JP3637777B2 - noise filter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a noise filter that filters switching noise generated in accordance with a switching operation of a semiconductor switch element that constitutes a power converter such as an inverter.
[0002]
[Prior art]
The switching operation of the semiconductor switch element constituting the power converter such as an inverter is performed based on a drive signal pulse-width-modulated (PWM) with a carrier frequency of about several kHz to several tens of kHz. Switching noise having a frequency component of 10 kHz or more is generated from the power converter.
[0003]
In recent years, various legal regulations have been put on power converters in order to suppress the adverse effects of components above 100 kHz on frequency components of the switching noise on external devices. In order to comply with such regulations, a noise filter for a power converter is installed in the power converter.
[0004]
As this type of noise filter for a power converter, for example, a single reactor formed by winding an electric wire around a core made of ferrite, an amorphous alloy, a crystal alloy, etc., and a single capacitor made of a film, a chip, etc. are reversed. A noise filter connected to an L shape is known.
[0005]
Switching noise generated by the switching operation of the semiconductor switch element is filtered by such a noise filter, but the reactor used as this type of noise filter is generally toroidal, and the capacitor is a pin insertion type. Since it has a shape such as a flat shape or a cylindrical shape, when these are mounted on a printed circuit board inside the power converter, there is a problem that a mounting space larger than each volume is required. Further, when this type of noise filter is mounted by individual wiring, there are many connection points, and there is a problem that the fixing method of individual parts becomes complicated.
[0006]
In order to solve this problem, a noise filter made of a metal wire processed into a spiral shape or a hoop shape has been proposed.
[0007]
[Problems to be solved by the invention]
However, in the present invention, it is necessary to ensure a sufficient AC insulation breakdown voltage (Break Down Voltage) (hereinafter referred to as “BDV (AC)”). Specifically, BDV (AC) needs to ensure AC 3000 V, but the proposed noise filter cannot satisfy such a requirement. In particular, there is no noise filter using a small dielectric sheet having a high dielectric constant and a small thickness, and BDV (AC) satisfies AC 3000V. Further, the conventional manufacturing method is complicated, not practical, and has a problem in terms of cost.
[0008]
The present invention has been made to solve the above problems, and an object of the present invention is to provide a small and thin noise filter having a high dielectric constant and a high BDV (AC). Another object of the present invention is to provide a noise filter with a low manufacturing cost.
[0009]
[Means for Solving the Problems]
The noise filter of the present invention is a noise filter for filtering switching noise generated in association with the switching operation of the semiconductor switch element constituting the power converter, and has BaTiO ₃ as a main component and BaSnO ₃ as a subcomponent. Further , it contains Al ₂ O ₃ as an additive , or contains BaTiO ₃ as a main component , contains BaZrO ₃ and CaTiO ₃ , and further contains Ba (Zn _x , Nb _1-x ) O ₃ (x = 0). .4 to 0.8), a conductor is disposed on both sides of a dielectric sheet having a thickness of 100 μm to 1 mm and an AC insulation withstand voltage of 3000 V or more. The sheet and the conductor are integrated to form a circuit having both the function of an inductor and the function of a capacitor. The current of the main circuit of the power converter is passed through one of the conductors, and the other of the two conductors is connected to a ground wire and flows through the dielectric sheet from the one conductor It is characterized in that a current based on noise is guided to the ground.
[0010]
Here, the dielectric ceramic may be a dielectric ceramic containing BaTiO ₃ as a main component, BaSnO ₃ as a subcomponent, and further containing Al ₂ O ₃ as an additive in a range of 1 to 6 mol%. .
[0011]
The dielectric ceramic is mainly composed of BaTiO ₃ , contains BaZrO ₃ and CaTiO ₃ , and further contains Ba (Zn _x , Nb _1-x ) O ₃ (x = 0.4 to 0.8) as an additive. The dielectric ceramic may be contained within a range of 0.5 to 6 mol%.
[0012]
Here, the circuit having both the function of the inductor and the function of the capacitor can have a spiral shape.
[0013]
Two or more noise filters may be connected in series.
[0014]
Alternatively, two noise filters may be used as one set, and two or more sets may be connected in parallel.
[0015]
According to the present invention, BDV (AC) can be improved by improving the composition of conventional BaTiO ₃ ceramics having a high dielectric constant that has been used for dielectric sheets. This effect is due to the improvement of the BDV (AC) of the entire ceramic by filling the grain boundary between the BaTiO ₃ particles with an additive having a low dielectric constant but high BDV (AC). is there.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the member which has the same function was attached | subjected and represented with the same code | symbol.
