WO2010010505A1

WO2010010505A1 - System for charge recycling

Info

Publication number: WO2010010505A1
Application number: PCT/IB2009/053137
Authority: WO
Inventors: Klaus Reimann; Peter Gerard Steeneken; Mareike Klee
Original assignee: Nxp B.V.
Priority date: 2008-07-22
Filing date: 2009-07-20
Publication date: 2010-01-28
Also published as: EP2321893A1

Abstract

The present application relates to a system for charge recycling. The present application relates also to a method for charge recycling and a handheld device, in particular, a multi-media handheld device. The system comprises at least one power supply device. The system comprises a first capacitive element and at least a second capacitive element. The first capacitive element and the second capacitive element are chargeable by the power supply device. The first capacitive element and the second capacitive element are connectable to the power supply device. At least one of the first capacitive element and the second capacitive element is formed as an actuation capacitive element. The system comprises at least a first switching element configured to connect the first capacitive element and the second capacitive element with each other such that at least one part of the charge on the actuation capacitive element is recyclable.

Description

System for charge recycling

TECHNICAL FIELD

The present application relates to a system for charge recycling, and more particularly, a system comprising a power supply device and a first capacitive element. The present application relates also to a method for charge recycling and a handheld device, in particular, a multi-media handheld device. BACKGROUND OF THE INVENTION

In many electrical circuits, switching devices or electronic tuning devices are employed. These devices can be operated by an actuation capacitor being a capacitive element. For operating these devices, the actuation capacitor needs to be charged. By way of example, some of these devices are a gate capacitance of a MOS transistor, a actuation capacitor of a Micro-Electro-Mechanical System (MEMS), a capacitance of a piezoelectric layer in an actuator, such as a MEMS actuator, a bias capacitance of a varactor device or a tuneable capacitor with a high k electric, such as ferroelectric capacitors, anti- ferroelectric capacitors or pyrochlore-based capacitors, or the like. Some of these devices may require for switching purposes a higher voltage than the battery voltage or voltage V_DD provided within an electrical device. In these cases, a charge pump, a switched power supply or the like can be implemented for meeting the voltage requirements of the respective loads. Such systems can be integrated into a system in package. Fig. 1 shows an exemplified embodiment of a MEMS device according to prior art. As can be seen from this Figure, a driving unit 2 is arranged having a control input terminal 16 for connecting a controlling device (not shown) with the driving unit 2. Furthermore, the driving unit 2 comprises a power supply device 4, such as a charge pump, being arranged for charging the capacitive element 8 via connection 14 and a switching element 12.2. Thereby, the capacitive element 8 is arranged within a MEMS device 6 for actuating a switch 10. Thus, the capacitive element 8 is formed as an actuation capacitor. The arranged capacitive element 8 can be discharged by closing the further switching element 12.1 which is arranged within the driving unit 2. However, such a low power charge pump is an inefficient energy converter, since the energy required to charge the actuation capacitor 8 is lost if the capacitor 8 is discharged. Furthermore, the depicted system according to prior art comprises the further drawback that charging may take a long time. In prior art, this issue can be solved by increasing the charge pump which implicates higher costs, larger required space and so on.

What is more, it is a continuous concern to improve the power consumption within an electrical device, in particular, within handheld devices, such as mobile phones or the like, or within ultra-low power applications due to their limited available power. For saving power within such an electrical device, it is also possible according to prior art to recycle energy. However, suitable and flexible applicable charge recycling systems are not known in prior art.

From document US 2007/0177412 a charge pumped driver for a switched mode power supply configured to double a battery voltage is known. This document discloses a power supply device connected to a power stage via a driver, wherein the charge on a holding capacitor of a MOSFET, which is part of the power stage, is recyclable. The charge on the holding capacitor is merely transferred back to the capacitor integrated within the provided power supply device. However, on the one hand, this system is inflexible, and on the other hand, the maximum voltage on the capacitors is twice the supply voltage and the voltage on one of the capacitors remains almost unchanged. The amount of charge that can be recycled is limited.

Therefore, it is one object of the present application to provide a system, which improves power saving. A further object is to increase the system operating time. Another object is to increase switching speed and to decrease actuation time. Another object is to ensure a flexible application of the recycling system. A further object is to allow recycling of charges which are on capacitors having voltages significant higher than the supply voltage of the system.

