JP2000269053A - Transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transformer which can function as a distributed constant circuit, even when line conductors are disposed at high density, be made smaller and thinner, have higher boosting rate by preventing losses due to voltage applied to a core, have a higher transformation efficiency and simplify its structure, when a transformer is provided with a voltage transducing section composed of cores having a dielectric property and magnetism, a line conductor and ground conductors constituting a transmission line and a line length (L) of the transmission line is set approximately equal to quarter of the wavelength on the transmission line with an operation frequency. SOLUTION: This transformer has a voltage transfer section 2 comprising a line conductor 41 and ground conductors 42, 42 constituting a transmission line 10, and cores 4, 4 having dielectric property and magnetism. A line length (L) of the transmission line is set approximately equal to quarter of the wavelength on the transmission line with an operation frequency. The ground conductors 42, 42 are provided between the cores 4, 4 and the line conductor 41.

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, in order to use at 1 MHz, the length of the coaxial cable needs to be about 49 m. When used as an inverter for a vehicle, the length of the coaxial cable must be about 884 m in order to use it at about 60 kHz, and it has been difficult to reduce the size.

The inventor of the present invention has proposed a transformer disclosed in Japanese Patent Application No. 10-250083 as means for solving the above-mentioned problems. This transformer obtains a high voltage by utilizing the voltage / current distribution at the time of tuning of a 1/4 wavelength transmission line terminated with a high resistance. FIG. 6 shows the structure of Japanese Patent Application No.
It is a schematic structure figure showing the example of the transformer of No. 250083.
This transformer includes a pair of cores 84 having dielectric and magnetic properties.
A transmission line 100 comprising a core 84, a spiral coil-shaped internal conductor 91 provided between the cores 84, 84, and coiled or film-shaped external conductors 92, 92 provided outside the cores 84, 84. A voltage conversion unit 102 having
It includes a cold cathode tube (load device) 120 having an impedance different from the intrinsic impedance of the voltage conversion unit 102.

The inner conductor 91 of the pair of cores 84, 84
The upper core 84 is divided right and left to take out connection terminals. Ferrite or the like is used as a material forming the pair of cores 84, 84. Internal conductor 91
An insulator 85 is interposed between the core 85 and each core 84. Adhesive layers 86 are interposed between the inner conductor 91 and the insulator 85 above the core 85, between the insulator 85 and the core 84 above the core 85, and between the core 84 and the outer conductor 92 above the core 84, respectively. ing. Also, the insulator 8 on the lower side of the internal conductor 91
Adhesive layers 86 are interposed between the core 5 and the lower core 84 and between the core 84 and the outer conductor 92 below the core 84, respectively.

The output (reception end) terminal of the internal conductor 91 is connected to a cold cathode tube 120, and the input (transmission end) terminal is connected to an AC power supply (not shown). Switch circuit 135 is connected. A cold cathode tube 120 is connected to an output (reception end) terminal of the external conductor 92, and a switch connected to the AC power supply (not shown) is connected to an input (transmission end) terminal. The circuit 135 is connected. The outer conductors 92, 92 are electrically connected by a connecting conductor 93 to make the electric potential equal. The line length (L) of the transmission line 100 is substantially equal to ほ ぼ wavelength of the frequency of the voltage applied to the transmission line 100. The transformer having such a configuration can increase both the magnetic permeability and the dielectric constant of the portion of the transmission line 100 where the electromagnetic field is generated by the dielectric properties and magnetism of the core 84, and as a result, the effect of shortening the high wavelength can be reduced. And this makes it possible to obtain 1
A / 4 wavelength line can be configured.

[0009]

In the transformer shown in FIG. 6, however, the wavelength can be shortened by the dielectric properties and magnetism of the core 84, and the core size can be shortened.
The installation area can be reduced, and downsizing is possible while maintaining a high step-up ratio and high conversion efficiency, but has the following complaints. In the transformer shown in FIG. 6, since a core 84 made of ferrite or the like is interposed between a portion where a high-frequency electric field is generated by the transmission line 100, that is, between the inner conductor 91 and the outer conductor 92, the transmission line 100 When a high-frequency voltage is applied, a loss occurs and the conversion efficiency (transformer characteristics) is reduced, which has been an obstacle to realizing a transformer with higher conversion efficiency. It is each core 84
This is because, when a high frequency voltage is applied to the transmission line 100, a current flows through each core 84 and a loss occurs because the resistance is low for use as an insulator at high frequencies.

