WO2007052206A1

WO2007052206A1 - Powering an electric circuit using mechanical impact

Info

Publication number: WO2007052206A1
Application number: PCT/IB2006/053999
Authority: WO
Inventors: Alan J. Davie; Martin Ouwerkerk; Evert J. Van Loenen; Martijn Krans
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2005-11-07
Filing date: 2006-10-30
Publication date: 2007-05-10

Abstract

The invention relates to powering of an electric circuit (110, 206), and in particular to powering of the electric circuit using mechanical impact or sudden mechanical shock. A device, system and method are disclosed where mechanical impact is converted into electrical energy. In order e.g. to decrease complexity and increase the efficiency of how to provide energy for e.g. portable devices and to increase the amount of energy provided with alternative energy sources such as mechanical impact, a device, system and method using certain shapes, construction and method is provided using a first material (104, 112) and a piezoelectric material (106). In particular, e.g. at least a part of a surface (116) of the device is an impact part suited for a mechanical impact from which the piezoelectric material (106) generates electrical energy. The invention is particularly suited for a ball (102) or electronic systems like a mobile phone (202).

Description

Powering an electric circuit using mechanical impact

FIELD OF THE INVENTION

The invention relates to powering of an electric circuit, and in particular to powering of an electric circuit using mechanical impact.

BACKGROUND OF THE INVENTION

With an increasing effort to make electric circuits portable and as the number and types of portable electric circuits that comprises electronics to be powered increases, the use of batteries for powering such electric circuits become increasingly common. Powering the electric circuits with non-rechargeable batteries is one way used for providing the energy to such electric circuits but which is e.g. not environmentally optimal. Powering the electric circuits directly with alternative energy sources is another way and finally powering the electric circuits with rechargeable energy sources such as rechargeable batteries is also a common way used to power electric circuits.

When e.g. the energy needed per time unit by the electric circuit increases the use of the rechargeable energy source, such as one or more rechargeable batteries for the electric circuit, may also increase. The level of energy needed per time unit where it is appropriate to use a rechargeable energy source may in the years to come decrease. This decrease may be due to that a need to act environmentally optimal may increase and a cost of rechargeable energy sources such as batteries may decrease. A most common way of recharging energy sources such as batteries is to connect the one or more batteries via a charging circuit to a mains electricity supply. Although this method minimizes effort provided by the user, it is generally a rather slow process that requires a mains supply to be conveniently available. Another way of recharging the rechargeable energy source by a user is to provide a physical effort over a certain possibly protracted amount of time such as to wind a spring or operate a dynamo.

A way of generating electrical energy with an alternative energy source is described in Japanese patent application with the publication number 2001-186678. The electrical device in JP 2001-186678 is equipped with a pipe 7 wherein an element 4, the element 4 (or moving part) is assumed to have a relative low mass (m), rolls back and forward and hereby actuates the plate shaped piezoelectric elements PZTl and PZT2. By this actuation electrical energy is generated and the energy is led to a battery charger.

In the view of the present inventors the method applied in 2001-186678 and the build up of the apparatus disclosed in JP 2001-186678 may be improved in a number of ways. As an example the efficiency of the device may be improved and the complexity of the device may be decreased.

The present inventors appreciate that as the trend towards the use of portable electric circuits grows a need for more convenient and alternative ways of powering the portable electric circuits is needed. Furthermore the inventors of the present invention have appreciated that an improved device for powering an electric circuit using alternative energy sources and an improved method for powering an electric circuit using alternative energy sources is of benefit, and has in consequence devised the present invention.

SUMMARY OF THE INVENTION It may be seen as an object of the present invention to provide a device, system and method for powering an electric circuit using alternative energy sources. In particular, it may be seen as an object to provide a device, a system and a method for powering an electric circuit using alternative energy sources with improved efficiency and/or decreased complexity. Accordingly, in a first aspect a device for powering an electric circuit is provided. In a second aspect of the invention an electronic system is provided and in a third aspect of the present invention a method for powering an electric circuit is provided. Preferably, the invention alleviates, mitigates or eliminates one or more of the above or other disadvantages singly or in any combination. According to the first aspect of the invention there is provided a device for powering an electric circuit, the device comprising: a first material provided in physical contact with a piezoelectric material for generating electric energy connection means for connecting the piezoelectric material at least electrically to the electric circuit, wherein at least a part of a surface of the device is an impact part suited for a mechanical impact and the impact part is formed by the first material and/or the piezoelectric material and the device is adapted for generating electric energy for powering the electric circuit when providing a mechanical impact to the impact part. A device for powering the electric circuit using an alternative energy source is thus provided and which may e.g. be used when a mains supply is not conveniently available. One possible advantage by the present invention may be that the use of a rechargeable energy source for some types of electric circuits may be prevented. Another possible advantage by the present invention may be that when the rechargeable energy source is used an alternative device for recharging the energy source is provided.

