JP2000277361A - Transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transformer exhibiting a high step-up ratio and superior conversion efficiency without causing magnetic flux to interlink with the transmission lines. SOLUTION: This transformer comprises at least a core 4 having dielectric and magnetic properties, and a transmission line 41 formed on the core 4. The line length of the line 41 is set to a value substantially equal to 1/4 the wavelength of the frequency of a voltage applied to the line 41, and a magnetic path for passing a magnetic flux generated by the line 41 is formed on the core 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer which can be suitably used for a backlight inverter or the like of a liquid crystal display device.

[0002]

2. Description of the Related Art It is generally known that a backlight inverter of a liquid crystal display device is provided with a step-up transformer. As a step-up transformer used for such an application, a winding transformer has been conventionally used.
This winding transformer is connected to a cold cathode tube via a ballast capacitor. Mercury is sealed in this cold cathode tube, and electrons generated by application of a high voltage collide with the mercury to generate ultraviolet rays, and the ultraviolet rays apply to the phosphor applied to the inside of the tube. Excitation light is emitted and converted into visible light. Such a cold-cathode tube requires a high voltage to be applied to generate electrons at the time of starting. However, once the discharge is started, the voltage for maintaining the discharge is about 1/3 of the starting voltage. I'm done. At this time, it is sufficient to supply a current of about 5 to 6 mA to the cold cathode tube, and a large current is not required. Therefore, a desired characteristic of the step-up transformer used for such an application is that the output voltage can be instantaneously increased at the start of the discharge of the cold cathode tube, and can be lowered to the discharge maintaining voltage in a steady state.

In recent years, demands for smaller, lighter, and higher performance liquid crystal display devices have been increasing. To satisfy such demands, the backlight inverter has been reduced in size, thickness, and conversion efficiency. There is a strong demand for efficiency. However, in the conventional inverter, there is a problem that the conversion efficiency is reduced when an attempt is made to reduce the thickness using a winding transformer. The reason for this is that if the shape of the core is made flat in order to make the winding transformer thinner, the winding becomes longer and the DC resistance increases. Further, when a winding transformer is used, the installation area becomes large, and there is a restriction on miniaturization.

Therefore, a backlight inverter having a piezoelectric transformer formed of a flat ceramic element in place of the winding transformer has been considered. This piezoelectric transformer can be made thinner while maintaining high conversion efficiency.
Since the step-up ratio is insufficient, a winding transformer may be used as an auxiliary transformer, and there has been a limitation in reducing the thickness. In addition, since the step-up ratio and the resonance frequency of the piezoelectric transformer are determined by the shape of the element and the electromechanical coupling coefficient, when the size of the element is reduced, the resonance frequency shifts to a higher frequency side and the step-up ratio also decreases. However, the size of the element cannot be reduced so much that the installation area becomes large as in the case of the winding transformer, which limits the miniaturization of the inverter. Further, in order to achieve both a high step-up ratio and a high conversion efficiency in the piezoelectric transformer, it is necessary to form a laminated structure or a rectangular shape having a long side of 20 to 30 mm, which makes the structure relatively complicated.

On the other hand, as a transformer to which the impedance conversion function is applied, there has been an example in which a high-frequency coaxial cable is used as a distributed constant line for a lighting device of a discharge lamp, and the high-frequency coaxial cable is used as a voltage converter. It has been reported. As the insulator of the coaxial cable, polyethylene (ε = 2.3) or Teflon (ε = 2.1) is usually used, depending on the frequency used.

However, in the conventional transformer, the dielectric constant of the insulator of the coaxial cable is low, for example, 1 MHz.
In order to use at about 60 kHz, the length of the coaxial cable should be about 49 m, especially when used as a backlight inverter of a liquid crystal display device. It was necessary to be 884 m, and miniaturization was difficult.

The inventors of the present invention have previously filed a patent application for a transformer that can be made smaller than a conventional transformer on September 3, 1998 as Japanese Patent Application No. 10-250083.
An example of this transformer is shown in FIGS. This transformer comprises a pair of plate-like cores 64, 6 having dielectric and magnetic properties.
A voltage conversion section 82 having a spiral transmission line 71 sandwiched therebetween and ground conductors 72 formed outside the pair of cores 64, 64, and a cold cathode tube (load device) 90.
It is provided with. A cold cathode tube (load device) 9 is connected to an output-side (receiving end) terminal 71 a of the transmission line 71.
0 is connected, and a switch circuit 95 connected to an AC power supply (not shown) is connected to a terminal 71b on the input side (sending end side).
Is connected. A cold cathode tube 90 is connected to an output terminal of one ground conductor 72, and a switch circuit 95 connected to the AC power supply is connected to an input terminal.
Is connected. In addition, one ground conductor 72 and the other ground conductor 72 are connected to the connecting conductor 9 in order to make the same potential.
8 are electrically connected.

Reference numerals 101 and 102 denote an adhesive layer for adhering the core 64 to the ground conductor 72, reference numerals 103 and 106 denote an insulating layer for insulating the transmission line 71 from the core, and reference numeral 104.
Is an adhesive layer for bonding the insulating layer 103 and the core 64;
Reference numeral 5 denotes an adhesive layer for bonding the insulating layer 103 and the transmission line 71, and reference numeral 107 denotes an adhesive layer for bonding the insulating layer 106 and the core 64, respectively.

In the transformer having this structure, since the propagation wavelength at the operating frequency is determined by the magnetic permeability and the dielectric constant of the core, the transmission line length can be reduced by using a core made of a material having a high magnetic permeability and a high dielectric constant. The transformer can be shortened, and the size of the transformer can be reduced.

