Electrical energy converter with piezoelectric element(s) and associated electronic electrical energy conversion system

Abstract

Electrical energy converter with piezoelectric element(s) and associated electronic electrical energy conversion system The present invention relates to an electrical energy converter (40) capable of converting an input voltage (Vin) into at least one output voltage (Vout), the input voltage (Vin) being applied between a first input terminal (44) and a second input terminal (46), the output voltage (Vout) being provided between a first output terminal (48) and a second output terminal (50), comprising at least two elementary piezoelectric converters (21, 22, 23), each comprising a primary switching branch (4a1, 4a2, 4a3) and a secondary switching branch (4b1, 4b2, 4b3), at least two elementary piezoelectric converters (2, 21, 22, 23) being connected in series via their primary switching branches (4a, 4a1, 4a2, 4a3) and / or secondary switching (4b, 4b1, 4b2, 4b3),between two terminals among the first input terminal (44), the second input terminal (46), the first output terminal (48) and the second output terminal (50). Figure for abstract: Figure 3,

Description

Title of the invention: Electrical energy converter with piezoelectric element(s) and associated electronic electrical energy conversion system

[0001] The present invention relates to an electrical energy converter capable of converting an input voltage into at least one output voltage.

[0002] The invention also relates to an associated electrical energy conversion system.

[0003] The invention lies in the field of electronic electrical energy conversion systems, in particular those comprising a piezoelectric element, in particular voltage conversion systems, i.e. direct-direct voltage conversion systems, also called DC-DC conversion systems (from the English Direct Current - Direct Current), alternating-direct conversion systems, also called AC-DC conversion systems (from the English Alternating Current - Direct Current), direct-alternating conversion systems or alternatively alternating-alternating conversion systems.

[0004] Documents FR 3 064 850 B1, FR 3 086 471 B1 and FR 3 086 472 B1 disclose various architectures of electrical energy converters with piezoelectric elements.

[0005] These documents describe converters comprising at least one piezoelectric assembly comprising at least one piezoelectric element, connected between two midpoints of a switching branch, each switching branch comprising a switch whose open or closed position can be controlled by an electronic device for controlling the converter. The switches are controlled cyclically, by control cycles, at the resonance oscillation frequency of the piezoelectric element, between phases at substantially constant load, during which the piezoelectric element is in open circuit and phases at substantially constant voltage, during which some of the switches are closed to control a substantially constant voltage level.

[0006] As known per se, the mechanical oscillation of piezoelectric elements (or piezoelectric resonators) is approximately sinusoidal over respective resonance cycles, also called resonance periods. The total mechanical deformation of the piezoelectric elements is the sum of elementary mechanical deformations of each of the piezoelectric elements. An increase or decrease in the energy stored over a period leads respectively to an increase or decrease in the oscillation amplitude.

[0007] Such piezoelectric element converters of the aforementioned type are controlled on control cycles (also called control cycles), the control cycle frequency being at least a factor of 10 higher than the frequency of change of the input / output voltages of the converter, so that during each control cycle, the input and output voltages are substantially constant.

[0008] An electrical energy converter driven so that the input voltage Vin is at least twice higher than the output voltage Vout is called a deep step-down converter. An electrical energy converter driven so that the input voltage Vin is at least twice lower than the output voltage Vout is called a deep step-up converter. The ratio between the highest voltage and the lowest voltage is called the conversion ratio.

[0009] One of the objectives of the invention is to produce electrical energy converters that are highly step-down or highly step-up, i.e. with an energy conversion ratio significantly greater than two, for example greater than 4, while using less expensive piezoelectric elements.

[0010] For this purpose, the subject of the invention is an electrical energy converter capable of converting an input voltage into at least one output voltage, the converter comprising a first input terminal and a second input terminal, the input voltage being applied between the first input terminal and the second input terminal, and comprising a first output terminal and a second output terminal, the output voltage being supplied between the first output terminal and the second output terminal. This converter comprises at least two elementary piezoelectric converters, each elementary piezoelectric converter comprising a primary switching branch and a secondary switching branch, the primary switching branch comprising two primary arms connected at a primary midpoint, a first primary arm being connected between a first primary terminal and the primary midpoint,a second primary arm being connected between a second primary terminal and the primary midpoint, each of said primary arms comprising a primary switch, the secondary switching branch comprising two secondary arms connected at a secondary midpoint, a first secondary arm being connected between a first secondary terminal and the secondary midpoint, a second secondary arm being connected between a second secondary terminal and the secondary midpoint, each of said secondary arms comprising a secondary switch, the elementary piezoelectric converter comprising at least one piezoelectric element connected between the primary midpoint and the secondary midpoint, wherein at least two elementary piezoelectric converters are connected in series via their primary switching branches and / or via their secondary switching branches, between two terminals among the first input terminal, the second, input terminal, the first output terminal and the second output terminal.

[0011] Advantageously, the series connection of at least two elementary piezoelectric converters via their switching branches, primary and / or secondary, makes it possible to divide the voltage at the primary and / or secondary terminals of the elementary piezoelectric converters concerned, while maintaining a high input or output voltage at the terminals of the electrical energy converter. Thus, each of the elementary piezoelectric converters is requested to carry out an electrical energy conversion with a more moderate conversion ratio, while the electrical energy converter achieves a high conversion ratio.

[0012] According to other advantageous aspects of the invention, the electrical energy converter comprises one or more of the following characteristics, taken in isolation or in all technically possible combinations.

[0013] The converter comprises at least two elementary piezoelectric converters connected in series via their primary switching branches and connected in parallel via their secondary switching branches.

[0014] The at least two elementary piezoelectric converters connected in series via their primary switching branches share the same secondary switching branch.

[0015] There are at least two elementary piezoelectric converters connected in parallel via their primary switching branches and connected in series via their secondary switching branches.

[0016] The at least two elementary piezoelectric converters connected in series via their secondary switching branches share the same primary switching branch.

[0017] This converter comprises at least one elementary piezoelectric converter called an elementary input piezoelectric converter, the first primary terminal of said elementary input piezoelectric converter being connected to the first input terminal and / or the second primary terminal of said elementary input piezoelectric converter being connected to the second input terminal.

[0018] It comprises at least one elementary piezoelectric converter called elementary output piezoelectric converter, the first secondary terminal of said elementary output piezoelectric converter being connected to the first output terminal and / or the second secondary terminal of said elementary output piezoelectric converter being connected to the second output terminal.

[0019] The at least two elementary piezoelectric converters are connected in series via their primary switching branches or via their secondary switching branches, between a first terminal among the first input terminal and the second input terminal and a second terminal among the first output terminal and the second output terminal.

[0020] This converter comprises, for at least one of said elementary piezoelectric converters, a capacitor connected between the first primary terminal and the second primary terminal or between the first secondary terminal and the second secondary terminal.

[0021] It comprises a plurality of elementary piezoelectric converters connected in series by their primary switching branches, in which each of said elementary piezoelectric converters comprises a capacitor connected between the first primary terminal and the second primary terminal.

[0022] There is a plurality of elementary piezoelectric converters connected in series by their secondary switching branches, wherein each of said elementary piezoelectric converters comprises a capacitor connected between the first secondary terminal and the second secondary terminal.

[0023] The invention also relates to an electronic electrical energy conversion system comprising an electrical energy converter and an electronic device for controlling the electrical energy converter, the electrical energy converter is as briefly described above.

[0024] According to another advantageous aspect of the invention, the electronic control device is configured to control the primary and / or secondary switches of each of the elementary piezoelectric converters over a control cycle to alternate between phases at substantially constant load and phase at substantially constant voltage, a first control half-cycle comprising a first phase at substantially constant voltage of first voltage and first duration, and a second phase at substantially constant voltage of second voltage and second duration, a second control half-cycle comprising a third phase at substantially constant voltage of voltage opposite to the first voltage and of duration substantially equal to the first duration, and a fourth phase at substantially constant voltage of voltage opposite to the second voltage and of duration substantially equal to the second duration.