In this transformer, the capacitance between the inner conductor and the outer conductor is controlled to produce a characteristic impedance to function as a transducer element. In the transformer shown in FIG. If the size of the internal conductors 91 is increased to reduce the size, the capacitance between the lines of the internal conductors 91 becomes large, so that the internal conductors 91 do not function as a distributed constant circuit. This is because the capacitance in the transformer shown in FIG. 6 depends on the core 84 and the insulator 85 between the inner conductor 91 and the outer conductor 92. In addition,
A transformer having a core having dielectric properties and magnetism, and a transmission line, a wavelength shortening effect is obtained by the dielectric constant and magnetic permeability of the core, the core size can be shortened, and the transformer can be miniaturized. It is called a transformer.

The present invention has been made in view of the above circumstances, and includes a voltage conversion section comprising a core having dielectric properties and magnetism, a line conductor and a ground conductor constituting a transmission line, and In a transformer in which the line length (L) is set to be approximately equal to a quarter wavelength on the transmission line at the operating frequency, even if the line conductors are densely arranged, the transformer functions as a distributed constant circuit, and is further reduced in size and thickness. A transformer capable of preventing a loss caused by a high-frequency voltage applied to the core, increasing the boost ratio, achieving higher conversion efficiency, and simplifying the structure. With the goal.

[0012]

A transformer according to the present invention has a line conductor and a ground conductor constituting a transmission line, and a voltage converter comprising a core having dielectric and magnetism. The length (L) is set substantially equal to a quarter wavelength on the transmission line at the operating frequency, and the ground conductor is provided between the core and the line conductor.

According to the transformer of the present invention, the transmission line includes a line conductor and a ground conductor, and a voltage conversion unit composed of a core having dielectric and magnetic properties. The transmission line has a line length (L). In a transformer set to be approximately equal to a quarter wavelength on the transmission line at the operating frequency, in particular, since the ground conductor is provided between the core and the line conductor, no high-frequency electric field is generated by the transmission line. Since a core having dielectric and magnetic properties is provided in the portion, even if a high-frequency voltage is applied to the transmission line, no voltage is applied to the core, and loss due to application of voltage to the core can be prevented. , The boost ratio can be made sufficiently high, and higher conversion efficiency can be achieved.

In the transmission line type transformer, the wavelength can be shortened by the effects of both the dielectric properties and the magnetism of the core, and thereby the core size can be shortened. In the present invention, since the core is disposed at a portion where a magnetic field is generated by the transmission line, an effect of shortening the wavelength by high magnetic permeability can be obtained. Further, since there is no core in the portion where the electric field is generated by the transmission line, the effect of shortening the wavelength by the high dielectric constant cannot be expected much. However, in the transformer shown in FIG. 6, a low dielectric constant is provided between the core and the internal conductor. Since an insulator made of polyimide (ε = 4) is arranged, most of the electric field is applied to the insulator, so that the effect of the dielectric properties of the core is not fully utilized. Therefore, the wavelength shortening effect is mainly achieved. This is due to the high permeability of the core, and therefore, the effect of shortening the wavelength shortening effect by changing the position of the core to the outside of the line conductor in the present invention is small.

In the converter according to the present invention, since the core is not interposed between the line conductor and the ground conductor, the dielectric constant of the core depends on the capacitance between the line conductor and the ground conductor. It has no effect, and the dielectric constant of the core does not affect the capacitance between the line conductors. Thereby, even if the line conductors are densely arranged and miniaturized, the capacitance between the line conductors is relatively large with respect to the capacitance between the line conductor and the ground conductor. Can be prevented from functioning as a distributed constant circuit.
Therefore, according to the present invention, even if the line conductors are densely arranged, the line conductor functions as a distributed constant circuit, and can be made smaller and thinner, and a loss caused by a voltage applied to the core is prevented. As a result, it is possible to provide a transformer capable of increasing the step-up ratio, achieving higher conversion efficiency, and simplifying the structure.

