WO2012084174A1

WO2012084174A1 - Electromechanical energy store, in particular for integrated circuits

Info

Publication number: WO2012084174A1
Application number: PCT/EP2011/006406
Authority: WO
Inventors: Andreas Schramm
Original assignee: Hochschule Heilbronn
Priority date: 2010-12-21
Filing date: 2011-12-15
Publication date: 2012-06-28
Also published as: DE102010055417A1

Abstract

The invention relates to an energy store for an electric circuit, in particular for an integrated circuit, comprising a piezoelectric element (2) consisting of a piezoelectric material between two electrodes. The energy store further comprises a mechanical storage element (1) which is designed and arranged such that, when an electric voltage is applied to the piezoelectric element (2), the mechanical storage element (1) is elastically deformed. Such an energy store has a higher energy density than a purely capacitive energy store and is therefore easier to integrate into integrated circuits.

Description

Electromechanical energy storage, in particular integrated circuits

Technical application

The present invention relates to an electromechanical energy collector for an electrical circuit comprising a piezoelectric element

consisting of a piezoelectric material between two electrodes and in particular in integrated circuits. can be used.

In many applications, intermediate storage of electrical energy is required. Especially in the field of integrated circuits can be energy storage with higher storage capacity, dimensioned usually suitable

Capacitors, however, due to the required

Space requirements do not fit on the chip itself, so they must be located externally. State of the art

DE 41 26 456 AI shows a high-energy storage capacitor, which is formed of a piezoelectric material as a dielectric between two electrodes. This capacitor is clamped in a mechanical version, a control of the clamping force can charge the capacitor and affect the charging and discharging time.

GB 1 370 674 A shows a in the form of a

Flywheel trained piezoelectric component, P2011 / 006406

which is used as a filter. The component is made of one or more piezoelectric layers

constructed, each between two electrodes

are arranged. US 5,925,971 A describes a piezoelectric resonator of several layers

piezoelectric material between each two

Electrodes. EP 2 273 660 A1 and DE 36 87 579 T2 disclose the use of a piezoelectric

Element as a capacitor or as electrical variablen Liehe capacity.

The object of the present invention is to provide an energy storage device for an electrical circuit, which has a high energy density for the storage and delivery of electrical energy, so that it also integrated

Circuits can be integrated.

Presentation of the invention

The object is achieved with the energy storage device according to claim 1. Advantageous embodiments of the energy storage are the subject of the dependent claims or can be found in the following description and the exemplary embodiments.

The proposed energy storage is a combination of a piezoelectric element and a mechanical storage element. The mechanical storage element is designed and

arranged that when applying an electric

Voltage to the piezoelectric element that

mechanical storage element by the deformation of the EP2011 / 006406

piezoelectric element is elastically deformed. When using this energy storage so that energy is stored on the one hand capacitive in the piezoelectric element and on the other hand mechanically in the mechanical Speieherelement. The mechanical storage ^¬ element behaves like a spring element, which absorbs energy according to the Hooke's law by elastic deformation and this mechanically stored energy upon discharge of the capacitor formed by the piezoelectric element back to the

transmits piezoelectric element, by which it is converted into electrical energy. The mechanical storage element has no piezoelectric

Function. The proposed energy storage can store at comparable dimensions more energy than a pure capacitor from the

piezoelectric material and thereby has a higher energy density. This allows for

corresponding miniaturization the use of such an energy storage as (integrated)

Component of an integrated circuit. Preferably, the mechanical storage element is adapted to the piezoelectric element or tuned to this, that the storable in the space or volume of the energy storage energy is maximized.

Preferably, therefore, the mechanical storage element and the piezoelectric element are also made of materials that are compatible with semiconductor fabrication processes. For example, as a piezoelectric

Material Si0 ₂ and / or as material for the mechanical storage element silicon or another in one 011 006406

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integrated circuit realizable material

be used.

The mechanical storage element must be there

of course an elastic deformation

allow, d. H. it must be able to expand or contract almost unhindered by the action of the piezoelectric element. The mechanical storage element is therefore preferably attached to a support only on one side or is supported only by the piezoelectric element.

