JP2000077246A - Transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase boosting ratio, to achieve high conversion efficiency, and to facilitate structure by at least providing a transmission line consisting of at least a pair of conductors and a voltage conversion part that has a core with dielectric and magnetic properties. SOLUTION: A voltage conversion part 2 is composed of a core part 3 and a transmission line 10. In the core part 3, an insulation layer is formed on both surfaces of a core with dielectric and magnetic properties via a first adhesion layer, and, furthermore, a second adhesion layer is formed on the insulation layer. As a material of the core, one kind or two kinds or more selected from a group of Mn-Zn ferrite, Ni-Zn ferrite, and Ni-Cu ferrite are used. In the core, effective permeability μ at 100 kHz should be set to 10-20,000, and also effective permittivity ε should be set to 10-5,000. A transmission line 10 consists of a pair of conductors 11 and 12, which is formed while being wound around the core part 3.

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 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.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a high step-up ratio, a high conversion efficiency, and a simple structure even if the device is made thinner and smaller. The purpose is to provide transformers.

[0007]

According to the present invention, there is provided a transformer comprising at least a transmission line comprising at least a pair of conductors and a voltage converter having a core having dielectric and magnetism. Is what you do. Preferably, the transformer according to the present invention includes 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 core is Mn-Zn ferrite, Ni-
It may be composed of one or more selected from the group of Zn ferrite and Ni-Cu ferrite. Further, in the transformer according to the present invention, the core may be F
e, one or more elements T selected from the group of Co, Ni, and Hf, Zr, W, Ti, V, Nb, Mo, C
r, Mg, Mn, Al, Si, Ca, Sr, Ba, C
u, Ga, Ge, As, Se, Zn, Cd, In, S
n, Sb, Te, Pb, Bi, one or more elements M selected from the group of rare earth elements, and one or more elements selected from the group of O, C, N, B It is preferably made of a soft magnetic alloy powder containing D and a synthetic resin.

Further, in the transformer according to the present invention, the core has an effective magnetic permeability μ at 100 kHz of 1%.
0 to 20000, and the effective dielectric constant ε is 10 to 5000.
It is preferred that Further, in the transformer according to the present invention, it is preferable that the line length L of the transmission line is substantially equal to １ ／ wavelength of the frequency of the voltage applied to the transmission line. In the transformer according to the present invention, the pair of conductors of the transmission line may be an inner conductor provided between the cores and an outer conductor provided outside the core.

[0009]

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 schematic configuration of a transformer according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view of the transformer according to the first embodiment. The transformer of the first embodiment includes a voltage converter 2
And a cold cathode tube 20 as a load device.

The voltage conversion unit 2 includes a core unit 3 and a transmission line 1.
0. As shown in FIG. 2, an insulating layer 6 is formed on both surfaces of a core 4 having dielectric and magnetic properties via a first adhesive layer 5, and a second adhesive layer is formed on the insulating layer 6. The layer 7 is formed. The material forming the core 4 is Mn-Zn ferrite, Ni-Zn
1 selected from the group of ferrite and Ni-Cu ferrite
It is preferable to use a kind or a combination of two or more kinds in that the dimension of the core 4 can be shortened and the transformer can be downsized.

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 wavelength shortening effect 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 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, μ and ε
Is preferably in the above range.

As a material forming the insulating layer 6, polyimide or the like is used. The transmission line 10 includes a pair of conductors 11, 1
It consists of two. The pair of conductors 11 and 12
Are formed so as to be wound around the core portion 3 respectively. In the transmission line 10, the direction of the current flowing in the conductor on one surface side of the core portion 3 and the direction of the current flowing in the conductor on the other surface side are reversed (the current direction is opposite on the front and back sides of the core portion), and the magnetic flux is reduced. It has a constructive structure. In the first embodiment, one conductor 11 and the other conductor 12 are formed in the core portion 3 so that the magnetic flux is directed in the direction of the arrow MF.
In the figure, reference numeral I _a, the direction of the arrow indicated by I _b, the conductor 1
This is the direction of the magnetic flux generated by the current flowing through 1 and 12. As a method of forming such a transmission line 10 around the core portion 3, for example, a general coated copper wire is wound, a conductor is formed on the insulating layer 6 by plating or sputtering, an adhesive layer 5. The insulating layer 6, the second adhesive layer 7, and the conductor may be integrally formed to be processed into a belt shape, and may be formed on both surfaces of the core 4 in a predetermined shape.

