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

Abstract

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), the converter including at least two elementary piezoelectric converters (21, 22, 23), each including 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 branches (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).

Description

[0001] Electrical energy converter with piezoelectric element(s) and associated electronic electrical energy conversion system

[0002] The present invention relates to an electrical energy converter capable of converting an input voltage into at least one output voltage.

[0003] The invention also relates to an associated electrical energy conversion system.

[0004] 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.

[0005] 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.

[0006] 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 resonant 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.

[0007] As is well known, 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 piezoelectric elements is the sum of elementary mechanical deformations of each of the piezoelectric elements. An increase or decrease in the stored energy over a period leads to an increase or decrease in the oscillation amplitude, respectively.

[0008] 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.

[0009] An electrical energy converter controlled so that the input voltage Vj n is at least twice the output voltage V ou t is called a deep step-down converter. An electrical energy converter driven so that the input voltage Vj n is at least twice lower than the output voltage V ou t is called a high-voltage boost converter. The ratio of the highest voltage to the lowest voltage is called the conversion ratio.

[0010] 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.

[0011] 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 one elementary piezoelectric converter, 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. This converter is such that it comprises at least two elementary piezoelectric converters 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 at least one of the primary switching branches being connected to the first input terminal or the second input terminal and at least one of the secondary switching branches being connected to the first output terminal or the second output terminal.,

[0012] 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.

[0013] According to other advantageous aspects of the invention, the electrical energy converter comprises one or more of the following characteristics, taken individually or in all technically possible combinations.

[0014] Said at least two elementary piezoelectric converters are connected in series via their primary switching branches and connected in parallel via their secondary switching branches.

[0015] The at least two elementary piezoelectric converters connected in series via their primary switching branches share the same secondary switching branch.

[0016] Said at least two elementary piezoelectric converters are connected in parallel via their primary switching branches and connected in series via their secondary switching branches.

[0017] The at least two elementary piezoelectric converters connected in series via their secondary switching branches share the same primary switching branch.

[0018] At least one elementary piezoelectric converter of said at least two elementary piezoelectric converters is 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.

[0019] At least one elementary piezoelectric converter of said at least two elementary piezoelectric converters is called an 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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 being as briefly described above.

[0025] 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 phases 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.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] - figure 1 is a schematic representation of an elementary piezoelectric converter and of an electrical circuit corresponding to a piezoelectric element;

[0028] - Figure 2 is a functional representation of an electronic electrical conversion system;

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

[0030] - figure 4 schematically illustrates a variant of the electrical energy converter of figure 3;

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

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

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

[0034] - figure 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 step-down configurations, in three-stage control at substantially constant voltage;

[0035] - figure 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 booster configurations, in three-stage control at substantially constant voltage;

[0036] - figure 10 illustrates curves of the voltage evolution 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] - Figure 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 plus or minus 5%, unless otherwise indicated.

[0039] Figure 1 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 shown in Figure 1 has 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 has 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 Figure 1, a potential V xai is applied to the first primary terminal 6a, and a potential V xa h is applied to the second primary terminal 8a. By convention, the potential V xa i is less than the potential V xah. The potential at the primary midpoint 10a is denoted V xar .

[0043] The secondary switching branch 4b has 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 Figure 1, a potential V X bi is provided at the first secondary terminal 6b, and a potential V X bh is supplied at the second secondary terminal 8b. By convention, the potential V X bi is less than the potential V X bh. The potential at the secondary midpoint 10b is denoted V xbr .

[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 K1. 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.

[0046] Each of the first and second secondary arms has a secondary switch 18b, 20b, also denoted K4 and K3.

[0047] 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.

[0048] The use of a two-way 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 a change of polarity. Similarly, the use of a two-way voltage switch is required for the secondary arms 14b and 16b if the secondary voltage is likely to change sign, for example if it is an alternating voltage with a change of polarity.

[0049] The switch 18a, 18b, 20a, 20b is preferably made up of the transistor, or the diode, or the transistor and the diode in antiparallel.

[0050] 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.

[0051] Alternatively, the switch 18a, 18b, 20a, 20b comprises a mechanical switch, such as a MEMS (MicroElectroMechanical System) microswitch.