One possible advantage by forming the impact part by the first material and/or the piezoelectric material may be that that only one material and possibly two materials may be used to provide a collection of the energy provided by the mechanical impact and hereby the complexity of the device is decreased.

Possibly the device may be substantially formed as one impact part. Alternatively or additionally at least an exterior surface of the device may be an impact part.

The connection means may be means such as one or more of the following means: electric wires connected to the piezoelectric material, electric wires connected to the piezoelectric material and provided with a plug adapted for at least electrical connection to the electric circuit. The electric circuit may comprise an electronic system.

The device may be adapted to be used with the electric circuit that may be powered directly by the device or the device may be adapted to be used with the electric circuit, where the electric circuit comprises a rechargeable energy source for powering the electronic system using electric energy. The electric circuit may e.g. comprise a rectifier and/or a capacitor. The electric circuit may alternatively or additionally comprise a circuit transmitting an identification signal. The electric circuit may comprise a circuit transmitting a signal useable for positioning the electric circuit. The electric circuit may comprise one or more light emitting diodes. The electric circuit may comprise rechargeable energy storage such as one or more batteries.

When, according to claim 2, the device is formed as one impact part, one possible advantage by increasing the part of the device formed as an impact part or even forming the device as one impact part or by forming at least an exterior surface of the device as an impact part may be that the complexity is decreased and/or the ability to withstand a rough handling of the device is increased and/or the efficiency of the device is increased.

When, according to claim 3, a moving part used to generate electric energy is the device, one possible advantage may be that no other moving parts than the device may be needed. When providing the device or system in accordance with the invention one possible advantage may be that electrical energy may be provided without the need for moving parts within the device, thus e.g. reducing the complexity of the device and possibly extending the lifetime of the device. In particular, one possible advantage by increasing the part of the device formed as an impact part or even forming the device as one impact part or by forming at least an exterior surface of the device as an impact part may be that a moving mass (m) used for generation of energy by the device, e.g. in a case where the device is used for charging by a drop under the influence of at least the force of gravity may be the mass (m) of the complete device. Hereby the amount of energy generated may also be increased.

The electric energy may be provided when providing the mechanical impact indirectly to the piezoelectric material trough the first material and/or when providing the mechanical impact directly to the piezoelectric material.

The first material may be a material adapted for mechanical impact and e.g. adapted in order not to be damaged by the mechanical impact. A possible advantage hereby is that the device is e.g. useable for rough handling.

The first material is preferable a material with material characteristics which may be adapted to be compatible with the piezoelectric material such as e.g. to provide a glued connection between the materials in at least some areas and/or points. When, according to claim 4, the first material and the piezoelectric material are provided in physical contact with each other by their shape and size, one possible advantage may be that a simple connection between the materials is provided. The physical contact may be present at least in some points between the materials and at least during a state when energy is not generated by the piezoelectric material. The first material and/or the piezoelectric material are preferable adapted for being formed in various forms and/or adapted to have certain material characteristics in order for the device to be attached to a electric circuit or an electronic system in a rubber band like manner. The device may be attached in this way to e.g. an electronic system to be powered and/or recharged by the device. When, according to claim 5, the first material is adapted to disperse the mechanical impact from a relative small area to an increased area a possible advantage may be that an increased area of the piezoelectric material may be activated and hereby a possible advantage may be that an increased amount of electric energy is generated. Thus possibly improving the efficiency of the device. When, according to claim 6, the first material is adapted to extend the duration that the impact activates the piezoelectric material may be a more effective energy generation because an extended or adjusted duration may be provided to fit the piezoelectric material and hereby increasing the efficiency by which efficiency electric energy is provided. The first material may be a compressible material such as a synthetic material, a rubber, a plastic, a softened plastic, a natural rubber or any other material suited to be adapted for e.g. rough handling and/or dispersing of the mechanical impact to an increased area and/or extending the duration that the impact activates the piezoelectric material. Dispersing of the mechanical impact and/or extending the duration that the impact activates the piezoelectric material may be provided by the presence of the first material.