[0025] According to another advantageous aspect of the invention, during each phase at substantially constant voltage, one of the primary switches and one of the secondary switches is in the closed position, and the other of the primary switches and the other of the secondary switches is open.

[0026] The invention will appear more clearly on reading the description which follows, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0027] [Fig-1] [Fig.l] is a schematic representation of a piezo converter elementary electric and an electric circuit corresponding to a piezoelectric element;

[0028] [Fig.2] [Fig.2] is a functional representation of an electronic system of electrical conversion;

[0029] [Fig.3] [Fig.3] illustrates an embodiment of an electrical energy converter comprising N=3 elementary piezoelectric converters connected in series via their primary switching branches;

[0030] [Fig.4] [Fig.4] schematically illustrates a variant of the energy converter electric of [Fig.3];

[0031] [Fig.5] [Fig.5] is a schematic representation of an electrical energy converter comprising three piezoelectric converters connected in series via their secondary switching branches;

[0032] [Fig.6] [Fig.6] is a schematic representation of a variant of the electrical energy converter of [Fig.4];

[0033] [Fig.7] [Fig.7] is a schematic representation of another embodiment of an electrical energy converter in which piezoelectric converters connected in series via their primary switching branches between an input terminal and an output terminal;

[0034] [Fig.8] [Fig.8] illustrates curves of the evolution of the voltage at the terminals of a piezoelectric assembly of an elementary piezoelectric converter in a plurality of voltage-lowering configurations, in three-stage control at substantially constant voltage;

[0035] [Fig.9] [Fig.9] illustrates curves of the evolution of the voltage at the terminals of a piezoelectric assembly of an elementary piezoelectric converter in a plurality of voltage-boosting configurations, in three-stage control at substantially constant voltage;

[0036] [Fig. 10] [Fig. 10] illustrates curves of the evolution of the voltage at the terminals of a piezoelectric assembly of an elementary piezoelectric converter in voltage step-down and voltage step-up configurations, in four-step control at substantially constant voltage;

[0037] [Fig. 11] [Fig. 11] illustrates an embodiment of an electrical energy converter comprising several elementary piezoelectric converters with switching bridge connected in series via their primary switching branches.

[0038] In the following description, the expression "substantially equal to" defines a relationship of equality to plus or minus 10%, preferably to plus or minus 5%, unless otherwise indicated.

[0039] [Fig.l] illustrates a piezoelectric converter 2 called an elementary piezoelectric converter, as well as an electrical circuit modeling the operation of a piezoelectric element.

[0040] The various embodiments of the invention implement a plurality of elementary piezoelectric converters, according to architectures described in detail below.

[0041] The piezoelectric converter 2 illustrated in [Fig.l] comprises a switching branch called the primary switching branch 4a and a switching branch called the secondary switching branch 4b.

[0042] The primary switching branch 4a comprises a first primary terminal 6a and a second primary terminal 8a, and a primary midpoint 10a. Between the primary terminals 6a, 8a is applied a potential difference or primary voltage. In the example of [Fig.l], a potential Vxai is applied to the first primary terminal 6a, and a potential Vxah is applied to the second primary terminal 8a. By convention, the potential Vxai is lower than the potential Vxah. The potential at the primary midpoint 10a is denoted Vxar.

[0043] The secondary switching branch 4b comprises a first secondary terminal 6b and a second secondary terminal 8b, and a secondary midpoint 10b. Between the secondary terminals 6b, 8b is provided a potential difference or secondary voltage. In the example of [Fig.l], a potential VxM is provided at the first secondary terminal 6b, and a potential Vxbh is provided at the second secondary terminal 8b. By convention, the potential VxWest is lower than the potential Vxbh. The potential at the secondary midpoint 10b is denoted Vxbr.

[0044] The primary switching branch 4a comprises two arms, respectively a first primary arm 14a connected between the first primary terminal 6a and the primary midpoint 10a, and a second primary arm 16a connected between the second primary terminal 8a and the primary midpoint 10a.

[0045] Each of the first and second primary arms comprises a primary switch 18a, 20a, also denoted K2 and KL

[0046] The secondary switching branch 4b comprises two arms, respectively a first secondary arm 14b connected between the first secondary terminal 6b and the secondary midpoint 10b, and a second secondary arm 16b connected between the second secondary terminal 8b and the secondary midpoint 10b.

[0047] Each of the first and second secondary arms comprises a secondary switch 18b, 20b, also denoted K4 and K3.

[0048] Each switch of the elementary piezoelectric converter 2, namely each of the switches 18a, 18b, 20a, 20b, is preferably a bidirectional current and unidirectional voltage switch, and comprises for example a transistor, or a diode, or even a transistor and a diode in antiparallel, not shown.

[0049] The use of a bidirectional voltage switch is required for the primary arms 14a and 16a if the primary voltage is likely to change sign, for example if it is an alternating voltage with change of polarity. Similarly, the use of a two-way voltage switch is required for secondary arms 14b and 16b if the secondary voltage is likely to change sign, for example if it is an alternating voltage with change of polarity.

[0050] The switch 18a, 18b, 20a, 20b is preferably made up of the transistor, or the diode, or the transistor and the diode in antiparallel.

[0051] Alternatively, the switch 18a, 18b, 20a, 20b comprises an association of several transistors, and is preferably made up of such an association of several transistors.

[0052] As a further variant, the switch 18a, 18b, 20a, 20b comprises a mechanical switch, such as a MEMS (MicroElectroMechanical System) micro-switch.

[0053] The transistor is, for example, an insulated gate field effect transistor, also called MOSFET (from the English Metal Oxide Semiconductor Field Effect Transistor). Alternatively, the transistor is a bipolar transistor; an insulated gate bipolar transistor, also called IGBT (from the English Insulated Gate Bipolar Transistor); a silicon (Si) based transistor, a GaN (from the English Gallium Nitride) based transistor; a silicon carbide (SiC) based transistor, or a diamond based transistor, or even a thyristor.

[0054] A piezoelectric assembly 22 is connected between the primary midpoint 10a and the secondary midpoint 10b.

[0055] The piezoelectric assembly 22 comprises one or more piezoelectric element(s) 15, each composed of a piezoelectric material having an associated resonant frequency.

[0056] As known per se, the mechanical oscillation of the piezoelectric elements 15 is approximately sinusoidal over respective resonance cycles, also called resonance periods. When several piezoelectric elements are present, the total mechanical deformation of the piezoelectric elements 15 is the sum of elementary mechanical deformations of each of the piezoelectric elements 15.

[0057] An increase or decrease in the energy stored over a period leads respectively to an increase or decrease in the oscillation amplitude.

[0058] The voltage Vpx at the terminals of the piezoelectric assembly 22 is dependent on the states of the respective switches K1, K2, K3, K4, capable of being controlled to alternate phases at substantially constant voltage and phases at substantially constant load.

[0059] By substantially constant charge is meant an exchange of a charge with the outside which is less than 30% of the charge which would have been exchanged with the outside if the voltage had been kept constant. In other words, by substantially constant charge is meant a variation in charge less than 30% of the charge which would have been exchanged with the exterior of the piezoelectric assembly 22 if the voltage across the terminals of the piezoelectric assembly 22 had been kept constant over the time period considered.

[0060] By substantially open electrical circuit, we mean a circuit in which a possible leakage current leads to a variation in charge of the piezoelectric assembly 22 of less than 30% of the charge which would have been exchanged with the exterior of the piezoelectric assembly 22 if the voltage across the terminals of the piezoelectric assembly 22 had been kept constant over the time period considered.

