Electronic device and common-mode control method for an electrical energy converter comprising two piezoelectric elements, associated electrical energy conversion electronic system

Abstract

Electronic device and method for common-mode control of an electrical energy converter comprising two piezoelectric elements, associated electronic electrical energy conversion system. The invention relates to an electronic device for controlling a converter of an input voltage into at least one output voltage, comprising a first bridge having two first switching branches, each between two terminals of the input voltage and having two first switches connected at a first midpoint; at least a second bridge having two second switching branches, each between two terminals of the output voltage and having two second switches connected at a second midpoint; at least one pair of first and second piezoelectric assemblies, each connected between respective first and second midpoints, distinct from one piezoelectric assembly to the other.The control device is configured to control, during a respective resonance cycle of the piezoelectric assemblies, the switching of each of the switches to alternate between phases with substantially constant voltage across the piezoelectric assemblies and phases with substantially constant load across said piezoelectric assemblies. It is further configured to, during each phase with substantially constant load, simultaneously close at most one switch from among those directly connected to the first piezoelectric assembly and at most one switch from among those directly connected to the second piezoelectric assembly, and open all the other switches in the first and second branches.

Description

Title of the invention: Electronic device and method for controlling without common mode an electrical energy converter comprising two piezoelectric elements, associated electronic electrical energy conversion system

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

[0002] The converter comprises a first switching bridge comprising two first switching branches, each first switching branch being connected between two terminals for applying the input voltage and comprising at least two first switches connected in series and connected to each other at a first midpoint; at least one second switching bridge comprising two second switching branches, each second switching branch being connected between two terminals for supplying the output voltage and comprising at least two second switches connected in series and connected to each other at a second midpoint;and at least one pair of first and second piezoelectric assemblies, each piezoelectric assembly comprising at least one piezoelectric element and being connected between respective first and second midpoints, the midpoints between which the piezoelectric assemblies are connected being distinct from one piezoelectric assembly to the other. ;

[0003] The electronic control device is configured to control, during a respective resonance cycle of the piezoelectric assemblies, a switching of each of the switches to alternate phases at substantially constant voltage at the terminals of the piezoelectric assemblies and phases at substantially constant charge at the terminals of said piezoelectric assemblies.

[0004] The invention also relates to an electronic electrical energy conversion system comprising such an electrical energy converter and an electronic device for controlling said converter.

[0005] The invention also relates to a method for controlling such an electrical energy converter, the method being implemented by such an electronic control device.

[0006] The invention relates to the field of electronic systems for converting electrical energy, in particular those comprising a piezoelectric element, in particular systems for converting into direct electrical energy, i.e. direct-direct conversion systems, also called DC-DC conversion systems (from the English Direct Current - Direct Current)^ and alternating-current conversion systems. continuous, also called AC-DC conversion systems (from the English Alternating Current - Direct Current).

[0007] Documents FR 3 086 471 Al and FR 3 086 472 Al, as well as the thesis manuscript “Piezoelectric DC-DC converters with temporary energy storage in mechanical form” by Benjamin POLLET, disclose an electrical energy converter of the aforementioned type, visible in figure 20 of documents FR 3 086 471 Al and FR 3 086 472 Al, and in [Fig.4]. 15 of the aforementioned thesis manuscript.

[0008] As indicated in document FR 3 086 471 A1 or in the thesis manuscript, an advantage of using two piezoelectric elements is that the output voltage is thus isolated from the input voltage, without it being necessary to use a transformer.

[0009] The isolation is capacitive and is therefore not achieved with a transformer which is a source of losses, but by the fact that the impedance of the piezoelectric resonator is very high at low frequency and blocks any propagation of the low-frequency voltage from the input to the output, and vice versa. In addition, the input common-mode component equal to half the sum of the potentials at the terminals of application of the input voltage does not affect the output common-mode component equal to half the sum of the potentials at the terminals of supply of the output voltage and vice versa. The input and output common-mode potentials or components can thus evolve freely, at low frequency, relative to each other.In fact, each piezoelectric element is modeled in the form of a capacitor and a resonant branch connected in parallel to the capacitor, the capacitance of said capacitor being called parallel capacitance, or reference capacitance, and noted Co. A low frequency signal of type 50 / 60 Hz will then be filtered by the high impedance (for example 3.1 MQ for Co = 1 nF at 50 Hz) of each of the blocked capacitances of the two piezoelectric resonators thus creating an isolation between the input and output parts of the converter.

[0010] This advantage is present even compared to a piezoelectric transformer, in which all the energy supplied to the primary is not completely transmitted to the secondary and the primary must also set in motion a larger mass, namely that of the primary plus that of the secondary, which generates losses.

[0011] However, the operation of such a converter is not optimal around the resonant frequency of the piezoelectric elements.

[0012] The aim of the invention is then to propose an electronic device, and an associated method, for controlling such an electrical energy converter offering improved control of the converter, in particular better insulation.

[0013] To this end, the invention relates to an electronic device for controlling an electrical energy converter capable of converting an input voltage into at least an output voltage, the converter comprising a first switching bridge comprising two first switching branches, each first switching branch being connected between two terminals for applying the input voltage and comprising at least two first switches connected in series and connected to each other at a first midpoint; at least one second switching bridge comprising two second switching branches, each second switching branch being connected between two terminals for supplying the output voltage and comprising at least two second switches connected in series and connected to each other at a second midpoint;at least one pair of first and second piezoelectric assemblies, each piezoelectric assembly comprising at least one piezoelectric element and being connected between respective first and second midpoints, the midpoints between which the piezoelectric assemblies are connected being distinct from one piezoelectric assembly to the other; ;

[0014] the electronic control device is configured to control, during a respective resonance cycle of the piezoelectric assemblies, a switching of each of the switches to alternate phases at substantially constant voltage at the terminals of the piezoelectric assemblies and phases at substantially constant charge at the terminals of said piezoelectric assemblies,

[0015] the electronic control device being further configured to, during each phase at substantially constant load, control in the closed position at the same time at most one respective switch among the switches connected directly to the first piezoelectric assembly and at most one respective switch among the switches connected directly to the second piezoelectric assembly, and in the open position all the other switches of the first and second switching branches.

[0016] With the converter and the associated control device of the state of the art, if the continuous or low frequency component, typically less than 1 kHz, is naturally filtered by the capacitive behavior of the low frequency piezoelectrics as described previously, the components around the resonance frequency of the piezoelectric naturally pass from the input to the output and vice versa.

[0017] With the control device according to the invention, the conversion cycle is adapted so that the latter allows power to be transferred from the input to the output, but without injecting a common mode component.