[0010]

However, in the above transformer, since the plate-shaped cores 64, 64 are opposed to each other with the transmission line 71 interposed therebetween, the abutting surfaces of the cores 64, 64 form a magnetic gap. There is a problem that the magnetic flux generated by the alternating current applied to the transmission line 71 acting on the transmission line 71 interlinks with the transmission line 71 in another portion, thereby increasing the copper loss and decreasing the conversion efficiency.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a transformer having a high step-up ratio and a high conversion efficiency without magnetic flux interlinking a transmission line. The purpose is to provide.

[0012]

In order to achieve the above object, the present invention employs the following constitution. A transformer according to the present invention includes at least a core having dielectric properties and magnetism, and a transmission line formed on the core, and a line length L of the transmission line is determined by a frequency of a voltage applied to the transmission line. 1 /
The wavelength is set to be approximately equal to four wavelengths, and a magnetic path is formed in the core for passing a magnetic flux generated from the transmission line. According to this transformer, since the magnetic path through which the magnetic flux passes is formed in the core, the generated magnetic flux does not link to the transmission line, so that the copper loss is reduced and the conversion efficiency can be increased.

[0013] Further, according to the transformer of the present invention, in the transformer described above, the core is formed by a pair of plate-shaped core halves abutting each other, and the line conductor of the transmission line is formed by the pair of plate conductors. A ground conductor disposed on the surface of the at least one core half opposite to the butting surface of the at least one core half, and a peripheral portion of the transmission line of at least one core half; A magnetic path forming portion that forms the magnetic path, wherein the transmission line is separated from the one of the core halves by the magnetic path forming portion. According to such a transformer, most of the magnetic flux generated from the transmission line passes through the magnetic path, and the transmission line and the core are separated from each other. And the conversion efficiency can be increased.

Further, the transformer according to the present invention is the above-described transformer, wherein a central convex portion is provided at a central portion of a mating surface of at least one core half, and at least a peripheral portion of the mating surface is provided. A peripheral convex portion is provided in a part, and the magnetic path forming portion is formed by abutting the central convex portion and the peripheral convex portion of the one core half on the other core half. The path is constituted by the pair of core halves, the central convex portion, and the peripheral convex portion, and the transmission line includes:
It is characterized by being arranged in the magnetic path forming part and being surrounded by the magnetic path. According to such a transformer, the magnetic flux generated from the transmission line can be concentrated on the central convex portion and the peripheral convex portion, and the cross-linking magnetic flux component linked to the transmission line can be reduced to reduce the copper loss. Can be increased.

Further, the transformer according to the present invention is the transformer described above, wherein the peripheral convex portion is provided on the entire peripheral portion of the core half. According to this transformer, since the peripheral convex portion is provided on the entire peripheral portion, the magnetic path forming portion on which the transmission line is disposed can be completely surrounded by the peripheral convex portion. As a result, it is possible to further reduce the transducing magnetic flux interlinking and reduce the copper loss, so that the conversion efficiency of the transformer can be further increased.

Further, the transformer according to the present invention is the transformer described above, wherein the transmission line is wound around the central convex portion and disposed in the magnetic path forming portion. And In such a transformer, since the transmission line is configured to be wound around the central convex portion, the generated magnetic flux can be concentrated on the central convex portion and the peripheral convex portion, and the cross link to the transmission line can be achieved. Since the copper loss can be reduced by reducing the magnetic flux component, the conversion efficiency can be increased.

Even if the magnetic path forming portion is provided on the one half of the core, the distance between the wound transmission lines and the distance between the ground conductors can be kept constant. There is no adverse effect on transformer characteristics (transformer characteristics) caused by the formation. Therefore, according to the present invention, a loss can be sufficiently reduced without changing the characteristics of the transformer, and a converter with higher conversion efficiency can be provided.

Further, in the transformer according to the present invention, the magnetic path forming portion may be filled with a non-magnetic material. According to the transformer having such a configuration, even when the magnetic path forming portion is formed in the core half, the core half is reinforced by the non-magnetic material filled in the magnetic path forming portion, and the mechanical strength of the transformer is improved. Can be improved.

The transformer of the present invention is the above-described transformer, wherein the core is Mn-Zn ferrite, Ni-
It is characterized by being composed of one or more selected from the group consisting of Zn ferrite and Ni-Cu ferrite. According to such a transformer, the size of the core can be reduced, and the size can be reduced. Further, in the transformer according to the present invention, the core may be selected from the group consisting of Fe, Co, and Ni.
A species or two or more elements T, Hf, Zr, W, Ti,
V, Nb, Mo, Cr, Mg, Mn, Al, Si, C
a, Sr, Ba, Cu, Ga, Ge, As, Se, Z
one or more elements M selected from the group consisting of n, Cd, In, Sn, Sb, Te, Pb, Bi, and rare earth elements;
It may be composed of a soft magnetic alloy powder containing one or more elements D selected from the group consisting of O, C, N and B, and a synthetic resin. According to such a transformer, the magnetic permeability and the dielectric constant of the core can be increased, the effect of shortening the wavelength becomes sufficient, and the size can be reduced.