In the transformer according to the present invention, the line conductor is formed in a planar shape, the ground conductor is laminated on at least one surface of the line conductor via an insulator, and the core is formed on the ground conductor. May be laminated. The transformer according to the present invention is preferably provided with a load device having an impedance different from the intrinsic impedance of the voltage conversion unit. In the transformer according to the present invention, the insulator has an effective dielectric constant (ε) of 10%.
Preferably, it is made of a smaller material. According to such a transformer, the capacitance between the line conductor and the ground conductor can be determined only by the insulator, and even if the line conductors are densely arranged and miniaturized, the capacitance between the line conductors can be reduced. Since it is possible to prevent the capacitance between the line conductor and the ground conductor from becoming relatively large, it is possible to function as a distributed constant circuit. Further, in the transformer according to the present invention, the core is Mn-Zn ferrite, Ni
It may be composed of one or more selected from -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 has an effective magnetic permeability (μ) at 100 kHz.
Is from 10 to 20,000, and the effective dielectric constant (ε) is from 10 to 20,000.
Preferably it is 5000. The effect of shortening the wavelength increases as the effective magnetic permeability (μ) and the effective permittivity (ε) increase, so that the transformer can be downsized. However, the characteristic impedance of the transmission line increases as the effective magnetic permeability (μ) increases, but decreases as the effective dielectric constant (ε) increases. Therefore, there are optimal ranges 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 are in the above ranges.

[0018]

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 diagram illustrating a schematic configuration of a transformer according to a first embodiment of the present invention, and FIG. 2 is a plan view illustrating a main part of the transformer according to the first embodiment. The transformer according to the first embodiment is generally constituted by a voltage conversion unit 2 having cores 4 and 4 provided outside a transmission line 10 and a cold cathode tube 20 as a load device.

The voltage converter 2 includes a pair of opposing cores 4,
4, ground conductors 42, 42 are formed on opposite surfaces, respectively.
Further, insulating layers (insulators) 45, 45 are formed inside the ground conductors 42, 42, respectively.
Is provided with a line conductor 41 inside. In the first embodiment, the transmission line 10 is configured by the line conductor 41 and the ground conductors 42 and 42 above and below the line conductor 41.
Between each opposing surface of the pair of cores 4 and 4 and the ground conductor 42,
The first adhesive layer 6a is interposed, the second adhesive layer 6b is interposed between each ground conductor 42 and the insulating layer 45, and the line conductor 41 and the upper insulating layer 45 are A third adhesive layer 6c is interposed therebetween. The pair of cores 4 and 4 have dielectric properties and magnetism. Each core 4
Are Mn-Zn ferrite, Ni-Z
It is preferable to use one or two or more selected from the group of n ferrite and Ni-Cu ferrite in that the core dimensions can be shortened and the transformer can be miniaturized.

Preferably, each core 4 has an effective magnetic permeability (μ) at 100 kHz of 10 to 20,000 for the above-mentioned reason, and each core 4 has an effective dielectric constant (ε) of 10 to 5000. Certain is preferred for the reasons mentioned above.

The line conductor 41 has a spiral coil shape. The ground conductors 42, 42 may be in the form of a spiral coil, or may be in the form of a film (planar) formed on the entire surface facing the cores 4, 4. Line conductor 4
1 and the ground conductors 42, 42
It is preferable that the capacitance is sufficiently large with respect to the capacitance between the lines, and it is preferable that the capacitance is at least equal to or larger than the capacitance. This capacitance is
It depends on the line width and interval of the line conductor 41 and the thickness of each insulating layer 45. Each insulating layer 45 is made of polyimide having ε = about 4. If the thickness of each insulating layer 45 is too thick, the capacitance between the line conductor 41 and the ground conductors 42, 42 will be small, and if the thickness is too thin, the capacitance will be large.

The output 41 (receiving end) of the line conductor 41 is connected to the cold cathode tube 20 and the input (transmitting) terminal 41b is connected to an AC power supply ( (Not shown) is connected to the switch circuit 35. The output terminal of one of the ground conductors (the lower ground conductor with respect to the line conductor 41) is connected to the cold cathode tube 20, and the input terminal is connected to the AC power supply. Switch circuit 35 is connected. One of the ground conductors (the lower ground conductor with respect to the line conductor 41)
42 and the other ground conductor (the upper ground conductor with respect to the line conductor 41) 42 are connected to the connecting conductor 4 in order to make the potential the same.
3 are electrically connected.

