value of the current flowing into the battery.

The communication unit may be further configured to communicate with the wireless power transmission apparatus using either one or both of an in-band communication scheme using a resonant frequency of the target resonator and an out-band communication scheme using a communication frequency differing from the resonant frequency.

In another general aspect, a wireless power transmission method includes measuring a value of a current flowing in a source resonator; receiving a value of a charging current of a battery from a wireless power reception apparatus; and controlling an amount of power to be transmitted by the source resonator based on either one or both of the measured value of the current and the received value of the charging current; wherein the value of the charging current of the battery varies as the battery is charged.

The controlling may include determining a charging mode of the battery based on a change in the received value of the charging current; and generating a pulse signal having a pulse width adjusted based on the determined charging mode of the battery.

The method may further include converting an alternating current (AC) power supplied from a power supply to a direct current (DC) power based on the pulse width of the pulse signal; and converting the DC power to an AC power based on a resonant frequency of the source resonator.

The receiving may include receiving, from the wireless power reception apparatus, a value of a current flowing in a target resonator; and the controlling may include calculating a power transmission efficiency offset by comparing the measured value of the current with the received value of the current flowing in the target resonator, and calculating the power transmission efficiency offset based on a result of the comparing; and generating a pulse signal having a pulse width adjusted based on the calculated power transmission efficiency offset.

The receiving may include receiving, from the wireless power reception apparatus, a value of a current flowing in a target resonator; and the controlling may include determining a charging mode of the battery based on a change in the received value of the charging current; calculating a power transmission efficiency offset by comparing the measured value of the current with the received value of the current flowing in the target resonator, and calculating the power transmission efficiency offset based on a result of the comparing; and generating a pulse signal having a pulse width adjusted based on the determined charging mode of the battery and the calculated power transmission efficiency offset.

In another general aspect, a wireless power transmission apparatus includes a measurer configured to measure information indicative of an amount of power being transmitted by a source resonator; a communication unit configured to receive, from a wireless power reception apparatus, measured information indicative of an amount of power being consumed by a load powered by the wireless reception apparatus; and a controller configured to control an amount of power to be transmitted by the source resonator based on either one or both of the information measured by the measurer and the measured information received by the communication unit.

The controller may be further configured to control the amount of power to be transmitted by the source resonator based on a difference between the information measured by the measurer and the measured information received by the communication unit.

DETAILED DESCRIPTION

Communication between a source and a target may be performed using either one or both of an in-band communication scheme and an out-band communication scheme. The in-band communication scheme refers to communication performed between the source and the target in the same frequency band used for power transmission. The out-band communication scheme refers to communication performed between the source and the target in a separate frequency band different from the frequency band used for power transmission.

FIG. 1is a diagram illustrating an example of a wireless power transmission system. Referring toFIG. 1, the wireless power transmission system includes a source110and a target120. The source110is a device configured to supply wireless power, and may be any electronic device capable of supplying power, for example, a pad, a terminal, a television (TV), a medical device, or an electric vehicle. The target120is a device configured to receive supplied wireless power, and may be any electronic device requiring power, for example, a pad, a terminal, a tablet personal computer (PC), a medical device, or an electric vehicle.

The source110includes a variable switching mode power supply (SMPS)111, a power amplifier (PA)112, a matching network113, a transmission (TX) controller114(for example, TX control logic), a communication unit115, and a power detector116.

The variable SMPS111generates a direct current (DC) voltage by switching an alternating current (AC) voltage having a frequency in a band of tens of hertz (Hz) output from a power supply. The variable SMPS111may output a DC voltage having a predetermined level, or may output a DC voltage having a level that may be adjusted under control of the TX controller114.

The variable SMPS111may control its output voltage based on a level of power output from the PA112so that the PA112may operate in a saturation region with high efficiency at all times, and may enable a maximum efficiency to be maintained at all levels of the output power of the PA112. The PA112may have, for example, class-E features.

For example, if a fixed SMPS is used instead of the variable SMPS111, a variable DC-to-DC (DC/DC) converter needs to be provided. In this example, the fixed SMPS outputs a fixed voltage to the variable DC/DC converter, and the variable DC/DC converter controls its output voltage based on the level of the power output from the PA112so that the PA112may operate in the saturation region with high efficiency at all times, and may enable the maximum efficiency to be maintained at all levels of the output power of the PA112.

The power detector116detects an output current and an output voltage of the variable SMPS111, and provides information on the detected current and the detected voltage to the TX controller114. Additionally, the power detector116may detect an input current and an input voltage of the PA112.

The PA112generates power by converting DC voltage having a predetermined level to an AC voltage using a switching pulse signal having a frequency in a band of a few megahertz (MHz) to tens of MHz output from a signal generator. Accordingly, the PA112may convert the DC voltage supplied to the PA112by the variable SMPS111to an AC voltage having a reference resonant frequency FRef, and may generate communication power used for communication, or charging power used for charging. The communication power and the charging power may be used in a plurality of targets.

The communication power may be a low power of 0.1 milliwatt (mW) to 1 mW. The charging power may be a high power of 1 mW to 200 watt (W) that is consumed by a device load of a target. In various examples described herein, the term “charging” may refer to supplying power to a unit or element that is configured to charge a battery or other rechargeable device. Additionally, the term “charging” may refer to supplying power to a unit or element that is configured to consume power. The units or elements may include, for example, batteries, displays, sound output circuits, main processors, and various sensors.

Also, the term “reference resonant frequency” refers to a resonant frequency that is used by the source110. Additionally, the term “tracking frequency” refers to a resonant frequency that is adjusted according to a preset scheme.

The TX controller114may detect a reflected wave of the communication power or the charging power, and may detect mismatching that may occur between a target resonator133and the source resonator131based on the detected reflected wave. To detect the mismatching, for example, the TX controller114may detect an envelope of the reflected wave, a power amount of the reflected wave, or any other characteristic of the reflected wave that is affected by mismatching.

The matching network113compensates for impedance mismatching between the source resonator131and the target resonator133to achieve optimal matching under the control of the TX controller114. The matching network113includes at least one capacitor and at least one inductor each connected to a switch controlled by the TX controller114.

The TX controller114may calculate a voltage standing wave ratio (VSWR) based on a voltage level of the reflected wave and a level of an output voltage of the source resonator131or the PA112. In one example, if the VSWR is greater than a predetermined value, the TX controller114may determine that mismatching is detected.

In another example, if the VSWR is greater than the predetermined value, the TX controller114may calculate a power transmission efficiency for each of N tracking frequencies, determine a tracking frequency FBesthaving the best power transmission efficiency among the N tracking frequencies, and adjust the reference resonant frequency FRefto the tracking frequency FBest. The N tracking frequencies may be set in advance.

The TX controller114may adjust a frequency of the switching pulse signal used by the PA112. Under the control of the TX controller114, the frequency of the switching pulse signal may be determined. For example, by controlling the PA112, the TX controller114may generate a modulation signal to be transmitted to the target120. In other words, the TX controller114may transmit a variety of data to the target120using in-band communication. The TX controller114may detect a reflected wave, and may demodulate a signal received from the target120from an envelope of the detected reflected wave.

The TX controller114may generate a modulated signal for in-band communication using various methods. For example, the TX controller114may generate the modulation signal by turning on or off the switching pulse signal used by the PA112, by performing delta-sigma modulation, or by any other modulation method known to one of ordinary skill in the art. Additionally, the TX controller114may generate a pulse-width modulation (PWM) signal having a predetermined envelope.

The TX controller114may determine an initial wireless power that is to be transmitted to the target120based on a change in a temperature of the source110, a battery state of the target120, a change in an amount of power received at the target120, and/or a change in a temperature of the target120.

The source110may further include a temperature measurement sensor (not illustrated) configured to detect a change in temperature of the source110. The source110may receive from the target120information regarding the battery state of the target120, the change in the amount of power received at the target120, and/or the change in the temperature of the target120via communication with the target120. The source110may detect the change in the temperature of the target120based on the information received from the target120.

The TX controller114may adjust a voltage supplied to the PA112using a lookup table. The lookup table may be used to store a level of the voltage to be supplied to the PA112based on the change in the temperature of the source110. For example, when the temperature of the source110rises, the TX controller114may lower the level of the voltage to be supplied to the PA112by controlling the variable SMPS111.