One conductor 11 of such a transmission line 10
The cold cathode tube 20 is connected to the output side (reception end side) terminal 11a, and the input side (transmission end side) terminal 11b is connected to
A switch circuit (not shown) connected to an AC power supply (not shown) is connected. The cold cathode tube 20 is connected to an output (reception end) terminal 12a of the other conductor 12, and an AC power supply (not shown) is connected to an input (transmission end) terminal 12b. ) Is connected to the switch circuit (not shown). Each conductor 11, 1 of the transmission line 10
The line length L of the second line is preferably substantially equal to １ ／ wavelength of the frequency (operating frequency) of the AC voltage applied to the transmission line 10. The line length L of the transmission line 10 is １ ／ of the frequency (operating operation frequency) of the AC voltage applied to the transmission line 10.
If the wavelength is not substantially equal, the cold cathode fluorescent lamp 20 having an impedance larger than the intrinsic impedance of the voltage converter 2
Is connected, impedance conversion and voltage conversion are not performed, which is not preferable.

As the cold-cathode tube 20, one having an impedance different from that 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 of the first embodiment, the direction of the magnetic flux is the direction shown by the arrow MF in FIG.

In the transformer according to the first embodiment having the above configuration, the parasitic capacitance (distribution constant) is taken into the circuit constant,
A distributed constant circuit as shown in FIG. 3 using the core 4 having dielectric properties and magnetism and the transmission line 10 is configured. FIG.
Where 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 ₁ is the impedance seen from the input side, Z ₂ is the impedance seen from the output side, Z ₀ is a specific impedance of the transmission line 10, and L is each conductor 11, 12
Is the line length. The distributed constant circuit shown in FIG. 3 is represented by the following equation (1).

[0016]

(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 ₁ is the impedance viewed from the input side, and Z ₂ is the output side. , Z ₀ is the inherent impedance of the transmission line 10, L
Is the line length of each of the conductors 11 and 12, and β is the propagation constant of the transmission line 10 (β = 2πf / v = 2π / λ... (1-a))
It is. In equation (1-a), v is the propagation velocity (= fλ), λ
Is the propagation wavelength.

In this embodiment, since the line length L of the conductors 11 and 12 is λ / 4 of the operating frequency, βL = (2π / λ) × (λ / 4) = π / 2. Therefore, equation (1) can be expressed by equation (4) below.

[0019]

(Equation 2)

By transforming the above equation (4) to find the impedance Z ₁ as seen 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) Indicates that when the propagation wavelength / 4 = transmission line length, if an impedance of 100 ohms is connected to the terminal on the output side of the transmission line having a specific impedance of 50 ohms, it looks like 25 ohms when viewed from the input side. indicates the 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. As described above, since the step-up ratio is determined by the ratio of the inherent impedance of the transmission line 10 and the load resistance (the resistance of the load device), the transformer according to the first embodiment has a high resistance and a high lighting during startup when a high voltage is required. It is suitable for the impedance characteristic of a cold cathode tube in which the resistance sometimes drops.

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 (load impedance) Z ₂ viewed from the output side to the inherent impedance Z ₀ of the transmission line 10. Here, it is assumed that the input voltage V ₁ is a constant voltage. The load impedance Z ₂ is the transmission line 10
If equal to the characteristic impedance Z ₀ of the (Z ₂ / Z ₀ =
In 1), it is clear that the transmission line is in a matching state, and the voltages at the transmitting 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 where Z ₂ > Z ₀ , V ₂ is larger than V ₁ , and is boosted. Therefore, the transmission line 10 whose line length L is １ ／ wavelength of the operating frequency is
When a load larger than the inherent impedance of the line 10 is connected as a load, a voltage higher than the input voltage is applied to both ends of the load at a magnification corresponding to a ratio with respect to the inherent impedance of the transmission line 10.