[0052] The transistor is, for example, an insulated gate field effect transistor, also called a MOSFET (from the English Metal Oxide Semiconductor Field Effect Transistor). Alternatively, the transistor is a bipolar transistor; an insulated gate bipolar transistor, also called an 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 a thyristor.

[0053] A piezoelectric assembly 22 is connected between the primary midpoint 10a and the secondary midpoint 10b.

[0054] The piezoelectric assembly 22 comprises one or more piezoelectric elements 15, each composed of a piezoelectric material having an associated resonance frequency. 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.

[0055] An increase or decrease in the energy stored over a period leads to an increase or decrease in the oscillation amplitude, respectively.

[0056] The voltage V pxat 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.

[0057] 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 outside 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.

[0058] By substantially open electrical circuit is meant 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.

[0059] 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.

[0060] A modeling around a resonance mode of a piezoelectric element 15 in the form of an electric circuit is illustrated in bubble 25 in figure 1.

[0061] 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.

[0062] 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 piezoelectric element 15 then typically corresponds to the voltage across the capacitor 24. A current i L , substantially sinusoidal, circulates in the piezoelectric element 15, in the resonant branch of its equivalent model.

[0063] The respective values ​​of the resistance R, the capacitance C of the capacitor 34, and the inductance L of the coil 36, as well as the reference capacitance Co define the dimensioning of the piezoelectric element 15.

[0064] Figure 2 schematically illustrates an electronic electrical energy conversion system 35, configured to provide electrical energy to a load 39 from a source 37.

[0065] 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.

[0066] The electrical energy converter 40 is configured to convert an input voltage Vj n into an output voltage V ou t. 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.

[0067] 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 continuous electrical energy or voltage into another continuous electrical energy or voltage, the potential Vj nn applied to the first input terminal 44 is lower than the potential Vj np applied to the second input terminal 46 and the potential V ou tn supplied on the first output terminal 48 is lower than the potential V 0U t P applied to the second output terminal 50.

[0068] To simplify the description, in the presence of an input voltage Vj n which changes sign, the Vj potentials nn and Vj np are then redefined at each instant so that Vj nn is less than Vj np . Similarly, if an output voltage is supplied that changes sign, Voutn and out Pare then redefined at each instant so that V ou tn is less than V 0U t P . Note that we consider a control cycle frequency at least 10 times higher than the primary voltage variation frequency, advantageously at least 100 times, so that during a control cycle, the input voltage Vj n and the output voltage V ou t can be considered substantially constant and without change of sign. The electrical energy converter 40 preferably being 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.

[0069] 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 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.

[0070] 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 source of electrical energy can be used, for example an AC or DC electrical network. In addition, to stabilize the input voltage, advantageously an electrical capacitor can be added in parallel with Vj n

[0071] 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 to the output, for example an electronic device, a motor, a resistive load, etc. In addition, to stabilize the output voltage, advantageously an electrical capacitor can be added in parallel with V ou t.

[0072] 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.

[0073] Note however that this rectifier is only of interest if the change in polarity of the input voltage Vj n induces a change of polarity on the primary arms (V X ah-V X ai). To only have to manage one voltage polarity (V xa hV xai), it may be advisable to place a rectifier bridge just upstream of these primary arms and not necessarily at the input of the converter. Alternatively, the use of bidirectional voltage switches 18a, 20a makes it possible to do without any voltage rectifier in the event of alternating sign on the voltage across the terminals of the primary arms (V xa hV xa i).. In this latter case (V xa hV xa i) can alternate in sign, but it is sufficient, in terms of representation, depending on the polarity of the voltage (V xa hV xa i), consider V X ah>V xa i. Thus, in the case of a negative voltage alternation, it is sufficient to consider for this alternation a converter with V xa h and V xai permuted, to re-describe the converter considering this permutation to find the operation considering V X ah>V xa i. In the following, to simplify the description, we will consider V xah always greater than V xa i, knowing that one can always, at any moment, define a V xa h and a V xai such that V X ah>V xa i. Similarly, in the following, we will consider Vj np always greater than Vj nn , knowing that we can always, at any time, define a Vj np and a Vj nn such as Vin P >Vi nn . 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 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.