The line length (L) of the transmission line 10 composed of the line conductor 41 and the ground conductors 42, 42 is set to a quarter wavelength on the transmission line 10 at the frequency (operating frequency) of the AC voltage applied to these conductors. They are set almost equal. In the first embodiment, 1 /
What is set substantially equal to the four wavelengths is the length of the line conductor 41. If the line length (L) of the transmission line 10 is not substantially equal to the 波長 wavelength on the transmission line 10 at the operating frequency, a case where the cold cathode tube 20 having an impedance larger than the intrinsic impedance of the voltage conversion unit 2 is connected. To
Since impedance conversion and voltage conversion are not performed, it is not preferable.

As the cold cathode tube 20, one having an impedance different from the intrinsic 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 20 having a larger impedance 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 the transformer according to the first embodiment having the above configuration, the parasitic capacitance (distribution constant) is taken into the circuit constant,
A pair of cores 4 and 4 having dielectric and magnetic properties, and a transmission line 1
A distributed constant circuit as shown in FIG. 3 using 0 is configured. In Figure 3, reference numeral V ₁ was input voltage, V ₂ reception terminal voltage, I
₁ is the 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,
Z ₀ is the specific impedance of the transmission line, and L is the line length of the transmission line. The distributed constant circuit shown in FIG. 3 is represented by the following equation (1).

[0026]

(Equation 1)

In the above equation, V ₁ is the input voltage, V ₂ is the receiving end voltage, I ₁ is the input current, I ₂ is the receiving end current, Z ₀ is the specific impedance of the transmission line, and L is the line length of the transmission line. , Β are the propagation constants of the line 10 (β = 2πf / v = 2π / λ...
(Equation (1-a)). In the equation (1-a), v is a propagation speed (= fλ), and λ is a propagation wavelength.

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

[0029]

(Equation 2)

By transforming the above equation (4) and obtaining the impedance Z ₁ seen from the input side, Z ₁ = V ₁ / I ₁ = (jZ ₀ · I ₂ ) / ((j / Z ₀ ) · V ₂ ) Equation (5) Since V ₂ = Z ₂ · I ₂ , Z ₁ = Z ₀ / (Z ₂ / Z ₀ ) = Z ₀ ² / Z ₂ Equation (6) This is the case where 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 of the transmission line is the propagation wavelength / 4, the above-mentioned relationship is established and the voltage conversion is performed. Since the step-up ratio is determined by the ratio of the inherent impedance of the transmission line and the load resistance (the resistance of the load device), the transformer according to the first embodiment has a high resistance at the time of starting requiring a high voltage and a high resistance at the time of lighting. It is suitable for the impedance characteristic of the cold cathode fluorescent lamp in which the resistance decreases.

Next, the operation of the transformer according to the first embodiment will be described with reference to equations (6) and (7) and FIG. FIG. 4 is a graph for explaining the boosting action of the transmission line of the transformer according to the first embodiment. In the graph of FIG. 4, the horizontal axis represents the ratio of the impedance Z ₂ seen from the output side to the inherent impedance Z ₀ of the line 10. Here, it is assumed that the input voltage V ₁ is a constant voltage. The load impedance Z ₂ is equal to the inherent impedance Z ₀ of the transmission line 10.
(Z ₂ / Z ₀ = 1), the transmission line 10 is in a matching state, and 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 satisfying Z ₂ > Z ₀ is connected (Z ₂ / Z ₀ > 1), the above equation (6) is used.
Z ₁ <Z _0, 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. Z
_In the region of ₂ > Z ₀ , V ₂ is larger than V ₁ , and is boosted. Therefore, when a load larger than the inherent impedance of the line 10 is connected as a load on the transmission line 10 having a line length L of 1/4 wavelength on the transmission line at the operating frequency, the inherent end of the line 10 is connected to both ends of the load. A voltage higher than the input voltage is applied at a magnification corresponding to the ratio with the impedance.