SUMMARY OF THE INVENTION

These and other objects are solved by a system comprising at least one power supply device. The system comprises a first capacitive element and at least a second capacitive element. The first capacitive element and the second capacitive element are chargeable by the power supply device. The first capacitive element and the second capacitive element are connectable to the power supply device. At least one of the first capacitive element and the second capacitive element is formed as an actuation capacitive element. The actuation capacitive element is configured to provide a state change energy. The system comprises at least a first switching element configured to connect the first capacitive element and the second capacitive element with each other such that at least one part of the charge on the actuation capacitive element is recyclable depending at least on whether the state change energy of the actuation capacitive element is not required.

The present system comprises at least one power supply device configured to generate a suitable output voltage and/or output current for meeting the requirements of the connectable loads. The power supply device may be connected to a provided battery or the like, which may generate a supply voltage V_DD- Furthermore, it is found according to the present application that at least two capacitive elements can be provided advantageously for obtaining a flexible system with significantly reduced actuation times. It shall be understood that, according to further variants of the present application, a plurality of capacitive elements can be arranged within the system. The first capacitive element is connectable to the power supply device to be chargeable by the power supply device as well as the second capacitive element. In other words, both capacitive elements are not integrated within the power supply device but arranged outside the power supply device.

Moreover, at least one of the provided capacitive elements is formed as an actuation capacitive element. An actuation capacitor is configured to actuate a further element or itself or to change a state, parameter or property of a further element or itself by providing a state change energy. The state change energy represents the energy required to change the state of a component. For instance, it is the energy required for switching between two states, like an open state and closed state. The actuation capacitor can be charged with the respective state change energy. For instance, a switch can be actuated by charging and/or discharging the actuation capacitor with a respective state change energy. It may be also possible that the charge of the actuation capacitor is used for actuating a switch or the like. It is also possible that the actuation capacitor is a varicap, wherein the actuation device changes its own properties. In particular, the actuation capacitor must be supplied with a suitable actuation voltage for actuating another component or changing its own properties. It is further found according to the present application that energy can be recycled in a simple manner by implementing a switching element between both the first capacitive element and the second capacitive element. The switching element, such as a suitable low-power switch, can be controlled such that energy is recycled. More particularly, at least one part of the charge stored on at least the actuation capacitor is recyclable. For instance, at least a portion of the charge or energy stored on the actuation device can be used for charging at least the second capacitive element by establishing a communication between the first and the second capacitive element, i.e. closing the first switching element. Furthermore, controlling the first switching element depends at least on whether the state change energy of the actuation energy is still required on one of the capacitive elements. If the state change energy of the actuation capacitor is not required anymore, at least a part of the state change energy can be recycled. In the other case, i.e. the state change energy on the actuation capacitor is required for actuating a component; the first switching element may interrupt the energy flow between the first and the second capacitive element. The system according to the present application provides for reduced power consumption and increased switching speed. Furthermore, the present system can be employed flexibly and the actuation time can be significantly reduced.

In another embodiment of the system according to the present application, the power supply device can be formed as a charge pump device and/or switched power supply. A charge pump may be configured to generate a higher output voltage and/or current than the voltage and/or current provided by the battery or the like for meeting voltage requirements of the connected loads, like the capacitive elements. In particular, a required actuation voltage for an actuation capacitor may be higher than the battery voltage. A charge pump can be used in particular in low power application, while a switched power supply can be preferred for high power applications.

The charge pump device may be configured to charge the first capacitive element with the charge of the second capacitive element according to a further embodiment. In other words, the charge pump can be used for recycling the charge from the first to the second capacitor. The available charge of one capacitor may be higher than the supply voltage and can be used for charging the further capacitor.

Furthermore, the voltage of the actuation capacitive element being recycled may be at least two times higher, in particular four times higher than the supply voltage. A high voltage compared to the supply voltage causes a more efficient application.

According to a further embodiment, at least one of the capacitive elements may be configured to change its value during recycling by at least more than 40 %, in particular more than 75 %. This may be advantageous for applications which are not implemented in CMOS technology.