[0018] During the phases with substantially constant voltage across the terminals of the piezoelectric assemblies, the voltage across the terminals of the piezoelectric assemblies does not vary and cannot induce a high-frequency common-mode voltage.

[0019] During the phases with substantially constant charge at the terminals of said piezoelectric assemblies, the closed position of at most one respective switch among the inter breakers connected directly to the first piezoelectric assembly and at most one respective switch among the switches connected directly to the second piezoelectric assembly at the same time, all the other switches of the first and second switching branches being in the open position, makes it possible to avoid the connection of one or the other of the piezoelectric assemblies between a potential of the input voltage and a potential of the output voltage, and then to avoid the introduction of a high-frequency common-mode component between the input voltage and the output voltage.

[0020] According to other advantageous aspects of the invention, the electronic control device comprises one or more of the following characteristics, taken in isolation or in all technically possible combinations:

[0021] - the value of the voltage of each of the phases at substantially constant voltage is distinct from the null value;

[0022] - the value of the voltage of each of the phases at substantially constant voltage is selected from the group consisting of: difference between the value of the input voltage and that of the output voltage; difference between the value of the output voltage and that of the input voltage; sum of the values ​​of the input and output voltages; and opposite of the sum of the values ​​of the input and output voltages.

[0023] - the number of phases at substantially constant voltage during a respective cycle of resonance is greater than or equal to 3;

[0024] the number of phases at substantially constant voltage during a respective resonance cycle being preferably equal to 3.

[0025] The invention also relates to an electronic electrical energy conversion system comprising:

[0026] - an electrical energy converter capable of converting an input voltage into at minus one output voltage, and comprising:

[0027] + a first switching bridge comprising two first branches of communication mutation, each first switching branch being connected between two terminals for applying the input voltage and comprising at least two first switches connected in series and linked together at a first midpoint;

[0028] + at least one second switching bridge comprising two second branches switching, each second switching branch being connected between two output voltage supply terminals and comprising at least two second switches connected in series and linked together at a second midpoint;

[0029] + at least one pair of first and second piezoelectric assemblies, each piezoelectric assembly comprising at least one piezoelectric element and being connected between respective first and second midpoints, the midpoints between which the piezoelectric assemblies are connected being distinct from a piezoelectric assembly to the other; and

[0030] - an electronic device for controlling the electrical energy converter, the control device being as defined above.

[0031] According to other advantageous aspects of the invention, the electronic electrical energy conversion system comprises one or more of the following characteristics, taken individually or in all technically possible combinations:

[0032] - the electronic electrical energy conversion system is a system of conversion into direct electrical energy, such as a direct-to-direct conversion system or an alternating-to-direct conversion system;

[0033] - the electrical energy converter is capable of converting the input voltage into several distinct output voltages, and includes

[0034] for each respective output voltage:

[0035] + a second respective switching bridge, each second branch of com mutation being connected between two terminals supplying the respective output voltage;

[0036] + a respective pair of first and second piezoelectric assemblies;

[0037] - each piezoelectric assembly is made up according to one of the constitutions among the group consisting of: a single piezoelectric element; a plurality of piezoelectric elements connected in series; a plurality of piezoelectric elements connected in parallel; a piezoelectric element and an auxiliary capacitor connected in series; a piezoelectric element and an auxiliary capacitor connected in parallel; and an arrangement of a plurality of parallel piezoelectric branches, each branch comprising one or more piezoelectric elements connected in series or an auxiliary capacitor;

[0038] the auxiliary capacitor preferably having a higher capacity, more preferably at least three times higher, than a reference capacity of the piezoelectric element(s), each piezoelectric element being modeled in the form of a capacitor and a resonant branch connected in parallel to the capacitor, the reference capacity being the capacity of said capacitor;

[0039] - the converter further comprises at least one switching assistance circuit, each switching assistance circuit being connected to a respective midpoint among the first and second midpoints, each switching assistance circuit being configured to, via the flow of a previously received current, discharge a parasitic capacitance of a switch of the respective switching bridge to which it is connected, and respectively charge a parasitic capacitance of another switch of said switching bridge;

[0040] - the converter comprises two switching assistance circuits, a first circuit switching aid circuit being connected to the first switching bridge and a second switching aid circuit being connected to the second switching bridge;

[0041] - each switching aid circuit comprises an element chosen from the group consisting of: an electromagnetic coil; a first assembly formed of an electromagnetic coil and a diode connected in series; a second assembly formed of an electromagnetic coil and a capacitor connected in series; and an additional piezoelectric element;

[0042] each switching assistance circuit preferably being made up of an element chosen from said group.

[0043] The invention also relates to a method for controlling an electrical energy converter capable of converting an input voltage into at least one output voltage, the converter comprising a first switching bridge comprising two first switching branches, each first switching branch being connected between two terminals for applying the input voltage and comprising at least two first switches connected in series and connected together at a first midpoint; at least one second switching bridge comprising two second switching branches, each second switching branch being connected between two terminals for supplying the output voltage and comprising at least two second switches connected in series and connected together at a second midpoint;at least one pair of first and second piezoelectric assemblies, each piezoelectric assembly comprising at least one piezoelectric element and being connected between respective first and second midpoints, the midpoints between which the piezoelectric assemblies are connected being distinct from one piezoelectric assembly to the other; ;

[0044] the method being implemented by an electronic control device and comprising the control, during a respective resonance cycle of the piezoelectric assemblies, of a switching of each of the switches to alternate phases at substantially constant voltage at the terminals of the piezoelectric assemblies and phases at substantially constant charge at the terminals of said piezoelectric assemblies, and

[0045] during each phase at substantially constant load, at most one respective switch among the switches connected directly to the first piezoelectric assembly and at most one respective switch among the switches connected directly to the second piezoelectric assembly are controlled in the closed position at the same time, and all the other switches of the first and second switching branches are controlled in the open position.