Further, the transformer according to the present invention is the above-described transformer, wherein the core has an effective magnetic permeability μ at 100 kHz of 10 to 20,000 and an effective dielectric constant ε of 10 to 20,000.
5,000. According to such a transformer, the magnetic permeability and the dielectric constant of the core are large, the transmission line length is shortened, the dimension of the core can be shortened, and the size can be reduced.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the transformer according to the present invention will be described below. In the embodiment described below, a case where the transformer of the present invention is applied to a backlight inverter of a liquid crystal display device will be described. FIG. 1 is a perspective view showing a main part of a transformer according to a first embodiment of the present invention, and FIG. 2 is a sectional view of the transformer. As shown in FIG. 2, the transformer 1 is generally composed of a voltage converter 2 and a cold cathode tube 36 as a load device.

The voltage conversion section 2 includes a spiral transmission line 41 between a pair of core halves 4a and 4b constituting the core 4.
And ground conductors 42, 42 are formed outside the pair of core halves 4a, 4b. The core 4 has dielectric properties and magnetism. As the material forming the core 4, it is possible to shorten the dimension of the core 4 by using one or two or more selected from the group of Mn-Zn ferrite, Ni-Zn ferrite, Ni-Cu ferrite, This is preferable in that the transformer 1 can be reduced in size. The grounding conductors 42, 42 are formed by a pair of core halves 4a, 4b.
Are provided on the respective surfaces opposite to the respective butting surfaces. The ground conductors 42, 42 are connected to the core halves 4a, 4b.
An adhesive layer 101 on the entire surface on the opposite side of each butting surface of
Although the thin film is provided through the intermediary of the thin film 102, the thin film is not limited to the thin film and may be a coil.

The core 4 preferably has an effective magnetic permeability μ at 100 kHz of 10 to 20,000.
The core 4 preferably has an effective dielectric constant ε of 10 to 5000. The core 4 is made of 2 selected from the ferrite group.
There may be a laminated structure such as a case of more than one kind,
In this case, the effective magnetic permeability and the effective permittivity are values when the laminated structure is regarded as a continuous medium. The wavelength shortening effect increases as the effective magnetic permeability μ and the effective permittivity ε of the core 4 increase, so that the transformer 1 can be downsized. However, the characteristic impedance of the transmission line increases as the effective magnetic permeability μ increases, but decreases as the effective permittivity ε increases. Therefore, there is an optimal range for μ and ε. Therefore, in the present invention, in order to increase the wavelength shortening effect and to set the characteristic impedance to a predetermined value, it is preferable that μ and ε of the core 4 are within the above ranges.

As shown in FIGS. 1 and 2, a center convex portion 4c is provided at the center of the abutting surface 4f of the core half body 4a, and a part of a peripheral portion 4d of the abutting surface 4f has
Peripheral protrusions 4e, 4e are provided. Peripheral convex portion 4e,
4e are provided facing each other on the butting surface 4f. Such a central convex portion 4c and a peripheral convex portion 4e,
4e is a method of cutting one surface of a plate-shaped core block with a grindstone or the like so as to leave the central convex portion 4c and the peripheral convex portions 4e and 4e, or a method in which the plate-shaped core block is It can be formed by a method of putting, pressing, and forming the central convex portion 4c and the peripheral convex portions 4e, 4e on one surface of the plate-shaped core block. The core half 4b has a plate shape. Then, the central convex portion 4c and the peripheral convex portions 4e, 4e of the core half 4a abut against the core half 4b to form the core 4, and a pair of core halves 4a, An air gap 7a is formed by being divided into a projection 4b, a central projection 4c, and peripheral projections 4e, 4e. The air gap 7a forms the magnetic path forming section 7.
The pair of core halves 4a and 4b and the central convex portion 4
A magnetic path surrounding the magnetic path forming part 7 is constituted by c and the peripheral protrusions 4e, 4e.

Next, as shown in FIGS. 1 and 2, the transmission line 41 is made of a line conductor and has a central convex portion 4c.
And is disposed in the magnetic path forming portion 7 at a distance from the core half 4a. As a method of providing such a transmission line 41 in the magnetic path forming portion 7, for example, a method of using a general coated copper wire and storing the coated conductive wire in the magnetic path forming portion 7, or a method of providing the core half 4b A spiral conductor is formed on the upper surface of the substrate by plating or sputtering, and the core halves 4a are abutted with each other. Thus, the transmission line 41 is disposed in the magnetic path forming section 7 and is surrounded by the magnetic path.

As shown in FIG. 2, an adhesive layer 103 is laminated on the core half 4b, and an insulating layer 104 made of polyimide or the like is laminated on a part of the adhesive layer 103. Are formed, and the transmission line 41 and the core half 4b are insulated. An insulating layer 105 made of polyimide or the like is laminated on the transmission line 41 with an adhesive layer 106 interposed therebetween.

In this transformer 1, the direction of the magnetic flux generated from the transmission line 41 interposed between the pair of core halves 4a and 4b as described above is shown in FIG. been when a street sign I _a in FIG. 2,
The direction of the arrow indicated by _Ib is set. Therefore, most of the magnetic flux generated from the transmission line is a pair of core halves 4a,
4b, the central convex portion 4c, and the peripheral convex portions 4e, 4e. The magnetic flux generated from the transmission line is concentrated on the central convex portion 4c and the peripheral convex portions 4e and 4e, and the crossover magnetic flux component does not link with the transmission line 41, so that the copper loss can be reduced. Conversion efficiency can be increased.

A cold cathode tube 36 is connected to an output (reception end) terminal 41a of the transmission line 41, and an AC power supply (not shown) is connected to an input (transmission end) terminal 41b. ) Is connected to the switch circuit 35. Also,
The output terminal of the other ground conductor 42 has a cold cathode tube 36
Is connected, and a switch circuit 35 connected to the AC power supply is connected to the input side terminal. Also,
The ground conductors 42 are electrically connected to each other by a connection conductor 43 so as to make the same potential.

