JP2000082630A - Laminated ceramic capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive laminated capacitor with heat resistance and a large capacitor which is stable for a high DC bias voltage or a high frequency voltage. SOLUTION: This laminated ceramic capacitor is to be integrated into an electric circuit in which an electrode metallic layer and a dielectric porcelain layer are alternately laminated, and the peak of directivity for a temperature is set -50 deg.C or less, and an electric field which is 200 V/mm or more is impressed to a dielectric layer as a DC bias electric field, and alternate currents with frequencies which are 20 kHz or more are superimposed, or is a laminated ceramic capacitor to be integrated into an electric circuit in which an electric field which is 200 V/mm or more is impressed to the dielectric layer as AC field intensity. For example, ceramic containing lead elements which are 30 mol% or more in terms of PbO, especially, a compound in a perovskite structure expressed by ABO3 is used for the dielectric porcelain.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer ceramic capacitor, particularly to a multilayer ceramic capacitor used in a switching power supply and the like, and to a power supply device such as a switching power supply and a high voltage generator using the capacitor.

[0002]

2. Description of the Related Art With the miniaturization of electronic devices, the miniaturization of switching power supplies has been progressing. Although downsizing of the switching power supply is realized by downsizing of devices to be used and mounting them at high density, temperature rise due to loss occurring in each device is inevitable. Therefore, each device is required to have low loss and heat resistance. In addition, capacitors used in switching power supplies are used under severe conditions not only in a temperature environment but also in an electrical environment. That is, a high DC bias voltage, a high-frequency voltage having a large amplitude is applied, or a large ripple current flows in many cases. As a capacitor for such a switching power supply, there is a so-called metallized film capacitor in which aluminum or the like is deposited on an organic film. Dielectrics such as polyethylene terephthalate film used in this capacitor have excellent high-frequency characteristics and are stable against high electric field strength.
Since the dielectric constant is low and the capacity obtained per unit volume is small, the size is inevitably increased. Further, the equivalent series inductance and the equivalent series resistance are large and it is hard to say that the loss is low. Further, since this capacitor uses a resin film as a base material, there is also a problem in heat resistance.

As means for improving heat resistance, it is conceivable to use a laminated ceramic capacitor in which dielectric ceramics and electrode metals are alternately laminated. The conventional technology of the multilayer ceramic capacitor will be outlined.

Considering the capacitance obtained from the viewpoint of the structure of a multilayer capacitor, the capacitance increases in proportion to the electrode area and the number of layers, and increases in inverse proportion to the thickness of one dielectric layer. Since the dielectric layer cannot be extremely thin from the viewpoint of reliability, it is necessary to increase the total area of the electrodes (the product of the area of one layer and the number of stacked layers) when manufacturing a large-capacity multilayer capacitor.

[0005] On the other hand, the electrode metal is selected depending on the temperature and atmospheric conditions under which the dielectric is sintered. That is, 1
In the case of a dielectric material that must be fired in an atmosphere in the atmosphere at a temperature of 150 ° C. or more, palladium or an alloy mainly containing palladium is selected so that the electrodes do not melt and do not oxidize. However, a capacitor having a large total electrode area becomes expensive. When using a dielectric that can be sintered in a reducing atmosphere at 1150 ° C. or higher, a nickel electrode can be used,
Although the merit in terms of cost is increased, materials which do not reduce the dielectric properties, particularly the insulation resistance even when fired in a reducing atmosphere, are limited, and it is difficult to obtain a high dielectric constant. When the firing temperature is 1150 ° C. or lower, an alloy mainly composed of silver, that is, an alloy of silver: palladium = 7: 3 can be used, which is advantageous in producing a large-capacity multilayer capacitor.