[0061] By substantially constant voltage is meant a voltage variation of less than 20%, preferably less than 10%, of the input or output voltage of the converter 10. For example, if the input voltage of the converter 10 is equal to 100V, then the voltage variation during each phase at substantially constant voltage, i.e. on each step at substantially constant voltage, is less than 20% of this voltage, i.e. less than 20V; preferably less than 10% of this voltage, i.e. less than 10V. Each phase at substantially constant voltage is also called a voltage step.

[0062] A modeling around a resonance mode of a piezoelectric element 15 in the form of an electric circuit is illustrated in bubble 25 in [Fig.l].

[0063] The piezoelectric element 15 is known per se, and is typically modeled, close to the resonance mode used, in the form of a capacitor 24 and a resonant branch 26 connected in parallel with the capacitor 24, the capacitor 24 and the resonant branch 26 being connected between a first electrode 28 and a second electrode 30 of the piezoelectric element 15. For example, when the set 22 of piezoelectric elements of the elementary piezoelectric converter is reduced to a piezoelectric element, the first electrode 28 is connected to the primary midpoint 10a and the second electrode 30 is connected to the secondary midpoint 10b.

[0064] The resonant branch 26 is typically an RLC branch formed of a resistor 32, a capacitor 34, and a coil 36 connected in series. The capacitance Co of the capacitor 24 connected in parallel with the resonant branch 26 is called the parallel capacitance, or blocked capacitance, or reference capacitance. The voltage across the terminals of the piezoelectric element 15 then typically corresponds to the voltage across the terminals of the capacitor 24. A substantially sinusoidal current iL flows in the piezoelectric element 15, in the resonant branch of its equivalent model.

[0065] The respective values ​​of the resistance R, of the capacitance C of the capacitor 34, and of the inductance L of the coil 36, as well as of the reference capacitance Co define the dimensioning of the piezoelectric element 15.

[0066] [Fig.2] schematically illustrates an electronic electrical energy conversion system 35, configured to supply electrical energy to a load 39 from from a source 37.

[0067] The electronic electrical energy conversion system 35 comprises an electrical energy converter 40 and an electronic control device 42 for the electrical energy converter 40.

[0068] The electrical energy converter 40 is configured to convert an input voltage Vin into an output voltage Vout. The electrical energy converter 40 comprises a first input terminal 44 and a second input terminal 46, a first output terminal 48 and a second output terminal 50.

[0069] In the case where the input and output electrical voltages are continuous, the electrical energy converter 40 being a direct-direct converter capable of converting a direct electrical energy or voltage into another direct electrical energy or voltage, the potential Vinn applied to the first input terminal 44 is lower than the potential Vinp applied to the second input terminal 46 and the potential V outn supplied to the first output terminal 48 is lower than the potential Voutp applied to the second output terminal 50.

[0070] To simplify the description, in the presence of an input voltage Vin which changes sign, the potentials Vinn and Vinp are then redefined at each instant so that Vinn is less than Vinp. Similarly, in the case of supplying an output voltage which changes sign, Voutn and Voutp are then redefined at each instant so that Voutn is less than Voutp. Note that we consider a control cycle frequency at least 10 times higher than the frequency of variation of the primary voltage, advantageously at least 100 times, so that during a control cycle, the input voltage Vin and the output voltage Vout can be considered substantially constant and without change of sign. The electrical energy converter 40 is preferably a DC-DC converter capable of converting a DC electrical energy or voltage into another DC electrical energy or voltage on the scale of a control cycle.

[0071] The electronic electrical energy conversion system 35 is for example a DC-DC conversion system capable of converting a first DC electrical energy or voltage received at the input into a second DC electrical energy or voltage delivered at the output, or even an AC-DC conversion system capable of converting an AC electrical energy or voltage received at the input into a DC electrical energy or voltage delivered at the output of the electrical energy conversion system.

[0072] For example, the electrical energy source 37 is a battery, a solar panel, an alternating voltage rectified by a diode bridge, a DC power bus. More generally, any other electrical energy source can be used, for example an AC or DC electrical network. In addition, to stabilize the input voltage, advantageously- nicely an electrical capacity can be added in parallel with Vin

[0073] The load 39 at the output of the electrical energy converter 40 is for example a battery. Generally, any electrical load 39 can be connected at the output, for example an electronic device, a motor, a resistive load, etc. Furthermore, to stabilize the output voltage, advantageously an electrical capacitor can be added in parallel with Vout.

[0074] When the electrical energy conversion system is an AC-DC conversion system, with for example an AC voltage centered on 0V, the electrical energy conversion system preferably further comprises a voltage rectifier, not shown, connected to the input of the electrical energy converter 40 and capable of rectifying the AC electrical voltage received at the input of the conversion system to deliver a rectified electrical voltage at the input of the converter 40. The voltage rectifier is for example a rectifier bridge, such as a diode bridge.

[0075] Note however that this rectifier is only of interest if the change in polarity of the input voltage Vin induces a change in polarity on the primary arms (Vxah-Vxai). To only have to manage a single voltage polarity (Vxah-Vxai), it may be wise to place a rectifier bridge just upstream of these primary arms and not necessarily at the input of the converter.

[0076] Alternatively, the use of bidirectional voltage switches 18a, 20a makes it possible to dispense with any voltage rectifier in the event of alternating sign on the voltage across the primary arms (Vxah-Vxai). In the latter case (Vxah-Vxai) can alternate sign, but it is sufficient, in terms of representation, depending on the polarity of the voltage (Vxah -Vxai), to consider Vxah>Vxai. Thus, in the event of negative voltage alternation, it is sufficient to consider for this alternation a converter with Vxah and Vxai permuted, to redescribe the converter considering this permutation to find the operation considering Vxah>Vxai. In the following, to simplify the description, we will consider Vxah always greater than Vxal, knowing that we can always, at any time, define a Vxah and a Vxai such that Vxah>Vxai.Similarly, in the following, we will always consider Vinp greater than Vinn, knowing that we can always, at any time, define a V inp and a Vinn such that Vinp>Vinn. Note that we consider a control cycle frequency at least 10 times greater than the frequency of variation of the primary voltage, advantageously at least 100 times, so that during a control cycle, the primary voltage can be considered substantially constant and without change of sign. The electrical energy converter 40 is preferably a DC-DC converter capable of converting a DC electrical energy or voltage into another DC electrical energy or voltage on the scale of a control cycle.

[0077] Similarly for the secondary arms, it is possible to generate an alternating voltage with change of polarity using bidirectional voltage switches 18b, 20b. To do this, it is sufficient to redefine Vxbh and Vxhi at each instant according to the polarity at the secondary, to find a configuration such that Vxbh>Vxbi. In the following, to simplify the description, we will consider Vxbh always greater than Vxbl, knowing that we can always, at each instant, define a Vxbh and a VxM such that Vxbh>Vxbb Note that we consider a control cycle frequency at least 10 times greater than the frequency of variation of the primary voltage, advantageously at least 100 times, so that during a control cycle, the secondary voltage can be considered substantially constant and without change of sign.

[0078] The electrical energy converter 40 advantageously comprises at least two elementary piezoelectric converters 2, connected in series via their respective primary switching branches 4a or via their respective secondary switching branches 4b, between two terminals among the first, the second input terminal, the first and the second output terminal.

[0079] Several examples of embodiments of electrical energy converters 40 are described below.

[0080] [Fig.3] illustrates an embodiment of an electrical energy converter 40 comprising N elementary piezoelectric converters, N being equal to 3 in the non-limiting example illustrated.

[0081] Generally, the number N is any number greater than or equal to 2.

[0082] The embodiment of [Fig.3] is more particularly advantageous for producing a converter with a high voltage drop or a strongly step-down converter.