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 (8) If the permittivity and the magnetic permeability of the portion of the voltage converter 2 where the electric field is generated are 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) 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. It can be shortened, and the transformer can be downsized.

Accordingly, in the transformer according to the first embodiment, the transmission line 10 including the pair of conductors 11 and 12, the voltage conversion unit 2 including the core 4 having dielectric and magnetism, and the voltage conversion unit Since the cold cathode tube (load device) 20 having an impedance different from the intrinsic impedance of the unit 2 is provided, the wavelength can be shortened, and the core size can be shortened. The transformer can be downsized while maintaining high conversion efficiency. In addition, 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 thickness can be reduced as compared with a piezoelectric transformer using an auxiliary transformer. Further, by simply providing the transmission line 10 on the core 4 having electro-electricity and magnetism, it is possible to achieve both a high step-up ratio and a high conversion efficiency, and the structure can be simplified.

In the transformer according to the present embodiment, the material constituting the core 4 is 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;
The use 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 increases the magnetic permeability and dielectric constant of the core 4. Can,
This is preferable because the wavelength shortening effect is sufficient and the transformer 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 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. Examples of the synthetic resin 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 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 desired magnetism and dielectric properties of the core 4, but the volume ratio in the slurry is 50%.
It is preferable to add so as to be about 80 vol%.
If the volume ratio of the soft magnetic alloy powder is less than 50 vol%, there may be a problem that the magnetic permeability becomes low. On the other hand, if the volume ratio exceeds 80 vol%, it becomes difficult to mold by injection molding or the like. There is fear.

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.

Then, 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 powder of a TM alloy ribbon obtained by a liquid quenching method instead 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
The core 4 constructed of a soft magnetic alloy powder and a synthetic resin represented by D _c, the permeability and permittivity is sufficiently large, therefore,
The voltage converter 2 including such a core 4 and the transmission line 10
In particular, in the transformer having the above, the effect of shortening the wavelength is sufficient, the core size can be shortened, and the transformer can be downsized.

The transformer according to the present invention may have a structure as shown in FIG. FIG. 5 is a cross-sectional view illustrating the transformer according to the second embodiment. The transformer of the second embodiment differs from the transformer of the first embodiment shown in FIGS. 1 and 2 in that a cover 22 that covers the transmission line 10 is provided at the outermost part. The cover 22 is provided for preventing electric shock and is made of an insulating material.

The transformer according to the present invention may have a structure as shown in FIGS. 6 and 7
FIG. 5 is a view showing a third embodiment of the transformer according to the present invention.
The transformer according to the third embodiment includes a transmission line 10 including a coil-shaped conductor 31 and a film-shaped conductor 32, a voltage conversion unit 2 including a core 4 having dielectric and magnetism, and a voltage conversion unit 2. A cold cathode tube (load device) 20 having an impedance different from the intrinsic impedance is provided. A terminal 31a on the output side (reception end side) of the coiled conductor 31 includes:
The cold cathode tube 20 is connected, and a switch circuit 35 connected to an AC power supply (not shown) is connected to a terminal 31b on the input side (transmission end side). The cold cathode tube 20 is connected to an output (reception end) terminal of the film conductor 32, and the AC power supply (not shown) is connected to an input (transmission end) terminal. The connected switch circuit 35 is connected. In the transformer of the third embodiment, the coiled conductor 31
The step-up ratio (gain) and the operating frequency can be adjusted by using the capacitance between the film conductor 32 and the capacitor. According to the transformer of the third embodiment, by adopting the above-described configuration, a high boosting ratio, high conversion efficiency, and simplification of the structure can be achieved even when the transformer is made thin and small. . In the transformer according to the third embodiment, the case where the conductor 32 is in the form of a film formed on the entire surface of the core 4 has been described, but may be in the form of a coil.

