JPH0228307A - Power supply - Google Patents

Abstract

PURPOSE:To increase output or reduce size of various kinds of power supply by a method wherein a ceramic capacitor using strontium titanate ceramic is used as a member of a circuit. CONSTITUTION:Ceramic 1 of strontium titanate, lanthanum titanate, and barium titanium is used as a ceramic capacitor. This is employed in a power supply device with ceramic 1 used where relative dielectric constant is 510 to 820, dielectric loss is 0.02% or less, voltage dependence of 1kV/mm electrostatic capacity is 0.5% or less per electric field having thickness of dielectric material, and reduction ratio of electrostatic capacity at 85 deg.C with respect to the electrostatic capacity at 20 deg.C is 37% or less. Even if the dielectric constant is relatively large, the rise in temperature during use can be reduced since the high frequency dielectric loss is small; and deterioration in electrostatic capacity during electricity charging can be reduced. This enables increase in output and reduction in size of a power supply.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a power supply device, and more specifically, to a power supply device using a strontium titanate ceramic capacitor as a member of an electric circuit for high frequency oscillation, resonance or coupling. This relates to power supplies.

[Conventional technology]

For use in induction heating for wood, resin, paint 1, high frequency drying of foods, clothing, etc., high frequency sewing machines for clothing, induction heating for steel, induction hardening of steel, high frequency melting of metals, glass, etc. uses some ceramic capacitors in its power supply circuit.

Ceramic capacitors are thermally and chemically stable;
In addition to being compact, the structure of the capacitor is extremely simple, making it easy to use at high frequencies.

Ceramic capacitors usually use forsterite-based, steatite-based, magnesium titanate-based, titanium oxide-based, calcium titanate-based ceramics, etc., but these ceramics have a low dielectric constant, so they can be used as a power source to some extent. In order to secure the output, the power supply device has to be larger.

In recent years, there has been a demand for power supplies for the various uses mentioned above to be as large in output as possible or as compact as possible.

In order to meet this demand, studies have been conducted on the use of ceramic capacitors whose dielectric material is a ceramic having a high dielectric constant, such as barium titanate, as a circuit member of a power source for the various uses mentioned above. As a result, conventional high-permittivity ceramics have problems such as rapid temperature rise during use or inability to obtain power output as calculated when applying electricity, and are limited to high-frequency, low-power ranges. I had no choice but to use it. The present inventors discovered that the cause of this is that these conventional high-permittivity ceramics are ferroelectric, and by replacing them with paraelectric or less ferroelectric materials. We have found a way to overcome these problems, and based on this knowledge, we have accomplished the present invention.

[Problems to be Solved by the Invention] That is, the present invention provides a power supply device using strontium titanate ceramics as a ceramic capacitor and using the ceramic capacitor as a member of the circuit for high-frequency dielectric or high-frequency induction. In the present invention, by using strontium titanate ceramics, the temperature rise during use, which is the problem mentioned above, can be reduced, and the power output when applying electricity can be obtained close to the calculated value. We were able to achieve high output or miniaturization of various power supplies. I would like to explain these in turn.

The temperature rise during use of a ceramic capacitor can be suppressed as the high frequency dielectric loss of the ceramic is smaller.

The high-frequency dielectric loss of conventional ceramics such as forsterite, steatite, magnesium pentatitanate, titanium oxide, and calcium titanate is 0.
Those with a content of 1% or less have been put into practical use as circuit members for power supplies for the various uses mentioned above. On the other hand, ceramics need to have a high dielectric constant in order to increase the output power or downsize the power supply. It is difficult to find something comparable to ceramics, and at present, as mentioned above, we have no choice but to limit ourselves to the limited high-frequency, low-power range using high-permittivity ceramics, which have a large high-frequency dielectric loss. The present inventors have been researching strontium titanate ceramics, but
Recently, this ceramic has been developed with a high frequency dielectric loss of 0.
．． 1% or less, and by using this ceramic, we have succeeded for the first time in suppressing the temperature rise during use in the various applications mentioned above. In addition, this ceramic has a high frequency dielectric loss of 0.1% or less.
In addition, if the composition is appropriately selected, it can be reduced to 0.03% or less. Also, high-frequency dielectric loss is greatly related to the service life of the capacitor, and it is desirable that it be as small as possible. It's advantageous.

Next, I would like to explain the power output when charging.