[0083] In this embodiment, the primary switching branches 4ab 4a2, 4a3 of the elementary piezoelectric converters 2b 22 and 23 are connected in series, while the secondary switching branches 4bb 4b2, 4b3 of the elementary piezoelectric converters 2b 22 and 23 are connected in parallel.

[0084] The series connection is made by connecting the first primary terminal of the elementary piezoelectric converters 22 and 23 to the second primary terminal of another of said elementary piezoelectric converters 2b 22

[0085] More precisely, in detail, the first primary terminal of the elementary piezoelectric converter 2i is connected to the first input terminal 44 of the electrical energy converter 40 at a connection point noted 52; the second primary terminal of the elementary piezoelectric converter 2i is connected to the first primary terminal of the elementary piezoelectric converter 22 at a connection point noted 54; the second primary terminal of the elementary piezoelectric converter 22 is connected to the first primary terminal of the elementary piezoelectric converter 23 at a connection point noted 56; the second primary terminal of the elementary piezoelectric converter 23 is connected to the second input terminal 46 at a connection point marked 58.

[0086] Thus, in this example, the elementary piezoelectric converters 2b 22 and 23 are connected in series via their primary switching branches 4ab 4a2, 4a3 between the first input terminal 44 and the second input terminal 46. In other words, the electrical energy converter 40 of [Fig.3] comprises a 3-level series stage at the input.

[0087] On the secondary side, in this embodiment, the first secondary terminals 6b b 6b2 and 6b3 of the elementary piezoelectric converters 2b 22 and 23 are connected to the first output terminal 48 and the second secondary terminals 8bb 8b2 and 8b3 of the elementary piezoelectric converters 2b 22 and 23 are connected to the second output terminal 50.

[0088] Furthermore, in this embodiment, capacitors 60b 602, 603, of respective capacitances Cia, C2a, C3a are connected respectively in parallel with the primary switching branches 4ab 4a2, 4a3 of the elementary piezoelectric converters 2i, 22 and 23. According to the architecture presented, the capacitor 60i is connected between the connection points 52 and 54, the capacitor 602 is connected between the connection points 54 and 56 and the capacitor 603 is connected between the connection points 56 and 58.

[0089] Thus, the first elementary piezoelectric converter 2i receives as input a first voltage Vinb, the second elementary piezoelectric converter 22 receives as input a second voltage Vin2 and the third elementary piezoelectric converter 23 receives as input a second voltage Vin3>each of the first voltages Vini, Vin2 and Vin3 being equal to a fraction of the input voltage Vin, their sum being equal to the input voltage Vin.

[0090] Furthermore, in the embodiment of [Fig.3], a capacitor 62 is connected in parallel with the secondary switching branches 4bb 4b2, 4b3 of the elementary piezoelectric converters 2b 22 and 23. The capacitor 62 is thus shared at the output of the secondary switching branches of the elementary piezoelectric converters 2i, 22 and 23.

[0091] For example, capacitor 62 has a capacitance Cs.

[0092] The purpose of these capacitors is to filter the voltage with respect to the ripples of current induced at the frequency of the driving cycle, to filter the voltage at the terminals of the primary arms for the capacitors 60b 602, 603, and at the terminals of the secondary arms for the capacitor 62. If a capacitor 60, 62 is directly in parallel with a low impedance voltage source or a load, such as a low impedance battery, or in series between a source and a load of low impedances, then this capacitor can be omitted, the source and / or the load ensuring this filtering. on the other hand, on the side of the series connection of arms, namely the capacitors 60i, 602, 603, in the example of [Fig.3], are useful for stabilizing the voltages across the respective primary arms, no source / load being connected in parallel to help stabilize the voltages.

[0093] According to an optional variant, additional capacitors 64b 642, 643 are connected in series with the piezoelectric resonator assemblies 22b 222 and 223 of the elementary piezoelectric converters 2b 22 and 23. This advantageously makes it possible to protect the electrical energy converter 40 in the event of failure of one or more of the piezoelectric resonator assemblies 22b 222 and 223. Indeed, in the event of failure and generation of a short circuit of a piezoelectric resonator assembly 22j, the additional capacitor 64j makes it possible to prevent one of the potentials Vinn or V inp attached to the input voltage from being connected to one of the output terminals.Thanks to the presence of such an additional capacitor 64jun, degraded mode operation of the electrical energy converter 40 is maintained in the event of failure of one of the piezoelectric resonator assemblies, which allows its use in applications requiring a high level of electrical safety, for example avionics applications.

[0094] The elementary piezoelectric converters 2b 22, 23 are controlled by the electronic control device 42 which applies control sequences per control cycle. Examples of control sequences will be described below with reference to FIGS. 8 to 10.

[0095] [Fig.4] illustrates a variant of the embodiment of an electrical energy converter 40 of [Fig.3].

[0096] In this variant, the secondary switching branches 4b b 4b2, 4b3 of the elementary piezoelectric converters 2b 22 and 23 are shared, or in other words replaced by a single secondary switching branch 4b. In other words, the elementary piezoelectric converters 2b 22 and 23 share the same secondary switching branch.

[0097] This embodiment is advantageous because the number of switches is reduced, and the control of the switches of the secondary switching branch is synchronized, and consequently facilitated.

[0098] [Fig.5] illustrates another embodiment of an electrical energy converter 40 comprising N elementary piezoelectric converters, N being equal to 3 in the non-limiting example illustrated.

[0099] The architecture of the electrical energy converter 40 in the embodiment of [Fig.5] is "mirrored" with respect to the architecture of the electrical energy converter 40 illustrated in [Fig.4].

[0100] In the embodiment of [Fig.5], the electrical energy converter 40 comprises a primary switching branch 4a shared for the elementary piezoelectric converters 2b 22 and 23, while the secondary switching branches 4bb 4b2, 4b3 of the elementary piezoelectric converters 2b 22 and 23 are connected in series.

[0101] Thus, in this example, the elementary piezoelectric converters 2b 22 and 23 are connected in series via their secondary switching branches 4b b 4b2, 4b3 between the first output terminal 48 and the second output terminal 50. In other words, the electrical energy converter 40 of [Fig.5] comprises a 3-level series stage at the output.

[0102] Furthermore, in the embodiment of [Fig.5], a shared capacitor 60 is connected in parallel with the shared primary switching branch 4 of the elementary piezoelectric converters 2b 22 and 23. On the secondary side, respective capacitors 62b 622, 623 of capacitances Clb; C2b, C3b are connected in parallel with each of the secondary switching branches 4bb 4b2, 4b3.

[0103] The embodiment of [Fig.5] is more particularly advantageous for producing a high voltage rise converter or high boost converter.

[0104] Of course, the person skilled in the art will similarly consider a highly boosted mirrored electrical energy converter architecture compared to the architecture described with reference to [Fig.3].

[0105] [Fig.6] illustrates another embodiment of an energy converter electric 40 comprising N elementary piezoelectric converters, N being equal to 3 in the non-limiting example illustrated.

[0106] In this embodiment, the electrical energy converter 40 has an architecture similar to that of the electrical energy converter of [Fig. 4], but the connections of the secondary switching branch are reversed. In other words, on the secondary side, in this embodiment, the first secondary terminal 6b, common to the elementary piezoelectric converters 2b 22 and 23 is connected to the second output terminal 50 and the second secondary terminal 8b of the elementary piezoelectric converters 2b 22 and 23 is connected to the first output terminal 48.

[0107] In this embodiment, the electrical energy converter 40 obtained is also inverting, the potential Voutn is of opposite polarity to the potential Vinp taking Vinn as zero potential reference.

[0108] Preferably, for the purpose of optimizing the efficiency of the electrical energy converter, the switching branches connected in series are the switching branches located on the side of the highest voltage, i.e. primary side for a step-down electrical energy converter architecture and secondary side for a step-up electrical energy converter architecture.