[0006] Dielectric ceramic materials used for multilayer ceramic capacitors are roughly classified into two types. First
Is a paraelectric material composed of a solid solution mainly composed of calcium titanate or strontium titanate, which is known as a temperature compensation material, and does not have a ferroelectric phase transition point, that is, a Curie point even at a low temperature. Material. Second
Is a ferroelectric material mainly composed of barium titanate, which is known as a high dielectric constant material, or a lead-based relaxor mainly composed of lead magnesium niobate or zinc zinc niobate, and has a Curie point. Exists. Since a ferroelectric material exhibits a peak in dielectric constant at the Curie point, a higher dielectric constant can be obtained when the Curie point is near room temperature. At temperatures below the Curie point, the dielectric loss (tan δ) increases. From such a viewpoint, a material having a Curie point at a temperature slightly lower than room temperature is selected as the high dielectric constant material. The first-class material system has excellent high-frequency characteristics, is stable against a DC bias electric field or a high-frequency electric field having a large amplitude, and exhibits excellent characteristics even in a severe electric environment, but has a dielectric constant of at most about 300. When a capacitor having a large capacity required for a power supply circuit, for example, a capacitor of 1 μF or more, is produced, not only is the size increased, but also the number of layers increases, which increases the cost and is not practically used. On the other hand, high dielectric constant materials classified into the second class have different dielectric constants depending on their temperature characteristics, but material systems having a temperature change rate within ± 10%, which is defined as a B characteristic in JIS C6429, are not used. 20
The dielectric constant of 00 to 3000 is +3 which is defined as the F characteristic.
In a characteristic in which a temperature change of 0 to -80% is permissible, a barium titanate-based compound has a temperature of about 10,000 and a lead-based relaxor has a characteristic of 150.
A high dielectric constant of 00 to 20000 can be obtained, which is advantageous for producing a large-capacity capacitor and has been put to practical use.

Further, as a capacitor material for high voltage, a material containing (SrPb) TiO ₃ as a main component has been reported (Hirotaka Yamamoto et al., Journal of the Ceramic Society of Japan, etc.).
Vol. 97, No. 6, pp. 619-622, 1989, and JP-A-60-
189107). According to this report, the dielectric constant is 2
800, which indicates that the capacitance change is small even with respect to the DC bias voltage.

[0008]

However, when a DC bias voltage is applied to a high dielectric constant material, piezoelectricity is induced, and mechanical vibrations are induced by the superposed high frequency electric field through electromechanical coupling. . For example, when used as an input or output capacitor of a switching power supply, if this vibration resonates with the switching frequency, unnecessary ripple current flows, resulting in an increase in energy loss in the capacitor and a rise in temperature. In an attempt,
Lead-based relaxer Pb _0.94 Sr _0.05 (Mg _1/3 Nb _2/3 )
_{0.49 (Zn 1/3 Nb 2/3} ) 0.21 Ti 0.215 (Ni 1/2 W 1/2)
_A multilayer capacitor composed of a dielectric represented by _0.0425 O ₃ and silver-palladium alloy electrodes was prepared and used in the above circuit. The capacitor has an outer shape of 5 × 6 × 1.6 mm, an electrode area per layer of 20 mm ² , the number of effective layers is 20, and the thickness of one dielectric layer is 23 μm. When a DC bias voltage is not applied to this capacitor, a change in the frequency of the impedance of the capacitor is examined. As shown in FIG.
Although it exhibits LC resonance near MHz, no resonance appears at frequencies other than this frequency. However, when a DC bias voltage of 40 V was applied, unnecessary resonance was observed at around 300 kHz and around 2 MHz as shown in FIG. This unnecessary resonance is caused by the piezoelectricity induced by the DC bias voltage.
It was clarified that the surface expansion vibration and the thickness vibration of the capacitor were excited and caused by resonance at a frequency determined by the vertical and horizontal dimensions and the thickness dimension of the capacitor. Even when a DC bias voltage of about 5 V is applied, the unnecessary resonance described above is weakened.

In addition, a material having a high dielectric constant has an unavoidable property that the dielectric loss increases depending on the high-frequency electric field strength.
For example, the capacitor described above has a voltage of 0.01 V, 1 kHz.
When measured with the signal of z, the tan δ is about 0.5%, but when measured at 10 V and 1 kHz, the tan δ increases to 1.2%. Further, a capacitor using a barium titanate-based dielectric which is commercially available as the capacitor having the B characteristic described above is used.
When a multilayer capacitor of 22 μF is measured with a signal of 1 kHz, tan δ is 0.75% at 0.01 V, but 15 tan.
When V was applied, it increased to 3.5%. Incidentally, this capacitor had a dielectric thickness of 55 μm. Normal,
The switching power supply operates at a frequency of several tens to several hundreds kHz or more. In this case, the increase in tan δ due to the high-frequency electric field strength increases the loss of the circuit.