[0074] Similarly for the secondary arms, it is possible to generate an alternating voltage with polarity change using bidirectional voltage switches 18b, 20b. To do this, simply redefine V X bh and V X hi at each instant according to the polarity at the secondary, to find a configuration such that V X bh>V X bi. In the following, to simplify the description, we will consider V X bh always greater than V X bi, knowing that we can always, at any moment, define a V X bh and a V X bi such that V X bh>V X bi. 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 secondary voltage can be considered substantially constant and without change of sign.

[0075] 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.

[0076] In addition, at least one of the primary switching branches is connected, via its first primary terminal or its second primary terminal, to the first input terminal or to the second input terminal, and at least one of the secondary switching branches is connected, via its first secondary terminal or its second secondary terminal, to the first output terminal or to the second output terminal.

[0077] Several examples of embodiments of electrical energy converters 40 are described below.

[0078] Figure 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.

[0079] Generally speaking, the number N is any number greater than or equal to 2.

[0080] The embodiment of Figure 3 is more particularly advantageous for producing a high voltage drop converter or high step-down converter.

[0081] In this embodiment, the primary switching branches 4ai, 4a2, 4aa of the elementary piezoelectric converters 2i, 22 and 2a are connected in series, while the secondary switching branches 4bi, 4b2, 4ba of the elementary piezoelectric converters 2i, 22 and 2a are connected in parallel.

[0082] The series connection is made by connecting the first primary terminal of the elementary piezoelectric converters 22 and 2a to the second primary terminal of another of said elementary piezoelectric converters 2i, 22.

[0083] 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 denoted 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 denoted 54; the second primary terminal of the elementary piezoelectric converter 22 is connected to the first primary terminal of the elementary piezoelectric converter 2a at a connection point denoted 56; the second primary terminal of the elementary piezoelectric converter 2a is connected to the second input terminal 46 at a connection point denoted 58.

[0084] Thus, in this example, the elementary piezoelectric converters 2i, 22 and 2a are connected in series via their primary switching branches 4ai, 4a2, 4aa between the first input terminal 44 and the second input terminal 46. In other words, the electrical energy converter 40 of FIG. 3 has a 3-level series stage at the input.

[0085] On the secondary side, in this embodiment, the first secondary terminals 6bi, 6b2 and 6ba of the elementary piezoelectric converters 2i, 22 and 2a are connected to the first output terminal 48 and the second secondary terminals 8bi, 8b2 and 8ba of the elementary piezoelectric converters 2i, 22 and 2a are connected to the second output terminal 50.

[0086] Furthermore, in this embodiment, capacitors 6O1, 6O2, 6O3, of respective capacities C1a, C2a, C3a are connected respectively in parallel with the primary switching branches 4ai, 4a2, 4a3 of the elementary piezoelectric converters 2i,

[0087] 22 and 23. According to the presented architecture, capacitor 6O1 is connected between connection points 52 and 54, capacitor 6O2 is connected between connection points 54 and 56 and capacitor 6O3 is connected between connection points 56 and 58.

[0088] Thus, the first elementary piezoelectric converter 2i receives as input a first voltage Vmi, the second elementary piezoelectric converter 22 receives as input a second voltage Vj n 2 and the third elementary piezoelectric converter

[0089] 23 receives as input a second voltage Vins, each of the first voltage Vj n i, Vj n 2 and Vj n3 being equal to a fraction of the input voltage Vin, their sum being equal to the input voltage Vj n .

[0090] Furthermore, in the embodiment of Figure 3, a capacitor 62 is connected in parallel with the secondary switching branches 4bi, 4b2, 4bs of the elementary piezoelectric converters 2i, 22 and 2s. 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 induced current ripples at the frequency of the driving cycle, to filter the voltage across the primary arms for capacitors 6O1, 6O2, 6O3, and across the secondary arms for capacitor 62. If a capacitor 60, 62 is directly in parallel with a low impedance voltage source or load, such as a low impedance battery, or in series between a low impedance source and load, then this capacitor can be omitted, the source and / or load providing this filtering. On the other hand, on the side of the series connection of arms, namely capacitors 6O1, 6O2, 6O3, in the example of Figure 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 64i, 642, 64s are connected in series with the piezoelectric resonator assemblies 22i, 222 and 22s of the elementary piezoelectric converters 2i, 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 22i, 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 Vj nn or Vj npconnected to the input voltage is not connected to one of the output terminals. Thanks to the presence of such an additional capacitor 64j, 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 2i, 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 Figures 8 to 10.