[0046] These characteristics and advantages of the invention will appear more clearly in the reading of the description which follows, given solely as a non-limiting example, and made with reference to the attached drawings, in which:

[0047] [Fig.l] [Fig.l] is a schematic representation of an electronic electrical energy conversion system according to the invention, comprising an electrical energy converter and an electronic device for controlling said converter, the converter comprising a first switching bridge with two first switching branches each formed by two first switches connected in series and connected at a first midpoint, a second switching bridge with two second switching branches each formed by two second switches connected in series and connected at a second midpoint, a pair of first and second piezoelectric assemblies, each piezoelectric assembly comprising a piezoelectric element and being connected between respective first and second midpoints, the midpoints between which the piezoelectric assemblies are connected being distinct from one piezoelectric assembly to the other;the first, and respectively second, bridges being connected between two terminals for applying an input voltage, and respectively between two terminals for supplying an output voltage; ;

[0048] [Fig.2] [Fig.2] is a set of curves representing a current flowing in the piezoelectric assemblies normalized to an amplitude of 1, a total mechanical deformation of the piezoelectric assemblies normalized to an amplitude of 1, a voltage between ends of said pair of piezoelectric assemblies, a voltage between the other ends of said pair of piezoelectric assemblies, as well as a total voltage of the piezoelectric assemblies corresponding to the sum of said elementary voltages at the terminals of each piezoelectric assembly, and this for different configurations of electrical energy conversions, namely for four voltage-stepping configurations;

[0049] [Fig.3] [Fig.3] is a view similar to that of [Fig.2], for other electrical energy conversion configurations, namely for four voltage booster configurations;

[0050] [Fig.4] [Fig.4] is a view similar to that of [Fig.l], according to another example of the electrical energy converter, where the electrical energy converter is capable of converting the input voltage into several distinct output voltages, and comprises - for each respective output voltage - a second respective switching bridge, each second switching branch being connected between two terminals for supplying said respective output voltage, and a respective pair of first and second piezoelectric assemblies;

[0051] [Fig.5] [Fig.5] is a view similar to that of [Fig.l], according to a complementary aspect where the converter further comprises a switching assistance circuit connected between the first and second midpoints of the second bridge;

[0052] [Fig.6] [Fig.6] is a schematic representation of different types of switching aid circuit;

[0053] [Fig.7] [Fig.7] is a view similar to that of [Fig.2], according to the complementary aspect of [Fig.5], the set of curves also representing the sum of the elementary voltages at the terminals of each piezoelectric assembly, and this for two voltage-lowering configurations;

[0054] [Fig.8] [Fig.8] is a view similar to that of [Fig.5], according to an alternative embodiment of the complementary aspect, where the switching assistance circuit is connected between the first and second midpoints of the first bridge; and

[0055] [Fig.9] [Fig.9] is a view similar to that of [Fig.7], for other electrical energy conversion configurations, namely for two voltage booster configurations, typically according to the embodiment variant of the complementary aspect.

[0056] The expression “substantially equal to” defines a relationship of equality to plus or minus 10%, preferably to plus or minus 5%.

[0057] In [Fig.l], an electronic electrical energy conversion system 5 comprises an electrical energy converter 10 comprising a pair of first 12A and second 12B piezoelectric assemblies, each piezoelectric assembly 12A, 12B comprising at least one piezoelectric element 15, the converter 10 comprising several switches Kb K2, K3, K4, K5, K6, K7, K8 capable of being controlled to alternate phases II, IV, VI at substantially constant voltage across the piezoelectric assemblies 12A, 12B and phases I, III, V at substantially constant charge across the piezoelectric assemblies 12A, 12B.

[0058] The electronic electrical energy conversion system 5 also comprises an electronic device 20 for controlling the electrical energy converter 10.

[0059] The electronic electrical energy conversion system 5 is typically a system for converting into direct electrical energy, such as a direct-direct conversion system capable of converting a first direct electrical energy or voltage received at the input into a second direct electrical energy or voltage delivered at the output, or even an alternating-direct conversion system capable of converting an alternating electrical energy or voltage received at the input into a direct electrical energy or voltage delivered at the output of the conversion system 5.

[0060] When the electrical energy conversion system 5 is an AC-DC conversion system, the electrical energy conversion system 5 preferably further comprises a voltage rectifier, not shown, connected to the input of the electrical energy converter 10 and capable of rectifying the AC electrical voltage received at the input of the conversion system 5 to deliver a voltage rectified electrical energy at the input of the converter 10, the electrical energy converter 10 preferably being a DC-DC converter capable of converting a DC electrical energy or voltage into another DC electrical energy or voltage. The voltage rectifier is for example a rectifier bridge, such as a diode bridge. Alternatively, the voltage rectifier is formed in part by switches of the converter 10.

[0061] Those skilled in the art will observe that these different examples for the conversion system 5, whether it is a DC-DC conversion system or an AC-DC conversion system, are also presented in the documents FR 3 086 471 A1 and FR 3 086 472 A1, in particular with regard to their figures 1 and 2.

[0062] The electrical energy converter 10 is preferably a DC-DC converter, and is also called a DC-DC converter. The DC-DC converter generally has the role of regulating a supply voltage of a load 22 to a stable value, by being powered by an energy source 24 providing a substantially DC voltage. The energy source 24 is for example a battery or a solar panel.

[0063] The electrical energy converter 10 is then configured to raise the value of the DC voltage between its input and its output, and is then also called a DC-DC step-up converter; or is configured to lower the value of the DC voltage between its input and its output, and is then called a DC-DC step-down converter.

[0064] The electrical energy converter 10 is configured to deliver N distinct output voltage(s), from E distinct input voltage(s), E and N each being an integer greater than or equal to 1.

[0065] In the example of [Fig.l], the electrical energy converter 10 is configured to deliver an output voltage, denoted Vout, from an input voltage, denoted Vin, the number E of input voltage(s) and the number N of output voltage(s) then each being equal to 1.

[0066] In the example of [Fig.4], the electrical energy converter 10 is configured to deliver several distinct output voltages, denoted Voutj where j is an integer index between 1 and N, from the input voltage Vin, the number N of distinct output voltages then being greater than 1. According to this example, the converter 10 is typically connected to several loads 22, as shown in [Fig.4].

[0067] The electrical energy converter 10 comprises the piezoelectric assemblies 12A, 12B each formed from one or more piezoelectric elements 15, and the control device 20 is configured to operate the piezoelectric material of the piezoelectric elements 15 at their resonance in order to exploit charge transfer phases making it possible to dispense with the use of an element inductive, while regulating the output voltage by maintaining the resonance of the piezoelectric material, i.e. with repeated switching cycles at an operating frequency dependent on the resonance frequency of the piezoelectric elements 15, and by adjusting the respective switching phase durations within the resonance cycle.

[0068] In steady state, the piezoelectric assemblies 12A, 12B exchange a charge and a power that is substantially zero over a resonance cycle, apart from losses. In other words, each piezoelectric assembly 12A, 12B gives back, substantially as much as it receives, energy and charge over a period. Two operating conditions then apply to the permanent / steady state, namely charge balance and energy balance over a resonance period. Even if during transients (start-up, variation of voltage steps, change of output current) this balance is not respected, it must nevertheless be possible to achieve it in steady state. This requires in particular a certain arrangement of the voltage steps during the resonance period.For example, for three-voltage-step operation, the two extreme voltage steps are controlled during one half-period of a given polarity of a current IL flowing in the piezoelectric elements 15, and the intermediate voltage step is controlled during the other half-period of opposite polarity of the current IL flowing in the piezoelectric elements 15.