The communication unit115performs out-band communication using a separate communication channel. The communication unit115may include a communication module, such as a ZigBee module, a Bluetooth module, or any other communication module known to one of ordinary skill in the art that the communication unit115may use to transmit data140to the target120via the out-band communication.

The source resonator131transfers electromagnetic energy130to the target resonator133. For example, the source resonator131may transfer the communication power or the charging power to the target120via magnetic coupling with the target resonator133.

As illustrated inFIG. 1, the target120includes a matching network121, a rectifier122, a DC/DC converter123, a communication unit124, a reception (RX) controller125(for example, RX control logic), a voltage detector126, and a power detector127.

The target resonator133receives the electromagnetic energy130from the source resonator131. For example, the target resonator133may receive the communication power or the charging power from the source110via the magnetic coupling with the source resonator131. Additionally, the target resonator133may receive data from the source110via the in-band communication.

The target resonator133may receive the initial wireless power that is determined by the TX controller114based on the change in the temperature of the source110, the battery state of the target120, the change in the amount of power received at the target120, and/or the change in the temperature of the target120.

The matching network121matches an input impedance viewed from the source110to an output impedance viewed from a load of the target120. The matching network121may be configured to have at least capacitor and at least one inductor.

The rectifier122generates a DC voltage by rectifying an AC voltage received from the target resonator133.

The DC/DC converter123may adjust a level of the DC voltage output from the rectifier122based on a capacity required by the load. For example, the DC/DC converter123may adjust the level of the DC voltage output from the rectifier122to a level in a range from 3 volts (V) to 10 V.

The voltage detector126detects a voltage of an input terminal of the DC/DC converter123, and the power detector127detects a current and a voltage of an output terminal of the DC/DC converter123. The detected voltage of the input terminal may be used to calculate a power transmission efficiency of power received from the source110. The detected current and the detected voltage of the output terminal may be used by the RX controller125to calculate an amount of power actually transferred to the load. The TX controller114of the source110may calculate an amount of power that needs to be transmitted by the source110to the target120based on a power required by the load and the power actually transferred to the load.

If the amount of power actually transferred to the load calculated by the RX controller125is transmitted to the source110by the communication unit124, the source110may calculate the amount of power that needs to be transmitted to the target120.

The RX controller125may perform in-band communication to transmit or receive data using a resonant frequency. During the in-band communication, the RX controller125may demodulate a received signal by detecting a signal between the target resonator133and the rectifier122, or detecting an output signal of the rectifier122, and demodulating the detected signal. In other words, the RX controller125may demodulate a message received via the in-band communication. Additionally, the RX controller125may adjust an impedance of the target resonator133using the matching network121to modulate a signal to be transmitted to the source110. For example, the RX controller125may adjust the matching unit121to increase the impedance of the target resonator133so that a reflected wave may be detected by the TX controller114of the source110. Depending on whether the reflected wave is detected, the TX controller114may detect a first value, for example, a binary number “0,” or a second value, for example, a binary number “1.” For example, when the reflected wave is detected, the TX controller114may detect “0”, and when the reflected wave is not detected, the TX controller114may detect “1”. Alternatively, when the reflected wave is detected, the TX controller114may detect “1”, and when the reflected wave is not detected, the TX controller114may detect “0”.

The communication unit124may transmit a response message to the communication unit115of the source110. For example, the response message may include any one or any combination of a “type of a corresponding target,” “information about a manufacturer of a corresponding target,” “a model name of a corresponding target,” a “battery type of a corresponding target,” a “scheme of charging a corresponding target,” an “impedance value of a load of a corresponding target,” “information on characteristics of a target resonator of a corresponding target,” “information on a frequency band used by a corresponding target,” an “amount of a power consumed by a corresponding target,” an “identifier (ID) of a corresponding target,” “information on a version or a standard of a corresponding target,” and any other information about the target120.

The communication unit124performs out-band communication that employs a separate communication channel. For example, the communication unit124may include a communication module, such as a ZigBee module, a Bluetooth module, or any other communication module known to one of ordinary skill in the art that the communication unit124may use to transmit or receive the data140to or from the source110via the out-band communication.

The communication unit124may receive a wake-up request message from the source110, and the power detector127may detect an amount of power received by the target resonator133. The communication unit124may transmit to the source110information on the detected amount of the power. Information on the detected amount of the power may include, for example, an input voltage value and an input current value of the rectifier122, an output voltage value and an output current value of the rectifier122, an output voltage value and an output current value of the DC/DC converter123, and any other information about the detected amount of the power.

FIG. 2is a block diagram illustrating an example of a wireless power transmission apparatus. Referring toFIG. 2, the wireless power transmission apparatus includes a power supply210, an AC/DC converter220, a DC/AC converter230, a source resonator240, a measurer250, a communication unit260, and a power controller270.

The AC/DC converter220converts an AC power supplied from the power supply210to a DC power based on a pulse width of a pulse signal generated by the power controller270.

The DC/AC converter230converts the DC power converted by the AC/DC converter220to an AC power based on a resonant frequency of the source resonator240. The DC/AC converter230may amplify the AC power. An amount of the AC power to be amplified may be determined based on an amount of power to be transmitted by the wireless power transmission apparatus.

The source resonator240transmits the AC power output from the DC/AC converter230via a mutual resonance. In this example, the mutual resonance may occur between the source resonator240and a target resonator of a wireless power reception apparatus (not shown inFIG. 2, but see the target resonator510of the wireless power reception apparatus inFIG. 5). When a resonant frequency band of the source resonator240matches a resonant frequency band of the target resonator, a mutual resonance may occur between the source resonator240and the target resonator.

The measurer250measures a value of a current flowing in the source resonator240. The AC power generated by the DC/AC converter230is transferred to the source resonator240. The value of the current measured by the measurer250may be compared with an expected amount of power to be controlled by the power controller270. In addition, a result in which efficiencies of the AC/DC converter220and the DC/AC converter230are reflected may be reflected in the measured value of the current.

The communication unit260receives a value of a charging current of a battery from the wireless power reception apparatus. In this example, the value of the charging current of the battery varies as the battery of the wireless power reception apparatus is charged. The battery of the wireless power reception apparatus may be charged using power transmitted by the source resonator240. As the battery is charged, a value of load of the battery may increase. When the value of load of the battery increases, a value of a charging current used to charge the battery may be changed. The communication unit260may receive the varying value of the charging current from the wireless power reception apparatus.

The communication unit260may communicate with the wireless power reception apparatus using either one or both of an in-band communication scheme using a resonant frequency of the source resonator240and an out-band communication scheme using a communication frequency differing from the resonant frequency of the source resonator240.

The power controller270controls an amount of power to be transmitted by the source resonator240based on either one or both of the value of the current measured by the measurer250and the value of the charging current received by the communication unit260.

The value of the charging current received by the communication unit260may be used for determining a charging mode of the battery. In addition, a value of a current flowing in the target resonator received by the communication unit260may be compared with the value of the current measured by the measurer250, and used for calculating a power transmission efficiency offset or a power transmission efficiency.

The value of the current measured by the measurer250may be used as a reference value for calculating the power transmission efficiency. In addition, the value of the current measured by the measurer250may be used for calculating the power transmission efficiency offset and an internal efficiency of a process of generating an AC power performed by the AC/DC converter220, the DC/AC converter230, and the power controller270.

For example, the power controller270may control an amount of power so that a current of 10 amperes (A) is supposed to flow in the source resonator240. When an actual current passing through the AC/DC converter220and the DC/AC converter230and flowing in the source resonator240is 9 A, an internal efficiency may be 90% and power transmission efficiency offset may be 1 A. The power controller270may control the amount of power to be transmitted by the source resonator240based on the internal efficiency and the power transmission efficiency offset.

The power controller270includes a charging mode determiner271and a pulse signal generator273.

The charging mode determiner271determines a charging mode of the battery based on a change in the value of the charging current received by the communication unit260. The charging mode of the battery may be a constant current (CC) mode in which the value of the charging current of the battery is constant, or a constant voltage (CV) mode in which the value of the charging current of the battery is variable and a value of a charging voltage of the battery is constant.