The transformer of the present invention may have a structure as shown in FIG. FIG. 8 is a diagram showing a fourth embodiment of the transformer according to the present invention. The transformer according to the fourth embodiment includes a pair of cores 4 and 4 having dielectric and magnetic properties,
The coil-shaped inner conductor 41 provided between the cores 4, 4 and the outer conductors 42, 4 provided outside the cores 4, 4.
2 and a cold-cathode tube (load device) 20 having an impedance different from the intrinsic impedance of the voltage conversion unit 2. The outer conductors 42, 42 may be coil-shaped or film-shaped. These outer conductors 42,
Reference numerals 42 are electrically connected by a connection conductor 43 to make the same potential. According to the transformer of the fourth embodiment, particularly, since two cores 4 are used, the inductance can be increased as compared with the transformer of the third embodiment, and the capacitance (C ) Can be increased, and there is an advantage that the degree of freedom in circuit design is increased.

The transformer according to the present invention may have a structure as shown in FIG. FIG. 9 is a view showing a fifth embodiment of the transformer according to the present invention. The difference between the transformer of the fifth embodiment and the transformer of the fourth embodiment shown in FIG. 8 is that the transformer is provided only outside one of the pair of cores 4, 4. It is.

[0039]

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 of the second embodiment shown in FIG. 5 was manufactured. The thickness d of the core portion 3 of the voltage converter 2 of the transformer manufactured here is 0.955 mm, and the total thickness t ₁ of the first adhesive layer 5, the insulating layer 6, and the second adhesive layer 7 is 0.325 m.
m, the thickness t _{2 of the} core 4 made of Mn—Zn ferrite is 0.89 mm, and the thickness t _{3 of the} conductors 11 and 12 is 0.03 m.
m, and the width W of the conductors 11 and 12 was 1.24 mm. The line length L of each of the conductors 11 and 12 is 0.34.
m. Note that the voltage conversion unit 2 manufactured here includes:
A cover 22 is provided similarly to the second embodiment in FIG. The gain phase of the voltage converter of the transformer manufactured here was measured. In this measurement, the terminating resistor Z _L for connecting the gain phase (using a dedicated measurement jig) to the output side terminal was set to 1 kΩ using an impedance analyzer HP4194A (trade name, manufactured by Hewlett-Packard Japan Limited). The test was performed while changing the values to 10 kΩ and 20 kΩ. The measurement frequency range was 1 MHz to 40 MHz so that points near resonance could be finely taken. A carbon film resistor was used for the terminating resistor Z _L. The measurement results are shown in FIGS. Also, the frequency f when tuned to λ / 4,
The value of the gain G _v is shown below.

When Z _L = 1 kΩ, f = 13.85 (MHz), G _v = 1
8.22 dB When Z _L = 10 kΩ, f = 13.59 (MHz), G _v = 3
When 0.22 dB Z _L = 20 kΩ, f = 13.22 (MHz), G _v = 4
5.29 dB

From the results shown in FIGS. 10 to 12, when the phase (phase difference between input and output voltages) is -90 (deg.), The gain is maximum, and as the terminating resistance increases, the gain ( It can be seen that the step-up ratio was obtained.

When the required line length when the transformer of the example was used as a backlight inverter of a liquid crystal display device was calculated as follows, the used frequency was 12 cm at 60 kHz. The transformer of this example had an effective magnetic permeability μ = 1500 and an effective dielectric constant ε = 70000.

[0043]

(Equation 3)

As described above, the transformer of the embodiment has a wavelength shortening effect due to the use of the core having magnetism and dielectric properties. Therefore, the line length is significantly reduced as compared with the transformer of the comparative example using a coaxial cable described later. We can see that we can do it.

(Comparative Example) A conventional transformer in which a high-frequency coaxial cable was provided as a voltage converter (transformer of a comparative example) had a line length of 884 m. The line length of the transformer of the comparative example is obtained by calculating the required length when the used frequency is 60 kHz when the transformer is used as a backlight inverter of a liquid crystal display device as follows. It is. The effective permittivity ε of the insulator of the coaxial cable was 2.