[0109] For example, advantageously, the number of elementary piezoelectric converters and their series connection arrangement is chosen so that the voltage across the terminals of the primary switching branch of each elementary piezoelectric converter is close to the voltage across the terminals of the secondary switching branch.

[0110] By close is meant within 50%, and advantageously within 25%.

[0111] In terms of simplicity of control, it is advantageous for each piezoelectric converter to operate in voltage step-down mode, i.e. the voltage on its secondary branch is lower than the voltage on its primary branch, advantageously the voltage gain is between 0.5 and 1.

[0112] [Fig.7] illustrates another embodiment of an electrical energy converter 40 comprising N elementary piezoelectric converters, N being equal to 3.

[0113] In this embodiment, the 3 elementary piezoelectric converters 2b 22 and 23 are connected in series via their respective primary switching branches 4ab 4a2, 4a3, the secondary switching branches 4bb 4b2, 4b3, being connected in parallel.

[0114] Unlike the embodiment illustrated in [Fig.3], the primary switching branches 4ab 4a2, 4a3 connected in series are connected between the second input terminal 46 of potential Vinp and the second output terminal 50 of potential Voutp.

[0115] More precisely, in detail, the first primary terminal 6ai of the elementary piezoelectric converter 2i is connected to the second input terminal 46 of the electrical energy converter 40 at a connection point denoted 52'; the second primary terminal 8ai of the elementary piezoelectric converter 2i is connected to the first primary terminal 6a2 of the elementary piezoelectric converter 22 at a connection point denoted 54'; the second primary terminal 8a2 of the elementary piezoelectric converter 22 is connected to the first primary terminal 6a3 of the elementary piezoelectric converter 23 at a connection point denoted 56'; the second primary terminal 8a3 of the elementary piezoelectric converter 23 is connected to the second output terminal 50 at a connection point denoted 58'.

[0116] On the secondary side, in this embodiment, the first secondary terminals 6b i, 6b2 and 6b3 of the elementary piezoelectric converters 2b 22 and 23 are connected to the first output terminal 48 and the second secondary terminals 8bb 8b2 and 8b3 of the elementary piezoelectric converters 2b 22 and 23 are connected to the second output terminal 50.

[0117] The electrical energy converter of [Fig.7] is particularly suitable for producing a strongly step-down converter. It also has the advantage that the The current flowing through the primary switching branches contributes to the output current, in addition to the current supplied by the secondary switching branches. This current, which flows directly through the primary switching branches to the output, does not need to pass through the piezoelectric resonators, which increases efficiency and allows the size of the piezoelectric resonators to be reduced (less current flowing through the piezoelectric resonators).

[0118] Of course, it is easy to envisage a mirrored electrical energy converter architecture compared to that of [Fig.7], in which the secondary switching branches of the elementary piezoelectric converters 2b 22 and 23 are connected in series between the second input terminal 46 and the second output terminal 50, and the primary switching branches are connected in parallel between the first and second input terminals.

[0119] An electrical energy converter 40 according to the invention can be controlled by the electronic control device 42 according to a number of voltage levels at substantially constant voltage chosen.

[0120] In one embodiment, the electronic control device 42 is configured to control each of the elementary piezoelectric converters of the electrical energy converter 40.

[0121] The electronic control device 42 is configured, depending on the architecture of the electrical energy converter 40, to control the closing or opening of each of the switches to respectively carry out an alternation of phases at substantially constant voltage (or voltage steps) and phases at substantially constant load over a control cycle for each elementary piezoelectric converter.

[0122] The electronic control device 42 is for example produced in the form of an electronic circuit comprising one or more electronic components.

[0123] Alternatively, the electronic control device 42 is produced in the form of a programmable logic component, such as an FPGA (Field Programmable Gate Array) or in the form of an integrated circuit, such as an ASIC (Application Specific Integrated Circuit) or even in the form of a computer, such as a microcontroller, a processor.

[0124] In all embodiments, each of the elementary piezoelectric converters can receive substantially the same control sequence. Alternatively, the sequences are substantially identical but are interleaved, i.e. have a phase shift, which makes it possible to better distribute the power exchanges over time. As a further variant, in the case of an even number N of elementary piezoelectric converters, the converters can receive commands in phase opposition 2 by 2, i.e. shifted by a half-period or a half-cycle, which which has the effect of compensating certain disturbances by symmetry and reducing the electromagnetic disturbances of the converter.

[0125] Furthermore, it is advantageous, even if they are out of phase, for the control sequences to be substantially identical so that the primary or secondary arms placed in series share the voltage well, when the converters exchange substantially identical power.

[0126] In the case of the same control sequence reproduced, with a possible phase shift, to control each of the piezoelectric converters, this sequence can be directly adjusted with regard to the voltage Vout, the current Iout or the desired output power Vout*Iout via a regulation loop.

[0127] As a variant, the electronic control device 42 comprises, for each elementary piezoelectric converter, a dedicated regulation circuit for, on the one hand, properly sharing the voltage on the switching branches placed in series on the primary side and / or the secondary side and, on the other hand, regulating the voltage Vout, the current Iout or the output power Vout*Iout.

[0128] Figures 8, 9 and 10 illustrate control sequences of an elementary piezoelectric converter 2 comprising a piezoelectric assembly 22 with piezoelectric element Px;

[0129] Figures 8 and 9 illustrate respective curves of total mechanical deformation of a piezoelectric assembly 22 and a curve of current IL flowing in a piezoelectric assembly, as well as curves of evolution of the voltage Vpxdyn and associated switch control configurations for producing voltage step-down ([Fig.8]) and voltage step-up ([Fig.9]) type configurations in three-step control at substantially constant voltage per control cycle.

[0130] [Fig. 10] illustrates a four-stage control at substantially constant voltage, on the one hand in step-down mode, on the other hand in step-up mode.

[0131] The voltage Vpxdyn is equal to the voltage Vpx across the terminals of the piezoelectric assembly from which the common mode component Vpxmc defined by the expression is subtracted:

[0132] Vpxmc=(Vxah+Vxal) / 2-(Vxbh+Vxbl) / 2

[0133] In the various electrical energy converter configurations described above, each of the elementary piezoelectric converters is controlled according to a step-down or step-up cycle.

[0134] The voltages Vxa and Vxb are obtained as a function of the voltages Vxah, Vxai at the terminals of its primary switching branch and Vxbh, Vxbi at the terminals of its secondary switching branch: Vxa=(Vxah-Vxai) / 2 and Vxb=(Vxbh-Vxbi) / 2.

[0135] The voltage Vxa represents the amplitude of the primary voltage relative to a central point Vxamc defined by the expression: Vxamc=(Vxai+Vxah) / 2, and is also called the amplitude of the dynamic input voltage.

[0136] The voltage Vxb represents the amplitude of the primary voltage relative to a central point Vxbmc defined by the expression: Vxbmc=(Vxbi+Vxbh) / 2, and is also called the amplitude of the dynamic output voltage.

[0137] We consider that the potentials at the terminals of the primary and secondary switching branches, in steady state, are substantially constant over the scale of a control cycle (variation less than 20% of the largest voltage among Vin or Vout, advantageously less than 5%).

[0138] Due to its capacitive behavior, the piezoelectric resonator is not sensitive to DC voltage components. It is then possible, in terms of functional representation, to remove the common mode Vxamc at the primary and Vxbmc at the secondary. Note that the common mode Vxamc or Vxbmc as defined here is not necessarily the average value of Vxar or Vxbr, it may remain a non-zero average component, in particular if, for example, for Vxar, Kl and K2 are not closed over identical durations. This is therefore an equivalent of a change of reference where a DC component has been removed and which is not necessarily the average value.