Further, a material containing (SrPb) TiO ₃ as a main component has a high firing temperature of 1220 ° C., and is not a material capable of realizing an inexpensive multilayer capacitor.

In order to solve the above-mentioned conventional problems, the present invention has heat resistance, is stable against a high DC bias voltage and a high-frequency voltage having a large amplitude, and is inexpensive and has a large capacity used for a switching power supply or the like. It is an object of the present invention to provide a multilayer capacitor and a low-loss switching power supply using the capacitor.

[0012]

In order to achieve the above object, a multilayer ceramic capacitor according to the present invention has an electrode metal layer and a dielectric porcelain layer alternately laminated, and has a peak capacitance of -50 ° C. with respect to temperature. A multilayer ceramic capacitor as described below, wherein an electric field of 200 V / mm or more is applied to the dielectric layer as a DC bias electric field and
Select from a multilayer ceramic capacitor for incorporation in an electric circuit on which an alternating current having a frequency of z or more is superimposed, and a multilayer ceramic capacitor for incorporation in an electric circuit in which an electric field of 200 V / mm or more is applied to the dielectric layer as an AC electric field strength. At least one multilayer ceramic capacitor.

In the capacitor of the present invention, it is preferable that the dielectric porcelain contains at least 30 mol% of lead element in terms of PbO.

In the capacitor of the present invention, the dielectric porcelain containing at least 30 mol% of lead element in terms of PbO is a compound having a perovskite structure represented by ABO ₃ , and the A-site element is composed of Pb or Pb. Consisting of one or more alkaline earth elements, and the B site element is Mg, Z
at least one element selected from the group consisting of n, Ni and Co, and at least one element selected from the group consisting of Nb, Ta and W;
It is preferably a dielectric porcelain made of a kind of element.

In the capacitor of the present invention,
It is preferable that the B site of the dielectric porcelain further contains at least one element selected from the group consisting of Ti, Zr and Sn.

In the capacitor of the present invention,
Dielectric porcelain converts manganese element to MnO ₂ ,
It is preferred that the content be 0.01% by weight or more and 1% by weight or less.

In the capacitor of the present invention,
Preferably, the electrode metal is silver or an alloy containing silver as a main component, or copper or an alloy containing copper as a main component. In the above, the main component refers to 50 mol% or more.

In the capacitor of the present invention,
It is preferable that the electric circuit is a circuit incorporated in at least one selected from an input filter of a switching power supply, an output filter of the switching power supply, and a snubber for removing a surge of the switching power supply.

In the capacitor of the present invention,
It is preferable that the electric circuit is a circuit incorporated in an energy storage device of a capacitor discharge high voltage generator.

In the capacitor of the present invention,
A DC bias voltage of 200 V / mm is applied to the dielectric ceramic layer.
Regarding the frequency characteristics of the impedance when the above voltage is applied, it is preferable that almost no unnecessary piezoelectric resonance is observed.

In the capacitor of the present invention,
The electric field intensity applied to the capacitor is 200 V / mm
It is preferable that it is above.

In the capacitor of the present invention,
The dielectric porcelain of the dielectric porcelain layer has a dielectric constant of 1000 to 1000.
It is preferably in the range of 4000.

According to the present invention, PbO is reduced to 30 mo.
By setting the temperature having a peak with respect to the temperature of the dielectric constant of the dielectric having a perovskite structure containing 1% or more, that is, the Curie point at -50 ° C. or less, piezoelectricity is induced even when a DC bias voltage is applied. As a result, a multilayer capacitor having no loss due to unnecessary resonance excitation can be manufactured using inexpensive electrode metal, and a large-capacity power supply capacitor can be realized at a practical price. This makes it possible to reduce the size of the power supply circuit and improve the reliability of heat resistance.

[0024]

Embodiments of the present invention will be described below in more detail.

As the dielectric ceramic of the multilayer ceramic capacitor of the present invention, the lead element is converted to PbO by 30 mol%.
A dielectric material, particularly a porcelain composition composed of a compound having a perovskite structure represented by ABO ₃ is used, and a peak of the dielectric constant with respect to a temperature change is present at −50 ° C. or less.