At least one driving unit may be arranged according to another embodiment. The driving unit may be configured to drive charging and/or discharging of at least one capacitive element. A single driving unit can be arranged for each capacitive element resulting in easily and accurately controlling the charging and/or discharging of the provided capacitors. Such a driving unit may also include the power supply device as well as the power supply device can be arranged outside the driving units. What is more, the system according to a further embodiment of the present application may comprise a second switching element, which may be configured to connect the first capacitive element to the power supply device via a first connection. The second switch can be controlled such that, in case charging of the capacitor by the power supply device is required, the second switch can be closed. Otherwise, the second switch can be opened for interrupting a power transfer between the power supply device and the first capacitor. This switching element can be implemented within the driving unit. Charge control can be easily secured.

According to a further embodiment, the system may comprise a third switching element which may be configured to connect the second capacitive element to the power supply device via a second connection. The third switch can be controlled in a similar manner as the second switch stated above. The third switch may also be implemented within the driving unit, which may be arranged for driving the second capacitive element.

For providing a simple discharge possibility of the first capacitive element, the system according to another embodiment may further comprise a fourth switching element which may be configured to connect the first capacitive element to ground potential. Also this switch can be provided within the driving unit. For instance, the second switch and the fourth switch can be connected in series between the power supply device and ground potential and their connecting point can be connected to the first capacitive element. A compact design is achieved, wherein the switches can be controlled oppositely for charging and discharging the first capacitive element respectively. In addition, according to a further embodiment, a fifth switching element can be arranged, which may be configured to connect the second capacitive element to ground potential. Also this switch may be arranged and controlled similar to the previously mentioned fourth switch.

Furthermore, the system according to a further embodiment of the present application may comprise a sixth switching element, wherein the sixth switching element may be configured to connect the first capacitive element to the power supply device via a third connection. In particular, both the first connection and the third connection may be provided at the same time. The additional third connection can be arranged for biasing the charge pump with the energy stored on the first capacitive element. Biasing a charge pump with a voltage higher than the supply voltage results in a higher pump rate and increased efficiency of the charge pump. E.g., pump sections in the charge pump can be disabled when operated with the higher voltage as available from the discharged capacitor. In addition, according to a further embodiment, a seventh switching element can be arranged, which may be configured to connect the second capacitive element to the power supply device via a fourth connection. In particular, both the second connection and the fourth connection may be provided at the same time. Also this seventh switch may be arranged and controlled similar to the previously mentioned sixth switch. It shall be understood that according to other variants of the present application it can be preferred that all four connections can be provided. A fifth connection may be provided by an eighth switching element to connect the capacitors or the charge pump to ground. If not already included in the charge pump, a ninth switching element can be introduced parallel to the eighth element to select between ground or supply voltage.

Moreover, both the first capacitive element and the second capacitive element can be formed as actuation capacitive elements. For instance, in several applications two switches to be actuated are arranged, wherein in case the first switch is closed the second switch must be opened. In case, the switching elements are actuated by two actuating capacitors, the charge of each capacitor can be recycled by coupling both capacitors via the first switching element for transferring at least portions of energy from one capacitor to the other one. Power consumption can be significantly reduced as well as actuation times.

In a further embodiment, at least one controlling device configured to control at least the provided switching elements may be arranged. The controlling device may be a suitable processing unit, like a custom logic circuit, a microprocessor or the like. Furthermore, the controlling device may be also configured to control the driving unit. It may be advantageous to control all switching elements by the controlling device, and to integrate all switching elements with the controlling device. It shall be understood that also more than one controlling device can be provided.

According to another embodiment, the present system may comprise a switch array. The switch array may be a digital network. For instance, the switch array may be configured to realize a plurality of capacitance values. For switching, at least portions of the energy stored in capacitances can be recycled for reducing power consumption significantly. At the same time, switching speed can be increased.

Another aspect of the present application is a method for controlling recycling of state change energy stored on at least one arranged actuation capacitive element, wherein at least a second capacitive element is arranged, and wherein the a first switching element is arranged between the actuation capacitive element and the second capacitive element, comprising charging the actuation capacitive element by a power supply device, separating the actuation capacitive element from the power supply device, closing the first switching element for transferring at least a part of the state change energy stored on the actuation capacitive element to the second capacitive element.

