RU2593456C2 - Method to control capacity of electric capacitor and variable capacitor based thereon - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: method to control capacity of electric capacitor and variable capacitor on the basis of this method relates to radio electronic industry and can be used in capacitor engineering. According to invention the change in capacitance is achieved by blocking the field of one of its plates, for this purpose control electric field is created between a locked plate and a control grid located between plates, opposite to the main capacitor field; and regulation of capacitance is achieved by increasing or decreasing control electric field intensity.

EFFECT: technical result is wider range of capacitance change of electric capacitors with any dielectric material as well as higher efficiency and effectiveness of the control field.

2 cl, 5 dwg

Description

The invention relates to the electronics industry and can be used in capacitor manufacturing.

Variable capacitors are widely used in radio engineering, automation, control and control systems, and electric power generators. Fundamentally, methods for controlling the capacitance of a capacitor are based on changing the area of its plates, the distance between them and the dielectric constant of the used dielectric material, or a combination thereof, and are carried out mechanically (variable and tuning capacitors), electrically and using non-linear elements (variconds, varicaps).

At the same time, variconds increase capacity with increasing voltage on the plates. In varicaps and their analogues on MIS structures (metal-dielectric-semiconductor), the dependence of the width of the pn-junction transition on the applied voltage is used to change the capacitance: with increasing voltage, the capacitance decreases due to an increase in the width of a homogeneous or heterogeneous transition. The use of both varicaps and variconds in capacity control circuits requires the application of a special additional bias voltage. Varicaps have a lower quality factor compared to variconds, but greater capacitance stability and lower losses at high frequencies (see A. Gorshkov “Variable Capacitors” // Radio, 1947, No. 1; A. Kocherov, “Electric Capacitor "//" Big Soviet Encyclopedia ", Moscow: Soviet Encyclopedia, 1969-1978; Zherebtsov IP Fundamentals of Electronics. L.: Energoatomizdat, 1985, p.137-138, 150-151).

Known methods for controlling the absolute capacitance of an electric capacitor with a change in the average dielectric constant of the capacitor dielectric by polarizing a part of the dielectric in the direction of the main field of the capacitor or perpendicular to it, for which a special control electric field is applied to this part of the dielectric, as well as bypassing the part of the dielectric of the capacitor (see " Ferroelectric varicond with integrated DC current blocking devices ", EA patent No. 003062 B1, IPC ⁷ H01L 29/93, 1998; “Variable capacitor”, ed. St. USSR No. 769650, IPC ⁴ H01G 7/00, 1984; “Method for controlling the capacitance of an electric capacitor and a variable capacitor based on this method”, RF patent No. 2443033, IPC H01G 7/00, 2010; “Method for controlling the capacitance of an electric capacitor and a semiconductor capacitor based on it”, RF patent No. 2474903, IPC H01G 7/00, 2011). A common disadvantage of variable capacitors of this class is the relatively high structural complexity and, as a rule, the small capacitance of individual capacitors.

The present invention relates to methods for controlling the capacitance of a capacitor associated with a change in the area of its plates. Including a known method in which the regulation of capacitance in a given range is carried out due to mechanical action on the movable plate or group of movable plates, by moving them relative to a fixed or group of fixed plates, while achieving a simultaneous change in the distance between the plates and the thickness of the dielectric between the plates. Upon reaching the desired capacity value, the position of the plates is fixed. This method is industrially implemented in tuning capacitors and variable capacitors (see AP Gorshkov “Variable Capacitors” // Radio, 1947, No. 1; “Variable Capacitor”, ed. St. USSR No. 1199, IPC ⁶ H01G 5/06, 1924).

The main disadvantage of this method is the need to transfer mechanical effects on the movable plate, the complexity of the design, the use of expensive materials and precious metals in the manufacture. Therefore, devices that implement it are characterized by high metal consumption, complexity of construction and they are difficult to miniaturize.