The pulse signal generator273generates a pulse signal having a pulse width adjusted based on the determined charging mode of the battery. For example, the pulse signal generator273may adjust the pulse width of the pulse signal by performing pulse width modulation (PWM). For example, the pulse signal generator273may increase a pulse width of a pulse signal in a single cycle when the charging mode of the battery is determined to be the CC mode, thereby enabling a relatively large amount of power to be transferred by the source resonator240in the CC mode. In addition, the pulse signal generator273may decrease a pulse width of a pulse signal in a single cycle when the charging mode of the battery is determined to be the CV mode, thereby enabling a relatively small amount of power compared to the amount of power transferred in the CC mode to be transferred by the source resonator240in the CV mode.

The communication unit260may receive from the wireless power reception apparatus a value of a current flowing in the target resonator of the wireless power reception apparatus. The value of the current flowing in the target resonator may be used for calculating a power transmission efficiency of power to be transferred by the source resonator240.

The communication unit260may receive from the wireless power reception apparatus a value of a current flowing in a rectifier (not shown inFIG. 2, but see the rectifier520inFIG. 5) of the wireless power reception apparatus. The value of the current flowing in the rectifier may be used for determining the charging mode of the battery.

The source resonator240and the target resonator may be resonators provided in a form of a coil. A ratio of a number of turns of the coil of the source resonator240to a number of turns of the coil of the target resonator may be a 1:1 ratio. In particular, the coils may be wound so that the ratio of the number of the turns of the coil of the source resonator240to the number of the turns of the coil of the target resonator is the 1:1 ratio.

A power transmission efficiency when the number of the turns of the coil of the source resonator240is the same as the number of the turns of the coil of the target resonator is higher than a power transmission efficiency when the number of the turns of the coil of the source resonator240is not the same as the number of the turns of the coil of the target resonator.

FIG. 3is a block diagram illustrating an example of a power controller310in a wireless power transmission apparatus. Referring toFIG. 3, the power controller310includes an offset calculator311and a pulse signal generator313.

In contrast to the power controller270ofFIG. 2, the power controller310includes the offset calculator311instead of the charging mode determiner271. The rest of the power controller310is identical to the power controller270ofFIG. 2. The operation of the power controller310will be described by referring to various elements shown inFIG. 2.

The offset calculator311calculates a power transmission efficiency offset by comparing the value of the current measured by the measurer250with the value of the current flowing in the target resonator received by the communication unit260, and calculating the power transmission efficiency offset based on a result of the comparing. The value of the current measured by the measurer250may be a value of a current flowing in the source resonator240. The communication unit260receives the value of the current flowing in the target resonator. Accordingly, the power transmission efficiency offset may be calculated. In particular, the power transmission efficiency offset may be calculated based on a difference between the value of the current flowing in the source resonator240and the value of the current flowing in the target resonator.

The pulse signal generator313generates a pulse signal having a pulse width adjusted based on the calculated power transmission efficiency offset. In theory, the entire amount of power transmitted by the source resonator240may be transferred to the target resonator. However, in view of an environment in which the power is transmitted, a number of factors may cause a loss of power. Accordingly, an amount of power to be transmitted by the source resonator240may be adjusted in view of an actual amount of power that is transferred to the target resonator.

For example, when a power transmission efficiency offset is relatively great, indicating a relatively great loss of power, the pulse signal generator313may generate a pulse signal having a pulse width that is relatively wide in a single cycle. Conversely, when a power transmission efficiency offset is relatively small, indicating a relatively small loss of power, the pulse signal generator313may generate a pulse signal having a pulse width that is relatively narrow in a single cycle.

FIG. 4is a block diagram illustrating another example of a wireless power transmission apparatus. Referring toFIG. 4, the wireless power transmission apparatus includes a power supply410, an AC/DC converter420, a DC/AC converter430, a source resonator440, a measurer450, a communication unit460, a first comparator470, a second comparator480, and a power controller490.

The AC/DC converter420converts an AC power supplied from the power supply410to a DC power based on a pulse width of a pulse signal generated by the power controller490.

The DC/AC converter430converts the DC power converted by the AC/DC converter420to an AC power based on a resonant frequency of the source resonator440. The DC/AC converter430may amplify the AC power. An amount of the AC power to be amplified may be determined based on an amount of power to be transmitted by the wireless power transmission apparatus.

The source resonator440transmits the AC power output from the DC/AC converter430via a mutual resonance. In this example, the mutual resonance may occur between the source resonator440and a target resonator of a wireless power reception apparatus (not shown inFIG. 2, but see the target resonator510of the wireless power reception apparatus inFIG. 5). When a resonant frequency band of the source resonator440matches a resonant frequency band of the target resonator, a mutual resonance may occur between the source resonator440and the target resonator.

The measurer450measures a value of a current flowing in the source resonator440. The AC power generated by the DC/AC converter430is transferred to the source resonator440. The value of the current measured by the measurer450may be compared with an expected amount of power to be controlled by the power controller490. In addition, a result in which efficiencies of the AC/DC converter420and the DC/AC converter430are reflected may be reflected in the measured value of the current.

The communication unit460receives a value of a charging current of a battery from the wireless power reception apparatus. In this example, the value of the charging current of the battery varies as the battery of the wireless power reception apparatus is charged. The battery of the wireless power reception apparatus may be charged using power transmitted by the source resonator440. As the battery is charged, a value of load of the battery may increase. When the value of load of the battery increases, a value of a charging current used to charge the battery may be changed. The communication unit460may receive the varying value of the charging current from the wireless power reception apparatus.

The communication unit460may communicate with the wireless power reception apparatus using either one or both of an in-band communication scheme using a resonant frequency of the source resonator440and an out-band communication scheme using a communication frequency differing from the resonant frequency of the source resonator440.

The communication unit460may receive from the wireless power reception apparatus a value of a current flowing in the target resonator of the wireless power reception apparatus. The value of the current flowing in the target resonator may be used for calculating a power transmission efficiency of power to be transferred by the source resonator440.

The first comparator470compares the value of the current measured by the measurer450with a reference current value Iref401. The reference current value Iref401may be set to a value of a current corresponding to an amount of power to be transmitted by the power controller490via the source resonator440. The first comparator470transfers to the power controller490a difference between the value of the current measured by the measurer450and the reference current value Iref401. The first comparator470may also transfer to the power controller490information indicating which one of the value of the current measured by the measurer450and the reference current value Iref401has a greater value. For example, the first comparator470may output a bit “1” when the current measured by the measurer450has a greater value than the reference current value Iref401, and output a bit “0” when the reference current value Iref401has greater value than the current measured by the measurer450.

The second comparator480compares the value of the current flowing in the target resonator received by the communication unit460with the reference current value Iref401. The second comparator480transfers to the power controller490a difference between the value of the current flowing in the target resonator received by the communication unit460and the reference current value Iref401. The second comparator480may also transfer to the power controller490information indicating which one of the value of the current flowing in the target resonator received by the communication unit460and the reference current value Iref401has a greater value. For example, the second comparator480may output a bit “1” when the current flowing in the target resonator received by the communication unit460has a greater value than the reference current value Iref401, and output a bit “0” when the reference current value Iref401has greater than the current flowing in the target resonator received by the communication unit460.

The power controller490controls an amount of power to be transmitted by the source resonator440based on either one or both of the value of the current received by the communication unit460and the value of the current measured by the measurer450.

The power controller490includes a charging mode determiner491, an offset calculator493, and a pulse signal generator495.

The charging mode determiner491determines a charging mode of the battery based on a change in the value of the charging current received by the communication unit460. The charging mode of the battery may be a CC mode in which the value of the charging current of the battery is constant, or a CV mode in which the value of the charging current of the battery is variable and a value of a charging voltage of the battery is constant.

The offset calculator493calculates a power transmission efficiency offset by comparing the value of the current measured by the measurer450with the value of the current flowing in the target resonator received by the communication unit460, and calculating the power transmission efficiency offset based on a result of the comparing. For example, when the value of the current measured by the measurer450is 10 A and the value of the current flowing in the target resonator is 9 A, the power transmission efficiency offset may be calculated as 1 A by the offset calculator493.