The piezoelectric material may be one or more layers of piezoelectric material and/or one or more layers of a piezoelectric foil.

When, according to claim 7, the piezoelectric material is at least partly comprised inside the first material one possible advantage may be that the efficiency of the generation of energy by the device is increased.

Alternatively or additionally the piezoelectric material is at least partly comprised between e.g. layers of the first material. A possible advantage by comprising the piezoelectric material between e.g. layers of the first material may be that the piezoelectric material is protected against direct mechanical impact and/or the efficiency of the generation of energy by the device is increased. The increase of energy generated when using a layer construction comprising both materials or by comprising the piezoelectric material within the first material may be due to the mechanical impact being dispersed to an increased area in which energy is efficiently generated by the piezoelectric material and/or due to extending the duration that the impact activates the piezoelectric material. A user may provide the mechanical impact.

Alternatively or additionally the first material and/or the piezoelectric material is adapted to form the device. The surface of the device may be formed by the first and/or piezoelectric material and possibly the electric connection means.

When, according to claim 8, the device is adapted for protecting at least a part of the electric circuit from direct mechanical impact, or when the device is adapted for protecting at least part of an electronic system comprising the electric circuit from directly mechanical impact, a possible advantage may be that a lifetime of the electric circuit or electronic system increases. Fitting the shape of the device to at least partly extend along the electric circuit or the electronic system and hereby possibly be attached to the electric circuit or the electronic system may be an example of how to adapt the device to protect the electric circuit. Thus possibly also decreasing the complexity of the device instead of e.g. having to comprise other means for attaching the device to the electric circuit.

Adapting the device for protecting at least a part of the electric circuit from directly mechanical impact may be provided by using the impact part for protection of the electric circuit alternatively or additionally to using the first material for protecting the electrical circuit. The device may e.g. be adapted to protect at least part of the electric circuit by the impact part on at least a part of the surface of the impact part substantially following a shape of at least part of the electric circuit part or by at least part of the surface of the impact part following at least part of an electronic system comprising the electric circuit.

When, according to claim 9, the first material and/or the piezoelectric material is provided at least partly with one of the following shapes: a shape adapted for protecting at least a part of the electric circuit from directly mechanical impact, a pad shape, the shape of half a ball, a ball shape a possible advantage may be that shaped such as at least partly to enclose or cover the electric circuit or the electronic system. One possible advantage of providing a shape of e.g. the impact part with a shape of a certain radii may be that the energy generated by the piezoelectric material increases. When, according to claim 10, the device is adapted for generating electric energy by providing one or more of the following types of mechanical impact to the surface or the impact part: pressing the surface or impact part, hitting the surface or impact part, letting the surface or impact part hit a surface of the surroundings, letting an object hit the surface or the impact part, kicking the impact part one possible advantage may be that energy is efficiently generated without the need for a mains supply of electric energy.

When, according to claim 11 , the device is formed as a ball and wherein using the ball in a playing like manner generates electric energy for at least partly powering the electric circuit a possible advantage may be that a device is provided with a form where multiple mechanical impact can be easily provided. Still further, some piezoelectric materials generate energy when the material is extended and/or when the material is compressed and when providing the piezoelectric material at least partly in e.g. the ball shaped form multiple extensions and/or compressions may be provided. Possibly only a part of the electric circuit consisting of wires may be partly positioned in the ball and the wires from the ball may be connected to an electronic system outside the ball and by e.g. pressing the ball the electronic system is powered and/or recharged.

In embodiments, which will be described herein, e.g. a ball shaped device where the piezoelectric material is shaped in a ball shape is shown. It must be understood that e.g. due to manufacturing properties it may be preferred to provide e.g, strip(s) of e.g. piezoelectric foil, or strip(s) shaped as part of a substantial sphere, in stead of a complete sphere shaped piezoelectric foil in order to provide a final shape such as a ball of a device according to the invention.

When, according to claim 12, the device is provided with means for opening and closing the device and hereby the device is adapted for exchanging the electric circuit positioned inside the device one possible advantage may be that the device may e.g. be used for powering and/or recharging different electric circuits.

When, according to claim 13, the piezoelectric material for generating electric energy is polyvinylidene fluoride a possible advantage may be an increased efficiency of the device.

According to the second aspect of the invention there is provided an electronic system comprising an electric circuit.