Among the compounds having a perovskite structure, the dielectric ceramic of various compositions in which the lead element is located at the A site in the composition formula represented by ABO ₃ , and the ratio of silver to palladium is 70/30. A multilayer capacitor using an alloy as an internal electrode was prepared. The characteristics of these capacitors are set such that the DC bias voltage is set to 0 to 40 V, the frequency of the measurement signal is 1 kHz to 1 MHz, and the effective voltage is 0.01 to 10 V.
Was applied and evaluated.

Among the multilayer capacitors prepared using various compositions, Pb (Mg _1/3 Nb _2/3 ) which is a ferroelectric substance having a perovskite structure having a Curie point higher than −50 ° C. as a dielectric ceramic ) O ₃ (−8 ° C.), Pb (Z
n _1/3 Nb _2/3 ) O ₃ (140 ° C.), PbTiO ₃ (490
C) as a first group of compounds, and Pb (Ni _1/3 Nb _2/3 ) O ₃ (−120) having a Curie point of −50 ° C. or lower.
_{℃), Pb (Co 1/3 Nb} 2/3) O 3 a (-70 ° C.) second
Group of compounds that reduce the Curie point of ferroelectrics
b (Mg _1/2 W _1/2 ) O ₃ , Pb (Co _1/2 W _1/2 ) O ₃ ,
Pb (Ni _1/2 W _1/2 ) O ₃ and Pb (Zn
_1/2 W _1/2 ) O ₃ as a third group of compounds, a solid solution of the first group of compounds and the second or third group of compounds, or a first group, a second group and a third group of compounds. When a composition having a Curie point of −50 ° C. or less was used as a solid solution of the compounds of the group, characteristics having a dielectric constant of 1000 or more and a tan δ at 1 kHz of 0.1% or less were obtained. . In these capacitors, even when a DC bias voltage of 200 to 3000 V / mm is applied to the dielectric layer and the frequency characteristics of the impedance are evaluated, unnecessary resonance is hardly observed, and there is no piezoelectric resonance induced by the DC bias. However, it was confirmed that there was no problem in practical use. In these capacitors, the electric field strength of the measurement signal is set to 200 to 80.
Even if the voltage was increased to 0 V / mm, the increase in tan δ was small, and a capacitor with small loss was realized.

The composition of the dielectric material is not limited to the above-mentioned combination of the first to third groups.
(TiZr) O ₃ , Pb (TiSn) O ₃ , Pb ｛(Mg
_1/3 Nb _2/3 ) Ti｝ O ₃ , Pb ｛(Mg _1/3 Ta _2/3 ) T
A solid solution having a Curie point at −50 ° C. or higher, such as i｝ O ₃ , may be used. Further, part of Pb is converted to Ca, Sr, B
A solid solution whose Curie point has been reduced by substituting with the alkaline earth metal of a may be used. Furthermore, it has been found that the addition of 1% by weight or less of MnO ₂ is effective for improving the insulation resistance of the dielectric ceramic and reducing the low frequency tan δ.

FIG. 2 shows a circuit diagram of a switching power supply using the capacitor of the present invention. FIG. 3 shows the main part current waveform. This switching power supply is called a step-down converter. The electric energy input from the DC power supply 21 is converted into AC by the switching element 23 being repeatedly turned on and off after being smoothed by the input capacitor 22, and the diode 24, the choke 25, rectified and smoothed by the output capacitor 26. The output voltage output to the load circuit 27 is adjusted by the ratio between the ON time and the OFF time of the switching element 23. Although omitted in the figure,
This switching power supply has a function of monitoring an output voltage and adjusting the on / off ratio for stabilization. The series circuit of the resistor 28 and the capacitor 29 is connected to both ends of the switching element 23 and suppresses generation of a surge voltage at the time of switching. The capacitor according to the embodiment of the present invention includes:
It can be used for at least one of the input capacitor 22, the output capacitor 26, and the snubber capacitor 29. For example, if the switching frequency is 300 kHz, the input DC voltage is 36 to 72 V, and the output DC voltage is 10 V, a maximum of 72 V is applied to both ends of the input capacitor 22 and the snubber capacitor 29, and a DC bias voltage of 10 V is applied to both ends of the output capacitor 26. A high frequency ripple current as shown in FIG. 3 flows through each capacitor. In other words, 300
A high frequency electric field of kHz is superimposed. If the capacitor has a piezoelectric vibration near 300 kHz, an unnecessary resonance current flows inside the capacitor in resonance with the switching frequency, the ripple voltage and the loss increase, and the operation as if the apparent capacitance was significantly reduced. I do. However, such a phenomenon does not occur in the capacitor of the embodiment of the present invention. Further, the feature that the capacitance of the capacitor is less fluctuated by the DC voltage has an effect of facilitating the design of the switching power supply. Generally, it is desired that the input / output ripple voltage is small as the performance of the power supply. In order to suppress the ripple voltage, the capacitance of the input and output capacitors must be large, and the equivalent series impedance must be small.
It is necessary that nδ is small and that these characteristics are stable regardless of various conditions.