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

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

[0098] Figure 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 Figure 5 is "mirrored" with respect to the architecture of the electrical energy converter 40 illustrated in Figure 4.

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

[0101] Thus, in this example, the elementary piezoelectric converters 2i, 22 and 23 are connected in series via their secondary switching branches 4bi, 4b3, 4b3 between the first output terminal 48 and the second output terminal 50. In other words, the electrical energy converter 40 of FIG. 5 has 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 4a of the elementary piezoelectric converters 2i, 22 and 2a. On the secondary side, respective capacitors 62i, 622, 62a of capacitances C1b; C2b, C3b are connected in parallel with each of the secondary switching branches 4bi, 4b2, 4ba.

[0103] The embodiment of Figure 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 mirrored high-boost electrical energy converter architecture compared to the architecture described with reference to Figure 3.

[0105] Figure 6 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.

[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 2i, 22 and 2a, is connected to the second output terminal 50 and the second secondary terminal 8b of the elementary piezoelectric converters 2i, 22 and 2a is connected to the first output terminal 48.

[0107] In this embodiment, the electrical energy converter 40 obtained is also an inverter, the potential V outn is of opposite polarity to the potential Vj np taking Vinn as a 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 higher voltage side, 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 primary switching branch of each elementary piezoelectric converter is close to the voltage across the secondary switching branch. By close is meant within 50%, and advantageously within 25%.

[0110] 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.

[0111] Figure 7 illustrates another embodiment of an electrical energy converter 40 comprising N elementary piezoelectric converters, N being equal to 3.

[0112] In this embodiment, the 3 elementary piezoelectric converters 2i, 22 and 23 are connected in series via their respective primary switching branches 4ai, 4a2, 4a3, the secondary switching branches 4bi, 4b2, 4b3 being connected in parallel.

[0113] Unlike the embodiment illustrated in Figure 3, the primary switching branches 4ai, 4a2, 4a3 connected in series are connected between the second input terminal 46 of potential Vj np and the second output terminal 50 of potential Voutp.

[0114] 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'.

[0115] On the secondary side, in this embodiment, the first secondary terminals 6bi, 6b2 and 6b3 of the elementary piezoelectric converters 2i, 22 and 23 are connected to the first output terminal 48 and the second secondary terminals 8bi, 8b2 and 8b3 of the elementary piezoelectric converters 2i, 22 and 23 are connected to the second output terminal 50.

[0116] The electrical energy converter in Figure 7 is particularly suitable for producing a strongly step-down converter. It also has the advantage that the current flowing through the primary switching branches contributes to the supply of 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 makes it possible to reduce the size of the piezoelectric resonators (less current flowing through the piezoelectric resonators).

[0117] Of course, it is easy to envisage a mirrored electrical energy converter architecture compared to that of Figure 7, in which the secondary switching branches of the elementary piezoelectric converters 2i, 22 and 2a 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.

[0118] 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.

[0119] In one embodiment, the electronic control device 42 is configured to control each of the elementary piezoelectric converters of the electrical energy converter 40.

[0120] 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.

[0121] The electronic control device 42 is for example produced in the form of an electronic circuit comprising one or more electronic components.

[0122] 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.

[0123] In all embodiments, each of the elementary piezoelectric converters can receive substantially the same control sequence. Alternatively, the sequences are substantially identical but are interlaced, 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 has the effect of compensating certain disturbances by symmetry and reducing the electromagnetic disturbances of the converter.Furthermore, it is advantageous, even if they are out of phase, that the control sequences are substantially identical so that the primary or secondary arms placed in series share the voltage well, when the converters exchange substantially identical power.

[0124] 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 V ou t, of the current l ou t or the power V ou *desired output level via a control loop.

[0125] Alternatively, the electronic control device 42 comprises, for each elementary piezoelectric converter, a dedicated regulation circuit to, on the one hand, properly share the voltage on the switching branches placed in series on the primary side and / or the secondary side and, on the other hand, regulate the voltage V ou t, of the current l ou t or the power V ou *output.