The pulse signal generator495generates a pulse signal having a pulse width adjusted based on the determined charging mode of the battery and the calculated power transmission efficiency offset. The pulse signal generator495may adjust a pulse width, for example, by performing PWM. For example, the pulse signal generator495may increase a pulse width of a pulse signal in a single cycle based on the power transmission efficiency offset when the charging mode of the battery is determined to be the CC mode, thereby enabling a relatively large amount of power to be transferred by the source resonator440in the CC mode. As another example, the pulse signal generator495may decrease a pulse width of a pulse signal in a single cycle based on the power transmission efficiency offset when the charging mode of the battery is determined to be the CV mode, thereby enabling a relatively small amount of power compared to the amount of power transferred in the CC mode to be transferred by the source resonator440in the CV mode. In this example, the pulse signal generator495may flexibly adjust the pulse width based on the power transmission efficiency offset.

The pulse signal generator495may adjust the pulse width of the pulse signal based on a difference between a result of the comparing by the first comparator470and a result of the comparing by the second comparator480. The result of the comparing by the first comparator470indicates an internal efficiency in a process of transmitting power through the source resonator440in the wireless power transmission apparatus. The result of the comparing by the second comparator480indicates a power transmission efficiency offset or a power transmission efficiency. The pulse signal generator495may adjust the pulse width of the pulse signal based on the internal efficiency and the power transmission efficiency. For example, when the internal efficiency is 90% and the power transmission efficiency is 80%, this indicates that only 72% of the power output from the AC/DC converter420actually reaches the target resonator. Accordingly, the pulse signal generator495may adjust the pulse width so that a desired amount of power may be transferred to the source resonator440and the target resonator.

The source resonator440and the target resonator may be resonators provided in a form of a coil. A number of turns of the coil of the source resonator440may be equal to a number of turns of the coil of the target resonator based so that a turns ratio of the number of turns of the coil of the source resonator440to the number of turns of the coil of the target resonator is a 1:1 ratio. In particular, the coils may be wound so that the 1:1 ratio of the number of the turns of the coil of the source resonator240to the number of the turns of the coil of the target resonator may be achieved.

A power transmission efficiency when the number of the turns of the coil of the source resonator440is equal to the number of the turns of the coil of the target resonator is higher than a power transmission efficiency when the number of the turns of the coil of the source resonator440is not equal to the number of the turns of the coil of the target resonator.

FIG. 5is a block diagram illustrating an example of a wireless power reception apparatus. Referring toFIG. 5, the wireless power reception apparatus includes a target resonator510, a rectifier520, a battery530, a measurer540, a communication unit550, and a controller560.

The target resonator510receives power wirelessly via a mutual resonance with a source resonator of a wireless power transmission apparatus (not shown inFIG. 5, but see the source resonator240inFIG. 2and the source resonator440inFIG. 4). In particular, a current is induced in the target resonator510by the received wireless power due to the mutual resonance.

The rectifier520rectifies an AC power received by the source resonator510to a DC power.

The battery530stores the DC power rectified by the rectifier520. That is, the battery530may be charged using the DC power.

The measurer540measures a value of a current flowing in the target resonator510.

The communication unit550transmits the value of the current measured by the measurer540to the wireless power transmission apparatus. The value of the current measured by the measurer540may be used for calculating a power transmission efficiency or a power transmission efficiency offset by the wireless power transmission apparatus.

The measurer540may measure a value of a current flowing from the rectifier520into the battery530, and the communication unit550may transmit to the wireless power transmission apparatus the value of the current flowing into the battery530. The value of the current flowing from the rectifier520into the battery530may be used for determining a charging mode of the battery530by the wireless power transmission apparatus.

The communication unit550communicates with the wireless power transmission apparatus using either one or both of an in-band communication scheme using a resonant frequency of the target resonator510and an out-band communication scheme using a communication frequency differing from the resonant frequency.

The controller560may determine the charging mode of the battery530based on a change in the value of the current flowing into the battery530. The charging mode of the battery530may be a CC mode in which the value of a charging current of the battery530is constant, and a CV mode in which the value of the charging current of the battery530is variable and a value of a charging voltage of the battery530is constant. The communication unit550may transmit information on the determined charging mode to the wireless power transmission apparatus.

FIG. 6is a block diagram illustrating another example of a wireless power transmission system600. Referring toFIG. 6, the wireless power transmission system600includes a wireless power transmission apparatus610and a wireless power reception apparatus620.

The wireless power transmission apparatus610includes a power supply unit611, an AC/DC converter612, a DC/AC converter613, a source resonator614, a measurer615, a communication unit616, a first comparator617, a second comparator618, and a power controller619.

The power supply unit611provides a three-phase AC power. The AC/DC converter612converts the AC power supplied by the power supply unit611to a DC power. The AC/DC converter612receives a pulse signal having a modulated pulse width from the power controller619, and converts the AC power to the DC power based on the pulse width of the received signal. An amplitude of the DC power may increase or decrease based on the pulse width.

The DC/AC converter613converts the DC power to an AC power in a resonant frequency band of the source resonator614. The DC/AC converter613may be implemented as an inverter. The source resonator614transfers the AC power to a target resonator621via a mutual resonance with the target resonator621.

The measurer615measures a value of a current flowing in the source resonator614. The communication unit616receives from a communication unit624information on a value of a current flowing in the target resonator621measured by a measurer623.

The first comparator617compares the value of the current measured by the measurer615with a reference current value Iref. The reference current value Irefmay be set to a value of a current corresponding to an amount of power to be transmitted by the power controller619via the source resonator614. The first comparator617may transfer to the power controller619a difference between the value of the current measured by the measurer615and the reference current value Iref. The first comparator617may also transfer to the power controller619information indicating which one of the value of the current measured by the measurer615and the reference current value Irefhas a greater value. For example, the first comparator617may output a bit “1” when the current measured by the measurer615is has a greater value than the reference current value Iref, and output a bit “0” when the reference current value Irefhas greater value than the current measured by the measurer615.

The second comparator618compares the value of the current flowing in the target resonator621received by the communication unit616with the reference current value Iref. The second comparator618transfers to the power controller619a difference between the value of the current flowing in the target resonator621received by the communication unit616and the reference current value Iref. The second comparator618may also transfer to the power controller619information indicating which one of the value of the current flowing in the target resonator621received by the communication unit616and the reference current value Irefhas a greater value. For example, the second comparator618may output a bit “1” when the current flowing in the target resonator621received by the communication unit616has a greater value than the reference current value Iref, and output a bit “0” when the reference current value Irefhas a greater value than the current flowing in the target resonator621received by the communication unit616.

The power controller619may adjust a pulse width of a pulse signal based on a difference between a result of the comparing by the first comparator617and a result of the comparing by the second comparator618. The result of the comparing by the first comparator617indicates an internal efficiency in a process of transmitting power via the source resonator614in the wireless power transmission apparatus610. The result of the comparing by the second comparator618indicates a power transmission efficiency offset or a power transmission efficiency. The power controller619may adjust the pulse width of the pulse signal based on the internal efficiency and the power transmission efficiency. For example, when the internal efficiency is 90% and the power transmission efficiency is 80%, this indicates that only 72% of the power output from the AC/DC converter612actually reaches the target resonator. Accordingly, the power controller619may adjust the pulse width so that a desired amount of power may be transferred to the source resonator614and the target resonator621.

The wireless power reception apparatus620includes the target resonator621, a rectifier622, the measurer623, the communication unit624, and a load.

The target resonator621receives power wirelessly via a mutual resonance with the source resonator614of the wireless power transmission apparatus610. In particular, a current may be induced in the target resonator621by the received wireless power due to the mutual resonance. The rectifier622rectifies an AC power received by the target resonator621to a DC power. The load may be a battery. The load may store the DC power rectified by the rectifier622. The measurer623measures a value of a current flowing in the target resonator621. The communication unit624transmits the value of the current measured by the measurer623to the communication unit616. The value of the current measured by the measurer623may be used for calculating a power transmission efficiency or a power transmission efficiency offset.

FIG. 7is a graph illustrating an example of wireless power transmission efficiencies depending on a turns ratio of a coil of a target resonator and a coil of a source resonator in a wireless power transmission system. Referring toFIG. 7, three cases in which the turns ratio is 6:6, 18:6, and 20:8 are illustrated.

As can seen fromFIG. 7, a power transmission efficiency is highest when the turns ratio is 6:6, which be simplified to 1:1. In particular, as the number of the turns of the coil of the source resonator becomes closer to the number of the turns of the coil of the target resonator, the power transmission efficiency increases. In view of such a characteristic, a source resonator and a target resonator may be designed and implemented so that the turns ratio of their coils is 1:1.