The mechanical storage element may be formed, for example, as a plate-shaped or bar-shaped element, in which on a plate surface, the piezoelectric element is arranged so that upon application of a voltage to the piezoelectric element, the mechanical storage element

Exposure of the piezoelectric element expands parallel to this surface. In such a

Embodiment, it is advantageous if on the opposite side of the plate-shaped member also a similar piezoelectric element is arranged, so that the mechanical storage element by the action of both piezoelectric

Elements expands. In a further embodiment, the mechanical storage element can also be realized as a bending beam, on one side of which the piezoelectric element is mounted. By applying an electrical voltage to the piezoelectric element then takes a bending of the bending beam. 006406

Another embodiment is to arrange the piezoelectric element together with the mechanical storage element positively between two rigid carriers. Upon expansion of the piezo- electric element, the mechanical memory ^¬ element is then compressed elastically, and can thereby leave stored mechanical energy during discharge of the capacitor formed by the piezoelectric element again to the piezoelectric element which this energy then as electrical energy via the two Can feed back electrodes into the connected circuit.

A particularly high energy storage density is achieved when the spring stiffness of the mechanical storage element and the spring stiffness of the

piezoelectric element are at least approximately equal, since in this case the mechanical energy

can be transferred almost completely between the two elements.

In an advantageous embodiment of the proposed energy storage in the input filter of an inverter, in particular a matrix converter, instead of at least one previously used there

Condenser used. Of course, the energy storage device can be used in all circuit arrangements, in particular integrated circuits, in which a static and / or dynamic energy store of high energy density is required. Of the

proposed energy storage can also be used as a filter because it has an electrical filter characteristic due to its operation. Brief description of the drawings

The proposed energy store will be explained below with reference to exemplary embodiments in conjunction with the drawings again. Hereby show:

1 is a highly schematic representation of a first example of the proposed energy storage;

FIG. 2 shows a highly schematic illustration of a second example of the proposed energy store; FIG.

3 is a highly schematic representation of a third example of the proposed energy storage; and

4 shows an example of a matrix converter in which the energy store can be used.

Ways to carry out the invention

Figure 1 shows a first example of the proposed energy storage in a highly schematic representation. In this example, loading and unloading

Discharging phases of the energy storage illustrated. In this case, the energy store is composed of a plate-shaped storage element 1 and two piezoelectric elements 2, which are rigidly connected to this storage element on both sides. The electrodes of these piezoelectric elements are not shown in this and in the following figures. These

Electrodes are generally full-surface on themselves 406

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opposite sides of the piezoelectric

Element as known to those skilled in the art. In the left part of Figure 1 is the proposed

Energy storage in the discharged state shown in which no voltage is applied to the electrodes and no energy is stored. When an electric voltage is applied to the electrodes of the piezoelectric elements 2, each piezoelectric element stores electric charge Q = C * U, where C is the capacitance of the one of the electrodes with the one therebetween

piezoelectric material formed capacitor and U represent the applied electrical voltage. By applying the electrical voltage, the respective piezoelectric element 2 expands due to the inverse piezoelectric effect. This causes an expansion of the mechanical storage element 1, in this case a silicon substrate, from the length L _x to the length L ₂ , as shown by the transition from the left partial illustration to the right partial image of FIG

is illustrated. The mechanical storage element 1 can be seen as a spring element which extends from the length Li to the length L ₂ . By the supply of electrical energy via the electrodes of the piezoelectric elements 2 is thus by the elastic deformation of the storage material potential energy in the spring, ie the mechanical storage element 1, stored.

If the stored in the energy storage

Energy will be fed back into the connected circuit, so will be through the 011 006406

discharge capacitors formed piezoelectric elements, wherein the capacitance of the piezoelectric elements each emit the charge dQ = C * dU to the circuit. The potential energy of the mechanical

Memory element has at the same time a counterforce result, which upsets the respective piezoelectric element 2, since the decreasing voltage

Piezocraft reduced. The mechanical storage element 1 shortens due to the restoring force again from the length L ₂ to the length Li. The stored potential energy decreases and the piezo effect due to this force effect on the piezoelectric

Element 2 calls an electrical voltage to the

Electrodes. The potential energy is thus converted into electrical by the piezoelectric element

Energy reverted, in turn, over the

Electrodes are fed back into the circuit. This process is characterized by the transition from the right

Partial image represented in the left part of Figure 1 representation.

Figure 2 shows another Ausgestaltungs- possibility of the proposed energy storage in a schematic representation. Here, the piezoelectric element 2 and the mechanical storage element 1 are positively secured between two rigid carriers 3, as indicated in FIG.