[0046]

(Equation 4)

[0047]

As described above, the transformer of the present invention has at least the transmission line composed of a pair of conductors and the voltage converter having the core having dielectric and magnetism. Since the wavelength can be shortened and the core size can be shortened, the installation area can be reduced, and the transformer can be downsized while maintaining a high step-up ratio and high conversion efficiency. Also, high boost ratio and high conversion efficiency can be achieved without using an auxiliary transformer such as a winding transformer.
The thickness can be reduced as compared with a piezoelectric transformer using an auxiliary transformer. In addition, even if the voltage conversion unit has a simple configuration in which a transmission line is provided in a core having electro-electricity and magnetism, a high step-up ratio and high conversion efficiency can be achieved, and the structure can be simplified. is there.

In the case where a load device having an impedance different from the intrinsic impedance of the voltage conversion unit is provided, the load is input to both ends of the load at a magnification corresponding to the ratio of the characteristic impedance to the intrinsic impedance of the voltage conversion unit. A voltage different from the voltage can be applied, particularly when the load device has an impedance larger than the intrinsic impedance of the voltage conversion unit. A voltage higher than the input voltage can be applied at a magnification, and can be suitably used for a backlight inverter of a liquid crystal display device.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a schematic configuration of a transformer according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing 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 cross-sectional view illustrating a schematic configuration of a transformer according to a second embodiment of the present invention.

FIG. 6 is a sectional view showing a schematic configuration of a transformer according to a third embodiment of the present invention.

FIG. 7 is a plan view illustrating a voltage transformer of the transformer of FIG. 6;

FIG. 8 is a cross-sectional view illustrating a schematic configuration of a transformer according to a fourth embodiment of the present invention.

FIG. 9 is a cross-sectional view illustrating a schematic configuration of a transformer according to a fifth embodiment of the present invention.

FIG. 10 is a diagram showing gain-phase characteristics when the terminating resistance is 1 kΩ.

FIG. 11 is a diagram showing gain-phase characteristics when the terminating resistance is 10 kΩ.

FIG. 12 is a diagram showing gain-phase characteristics when the terminating resistance is 20 kΩ.

[Explanation of symbols]

2 ... voltage conversion unit, 4 ... core, 10 ... transmission line, 11 ...
..Conductors, 12 conductors, 20 cold cathode tubes (load devices),
31 ... conductor, 32 ... conductor, 41 ... internal conductor, 42 ...
Outer conductor.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Takashi Hatanai, Inventor Takashi Hatani, 1-7 Yukiya Otsukacho, Ota-ku, Tokyo Inside the Alps Electric Co., Ltd. (72) Inventor Toshio Takahashi 1-7, Yukitani-Otsukacho, Ota-ku, Tokyo Alps Electric Co., Ltd. (72) Inventor Yutaka Yamamoto 1-7 Yukitani Otsukacho, Ota-ku, Tokyo Alps Electric Co., Ltd. (72) Inventor Akihiro Makino 1-7 Yukitani-Otsukacho, Ota-ku, Tokyo Alps Inside the Electric Company (72) Inventor Toshiro Sato 1006-1-1, Inaba, Nagano City, Nagano Prefecture

Claims (7)

[Claims] 1. A transformer comprising at least a transmission line comprising at least a pair of conductors and a voltage converter having a core having dielectric and magnetism. 2. The transformer according to claim 1, further comprising a load device having an impedance different from an intrinsic impedance of the voltage conversion unit. 3. The core is made of Mn—Zn ferrite, Ni
3. The transformer according to claim 1, wherein the transformer comprises one or more selected from the group consisting of —Zn ferrite and Ni—Cu ferrite. 4. 4. The core comprises 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 transformer according to any one of claims 1 to 3, wherein the transformer is made of a synthetic resin. 5. 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 4, wherein the number is from 5000 to 5000. 6. The transformer according to claim 1, wherein a line length L of the transmission line is substantially equal to １ ／ wavelength of a frequency of a voltage applied to the transmission line. 7. The transmission line according to claim 1, wherein the pair of conductors of the transmission line are an inner conductor provided between the cores and an outer conductor provided outside the cores. The transformer according to any one of the above.