[0069] As known per se, the mechanical oscillation of the piezoelectric elements 15 is approximately sinusoidal, as shown in Figures 2, 3, 7 and 9 by the curve 26 illustrating the total mechanical deformation of the piezoelectric elements 15 during a respective resonance cycle. The total mechanical deformation of the piezoelectric elements 15 is the sum of elementary mechanical deformations of each of the piezoelectric elements 15.

[0070] An increase or a decrease in the energy stored over a period leads respectively to an increase or a decrease in the oscillation amplitude. Furthermore, during a phase with a substantially constant charge at the terminals of the piezoelectric assemblies 12A, 12B, that is to say when the piezoelectric elements 15 are placed in a substantially open electrical circuit, with a low exchange of electrical charges between the piezoelectric elements 15 and the outside, an increase in the amplitude of the oscillations causes an increase in the speed of variation of the voltage Vp at the terminals of the piezoelectric assemblies 12A, 12B, and during a phase II, IV, VI with a substantially constant voltage at the terminals of the piezoelectric assemblies 12A, 12B, this increase in oscillation amplitude leads to an increase in a current Ip exchanged between the piezoelectric elements 15 and the voltage levels.

[0071] By substantially constant charge is meant an exchange of a charge with the exterior which is less than 10% of the charge which would have been exchanged with the exterior if the voltage had been kept constant. In other words, by substantially constant charge, we mean a charge variation less than 10% of the charge which would have been exchanged with the exterior of the piezoelectric assemblies 12A, 12B if the voltage across the terminals of the piezoelectric assemblies 12A, 12B had been kept constant over the time period considered.

[0072] By substantially open electrical circuit is meant a circuit in which a possible leakage current leads to a variation in charge of the piezoelectric assemblies 12A, 12B less than 10% of the charge which would have been exchanged with the exterior of the piezoelectric assemblies 12A, 12B if the voltage across the terminals of the piezoelectric assemblies 12A, 12B had been kept constant over the time period considered.

[0073] 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 II, IV, VI 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.

[0074] The converter 10 then comprises several switches Kb K2, K3, K4, K5, K6, K7, K8 visible in figures 1, 5 and 8, Ki4, K2>b K3>i, K41, Ki>2, K2>2, K3>2, K4j2, K5, K6, K7, K8 visible in [Fig.4], capable of being controlled to alternate phases II, IV, VI at substantially constant voltage and phases I, III, V at substantially constant charge at the terminals of the piezoelectric assemblies 12A, 12B, within periods of substantially constant duration corresponding to the operating frequency of the converter 10, depending on the resonance frequency, also called natural frequency, of the piezoelectric elements 15.Phases I, III, V at substantially constant load allow, in steady or permanent mode, to pass from one constant voltage to another and to close the switches which must be closed when the voltage at their terminals is preferably zero in order to have a so-called zero voltage switching, also called ZVS mode switching (from the English Zero Voltage Switching).

[0075] In particular, the converter 10 comprises a first switching bridge 30 comprising two first switching branches 32, each first switching branch 32 being connected between two terminals 34 for applying the input voltage Vin and comprising at least two first switches 36 connected in series and connected together at a first midpoint 38. Among the two application terminals 34, one has a lower potential, denoted Vinn, than the other, denoted Vinp. The first bridge switching branch 30 preferably consists of the first two switching branches 32.

[0076] In the examples of figures 1, 4, 5 and 8, each first switching branch 32 comprises two first switches 36 connected in series and connected at the first midpoint 38. Each first switching branch 32 is preferably made up of the two first switches 36.

[0077] In these examples, the first two switches 36 are denoted K5, K6 for one of the first two switching branches 32, and respectively K7, K8 for the other of the first two switching branches 32.

[0078] For the sake of distinction between the first switches 36 connected directly to the first piezoelectric assembly 12A and those connected directly to the second piezoelectric assembly 12B, the first switches 36 connected directly to the first piezoelectric assembly 12A are also denoted 36A, and the first switches 36 connected directly to the second piezoelectric assembly 12B are also denoted 36B.

[0079] In the examples of figures 1, 4, 5 and 8, the first switches 36A connected directly to the first piezoelectric assembly 12A are also denoted K5, K6, and the first switches 36B connected directly to the second piezoelectric assembly 12B are also denoted K7, K8.

[0080] Similarly, the first midpoint 38 directly connected to the first piezoelectric assembly 12A is also denoted 38A, and the first midpoint 38 directly connected to the second piezoelectric assembly 12B is also denoted 38B.

[0081] The converter 10 comprises a second switching bridge 40 comprising two second switching branches 42, each second switching branch 42 being connected between two terminals 44 for supplying the output voltage Vout and comprising at least two second switches 46 connected in series and connected together at a second midpoint 48. Among the two supply terminals 44, one has a lower potential, denoted Voutn, than the other, denoted Voutp. The second switching bridge 40 is preferably made up of the two second switching branches 42.

[0082] In the examples of figures 1, 4, 5 and 8, each second switching branch 42 comprises two second switches 46 connected in series and connected at the second midpoint 48. Each second switching branch 42 is preferably made up of the two second switches 46.

[0083] In the examples of figures 1, 5 and 8, the two second switches 46 are denoted Ki, K2 for one of the two second switching branches 42, and respectively K3, K4 for the other of the two second switching branches 42.

[0084] When the electrical energy converter 10 is configured to deliver several separate output voltages Voutj, it comprises, for each respective output voltage Voutj, a second respective switching bridge 40, each second switching branch 42 being connected between two terminals 44 for supplying the respective output voltage Voutj.

[0085] In the example of [Fig.4], the electrical energy converter 10 is configured to deliver two distinct output voltages, namely a first output voltage Vout_i and a second output voltage Vout_2. According to this example, the converter 10 then comprises two second switching bridges 40, the one associated with the first output voltage Vout_i being denoted 40_l and the one associated with the second output voltage Vout_2 being denoted 40_2. Each second switching branch 42 being connected between two terminals 44 for supplying the respective output voltage Vout_i, Vout_2. In this example, the lower potentials of the output voltages Vout_i, Vout_2 are respectively denoted Vout_i, Vout_2, and the higher potentials of the output voltages Vout_i, Vout_2 are respectively denoted Vout_i, Vout_2. In this example again, the second switches 46 are denoted Ki i, K2.i, K3.i, K41 for the second switching bridge 40_l associated with the first output voltage Vout_i, and the second switches 46 are denoted K[j2, K2 2, K3j2, K4j2 for the second switching bridge 40_2 associated with the second output voltage Vout 2. .