Further, the capacitor according to the embodiment of the present invention was used in a capacitor discharge type high voltage generator for engine ignition. FIG. 4 is a circuit diagram thereof. The DC input voltage from the battery 41 is converted into a voltage of 400 V by the DC-DC converter 42, and then the capacitor 43 is charged. Further, the high frequency switching of the switching element 44 causes the discharge gap 46 via the coil 45.
To be discharged. This switching frequency is about 100 kHz
100 kHz, 4
A high-frequency electric field of 00V is applied. If the capacitor 43 is a conventional capacitor in which tan δ is increased by applying a DC voltage or a high-frequency voltage, the loss is large and high energy efficiency cannot be expected. As a result, by using the capacitor of the embodiment of the present invention, 65% or more of the energy stored in the capacitor can be used as the discharge energy, and the efficiency of the same-capacity barium titanate-based B-capacitance capacitor can be used. Is greater than 40%.

In addition to the circuits shown here, the capacitor of the present invention, which is characterized in that there is no piezoelectric vibration upon application of a high-frequency electric field and the fluctuation of capacitance is small, is useful for a timer circuit for setting a time constant. It is.

[0032]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples.

The dielectric ceramic raw material used for the multilayer capacitor was prepared as follows. First, high purity (99%
PbO, MgO, ZnO, NiO, CoO, N
_{b 2 O 5, Ta 2 O} 5, WO 3, TiO 2, ZrO 2, S
nO ₂ , CaCO ₃ , SrCO ₃ , BaCO ₃ and M
nO ₂ was weighed according to the composition shown in Table 1, mixed in a 500 ml polyethylene container with stabilized zirconia having an average diameter of 5 mm together with pure water for 17 hours, dried, placed in an alumina crucible, and temporarily placed at 750 ° C. for 2 hours. Baked.
The calcined powder was ground in the same container in the same manner for 17 hours, and dried to obtain a dielectric material. The raw material powder is granulated by adding an aqueous solution of polyvinyl alcohol, and molded into a disk having an average diameter of 13 mm and a thickness of about 1 mm.
Calcination was carried out at ℃ for 1 hour. Cr-Au electrodes were vapor-deposited on both surfaces of the obtained sintered compact disk, and the capacitance and its temperature change were measured to determine the dielectric constant and Curie point of the material. Table 1 shows the measurement results. In addition, the measurement was not performed below -70 degreeC.

Next, a method for producing a multilayer capacitor using these materials and an evaluation method will be described. First, polyvinyl butyral is used as a binder in the raw material powder.
10% by weight and 2 to 5% by weight of butylbenzyl phthalate as a plasticizer were added and mixed with a solvent to form a slurry. A sheet of 20 to 40 μm was formed from the obtained slurry on a polyethylene terephthalate film by a doctor blade method to obtain a green sheet. This green sheet was cut, and 3 to 10 green sheets from which the polyethylene terephthalate film was peeled were pressed and laminated on a metal plate. An Ag / Pd electrode paste was printed on the laminate, and after drying the paste, one green sheet was further placed thereon and laminated under pressure. Next, the previously printed electrode pattern was shifted, and an electrode paste was printed so that the electrodes could be alternately taken out of each layer. After repeating the printing and laminating steps for the required number of layers, only 3 to 10 green sheets were laminated. The laminate is cut into individual capacitors,
The temperature was raised to 600 ° C./hour to incinerate the binder.
Then, it put in a magnesia container and baked at 950-1100 ° C for 1 hour. To connect the internal electrodes of the fired capacitor, a silver paste was applied and baked at 600 ° C. for 15 minutes to form external electrodes. In the capacitor, the effective portion of the electrode has a length of 5 mm and a width of 4.2 mm, and the dielectric thickness and the number of layers are as shown in Tables 1 and 2.