The output of the power supply for the above various uses is proportional to the product of the square of the voltage applied to the ceramic capacitor used and the capacitance at the time of application. Therefore, in order to increase the power output, f
It is first necessary to increase the f1ift pressure. However, conventional high-permittivity ceramics have the disadvantage of a significant decrease in capacitance when electricity is applied, and due to this disadvantage, when conventional high-permittivity ceramics are used, they cannot be used within a limited high-frequency, low-power range. In recent years, it has become difficult to stay in
Regarding the various power supplies mentioned above, there is a demand for the power output voltage to be as high as possible, and due to circuit design considerations, it is often necessary to apply a voltage up to the maximum capacity of the capacitor. Improvement of the above-mentioned drawbacks has become an important issue in this field.The present inventors believe that the cause of this drawback is that conventional high dielectric constant ceramics are ferroelectric. We have found that this problem can be solved by using strontium titanate ceramics that are paraelectric or have a low degree of ferroelectricity.

In other words, with conventional forsterite-based, steatite-based, magnesium titanate-based, titanium oxide-based, and calcium titanate-based ceramics, the decrease in capacitance when electricity is applied is negligible, but the present invention The decrease in capacitance of strontium titanate ceramics when a voltage is applied, that is, the voltage dependence of the capacitance voltage is IKV/
It can be said that the dielectric constant is suppressed to 0.5% or less per am dielectric thickness, and is extremely superior to high dielectric constant ceramics such as barium titanate ceramics, which exhibit a large reduction rate in warm temperatures.

In addition, the temperature characteristics are 8 for capacitance at 20°C.
The rate of decrease in capacitance at 5° C. can be made 37% or less, and furthermore, there is almost no change in dielectric constant (or capacitance) over time, which is excellent. It is well understood that conventional high dielectric constant ceramics such as barium titanate type ceramics exhibit extremely large changes over time and are not suitable as circuit members for the various uses mentioned above.

Therefore, in the power supply device of the present invention, the dielectric constant is 5
1O~820, dielectric loss 0.02% or less, voltage dependence of capacitance IKV/m dielectric thickness per electric field 0.5% or less, and 85℃ for capacitance at 20℃
A strontium titanate-based ceramic capacitor with a capacitance reduction rate of 37% or less is used.

[Means to solve the problem]

This invention uses 20 to 35 mol% of strontium titanate.
and lanthanum titanate 5 mol% and barium titanate 60~
75 mol%, and contains at least one additive component selected from oxides of metals selected from manganese, niobium, chromium, nickel, cobalt, and iron, clayey materials, and oxides of rare earth elements. and relative dielectric constant 510~820
．． Dielectric loss 0.02% or less, voltage dependence ratio of capacitance I
Use a strontium titanate ceramic capacitor that has a KV/w dielectric thickness per electric field of 0.5% or less and a capacitance reduction rate of 37% or less at 85°C relative to the capacitance at 20°C. It is a power supply device for dielectric or induction heating.

[For production]

Even though the present invention has a relatively small dielectric constant, the high-frequency dielectric loss is also small, so the temperature rise during use can be extremely reduced, and the capacitance decreases when electricity is applied. .

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

Strontium titanate in the molar ratios shown in Table 1.

Mix lanthanum titanate, barium titanate, and necessary additives, add an appropriate amount of binder, and make a powder with a diameter of 16.5 mm.
1200℃ after pressure forming into a disc with a thickness of 1fi.
Ceramics were obtained by firing for 2 hours.

The rare earth element oxide in the additive component is added to further reduce dielectric loss, and for example, cerium oxide, lanthanum oxide, etc. are used. The amount added is usually selected within the range of 0.01 to 10% by weight.

Also manganese, diopter, chromium, and nickel.

Cobalt and iron oxides and clay substances are added as mineralizers to form a sintered body with a dense structure, and the amount added is usually in the range of 0.1 to 0.5% by weight. selected within.

These ceramics are used, for example, as a ceramic capacitor having the structure shown in FIGS. 1 and 2. In Fig. 1, terminals 2 and 2 are provided on both sides of the ceramic l.
' is fixed by means such as soldering via the electrodes 3, 3', and a synthetic resin 5 such as epoxy resin is applied over the entire surrounding area.
covered with. 4 is a connector.

A ceramic capacitor having the shape shown in FIG. 1 was processed and its characteristics were measured. The results are shown in Table 1.

Table 1 Note that the numerical values of the capacitor characteristics were determined as follows.