Furthermore, according to another embodiment of the present application, the method may further comprise inverse charging of the actuation capacitive element at least partially by the second capacitive element. In particular, after discharging an actuation capacitor over a second capacitive element, like a buffer capacitor, the actuation capacitor can be inverse charged by the energy stored on the at least one second capacitor, in case at least the first switching element is driven respectively. In other words, a portion of the charge stored on the actuation capacitor before this capacitor is discharged can be recycled by using at least a second capacitor and the first switching element. The system according to the present application can be used in electrical devices, which requires a frequent actuation, such as fast antenna matching. Furthermore, the present system is also suited for high operation voltages and for fast switching of many switches. The charge recycling system can be used for ferroelectric devices, such as ferroelectric varactors or ferroelectric MEMS, where the ferroelectric layer acts as electrostrictive or piezoelectric layer, capacitive or galvanic MEMS switches or (ultra-)sonic transducers.

Another aspect of the present application is a handheld device, in particular a handheld multi media device, comprising at least one system as stated above. The handheld device may be a mobile phone, personal digital assistant or the like. It shall be understood that, according to further variants of the present application, the handheld device may comprise more than merely one present charge recycling system.

According to a further embodiment of the present application, the handheld device may further comprise a Micro-Electro-Mechanical system switch, a Micro-Electro- Mechanical system sensor, a Micro-Electro-Mechanical system actuator, a tunable component, an ultra low power application, a piezoelectric actuator, an electrostatic actuator and/or combinations thereof.

These and other aspects of the present patent application become apparent from and will be elucidated with reference to the following Figures. The features of the present application and of its exemplary embodiments as presented above are understood to be disclosed also in all possible combinations with each other.

BRIEF DESCRIPTION OF THE DRAWINGS In the Figures show:

Fig. 1 a first embodiment of a Micro-Electro-Mechanical System according to prior art,

Fig.2 a first embodiment of the system according to the present application, Fig. 3 a second embodiment of a Micro-Electro-Mechanical System according to prior art,

Fig. 4 a second embodiment of the system according to the present application,

Fig. 5 a third embodiment of the system according to the present application, Fig. 6 a digital network combinable with the system according to the present application,

Fig. 7 an exemplified graph illustrating possible power saving of the digital network shown in Fig. 6,

Fig. 8 a fourth embodiment of the system according to the present application, Fig. 9 an embodiment for charge inversion according to prior art, Fig. 10 an embodiment of the system according to the present application for charge inversion.

Like reference numerals in different Figures indicate like elements.

DETAILED DESCRIPTION OF THE DRAWINGS In the following detailed description of the present application, exemplary embodiments of the present application will describe and point out a charge recycling system for an improved utilization of provided energy with reduced actuation time.

In Fig. 2, a first simplified embodiment of the system according to the present application is shown. The depicted system comprises a power supply device 4, which comprises in each case one connection to the first capacitive element 8.1 and to the second capacitive element 8.2. Any power supply device which is suited for charging the arranged first and second capacitive elements 8.1 and 8.2 can be implemented. By way of example, the power supply device 4 may be supplied by a voltage V_DD and may be formed as a charge transfer device, like a charge pump or switched power supply, configured to charge and/or discharge both the first and second capacitive elements 8.1 and 8.2.

At least one of the capacitive elements 8.1 and 8.2 may be an actuating capacitor while the other may be also an actuating capacitor or a buffer capacitor. Thereby, a buffer capacitor can be used as an intermediate storage for storing energy for later use.

In addition, a first switching element 20 is arranged within the present system. The first switching element 20 can be formed as a low-power switch, like a transistor or any other kind of controllable switch. This switch 20 is arranged such that charge and the state change energy respectively stored on at least one capacitive element is recyclable. The first switch can be closed in case at least the state change energy on the actuation capacitor, such as capacitor 8.1, is not required. In this case, at least parts of the not required state change energy can be transferred to the further arranged capacitor 8.2 via the first switch 20 for instance to use the state change energy for actuating a further component by capacitor 8.2. It may also possible that the transferred energy is merely stored for later use, for instance, for charging the actuating capacitor 8.1 once again. A more detailed elucidation of the charge recycling system will occur subsequently.

