Washing machine and method of controlling the same

The present disclosure relates to a washing machine, having an actively movable balancer, and method of controlling the same. The washing machine according to an embodiment of the present disclosure includes: a balancing unit to move along a circumference of a drum to reduce imbalance due to an unbalanced distribution of the laundry; a transmission coil provided at a tub to generate a wireless power signal and transmit power wirelessly to the balancing unit; a transmission converter to apply power at a driving frequency to the transmission coil; a voltage measurer to measure a transmission voltage, which is a voltage of the transmission coil; and a transmission controller to control the transmission converter based on the transmission voltage measured by the voltage measurer, thereby transmitting sufficient power wirelessly to the balancing unit in a short period of time.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Korean Patent Application No. 10-2017-0034839, filed on Mar. 20, 2017, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety.

FIELD

The present disclosure relates to a washing machine and method of controlling the same, and more particularly to a washing machine having an actively movable balancer, and a method of controlling the same.

BACKGROUND

A washing machine is an appliance for cleaning by performing washing, rinsing, and spin-drying cycles to remove contaminants from clothing, bedding, and the like (hereinafter referred to as “laundry”) by using water, detergent, and mechanical operations.

The washing machine is provided with a balancer to reduce imbalance which occurs when laundry in a drum is unevenly distributed. As the balancer for use in the washing machine, a ball balancer or a liquid balancer is used. However, there is a problem in that the ball balancer or the liquid balancer moves passively according to rotation of a drum, such that as the ball balancer or the liquid balancer moves to an opposite side of the center of mass of laundry, the drum continuously rotates until the imbalance is reduced. In order to solve such problem, a method of actively moving the balancer is suggested.

In order for the balancer to move actively, it is required to supply power to the balancer. Recently, there is suggested a method of transmitting power wirelessly by using a transmitting coil disposed around the drum and a receiving coil disposed around the balancer. However, as the balancer rotates along with the drum, the transmitting coil and the receiving coil meet for a very short period of time as the drum rotates. Accordingly, there is a need for a method of supplying sufficient power for the movement of the balancer even in a very short period of time.

SUMMARY

It is an object of the present invention to provide a washing machine for wirelessly transmitting sufficient power to a balancing unit in a short period of time, and a method of controlling the same.

It is another object of the present invention to provide a washing machine for wirelessly transmitting power to the balancing unit by considering safety of an electronic device for wireless power transmission, and a method of controlling the same.

The objects of the present invention are not limited to the aforementioned objects and other objects undescribed herein will be clearly understood by those skilled in the art from the following description.

In accordance with the present invention, the above and other objects can be accomplished by providing a washing machine including: a balancing unit which moves along a circumference of a drum to reduce imbalance which occurs due to an unbalanced distribution of the laundry; a transmission coil which is provided at a tub, and generates a wireless power signal to transmit power wirelessly to the balancing unit; a transmission converter configured to apply power at a driving frequency to the transmission coil; a voltage measurer configured to measure a transmission voltage, which is a voltage of the transmission coil; and a transmission controller configured to control the transmission converter based on the transmission voltage measured by the voltage measurer, thereby transmitting sufficient power wirelessly to the balancing unit in a short period of time.

The transmission controller may convert the transmission voltage to a coil current, which is an electric current, and may change the driving frequency of the transmission converter according to the coil current. In this case, the transmission controller may convert the transmission voltage to the coil current by using a predetermined linear relation.

In response to the coil current being equal to or less than a predetermined minimum current, the transmission controller may increase the driving frequency, and in response to the coil current being equal to or higher than a predetermined maximum current, the transmission controller may decrease the driving frequency.

The minimum current may be set based on a minimum power required for the balancing unit to move actively; and the maximum current may be set by considering safety of the balancing unit.

Further, in accordance with the present invention, the above and other objects can be accomplished by providing a method of controlling a washing machine, the method including: generating a wireless power signal at a set driving frequency and transmitting the generated wireless power signal to the balancing unit by the wireless power transmitter; measuring a transmission voltage, which is a voltage of a transmission coil which generates a wireless power signal; and changing the driving frequency from the transmission voltage.

The changing of the driving frequency from the transmission voltage may include converting the transmission voltage to a coil current, which is an electric current, by using a predetermined linear relation; and in response to the coil current being equal to or less than a predetermined minimum current, increasing the driving frequency, and in response to the coil current being equal to or higher than a predetermined maximum current, decreasing the driving frequency.