(a) The relative dielectric constant tan δ is a value measured under the conditions of 20° C. and 1 MHz.

(D) 1 degree characteristic is 8 for capacitance at 20℃
It is shown as the rate of decrease in capacitance at 5°C.

(c) The voltage dependence ratio is expressed as the following ratio of capacitance per electric field of 1 to 1 V applied to a dielectric thickness of 1.

As is clear from this table, the dielectric constant is 510~
820, dielectric loss is 0.02% or less, voltage dependence ratio of capacitance IKV/m per electric field of dielectric thickness is 0.5% or less, and temperature characteristic is 37% or less.

A ceramic capacitor with a high frequency peak value of 25 V and a capacitance flooOPF having a shape shown in FIG. 2 was prepared using sample 2 in this example, and a high frequency heating power source was prepared using this as a circuit member.

At an ambient temperature of 50℃, the above capacitor has 90KVA.
electric power was applied, and the rate of temperature rise was measured.

As a result, the temperature was about 2°C.

Next, the difference in characteristics between an example of the strontium titanate ceramic capacitor of the present invention and a conventional high dielectric constant ceramic capacitor, such as a barium titanate ceramic capacitor, will be explained with reference to the accompanying drawings.

In Figure 3, the horizontal axis is the voltage dependence ratio, that is, the number obtained by dividing the applied voltage (Vkν) by the thickness of the dielectric (dm■), and the capacitance!
This is a graph plotting the relationship between the two with (C) as the vertical axis.As is clear from this graph, when compared at V/d=1, the rate of decrease in capacitance of the strontium-based ceramic capacitor (A) of the present invention is It is significantly smaller than the conventional high dielectric constant barium titanate ceramic capacitor (B).

Further, FIG. 4 shows the temperature characteristics as a rate of change (rate of decrease) in capacitance at 85° C. with respect to capacitance at 20° C. While this is as high as 55% for the conventional barium titanate ceramic capacitor (B), it is about 15% for the strontium titanate ceramic capacitor of the present invention.

Furthermore, FIG. 5 is a graph showing the capacitance over time, and it shows that the change over time of the strontium titanate ceramic capacitor (A) of the present invention is greater than that of the conventional barium titanate ceramic capacitor (B). It can be seen that there are significantly fewer

As described above, in the present invention, it is possible to obtain a larger power output as a power supply, and stable output can be obtained over a long period of time.

〔Effect of the invention〕

The power supply device according to the present invention uses strontium titanate, lanthanum titanate, and barium titanate ceramics as a ceramic capacitor, and has a dielectric constant of 510 to 820.
, dielectric loss 0.02% or less, voltage dependence ratio of capacitance I
A power supply device using ceramics having an electric field of XV/m dielectric thickness of 0.5% or less and a reduction rate of capacitance at 85°C relative to capacitance at 20°C of 37% or less. In order to do this, it has become possible to increase the power output and make the power supply smaller, and it is used as a power supply device for induction heating such as high-frequency sensing and high-frequency sewing machines, or induction heating for high-frequency hardening, high-frequency melting, high-frequency welding, etc. There are huge profits.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of ceramic capacitors for high frequency dielectric heating and induction heating used conventionally and in the present invention. FIG. 3 is a diagram showing the relationship between the voltage dependence ratio and the applied voltage in an embodiment of the present invention. FIG. 4 is a diagram showing the change in capacitance with respect to temperature in the same embodiment of the present invention. FIG. 5 is a diagram showing the change in capacitance over time in the same example of the present invention. Patent Applicant: TDC Co., Ltd. Agent
Patent Attorney Pharmacist Minoru 0 shots 0 Tokyo Chuo F. Shikisha Kaisha Chuo F. 1-13-1 Nihonbashi, Nihonbashi 1-chome, T.D.-K Co., Ltd.

Claims (1)

[Claims] (1) Strontium titanate 20-35 mol%, lanthanum titanate 5 mol%, barium titanate 60-75 mol%
mol%, and contains at least one additive component selected from oxides of metals selected from manganese, niobium, chromium, nickel, cobalt, and iron, clayey materials, and oxides of rare earth elements. , relative dielectric constant 510-820, dielectric loss 0.02% or less, voltage dependence of capacitance 1KV
A strontium titanate-based ceramic capacitor was used, which has a dielectric thickness of 0.5% or less per electric field and a reduction rate of capacitance at 85°C relative to capacitance at 20°C of 37% or less. Power supplies for dielectric or induction heating.