For elucidating the system according to the application and its advantages compared to prior art, at first, a system according to prior art is pointed out. Fig. 3 shows a second embodiment of a system according to prior art. The depicted system is similar to the previously stated embodiment according to prior art (Fig. 1), and thus, for avoiding repetitions, merely the additional features are explained.

As can be seen from Fig. 3, substantially two embodiments, as shown in Fig. 1, are arranged. More particularly, two driving units 2.1 and 2.2 with two control input terminals 16.1 and 16.2 and four switching elements 12.1 to 12.4, two connections 14.1 and 14.2 as well as two MEMS devices 6.1 and 6.2 each comprising a capacitive element 8.1 or 8.2, in particular, actuation capacitors, and a switch 10.1 or 10.2 are arranged. Furthermore, one power supply device 4 is provided. The shown system does not provide a possibility for recycling energy stored in one of the capacitors 8.1 and 8.2. It is merely possible to fully discharge both capacitors 8.1 and 8.2 without reusing this energy. The benefits of the present system compared to prior art are pointed out by the aid of Fig. 4. In Fig. 4, a second embodiment of the system according to the present application is shown. The main difference between the embodiment of prior art (Fig. 3) and the present embodiment according to the application is that a first switching element 20 is arranged between the first capacitive element 8.1 and the second capacitive element 8.2. It may be advantageous to implement a low-power switch as the first switching element 20. In the following the functioning of the shown embodiment will be pointed out.

As stated above, the first capacitor 8.1 can be charged by the power supply device 4, for instance a charge pump, which is configured to generate a required activation voltage, by closing the switch 12.2 and opening the switch 12.1. This can be controlled by a controlling device (not shown) via control input terminal 16.1. By way of example, a suitable processing unit can be employed as the controlling device. The second capacitive element 8.2 can be charged in a similar manner, wherein the charge process can be also controlled by the controlling device. In case the first switch 20 is opened, charge cannot be transferred among the capacitive elements 8.1 and 8.2. In case the switch 20 is closed, at least a portion of charge can be transferred from capacitor 8.1 to capacitor 8.2 or vice versa, which may depend on the charge status of the capacitors 8.1 and 8.2. The first switch 20 can be closet in case the state change energy stored on the actuation capacitor 8.1 is not longer required on the actuation capacitor 8.1. Thereby, the switch 20 can be controlled by the controlling device. It may be required that at the same time the switching elements 12.1 to 12.4 are opened. In case the transferred charge or state change energy from one capacitor to the other capacitor is not sufficient, the respective capacitor 8.1 or 8.2 can be additionally charged by the power supply device. Therefore, the respective driving unit 2.1 or 2.2 can be respectively switched and the first switch 20 can be opened.

The present embodiment can be used within many application requiring signal routing switches. This may be the case within a MEMS switch or the like. By way of example, an antenna can be connected to several receiving and/or transmitting signal paths. In such a device, closing one switch requires that another switch must be opened. Using the embodiment shown in Fig. 4 enables to recycle at least partially the charge for actuation. More particularly, at least half of the charge can be transferred from capacitor 8.1 to capacitor 8.2 by closing the first switch 20.

Besides a significant faster switching and less actuation time, extra benefit of charge recycling can be achieved. More particularly, the actuation capacitance may depend on the actuation state. Opening a switch, for instance a capacitive MEMS yields a reduced actuation capacitance of approximately a factor often. This means that the switch itself may act as a charge pump and is capable of generating high voltage transients during opening. This fact can be used by designing the switch hysteresis and switch electronic in a suitable manner to increase the recyclable part of charge. It shall be understood that, according to further variants of the present application, more than only two capacitors can be arranged as well as more than only one first switch configured to recycle charge can be provided.

In Fig. 5, a third embodiment of the system according to the present application is depicted. The present system comprises also two MEMS devices 6.1 and 6.2 similar to the previously described MEMS devices 6, 6.1 and 6.2. In addition, the power supply device of the present embodiment is formed as a charge pump 4.1. Other power supply devices are also usable. The charge pump 4.1 may be configured to generate an actuation voltage, which may be higher than the supply voltage V_DD provided by the electrical device. By way of example, the charge pump 4.1 may comprise one or more suitable energy storing units for generating the required actuation charge by suitable switching.