[0017]
FIG. 1A shows the appearance of the noise filter, and FIG. 1B shows a cross-sectional view of the noise filter taken along the line AA in FIG.
[0018]
1 (a) and 1 (b), reference numeral 2 denotes a dielectric sheet, which in the present invention is made of BaTiO ₃ ceramics. The BaTiO ₃ ceramics will be described later.
[0019]
The thickness of the dielectric sheet 2 is preferably in the range of about 100 μm to 1 mm, and particularly preferably in the range of 0.5 to 0.9 mm.
[0020]
On one surface (front surface) of the dielectric sheet 2, an inductor conductor 1 having a spiral pattern having the function of an inductor and a capacitor is formed. The inductor conductor 1 has a function of passing a current of a main circuit (for example, a circuit of a power converter). The inductor conductor 1 may have a two-layer structure in which a spiral coil pattern and a punched coil having the same shape as the coil pattern are soldered. In this structure, the punched coil has a function of passing a current. Have.
[0021]
On the other surface (back surface) of the dielectric sheet 2, a grounding conductor 3 is formed at a position facing the inductor conductor 1. The grounding conductor 3 is joined to the lead wire at both ends, and has a function of passing a noise component current. Here, the “noise component current” refers to a noise component current that flows in the main circuit pattern in the inductor conductor 1 and flows into the ground conductor 3 through the dielectric sheet 2.
[0022]
The dielectric sheet 2 may be previously formed with through holes (not shown) used for positioning and fixing the noise filters when a plurality of noise filters are stacked.
[0023]
When a plurality of the noise filters 10 are stacked, the ends of the inductor conductors of each noise filter are connected in series, and the two unconnected ends are used as electrical input / output terminals. Can do. Similarly, a grounding conductor can be connected and used in series. However, when a plurality of noise filters are stacked, an insulating sheet is sandwiched between the noise filters.
[0024]
FIGS. 2A to 2C are perspective views conceptually showing the configuration of a noise filter for a power converter that uses four noise filters laminated, and FIGS. 2A and 2C are magnetic bodies. It is a perspective view which shows the external appearance of a division | segmentation core, (b) is a perspective view which shows the state which laminated | stacked four noise filters.
[0025]
As shown in FIG. 2 (b), the noise filter 10 has a through hole 11 formed in advance in the center portion, and is used for mutual fixation when the noise filters are stacked. The laminated noise filter is sandwiched from above and below using a magnetic material split core 4a shown in FIG. 2A and a magnetic material split core 4b shown in FIG. 2C, and sealed with a polymer resin material or the like. As a result, the four noise filters 10 are accommodated in a single housing. In addition, positioning and fixing projections 11a and 11b are respectively formed in the central portions of the magnetic body split cores 4a and 4b. The magnetic cores 4a and 4b have a structure in which openings 12a and 12b are formed on one side in order to take out the lead wires of the input / output terminals to the outside. As a material of the magnetic body split cores 4a and 4b, for example, a ferrite core can be used.
[0026]
In the present invention, the four noise filters may be a set of two connected in series, and two of these sets may be used in parallel. As shown in FIG. 2B, the end portions of the conductors can be easily connected through the through holes 11 by making the spiral pattern of one noise filter 10 of one set into a reverse winding pattern. In this case, one end of each set is connected to an input conductor and the other end is connected to a power converter or the like. A manufacturing method using such two sets of noise filters is disclosed in Japanese Patent Application No. 9-233080, pages 10-14.
[0027]
By connecting a plurality of noise filters, the number of turns of the coil can be increased and the inductor can be improved.
[0028]
In the present invention, the dielectric sheet 2 is made of BaTiO ₃ ceramics. Such BaTiO ₃ ceramics may be two-component or three-component, but are not limited thereto. For example, the two-component system is preferably a dielectric ceramic containing BaTiO ₃ —BaSnO ₃ as a main component and containing 1 to 6 mol% of Al ₂ O ₃ . In such dielectric ceramics, BDV (AC) characteristics can be improved without lowering the dielectric constant by precipitating Al ₂ O ₃ at the BaTiO ₃ ceramic grain boundaries. Here, Sn is a shifter for shifting the Curie temperature to the low temperature side. The ratio of BaTiO ₃ and BaSnO ₃ can be appropriately selected. In the present invention, BaTiO ₃ : BaSnO ₃ = 0.95: 0.05 to 0.70: 0.3 is preferable, and It is particularly preferable that BaTiO ₃ : BaSnO ₃ = 0.75: 0.25.