The minimum current may be set based on a minimum power required for the balancing unit to move actively; and the maximum current may be set by considering safety of the balancing unit or the wireless power transmitter.

The specifics of other embodiments are included in the detailed description and drawings.

The washing machine and method of controlling the same of the present disclosure have one or more of the following effects.

First, even when the balancing unit rotates along with the drum, the wireless power transmitter may wirelessly transmit sufficient power to the balancing unit in a short period of time.

Secondly, even when sufficient power may be transmitted by controlling the wireless power transmitter, electronic components of the wireless power transmitter or the balancing unit may be prevented from being damaged by fire.

Thirdly, even when the wireless power transmitter may not communicate with the balancing unit which receives power, there is no problem in wireless power transmission by only controlling the wireless power transmitter.

The effects of the present disclosure are not limited to the above-described effects, and other effects undescribed herein may be clearly understood by those skilled in the art from the claims.

DETAILED DESCRIPTION

Advantages and features of the present disclosure and methods for accomplishing the same will be more clearly understood from exemplary embodiments described below with reference to the accompanying drawings. However, the present disclosure is not limited to the following embodiments, but may be implemented in various different forms. The embodiments are provided only to complete disclosure of the present disclosure and to fully provide a person having ordinary skill in the art to which the present disclosure pertains with the category of the present disclosure, and the present disclosure will be defined by the scope of the appended claims. Like reference numerals generally denote like elements through the specification.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings for explaining a washing machine and a method of controlling the same.

FIG. 1is a cross-sectional view of a washing machine according to an embodiment of the present disclosure;FIG. 2is a perspective view of a tub of a washing machine according to an embodiment of the present disclosure; andFIG. 3is a perspective view of a drum of a washing machine according to an embodiment of the present disclosure.

The washing machine100according to an embodiment of the present disclosure includes a cabinet111which forms an external appearance of the washing machine100; a door112which opens and closes one side of the cabinet111so that laundry may be put into the cabinet111; a tub122which is provided in the cabinet111, is supported by the cabinet111, and in which wash water is contained; a drum124which has a cylindrical shape, is provided in the tub122, and rotates when the laundry is loaded; a drum motor113which provides torque to the drum124to rotate the drum124; a balancing unit300which moves along the circumference of the drum124to reduce imbalance which occurs due to an unbalanced distribution of laundry when the drum124rotates; a detergent box133in which detergent is held; and a control panel114which receives a user's input and displays status of a washing machine.

The cabinet111is provided with a laundry inlet hole111a, through which laundry is loaded into the cabinet111. The door112is rotatably connected with the cabinet111to open and close the laundry inlet hole111a. The cabinet111is provided with the control panel114. The cabinet111is provided with the detergent box133which may be withdrawn therefrom.

A spring115and a damper117are provided in the cabinet111to absorb shock of the tub122. The tub122contains wash water. The tub122is disposed outside the drum124while surrounding the drum124.

The tub122includes: a tub main body122awhich has a cylindrical shape and both ends of which are open; a front tub cover122bwhich has a ring shape and is disposed at a front side of the tub main body122a; a rear tub cover122cwhich has a disc shape and is disposed at a rear side of the tub main body122a. Hereinafter, the front side refers to the side of the door112, and the rear side refers to the side of the drum motor113. A tub hole122dis formed at the front tub cover122b. The tub hole122dis formed to communicate with the laundry inlet hole111ato allow the laundry to be put into the drum124.

The drum motor113is provided at the rear tub cover122cto generate torque. The drum motor113is connected with a rotation axis116to rotate the drum124. The drum motor113may rotate the drum124at various speeds and directions. The drum motor113includes: a stator (not shown) wound with a coil; and a rotor (not shown) which rotates by generating electromagnetic interaction with the coil.

The rotation axis116connects the drum motor113with the drum124. The rotation axis116transfers torque of the drum motor113to the drum144to rotate the drum124. One end of the rotation axis116is connected to the center of rotation at the rear side of the drum124, and the other end of the rotation axis116is connected with the rotor (not shown) of the drum motor113.

The drum124rotates with the laundry loaded therein. The drum124is disposed in the tub122. The drum124is formed in a cylindrical shape and is rotatable. The drum124has a plurality of through-holes through which wash water may pass. The drum124rotates by receiving the torque of the drum motor213.