The most structurally close to the claimed invention is a method of regulating the capacitance of the capacitor charge, including changing the capacitance to a predetermined value, for which an additional continuously acting electric field is created in the dielectric between the capacitor plates, and the capacitance is changed by decreasing or increasing the field strength, and upon reaching the specified value capacitance field strength is kept unchanged. An additional electric field is created by performing a part of the medium between the plates of the conductive capacitor by introducing an additional conductive electrode into the space between the plates, which is connected to a source of a regular electric field to increase or decrease the potential of the conductive medium, and an additional field is created in the form of an electric field by connecting an additional conductive electrode with DC source (“Method for controlling the capacitance of a capacitor charge”, patent R №2034348, IPC H01G 7/00, 1987).

The essence of this method, as described, is to reduce the effective area of the plates by inducing charges on their surface caused by the electrostatic field of the additional electrode. Since these charges are bound by the charge of the additional electrode, according to the author of the invention, this reduces the ability of the capacitor to accumulate the main charge under the action of the main field, that is, its main capacity decreases.

The disadvantage of this, selected as a prototype of the method is the insufficient range of capacitance and low efficiency of the control additional field. This is due to the fact that since the additional electrode is not galvanically connected to the plates, it has a negligible intrinsic capacitance and a high voltage will be required to charge it.

The objective of the invention is to expand the capabilities of the electrical method for controlling the capacitance of a capacitor in terms of increasing the range of variation of the capacitance of capacitors with any dielectric, increasing the cost-effectiveness of controlling capacities and the effectiveness of the control field.

The solution of the problem of controlling the capacitance of an electric capacitor is that the change in the capacitance of the capacitor is achieved by blocking the field of one of its plates, for which a control electric field is created between the locked plate and the control grid located between the plates, opposite to the main field of the capacitor, and the capacitor is regulated increase or decrease in the intensity of the control electric field.

The physical content of the indicated blocking of the capacitor plate consists in the complete or partial interruption of the capacitive coupling between the plates. In this case, in the case of a complete blocking of one cover, the total capacitance of the capacitor will be minimal and equal to the capacitive coupling between the control grid, the area of which is much smaller than that of the cover, and the other cover. And with partial blocking, when the control field is less than the blocking value, the total capacitance of the capacitor, as a function of the magnitude of the control field, will be in the range from minimum to full, equal to the capacity between the blocking plate connected to the control grid and another plate.

We show it mathematically. From a physics course (see Yavorsky B.M., Detlaf A.A. Handbook of Physics. M.: Nauka, 1974. p. 356-372; Savelyev I.V. Course in General Physics. St. Petersburg: Lan, 2008. p. 54-57, 84-91; Landsberg G.S. (ed.) Elementary textbook of physics. T2. M .: Fizmatlit, 2008. p. 33-41, 71-91; Bessonov L.A. Theoretical foundations of electrical engineering M.: Higher School, 1967. p.578), the following is known.

The capacitance of a flat capacitor C is equal to:

$$C=\epsilon {\epsilon }_{\mathrm{about}}S/d,\left(\mathrm{one}\right)$$

where S is the area of each plate or the smaller of them, d is the distance between the plates, ε _о is the electric constant, ε is the dielectric constant (relative) of the substance located between the plates. In this case, filling the space between the plates with a dielectric increases the capacity by a factor of ε.

It is also known that the field inside the charged hollow conductor is absent. Thus, if the plates of a flat capacitor are connected and one common potential is applied to them, then the field between the plates will be zero, the charges will be located on the outer sides of the plates, the field will be directed outward from the plates of the capacitor. At the same time, the fields of the plates mutually block each other.

The condition of this state can be written as:

$$E_{\mathrm{one}}={\mathrm{<figure-callout\; id="2"\; label="E"\; filenames="00000007.png"\; state="\{\{state\}\}">E</figure-callout>}}_2,\left(2\right)$$

where E ₁ and E ₂ are the electric field strengths at the 1st and 2nd capacitor plates, respectively.