As can be further seen from Fig. 5, besides the first and second connections 14.1 and 14.2, the first capacitive element 8.1 is also in communication with the charge pump 4.1 via a third connection 18.1 and the second capacitive element 8.1 is in communication with the charge pump 4.1 via a fourth connection 18.2. The third connection 18.1 comprises a sixth switching element 22.1 and the fourth connection 18.2 encompasses a seventh switching element 22.2. What is more, a further switch 22.3 is provided for establishing a connection to the ground potential. A similar switch could be added in parallel to the supply voltage, if not already included in the charge pump.

Additionally to the functioning of the system according to Fig. 4, the depicted system enables biasing the charge pump 4.1. More particularly, the two additional arranged switches 22.1 and 22.2 and connections 18.1 and 18.2 enable that the charge pump 4.1 can be biased with the voltage on capacitor 8.1 and/or capacitor 8.2. For instance, in case switches 12.2 and 22.2 are closed and switches 12.1 and 22.1 are opened, the voltage stored on capacitor 8.2 can be biased to the charge pump 4.1. In the other case, i.e. switches 12.1 and 22.1 are closed and switches 12.2 and 22.2 are opened, the voltage stored on capacitor 8.1 can be biased to the charge pump 4.1. Moreover, in each of the described examples, the further arranged switch 22.3 can be closed for fully discharging the respective capacitive element 8.1 or 8.2.

As mentioned hereinbefore, the present system is not only suitable for single switch application. In an advantageous manner, the present system can be also employed in a digital system as depicted in Fig. 6. The depicted digital network may comprise four branches arranged in parallel, wherein in turn each branch comprises a series connection of a capacitor 9.1 to 9.4 and a switch 24.1 to 24.4. The shown digital network can realize 16 (15+open) capacitance values.

Each of the switches 24.1 to 24.4 is operated by a separate actuation capacitor (not shown). These activation capacitors may need charge for actuation, which can be realized by combining the digital network with one embodiment of a system as shown in Figs. 2 or 4. For simplicity reasons, the entire realization of the combination of the digital network and the system according to the present application is not depicted.

Fig. 7 shows a graph, which illustrates the possible power saving by combining an embodiment of the system according to the present application with the digital network as shown in Fig. 6. While the solid bars 29 indicate the case that the system according to the present application is not used, the striped bars 27 indicate the case that the system according to the present application is employed. Furthermore, reference sign 26 indicates the positive values needed to step up and reference sign 28 indicates the negative values needed to step down for realizing the possible capacitance values. As can be seen from the graph, the power consumption can be significantly reduced by using the system according to the present application, in particular for the case 28 of step down values.

In Fig. 8 a fourth embodiment of the system according to the present application is depicted. The shown system comprises a first capacitive element 8.1, which may be implemented within a capacitive MEMS switch 6.3. The actuation capacitor 8.1 is in this particular case at the same time the switched capacitor. Biasing the capacitor 8.1 with an actuation voltage results in a hysteretic switching of its capacitance. Alternatively, this could be an actuated galvanic switch in series with a capacitor or a capacitance array as depicted in Fig. 6. Furthermore, two tunable capacitive elements 11.1 and 11.2 are arranged. In other words, a tunable capacitor is combined with a MEMS switch. As a tunable capacitor 11.1 or 11.2, a varactor device or the like can be employed. Also in this embodiment, a continuous value variation may require a discharge of the tuned capacitors 11.1 and 11.2 and a charge of the MEMS actuation capacitor 8.1. Reference sign 34 indicates the actuation charge recycling directions. Other combinations are possible, like galvanic switches with tunable acoustic filters. It is found according to the present application that a system for charge inversion according to prior art can be also significantly improved in view of power consumption and actuation time by employing the system according to the present application. Fig. 9 shows an embodiment for charge inversion according to prior art. The depicted system can be connected to a power supply device (not shown) via terminal 40. A second capacitor 36 is arranged between the potential of terminal 40 and ground potential. In parallel to the second capacitor 36 a network 41 is connected having four switches 38.1 to 38.4 and a first capacitive element 37, in particular, an actuation capacitor 37.