A drum hole124ais provided at a front side of the drum124. The drum hole124ais formed to communicate with the laundry inlet hole111aand the tub hole122dso that the laundry may put into the drum124. A guide rail125is connected to a front and/or a rear circumference of the drum124. In the embodiment, the guide rail125is provided on a front circumference of the drum124.

A gasket128seals a space between the tub122and the cabinet111. The gasket128is interposed between the opening of the tub122and the laundry inlet hole111a. The gasket128absorbs shock which is delivered to the door112when the drum124rotates, and prevents wash water in the tub122from leaking to the outside. The gasket128may be provided with a circulation nozzle127which sprays wash water into the drum124.

The detergent box133may hold a detergent, a fabric softener, bleach, and the like. It is desired that the detergent box133is retractably provided at the front surface of the cabinet111. When wash water is supplied, the detergent in the detergent box133is mixed with the wash water to be introduced into the tub122.

The cabinet111includes: a water supply valve131which adjusts introduction of the wash water supplied from an external water source; a water supply passage132through which the wash water, introduced into the water supply valve, flows to the detergent box133; and a water supply pipe134through which the wash water, mixed with the detergent in the detergent box133, is introduced into the tub122.

The cabinet111includes: a drain pipe135through which the wash water in the tub122is drained; a pump136which discharges the wash water in the tub122; a circulation passage137which circulates the wash water; a circulation nozzle127which introduces the wash water is into the drum124; and a drain passage138through which the wash water is drained to the outside. Depending on embodiments, the pump136may include a circulation pump and a drain pump which may be connected to the circulation passage137and the drain passage138respectively.

A plurality of balancing units300move along the guide rail125of the drum124, to change the center of gravity of the drum124. In this case, the center of gravity of the drum124does not refer to the center of mass of the drum124itself, but refers to a common center of gravity of objects, including the drum124, the laundry which is loaded in the drum124, the guide rail125, the plurality of balancing units300, and other elements attached to the drum24, which rotate along with the drum124when the drum124rotates.

The plurality of balancing units300move along the front circumference of the drum124, to adjust the center of gravity of the drum124when laundry is unevenly distributed. When the drum124rotates with the unbalanced laundry, vibration and noise are caused by imbalance, in which a geometrical center of the rotation axis116(the center of gravity) of the drum124does not coincide with a real center of gravity of the drum124. The plurality of balancing units300may reduce the imbalance of the drum124by causing the center of gravity of the drum124to be close to the rotation axis116. In the embodiment, the plurality of balancing units300are two units of a first balancing unit300aand a second balancing unit300b.

The plurality of balancing units300move actively along the guide rail125. The active movement refers to movement of the plurality of balancing units300along the guide rail125by using their own power.

The guide rail125is a passage where the plurality of balancing units300move. The guide rail125is formed in a ring shape and is connected to a front end circumference of the drum124.

A transmission coil240for wireless power transmission to the plurality of balancing units300is disposed at the front tub cover122band/or the rear tub cover122c. In the embodiment, the transmission coil240is disposed at the front tub cover122b. The transmission coil240is disposed at a position facing the guide rail125. The transmission coil240is formed as a coil which generates a wireless power signal which is a magnetic field. The transmission coil240will be described in detail later with reference toFIGS. 7 and 8.

The control panel114may include: an input unit (not shown), which receives input of wash cycles selected by a user, or input of various operation commands such as operation time of wash cycles, reservation, and the like; and a display unit (not shown) which displays an operation state of the washing machine100.

FIG. 4is a partial perspective view of a washing machine according to an embodiment of the present disclosure;FIG. 5is a partial cross-sectional view of a washing machine according to an embodiment of the present disclosure; andFIG. 6is an exploded perspective view of a balancing unit of a washing machine according to an embodiment of the present disclosure.

The balancing unit300according to an embodiment of the present disclosure includes: a reception coil310which generates electric power by electromagnetic induction by receiving the wireless power signal from the transmission coil240; a driving module330which generates driving power by using the electric power generated by the reception coil310; a pinion gear340which rotates by receiving the driving power from the driving module330; an upper frame350which includes the driving module330and the pinion gear340; a lower frame370which is slidably connected with the upper frame350; an elastic body390interposed between the upper frame350and the lower frame370; and an electronic component module320in which electronic components are included.

The reception coil310generates power by electromagnetic induction by receiving the wireless power signal, which is a magnetic field, generated by the transmission coil240. The reception coil310is disposed on a surface that faces the tub122of the upper frame350so as to oppose the transmission coil240. The reception coil310is formed as a coil which generates electric power by electromagnetic induction caused by a magnetic field. The reception coil310will be described in detail later with reference toFIGS. 7 and 8.