[0126] Figures 8, 9 and 10 illustrate control sequences of an elementary piezoelectric converter 2 comprising a piezoelectric assembly 22 with piezoelectric element Px;

[0127] Figures 8 and 9 illustrate respective curves of total mechanical deformation of a piezoelectric assembly 22 and a curve of current l flowing in a piezoelectric assembly, as well as curves of evolution of the voltage V pXdyn and associated switch drive configurations to achieve step-down (Figure 8) and step-up (Figure 9) configurations in three-step drive with substantially constant voltage per drive cycle.

[0128] Figure 10 illustrates a four-step control at substantially constant voltage, on the one hand in step-down mode, on the other hand in step-up mode.

[0129] The voltage V pX dyn is equal to the voltage V px at the terminals of the piezoelectric assembly from which the common mode component V is subtracted pxm c defined by the expression:

[0130] Vpxmc- (V X ah+V X al) / 2-(V x bh'*'V x bl) / 2

[0131] 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.

[0132] The voltages V xa and V X b are obtained as a function of the voltages V xa h, V xai across its primary switching branch and V X bh, V X bi at the terminals of its secondary switching branch: V xa =(V X ah-V X ai) / 2 and V X b=(V X bh-V X bi) / 2. The voltage V xa represents the amplitude of the primary voltage relative to a central point V xa mc defined by the expression: V xam c=(V xa i+V xa h) / 2, and is also called the amplitude of the dynamic input voltage.

[0133] The voltage V X b represents the amplitude of the primary voltage relative to a central point V X b mc defined by the expression: V X bmc=(V X bi+V X bh) / 2, and is also called the amplitude of the dynamic output voltage.

[0134] 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 Vj n or V ou t, advantageously less than 5%).

[0135] 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 V xam c in primary and V X b mc in secondary. Note that the common mode V xam c or V X b mc as defined here is not necessarily the average value of V xar or V X br, there may remain a non-zero average component, in particular if, for example, for V xar, K1 and K2 are not closed over identical durations. This is therefore an equivalent of a change of reference where a continuous component has been removed and which is not necessarily the average value.

[0136] The voltage V px at the terminals of the piezoelectric assembly can take the following values: V px =V xam resume X bmc+ / -V xa + / -V X b

[0137] The dynamic component V pX d yn of this voltage, or dynamic voltage across the terminals of the piezoelectric assembly, simply called dynamic voltage V pX d yn subsequently, can take the following voltage step values: V pX d yn =V px -(V xam resume X bmc)= + / -V xa + / - V xb

[0138] There are 4 possible voltage step values:

[0139] • V px d y n — V xa+Vxb (K1 and K4 closed and K2 and K3 open)

[0140] • Vpxdyn- Vxa" Vxb (K1 and K3 closed and K2 and K4 open)

[0141] • Vpxdyn - Vxa +Vxb (K2 and K4 closed and K1 and K3 open)

[0142] • Vpxdyn - Vxa" V X b (K2 and K3 closed and K1 and K4 open)

[0143] 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 load and phases II, IV and VI at substantially constant voltage.

[0144] 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 supplied, 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.

[0145] Figure 8 shows two step-down configurations A1 and A3 without ZVS mode (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.

[0146] The steering is angular over a steering cycle of 0 to 2TT radians.

[0147] In the buck configurations A1 and A3, phase I extends from 0 to 01, phase II extends from 0i to 02, phase III from 02 to 03, phase IV from 03 to 04, phase V from 04 to 0s, phase VI from 0s to 06, where 03=TT and 06=2TT. In other words, 03 corresponds to a half-cycle of control.

[0148] By convention, for the first step-down configuration A1, the highest voltage step for the dynamic voltage V pX dyn is the one with the value V xa -V Xb. During this level, power is supplied to the piezoelectric assemblies 12A, 12B. By convention, the current II 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 V X aV X b.. Therefore, at constant load, the dynamic voltage V pX d yn tends to decrease when current II is positive, and consequently to increase when current II is negative.

[0149] Conversely, by convention, for the third step-down configuration A3, the highest voltage step for the dynamic voltage V pX d yn is the one with the value V xa +V Xb. During this level, power is delivered, or drawn, from the piezoelectric assembly 22. By convention, the current II flowing in the piezoelectric elements 15 is oriented so as to be positive during this voltage level at the value V c . Therefore, at constant load, the dynamic voltage V pX d yn tends to increase when current II is positive, and consequently to decrease when current II is negative.