[0086] For the sake of distinguishing between the second switches 46 connected directly to the first piezoelectric assembly 12A and those connected directly to the second piezoelectric assembly 12B, the second switches 46 connected directly to the first piezoelectric assembly 12A are also denoted 46A, and the second switches 46 connected directly to the second piezoelectric assembly 12B are also denoted 46B.

[0087] In the examples of figures 1, 5 and 8, the second switches 46A connected directly to the first piezoelectric assembly 12A are also denoted Kb K2, and the second switches 46B connected directly to the second piezoelectric assembly 12B are also denoted K3, K4.

[0088] In the example of [Fig.4], the second switches 46A connected directly to the first piezoelectric assembly 12A are also denoted Ki>b K2>b for the second switching bridge 40_l associated with the first output voltage Voutb and Ki>2, K2>2, for the second switching bridge 40_2 associated with the second output voltage V out_2. In this example, the second switches 46B connected directly to the second piezoelectric assembly 12B are also denoted K3,b K41 for the second switching bridge 40_l associated with the first output voltage Vout_i, and K3 2, K4j2 for the second switching bridge 40_2 associated with the second output voltage V out_2*

[0089] Similarly, the second midpoint 48 connected directly to the first set piezoelectric 12A is also denoted 48A, and the second midpoint 48 connected directly to the second piezoelectric assembly 12B is also denoted 48B.

[0090] The converter 10 comprises one or more pairs of first 12A and second 12B piezoelectric assemblies, each piezoelectric assembly 12A, 12B comprising at least one piezoelectric element 15 and being connected between respective first 38 and second 48 midpoints, the midpoints 38, 48 between which the piezoelectric assemblies 12A, 12B are connected being distinct from one piezoelectric assembly 12A to the other 12B.

[0091] In the examples of Figures 1, 5 and 8, the converter 10 comprises a single pair of first 12A and second 12B piezoelectric assemblies.

[0092] When the electrical energy converter 10 is configured to deliver several distinct output voltages Voutj, it comprises, for each respective output voltage Voutj, a respective pair of first 12A and second 12B piezoelectric assemblies.

[0093] In the example of [Fig.4], the electrical energy converter 10 is configured to deliver two separate output voltages, and then comprises two pairs of first 12A and second 12B piezoelectric assemblies.

[0094] Each switch of the converter 10, namely each of the first 36 and second 46 switches, is preferably a unidirectional current and unidirectional voltage switch. The switch 36, 46 comprises, for example, a transistor, or a diode, or a transistor and a diode in antiparallel, not shown. The switch 36, 46 is preferably made up of the transistor, or the diode, or the transistor and the diode in antiparallel. Alternatively, the switch 36, 46 comprises a combination of several transistors, and is preferably made up of such a combination of several transistors. As a further variant, the switch 36, 46 comprises a mechanical switch, such as a MEMS (MicroElectroMechanical System) microswitch.

[0095] 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.

[0096] Each piezoelectric assembly 12A, 12B is constituted according to one of the constitutions among the group consisting of: a single piezoelectric element 15; several piezoelectric elements 15 connected in series; several piezoelectric elements 15 connected in parallel; a piezoelectric element 15 and a auxiliary capacitor, not shown, connected in series; a piezoelectric element 15 and an auxiliary capacitor connected in parallel; and an arrangement of several parallel branches, each branch comprising one or more piezoelectric elements 15 connected in series or an auxiliary capacitor.

[0097] The auxiliary capacitor is typically of greater capacity, preferably at least three times greater, than a reference capacity Co, described below, of the piezoelectric element(s) 15.

[0098] As an optional addition, the first 12A and second 12B piezoelectric assemblies share the same piezoelectric material, while having the electrodes of the first assembly 12A distinct from those of the second assembly 12B. According to this optional addition, the pairs of electrodes of the first assembly 12A, and respectively those of the second assembly 12B, cover distinct material surfaces. Furthermore, the electrodes of the first assembly 12A cannot in this case directly induce a significant electric field in the part of the piezoelectric material belonging to the second assembly 12B.According to this optional addition, the capacitance between any one of the electrodes of the first set 12A and any one of the electrodes of the second set 12B is negligible (at least 10 times lower) compared to a reference capacitance Co, described below, of each of the sets 12A, 12B, for example by not being directly opposite each other on either side of the material. This sharing of the same material makes it possible, for example, to facilitate the implementation of the first 12A and second 12B piezoelectric sets (limiting the number of part(s), sharing the fixing means); and also to synchronize the vibration of the two sets 12A, 12B, without there being a significant transfer of energy from one set to the other ( <l / 10ème de la puissance de sortie). .

[0099] The piezoelectric element 15 is known per se, and is typically modeled, close to the resonance mode used, in the form of a capacitor 52 and a resonant branch 54 connected in parallel with the capacitor 52, the capacitor 52 and the resonant branch 54 being connected between a first electrode 56 and a second electrode 58 of the piezoelectric element 15, as illustrated in the modeling of the piezoelectric element 15 represented in a bubble 60 in [Fig.l]. The resonant branch 54 is typically an RLC branch formed of a capacitor 62, a resistor 64 and a coil 66 connected in series. The capacitance of the capacitor 52 connected in parallel with the resonant branch 54 is called parallel capacitance, or blocked capacitance, or reference capacitance, and denoted Co. The voltage across the terminals of the piezoelectric element 15 then typically corresponds to the voltage across the terminals of the capacitor 52.

[0100] In the present description, a so-called total piezoelectric voltage Vp is by convention the sum of each of the voltages across the terminals of the first 12A, and respectively second 12B, piezoelectric assemblies. In particular, the voltage across the terminals of the first piezoelectric assembly 12A is denoted Vpl, and that across the terminals of the second piezoelectric assembly 12B is denoted Vp2. The total piezoelectric voltage Vp is then equal to the sum of these voltages Vpl and Vp2, i.e. Vpi+Vp2. The two piezoelectric assemblies 12A, 12B, and the piezoelectric elements 15 constituting them, are preferably identical, and have substantially the same voltage across their terminals apart from a possible offset voltage VOffset, so that the voltages Vpl and Vp2 are equal to Vp / 2+ / -VOffset, according to the following equations:

[0101] [Math.l]

[0102] [Math.2] VV y + yy Py pl Z oJ J set p2 Z o JJ set

[0103] The VOffset voltage is a substantially constant component on the scale of a resonance period and has little impact on the charge or energy balance over a period. This VOffset voltage evolves slowly with respect to the driving frequency, its ripple is typically at a frequency at least 10 times lower than the driving frequency of the piezoelectric assemblies 12A, 12B. Furthermore, when the voltages Vpi+Vp2 are added together, this offset voltage VOffset disappears, and the total piezoelectric voltage Vp is obtained, as described in the different cycles. In practice, this offset voltage Voffset does not impact the driving law, and allows completely independent potentials Vinn and Voutn at low frequency.