It is preferable that each line length L of the transmission line 41 and the ground conductors 42, 42 is substantially equal to １ ／ wavelength of the frequency (operating frequency) of the AC voltage applied to these conductors.
If the line lengths L of the transmission line 41 and the ground conductors 42 and 42 are different from １ ／ wavelength of the frequency (operating frequency) of the AC voltage, the cold cathode tube 36 having an impedance larger than the intrinsic impedance of the voltage conversion unit 2 will When connected,
Voltage conversion is not performed, which is not preferable.

As the cold cathode tube 36, one having an impedance different from the specific impedance of the voltage converter 2 having the above-described configuration is used. This is preferable in that a voltage different from the input voltage is applied at a corresponding magnification. Further, the cold cathode tube 36 having an impedance larger than the intrinsic impedance of the voltage converter 2 is used.
This is more preferable in that a voltage higher than the input voltage is applied to both ends of the load at a magnification corresponding to the ratio of the impedance to the inherent impedance of the voltage converter 2. In this transformer 1, the parasitic capacitance (distribution constant)
Core 4 having dielectric and magnetic properties
And a distributed constant circuit as shown in FIG. 3 using the transmission line 41 and the ground conductors 42, 42. In FIG. 3, reference symbol V ₁ denotes an input voltage, V ₂ denotes a receiving end voltage, I ₁ denotes an input current, I ₂
Is the receiving end current, Z ₁ is the impedance seen from the input side, Z ₂
Is the impedance seen from the output side, and Z ₀ is the transmission line 41
, L is the line length of the transmission line 41. The distributed constant circuit shown in FIG. 3 is represented by the following equation (1). In the equation (1), β is a propagation constant of the transmission line 41 (β = 2πf / v = 2π / λ... (1-a)). In the equation (1-a), v is a propagation speed (= fλ), and λ is a propagation wavelength.

[0031]

(Equation 1)

In this embodiment, since the line length L of the transmission line 41 is set to λ / 4 of the operating frequency, βL = (2π / λ) × (λ / 4) = π / 2. Therefore, equation (1) can be expressed by equation (4) below.

[0033]

(Equation 2)

By transforming the above equation (4) and obtaining the impedance Z ₁ as viewed from the input side, Z ₁ = V ₁ / I ₁ = (jZ ₀ · I ₂ ) / ((j / Z ₀ ) · V ₂ ) (5) Here, since V ₂ = Z ₂ · I ₂ , Z ₁ = Z ₀ / (Z ₂ / Z ₀ ) = Z ₀ ² / Z ₂ Equation (6) Is, when propagation wavelength / 4 = line length,
When an impedance of 100 ohms is connected to the output terminal of the line having a specific impedance of 50 ohms, it looks like 25 ohms when viewed from the input side.
Impedance Z ₂ which are connected to the power receiving end, appears to be converted to Z ₁ from the sending end. Therefore, impedance conversion is performed.

From the above equation (4), From the above, it is understood that the voltage is proportional to the current at the other end, and the current is proportional to the voltage at the other end. Only when the line length L is the propagation wavelength / 4, the above-mentioned relations hold and voltage conversion is performed. Thus, the inherent impedance of the transmission line 41 and the load resistance (the resistance of the load device)
The transformer 1 is suitable for the impedance characteristics of a cold-cathode tube in which a high resistance is required at the time of start-up requiring a high voltage and a resistance is reduced at the time of lighting.

Next, the operation of the transformer 1 will be described with reference to the above equations (6) and (7) and FIG. FIG.
5 is a graph for explaining the boosting action of the transmission line of the transformer 1. In the graph of FIG. 4, the horizontal axis represents the ratio of the impedance Z ₂ seen from the output side to the specific impedance Z ₀ of the transmission line 41. Here, it is assumed that the input voltage V ₁ is a constant voltage. When the load impedance Z ₂ is equal to the inherent impedance Z ₀ of the transmission line 41 (Z ₂ /
Z ₀ = 1), the transmission line 41 is in a matching state,
It is clear that the voltages at the sending end and the receiving end are equal as shown at point A in the figure. When a load of Z ₂ > Z ₀ is connected (Z ₂ / Z ₀ > 1), Z ₁ <Z ₀ from the above equation (6), and the input current I ₁ increases. Further, from the above equation (7), since the reception terminal voltage V ₂ is proportional to the input voltage I _1, also increases as shown in Figure B point. In the region of Z ₂ > Z ₀ ,
V ₂ will be being boosted is larger than V _1. Therefore, when a load greater than the inherent impedance of the transmission line 41 is connected as a load on the transmission line 41 having a line length L of 動作 wavelength of the operating frequency, the ratio between the load and the inherent impedance of the transmission line 41 at both ends of the load. A voltage higher than the input voltage is applied at a magnification according to.

Next, the reason why the wavelength can be shortened by using the core 4 in the transformer 1 and the transformer 1 can be downsized will be described. The wavelength in free space is represented by the following equation (8). λ = v / f (8) If the permittivity / permeability of the portion of the voltage converter 2 where the electromagnetic field is generated is large, the traveling speed v of the traveling wave decreases. This propagation speed v is represented by the following equation (9). v [m / s] = 3 × 10 ⁸ × (ε ^1/2 · μ ^1/2 ) ⁻¹ (9) Accordingly, the wavelength in that case is represented by the following equation (10). λ = (v / f) · (ε ^1/2 · μ ^1/2 ) ^-1 (10) As is apparent from the above equation (10), the wavelength can be shortened according to the values of the permittivity and the magnetic permeability. As the dielectric constant and magnetic permeability increase, the wavelength decreases accordingly. Therefore, by forming the core 4 from a material having a large dielectric constant and magnetic permeability, the wavelength can be shortened and the core size can be reduced. The transformer 1 can be shortened, and the transformer 1 can be downsized.