[0150] As can be seen, the evolution of the voltage V pX d yn in the step-down configuration A3 is symmetrical, by inversion of signs (or inversion of polarity), to the evolution of the voltage V pX d yn in the step-down configuration A1. In Figure 8, the second step-down configuration A2 differs from the first step-down configuration A1, described previously, only in that it incorporates an excursion to the voltage Vzvs equal to +V X has+ V X b.

[0151] This voltage excursion allows you to move from the dynamic voltage level equal to - Vxa+Vxb to the voltage level equal to V xa -V X b in ZVS switching at the switches.

[0152] This transition is done in two stages, a first stage from angle 02 to angle 03 to move from the dynamic voltage V pX dyn equal to -V X a+V X b at dynamic voltage V pX dyn equal to Vxa+Vxb, then a second step from angle 03 to angle 03b to go from the dynamic voltage V pX dyn equal to V X a+V X b at dynamic voltage V pX dyn equal to V xa -V X b.

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

[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 realize cycles I to VI in the buck 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 Figure 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 area, consequently they can consist of only a simple diode.

[0157] Figure 9 shows 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 closure of the switches when the voltage across their terminals is low, preferably zero, to achieve zero voltage switching.

[0158] The steering is angular over a steering cycle of 0 to 2TT radians.

[0159] In the E1 and E3 elevator configurations, phase I extends from 0 to 01, phase II extends from 01 to 02, phase III from 02 to 03, phase IV from 03 to 04, phase V from 04 to 0s, phase VI from 0s to 06, where 03=TT and 06=2TT. In other words, 03 corresponds to a half-cycle of piloting.

[0160] During the first phase I, the sign of current II leads to an increase in the dynamic voltage V pX dyn. The dynamic voltage V pX dyn therefore goes from the value V xa -V Xb to the value -Vxa+Vxb. After the voltage step of phase II, the dynamic component of the dynamic voltage V pX dyn passes during phase III to V X has + V X b, then goes down to V xa -V X b during phase V.

[0161] Conversely, by convention, for the third booster configuration E3, the highest voltage step for the dynamic voltage V pX dyn is the one with the value V xa -V X b. During this level, power is delivered, or drawn, from the piezoelectric assembly 22. By convention, the current II flowing in the piezoelectric elements 15 is oriented so as to be positive during this voltage level at the value V c . Therefore, at constant load, the dynamic voltage V pX dyn tends to increase when current II is positive, and consequently to decrease when current II is negative.

[0162] As can be seen, the evolution of the dynamic voltage V pX dyn in the E3 booster configuration is symmetrical, by inversion of signs, to the evolution of the voltage V pX dyn in the E1 elevator configuration.

[0163] In Figure 9, the second booster configuration E2 differs from the first booster configuration E1 described previously, only in that it incorporates an excursion to the voltage Vzvs equal to -V xa -V X b. the transition from phase VI to phase I.

[0164] This voltage excursion allows us to move from the level equal to V xa - X b at the level equal to -V xa +V X b in ZVS switching at the switches. This transition is done in two stages, a first stage between the angle 05b and 06 (2TT, and therefore 0) to pass from the dynamic voltage pX dyn equal to V xa -V X b to dynamic tension pX dyn equal to -V xa-V X b, then a second step between 0o and 0i to move from dynamic tension pX dyn equal to -V xa -V X b to dynamic tension pX dyn equal to -V xa +V X b.

[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 realize 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 Figure 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. 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.

[0169] Figure 10 illustrates a four-step control at substantially constant voltage, on the one hand in step-down mode, on the other hand in step-up mode.

[0170] In Figure 10 are represented: the current curve II circulating in the resonant branch of the equivalent electrical model of a piezoelectric assembly is illustrated over a resonance cycle ranging from 0 to 2TT; 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 Figure 10, to a resonance cycle of the piezoelectric assembly.

[0171] In step-down mode, V xa is greater than V X b. The evolution of the dynamic component of the piezoelectric voltage (or dynamic voltage) V pX dy n on a control cycle between 0 and 2TT is illustrated in graph A*.

[0172] In this buck configuration, the control cycle, equal to the operating period in this example, has two half-cycles.

[0173] 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 0j.