[0104] In the example of [Fig.4] where the electrical energy converter 10 is configured to deliver the first Vout_i and second Vout 2 output voltages and then comprises two pairs of first 12A and second 12B piezoelectric assemblies, the total piezoelectric voltage for a first pair of first 12A and second 12B piezoelectric assemblies associated with the first output voltage Vout_i is denoted Vpl, and that for a second pair of first 12A and second 12B piezoelectric assemblies associated with the second output voltage Vout 2 is denoted Vp 2. In particular, the voltage across the first piezoelectric assembly 12A is denoted Vp_i i for the first pair and Vp 2 ji for the second pair, and that across the second piezoelectric assembly 12B is denoted Vp_ij2 for the first pair and Vp 2 j2 for the second pair.Each total piezoelectric voltage Vpl, Vp 2 is then equal to the sum of these respective voltages Vp_i i, Vp_ij2 and Vp 2ji, Vp 2j2, i.e. Vp_i i + Vp_ij2, and respectively Vp 2ji + Vp 2j2. The two piezoelectric assemblies 12A, 12B, and the piezoelectric elements 15 constituting them, are preferably identical, and have substantially the same voltage at their terminals at a possible voltage . offset VOffSet_i, VoffSet_2 near, so that the voltages Vp_i i, Vp_2,i and Vp_i>2, Vp 2>2 are each equal to half of the total piezoelectric voltage Vp_i+ / -Voffset_i, Vp 2 + / -V offset_2 respectively, according to the following equations:

[0105] [Math.3]

[0106] [Math.4] + V N offset

[0107] [Math.5]

[0108] [Math.6] + y 2 of / set_2 and V p_^ V, —L=2 _ y 2 offset_2

[0109] Furthermore, in the present description and as shown in Figures 1, 5 and 8, the voltage between the first midpoints 38 is denoted Vpa, and is by convention equal to the potential difference (Vpai - Vpa2), where Vpai is the potential of the first midpoint 38 connected to the first piezoelectric assembly 12A, and Vpa2 is the potential of the other first midpoint 38 connected to the second piezoelectric assembly 12B. The voltage between the second midpoints 48 is denoted Vpb, and is by convention equal to the potential difference (Vpb2 - Vpbi), where Vpbi is the potential of the second midpoint 48 connected to the first piezoelectric assembly 12A, and Vpb2 is the potential of the other second midpoint 48 connected to the second piezoelectric assembly 12B.

[0110] By convention and as shown in Figures 1, 5 and 8, the voltage across the terminals of the first piezoelectric assembly Vpl is equal to the potential difference (Vpai - Vpbi), and that across the terminals of the second piezoelectric assembly Vp2 is equal to the potential difference (Vpb2 - Vpa2).

[0111] In the example of [Fig.4] where the electrical energy converter 10 comprises two pairs of first 12A and second 12B piezoelectric assemblies and two second switching bridges 40_l, 40_2, the voltage between the first midpoints 38 is also denoted Vpa, and is by convention equal to the potential difference (Vpai - Vpa2), where Vpai is the potential of the first midpoint 38 connected to the first piezoelectric assembly 12A, and Vpa2 is the potential of the other first midpoint 38 connected to the second piezoelectric assembly 12B.The voltage between the second midpoints 48 is noted Vpb_i for the second switching bridge 40_l associated with the first output voltage Vout_i, is by convention equal to the potential difference (Vpb2>i - Vpbi i), where Vpbi i is the potential of the second midpoint 48 connected to the first piezoelectric assembly 12A, and Vpb2ji is the potential of the other second midpoint 48 connected to the second piezoelectric assembly 12B, this for the . second switching bridge 40_l associated with the first output voltage Vout_i. Similarly, the voltage between the second midpoints 48 is noted Vpb_2 for the second switching bridge 40_2 associated with the second output voltage Vout 2, is by convention equal to the potential difference (Vpb2>2 - Vpbi>2), where Vpbi>2 is the potential of the second midpoint 48 connected to the first piezoelectric assembly 12A, and Vpb2>2 is the potential of the other second midpoint 48 connected to the second piezoelectric assembly 12B, this for the second switching bridge 40_2 associated with the second output voltage Vout_2.

[0112] By convention and as shown in [Fig.4], the voltage across the terminals of the first piezoelectric assembly Vp_i i of the first pair is equal to the potential difference (Vpai - Vpbi i), and that across the terminals of the second piezoelectric assembly Vp_ij2 of the first pair is equal to the potential difference (Vpb2>i - Vpa2). Similarly, the voltage across the terminals of the first piezoelectric assembly Vp_2>i of the second pair is equal to the potential difference (Vpai - Vpbi>2), and that across the terminals of the second piezoelectric assembly Vp_2>2 of the second pair is equal to the potential difference (Vpb2,2 - Vpa2).

[0113] The resonance frequency is the frequency at which the piezoelectric element 15 oscillates and consequently its current IL, visible in [Fig.l]. The conversion cycle is synchronized with a mechanical movement of the piezoelectric element 15, and the control frequency is then set to the mechanical oscillation frequency. In practice, this oscillation frequency depends on the operating point of the converter 10: values ​​of the three voltage levels and the output current. Depending on the operating point, this oscillation frequency typically varies between the so-called series resonance frequency of the piezoelectric element 15 (cos= 1 / ^^.(^ ) where Lr and Cr correspond to the inductance and capacitance of the resonant branch 54 and the so-called parallel resonance frequency of the piezoelectric element 15 (a)p=l / ^(Lr.Cr.C0 / (Cr+C0))), also respectively called the resonance frequency and antiresonance frequency of the piezoelectric element 15.The operating frequency of the converter 10 is then between these two resonance and antiresonance frequencies of the piezoelectric element 15. The operating point varies slowly with respect to the oscillation frequency of the piezoelectric element 15. The operating point typically varies at less than 10kHz, while the oscillation frequency of the piezoelectric element 15 is typically greater than or equal to 100kHz. As a result, the operating frequency of the converter 10 varies little from one period to the next.

[0114] Generally speaking, for the electrical energy converter 10 with the piezoelectric assemblies 12A, 12B and controlled by the electronic control device 20, the number of phases II, IV, VI at substantially constant voltage is typically of at least 2, preferably equal to 3, while being able to be greater than or equal to 4 with the implementation of the piloting described in application FR 21 07345 filed on July 7, 2021.