In the above-described transformer 1, a spiral transmission line 41 is sandwiched between a pair of core halves 4a and 4b having dielectric properties and magnetism, and a pair of core halves 4a and 4b
The voltage conversion unit 2 having the ground conductors 42 and 42 formed outside thereof and the cold cathode tube (load device) 36 having an impedance different from the intrinsic impedance of the voltage conversion unit 2 are provided, so that the wavelength can be shortened. Thus, since the core size can be reduced, the installation area can be reduced, and the transformer 1 can be downsized while maintaining a high step-up ratio and high conversion efficiency. Further, since a high step-up ratio and high conversion efficiency can be achieved at the same time without using an auxiliary transformer such as a winding transformer, the inverter can be made thinner than a piezoelectric transformer using the auxiliary transformer. Further, the transmission line 41 is provided between the pair of core halves 4a and 4b having dielectric properties and magnetism, and the ground conductors 42 and 42 are provided outside the pair of core halves 4a and 4b. High conversion efficiency can be achieved, and the structure can be simplified.

In the transformer 1 described above, one or two or more elements T selected from the group consisting of Fe, Co, and Ni, and Hf, Zr, W, Ti, V, N
b, Mo, Cr, Mg, Mn, Al, Si, Ca, S
r, Ba, Cu, Ga, Ge, As, Se, Zn, C
d, In, Sn, Sb, Te, Pb, Bi, one or two or more elements M selected from the group of rare earth elements;
One or more elements D selected from the group consisting of C, N and B
It is preferable to use a soft magnetic alloy powder containing the same and a synthetic resin in that the magnetic permeability and the dielectric constant of the core 4 can be increased, the wavelength shortening effect becomes sufficient, and the transformer 1 can be downsized.

As the soft magnetic alloy powder, for example, those represented by the following composition formula are preferably used. T _a M _b D _c (where T represents one or more elements selected from the group consisting of Fe, Co, and Ni, and M represents Hf, Zr,
W, Ti, V, Nb, Mo, Cr, Mg, Mn, Al,
Si, Ca, Sr, Ba, Cu, Ga, Ge, As, S
e, Zn, Cd, In, Sn, Sb, Te, Pb, B
i represents one or more elements selected from the group of rare earth elements, and D represents one or more elements selected from the group of O, C, N, and B. In the composition formulas, a, b, and c, which indicate composition ratios, are atomic%, and 40 ≦ a <87, 0 <
It satisfies the relationship of b ≦ 20 and 0 <c ≦ 50. )

As the above synthetic resin, a material having a small dielectric loss (that is, a material having a large Q and a Q of 400 or more) is used, and examples thereof include polypropylene, polyethylene, polystyrene, paraffin, polytetrafluoroethylene, polycarbonate, and silicone. Resins.

The core 4 made of a soft magnetic alloy powder and a synthetic resin as described above can be manufactured, for example, as follows. First, to obtain the composition of the soft magnetic alloy powder composition formula represented by T _a M _b D _c Weigh the raw materials. As the raw material here, T powder and M powder are used. As the T powder, a powder selected from at least one element selected from the group consisting of Fe, Co, and Ni, oxides, carbides, carbonates, nitrides, and borides is used.
As the powder of M, Hf, Zr, W, Ti, V, Nb,
Mo, Cr, Mg, Mn, Al, Si, Ca, Sr, B
a, Cu, Ga, Ge, As, Se, Zn, Cd, I
A powder selected from at least one element selected from the group consisting of n, Sn, Sb, Te, Pb, Bi, and a rare earth element, and oxides, carbides, carbonates, nitrides, and borides is used. Can be As the rare earth elements, 3 in the periodic table
Sc, Y belonging to A group, or La, Ce, Pr,
Nd, Pm, Sm, Eu, Gd, Td, Dy, Ho, E
At least one element selected from the group of lanthanoids such as r, Tm, Yb, and Lu, or a mixture thereof. At this time, the powder of T has a particle size of 100 μm or less,
It is desirable that the powder has a particle size of 2 μm or less.

Next, when adding O, C, and N of D, the above-mentioned powder of T and powder of M are sealed in a stainless steel pot together with stainless steel balls of the same material as the pot, and O is added. , C, and N are filled with a gas of at least one element selected from the group consisting of a simple gas, an oxide gas, and a carbide gas. Then, a predetermined time using a high-energy planetary ball mill, milling by stirring to mechanical alloying, the soft magnetic alloy powder composition formula represented by T _a M _b D _c is obtained. The time of mechanical alloying should be 2 hours or more, bcc structure or fcc
It is preferable because the structure or the crystal of T in which these are mixed can be sufficiently refined. The soft magnetic alloy powder obtained here has an average crystal grain size of several nm to several tens nm.
An average particle size of 1 to 2 having a structure in which a T microcrystalline phase having a cc structure is surrounded by an amorphous phase containing a large amount of M and D.
It becomes agglomerated particles of about μm. This soft magnetic alloy powder exhibits excellent soft magnetic properties because the bcc structure or fcc structure constituting the aggregated particles, or the average particle size of the fine crystal of T in which these are mixed, is excellent. Alternatively, the fcc structure, or a microcrystal of T in which these are mixed is surrounded by a high-resistance amorphous phase,
The feature is that eddy current loss can be kept small.