[0139] The voltage Vpx across the piezoelectric assembly can take the following values: Vpx=Vxamc-Vxbmc+ / -Vxa+ / -Vxb

[0140] The dynamic component Vpxdyn of this voltage, or dynamic voltage across the terminals of the piezoelectric assembly, simply called dynamic voltage Vpxdyn hereinafter, can take the following voltage step values: Vpxdyn=Vpx-(Vxamc-Vxbmc)= + / -vxa+ / -vxb

[0141] There are 4 possible voltage step values: • Vpxdyn=Vxa+Vxb (Kl and K4 closed and K2 and K3 open) • Vpxdyn=Vxa-Vxb (Kl and K3 closed and K2 and K4 open) • Vpxdyn= -Vxa+Vxb (K2 and K4 closed and Kl and K3 open) • Vpxdyn= -Vxa-Vxb (K2 and K3 closed and Kl and K4 open)

[0142] In the example described with reference to Figures 8 and 9, each cycle comprises 6 phases, respectively phases I, III and V at substantially constant charge and phases II, IV and VI at substantially constant voltage.

[0143] By convention, if power is supplied to the piezoelectric assembly 22 during phase II, IV, VI at substantially constant voltage corresponding to the highest voltage during a resonance cycle, then the cycle is considered a step-down cycle for the piezoelectric assembly 22. Conversely, if power is delivered, or drawn, from the piezoelectric assembly during said phase II, IV, VI at substantially constant voltage for which the voltage is the highest during the resonance cycle, then the cycle is considered a step-up cycle for the piezoelectric assembly 22.

[0144] In [Fig.8] two step-down configurations A1 and A3 are presented without mode ZVS (from the English "Zero Voltage Switch"), and two step-down configurations A2 and A4 with ZVS mode. The ZVS mode ensures that the switches close when the voltage across their terminals is low, preferably zero, to achieve zero voltage switching.

[0145] The piloting is angular over a piloting cycle of 0 to 2ir radians.

[0146] In the step-down configurations A1 and A3, phase I extends from 0 to phase II extends from 0x to 02, phase III from 02 to 03, phase IV from 03 to 04, phase V from 04 to 05, phase VI from 05 to 06, where 03=ir and 06=2ir. In other words, 03 corresponds to a half-cycle of control.

[0147] By convention, for the first step-down configuration A1, the highest voltage level for the dynamic voltage Vpxdyn is that at the value Vxa-Vxb. During this level, power is supplied to the piezoelectric assemblies 12A, 12B. By convention, the current IL flowing in the piezoelectric elements 15, i.e. in the piezoelectric assembly 22, is oriented so as to be positive during this voltage level at the value Vxa-Vxb. Consequently, at constant load, the dynamic voltage VpXdyn tends to decrease when the current IL is positive, and consequently to increase when the current IL is negative.

[0148] Conversely, by convention, for the third step-down configuration A3, the highest voltage level for the dynamic voltage Vpxdyn is that at the value Vxa+Vxb. During this level, power is delivered, or drawn, from the piezoelectric assembly 22. By convention, the current IL flowing in the piezoelectric elements 15 is oriented so as to be positive during this voltage level at the value Vc. Consequently, at constant load, the dynamic voltage Vpxdyn tends to increase when the current IL is positive, and consequently to decrease when the current IL is negative.

[0149] As can be seen, the evolution of the voltage Vpxdyn in the step-down configuration A3 is symmetrical, by inversion of signs (or inversion of polarity), to the evolution of the voltage Vpxdyn in the step-down configuration AL

[0150] In [Fig.8], the second step-down configuration A2 differs from the first step-down configuration Al, described previously, only in that it incorporates an excursion to the voltage VZvs equal to +Vxa+Vxb.

[0151] This voltage excursion makes it possible to move from the dynamic voltage level equal to -Vxa+Vxb to the voltage level equal to Vxa-Vxb in ZVS switching at the switches.

[0152] This transition is made in two stages, a first stage from angle 02 to angle 03 to pass from the dynamic voltage Vpxdyn equal to -Vxa+Vxb to the dynamic voltage Vpxdyn equal to Vxa+Vxb, then a second stage from angle 03 to angle 03b to pass from the dynamic voltage Vpxdyn equal to Vxa+Vxb to the dynamic voltage Vpxdyn equal to Vxa-Vxb.

[0153] The behavior is analogous in the A4 step-down configuration, in polarity reversed.

[0154] The switching diagrams Com-1, Com-2, Com-3 and Com-4 illustrate the switching of the respective switches K1, K2, K3 and K4 to carry out cycles I to VI in the step-down configuration A4.

[0155] The switching diagrams illustrate the phases during which the respective switches are closed (diagram corresponding to the high state) or open (low state).

[0156] The hatched parts of [Fig.8] represent phases during which the holding in the on position can be done naturally, via an intrinsic reverse diode of the switches, or via an additional parallel diode. Note here that the switches K3 and K4 having respectively Com-3 and Com-4 as control, are only in conduction in the hatched zone, consequently they can consist of only a simple diode.

[0157] In [Fig.9] are presented two booster configurations E1 and E3 without ZVS mode (from the English "Zero Voltage Switch"), and two booster configurations E2 and E4 with ZVS mode. The ZVS mode ensures the closing of the switches when the voltage at their terminals is low, preferably zero, to achieve zero voltage switching.

[0158] The piloting is angular on a piloting cycle of 0 to 2ir radians.

[0159] In the elevator configurations E1 and E3, phase I extends from 0 to 0b phase II extends from 0x to 02, phase III from 02 to 03, phase IV from 03 to 04, phase V from 04 to 05, phase VI from 05 to 06, where 03=ir and 06=2ir. In other words, 03 corresponds to a half-cycle of piloting.

[0160] During the first phase I, the sign of the current IL leads to an increase in the dynamic voltage Vpxdyn. The dynamic voltage Vpxdyn therefore changes from the value Vxa-Vxb to the value -Vxa+Vxb. After the voltage plateau of phase II, the dynamic component of the dynamic voltage Vpxdyn changes during phase III to Vxa+Vxb, then drops to Vxa-Vxb during phase V.

[0161] Conversely, by convention, for the third booster configuration E3, the highest voltage level for the dynamic voltage Vpxdyn is that at the value Vxa-Vxb. During this level, power is delivered, or drawn, from the piezoelectric assembly 22. By convention, the current IL flowing in the piezoelectric elements 15 is oriented so as to be positive during this voltage level at the value Vc. Consequently, at constant load, the dynamic voltage Vpxdyn tends to increase when the current IL is positive, and consequently to decrease when the current IL is negative.

[0162] As can be seen, the evolution of the dynamic voltage Vpxdyn in the E3 booster configuration is symmetrical, by inversion of signs, to the evolution of the voltage Vpxdyn in the EL booster configuration.

[0163] In [Fig.9], the second booster configuration E2 differs from the first booster configuration El described previously, only in that it integrates an excursion to the voltage VZvs equal to -Vxa-Vxb at the transition from phase VI to phase I.

[0164] This voltage excursion makes it possible to move from the level equal to Vxa-Vxb to the level equal to -Vxa+Vxb in ZVS switching at the switches. This transition is done in two stages, a first stage between the angle 05b and 06(2ir, and therefore 0) to move from the dynamic voltage Vpxdyn equal to Vxa-Vxb to the dynamic voltage Vpxdyn equal to -Vxa-Vxb, then a second stage between 0O and 0i to move from the dynamic voltage Vpxdyn equal to -Vxa-Vxb to the dynamic voltage Vpxdyn equal to -Vxa+Vxb.

[0165] The behavior is analogous and of opposite signs (or reversed polarity) in the E4 elevator configuration.

[0166] The switching diagrams Com-1, Com-2, Com-3 and Com-4 illustrate the switching of the respective switches K1, K2, K3 and K4 to carry out cycles I to VI in the step-up configuration E2.