[0035]

[Table 1]

[0036]

[Table 2]

The characteristics of the capacitor were evaluated by using an LCR meter. 1 kHz and 1 MHz, 0.01 Vrms. Table 3 shows the capacitance and tan δ when the signal voltage was applied.
Table 3 shows that the DC bias voltage is 1 kHz for 40 V,
0.01 Vrms. And ta when the signal voltage of
nδ, and 10 Vrms. The capacitance and tan δ when the signal voltage was applied are also shown. The BaTiO ₃ system of Comparative Example 1 was a commercially available B-characteristic capacitor, and the effective area of the electrode was 4 mm in length and 4.5 mm in width.
Also, a DC voltage of 40 V was applied as a bias voltage by an impedance analyzer, and the frequency was 1 kHz to 4 kHz.
Sweep was performed in the range of 0 MHz, and the change in impedance was measured to check for the presence or absence of unnecessary resonance. In Table 2, the case where the unnecessary resonance is clearly observed is indicated by x, the case where no unnecessary resonance is observed is indicated by ○, and the case where the slight resonance is observed but does not cause any practical problem is indicated by Δ.

[0038]

[Table 3]

FIG. 5 shows the frequency characteristics of the impedance of Sample No. 1 where the resonance was most remarkable among these capacitors. FIG. 5A shows a case where no DC bias voltage is applied, and FIG. 5B shows a case where a bias voltage of 40 V is applied. As is clear from FIG. 5, even when a DC bias electric field strength of about 3000 V / mm is applied,
The piezoelectric resonance was extremely small, and such a small resonance did not hinder practical use as a switching power supply.

Comparative Examples 1 to 6 shown in Tables 1 to 3 all have Curie points higher than -50 ° C. As a result, when a DC bias voltage is applied, unnecessary resonance is observed, and a large-capacity capacitor for a power supply is used. This is not preferable. Further, the capacitors of Comparative Examples 1 to 6 were 10 Vrms. It can be seen that the increase in tan δ at the signal voltage is large, which is not preferable for use at a high AC signal voltage. Further, Comparative Examples 2, 3,
Each of the capacitors 4 has a large decrease in capacity when a bias voltage is applied, and therefore requires a larger capacity capacitor when used with a bias voltage applied.

In contrast to the capacitors of the comparative examples, in the capacitor of the present embodiment, whether the unnecessary resonance when the bias voltage is applied is within a range where there is no practical obstacle even if observed.
No observations were made. In many of the capacitors of this example, tan δ at 1 MHz was small, and even when a high AC signal voltage was applied, tan δ increased slightly. That is, it was confirmed that the capacitor of the present example exhibited excellent characteristics as a switching power supply to which a DC voltage was applied or a high-frequency ripple current flows, or as a capacitor for a high-voltage generating circuit used at a high-frequency high frequency. .

It should be noted that, other than the compositions shown in Table 1 of the examples, firing can be performed at 1150 ° C. or less, and if a dielectric composition having a Curie point of −50 or less is used, the DC bias voltage or the high An inexpensive multilayer capacitor in which the loss does not extremely increase with respect to the alternating current having the amplitude can be obtained.

[0043]

As described above, according to the present invention, PbO is 3
By setting the temperature having a peak relative to the temperature of the dielectric constant of the dielectric having a perovskite structure containing 0 mol% or more, that is, the Curie point to -50 ° C or less, piezoelectricity is induced even when a DC bias voltage is applied. As a result, a multilayer capacitor having no loss due to unnecessary resonance excitation can be manufactured using inexpensive electrode metal, and a large-capacity power supply capacitor can be realized at a practical price.
This makes it possible to reduce the size of the power supply circuit and improve the reliability of heat resistance.