FIG. 8is a flowchart illustrating an example of a wireless power transmission method. Referring toFIG. 8, in810, a wireless power transmission apparatus measures a value of a current flowing in a source resonator.

In820, the wireless power transmission apparatus receives a value of a charging current of a battery from a wireless power reception apparatus. In this example, the value of the charging current of the battery varies as the battery of the wireless power reception apparatus is charged.

In830, the wireless power transmission apparatus controls an amount of power to be transmitted by the source resonator based on either one or both of the received value of the charging current and the measured value of the current flowing in the source resonator.

The wireless power transmission apparatus may determine a charging mode of the battery based on a change in the received value of the charging current, and generate a pulse signal having a pulse width adjusted based on the determined charging mode of the battery. The charging mode of the battery may be a CC mode in which the value of the charging current of the battery is constant, or a CV mode in which the value of the charging current of the battery is variable and a value of a charging voltage of the battery is constant.

The wireless power transmission apparatus may convert an AC power supplied from a power supply to a DC power based on the adjusted pulse width of the pulse signal, and convert the DC power to an AC power based on a resonant frequency of the source resonator.

The wireless power transmission apparatus may receive, from the wireless power reception apparatus, a value of a current flowing in a target resonator of the wireless power reception apparatus, calculate a power transmission efficiency offset by comparing the measured value of the current with the received value of the current flowing in the target resonator and calculating the power transmission efficiency offset based on a result of the comparing, and generate a pulse signal having a pulse width adjusted based on the calculated power transmission efficiency offset.

FIG. 9is a flowchart illustrating another example of a wireless power transmission method. Referring toFIG. 9, in910, a wireless power transmission apparatus determines a charging mode of a battery based on a change in a received value of a charging current of the battery. The charging mode of the battery may be a CC mode in which the value of the charging current of the battery is constant, or a CV mode in which the value of the charging current of the battery is variable and a value of a charging voltage of the battery is constant.

In920, the wireless power transmission apparatus calculates a power transmission efficiency offset by comparing a measured value of a current with a received value of a current flowing in a target resonator, and calculating the power transmission efficiency based on a result of the comparing.

In930, the wireless power transmission apparatus generates a pulse signal having a pulse width adjusted based on the calculated power transmission efficiency offset.

The wireless power transmission apparatus may control a power to be transmitted based on an internal efficiency and a power transmission efficiency, thereby transmitting an amount of power to be used by the wireless power reception apparatus more precisely.

The wireless power transmission apparatus may control a power to be transmitted based on a charging mode of a battery, thereby transmitting an amount of power to be used for charging the battery efficiently.

The wireless power reception apparatus may transmit to the wireless power transmission apparatus information on a value of a current to be used to charge a battery or a value of a current flowing in a target resonator, thereby providing information to be used for calculating a power transmission efficiency or a power transmission efficiency offset. The wireless power transmission apparatus may calculate the power transmission efficiency or the power transmission efficiency offset based on the information on the value of the current to be used to charge the battery or the value of the current flowing in the target resonator.

FIGS. 10A, 10B, 11A, 11B, 12A, and 12Bare diagrams illustrating examples of applications using a wireless power transmission apparatus.

FIG. 10Ais a diagram illustrating an example of wireless power charging between a pad1010and a mobile terminal1020, andFIG. 10Bis a diagram illustrating an example of wireless power charging between pads1030and1040and hearing aids1050and1060.

In the example inFIG. 10A, a wireless power transmitter is mounted in the pad1010, and a wireless power receiver is mounted in the mobile terminal1020. The pad1010may be used to charge a single mobile terminal, namely the mobile terminal1020.

In the example inFIG. 10B, two wireless power transmitters are respectively mounted in the pads1030and1040. The hearing aids1050and1060may be used for a left ear and a right ear, respectively. In this example, two wireless power receivers are respectively mounted in the hearing aids1050and1060.

FIG. 11Ais a diagram illustrating an example of wireless power charging between a mobile terminal1110and a tablet PC1120, andFIG. 11Bis a diagram illustrating an example of wireless power charging between mobile terminals1130and1140.

In the example inFIG. 11A, a wireless power transmitter and a wireless power receiver are mounted in the mobile terminal1110, and a wireless power transmitter and a wireless power receiver are mounted in the tablet PC1120. The mobile terminal1110and the tablet PC1120may wirelessly exchange power.

In example inFIG. 11B, a wireless power transmitter and a wireless power receiver are mounted in the mobile terminal1130, and a wireless power transmitter and a wireless power receiver are mounted in the mobile terminal1140. The mobile terminals1130and1140may wirelessly exchange power.

FIG. 12Ais a diagram illustrating an example of wireless power charging between an electronic device1210that is inserted into a human body, and a mobile terminal1220.FIG. 12Bis a diagram illustrating an example of wireless power charging between a hearing aid1230and a mobile terminal1240.

In the example inFIG. 12A, a wireless power transmitter and a wireless power receiver are mounted in the mobile terminal1220, and a wireless power receiver is mounted in the electronic device1210. The electronic device1210may be charged by receiving power from the mobile terminal1220.

In the example inFIG. 12B, a wireless power transmitter and a wireless power receiver are mounted in the mobile terminal11230, and a wireless power receiver is mounted in the hearing aid1230. The hearing aid1230may be charged by receiving power from the mobile terminal1240. Low-power electronic devices, such as Bluetooth earphones, may also be charged by receiving power from the mobile terminal1240.

In the following description ofFIGS. 13A through 15B, unless otherwise indicated, the term “resonator” may refer to both a source resonator and a target resonator. The resonators ofFIGS. 13A through 15Bmay be used as the resonators ofFIGS. 1 through 12B.

FIGS. 13A and 13Bare diagrams illustrating examples of a distribution of a magnetic field in a feeder and a resonator of a wireless power transmitter. When a resonator receives power supplied through a separate feeder, magnetic fields are formed in both the feeder and the resonator.

FIG. 13Ais a diagram illustrating an example of a structure of a wireless power transmitter in which a feeder1310and a resonator1320do not have a common ground. Referring toFIG. 13A, as an input current flows into the feeder1310through terminal labeled “+” and out of the feeder1310through a terminal labeled “−”, a magnetic field1330is formed by the input current. A direction1331of the magnetic field1330inside the feeder1310is into the plane ofFIG. 13A, and is opposite to a direction1333of the magnetic field1330outside the feeder1310, which is out of the plane ofFIG. 13A. The magnetic field1330formed by the feeder1310induces a current to flow in the resonator1320. The direction of the induced current in the resonator1320is opposite to a direction of the input current in the feeder1310, as indicated by the dashed lines with arrowheads inFIG. 13A.

The induced current in the resonator1320forms a magnetic field1340. A direction of the magnetic field generated by the induced current is the same at all positions inside the resonator1320, and is out of the plane ofFIG. 13A. Accordingly, a direction1341of the magnetic field1340formed by the resonator1320inside the feeder1310is the same as a direction1343of the magnetic field1340formed by the resonator1320outside the feeder1310.

Consequently, when the magnetic field1330formed by the feeder1310and the magnetic field1340formed by the resonator1320are combined, the strength of the total magnetic field inside the resonator1320decreases inside the feeder1310, but increases outside the feeder1310. In an example in which power is supplied to the resonator1320through the feeder1310configured as illustrated inFIG. 13A, the strength of the total magnetic field decreases in the center of the resonator1320, but increases outside the resonator1320. In another example in which a magnetic field is randomly or not uniformly distributed in the resonator1320, it is difficult to perform impedance matching since an input impedance will frequently vary. Additionally, when the strength of the total magnetic field increases, an efficiency of wireless power transmission increases. Conversely, when the strength of the total magnetic field decreases, the efficiency of wireless power transmission decreases. Accordingly, the power transmission efficiency is reduced on average when the magnetic field is randomly or not uniformly distributed in the resonator1320compared to when the magnetic field is uniformly distributed in the resonator1320.