[0167] The switching diagrams illustrate the phases during which the respective switches are closed (diagram corresponding to the high state) or open (low state).

[0168] The hatched parts of [Fig.9] represent phases during which the switches K3 and K4 can be kept in the on position naturally, via an intrinsic reverse diode of the switches, or via an additional parallel diode.

[0169] It is clear to a person skilled in the art that other types of control, for example controls with another number of steps at substantially constant voltage, are applicable for controlling the electrical energy converters according to the invention.

[0170] [Fig. 10] illustrates a four-stage control at substantially constant voltage, on the one hand in step-down mode, on the other hand in step-up mode.

[0171] In [Fig. 10] are represented: the curve of current IL flowing in the resonant branch of the equivalent electrical model of a piezoelectric assembly is illustrated over a resonance cycle ranging from 0 to 2ir; in parallel, curves of evolution of the voltage Vpxdyn in voltage step-down mode (A*) and in voltage step-up mode (E*) in four-step control at substantially constant voltage over a control cycle equal, in the example of [Fig. 10], to a resonance cycle of the piezoelectric assembly.

[0172] In voltage step-down mode, Vxa is greater than Vxb. The evolution of the dynamic component of the piezoelectric voltage (or dynamic voltage) Vpxdyn over a control cycle between 0 and 2ir is illustrated in graph A*.

[0173] In this step-down configuration, the control cycle, equal to the operating period in this example, comprises two half-cycles.

[0174] The first half-cycle comprises two phases I, III at substantially constant charge and two phases II, IV at substantially constant voltage, defined between respective angles 0;.

[0175] In detail, between 0O and 0B during phase I at substantially constant load, the dynamic component of the piezoelectric voltage Vpxdyn changes from -Vxa-Vxb (K2 and K3 closed and Kl and K4 open) to -Vxa+Vxb (K2 and K4 closed and Kl and K3 open).

[0176] During phase II at substantially constant voltage, between 0i and 02, the dynamic component of the piezoelectric voltage Vpxdyn is substantially equal to -Vxa+Vxb.

[0177] During phase III at substantially constant load, between 02 and 02b, the value of the dynamic component of the piezoelectric voltage Vpxdyn evolves between -Vxa+Vxb and V xa+Vxb (Kl and K4 closed, K2 and K3 open).

[0178] Finally, during phase IV at substantially constant voltage, between angles 02b and 03 =ji, the dynamic component of the piezoelectric voltage Vpxdyn is substantially equal to Vxa+Vxb.

[0179] The second half-cycle also comprises two phases V, VII at substantially constant charge and two phases VI, VIII at substantially constant voltage.

[0180] In detail, between 03 and 03b, during phase V at substantially constant load, the dynamic component of the piezoelectric voltage Vpxdyn changes from Vxa+Vxb to Vxa-Vxb (Kl and K3 closed, K2 and K4 open).

[0181] During phase VI at substantially constant voltage, between 03b and 04, the dynamic component of the piezoelectric voltage Vpxdyn is substantially equal to Vxa-Vxb.

[0182] During phase VII at substantially constant load, between 04 and 05, the dynamic component of the piezoelectric voltage Vpxdyn evolves between Vxa-Vxb and -Vxa-Vxb.

[0183] Finally, during phase VIII at substantially constant voltage, between angles 05 and 06 =2ir, the dynamic component of the piezoelectric voltage Vpxdyn is substantially equal to Vxa-Vxb.

[0184] The respective substantially constant voltage phases II, VI are of substantially the same duration, in other words 63 " ~ and the respective voltage values are substantially equal and of opposite signs.

[0185] Similarly, the respective substantially constant voltage phases IV, VIII are of substantially the same duration, in other words ^3 - ~ 0g - 0 g, and the values ​​of respective tensions are substantially equal and of opposite signs.

[0186] The evolution of the dynamic voltage Vpxdyn (or dynamic component of the piezoelectric voltage) over time in a voltage booster type configuration, in which Vxa <Vxb, est illustrée dans le graphe E*.

[0187] In this elevator type configuration, the pilot cycle, equal to the resonance / operating period in this example, comprises two half-cycles.

[0188] The first half-cycle comprises two phases I', III' at substantially the same voltage constant and two phases II', IV' at substantially constant load.

[0189] In detail, between 00 and 00b, during phase I' at substantially constant voltage, the dynamic voltage Vpxdyn is substantially equal to -Vxa-Vxb.

[0190] During phase II' at substantially constant load, between 0Ob and 0b the dynamic voltage Vpxdyn evolves between -Vxa-Vxb and -Vxa+Vxb.

[0191] During phase III' at substantially constant voltage, between 0i and 02, the dynamic voltage value Vpxdyn is substantially equal to -Vxa+Vxb.

[0192] Finally, during phase IV' at substantially constant load, between angles 02 and 03 =ji, the dynamic voltage Vpxdyn evolves between -Vxa+Vxb and Vxa+Vxb.

[0193] The second half-cycle also comprises two phases V', VII' at substantially constant voltage and two phases VI', VIII' at substantially constant charge.

[0194] In detail, between 03 and 04, during phase V' at substantially constant voltage, the dynamic voltage Vpxdyn is substantially equal to Vxa+Vxb.

[0195] During phase VI' at substantially constant load, between 04 and 05, the dynamic voltage Vpxdyn evolves between Vxa+Vxb and Vxa-Vxb.

[0196] During phase VII' at substantially constant voltage, between 05 and 05b, the dynamic voltage value Vpxdyn is substantially equal to Vxa-Vxb.

[0197] Finally, during phase VIII' at substantially constant load, between angles 05b and 06 =2ir, the dynamic voltage Vpxdyn evolves between Vxa-Vxbet -Vxa-Vxb.

[0198] Furthermore, the respective substantially constant voltage phases I', V' are of substantially the same duration, in other words ^2 " ~ $4" ®3b, and the values ​​of respective voltages are substantially equal and of opposite signs (respectively -V xa-Vxb and Vxa+Vxb.).

[0199] Similarly, the respective substantially constant voltage phases III', VII' are of substantially the same duration, in other words #2' ~ $5b~ #5 and the values ​​of respective voltages are substantially equal and of opposite signs (respectively V xa+Vxb and Vxa-Vxb.).

[0200] In each of the control (or piloting) configurations of the electrical energy converter, of the voltage step-down type or of the voltage step-up type, there is a symmetry in the evolution in the evolution of the dynamic voltage Vpxdyn between the two half-cycles, the evolution in the second half-cycle being obtained by translation of the evolution in the first half-cycle, with an opposite voltage polarity.

[0201] Furthermore, the voltage levels thus arranged per half-cycle of control, and more particularly in the example per half-period of resonance, are such that the respective voltage values ​​of the levels per half-cycle are of opposite polarities.

[0202] Generally, for both types of configurations, one of the voltage values ​​among the first voltage value and the second voltage value of the first half-cycle of driving is equal to the difference Vxa-Vxb or the opposite of the difference Vxb-Vxa between the amplitude of the dynamic input voltage Vxa and the amplitude of the dynamic output voltage Vxb, and the other voltage value among the first voltage value and the second voltage value is equal to the sum Vxa +Vxb or the opposite of the sum -Vxa-Vxb of the amplitude of the dynamic input voltage Vxa and the amplitude of the dynamic output voltage Vxb.

[0203] The electronic control device 42 is configured to control the respective switches at the primary and secondary to achieve the 4-voltage step configurations described above. For each phase at substantially constant voltage, one of the primary switches K1, K2 is closed (passing), while the other of the primary switches is open.