Next, the obtained soft magnetic alloy powder is dispersed in a synthetic resin solution using an organic solvent as a solvent to obtain a slurry.
This slurry is repeatedly passed through three rolls and kneaded until the slurry becomes powdery to obtain a kneaded material. As organic solvents for dissolving this synthetic resin, xylene, toluene,
Benzene and the like can be mentioned. The addition ratio of the soft magnetic alloy powder to the synthetic resin can be appropriately changed depending on the magnetism and dielectric properties of the target core, but is 50 to 50% by volume in the slurry.
It is preferable to add so that it may be about 80 vol%. When the volume ratio of the soft magnetic alloy powder is less than 50 vol%,
There is a possibility that the magnetic permeability may be low, while if it exceeds 80 vol%, there may be a problem that it is difficult to perform molding by injection molding or the like.

The above soft magnetic alloy powder is dispersed in a synthetic resin liquid,
Before kneading, it is desirable to perform heat treatment in an atmosphere selected from among air, oxygen, nitrogen, and water vapor or in a mixed atmosphere thereof. The heating temperature here is 25 ° C ~
The heating time is preferably about 300 ° C. and about 0.5 to 48 hours. By doing so, an insulating layer made of an oxide is formed on the surface of the soft magnetic alloy powder, so that the specific resistance of the soft magnetic alloy powder increases and the dielectric constant at high frequencies can be further reduced. Note that the insulating layer here is not limited to an oxide film and may be formed using another insulating film.

Next, the kneaded material is put into a drier or the like and heated to evaporate the organic solvent, and then molded into a desired shape using a press molding machine, an injection molding machine, an extruder or the like. Is prepared. Thereafter, the molded body is placed in the
By heating at about 400 ° C. for about 1 hour, the core 4 having the desired magnetism and dielectric properties can be obtained. Further, the core 4 made of the soft magnetic alloy powder and the synthetic resin is mixed with the T powder and the M powder and then pulverized in a D gas atmosphere.
Instead of stirring, the powder of T, the powder of M, and the powder of D are mixed, and then mixed in an inert gas atmosphere or O, C,
A simple gas of at least one element selected from the group of N,
It can also be manufactured in the same manner as in the above-described manufacturing example except that pulverization and stirring are performed in a gas atmosphere of D selected from an oxide gas and a carbide gas. As the powder of D above,
At least one or a mixture selected from carbon and B is used. In this example, the T powder, the M powder, and the D powder are pulverized and stirred under a gas atmosphere of D, an inert gas atmosphere such as Ar gas, or a mixture of the gas D and Ar gas. It is performed in a mixed gas atmosphere with an inert gas, and when performed in the mixed gas atmosphere, the amounts of oxygen, carbon, and nitrogen in the material can be adjusted.

The core 4 made of a soft magnetic alloy powder and a synthetic resin is made of a TM alloy ribbon pulverized powder obtained by a liquid quenching method in place of the T powder and the M powder. It can also be manufactured in the same manner as the manufacturing example described above. Also, a core 4 made of a soft magnetic alloy powder and a synthetic resin is used.
Is a powder of T, a powder of M, a powder of D and / or D
It can also be manufactured in the same manner as in the above-mentioned manufacturing example, except that in addition to the above-mentioned gas, a pulverized material powder of a TM alloy ribbon obtained by a liquid quenching method is used.

A synthetic resin having a small dielectric loss and a composition formula of T
By configuring the _a M _b D core 4 of soft magnetic alloy powder represented by _c, upon the resistivity of the core 4 is 10 ⁸ Ω · cm or more, a dielectric as an insulator which synthetic resin has (dielectric) The properties and the soft magnetic properties of the soft magnetic alloy powder can be combined. The above composition formula is T _a M _b
A pair of core halves 4a constructed of a soft magnetic alloy powder and a synthetic resin represented by D _c, 4b are permeability and permittivity is sufficiently large, therefore, such a pair of core halves 4a, 4
b, a spiral transmission line 41 made of a conductor is sandwiched between the pair of core halves 4a and 4b. In particular, the wavelength shortening effect is sufficient,
The core size can be shortened, and the transformer 1 can be downsized.

Next, a second embodiment of the present invention will be described. FIG. 5 is a perspective view illustrating a main part of the transformer according to the second embodiment. This transformer 10 is different from the transformer 1 shown in FIGS. 1 and 2 in that a peripheral convex portion 4h is provided on the entire peripheral portion 4d of the butting surface 4f of one core half 4g. It is. That is, the peripheral convex portion 4h is formed over the entire periphery of the substantially rectangular abutting surface 4f. The transmission line 41 is completely surrounded by the core 4 by being disposed in the magnetic path forming portion divided into the core halves 4g, 4b, the central convex portion 4c, and the peripheral convex portion 4h.

Therefore, according to the transformer 10, the following effects can be obtained in addition to the effects of the transformer 1 described above. That is, since the peripheral convex portion 4h is provided over the entire circumference of the butting surface 4f, the transmission line 41 is completely surrounded by the magnetic path, and the crossover magnetic flux component linked to the transmission line 41 can be further reduced. Since the copper loss can be reduced, the conversion efficiency of the transformer 10 can be further increased.