FIG. 13Bis a diagram illustrating an example of a structure of a wireless power transmission apparatus in which a resonator1350and a feeder1360have a common ground. The resonator1350includes a capacitor1351. The feeder1360receives a radio-frequency (RF) signal via a port1361. When the RF signal is input to the feeder1360, an input current is generated in the feeder1360as indicated by the solid lines with arrowheads inFIG. 13B. The input current flowing in the feeder1360forms a magnetic field, and a current is induced in the resonator1350by the magnetic field as indicated by the dashed lines with arrowheads inFIG. 13B. Additionally, another magnetic field is generated by the induced current flowing in the resonator1350. In this example, a direction of the input current flowing in the feeder1360is opposite to a direction of the induced current flowing in the resonator1350. Accordingly, in a region between the resonator1350and the feeder1360, a direction1371of the magnetic field generated by the input current is the same as a direction1373of the magnetic field generated by the induced current, and thus the strength of the total magnetic field increases in the region between the resonator1350and the feeder1360. Conversely, inside the feeder1360, a direction1381of the magnetic field generated by the input current is opposite to a direction1383of the magnetic field generated by the induced current, and thus the strength of the total magnetic field decreases inside the feeder1360. Therefore, the strength of the total magnetic field decreases in the center of the resonator1350, but increases near an outer periphery of the resonator1350. Thus, a magnetic field may be more uniformly distributed in the resonator1550inFIG. 13B, compared to the structure ofFIG. 13A.

An input impedance may be adjusted by adjusting an internal area of the feeder1360. The input impedance is an impedance viewed in a direction from the feeder1360to the resonator1350. When the internal area of the feeder1360increases, the input impedance increases. Conversely, when the internal area of the feeder1360decreases, the input impedance decreases. Because the magnetic field is randomly distributed in the resonator1350despite a reduction in the input impedance, the input impedance may vary based on a location of a target. Accordingly, a separate matching network may be required to match the input impedance to an output impedance of a power amplifier. For example, when the input impedance increases, a separate matching network may be used to match the increased input impedance to a relatively low output impedance of the power amplifier.

FIGS. 14A and 14Bare diagrams illustrating an example of a wireless power transmission apparatus including a resonator and a feeder. Referring toFIG. 14A, the wireless power transmission apparatus includes a resonator1410and a feeder1420. The resonator1410includes include a capacitor1411. The feeder1420is electrically connected to both ends of the capacitor1411.

FIG. 14Bis a diagram illustrating in greater detail a structure of the wireless power transmission apparatus ofFIG. 14A. The resonator1410includes a first transmission line (not identified by a reference numeral inFIG. 14B, but formed by various elements inFIG. 14Bas discussed below), a first conductor1441, a second conductor1442, and at least one capacitor1450.

The capacitor1450is inserted in series between a first signal conducting portion1431and a second signal conducting portion1432, causing an electric field to be concentrated in the capacitor1450. Generally, a transmission line includes at least one conductor in an upper portion of the transmission line, and at least one conductor in a lower portion of the transmission line. A current may flow through the at least one conductor disposed in the upper portion of the transmission line, and the at least one conductor disposed in the lower portion of the transmission line may be electrically grounded. In this example, a conductor disposed in an upper portion of the first transmission line inFIG. 14Bis separated into two portions that will be referred to as the first signal conducting portion1431and the second signal conducting portion1432. A conductor disposed in a lower portion of the first transmission line inFIG. 14Bwill be referred to as a first ground conducting portion1433.

As illustrated inFIG. 14B, the resonator1410has a generally two-dimensional (2D) structure. The first transmission line includes the first signal conducting portion1431and the second signal conducting portion1432in the upper portion of the first transmission line, and includes the first ground conducting portion1433in the lower portion of the first transmission line. The first signal conducting portion1431and the second signal conducting portion1432are disposed to face the first ground conducting portion1433. A current flows through the first signal conducting portion1431and the second signal conducting portion1432.

One end of the first signal conducting portion1431is connected to one end of the first conductor1441, the other end of the first signal conducting portion1431is connected to one end of the capacitor1450, and the other end of the first conductor1441is connected to one end of the first ground conducting portion1433. One end of the second signal conducting portion1432is connected to one end of the second conductor1442, the other end of the second signal conducting portion1432is connected to the other end of the capacitor1450, and the other end of the second conductor1442is connected to the other end of the first ground conducting portion1433. Accordingly, the first signal conducting portion1431, the second signal conducting portion1432, the first ground conducting portion1433, the first conductor1441, and the second conductor1442are connected to each other, causing the resonator1410to have an electrically closed loop structure. The term “loop structure” includes a polygonal structure, a circular structure, a rectangular structure, and any other geometrical structure that is closed, i.e., that does not have any opening in its perimeter. The phrase “having a loop structure” indicates a structure that is electrically closed.

The capacitor1450is inserted into an intermediate portion of the first transmission line. In the example inFIG. 14B, the capacitor1450is inserted into a space between the first signal conducting portion1431and the second signal conducting portion1432. The capacitor1450may be a lumped element capacitor, a distributed element capacitor, or any other type of capacitor known to one of ordinary skill in the art. For example, a distributed element capacitor may include zigzagged conductor lines and a dielectric material having a relatively high permittivity disposed between the zigzagged conductor lines.

The capacitor1450inserted into the first transmission may cause the resonator1410to have a characteristic of a metamaterial. A metamaterial is a material having a predetermined electrical property that is not found in nature, and thus may have an artificially designed structure. All materials existing in nature have a magnetic permeability and a permittivity. Most materials have a positive magnetic permeability and/or a positive permittivity.

For most materials, a right-hand rule may be applied to an electric field, a magnetic field, and a Poynting vector of the materials, so the materials may be referred to as right-handed materials (RHMs). However, a metamaterial having a magnetic permeability and/or a permittivity that is not found in nature may be classified into an epsilon negative (ENG) material, a mu negative (MNG) material, a double negative (DNG) material, a negative refractive index (NRI) material, a left-handed (LH) material, and any other metamaterial classification known to one of ordinary skill in the art based on a sign of the magnetic permeability of the metamaterial and a sign of the permittivity of the metamaterial.

If the capacitor1450is a lumped element capacitor and a capacitance of the capacitor1450is appropriately determined, the resonator1410may have a characteristic of the metamaterial. If the resonator1410is caused to have a negative magnetic permeability by appropriately adjusting the capacitance of the capacitor1450, the resonator1410may also be referred to as an MNG resonator. Various criteria may be applied to determine the capacitance of the capacitor1450. For example, the various criteria may include a criterion for enabling the resonator1410to have the characteristic of the metamaterial, a criterion for enabling the resonator1410to have a negative magnetic permeability at a target frequency, a criterion for enabling the resonator1410to have a zeroth order resonance characteristic at the target frequency, and any other suitable criterion. Based on any one or any combination of the aforementioned criteria, the capacitance of the capacitor1450may be determined.

The resonator1410, hereinafter referred to as the MNG resonator1410, may have a zeroth order resonance characteristic of having a resonant frequency when a propagation constant is “0”. If the resonator1410has the zeroth order resonance characteristic, the resonant frequency is independent of a physical size of the MNG resonator1410. By appropriately changing the capacitance of the capacitor1450, the resonant frequency of the MNG resonator1410may be changed without changing the physical size of the MNG resonator1410.

In a near field, the electric field is concentrated on the capacitor1450inserted into the first transmission line, causing the magnetic field to become dominant in the near field. The MNG resonator1410has a relatively high Q-factor when the capacitor1450is a lumped element capacitor, and thereby increasing a power transmission efficiency. The Q-factor indicates a level of an ohmic loss or a ratio of a reactance with respect to a resistance in the wireless power transmission. As will be understood by one of ordinary skill in the art, the efficiency of the wireless power transmission will increase as the Q-factor increases.

Although not illustrated inFIG. 14B, a magnetic core passing through the MNG resonator1410may be provided to increase a power transmission distance.

Referring toFIG. 14B, the feeder1420may include a second transmission line (not identified by a reference numeral inFIG. 14B, but formed by various elements inFIG. 14Bas discussed below), a third conductor1471, a fourth conductor1472, a fifth conductor1481, and a sixth conductor1482.

The second transmission line includes a third signal conducting portion1461and a fourth signal conducting portion1462in an upper portion of the second transmission line, and includes a second ground conducting portion1463in a lower portion of the second transmission line. The third signal conducting portion1461and the fourth signal conducting portion1462are disposed to face the second ground conducting portion1463. A current flows through the third signal conducting portion1461and the fourth signal conducting portion1462.