[0174] In detail, between 0o and 01, during phase I at substantially constant load, the dynamic component of the piezoelectric voltage V pX dy n -V pass xa -V X b (K2 and K3 closed and K1 and K4 open) to -V xa +V X b (K2 and K4 closed and K1 and K3 open).

[0175] During phase II at substantially constant voltage, between 01 and 02, dynamic component of the piezoelectric voltage V pX d yn is approximately equal to -V xa +V X b.

[0176] During phase III at substantially constant load, between 02 and 02b, the value of the dynamic component of the piezoelectric voltage V pX d yn evolves between -V xa +VX b and V xa +V X b (K1 and K4 closed, K2 and K3 open).

[0177] Finally, during phase IV at substantially constant voltage, between angles 02b and 03=TT, the dynamic component of the piezoelectric voltage V pX d yn is substantially equal to V xa +V x b.

[0178] The second half-cycle also includes two phases V, VII at substantially constant load and two phases VI, VIII at substantially constant voltage.

[0179] In detail, between 03 and 03b, during phase V at substantially constant load, the dynamic component of the piezoelectric voltage V pX d yn V pass xa +V X b to V xa -V X b (K1 and K3 closed, K2 and K4 open). During phase VI at substantially constant voltage, between 03b and 04, the dynamic component of the piezoelectric voltage V pX dyn is approximately equal to V xa -VX b.

[0180] During phase VII at substantially constant load, between 04 and 0s, the dynamic component of the piezoelectric voltage V pX d yn evolves between V xa -V X b and -V xa -V X b.

[0181] Finally, during phase VIII at substantially constant voltage, between angles 0s and 06=2TT, the dynamic component of the piezoelectric voltage V pX d yn is substantially equal to V xa -V xb .

[0182] The respective substantially constant voltage phases II, VI are of substantially the same duration, in other words 02— 01 « 04 — 03b, and the respective voltage values ​​are substantially equal and of opposite signs.

[0183] Similarly, the respective substantially constant voltage phases IV, VIII are of substantially the same duration, in other words 03- 0 2b~ 06- 05, and the respective voltage values ​​are substantially equal and of opposite signs.

[0184] The evolution of dynamic voltage V pX d yn (or dynamic component of the piezoelectric voltage) over time in a voltage-boosting configuration, in which V xa <V X b, is illustrated in graph E*.

[0185] In this elevator type configuration, the drive cycle, equal to the resonance / operating period in this example, has two half-cycles.

[0186] The first half-cycle comprises two phases I', III' at substantially constant voltage and two phases II', IV' at substantially constant load.

[0187] In detail, between 0o and 0ob, during phase I' at substantially constant voltage, the dynamic voltage V pX d yn is approximately equal to -V xa -V X b.

[0188] During phase II' at substantially constant load, between 0ob and 01, the dynamic voltage V pX d yn evolves between -V xa -V X b and -V xa +V X b.

[0189] During phase III' at substantially constant voltage, between 01 and 02, the dynamic voltage value V pX d yn is approximately equal to -V xa +V X b.

[0190] Finally, during phase IV' at substantially constant load, between angles 02 and 03=TT, the dynamic voltage V pX d yn evolves between -V xa +V X b and V xa +V X b.

[0191] The second half-cycle also includes two phases V', VII' at substantially constant voltage and two phases VI', VIII' at substantially constant load.

[0192] In detail, between 03 and 04, during phase V' at substantially constant voltage, the dynamic voltage V pX d ynis substantially equal to V xa +V X b.

[0193] During phase VI' at substantially constant load, between 04 and 0s, the dynamic voltage V pX d yn evolves between V xa +V X b and V xa -V X b.

[0194] During phase VII' at substantially constant voltage, between 0s and 05b, the dynamic voltage value V pX d yn is substantially equal to V xa -V X b. Finally, during phase VIII' at substantially constant load, between angles 05b and 06=2TT, the dynamic tension pX dyn evolves between xa - X b and -V xa -V X b.

[0195] Furthermore, the respective substantially constant voltage phases I', V' are of substantially the same duration, in other words 020i ~ 04 9 3b , and the respective voltage values ​​are substantially equal and of opposite signs (respectively - V xa -Vx b and V xa +V x b.) .