The driving module330may generate driving power by using electric power, which is supplied from an external source and is transmitted wirelessly through the transmission coil240and the reception coil310. It is desired that the driving module330is a motor which generates torque. The driving module330rotates the pinion gear340. In the case where the driving module330is a motor, a worm gear (not shown) is interposed between the motor and the pinion gear340, such that the worm gear may rotate the pinion gear340. It is desired that the driving module330is disposed at the upper frame350.

The pinion gear340rotates by receiving driving power from the driving module330. A rack gear125ais disposed on an inner diameter surface of the guide rail125; and the pinion gear340is engaged with the rack gear125a.

The rack gear125ais formed along the inner diameter surface of the guide rail125. The cross-section of the guide rail125is formed in a square shape, and the inner diameter surface of the guide rail125refers to a surface located close to the center of rotation of the drum124, among the inner side surfaces of the guide rail125.

The pinion gear340rotates while being engaged with the rack gear125ato actively move the balancing unit300. As the pinion gear340is engaged with the rack gear125a, the balancing unit300may be prevented from moving freely by the dead load or rotation of the drum124.

The upper frame350forms the frame of the balancing unit300. The upper frame350is disposed on the inner diameter surface of the guide rail125. The upper frame350has a side surface which is formed in an arc shape so as to move along the guide rail125.

The upper frame350includes the driving module330, the pinion gear340, the electronic component module320, an upper roller360, and the transmission coil240. The upper frame350is connected with the lower frame370, and the elastic body390is interposed between the upper frame350and the lower frame370.

The electronic component module320includes various electronic components, which are provided for driving the driving module330by using electric power generated by the transmission coil240.

The upper roller360is rotatably provided at the upper frame350. The upper roller360may roll while being firmly pressed against the inner diameter surface of the guide rail125. The upper roller360is provided to prevent the upper frame350from being directly in contact with the inner diameter surface of the guide rail125. When the pinion gear340is engaged with the rack gear125a, the upper roller360prevents an elastic force, provided by the elastic body390, from being concentrated on the pinion gear340. It is desired that a plurality of upper rollers360are provided.

The lower frame370forms a lower frame of the balancing unit300. The lower frame370is disposed on an outer diameter surface of the guide rail125. The outer diameter surface of the guide rail125refers to a surface that faces the inner diameter surface on the inner side of the guide rail125. The lower frame370is formed in an arc shape so as to move along the guide rail125. The lower frame370includes a lower roller380.

The lower roller380is rotatably provided at the lower frame370. The lower roller380may roll while being firmly pressed against the outer diameter surface of the guide rail125. The lower roller380is provided to prevent the lower frame370from being directly in contact with the outer diameter surface of the guide rail125. It is desired that a plurality of lower rollers380are provided.

FIG. 7is a block diagram illustrating a washing machine according to an embodiment of the present disclosure. The washing machine according to an embodiment includes: a power supply210which is connected with an external power source to provide power; and a wireless power transmitter200which wirelessly transmits power to the balancing unit300, in which the wireless power transmitter200includes: the aforementioned transmission coil240which generates a wireless power signal to wirelessly transmit power to the balancing unit300; a transmission converter230which applies power at a predetermined driving frequency to the transmission coil240; a voltage measurer250which measures a transmission voltage which is a voltage of the transmission coil240; and a transmission controller220which controls the transmission converter230based on the transmission voltage measured by the voltage measurer250.

The power supply210converts commercial electric power, which is an alternating current supplied from an external power source, into a direct current, and supplies the direct current to the transmission converter230. It is desired that the power supply210is provided in the cabinet111or at the control panel114. The power supplied after conversion by the power supply210may also be supplied to the drum motor113.

The transmission converter230converts the direct current, supplied from the power supply210, into an alternating current (AC) waveform. The transmission converter230includes a switching device which converts the direct current (DC) into the alternating current (AC), and a driving frequency of the switching device is set by the transmission controller220. The alternating current (AC) may drive the transmission coil240to form a magnetic field around the transmission coil240.

As described above, the transmission coil240is disposed at the tub122and generates a wireless power signal which is a magnetic field. The transmission coil240is connected with a transmitting capacitor (not shown) to form a resonance circuit. As the alternating current (AC) flows to the transmission coil240, a wireless power signal, which is a magnetic field, is generated according to a change in current.