[0115] Each phase II, IV, VI at substantially constant voltage is capable of being obtained from a combination of the input and output voltages, in positive or negative value. The energy converter 10 then makes it possible to exchange energy during the phases II, IV, VI at substantially constant voltage, and consequently, with the voltage combinations used to obtain these phases II, IV, VI at substantially constant voltage. It is in particular possible to transfer energy from a phase at substantially constant voltage of low voltage to a phase at substantially constant voltage of higher voltage, and by the play of the aforementioned combinations ultimately obtain a voltage step-down converter, which may seem counter-intuitive.Conversely, it is also possible to transfer energy from a phase with a substantially constant voltage of high voltage to a phase with a substantially constant voltage of lower voltage, and by the play of the aforementioned combinations ultimately obtain a voltage boost converter. Those skilled in the art will then understand that it is possible to have a boost cycle seen by the piezoelectric assemblies 12A, 12B while the electrical energy converter 10 is a step-down converter, and conversely to have a step-down cycle seen by the piezoelectric assemblies 12A, 12B while the electrical energy converter 10 is a step-up converter.

[0116] By convention, if power is supplied to the piezoelectric assemblies 12A, 12B 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 assemblies 12A, 12B. Conversely, if power is delivered, or drawn, from the piezoelectric assemblies 12A, 12B 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 assemblies 12A, 12B.As previously indicated, the conversion cycle seen by the piezoelectric assemblies 12A, 12B is likely to be a step-up cycle while the electrical energy converter 10 operates as a step-down converter, and conversely the conversion cycle seen by the piezoelectric assemblies 12A, 12B is likely to be a step-down cycle while the electrical energy converter 10 operates as a step-up converter.

[0117] The electronic control device 20 is configured to control the electrical energy converter 10, in particular to control the control of the switches 36, 46 of the converter, in order to alternate phases II, IV, VI at substantially the same voltage. constant at the terminals of the piezoelectric assemblies 12A, 12B and of the phases I, III, V at substantially constant load, that is to say in substantially open circuit, at the terminals of said piezoelectric assemblies 12A, 12B.

[0118] The electronic control device 20 is for example produced in the form of an electronic circuit comprising one or more electronic components.

[0119] Alternatively, the electronic control device 20 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.

[0120] According to the invention, the electronic control device 20 is configured to, during each phase I, III, V at substantially constant load, control in the closed position at the same time at most one respective switch among the switches 36A, 46A connected directly to the first piezoelectric assembly 12A and at most one respective switch among the switches 36B, 46B connected directly to the second piezoelectric assembly 12B, and control in the open position all the other switches 36, 46 of the first and second switching branches 32, 42.

[0121] In other words, during each phase I, III, V at substantially constant load, at most one respective switch among the switches 36A, 46A connected directly to the first piezoelectric assembly 12A and at most one respective switch among the switches 36B, 46B connected directly to the second piezoelectric assembly 12B are in the closed position at the same time, all the other switches 36, 46 of the first and second switching branches 32, 42 being in the open position.

[0122] In other words, during each phase I, III, V at substantially constant load, at each instant at most one respective switch among the switches 36A, 46A connected directly to the first piezoelectric assembly 12A is in the closed position, and at most one respective switch among the switches 36B, 46B connected directly to the second piezoelectric assembly 12B is in the closed position, and all the other switches 36, 46 of the first and second switching branches 32, 42 are in the open position.

[0123] In the examples of figures 1, 5 and 8, during each phase I, III, V at substantially constant load, at most one respective switch among the switches K2, K5, K6 is in the closed position, and at most one respective switch among the switches K3, K4, K7, K8 is in the closed position, all the other switches of the first and second switching branches 32, 42 being in the open position.

[0124] In the example of [Fig.4] where the electrical energy converter 10 is configured to deliver the first Vout_i and second Vout_2 distinct output voltages res pectives, and then comprises two pairs of first 12A and second 12B piezoelectric assemblies and two second switching bridges 40_l, 40_2, on the one hand for converting the input voltage Vin into the first output voltage Vout_i via the first switching bridge 30 and the second switching bridge 40_l associated with the first output voltage Vout_i, during each phase I, III, V at substantially constant load, at most one respective switch among the switches Ki>b K2>b K5, K6 is in the closed position, and at most one respective switch among the switches K3>b K41, K7, K8 is in the closed position, all the other switches of the switching bridges 30, 40_l being in the open position.On the other hand, for the conversion of the input voltage Vin into the second output voltage Vout 2 via the first switching bridge 30 and the second switching bridge 40_2 associated with the second output voltage V out_2, during each phase I, III, V at substantially constant load, at most one respective switch among the switches Kb2, K2>2, K5, K6 is in the closed position, and at most one respective switch among the switches K3 2, K4j2, K7, K8 is in the closed position, all the other switches of the switching bridges 30, 40_2 being in the open position.

[0125] In addition, the electronic control device 20 is configured to, during phases II, IV, VI at substantially constant voltage across the terminals of the piezoelectric assemblies 12A, 12B, control the control of the switches 36, 46 of the converter 10, in order to have the value Va, Vb, Vc of the voltage of each of phases II, IV, VI at substantially constant voltage distinct from the zero value.

[0126] According to this addition, the electronic control device 20 is preferably configured to, during phases II, IV, VI at substantially constant voltage across the terminals of the piezoelectric assemblies 12A, 12B, control the control of the switches 36, 46 of the converter 10, in order to have the value Va, Vb, Vc of the voltage of each of phases II, IV, VI at substantially constant voltage chosen from the group consisting of: difference Vin - Vout between the value of the input voltage Vin and that of the output voltage Vout; difference Vout - Vin between the value of the output voltage Vout and that of the input voltage Vin; sum Vin + Vout of the values ​​of the input voltages Vin and output Vout; and opposite of the sum -Vin -Vout of the values ​​of the input voltages Vin and output Vout.

[0127] The operation of the converter 10 in the example of [Fig.l] will now be explained according to four voltage step-down configurations, namely a first step-down configuration A1, a second step-down configuration A2, a third step-down configuration A3 and a fourth step-down configuration A4 with respect to [Fig.2]; then according to four voltage step-up configurations, namely a first step-up configuration E1, a second step-up configuration E2, a third step-up configuration E3 and a fourth step-up configuration E4 with respect to [Fig.3].