By applying a voltage to the piezoelectric element 2, the mechanical storage element 1 is then elastically compressed and stores accordingly

mechanical energy. The carrier 3 are here

sufficiently rigid, so that they do not deform or move by the force effect. at 011 006406

Regenerating the energy stored in the energy store in the connected circuit decreases the electrical voltage at the piezoelectric element again and the restoring force of the mechanical

Memory element 1 causes a force on the

piezoelectric element. By this force, in turn, an electrical voltage is generated by the electrical energy is fed back into the circuit. The mechanical storage element may in this case be formed, for example, from an elastomeric material.

Finally, FIG. 3 shows a further example of an embodiment of the energy store in which the piezoelectric element 2 and the mechanical storage element 1 are plate-shaped

are formed and fixed on one side to a support 3. Here too, an electrical voltage on the piezoelectric element 2 causes an expansion of the

The feedback is then in the same manner as already explained in connection with the preceding examples.

In a further embodiment, the

mechanical storage element 1 is a bending beam on which the piezoelectric element 2 is mounted on one side. Again, there is a one-sided

Attachment to a support element 3, similar to

Representation of Figure 3. By applying a voltage to the piezoelectric element 2, the memory element 1 bends and thereby stores the mechanical

Energy until the electrical voltage at the piezoelectric element is reduced again. Of course, the arrangements may also differ from the illustrated examples depending on the piezoelectric effect used. It is essential for the proposed energy store that the piezoelectric element can elastically deform the mechanical storage element upon application of an electrical voltage, in order thereby to have potential

To store energy in this memory element. When reducing the electrical voltage then the stored potential energy must be transmitted through the mechanical storage element back to the piezoelectric element.

Finally, FIG. 4 shows an example of a matrix converter in which the proposed energy store can be used. The matrix converter has in a known manner a switch matrix 4 with an upstream filter 5, through which the connected network 6 is separated from the switching matrix 4. The connected to the output side of the switch matrix 4 load 7 is also schematic

indicated. In the filter 5 usually come

Film capacitors are used, as indicated in the figure. For storing higher energies with a smaller space requirement in the present example instead of the individual capacitors one

Energy storage used according to the present invention. This can be in the realization of an energy storage in silicon significantly larger energy caching than in the usual, realizable in silicon capacitors. LIST OF REFERENCE NUMBERS

1 mechanical storage element 2 piezoelectric element

3 carrier element

4 switching matrix

5 filters

6 network

7 load

Claims

claims

Energy storage for an electrical circuit ^¬ circuit, in particular for integrated circuits having at least one piezoelectric element (2) consisting of a piezoelectric material between two electrodes,

characterized,

that the energy storage additionally

mechanical memory element (1), which is designed and arranged such that upon application of an electrical voltage to the piezoelectric element (2), the mechanical

Memory element (1) is elastically deformed.

Energy storage according to claim 1,

characterized,

that the mechanical storage element (1) as

Plate is formed and the piezoelectric element (2) disposed on one side of the plate and rigidly connected thereto.

Energy storage according to claim 2,

characterized,

a further piezoelectric element (2) is arranged on an opposite side of the plate and rigidly connected thereto.

Energy storage according to claim 1,

characterized,

that the piezoelectric element (2) together with the mechanical storage element (1) between two rigid supports (3) is arranged so

that the piezoelectric element (2) the

mechanical memory element (1) upon application of an electrical voltage to the piezoelectric element (2) presses against one of the carrier (3) and thereby elastically deformed.

Energy storage according to claim 1,

characterized,

that the mechanical storage element (1) as

Bending beam is formed and the piezoelectric element (2) on one side of the

Bending beam arranged and rigidly connected to this.

Energy store according to one of claims 1 to 5, characterized

the mechanical storage element (1) and the piezoelectric element (2) consist of materials compatible with semiconductor manufacturing processes.

Energy store according to one of claims 1 to 6 in an electrical circuit, so that by applying an electrical voltage to the

piezoelectric element energy from the

Circuit for a capacitive in the piezoelectric element and on the other hand mechanically stored in the mechanical storage element and stored in the energy storage energy by discharging the capacitor formed by the piezoelectric element fed back into the circuit.

Integrated circuit with at least one

Energy store according to one of claims 1 to 7, which is integrated in the integrated circuit.

An integrated circuit according to claim 8, which

forms a converter, wherein the energy storage is connected in an input filter of the inverter.

10. Integrated circuit according to claim 8,

when the energy storage as electrical

Filter is used.