[0204] During the constant load phases, only a change of polarity is necessary either at the primary, passing from +Vxa to -Vxa or from -Vxa to +Vxa, or at the secondary, passing from +Vxb to -Vxb or from -Vxb to +Vxb. Thus, only Vxar or Vxbr changes potential, while the other potential among Vxar, Vxbr remains unchanged via a switch which remains conducting or closed. Consequently, the output of a phase at substantially constant voltage is carried out by the opening or blocking of a single switch and the output of a phase at constant load is carried out by the closing or conduction of a single switch. Furthermore, it is not necessary to change the switch configuration over the entire duration which separates 2 constant voltage levels, unlike the case of a cycle with 3 constant voltage levels as described in [Fig.8], for example between 02 and 03b.

[0205] Advantageously, in voltage step-down mode, only the primary switches K1, K2 are controlled, the conduction or blocking of the secondary switches K3, K4 being carried out naturally via an intrinsic diode of the switches or via an additional parallel diode.

[0206] Furthermore, it should be noted that the examples of electrical energy converters 40 described up to now all comprise two or more elementary piezoelectric converters, possibly comprising a common (or shared) switching branch.

[0207] It is clear that the invention also applies to elementary piezoelectric converters with switching bridge, i.e. comprising two primary switching branches and two secondary switching branches and sets of piezoelectric elements connected to the respective midpoints of one of the primary switching branches and one of the secondary switching branches.

[0208] The frequency of the driving cycle is equal to the frequency of the mechanical movement of the piezoelectric element(s) 15 or to a submultiple of this frequency. For a given resonance mode, the piezoelectric element 15 is typically operated between its so-called series resonance frequency (cos=l / 'V(LC) where L and C correspond to the inductance and capacitance of the resonant branch and the so-called parallel resonance frequency of the piezoelectric element 15 (œp=l / V(LCC( / (C+Co))), also respectively called resonance frequency and antiresonance frequency of the piezoelectric element 15. The frequency of the driving cycle is therefore between these two frequencies or between two frequencies which are sub-multiples of these two frequencies. In addition, the frequency of the driving cycle is typically adjusted between these two limit frequencies to adjust the output current and ultimately, for example, regulate the output voltage via a regulation loop.It is also possible to change the resonance mode on the resonator, for example switching from a thickness resonance mode to a radial or surface elongation resonance mode, or switching to a higher resonance mode to address different power ranges with improved efficiency.

[0209] An example of the architecture of an electrical energy converter 80 comprising elementary converters with switching bridge is illustrated in [Fig. 11].

[0210] In the example of an electrical energy converter of [Fig.l 1], the primary switching branches are connected in series between the first input terminal and the second input terminal, which makes it possible to divide the input voltage Vin into two input voltages substantially equal to Vin / 2.

[0211] Advantageously, the electrical energy converter presented, according to its various embodiments, makes it possible to divide the voltage at the input or output terminals of at least a portion of the elementary piezoelectric converters, and consequently to obtain a better electrical energy conversion efficiency.

Claims

Claims

1. Electrical energy converter (40, 80) capable of converting an input voltage (Vin) into at least one output voltage (Vout), the converter (40, 80) comprising a first input terminal and a second input terminal, the input voltage (Vin) being applied between the first input terminal and the second input terminal, and comprising a first output terminal and a second output terminal, the output voltage (Vout) being supplied between the first output terminal and the second output terminal, characterized in that it comprises at least two elementary piezoelectric converters (2, 2b 22, 23), each elementary piezoelectric converter (2, 2b 22, 23) comprising a primary switching branch (4a, 4ab 4a2, 4a3) and a secondary switching branch (4b, 4bb 4b2, 4b3), the primary switching branch (4a) comprising two arms primaries connected at a primary midpoint (10a),a first primary arm being connected between a first primary terminal and the primary midpoint, a second primary arm being connected between a second primary terminal and the primary midpoint, each of said primary arms comprising a primary switch (18a, 20a), the secondary switching branch (4b) comprising two secondary arms connected at a secondary midpoint (10b), a first secondary arm being connected between a first secondary terminal and the secondary midpoint, a second secondary arm being connected between a second secondary terminal and the secondary midpoint, each of said secondary arms comprising a secondary switch (18b, 20b), the elementary piezoelectric converter (2) comprising at least one piezoelectric element (15) connected between the primary midpoint (10a) and the secondary midpoint (10b), wherein at least two elementary piezoelectric converters (2, 2b 22,23) are connected in series via their primary switching branches (4a, 4ab 4a2, 4a3) and / or via their secondary switching branches (4b, 4bb 4b2, 4b3), between two terminals among the first input terminal (44), the second input terminal (46), the first output terminal (48) and the second output terminal (50).,

2. Converter according to claim 1, comprising at least two elementary piezoelectric converters (2b 22, 23) connected in series via their primary switching branches and connected in parallel via their secondary switching branches.

3. Converter according to claim 2, wherein said at least two elementary piezoelectric converters (2b 22, 23) connected in series via their primary switching branches (4ab 4a2, 4a3) share the same secondary switching branch (4b).

4. Converter according to claim 1, comprising at least two elementary piezoelectric converters (2b 22, 23) connected in parallel via their primary switching branches and connected in series via their secondary switching branches (4bb 4b2, 4b3).

5. Converter according to claim 4, wherein said at least two elementary piezoelectric converters (2b 22, 23) connected in series via their secondary switching branches share the same primary switching branch (4a).

6. Converter according to any one of claims 1 to 5, comprising at least one elementary piezoelectric converter called elementary input piezoelectric converter, the first primary terminal of said elementary input piezoelectric converter being connected to the first input terminal and / or the second primary terminal of said elementary input piezoelectric converter being connected to the second input terminal.

7. Converter according to any one of claims 1 to 6, comprising at least one elementary piezoelectric converter called elementary output piezoelectric converter, the first secondary terminal of said elementary output piezoelectric converter being connected to the first output terminal and / or the second secondary terminal of said elementary output piezoelectric converter being connected to the second output terminal.

8. Converter according to any one of claims 1 to 5, wherein said at least two elementary piezoelectric converters are connected in series via their primary switching branches or via their secondary switching branches, between a first terminal among the first input terminal and the second input terminal and a second terminal among the first output terminal and the second output terminal.

9. Converter according to any one of claims 1 to 8, comprising, for at least one of said elementary piezoelectric converters, a capacitor (60, 62) connected between the first terminal primary and the second primary terminal or between the first secondary terminal and the second secondary terminal.

10. Converter according to claim 9, comprising a plurality of elementary piezoelectric converters connected in series by their primary switching branches, wherein each of said elementary piezoelectric converters comprises a capacitor (60i, 602, 603) connected between the first primary terminal and the second primary terminal.

11. Converter according to claim 10, comprising a plurality of elementary piezoelectric converters connected in series by their secondary switching branches, wherein each of said elementary piezoelectric converters comprises a capacitor (62i, 622, 623) connected between the first secondary terminal and the second secondary terminal.

12. Electronic electrical energy conversion system comprising an electrical energy converter and an electronic device for controlling the electrical energy converter, characterized in that the electrical energy converter is in accordance with any one of claims 1 to 11.

13. System according to claim 12, in which the electronic control device is configured to control the primary and / or secondary switches of each of the elementary piezoelectric converters on a control cycle to alternate between phases at substantially constant load and phase at substantially constant voltage, a first half-cycle of control comprising a first phase at substantially constant voltage of first voltage and first duration, and a second phase at substantially constant voltage of second voltage and second duration, a second half-cycle of control comprising a third phase at substantially constant voltage of voltage opposite to the first voltage and of duration substantially equal to the first duration, and a fourth phase at substantially constant voltage of voltage opposite to the second voltage and of duration substantially equal to the second duration.

14. A system according to claim 13, wherein during each phase at substantially constant voltage, one of the primary switches and one of the secondary switches is in the closed position, and the other of the primary switches and the other of the secondary switches is open.

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