Now we will complicate the experiment by replacing one of the plates, say the 1st, with an electrode in the form of a grid. Neglecting the uneven distribution of charges on the grid, at a strength E _C , for a fairly rare grid, we obviously get:

$$E_{\mathrm{FROM}}<{\mathrm{<figure-callout\; id="2"\; label="E"\; filenames="00000007.png"\; state="\{\{state\}\}">E</figure-callout>}}_2.\left(3\right)$$

Physically, this will mean the penetration of part of the field of the 2nd lining through the grid. This can be prevented if we form a counter flow of the control field intensity E _У equal to or greater than the difference in the intensity flows from inequality (3):

$$E_{\mathrm{At}}\ge E_2-E_{\mathrm{FROM}}.\left(\mathrm{four}\right)$$

For this purpose it is necessary to submit to the control grid and 2nd plate of a corresponding control voltage U _U:

$$U_{\mathrm{At}}=E_{\mathrm{At}}\cdot d_{\mathrm{FROM}2},\left(5\right)$$

where d _C2 is the distance between the control grid and the 2nd lining. It is clear that the smaller d _C2 , the more effective the action of the control voltage U _U.

We extend the foregoing to the proposed three-electrode flat capacitor.

Figure 1, 2 shows a design variant of a capacitor of variable capacitance that implements the proposed method for controlling the capacitance of a capacitor.

The device contains dielectric 4-coated plates 1, 2, designed to create the main field of the capacitor, and located between the control grid 3, which serves to form the control field. The control grid 3 and the lining 2 are connected to different poles of the adjustable voltage source 5.

In this case, the dielectric 4 can be any, including various types in different areas of the interelectrode space.

The operation of the device are as follows.

When U _Y = 0, the flux of the main field strength is maximum, and therefore, the capacitance of the capacitor is also maximum (see Fig. 3). Most of the flow of tension falls on the capacitor plates, a smaller part of it is intercepted by the grid.

When the blocking value U _Y = U _Uzap , determined from the conditions (4, 5), the flux of the main field strength is minimal and is reduced to the flux of tension between the lining 1 and the grid 3 (see figure 5). Accordingly, according to expression (1), the capacitance of the capacitor is also minimal, since the grid area is much smaller than the area of the plates.

The intermediate values of U _U , from 0 to U _Uzap , correspond to the intermediate values of the capacitor C, from the capacitance between the lining 1 and the lining 2 connected to the grid 3: C _{1 (2 + С)} to the capacitance between the lining 1 and the grid 3: C _1C (see figure 4). Moreover, with an increase in the absolute value of the control voltage, the capacitor capacitance decreases.

Also note that to increase the efficiency of the control voltage, it is necessary to bring the grid as close as possible to the shielded cover, and to increase the range of capacity regulation, make the grid as rare as possible.

The capacitor capacitance is controlled as follows.

Applying to the plates 1, 2 of the capacitor in the General case, the changing operating voltage U _p (t), get the main working field intensity, in the General case, E _p (t). A control field of intensity E _y between the control grid 3 and the lockable cover 2 is created by applying to them a control voltage U _y supplied from the regulated voltage source 5.

The capacitance of the capacitor is controlled by increasing or decreasing the control field strength by changing the value of the control voltage U _y . Upon reaching the specified value of the working capacitance C _{p of the} capacitor, the control field intensity is kept unchanged.

Consider an example of a practical implementation of the device.

In the particular case of using vacuum as a dielectric, it is easy to see that we obtain a long and well-known tube triode, with the exception of the cathode heating circuit, which is no longer needed. The parameters of triodes designed for various applied problems are known from the literature. In particular, to increase the steepness of the amplification characteristics, increase the input capacitance C _in , reducing the grid-cathode distance to tens of microns. And to reduce the parasitic bonds of the triode, the passage capacitance C _pr grid - anode is reduced to values that are an order of magnitude smaller than the output capacitance C of the _output triode cathode - anode (see I. Zherebtsov, Fundamentals of Electronics. L .: Energoatomizdat, 1985, p. 224- 228).