According to the third aspect of the invention there is provided a method of powering an electric circuit, the method comprising the following steps: - providing a first material in physical contact with a piezoelectric material for generating electric energy connecting the piezoelectric material at least electrically to the electric circuit forming an impact part of the device by the first material and/or the piezoelectric material - generating electric energy for powering the electric circuit when providing a mechanical impact to the impact part.

The method may further comprise the step of adapting the device for protecting at least a part of the electric circuit from direct mechanical impact.

The electric energy may be provided when providing the mechanical impact indirectly to the piezoelectric material through the first material and/or when providing the mechanical impact directly to the piezoelectric material.

In general the various aspects of the invention and/or the possible advantages may be combined and coupled in any way possible within the scope of the invention. These and other aspects, features and/or advantages of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention will be described, by way of example only, with reference to the drawings, in which

Fig. 1 is showing a powering device in accordance with the present invention. Fig. 2 is showing a mobile phone with a powering device in accordance with the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

An embodiment of a device 102 in accordance with the present invention for powering an electric circuit is illustrated in FIG 1. The device 102 is shown in a cross sectional view. As shown in this embodiment the device 102 may be symmetric. The device 102 comprises a first material 104, 112 and a piezoelectric material 106. In this embodiment the piezoelectric material is shown as a ring. As only a cross section is shown the piezoelectric material may be provided in a spherical shape. In the shown embodiment the outer part 104 of the first material 104, 112 follows the shape of the piezoelectric material 106 or vice versa. The 104 part of the first material 104, 112 encloses the piezoelectric material 106. The ring of piezoelectric material 106 is provided around an inner part 112 of the first material 104, 112.

The piezoelectric material 106 is connected to an electric circuit 110 by connection means 108. In the shown embodiment the electric circuit comprises a rechargeable energy source 114. The exterior surface 116 of the device 102 comprises the first material 104.

The exterior surface 116 is a surface suited for mechanical impact. The mechanical impact may e.g. be a user pressing the device 102 or an object hitting the device 102. In a simple embodiment of the invention the device 102 may be referred to as a ball and the cross section shown is e.g. taken through a centre of the ball. When provided with the mechanical impact the device 102 generates electrical energy. The piezoelectric material 106 being extended in some areas and/or compressed in some areas by the mechanical impact provides the electrical energy.

The electrical energy generated is via the connection means led to the rechargeable energy source 114. The electric energy from the energy source may be provided for powering an electric circuit such as a circuit for transmitting an identification code and/or for transmitting a signal for positioning the device 102. Alternatively the electric circuit may directly use energy generated without the need for rechargeable energy storage 114.

When e.g. the device 102 is e.g. split in two parts (not shown) and provided with means for opening and closing the device (not shown) such as a hinge and/or e.g. Velcro tape provided between the parts the electric circuit may be changed and e.g. a sound- generating toy may be provided. Alternatively the electric circuit only comprises connection means 108 and connecting batteries to the piezoelectric material, closing the device 102 and generating electric energy by e.g. playing with the device (or "power-ball") may recharge various types of batteries.

When suited for mechanical impact the piezoelectric material may also be at least part of the surface 116. The piezoelectric material 106 may comprise one or more layers of a piezoelectric foil. Alternatively or additionally one of more layers of a piezoelectric material may be followed by a layer of the first material 104, 112 which is then followed by a ring or layer of one or more layers of a piezoelectric material 104, 112. The inner part 112 of the first material may be another type than the outer part 104 of the first material 104, 112.

Another embodiment in accordance with the present invention is illustrated in FIG. 2 where an electronic system 202 is shown. The electronic system 202 comprises an electric circuit 206 such as a mobile phone 206. The electric circuit of the mobile phone comprises a rechargeable battery 218 connected through connection means 210, 208 in the mobile phone and the device, respectively, to the piezoelectric material. In FIG.2 a ring 220 of piezoelectric material is provided within the device 204. More rings, each e.g. comprising one or more layers of piezoelectric material may be provided. Alternatively, the piezoelectric material may be provided as one or more layers of piezoelectric material provided in parts 222 (or plates) of a piezoelectric material or piezoelectric foil substantially following one or more sides of the device 204. The device 204 is provided for at least partly powering and/or recharging the electric circuit 206 by mechanical impact of the device 204 and hereby generating electric energy by the piezoelectric material.