The voltage measurer250measures a voltage of the transmission coil240. The voltage measurer250may capture a voltage from the transmission coil240by using a capacitor, and may measure the voltage by using an Analog to Digital Converter (ADC). The voltage measurer250may transmit a transmission voltage, which is the measured voltage, to the transmission controller220.

The transmission controller220controls the transmission converter230based on the transmission voltage measured by the voltage measurer250. The transmission controller220controls a driving frequency of the transmission converter230based on the transmission voltage measured by the voltage measurer250. Further, the transmission controller220may control an output voltage or current of the transmission converter230. The transmission controller220will be described in detail later with reference toFIG. 8.

The washing machine according to an embodiment of the present disclosure includes: the aforementioned reception coil310which generates power by receiving a wireless power signal; a rectifier321which converts power, generated by the reception coil310, from an alternating current to a direct current; and a charging capacitor322which charges the power converted by the rectifier321.

As described above, the reception coil310generates power by electromagnetic induction by receiving a wireless power signal which is a magnetic field generated by the transmission coil240. The reception coil310is connected with a receiving capacitor (not shown) to form a resonance circuit. When the balancing unit300passes the transmission coil240, the reception coil310receives the wireless power signal, generated by the transmission coil240, to generate power having an AC waveform.

The rectifier321converts power, generated by the receiving coil310, from an alternating current to a direct current. The rectifier321may include a smoother which makes the rectified current a smooth and stable current.

The charging capacitor322may temporarily charge power supplied from the rectifier321. As the balancing unit300may not include an electric condenser due to the limitations on size and weight, such that the charging capacitor322may charge power by using a capacitor and may supply the power to the driving module330.

The aforementioned rectifier321and the charging capacitor322are included in the electronic component module320.

FIG. 8is a flowchart illustrating a method of controlling a washing machine according to an embodiment of the present disclosure.

As the reception coil310of the balancing unit300rotates with the drum124, the reception coil310and the transmission coil240meet only for a very short period of time to receive power wirelessly. Further, the balancing unit300temporarily stores the wirelessly received power in the charging capacitor322having a small power capacity, such that the wireless power transmitter200is required to transmit sufficient power in a very short period of time. However, unlike general wireless power transmission, the wireless power transmitter200and the balancing unit300of the present disclosure do not communicate with each other, such that the balancing unit300may not transfer the transmitted power or generated voltage to the wireless power transmitter200. Accordingly, the wireless power transmitter200is required to transmit power enough to drive the driving module330of the balancing unit300in a very short transmission time of several ms without knowing the power transmitted to the balancing unit300or the generated voltage. Furthermore, while the wireless power transmitter200continuously generates a wireless power signal, the balancing unit300receives the generated power signal only during a short period of time, such that in the case where an excessive amount of power is transmitted, there is a concern that the transmitting capacitor, the receiving capacitor, or the charging capacitor322may be damaged by fire. Accordingly, the inventors of the present disclosure have conducted research to provide a method of controlling the wireless power transmitter200by considering safety and a transmission time of the wireless power transmitter200and power for driving the driving module330.

A transmission resonance frequency (Fxt), which is a resonance frequency of a transmitting-side resonance circuit formed by the transmission coil240, is determined by a capacity of the transmission coil240and a capacity of a capacitor. Further, a reception resonance frequency (Frx), which is a resonance frequency of a receiving-side resonance circuit formed by the reception coil310, is determined by a capacity of the reception coil310and a capacity of a capacitor. The driving frequency (Fop) of the transmission converter230is set by the transmission controller220. The driving frequency (Fop) has the following relationship with the transmission resonance frequency (Ftx) and the reception resonance frequency (Frx).
Ftx<Fop<Frx

As described above, it is required to transmit power enough to drive the driving module330of the balancing unit300. Power supplied from the rectifier321has a proportional relationship with the rectified voltage which is a voltage output by the rectifier321. Experiments showed that as the driving frequency (Fop) becomes closer to the reception resonance frequency (Frx), the rectified voltage of the rectifier321is increased. That is, as the driving frequency (Fop) is approximate to the reception resonance frequency (Frx), power supplied by the rectifier321is increased.

As described above, power should be transmitted wirelessly during a short transmission time when the reception coil310and the transmission coil240meet each other. Experiments showed that as the driving frequency (Fop) becomes closer to the transmission resonance frequency (Ftx), a transmission time is shortened.