[0029]
The relative dielectric constant of the BaTiO ₃ ceramics is 6000 to 7000 near the Curie temperature (about 120 ° C.). However, when dielectric ceramics composed only of BaTiO ₃ and BaSnO ₃ are used, the BDV (AC) characteristics are as follows. It becomes very low, and BDV (AC) of 3000 V or more cannot be satisfied with alternating current (AC) required for a noise filter for power conversion. If the thickness of the dielectric sheet is increased, a BDV (AC) of 3000 V or more can be achieved, but the capacity as a capacitor is reduced. In addition, the thickness of the noise filter should be as thin as possible in order to reduce the size of the noise filter.
[0030]
As a three-component system, BaTiO ₃ is the main component, BaZrO ₃ is a minor component, CaTiO ₃ is included, and Ba (Zn _x , Nb _1-x ) O ₃ is added in an amount of 0.5 to 6 mol as an additive. % Of dielectric ceramics is preferable. However, it is particularly preferable that x = 0.4 to 0.8 and x = 0.5. Here, Zr is a shifter, and Ca is a depressor for flattening the temperature characteristic of the dielectric constant near the Curie temperature. Ba (Zn _x , Nb _1-x ) O ₃ is paraelectric, and by adding it, the BDV (AC) characteristics can be improved. The proportion of BaTiO ₃ , BaZrO ₃ and CaTiO ₃ constituting the three components can be appropriately selected. In the present invention, BaTiO ₃ : BaZrO ₃ : CaTiO ₃ = 0.7 to 0.9: 0.15 0.25: is preferably 0.01 to 0.1, more _{BaTiO 3: BaZrO 3: CaTiO 3} = 0.75: 0.20: and particularly preferably 0.05.
[0031]
【Example】
Examples are described below, but the present invention is not limited to these examples.
[0032]
Example 1
Consider the case where the dielectric sheet is a two-component BaTiO ₃ ceramic. FIG. 3 shows the relationship between the addition amount and BDV (AC) and the relationship between the addition amount and the relative dielectric constant when Al ₂ O ₃ is added to 0.75BaTiO ₃ -0.25BaSnO ₃ as the dielectric ceramic. Indicates. The value of BDV (AC) to the addition amount of Al ₂ O ₃ is from left vertical axis, the value of the dielectric constant with respect to the addition amount of Al ₂ O ₃ (epsilon _r) is read from the right ordinate axis. However, the firing temperature of the dielectric ceramic is 1350 ° C.
[0033]
The specifications of the dielectric ceramics used for the dielectric sheet of the power conversion noise filter are required to satisfy a relative dielectric constant of about 3000 and a BDV (AC) of 3000 V or more as an effective value. Therefore, when the thickness of the dielectric sheet is 0.7 mm, an electric field strength of BDV (AC) 4300 V / mm is necessary, and the relative dielectric constant is 3000 or more. It can be seen from the graph of FIG. 3 that the added amount of Al ₂ O ₃ that satisfies these values may be 3 to 6 mol%. Further, if the thickness of the dielectric sheet 1 mm, BDV (AC) is required 3000 V / mm or more field strength, and since the dielectric constant must satisfy more than 3000, Al ₂ from the graph of FIG. 3 amount of O ₃ is found to be 1-6 mol%. The thickness of the dielectric sheet is appropriately selected, and according to the thickness, Al ₂ O ₃ is in the range of 1 to 6 mol% in the ceramic mainly composed of 0.75BaTiO ₃ -0.25BaSnO ₃ . It has been found that it may be added in an amount.
[0034]
Using such dielectric ceramics, a noise filter as shown in FIG. 1 was produced. Two of these were used to form two sets, each of which was mounted on a magnetic material split core as shown in FIG. From the opening of the magnetic material split core, the input / output terminals of the first set of noise filters and the input / output terminals of the second set of noise filters are drawn out by lead wires. These projecting lead terminals were solder-bonded in a surface-mounted form with pins inserted into a socket or the like of a printed wiring board to produce one mounting component integrated with the board.
[0035]
Example 2
Consider the case where the dielectric sheet is a ternary BaTiO ₃ ceramic. FIG. 4 shows the effect on BDV (AC) or relative permittivity when Ba (Zn _0.5 , Nb _0.5 ) O ₃ is added to 0.75BaTiO ₃ −0.20BaZrO ₃ −0.05CaTiO ₃ as dielectric ceramics. Indicates. The value of BDV (AC) with respect to the addition amount of Ba (Zn _0.5 , Nb _0.5 ) O ₃ is from the left vertical axis, and the value of the relative dielectric constant (ε _r ) with respect to the addition amount of Ba (Zn _0.5 , Nb _0.5 ) O ₃ is Read from the right vertical axis. However, the firing temperature is 1200 ° C.