[0196] Similarly, the respective substantially constant voltage phases III', VII' are of substantially the same duration, in other words 02 0i ~ 05b 05 and the respective voltage values ​​are substantially equal and of opposite signs (respectively V xa +V x b and V xa -V x b.).

[0197] 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 of the dynamic voltage V pX d yn 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.

[0198] 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.

[0199] 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 V xa -V X b or the opposite of the difference V X b- V xa between the amplitude of the dynamic input voltage V xa and the amplitude of the dynamic output voltage V X b, and the other voltage value among the first voltage value and the second voltage value is equal to the sum V xa +V X b or the opposite of the sum - V xa -V x b of the amplitude of the dynamic input voltage V xaand the amplitude of the dynamic output voltage V X b.

[0200] The electronic control device 42 is configured to control the respective switches at the primary and secondary to achieve the 4-step voltage 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.

[0201] During constant load phases, only a change of polarity is necessary, either in the primary, passage from +V xa to -V xa or -V xa to +V xa , either in secondary, passage from +V X b to -V X b or -V X b to +V X b. Thus, only V xar or V X br changes potential, while the other potential among V xar , V Xbr remains unchanged via a switch that remains on or closed. Consequently, the output of a phase at substantially constant voltage is achieved by opening or blocking a single switch and the output of a phase at constant load is achieved by closing or turning on a single switch. Furthermore, it is not necessary to change the switch configuration over the entire duration between 2 constant voltage steps, unlike in the case of a 3-step cycle at constant voltage as described in Figure 8, for example between 02 and 03b.

[0202] 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.

[0203] 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.

[0204] 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.

[0205] 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 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 (œ p=1A / (LCCo / (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 that 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 control loop. It is also possible to change the resonance mode on the resonator, for example, from a thickness resonance mode to a radial or surface elongation resonance mode, or even to switch to a higher resonance mode to address different power ranges with improved efficiency.

[0206] An example of the architecture of an electrical energy converter 80 comprising elementary converters with switching bridge is illustrated in Figure 11. In the example of an electrical energy converter of Figure 11, 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 Vj n into two input voltages substantially equal to Vj n / 2. 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 part 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 ( j n ) in at least one output voltage (V ou t), the converter (40, 80) comprising a first input terminal and a second input terminal, the input voltage ( j n ) 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 (V out) being provided between the first output terminal and the second output terminal, comprising at least one elementary piezoelectric converter (2, 2i, 22, 2a), each elementary piezoelectric converter (2, 2i, 22, 2a) comprising: a primary switching branch (4a, 4ai, 4a2, 4aa) and a secondary switching branch (4b, 4bi, 4b2, 4ba), the primary switching branch (4a) comprising two primary arms 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), at least one piezoelectric element (15) connected between the primary midpoint (10a) and the secondary midpoint (10b), characterized in that it comprises at least two elementary piezoelectric converters (2, 2i, 22, 2a) connected in series via their primary switching branches (4a, 4ai, 4a2, 4aa) and / or via their secondary switching branches (4b, 4bi, 4b2, 4ba), 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),at least one of the primary switching branches being connected to the first input terminal (44) or to the second input terminal (46) and at least one of the secondary switching branches being connected to the first output terminal (48) or to the second output terminal (50)., 2. Converter according to claim 1, wherein said at least two elementary piezoelectric converters (2i, 22, 2a) are 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 (2i, 22, 23) connected in series via their primary switching branches (4ai, 4a2, 4a3) share the same secondary switching branch (4b).

4. Converter according to claim 1, wherein said at least two elementary piezoelectric converters (2i, 22, 23) are connected in parallel via their primary switching branches and connected in series via their secondary switching branches (4bi, 4b2, 4ba).

5. Converter according to claim 4, wherein said at least two elementary piezoelectric converters (2i, 22, 2a) 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, wherein at least one elementary piezoelectric converter of said at least two elementary piezoelectric converters is said to be 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.

7. Converter according to any one of claims 1 to 6, wherein at least one elementary piezoelectric converter of said at least two elementary piezoelectric converters is said to be an 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 primary terminal 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, in which each of said elementary piezoelectric converters comprises a capacitor (6O1, 6O2, 6O3) 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, in which 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 conforms to any one of claims 1 to 11.

13. The system of claim 12, wherein 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 phases 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.

14. The system of 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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