Next, in the transformer of the first embodiment,
The reason why the wavelength can be shortened and the transformer can be downsized by using the core 4 as described above will be described. The wavelength in free space is represented by the following equation (8). λ = v / f Equation (8) If the magnetic permeability / permittivity of the portion of the voltage converter 2 where the electromagnetic field is generated is large, the traveling speed v of the traveling wave becomes slow. 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) Therefore, the wavelength in that case is represented by the following expression (10). λ = (v / f) · (ε ^1/2 · μ ^1/2 ) ^-1 Equation (10) As is apparent from the above equation (10), the wavelength is shortened according to the values of the permittivity and the magnetic permeability. That is, when the permittivity and the magnetic permeability increase, the wavelength also decreases accordingly. Therefore, by forming the core 4 from a material having a high permittivity and the magnetic permeability, the wavelength can be shortened, and the core size can be reduced. Can be shortened, and the size of the transformer can be reduced.

The transformer of the present embodiment can reduce the wavelength and the core size by the effects of both the dielectric properties and the magnetic properties of the cores 4 and 4 as described above. In particular, since the cores 4 and 4 are arranged in the portion where the magnetic field is generated by the transmission line 10, a wavelength shortening effect by high magnetic permeability can be obtained. As a result, the core size can be reduced, so that the installation area can be reduced, and the transformer can be downsized while maintaining a high step-up ratio and high conversion efficiency. In the present embodiment, the ground conductors 42 and 42 are provided between the cores 4 and 4 and the line conductor 41, so that the cores 4 and 4 are provided in a portion where the transmission line 10 does not generate a high-frequency electric field. That is, even if a high-frequency voltage is applied to the transmission line 10, no voltage is applied to the cores 4 and 4, the loss caused by the voltage applied to the cores 4 and 4 can be prevented, and the boost ratio can be sufficiently increased. , Higher conversion efficiency can be achieved. Furthermore, in this embodiment, since the core is not interposed between the line conductor 41 and the ground conductors 42, 42, the dielectric constant of the core affects the capacitance between the line conductor 41 and the ground conductors 42, 42. No, and the line conductor 4
The dielectric constant of the core does not affect the capacitance between the lines. As a result, even if the line conductors 41 are densely arranged and miniaturized, the capacitance between the lines of the line conductors 41 is reduced.
Since it is possible to prevent the capacitance from becoming relatively large with respect to the capacitance between the first and ground conductors 42, it is possible to function as a distributed constant circuit.

Further, in the transformer according to the present embodiment, a high step-up ratio and high conversion efficiency can be achieved without using an auxiliary transformer such as a winding transformer, so that the transformer is thinner than a piezoelectric transformer using an auxiliary transformer. Is possible. Further, by simply providing the cores 4 and 4 outside the transmission line 10 including the line conductor 41 and the ground conductors 42 and 42, both a high step-up ratio and a high conversion efficiency can be achieved, and the structure can be simplified. is there. In addition, since the line conductor 41 can be formed on the insulating layer 45 by a method such as plating or sputtering, a thin conductor can be formed, and a thin transformer can be provided. Therefore, according to the transformer of the first embodiment, even if the line conductors 41 are densely arranged, the transformer functions as a distributed constant circuit, and can be made smaller and thinner, and a voltage is applied to the core. , A booster ratio can be increased, a higher conversion efficiency can be achieved, and a transformer that can be simplified in structure can be provided.

In the transformer according to the present embodiment, one or more elements T selected from the group consisting of Fe, Co, and Ni, and 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, a soft magnetic alloy powder containing one or more elements M selected from the group of rare earth elements and one or two or more elements D selected from the group of O, C, N, and B; The use of a synthetic resin is preferable in that the magnetic permeability and the dielectric constant of the pair of cores 4 and 4 can be increased, the wavelength shortening effect becomes sufficient, and the transformer can be miniaturized.

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 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.

Each of the cores 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, N
b, Mo, Cr, Mg, Mn, Al, Si, Ca, S
r, Ba, Cu, Ga, Ge, As, Se, Zn, C
powder selected from at least one element selected from the group consisting of d, In, Sn, Sb, Te, Pb, Bi, and rare earth elements, oxides, carbides, carbonates, nitrides, and borides Is used. Examples of the rare earth element include Sc, Y or La, C belonging to Group 3A of the periodic table.
e, Pr, Nd, Pm, Sm, Eu, Gd, Td, D
Examples include at least one element selected from the group of lanthanoids such as y, Ho, Er, Tm, Yb, and Lu, or a mixture thereof. At this time, the T powder has a particle size of 100.
It is desirable that the powder of M or less and M have a particle size of 2 μm or less.