[0036]
As described above, the specifications of the dielectric ceramics used for the dielectric sheet of the power conversion noise filter are required to satisfy a relative dielectric constant of about 3000 and a BDV (AC) of 3000 V or more as an effective value. Therefore, when the thickness of the dielectric sheet is 0.5 mm, an electric field strength of BDV (AC) 6000 V / mm is necessary, and a relative dielectric constant of 3000 or more is necessary. The addition amount of Ba (Zn _0.5 , Nb _0.5 ) O ₃ satisfying these values is 1.8 to 6 mol% from the graph of FIG. 4, and BDV (AC) of AC 3000 V or more is obtained by addition of 2 mol%. It can be seen that it can be achieved. In addition, if the thickness of the dielectric sheet is 1 mm, an electric field strength of BDV (AC) 3000 V / mm or more is required and the relative dielectric constant must satisfy 3000 or more. It can be seen that the added amount of Zn _0.5 , Nb _0.5 ) O ₃ is _{0.5 to} 6 mol%. Therefore, according to the thickness of the dielectric sheet, the ceramic containing 0.75BaTiO ₃ −0.20BaZrO ₃ −0.05CaTiO ₃ as the main component contains Ba (Zn _0.5 , Nb _0.5 ) O ₃ in an amount of _0.5 to 6 mol%. It was found that it should be added within the range.
[0037]
【The invention's effect】
According to the present invention, a small and thin noise filter having a high dielectric constant and a high BDV can be obtained. Further, according to the present invention, since it is manufactured by a simple manufacturing process, it is easy to mount and an inexpensive noise filter can be obtained. Furthermore, since a thin dielectric sheet is used in the present invention, a large capacitance can be obtained.
[Brief description of the drawings]
FIG. 1A is a schematic perspective view of a noise filter, and FIG. 1B is a cross-sectional view taken along line AA in FIG.
2A is a perspective view of a magnetic body split core, FIG. 2B is a perspective view of a noise filter, and FIG. 2C is a perspective view of a magnetic body split core.
FIG. 3 is a graph showing the relationship between BDV (AC) or relative dielectric constant of BaTiO ₃ —BaSnO ₃ ceramics and the amount of Al ₂ O ₃ added.
FIG. 4 is a graph showing the relationship between the addition amount of BDV (AC) or relative dielectric constant of Ba (Zn _0.5 , Nb _0.5 ) O ₃ in BaTiO ₃ —BaZrO ₃ —CaTiO ₃ series ceramics.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Inductor conductor 2 Dielectric sheet | seat 3 Grounding conductors 4a and 4b Magnetic body split core 10 Power conversion noise filter 11 Through-holes 11a and 11b Protrusion

Claims (6)

A noise filter for filtering switching noise generated in accordance with a switching operation of a semiconductor switch element constituting a power converter, which is composed mainly of BaTiO ₃ , BaSnO ₃ as a subcomponent, and Al ₂ as an additive. O ₃ is contained or contains BaTiO ₃ as a main component , contains BaZrO ₃ and CaTiO ₃ , and further contains Ba (Zn _x , Nb _1-x ) O ₃ (x = 0.4 to 0.8). Conductors are arranged opposite to each other on both sides of a dielectric sheet having a thickness of 100 μm to 1 mm and an AC insulation withstand voltage of 3000 V or more, and the dielectric sheet and the conductor are integrated. A circuit having both the function of an inductor and the function of a capacitor is formed, and the power is applied to one of the two conductors. A current of the main circuit of the converter is passed, and a ground wire is connected to the other of the two conductors, and a current based on the switching noise flowing from the one conductor through the dielectric sheet is guided to the ground. A noise filter characterized by that. The dielectric ceramic is a dielectric ceramic containing BaTiO ₃ as a main component, BaSnO ₃ as a subcomponent, and further containing Al ₂ O ₃ as an additive in a range of 1 to 6 mol%. The noise filter according to claim 1. The dielectric ceramic contains BaTiO ₃ as a main component, BaZrO ₃ and CaTiO ₃ , and Ba (Zn _x , Nb _1-x ) O ₃ (x = 0.4 to 0.8) as an additive is 0. The noise filter according to claim 1, wherein the noise filter is a dielectric ceramic contained within a range of 5 to 6 mol%.   The noise filter according to any one of claims 1 to 3, wherein the circuit having both the function of the inductor and the function of the capacitor has a spiral shape.   Two or more noise filters according to any one of claims 1 to 4 are connected in series.   The noise filter according to any one of claims 1 to 4, wherein two noise filters are used as one set, and two or more sets are connected in parallel.

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