The cross-section A-A 212 is shown at 216 and in an alternative 214. In the alternative 214 the device 204 is only, at least partly, enclosing four sides of the mobile phone (electric circuit 206). Another possibility is also to enclose the backside of the electric circuit 206. Still further a pocket like form of the device 204 may be provided where substantially all of the electric circuit 206 is covered by the device 204 leaving e.g. only one or more small holes in the device 204 e.g. for inserting and extracting the electric circuit 206 from the pocket formed device. Similarly only less than the described surfaces or only part of one surface of the electric circuit 206 may be covered by the device 204.

In the cross section 214 the ring 220 of the piezoelectric material such as one or more layers of a piezoelectric foil is shown in a cross-sectional view. It can be seen that the ring is positioned inside the exterior surface of the device 204. In the cross section 216 both the ring 220 and two plates 222 of a piezoelectric material is shown inside the first material. Other variations of the position and geometry of the ring and/or the plates may be provided.

Similarly to the description of FIG.1 the piezoelectric material may be at least partly surrounded by the first material.

In general, the invention is based upon using mechanical impact, or sudden mechanical shock to provide relative high levels of re-charging energy that can be generated over relative short periods of time. The invention could be incorporated into a range of more or less modified electronic devices where the power consumption requirements are generally low to moderate.

Impact energy may be provided with the assistance of gravity, such as dropping the device to be charged from a certain height above the ground. Alternatively, it may be even more advantageous to provide charging by the user "striking" or "hitting" the device, such as 102, by a convenient heavy object or weight. Elements of the device for impact charging may as described comprise an actuator for mechanical to electrical energy conversion and one or more energy storages. The actuator may comprise the piezoelectric material. The actuator converts the instantaneous energy provided by the mechanical impact into a proportional electrical output. The rechargeable battery 218 may provide energy storage. Another energy storage may be a short-term mechanical energy storage for short term storing (and/or transferring and/or dispersion and/or extending the duration that the impact activates the piezoelectric material) of the instantaneous energy provided by the mechanical impact while the impact energy travels through this short term energy storage. Such short term mechanical energy storage may be a spring member or a compressible material such as the compressible first material 104. The short-term mechanical energy storage gathers the generated energy for more gradual delivery of the impact energy to the actuator over an extended period and/or over an extended area of the actuator possibly in order to improve the efficiency of the actuator. Preferably, a device according to the invention may comprise the mechanical short-term energy storage. Another energy storage may be an electric short term energy storage, provided by e.g. a capacitor provided in electrical connection with the output of the actuator in order to gather the energy generated by the actuator and which short-term energy storage may be controlled for more gradual delivery of the electrical energy to e.g. the rechargeable batteries or other energy storage devices.

As an indication of the energies available from providing energy by gravity charging or hit charging relative to a conventional charging using a main power supply the following principle calculations may be provided.

Gravity charging.

It is assumed that the object to be charged is dropped to the ground under the force of gravity. To calculate the energy provided by such a drop we may assume a drop height of two meters (h = 2m), an object or device mass of five hundred grams (m = 50Og), gravity, g = 10 N/kg and that the efficiency of a mechanical to electrical energy converter (or transducer or actuator) such as the device according to the invention, is set to 25%.

Potential energy of the obejct equals, m x g x h = 0,5 x 10 x 2 = 10 Joules. (1)

Energy transferred to battery = 10 Joules x 25% = 2.5 Joules. (2)

For comparison, the conventional charging for a battery with a capacity, C =

500 mAH with a typical charging current, I, may equal af tenth of 500 mAH = 50 mAH. A typical voltage-drop, U, may be 1,2V in a NiMH or the like battery. The power delivered by the conventional charger is then as follows.

Power delivered by conventional charger = U x I = 5OmA x 1,2V = 60mJ/s (3)

For the conventional charger to provide the same energy as the gravity impact charging, the conventional charger needs a period of 2.5 J divided by 60mJ/s, which equals around 42 seconds.

Hit charging.

It is assumed that the weight of the object that strikes the charging device has a mass of five hundred grams (m = 50Og), the distance, d, the weight is moved is one meter (d = 1 m), the transition time over one meter, t = 0,2s and the conversion efficiency is set to 25%. The acceleration, force and energy are then as follows.

Acceleration of weight, a = (2 x D) / 1² = 2 x 1 / 0.04 = 50m/s² (4) Force impacted by weight, F = m x a = 0.5kg x 50m/s² = 25N. (5)

Energy from impact = F x d = 25N x Im x 25% = 6.25 Joules. (6)

When using the same conventional charger and battery as in the previous calculation example, the conventional charger needs 6.25 J divided by 60mJ/s = 104 seconds to provide the same energy as the hit charging.