Next, a third embodiment of the present invention will be described. FIG. 6 is a cross-sectional view illustrating the power converter 22 of the transformer 20 according to the third embodiment. This transformer 20 corresponds to FIG.
The difference from the transformer 1 shown in FIG. 2 is that the magnetic path forming portion 7 is filled with a non-magnetic material 25. That is, the non-magnetic material 25 is formed by the transmission line 41 and the one core 4a.
Is filled in the gap 7a (the magnetic path forming portion 7) between them. Here, for example, when the magnetic path forming portion 7 is filled with a magnetic material, the magnetic flux generated from the transmission line 41 is applied to the magnetic material, the magnetic flux linked to the transmission line 41 increases, the copper loss increases, and the transformer 20 It is not preferable because the conversion efficiency decreases. As the nonmagnetic material 25, a resin, for example, a resin having a high hardness such as an epoxy resin is preferable, and it is preferable that the thermal expansion coefficient is substantially equal to that of the core 4.

According to the transformer 20, the following effects can be obtained in addition to the effects of the transformer 1 described above. That is,
Even when the magnetic path forming part 7 is formed in the core half 4a, the mechanical strength of the core half 4a is reinforced by the non-magnetic material 25 filled in the magnetic path forming part 7, and the mechanical strength of the transformer 20 is increased. Strength can be improved.

[0053]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to only these Examples. (Example 1) A transformer similar to the transformer 10 shown in FIGS. 1 and 2 was manufactured. The thickness of each of the core halves 4a and 4b made of Mn-Zn ferrite of the voltage conversion unit 2 of the transformer of Example 1 manufactured here was 0.5 mm, and the central convex portion 4c and the peripheral convex portion 4e of the core half 4a. Is 0.5 mm, the depth of the magnetic path forming portion 7 is 0.5 mm, the thickness of the spiral transmission line 41 is 0.04 mm, the width of the transmission line 41 is 0.29 mm, and the transmission line 41 is Pitch is 0.24m
m, and the thickness of the ground conductors 42, 0.04 mm. The line length L of the transmission line 41 was 1.8 m. The thickness of the insulating layer 104 is 70 μm,
Since the thickness of No. 5 was 7 μm, the distance between the insulating layer 105 and the core half 4a was about 0.39 mm.

The gain phase of the voltage converter of the transformer thus manufactured was measured. In this measurement, the termination of the gain phase (using a dedicated measurement jig) using an impedance analyzer HP4194A (trade name; manufactured by Japan Hewlett-Packard Co., Ltd.) was set to 100 kΩ, and the terminating resistance Z _L connected to the output terminal was set to 100 kΩ. went. The measurement frequency range is 0.01M so that points near resonance can be finely taken.
Hz to 10 MHz. A carbon film resistor was used for the terminating resistor Z _L. FIG. 7 shows the measurement results. Also, λ / 4
Shows the frequency f when the tuning, the value of the gain G _v below.

When Z _L = 100 kΩ, f = 0.86 MH
z, G _v = 24.3 dB

From the results shown in FIG. 7, it can be seen that the gain is maximum when the phase (phase difference between input and output voltages) is -90 (deg.). Also, the gain value is 2
It turns out that it shows a high value of 4.3 dB.

Next, the terminating resistance is set to 440Ω, 960Ω,
The conversion efficiencies when changing to 3.05 kΩ, 10.05 kΩ, and 33.05 kΩ were measured using an oscilloscope. The input voltages were 3 V, 5 V, and 7 V. The operating frequency was 860 kHz (at the time of λ / 4 tuning). FIG. 8 shows the results. As can be seen from FIG. 8, the transformer according to the first embodiment exhibits a conversion efficiency of about 92% when the terminating resistance is about 1 kΩ.

Comparative Example 1 A transformer similar to the transformer shown in FIGS. 11 and 12 was manufactured. The thickness of each of the core halves 64, 64 made of Mn-Zn ferrite of the voltage converter 2 of the transformer of Comparative Example 1 manufactured here was 0.5 mm, the thickness of the spiral transmission line 71 was 0.04 mm, and the transmission was performed. The width of the line 71 is 0.23 mm, and the pitch of the transmission line 71 is 0.3.
mm, and the thickness of the ground conductors 72 was 0.04 mm. The line length L of the transmission line 71 was 2.48 m.

The gain-phase characteristics of the voltage converter of the transformer of Comparative Example 1 were measured in the same manner as in Example 1.
FIG. 9 shows the results. Also shows the frequency f when tuned to lambda / 4, the value of the gain G _v below.

When Z _L = 100 kΩ, f = 0.4 MHz,
G _v = 18.0 dB

From the results shown in FIG. 9, when the phase (phase difference between input and output voltages) is -90 (deg.), The gain is maximum, but the value of the gain is 18.0 dB, which is It turns out that it is lower than the transformer.

Next, the conversion efficiency of the transformer of Comparative Example 1 was measured in the same manner as in Example 1. However, the input voltage is 1
V, 3 V, and 5 V. The operating frequency is 400 kHz (λ
/ 4 tuning). The results are shown in FIG. As is apparent from FIG. 10, the conversion efficiency of the transformer of Comparative Example 1 is about 77% when the termination resistance is about 700Ω, which is lower than the conversion efficiency of the transformer of Example 1. It can be seen that it is.

The reason why the gain and the conversion efficiency are higher in the transformer of the first embodiment is that the transformer of the first embodiment is provided with a magnetic flux forming part, and the transmission line and the core half are connected to each other. It is presumed that, because of the separation, the crossover magnetic flux component linked to the transmission line decreased, and the copper loss decreased.

[0064]

As described above in detail, in the transformer of the present invention, since the magnetic path for passing the magnetic flux generated from the transmission line is formed in the core, the transition magnetic flux linked to the transmission line is formed. The conversion efficiency can be increased because the components are reduced and the copper loss is reduced.