[Brief description of the drawings]

1A and 1B are diagrams showing impedance characteristics of a conventional capacitor.

FIG. 2 is a circuit diagram of a switching power supply using a capacitor according to an embodiment of the present invention.

3 is a main part current waveform diagram of FIG. 2;

FIG. 4 is a circuit diagram of a high-voltage generator using a capacitor according to an embodiment of the present invention.

5A and 5B are diagrams showing impedance characteristics of a capacitor according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 21 input DC power supply 22 input capacitor 23 switching element 24 diode 25 choke 26 output capacitor 27 load circuit 28 resistor 29 snubber capacitor 41 input DC power supply 42 DC-DC converter 43 capacitor 44 switching element 45 coil 46 discharge gap

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Koji Yoshida, Inventor 1006, Kazuma, Kadoma, Osaka Prefecture, Matsushita Electric Industrial Co., Ltd. 72) Inventor ▲ Yabu ▼ No. 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (12)

[Claims] 1. A multilayer ceramic capacitor in which electrode metal layers and dielectric porcelain layers are alternately laminated, and a peak of capacitance with respect to temperature exists at -50 ° C. or less, wherein a DC bias electric field is applied to the dielectric layer. A multilayer ceramic capacitor to be incorporated in an electric circuit in which an electric field of 200 V / mm or more is applied and an alternating current of a frequency of 20 kHz or more is superimposed, and an electric field in which an electric field of 200 V / mm or more as an AC electric field strength is applied to the dielectric layer. A multilayer ceramic capacitor comprising at least one multilayer ceramic capacitor selected from multilayer ceramic capacitors to be incorporated in a circuit. 2. The multilayer ceramic capacitor according to claim 1, wherein the dielectric ceramic of the dielectric ceramic layer contains a lead element in an amount of 30 mol% or more in terms of PbO. 3. The dielectric porcelain of said dielectric porcelain layer has a manganese element of not less than 0.01% by weight in terms of MnO _2.
The multilayer ceramic capacitor according to claim 2, wherein the content of the multilayer ceramic capacitor is less than or equal to% by weight. 4. The multilayer ceramic capacitor according to claim 2, wherein the metal of the electrode metal layer is silver, an alloy mainly containing silver, copper, or an alloy mainly containing copper. 5. The lead element is converted to PbO by 30 mol.
1% or more is a compound having a perovskite structure represented by ABO ₃ , wherein the A-site element is Pb
Or Pb and one or more alkaline earth elements,
The B-site element is a dielectric porcelain composed of at least one element selected from the group consisting of Mg, Zn, Ni and Co and at least one element selected from the group consisting of Nb, Ta and W. Item 3. The multilayer ceramic capacitor according to Item 2. 6. The dielectric ceramic according to claim 1, wherein the manganese element is Mn.
The multilayer ceramic capacitor according to claim 5, wherein the content is 0.01% by weight or more and 1% by weight or less in terms of O ₂ . 7. The method according to claim 7, wherein the B site of the dielectric porcelain further includes T
The multilayer ceramic capacitor according to claim 5, comprising at least one element selected from the group consisting of i, Zr, and Sn. 8. The dielectric ceramic according to claim 1, wherein the manganese element is Mn.
The multilayer ceramic capacitor according to claim 7, wherein the content is 0.01% by weight or more and 1% by weight or less in terms of O ₂ . 9. The multilayer ceramic capacitor according to claim 7, wherein the electrode metal is silver, an alloy mainly containing silver, copper, or an alloy mainly containing copper. 10. The multilayer ceramic capacitor according to claim 1, wherein the electric circuit is a circuit incorporated in at least one selected from an input filter of a switching power supply, an output filter of the switching power supply, and a snubber for removing a surge of the switching power supply. . 11. The multilayer ceramic capacitor according to claim 1, wherein the electric circuit is a circuit incorporated in an energy storage device of a capacitor discharge high voltage generator. 12. The multilayer ceramic capacitor according to claim 1, wherein the dielectric ceramic of the dielectric ceramic layer has a dielectric constant in a range of 1000 to 4000.