The charge of the actuation capacitor 37 can be inversed as follows. By way of example, the actuation capacitor 37 can be charged with the provided voltage via terminal 40 by closing switches 38.2 and 38.3 and opening switches 38.1 and 38.4. In case the charge on the actuation capacitor 37 should be inverted, the switches 38.2 and 38.3 are opened and the switches 38.1 and 38.4 are closed. Then the actuation capacitor 37 is first discharged via the second capacitor 36, and subsequently, the actuation capacitor 37 is charged by the applied voltage resulting in an inverse charge compared to the previous status of the actuation capacitor 37. For inverting the charge once again, the switches 38.1 to 38.4 can be switched respectively. However, the charge on the actuation capacitor 37 is not recyclable according to prior art.

Fig. 10 shows an embodiment of the system according to the present application for charge inversion. The main differences compared to the embodiment of prior art are an additional first switching element 42 arranged within the network 41.1 and the arrangement of three capacitive elements 36.1, 36.2 and 37. The capacitive elements 36.1 and 36.2 may be formed as suitable buffer capacitors 36.1 and 36.2. As can be seen from this

Figure, the capacitive elements 36.1 and 36.2 are arranged in parallel to each other and they are connectable to each other via the first switch 42. Both capacitors 36.1 and 36.2 comprise a capacitive value C/2 of half the capacitive value C of the capacitor 36 as shown in Fig. 9. In addition, the first switch 42 is arranged in parallel to the actuation capacitor 37 between the connecting points 44.1 and 44.2.

Subsequently, the functioning of the embodiment shown in Fig. 10 is pointed out. By way of example, the actuation capacitor 37 can be charged by closing besides the first switch 42 the switches 38.1 and 38.4 and by opening switches 38.2 and 38.3. Then the first switching element 42 and switching element 38.4 can be opened as well as switching element 38.3 can be closed. This causes that the actuation capacitor 37 is discharged into buffer capacitor 36.2. Afterwards, switch 38.1 is opened and switches 42 and 38.2 are closed. The actuation capacitor 37 is inverse charged by the voltage provided by the voltage supply device, and in addition, by the buffer capacitor 36.2, which has stored at least parts of the energy previously stored within the actuation capacitor 37. According to the present embodiment, approximately 25% of energy can be saved for the energy originally stored on the actuation capacitor 37. Furthermore, recharging the buffer capacitors 36.1 and 36.2 requires less time compared to the system of prior art.

Furthermore, it is readily clear for a person skilled in the art that the logical blocks in the schematic block diagrams presented in the above description may at least partially be implemented in electronic hardware and/or computer software, wherein it depends on the functionality of the logical block and on design constraints imposed on the respective devices to which degree a logical block is implemented in hardware or software. The presented logical blocks may for instance be implemented in one or more digital signal processors, application specific integrated circuits, field programmable gate arrays or other programmable devices. To this end, the processor and the storage medium may be coupled to interchange information, or the storage medium may be included in the processor.

Claims

CLAIMS:

1. A system, comprising: at least one power supply device (4, 4.1), a first capacitive element (8.1, 37), at least a second capacitive element (8.2, 11.1, 11.2, 36.1, 36.2), - the first capacitive element (8.1, 37) and the second capacitive element (8.2,

11.1, 11.2, 36.1 , 36.2) being chargeable by the power supply device (4, 4.1), the first capacitive element (8.1, 37) and the second capacitive element (8.2, 11.1, 11.2, 36.1 , 36.2) being connectable to the power supply device (4, 4.1), at least one of the first capacitive element (8.1, 37) and the second capacitive element (8.2, 11.1, 11.2, 36.1, 36.2) being formed as an actuation capacitive element (8.1, 8.2, 37), the actuation capacitive element (8.1, 8.2, 37) being configured to provide a state change energy, and at least a first switching element (20, 42) configured to connect the first capacitive element (8.1, 37) and the second capacitive element (8.2, 11.1, 11.2, 36.1, 36.2) with each other such that at least one part of the charge on the actuation capacitive element (8.1, 8.2, 37) is recyclable depending at least on whether the state change energy of the actuation capacitive element (8.1, 8.2, 37) is not required.

2. The system according to claim 1, wherein the power supply device (4) is formed as at least one of:

A) charge pump device (4.1),

B) switched power supply.