Next, when adding O, C, and N of D, the above-described 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 liquid 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 4, 4 constructed of a soft magnetic alloy powder and a synthetic resin represented by D _c, the permeability and permittivity is sufficiently large, therefore, provided a pair of core 4,4 on the outside of the transmission line 10 modified In a vessel, the wavelength shortening effect is sufficient,
The core size can be shortened, and the transformer can be downsized.

Next, a description will be given of a second embodiment of the transformer according to the present invention. FIG. 5 is a diagram illustrating a schematic configuration of the transformer according to the second embodiment. The difference between the transformer of the second embodiment and the transformer of the first embodiment shown in FIGS. 1 and 2 is that not one surface of the line conductor 41 but one surface of the line conductor 41 (the lower surface in the drawings). 2) is that the ground conductor 42 is provided via the insulating layer 45, and the core 4 having dielectric and magnetism is provided on the lower surface of the ground conductor 42. A first adhesive layer 6a is interposed between the core 4 and the ground conductor 42, and a second adhesive layer 6b is interposed between the ground conductor 42 and the insulating layer 45.

A cold cathode tube 20 is connected to a terminal (not shown) on the output side (reception end side) of the line conductor 41 as described above, and a terminal (not shown) on the input side (transmission end side). Is connected to a switch circuit 35 connected to an AC power supply (not shown). Further, a terminal on the output side of the ground conductor 42 (not shown)
Is connected to a cold-cathode tube 20, and a terminal on the input side is connected to a switch circuit 35 connected to the AC power supply. According to the transformer of the second embodiment, by adopting the above-described configuration, substantially the same operation and effect as those of the transformer of the first embodiment can be obtained. Instead, the ground conductor 42 is provided on one surface via the insulating layer 45, and the core 4 having dielectric and magnetism is formed on the lower surface of the ground conductor 42. Further simplification of the structure is possible.

[0048]

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. (Experimental Example 1) A transformer (Example 1) similar to the transformer of the first embodiment shown in FIGS. 1 and 2 was manufactured. The thickness of each core 4 made of Mn-Zn ferrite of the voltage converter 2 of the transformer manufactured here is 0.5 mm, the real part (μ ′) of the magnetic permeability is 1500, and the imaginary part (μ ″) of the magnetic permeability. Is 20,
The dielectric constant (ε _F ) is 1.0 × 10 ⁵ and the specific resistance (ρ) is 3.0.
Ωm, and the length (L) of the spiral coil type transmission line 10 provided inside the cores 4 and 4 is substantially equal to １ ／ wavelength on the transmission line at the operating frequency. Has a thickness of 35 μm and a width of 0.23 m
m, the number of turns was 19.5, the conductor spacing was 0.30 mm, the thickness of each ground conductor 42 was 38 μm, and the polyimide (ε
= 4), the thickness of the insulating layer 45 below the line conductor 41 is set to 70 μm, and the thickness of the insulating layer 45 above the line conductor 41 is set to 7 μm. The total thickness of the adhesive layers 6a to 6c was set to 236 μm.

For comparison, a transformer similar to that shown in FIG. 6 (Comparative Example 1) was manufactured. Each core 8 made of Mn-Zn ferrite of the voltage converter 102 of the transformer manufactured here
4, the thickness is 0.5 mm, and the real part (μ ′) of the magnetic permeability is 15
00, the imaginary part (μ ″) of the magnetic permeability is 20, and the dielectric constant (ε _F )
Is set to 1.0 × 10 ⁵ , the specific resistance (ρ) is set to 3.0Ωm, the line length (L) of the spiral coil type transmission line 100 is almost equal to １ ／ wavelength on the transmission line at the operating frequency, The thickness of the internal conductor 91 is 35 μm, and the width is 0.1 μm.
23mm, number of turns 19.5, conductor spacing 0.30m
m, the thickness of each outer conductor 92 is set to 38 μm, and the thickness of the insulator 85 below the inner conductor 91 among the insulating layers 85, 85 made of polyimide (ε = 4) is 70 μm, The thickness of the insulator 85 was set to 7 μm, and the total thickness of the five adhesive layers 86 was set to 236 μm.