For example, for a 6N2P-EV triode with a nominal anode voltage of 250 V, the blocking voltage is -4 V, C _out = 2.5 pF, C _in = 2.35 pF, C _pr = 0.55 pF (see B. Katznelson ., Larionov A.S. Domestic receiving-amplifying lamps and their foreign analogues (reference book), Moscow: Energoizdat, 1981, p.140).

Thus, a variable capacitor constructed according to the proposed method based on a 6N2P-EV tube triode with a rated voltage of 250 V, when the control voltage changes in the range from 0 V to -4 V, gives a total decrease in the capacitor capacity by about 5 times, from an order of magnitude 2.7 pF to 0.55 pF.

A comparative analysis with close analogues and prototype shows that the proposed method for controlling the capacitance of a capacitor and a device based on it differ in a different, more universal and more economical technology for changing the effective area of the capacitor plates.

Including, from a method and device with mechanical regulation of capacitance in a given range due to mechanical action on a moving plate or group of moving plates, by moving them relative to a fixed plate or a group of fixed plates (see AP Gorshkov “Variable Capacitors” // Radio, 1947, No. 1; Variable Capacitor, ed. St. USSR No. 1199, IPC ⁶ H01G 5/06, 1924). The present invention does not require the transmission of mechanical effects and, accordingly, is devoid of the inherent disadvantages of mechanical devices: low speed, design complexity, the use of expensive materials and precious metals in the manufacture, high metal consumption, difficulties in miniaturization.

In contrast to the method implemented in the invention, “Method for regulating the capacitance of a capacitor charge” (RF patent No. 2034348, IPC H01C 7/00, 1987), in which the effect of changing the capacitance of a three-electrode capacitor is achieved by creating an additional continuously acting electric in the dielectric between the capacitor plates field using an additional conductive electrode, which is connected to a direct current source, in the proposed method, the technical effect is obtained by blocking the field of one of its plates, for which between covered with a lining and located between the lining of the control grid create a control electric field opposite to the main field of the capacitor, and the capacitance of the capacitor is regulated by increasing or decreasing the control electric field, which eliminates the disadvantages of the prototype, extends the range of capacitance, increases the efficiency of the device and the efficiency of the control field of the capacitor .

Thus, the present invention meets the criteria of "novelty" and "inventive step".

Using the proposed method for controlling the capacitance of a capacitor and a device based on it gives, in comparison with existing methods of electrical control, the following technical result:

expands the range of capacitor capacitance;

allows you to control the capacitance of a capacitor with any dielectric;

increases the efficiency of the process of controlling the capacitance of the capacitor due to the greater efficiency of the control field.

The prospects for the industrial application of the invention do not cause difficulties, since it is supposed to use existing, mastered technologies of capacitor engineering and microelectronics, and also it does not require the use of any means, materials or elements unknown to modern industry.

For example, to create variable capacitors of large capacity, the film winding technology that is widely used in the production of capacitors with organic dielectrics can be applied (see Merkulov V.I. Fundamentals of capacitor engineering. Tomsk: Tomsk PU, 2001, pp. 98-99, 108-110 )

Claims (2)

1. A method of controlling the capacitance of an electric capacitor using a control electric field generated by a control grid located between the plates, characterized in that the change in the capacitance of the capacitor is achieved by blocking the field of one of its plates, for which a control electric field is created between the locked plate and the control grid, opposite to the main the capacitor field, and a change in the capacitance of the capacitor is carried out by increasing or decreasing the voltage of the control electric i. 2. A capacitor of variable capacitance, comprising at least two plates separated by a dielectric, intended to create the main field of the capacitor, and a control grid between them, used to form a control electric field, characterized in that the control grid and one of the capacitor plates are connected to different poles of the adjustable voltage source.

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