3. The system according to claim 2, wherein the charge pump device (4.1) is configured to charge the first capacitive element (8.1, 37) with the charge of the second capacitive element (8.2, 11.1, 11.2, 36.1, 36.2).

4. The system according to claim 1, wherein the voltage of the actuation capacitive element (8.1, 8.2, 37) being recycled is at least two times higher, in particular four times higher than the supply voltage.

5. The system according to any of claims 1-4, wherein at least one of the capacitive elements (8.1, 8.2, 11.1, 11.2, 36.1, 36.2, 37) is configured to change its value during recycling by at least more than 40 %, in particular more than 75 %.

6. The system according to any of claims 1-5, further comprising at least one driving unit (2.1, 2.2) configured to drive charging and/or discharging of at least one capacitive element (8.1, 8.2, 11.1, 11.2, 36.1, 36.2, 37).

7. The system according to any of claims 1-6, further comprising a second switching element (12.2) configured to connect the first capacitive element (8.1, 37) to the power supply device (4, 4.1) via a first connection (14.1), and/or a third switching element (12.4) configured to connect the second capacitive element (8.2, 11.1, 11.2, 36.1, 36.2) to the power supply device (4, 4.1) via a second connection (14.2).

8. The system according to any of claims 1-7, further comprising a fourth switching element (12.1) configured to connect the first capacitive element (8.1, 37) to ground potential, and/or a fifth switching element (12.3) configured to connect the second capacitive element (8.2, 11.1, 11.2, 36.1, 36.2) to ground potential.

9. The system according to any of claims 1-8, further comprising a sixth switching element (22.1) configured to connect the first capacitive element (8.1, 37) to the power supply device (4, 4.1) via a third connection (18.1), and/or at least a seventh switching element (22.2) configured to connect the second capacitive element (8.2, 11.1, 11.2, 36.1 , 36.2) to the power supply device (4, 4.1) via a fourth connection (18.2).

10. The system according to any of claims 1-9, wherein the first capacitive element (8.1, 37) and the second capacitive element (8.2, 11.1, 11.2, 36.1, and 36.2) are formed as actuation capacitive elements (8.1, 8.2, and 37).

11. The system according to any of claims 1-10, further comprising a controlling device configured to control at least the provided switching elements (12.1, 12.2, 12.3, 12.4, 20, 22.1, 22.2, 22.3, 38.1, 38.2, 38.3, 38.4, and 42).

12. The system according to any of claims 1-11, further comprising a switch array.

13. A method for controlling recycling of state change energy stored on at least one arranged actuation capacitive element (8.1, 8.2, 37), wherein at least a second capacitive element (8.2, 11.1, 11.2, 36.1, 36.2) is arranged, and wherein the a first switching element (20, 42) is arranged between the actuation capacitive element (8.1, 8.2, 37) and the second capacitive element (8.2, 11.1, 11.2, 36.1, 36.2), comprising: charging the actuation capacitive element (8.1, 8.2, 37) by a power supply device (4, 4.1), separating the actuation capacitive element (8.1 , 8.2, 37) from the power supply device (4, 4.1), - closing the first switching element (20, 42) for transferring at least a part of the state change energy stored on the actuation capacitive element (8.1, 8.2, 37) to the second capacitive element (8.2, 11.1, 11.2, 36.1, 36.2).

14. The method according to claim 13, further comprising inverse charging of the actuation capacitive element (8.1, 8.2, 37) at least partially by the second capacitive element

(8.2, 11.1, 11.2, 36.1, 36.2).

15. A handheld device, in particular a handheld multi media device, comprising at least one system according to any of claims 1-12.

16. The handheld device according to claim 15, further comprising at least one of:

A) Micro-Electro-Mechanical system switch,

B) Micro-Electro-Mechanical system sensor,

C) Micro-Electro-Mechanical system actuator, D) tunable component,

E) ferroelectric component,

F) ultra low power application,

G) piezoelectric actuator, H) electrostrictive actuator,

I) electrostatic actuator, and

J) combinations thereof.

17. Use of a system according to any of claims 1-12 for saving electrical energy.

18. Use of a system according to any of claims 1-12, for increasing switch speed and/or ramp up time of voltage on actuation capacitance.