The transformer load characteristics of the voltage converters of the transformers of Example 1 and Comparative Example 1 manufactured here were measured. In this measurement, the impedance analyzer HP
Using 4194A (trade name; manufactured by Japan Hewlett-Packard Co., Ltd.), the termination resistance for connecting the measurement of the gain (Gv) to the terminal on the output side is 100 kΩ, 47 kΩ, 10 kΩ.
And changed. The measurement frequency range is 0.01 to 1
MHz. A carbon film resistor was used as the terminating resistor (RL). The measurement results are shown in Table 1.

[0051]

[Table 1]

In Table 1, Gv represents a gain. From the results shown in Table 1, in the transformer of Example 1 in which the ground conductor was provided between the core and the line conductor (the core was provided outside the transmission line), the core was interposed between the inner conductor and the outer conductor. It can be seen that the gain (boost ratio) is higher than that of the transformer of Comparative Example 1 and that the higher the termination resistance, the higher the gain (boost ratio) is obtained.

[0053]

As described above, the transformer according to the present invention has a line conductor and a ground conductor constituting a transmission line, and a voltage converter comprising a core having dielectric and magnetism. The line length (L) of the line is set substantially equal to a quarter wavelength on the transmission line at the operating frequency, and the ground conductor is provided between the core and the line conductor. Since a core having dielectric and magnetic properties is provided in a portion where no generation occurs, no voltage is applied to the core even when a high-frequency voltage is applied to the transmission line, and a loss due to the application of a voltage to the core is reduced. Can be prevented, the boost ratio can be sufficiently increased, and higher conversion efficiency can be achieved. In the converter of the present invention, since no core is interposed between the line conductor and the ground conductor, the dielectric constant of the core does not affect the capacitance between the line conductor and the ground conductor. The dielectric constant of the core does not affect the capacitance between the line conductors. Accordingly, even if the line conductors are densely arranged and miniaturized, the capacitance between the line conductors is relatively large with respect to the capacitance between the line conductor and the ground conductor. Can be prevented from functioning as a distributed constant circuit. Therefore, according to the present invention, even if the line conductors are densely arranged, the line conductor functions as a distributed constant circuit, and can be made smaller and thinner, and a loss caused by a voltage applied to the core is prevented. As a result, it is possible to provide a transformer capable of increasing the step-up ratio, achieving higher conversion efficiency, and simplifying the structure.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a transformer according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a main part of the transformer of FIG. 1;

FIG. 3 is a diagram for explaining 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 diagram illustrating a schematic configuration of a transformer according to a second embodiment of the present invention.

FIG. 6 is a diagram showing a schematic configuration of a conventional transformer.

[Explanation of symbols]

2 ... voltage converter, 4 ... core, 6a ... first adhesive layer,
6b ... second adhesive layer, 6c ... third adhesive layer, 10 ...
Transmission line, 20: cold cathode tube (load device), 41: line conductor, 41a: terminal on output side (reception end side), 41b: terminal on input side (transmission end side), 42: ground conductor 43: connection conductor 45: insulating layer (insulator)

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshio Takahashi 1-7 Yukitani Otsukacho, Ota-ku, Tokyo Alps Electric Co., Ltd.

Claims (6)

[Claims] 1. A transmission line, comprising: a line conductor and a ground conductor constituting a transmission line; and a voltage conversion unit comprising a core having dielectric and magnetic properties, wherein a line length (L) of the transmission line is above the transmission line at an operating frequency. Wherein the ground conductor is provided between the core and the line conductor. 2. The line conductor is formed in a planar shape, the ground conductor is laminated on at least one surface of the line conductor via an insulator, and the core is laminated on the ground conductor. The transformer according to claim 1, wherein: 3. The transformer according to claim 1, further comprising a load device having an impedance different from an intrinsic impedance of the voltage conversion unit. 4. The transformer according to claim 2, wherein the insulator is made of a material having an effective dielectric constant (ε) of less than 10. 5. The core is made of Mn—Zn ferrite, Ni
The transformer according to any one of claims 1 to 4, wherein the transformer comprises one or more selected from the group consisting of -Zn ferrite and Ni-Cu ferrite. 6. The core according to claim 1, wherein the core has an effective magnetic permeability (μ) at 100 kHz of 10 to 20,000 and an effective permittivity (ε) of 10 to 5000. Transformer.