One end of the third signal conducting portion1461is connected to one end of the third conductor1471, the other end of the third signal conducting portion1461is connected to one end of the fifth conductor1481, and the other end of the third conductor1471is connected to one end of the second ground conducting portion1463. One end of the fourth signal conducting portion1462is connected to one end of the fourth conductor1472, the other end of the fourth signal conducting portion1462is connected to one end of the sixth conductor1482, and the other end of the fourth conductor1472is connected to the other end of the second ground conducting portion1463. The other end of the fifth conductor1481is connected to the first signal conducting portion1431at or near where the first signal conducting portion1431is connected to one end of the capacitor1450, and the other end of the sixth conductor1482is connected to the second signal conducting portion1432at or near where the second signal conducting portion1432is connected to the other end of the capacitor1450. Thus, the fifth conductor1481and the sixth conductor1482are connected in parallel with both ends of the capacitor1450. The fifth conductor1481and the sixth conductor1482may be used as an input port to receive an RF signal as an input.

Accordingly, the third signal conducting portion1461, the fourth signal conducting portion1462, the second ground conducting portion1463, the third conductor1471, the fourth conductor1472, the fifth conductor1481, the sixth conductor1482, and the resonator1410are connected to each other, causing the resonator1410and the feeder1420to have an electrically closed loop structure. The term “loop structure” includes a polygonal structure, a circular structure, a rectangular structure, and any other geometrical structure that is closed, i.e., that does not have any opening in its perimeter. The phrase “having a loop structure” indicates a structure that is electrically closed.

If an RF signal is input to the fifth conductor1481or the sixth conductor1482, an input current flows through the feeder1420and the resonator1410, generating a magnetic field that induces a current in the resonator1410. A direction of the input current flowing through the feeder1420is the same as a direction of the induced current flowing through the resonator1410, thereby causing the strength of the total magnetic field to increase in the center of the resonator1410, and decrease near the outer periphery of the resonator1410.

An input impedance is determined based by an area of a region between the resonator1410and the feeder1420. Accordingly, a separate matching network used to match the input impedance to an output impedance of a power amplifier may not be necessary. However, even if a matching network is used, the input impedance may be adjusted by adjusting a size of the feeder1420, and accordingly a structure of the matching network may be simplified. The simplified structure of the matching network reduces a matching loss of the matching network.

The second transmission line, the third conductor1471, the fourth conductor1472, the fifth conductor1481, and the sixth conductor1482of the feeder1420may have the same structure as the resonator1410. For example, if the resonator1410has a loop structure, the feeder1420may also have a loop structure. As another example if the resonator1410has a circular structure, the feeder1420may also have a circular structure.

FIG. 15Ais a diagram illustrating an example of a distribution of a magnetic field inside a resonator produced by feeding of a feeder.FIG. 15Amore simply illustrates the resonator1410and the feeder1420ofFIGS. 14A and 14B, and the following description ofFIG. 15Arefers to elements that are shown inFIGS. 14A and 14B.

A feeding operation may be an operation of supplying power to a source resonator in wireless power transmission, or an operation of supplying AC power to a rectifier in wireless power transmission.FIG. 15Aillustrates a direction of an input current flowing in the feeder as indicated by the solid lines with arrowheads, and a direction of an induced current flowing in the source resonator as indicated by the dashed lines with arrowheads. Additionally,FIG. 15Aillustrates a direction of a magnetic field generated by the input current of the feeder, and a direction of a magnetic field generated by the induced current of the source resonator.

Referring toFIG. 15A, the fifth conductor1481or the sixth conductor1482of the feeder1420ofFIG. 14Amay be used as an input port1510. In the example inFIG. 15A, the sixth conductor1482of the feeder1420is being used as the input1510. An RF signal is input to the input port1510. The RF signal may be output from a power amplifier. The power amplifier may increase and decrease an amplitude of the RF signal based on a power requirement of a target. The RF signal input to the input port1510is represented inFIG. 15Aas an input current flowing in the feeder1420. The input current flows in a clockwise direction in the feeder1420along the second transmission line of the feeder1420. The fifth conductor1481and the sixth conductor1482of the feeder1420may be electrically connected to the resonator1410. More specifically, the fifth conductor1481of the feeder1420is connected to the first signal conducting portion1431of the resonator1410, and the sixth conductor1482of the feeder1420is connected to the second signal conducting portion1432of the resonator1410. Accordingly, the input current flows in both the resonator1410and the feeder1420. The input current flows in a counterclockwise direction in the resonator1410. The input current flowing in the resonator1410generates a magnetic field, and the magnetic field induces a current in the resonator1410. The induced current flows in a clockwise direction in the resonator1410along the first transmission line of the resonator1410. The induced current in the resonator1410transfers energy to the capacitor1411of the resonator1410, and also generates a magnetic field. InFIG. 15A, the input current flowing in the feeder1420and the resonator1410is indicated by the solid lines with arrowheads, and the induced current flowing in the resonator1410is indicated by the dashed lines with arrowheads.

A direction of a magnetic field generated by a current is determined based on the right-hand rule. As illustrated inFIG. 15A, inside the feeder1420, a direction1521of the magnetic field generated by the input current flowing in the feeder1420is the same as a direction1523of the magnetic field generated by the induced current flowing in the resonator1410. Accordingly, the strength of the total magnetic field increases inside the feeder1420.

In contrast, as illustrated inFIG. 15A, in a region between the feeder1420and the resonator1410, a direction1533of a magnetic field generated by the input current flowing in the feeder1420is opposite to a direction1531of the magnetic field generated by the induced current flowing in the resonator1410. Accordingly, the strength of the total magnetic field decreases in the region between the feeder1420and the resonator1410.

Typically, in a resonator having a loop structure, a strength of a magnetic field decreases in the center of the resonator, and increases near an outer periphery of the resonator. However, referring toFIG. 15A, since the feeder1420is electrically connected to both ends of the capacitor1411of the resonator1410, the direction of the induced current in the resonator1410is the same as the direction of the input current in the feeder1420. Since the direction of the induced current in the resonator1420is the same as the direction of the input current in the feeder1420, the strength of the total magnetic field increases inside the feeder1420, and decreases outside the feeder1420. As a result, due to the feeder1420, the strength of the total magnetic field increases in the center of the resonator1410having the loop structure, and decreases near an outer periphery of the resonator1410, thereby compensating for the normal characteristic of the resonator1410having the loop structure in which the magnetic field decreases in the center of the resonator1410, and increases near an outer periphery of the resonator1410. Thus, the strength of the total magnetic field may be constant inside the resonator1410.

A power transmission efficiency for transferring a wireless power from a source resonator to a target resonator is proportional to the strength of the total magnetic field generated in the source resonator. Accordingly, when the strength of the total magnetic field increases inside the source resonator, the power transmission efficiency also increases.

FIG. 15Bis a diagram illustrating examples of equivalent circuits of a feeder and a resonator. Referring toFIG. 15B, a feeder1540and a resonator1550may be represented by the equivalent circuits inFIG. 15B. The feeder1540is represented as an inductor having an inductance Lf, and the resonator1550is represented as a series connection of an inductor having an inductance L coupled to the inductance Lfof the feeder1540by a mutual inductance M, a capacitor having a capacitance C, and a resistor having a resistance R. An input impedance Zinviewed in a direction from the feeder1540to the resonator1550may be expressed by the following Equation 1:

In Equation 1, M denotes a mutual inductance between the feeder1540and the resonator1550, ω denotes a resonant frequency of the feeder1540and the resonator1550, and Z denotes an impedance viewed in a direction from the resonator1550to a target. As can be seen from Equation 1, the input impedance Zinis proportional to the square of the mutual inductance M. Accordingly, the input impedance Zinmay be adjusted by adjusting the mutual inductance M. The mutual inductance M depends on an area of a region between the feeder1540and the resonator1550. The area of the region between the feeder1540and the resonator1550may be adjusted by adjusting a size of the feeder1540, thereby adjusting the mutual inductance M and the input impedance Zin. Since the input impedance Zinmay be adjusted by adjusting the size of the feeder1540, it may be unnecessary to use a separate matching network to perform impedance matching with an output impedance of a power amplifier.

