JP5755620B2 - Wireless charging stand - Google Patents

Description

  The present invention relates to a wireless charging stand that transmits electric power to a power receiver using electromagnetic induction.

In recent years, wireless charging stands that transmit power from a charging stand in a contactless manner to electronic device terminals such as mobile phones have become widespread. By generating electromagnetic induction between a power transmission coil built in the wireless charging base and a power reception coil built in a power receiver such as an electronic device terminal, power is transmitted to the power receiver in a non-contact manner. The power transmitted to the power receiving coil is supplied to a load such as a secondary battery built in the power receiver via the rectifier circuit.
Such a wireless charging base can be charged simply by placing the power receiver on the wireless charging base, and it is not necessary to connect or disconnect the power connector, so it is convenient and the power connector for charging the power receiver. There is an advantage that it is easy to obtain waterproofing and dustproofing.

  The power transmission coil of the wireless charging base is required to have a power transmission efficiency and a merit in terms of cost, and a power transmission coil in which a conductive wire with an insulation coating is wound in one layer in a spiral shape is often used. In such a power transmission coil, the outer winding terminal is drawn directly from the outer periphery of the power transmission coil, but the inner winding terminal is drawn from the power transmission coil across the power transmission coil to the outer periphery of the power transmission coil. In the thickness direction, local protrusions are generated due to the diameter of the conducting wire.

Japanese Patent Application No. 2012-026936 Japanese Patent No. 4835800 JP 2012-119596 A JP 2009-27025 A

In the wireless charging stand, a ferrite plate is placed on the side opposite to the power receiver of the power transmission coil to improve power transmission efficiency and prevent magnetic flux leakage. However, the inductance value of the power transmission coil is between the power transmission coil and the ferrite plate. Varies with distance. If the distance between the power transmission coil and the ferrite plate varies, the resonance frequency of the wireless charging base may vary, and power transmission efficiency may be reduced.
Therefore, in order to set the resonance frequency of the wireless charging base to a predetermined value, this distance must be constant.

FIG. 5 is an exploded perspective view showing a conventional wireless charging stand.
As shown in FIG. 5, in the conventional wireless charging stand, a ferrite plate 42 is disposed between the power transmission coil 30 and the circuit board 21.
The power transmission coil 30 is a planar coil in which a conductive wire covered with insulation is wound in a single layer in a spiral shape, and the inner winding terminal 31 a is drawn out to the outer periphery of the power transmission coil across the planar portion of the power transmission coil 30. .
The ferrite plate 42 is provided with a slit 91 for accommodating a protrusion formed by the winding terminal 31a. The power transmission coil 30 and the ferrite plate 42 are in close contact with the slit 91 so that the winding terminal 31a is accommodated. Is fixed. Therefore, the conventional wireless charging stand can make the distance between the power transmission coil 30 and the ferrite plate 42 constant, and can suppress variations in the resonance frequency of the wireless charging stand.

  However, the conventional wireless charging stand shown in FIG. 5 may cause eddy currents due to a slight magnetic flux leaking from the slit 91, cause noise, or damage the ferrite plate due to impact. There is a problem. Although a method of increasing the thickness of the ferrite plate 42 and making the slit 91 indented is also conceivable, a ferrite plate thicker than the diameter of the winding is necessary, so that the thickness of the wireless charging base is increased.

The wireless charging stand of the present invention includes a circuit board, a power transmission coil disposed on the lower surface of the circuit board, and a ferrite plate disposed below the power transmission coil, and the circuit board, the power transmission coil, and the ferrite. A plate is housed inside the case, the power transmission coil is fixed to the circuit board,
The ferrite plate is fixed to the bottom surface inside the case.

  In the wireless charging stand of the present invention, the circuit board, the power transmission coil, and the ferrite plate are housed inside the case, the power transmission coil is fixed to the circuit board, and the ferrite plate is fixed to the bottom surface inside the case, so that it is below the power transmission coil. Since it is arranged, it is possible to suppress a decrease in power transmission efficiency due to variations in the resonance frequency of the wireless charging stand, and to eliminate magnetic flux leakage and damage to the ferrite plate due to impact.

It is a disassembled perspective view which shows the Example of the wireless charging stand of this invention. It is sectional drawing of FIG. It is a top view which shows the example of a circuit board. It is sectional drawing which shows the example of the fixing method of a ferrite plate and a case. It is a disassembled perspective view of the conventional wireless charging stand.

Hereinafter, an embodiment of the wireless charging stand according to the present invention will be described with reference to FIGS.
FIG. 1 is an exploded perspective view showing an embodiment of the wireless charging stand of the present invention, and FIG. 2 is a cross-sectional view of FIG.
The wireless charging base 10 includes a circuit board 20, a power transmission coil 30 disposed on the lower surface of the circuit board 20, and a ferrite plate 40 made of a magnetic material disposed under the power transmission coil 30, and a lower case 50a and an upper case. It is accommodated in the case 50 consisting of 50b. The lower case 50a and the upper case 50b are connected by a support column 50c.

  The power transmission coil 30 is a planar coil in which a conductive wire with insulation coating is wound in a single layer in a spiral shape. Of the winding terminals 31 a and 31 b, the inner winding terminal 31 a crosses the flat portion of the power transmission coil 30. It is drawn out to the outer periphery of the power transmission coil 30. In order to suppress an increase in the resistance value due to the skin effect, a litz wire in which a plurality of conductive wires coated with insulating coatings are close to each other may be used as the conductive wire used for the power transmission coil.