Further, as described above, it is required to limit power transmission to prevent capacitors from being damaged by fire.

As shown in experiments, a coil current, which is a current flowing in the transmission coil, has a predetermined range to satisfy the above requirements. That is, it is desired that the coil current is in a range between a minimum current and a maximum current. Further, it has been confirmed through experiment that between the set transmission resonance frequency (Ftx) and reception resonance frequency (Frx), the coil current is increased as the driving frequency (Fop) is increased; and the coil current is decreased as the driving frequency (Fop) is decreased.

Accordingly, by increasing the driving frequency (Fop) if the coil current at the set transmission resonance frequency (Ftx) and reception resonance frequency (Frx) is equal to or less than a minimum current; and by reducing the driving frequency (Fop) if the coil current is equal to or higher than a maximum current, sufficient power may be transmitted in a short transmission time, and electronic components may be prevented from being damaged by fire.

Measuring the coil current is a matter of concern, but experiments showed that a transmission voltage measured by a voltage measurer250is proportional to the transmission coil in a linear relation. Accordingly, by converting the transmission voltage measured by the voltage measurer250into a coil current by using the linear relation, the driving frequency (Fop) may be changed according to the coil current.

The above description will be described below as a controlling method with reference toFIG. 8.

The wireless power transmitter200generates a wireless power signal at the set driving frequency (Fop) in S11. The transmission converter230of the wireless power transmitter200converts a direct current, supplied from the power supply210, to an alternating current having a set driving frequency (Fop), and applies the alternating current to the transmission coil240. The transmission coil240generates a wireless power signal, which is a magnetic field, in response to input of the alternating current from the transmission converter230. The balancing unit300receives power wirelessly by receiving the generated wireless power signal.

The driving frequency (Fop) is set by the transmission controller220; and it is desired that the initial driving frequency (Fop) is set to a median value between the transmission resonance frequency (Ftx), which is determined by the capacity of the transmission coil240of the transmitting-side resonance circuit and the capacity of a capacitor, and the reception resonance frequency (Frx) which is determined by the capacity of the reception coil310of the receiving-side resonance circuit and the capacity of a capacitor.

The wireless power transmitter200measures a transmission voltage in S12. The voltage measurer250of the wireless power transmitter200captures a voltage from the transmission coil240by using a capacitor, and measures a voltage by using an Analog to Digital Converter (ADC). The voltage measurer250transfers the transmission voltage, which is the measured voltage, to the transmission controller220.

The wireless power transmitter200calculates a coil current from the transmission voltage in S13. The transmission controller220of the wireless power transmitter200converts the transmission voltage, which is transferred from the voltage measurer250, to a coil current by using a predetermined linear relation.

The wireless power transmitter200determines whether the coil current is in a range between a predetermined minimum current and a predetermined maximum current in S14. The transmission controller220of the wireless power transmitter200determines whether the calculated coil current exceeds the predetermined minimum current and is below the predetermined maximum current. In the case where the calculated coil current is in a range between the predetermined minimum current and the predetermined maximum current, the wireless power transmitter200continues to measure the transmission voltage in S12.

In the case where the coil current is equal to or less than predetermined minimum current or is equal to or higher than the predetermined maximum current, the wireless power transmitter200changes the driving frequency (Fop) in S15. In response to the calculated coil current being equal to or less than the predetermined minimum current, the transmission controller220of the wireless power transmitter200increases the driving frequency (Fop); and in response to the calculated coil current being equal to or higher than the predetermined maximum current, the transmission controller220of the wireless power transmitter200decreases the driving frequency (Fop).

The wireless power transmitter200generates a wireless power signal at the changed driving frequency (Fop) in S16The transmission converter230of the wireless power transmitter200converts a direct current, supplied from the power supply210, to an alternating current having the changed driving frequency (Fop), and applies the alternating current to the transmission coil240; and the transmission coil240generates a wireless power signal, which is a magnetic field, in response to the input of the alternating current from the transmission converter230. The balancing unit300receives power wirelessly by receiving the generated wireless power signal.

While the present disclosure has been shown and described with reference to the exemplary embodiments thereof, it should be understood that the present disclosure is not limited to the specific embodiments, and various modifications and variations may be made by those skilled in the art without departing from the scope and spirit of the invention as defined by the appended claims, and the modified implementations should not be construed independently of the technical idea or prospect of the present disclosure.

EXPLANATION OF REFERENCE NUMERALS