If the resonator1550and the feeder1540inFIG. 15Bare included in a wireless power reception apparatus, a magnetic field may be distributed as illustrated inFIG. 15A. In this case, the resonator1550may operate as a target resonator1550, and may receive wireless power from a source resonator via magnetic coupling. The received wireless power induces a current in the target resonator1550. The induced current in the target resonator1550generates a magnetic field, which induces a current in the feeder1540. If the target resonator1550is connected to the feeder1540as illustrated inFIG. 15A, a direction of the induced current flowing in the resonator1550will be the same as a direction of the induced current flowing in the feeder1540. Accordingly, for the reasons discussed above in connection withFIG. 15A, the strength of the total magnetic field will increase inside the feeder1540, and will decrease in a region between the feeder1540and the target resonator1550.

FIG. 16is a diagram illustrating an example of an electric vehicle charging system. Referring toFIG. 16, an electric vehicle charging system1600includes a source system1610, a source resonator1620, a target resonator1630, a target system1640, and an electric vehicle battery1650.

In one example, the electric vehicle charging system1600has a structure similar to the structure of the wireless power transmission system ofFIG. 1. The source system1610and the source resonator1620in the electric vehicle charging system1600operate as a source. The target resonator1630and the target system1640in the electric vehicle charging system1600operate as a target.

In one example, the source system1610includes a variable SMPS, a power detector, a power amplifier, a matching network, a TX controller, and a communication unit similar to those of the source110ofFIG. 1. In one example, the target system1640includes a matching network, a rectifier, a voltage detector, a DC/DC converter, a power detector, a communication unit, and a RX controller similar to those of the target120ofFIG. 1. The electric vehicle battery1650is charged by the target system1640. The electric vehicle charging system1600may use a resonant frequency in a band of a few kilohertz (kHz) to tens of MHz to wirelessly transmit power.

The source system1610generates power based on a type of the vehicle being charged, a capacity of the electric vehicle battery1650, and a charging state of the electric vehicle battery1650, and wirelessly transmits the generated power to the target system1640via magnetic coupling between the source resonator1620and the target resonator1630.

The source system1610may control an alignment of the source resonator1620and the target resonator1630. For example, when the source resonator1620and the target resonator1630are not aligned, the TX controller of the source system1610may transmit a message to the target system1640to control the alignment of the source resonator1620and the target resonator1630.

For example, when the target resonator1630is not located in a position enabling maximum magnetic coupling, the source resonator1620and the target resonator1630are not properly aligned. When a vehicle does not stop at a proper position to accurately align the source resonator1820and the target resonator1830, the source system1610may instruct a position of the vehicle to be adjusted to control the source resonator1620and the target resonator1630to be aligned. However, this is just an example, and other methods of aligning the source resonator1820and the target resonator1830may be used.

The source system1610and the target system1640may transmit or receive an ID of a vehicle and exchange various messages by communicating with each other.

The descriptions ofFIGS. 2 through 15Bare also applicable to the electric vehicle charging system1600. However, the electric vehicle charging system1600may use a resonant frequency in a band of a few kHz to tens of MHz, and may transmit power that is equal to or higher than tens of watts to charge the electric vehicle battery1650.

The TX controller114, the communication units115,124,260,460,550,616, and624, the RX controller125, the measurers250,450,540,615, and623, the power controllers270,310,490, and619, the charging mode determiners271and491, the pulse signal generators273,313, and495, the offset calculators311and493, the first comparators470and617, the second comparators480and618, the controller560, the source system1610, and the target system1640inFIGS. 1-6 and 16described above that perform the operations illustrated inFIGS. 8 and 9may be implemented using one or more hardware components, one or more software components, or a combination of one or more hardware components and one or more software components.

A hardware component may be, for example, a physical device that physically performs one or more operations, but is not limited thereto. Examples of hardware components include resistors, capacitors, inductors, power supplies, frequency generators, operational amplifiers, power amplifiers, low-pass filters, high-pass filters, band-pass filters, analog-to-digital converters, digital-to-analog converters, and processing devices.

A software component may be implemented, for example, by a processing device controlled by software or instructions to perform one or more operations, but is not limited thereto. A computer, controller, or other control device may cause the processing device to run the software or execute the instructions. One software component may be implemented by one processing device, or two or more software components may be implemented by one processing device, or one software component may be implemented by two or more processing devices, or two or more software components may be implemented by two or more processing devices.

A processing device may be implemented using one or more general-purpose or special-purpose computers, such as, for example, a processor, a controller and an arithmetic logic unit, a digital signal processor, a microcomputer, a field-programmable array, a programmable logic unit, a microprocessor, or any other device capable of running software or executing instructions. The processing device may run an operating system (OS), and may run one or more software applications that operate under the OS. The processing device may access, store, manipulate, process, and create data when running the software or executing the instructions. For simplicity, the singular term “processing device” may be used in the description, but one of ordinary skill in the art will appreciate that a processing device may include multiple processing elements and multiple types of processing elements. For example, a processing device may include one or more processors, or one or more processors and one or more controllers. In addition, different processing configurations are possible, such as parallel processors or multi-core processors.

A processing device configured to implement a software component to perform an operation A may include a processor programmed to run software or execute instructions to control the processor to perform operation A. In addition, a processing device configured to implement a software component to perform an operation A, an operation B, and an operation C may have various configurations, such as, for example, a processor configured to implement a software component to perform operations A, B, and C; a first processor configured to implement a software component to perform operation A, and a second processor configured to implement a software component to perform operations B and C; a first processor configured to implement a software component to perform operations A and B, and a second processor configured to implement a software component to perform operation C; a first processor configured to implement a software component to perform operation A, a second processor configured to implement a software component to perform operation B, and a third processor configured to implement a software component to perform operation C; a first processor configured to implement a software component to perform operations A, B, and C, and a second processor configured to implement a software component to perform operations A, B, and C, or any other configuration of one or more processors each implementing one or more of operations A, B, and C. Although these examples refer to three operations A, B, C, the number of operations that may implemented is not limited to three, but may be any number of operations required to achieve a desired result or perform a desired task.

Software or instructions for controlling a processing device to implement a software component may include a computer program, a piece of code, an instruction, or some combination thereof, for independently or collectively instructing or configuring the processing device to perform one or more desired operations. The software or instructions may include machine code that may be directly executed by the processing device, such as machine code produced by a compiler, and/or higher-level code that may be executed by the processing device using an interpreter. The software or instructions and any associated data, data files, and data structures may be embodied permanently or temporarily in any type of machine, component, physical or virtual equipment, computer storage medium or device, or a propagated signal wave capable of providing instructions or data to or being interpreted by the processing device. The software or instructions and any associated data, data files, and data structures also may be distributed over network-coupled computer systems so that the software or instructions and any associated data, data files, and data structures are stored and executed in a distributed fashion.

For example, the software or instructions and any associated data, data files, and data structures may be recorded, stored, or fixed in one or more non-transitory computer-readable storage media. A non-transitory computer-readable storage medium may be any data storage device that is capable of storing the software or instructions and any associated data, data files, and data structures so that they can be read by a computer system or processing device. Examples of a non-transitory computer-readable storage medium include read-only memory (ROM), random-access memory (RAM), flash memory, CD-ROMs, CD-Rs, CD+Rs, CD-RWs, CD+RWs, DVD-ROMs, DVD-Rs, DVD+Rs, DVD-RWs, DVD+RWs, DVD-RAMs, BD-ROMs, BD-Rs, BD-R LTHs, BD-REs, magnetic tapes, floppy disks, magneto-optical data storage devices, optical data storage devices, hard disks, solid-state disks, or any other non-transitory computer-readable storage medium known to one of ordinary skill in the art.

Functional programs, codes, and code segments for implementing the examples disclosed herein can be easily constructed by a programmer skilled in the art to which the examples pertain based on the drawings and their corresponding descriptions as provided herein.

While this disclosure includes specific examples, it will be apparent to one of ordinary skill in the art that various modifications may be made in these examples without departing from the spirit and scope of the claims and their equivalents. Suitable results may be achieved if the described techniques are performed in a different order, and/or if components in a described system, architecture, device, or circuit are combined in a different manner, and/or replaced or supplemented by other components or their equivalents. Therefore, the scope of the disclosure is defined not by the detailed description, but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents are to be construed as being included in the disclosure.