In the transformer according to the present invention, a magnetic path forming portion for forming the magnetic path is provided around the transmission line, and the transmission line is separated from the core by the magnetic path forming portion. As a result, the transition magnetic flux component interlinking the transmission line is reduced, the copper loss is reduced, and the conversion efficiency can be increased.

Further, in the transformer according to the present invention, the magnetic path forming portion is formed by being divided into the pair of core halves, the central convex portion, and the peripheral convex portion. Since the magnetic path is constituted by the pair of core halves, the central convex portion, and the peripheral convex portion, and the transmission line is disposed in the magnetic path forming portion and surrounded by the magnetic path. , Of the magnetic flux generated from the transmission line, the transition magnetic flux component moving from one core half to the other core half is concentrated on the central convex portion and the peripheral convex portion, and the transition magnetic flux component links to the transmission line. Since there is no copper loss, the conversion efficiency can be increased.

In the transformer according to the present invention, since the peripheral convex portion is provided on the entire peripheral portion, the magnetic path forming portion on which the transmission line is disposed is completely surrounded by the peripheral convex portion. This makes it possible to reduce the crossover magnetic flux linked to the transmission line and reduce the copper loss, so that the conversion efficiency of the transformer can be further increased.

In the transformer according to the present invention, the transmission line is formed by being wound around the central convex portion.
The generated magnetic flux can be concentrated on the central convex portion and the peripheral convex portion, and the transition magnetic flux component linked to the transmission line can be reduced to reduce the copper loss, so that the conversion efficiency can be improved.

Further, the core of the transformer of the present invention is Mn-
Since it is made of one or more selected from the group consisting of Zn ferrite, Ni-Zn ferrite, and Ni-Cu ferrite, the size of the core can be shortened and the transformer can be downsized. Further, in the transformer according to the present invention, the core has an effective magnetic permeability μ at 100 kHz of 10 to 20,000.
Since the effective permittivity ε is 10 to 5000, the length of the transmission line can be shortened, the dimension of the core can be shortened, and the transformer can be downsized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main part of a transformer according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the transformer according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a distributed constant circuit of the transformer according to the first embodiment.

FIG. 4 is a diagram for explaining a boosting action of a transmission line of the transformer according to the first embodiment.

FIG. 5 is a perspective view showing a main part of a transformer according to a second embodiment of the present invention.

FIG. 6 is a sectional view of a voltage converter of a transformer according to a third embodiment of the present invention.

FIG. 7 is a diagram illustrating gain-phase characteristics when the termination resistance of the transformer according to the first embodiment is 100 kΩ.

FIG. 8 is a diagram illustrating the relationship between the termination resistance and the conversion efficiency of the transformer according to the first embodiment.

FIG. 9 is a diagram showing gain-phase characteristics when the termination resistance of the transformer of Comparative Example 1 is 100 kΩ.

FIG. 10 is a diagram showing the relationship between the termination resistance and the conversion efficiency of the transformer of Comparative Example 1.

FIG. 11 is a perspective view showing a main part of a conventional transformer.

FIG. 12 is a sectional view of a transformer according to a conventional embodiment.

[Explanation of symbols]

 1, 10, 20 Transformer 4 Core 4a, 4b, 4g Core half 4c Central convex part 4d Peripheral part 4e, 4h Peripheral convex part 4f Butt surface 7 Magnetic path forming part 41 Transmission line 42 Ground conductor

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toshio Takahashi 1-7 Yukitani Otsukacho, Ota-ku, Tokyo Alps Electric Co., Ltd. F-term (reference) 5E043 BA01

Claims (7)

[Claims] A transmission line formed on the core, wherein a length of the transmission line is equal to one of a frequency of a voltage applied to the transmission line. The transformer is set to be substantially equal to 波長 wavelength, and a magnetic path for passing a magnetic flux generated from the transmission line is formed in the core. 2. The core has a pair of plate-shaped core halves abutted on each other, and a line conductor of the transmission line is disposed inside the core so as to be sandwiched between the pair of core halves. A ground conductor is arranged on a surface opposite to a mating surface of one of the core halves, and at least in a peripheral portion of the transmission line of one of the core halves,
2. The transformer according to claim 1, wherein a magnetic path forming unit that forms the magnetic path is provided, and the transmission line is separated from the one of the core halves by the magnetic path forming unit. 3. 3. A central convex portion is provided at a central portion of an abutting surface of at least one core half, and a peripheral convex portion is provided on at least a part of a peripheral portion of the abutting surface. The center convex portion and the peripheral convex portion of the one core half are formed by abutting the other core half, and the magnetic path is formed by the pair of core halves, the central convex portion, and the peripheral portion. 3. The transformer according to claim 2, wherein the transmission line includes a protrusion, and the transmission line is disposed in the magnetic path forming portion and is surrounded by the magnetic path. 4. 4. The transformer according to claim 3, wherein the peripheral convex portion is provided on the entire peripheral portion of the core half. 5. The transformer according to claim 3, wherein the transmission line is wound around the central convex portion and disposed in the magnetic path forming portion. 6. The core is made of Mn—Zn ferrite, Ni
The transformer according to any one of claims 1 to 5, wherein the transformer comprises one or more selected from the group consisting of -Zn ferrite and Ni-Cu ferrite. 7. The core has an effective magnetic permeability μ at 100 kHz of 10 to 20,000 and an effective dielectric constant ε of 10
The transformer according to any one of claims 1 to 6, wherein the number is from 5000 to 5000.