  The power transmission coil 30 is fixed to the lower surface of the circuit board 20, and the ferrite plate 40 is fixed to the upper surface of the lower case 50a. The power transmission coil 30 is preferably fixed with an adhesive having elasticity, a double-sided tape having flexibility, or the like in order to improve impact resistance.

  By adopting such a structure, even if there is a protrusion on the lower side of the power transmission coil 30, the distance between the power transmission coil 30 and the ferrite plate 40 can be kept constant, and variations in the resonance frequency of the wireless charging base 10 can be achieved. Can be small.

  In the wireless charging stand, in order to improve the power transmission efficiency from the power transmission coil to the power receiving coil, it is necessary to accurately align the power transmission coil and the power receiving coil, for example, the position of the power receiving coil on the wireless charging stand. By arranging the position detection coil for detection, the relative position of the power transmission coil and the power reception coil is detected, and the power receiver is arranged at an appropriate position by the position display means such as LED provided on the wireless charging stand. There is a wireless charging stand that guides the user. In the case of such a wireless charging base, a position detection coil may be provided by forming a conductor pattern on the circuit board.

FIG. 3 shows an example in which a position detection coil is arranged on a circuit board.
A fan-shaped position detection coil 81 with a conductor pattern is formed at a substantially central portion of the surface of the circuit board 20, and a wireless charging base circuit and a reception detected by the position detection coil 81 are further outside the position detection coil 81. Position display means for informing the user of the position of the electric appliance and state display means for informing the state of charging are arranged.
Thus, by integrating the position detection coil and the circuit board, the wireless charging base can be thinned.

  In addition, the ferrite plate has relatively large thickness variations and warping due to sintering during manufacture. When such a ferrite plate is used, since the distance between the ferrite plate and the power transmission coil is not constant, the inductance value of the power transmission coil varies greatly, and the resonance frequency of the wireless charging base is significantly shifted. Therefore, the case must be designed in consideration of the variation of the ferrite plate. Therefore, it is common to correct the thickness variation and warpage by polishing the ferrite plate, but there is a problem that the ferrite plate becomes expensive.

FIG. 4 is a diagram for explaining an example of a method for fixing the ferrite plate 41 to the lower case 51a.
The lower case 51a is formed with a recess 110 for accommodating the ferrite plate 41.
A through hole 120 is provided on the bottom surface of the recess 110. The pin 70 is disposed in the through hole 120 of the recess 110, and the adhesive 60 is applied to the center and the outer periphery of the ferrite plate 41. The crimping plate 100 is disposed on the upper surface of the lower case 51a in which the ferrite plate 41 is accommodated in the recess 110, and the pin 70 and the crimping plate are pressed after the ferrite plate 41 is pressed against the crimping plate 100 with the pin 70 and the adhesive 60 is cured. Remove 100. In this case, even if the thickness of the ferrite plate 41 varies, the upper surface of the ferrite plate 41 can be made equal to the height of the upper surface of the lower case 51a.

  It is desirable to use three or more pins 70 in order to apply a supporting force evenly to the ferrite plate 41. Further, an elastic material such as rubber or wool may be spread instead of the pins. In this case, the through hole 120 on the bottom surface of the recess 110 is not necessary. It is desirable that the depth of the recess 110 formed in the lower case 51a can be accommodated even when the ferrite plate 41 is thick, uneven, or warped.

DESCRIPTION OF SYMBOLS 10 Wireless charging stand 20, 21 Circuit board 30 Power transmission coil 31a, 31b Winding terminal 40, 41, 42 Ferrite plate 50 Case 50a, 51a Lower case 50b Upper case 50c Support pillar 60 Adhesive 70 Pin 81 Position detection coil 91 Slit 100 Crimp plate 110 Recess 120 Through hole

Claims (4)

In the wireless charging stand that supplies power to the power receiver by electromagnetic induction,
The wireless charging stand
A plate-like upper case;
A circuit board disposed on the lower surface of the upper case ;
A power transmission coil disposed on the lower surface of the circuit board;
A ferrite plate disposed below the power transmission coil ;
A plate-like lower case disposed on the lower surface of the ferrite plate;
A recess provided on the upper surface of the lower case, deeper than the height of the ferrite plate in the height direction;
A support column connecting the lower case and the upper case ;
The upper case and the lower case are fixed by the support columns so that the distance between the lower surface of the upper case and the upper surface of the lower case is constant,
The circuit board, the power transmission coil, and the ferrite plate are housed in the upper case and the lower case, and the power transmission coil is fixed to the circuit board,
The circuit board is fixed to the lower surface of the upper case,
A wireless charging stand , wherein the ferrite plate is fixed in the recess of the lower case so that the upper surface of the ferrite plate and the upper surface of the lower case are substantially at the same height . The circuit board is provided with a position detection coil for detecting the position of the power receiving coil on the substrate surface and a display means for displaying the position of the power receiver based on the position information detected by the position detecting coil. The wireless charging stand according to claim 1. It said recess provided with a through-hole, the wireless charger according to claim 1 or claim 2 the position of the ferrite plate is adjustable by pressing and inserting the pin from the through hole. Wireless charging base of claim 1 to claim 3 sandwiched elastic member between the lower case and the ferrite plate.

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