All the calculations described here were provided on the basis of one drop or one strike with the weight. However it follows that by applying multiple drops or hits the battery could be charged incrementally.

It must be understood that the above calculations are principle calculations which may have been simplified and which have only been provided in order to indicate a level of energy that may be provided under the given assumptions and with the given calculations in order to make a relative comparison with the conventional charger.

Although the present invention has been described in connection with preferred embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims.

In this section, certain specific details of the disclosed embodiment, are set forth for purposes of explanation rather than limitation, so as to provide a clear and thorough understanding of the present invention. However, it should be understood readily by those skilled in this art, that the present invention might be practised in other embodiments that do not conform exactly to the details set forth herein, without departing significantly from the spirit and scope of this disclosure. Further, in this context, and for the purposes of brevity and clarity, detailed descriptions of well-known apparatus, circuits and methodology have been omitted so as to avoid unnecessary detail and possible confusion.

Reference signs are included in the claims, however the inclusion of the reference signs is only for clarity reasons and should not be construed as limiting the scope of the claims.

Claims

CLAIMS:

1. A device (102, 204) for powering an electric circuit (110, 206), the device comprising: a first material (104, 112) provided in physical contact with a piezoelectric material (106) for generating electric energy connection means (108, 208) for connecting the piezoelectric material (106) at least electrically to the electric circuit (110, 206), wherein at least a part of a surface (116) of the device is an impact part suited for a mechanical impact and the impact part is formed by the first material (104, 112) and/or the piezoelectric material (106) and the device is adapted for generating electric energy for powering the electric circuit (110, 206) when providing a mechanical impact to the impact part.

2. The device according to claim 1, wherein the device is formed as one impact part.

3. The device according to claim 1, wherein a moving part used to generate electric energy is the device.

4. The device according to claim 1, wherein the first material and the piezoelectric material are provided in physical contact with each other by their shape and size.

5. The device according to claim 1, wherein the first material is adapted to disperse the mechanical impact from a relative small area to an increased area.

6. The device according to claim 1, wherein the first material is adapted to extend the duration that the impact activates the piezoelectric material.

7. The device according to claim 1, wherein the piezoelectric material is at least partly comprised inside the first material.

8. The device according to claim 1, wherein the device is adapted for protecting at least a part of the electric circuit from direct mechanical impact.

9. The device (102, 204) according to claim 1, wherein the first material (104, 112) and/or the piezoelectric material (106) is provided at least partly with one of the following shapes: a shape adapted for protecting at least a part of the electric circuit from directly mechanical impact, a pad shape, the shape of half a ball, a ball shape.

10. The device (102, 204) according to claim 1, wherein the device is adapted for generating electric energy by providing one or more of the following types of mechanical impact to the surface or the impact part: pressing the surface or the impact part, hitting the surface or the impact part, letting the surface or the impact part hit a surface of the surroundings, letting an object hit the surface or the impact part, kicking the surface or the impact part.

11. The device (102, 204) according to claim 1, wherein the device is formed as a ball and wherein using the ball in a playing like manner generates electric energy for at least partly powering the electric circuit (110, 206).

12. The device (102, 204) according to claim 11, wherein the device is provided with means for opening and closing the device and hereby the device is adapted for exchanging the electric circuit (110, 206) positioned inside the device.

13. The device (102, 204) according to claim 1, wherein the piezoelectric material (106) for generating electric energy is polyvinylidene fluoride.

14. An electronic system (102, 202) comprising an electric circuit, the electronic system being adapted for being at least electrically connected to the device (102) according to claim 1 for at least partly powering the electric circuit (206, 110).

15. The electronic system (102, 202) according to claim 14, the electronic system furthermore comprising a rechargeable energy source (114, 220), the system being adapted for being at least electrically connected to the device according to claim 1 for at least partly recharging the energy source.

16. The electronic system (102, 202) according to claim 14, wherein the electronic system is one of the following: a mobile phone (206), a remote control, an alarm clock, an electronic playing game, a toy, a device used in sports such as a racket or a ball, a clothing part.

17. A method of powering an electric circuit (110, 206), the method comprising the following steps: providing a first material (104, 112) in physical contact with a piezoelectric material (106) for generating electric energy - connecting the piezoelectric material (106) at least electrically to the electric circuit forming an impact part of the device (102, 204) by the first material (104, 112) and/or the piezoelectric material (106) generating electric energy for powering the electric circuit (110, 206) when - providing a mechanical impact to the impact part.