[0128] The method for controlling the electrical energy converter 10 is then implemented by the electronic control device 20 and comprises the control, during a respective resonance cycle of the piezoelectric assemblies 12A, 12B, of a switching of each of the switches 36, 46 to alternate phases II, IV, VI at substantially constant voltage across the terminals of the piezoelectric assemblies 12A, 12B and phases I, III, V at substantially constant charge across the terminals of said piezoelectric assemblies 12A, 12B,

[0129] For each of the step-down, step-up configurations, respectively, and according to the invention, during each phase I, III, V at substantially constant load, at most one respective switch among the switches 36A, 46A connected directly to the first piezoelectric assembly 12A and at most one respective switch among the switches 36B, 46B connected directly to the second piezoelectric assembly 12B are controlled in the closed position at the same time, and all the other switches 36, 46 of the first and second switching branches 32, 42 are controlled in the open position.

[0130] Those skilled in the art will note that by very boost configuration, we typically mean a configuration where the gain, i.e. the ratio of the output voltage Vout divided by the input voltage Vin, is greater than 2, i.e. Vout / Vin > 2. Corollarily, by very step-down configuration, we typically mean a configuration where the gain, i.e. the ratio of the output voltage Vout to the input voltage Vin, is less than 1 / 2, i.e. Vout / Vin < 1 / 2.

[0131] Similarly, by step-up configuration, we typically mean a configuration where said gain is between 1 and 2, i.e. Vin < Vout < 2Vin. Corollarily, by step-down configuration, we typically mean a configuration where said gain is between 1 / 2 and 1, i.e. Vin / 2 < Vout < Vin. Al step-down configuration

[0132] By convention, for the first step-down configuration A1, the highest voltage level for the total piezoelectric voltage Vp is that at the value Va. 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 assemblies 12A, 12B, is oriented so as to be positive during this voltage level at the value Va. Consequently, at constant load, the total piezoelectric voltage Vp tends to decrease when the current IL is positive, and consequently to increase when the current IL is negative.

[0133] From the time instant to to the time instant tb corresponding to a first phase I, the sign of the current IL flowing in the piezoelectric elements 15 leads to an increase in the total piezoelectric voltage Vp. The total piezoelectric voltage Vp goes from the value Vc equal to -Vin-Vout to the value Vb equal to -Vin+Vout. Only the voltage Vpb needs to be changed, it must go from -Vout to +Vout, which it does naturally with the increase in the total piezoelectric voltage Vp, while the voltage Vpa remains constant and fixed at -Vin by keeping the switches K5 and K8 closed.

[0134] During this first phase I, at substantially constant load, only switches K5 and K8 are then in the closed position.

[0135] At the time instant tb the voltages Vpa and Vpb are therefore already repositioned on the values ​​of the next voltage level, and the closing of the switches Kb K4 is carried out in ZVS mode, that is to say with a substantially zero voltage at their terminals before their closing. If the switches Ki and K4 have an intrinsic reverse diode or an additional diode placed in parallel, their conduction can be done naturally with regard to the sign of the current. The switches K5, K8 were already closed.

[0136] From time instant ti to time instant t2, corresponding to a second phase II, the switches Kb K4, K5 and K8 are in the closed position. The total piezoelectric voltage Vp is equal to -Vin+Vout. A positive power is drawn from the input voltage V in at the same time as a positive power is supplied to the output voltage Vout.

[0137] From time instant t2 to time instant t3, corresponding to a third phase III, the sign of the current IL leads to an increase in the total piezoelectric voltage Vp. The total piezoelectric voltage Vp therefore changes from -Vin+Vout to +Vin-Vout. Seen from the piezoelectric assemblies 12A, 12B, the application of the value Va at time instant t3 does not induce a voltage variation at its terminals and from this point of view the closing of the switches at time instant t3 does not induce losses for the piezoelectric assemblies 12A, 12B.

[0138] However, the voltage across the switches is not zero and their closure induces losses specific to the energy stored in their parasitic capacitances, for example their output capacitance. Indeed, the initial total piezoelectric voltage Vp is equal to -Vin +Vout, the voltage Vpa being equal to -Vin and the voltage Vpb equal to +Vout, and the sign of the current IL allows an increase in the total piezoelectric voltage Vp contributing to the increase in the voltage Vpa, but not to the decrease in the voltage Vpb which must go from +Vout to -Vout. Therefore, at the time instant t3, the voltage Vpb is still at +Vout while the voltage Vpa is equal to the total piezoelectric voltage Vp minus the voltage Vpb, i.e. (+Vin-Vout)-Vout, or Vin-2Vout.

[0139] Before their closure at time instant t3, switches K2 and K3 have a potential difference Vout across their terminals, which induces losses when they close. Before their closure at time instant t3, switches K6 and K7 have a potential difference (Vin-Vpa) / 2, i.e. (Vin-(Vin-2Vout)) / 2 = Vout across their terminals, which which induces losses when they are closed.

[0140] In practice, if switches K2 and K3 have a reverse diode (intrinsic or additional placed in parallel), with regard to the sign of current IL, switches K2 and K3 do not need to be forced to close, but can close naturally a little later. In this case, the energy stored in their parasitic output capacitance will be dissipated in switches K6 and K7. At the common mode level, if the switches K2 and K3 are substantially identical and K6 and K7 are substantially identical, and the switches K6 and K7 are closed substantially at the same time, (the same for the switches K2 and K3 if they are forced to close), then, by symmetry, the current drawn on the potential Vinp opposes the current drawn on the potential Vinn, and the same for the potential Voutp and the potential V outn, and there is no common mode current injected on the output voltage Vout.

[0141] During this third phase III, at a substantially constant load, only the switches Ki and K4 are then passing or controlled in the closed position.

[0142] From time instant t3 to time instant t4, corresponding to a fourth phase IV, switches K2, K3, K6 and K7 are on or closed. The total piezoelectric voltage Vp is equal to Vin-Vout. A positive power is drawn from the input voltage Vin at the same time as a positive power is supplied to the output voltage Vout.

[0143] From time instant t4 to time instant t5, corresponding to a fifth phase V, the sign of current IL leads to a decrease in the total piezoelectric voltage Vp. The total piezoelectric voltage Vp therefore changes from +Vin-Vout to -Vin-Vout. Only voltage Vpa needs to be modified, and must change from +Vin to -Vin, which it does naturally with the decrease in the total piezoelectric voltage Vp, while voltage Vpb remains constant and fixed at -Vout via keeping switches K2 and K3 on (either by maintaining a closing command, or naturally via their intrinsic reverse diode, or even via an additional parallel diode).

[0144] During this fifth phase V, at substantially constant load, only switches K2 and K3 are then in the closed position.

[0145] At time instant t5, voltage Vpa and voltage Vpb are therefore already repositioned to the values ​​of the next voltage level, and the closing of switches K5, K8 is carried out in ZVS mode. If switches K5 and K8 have an intrinsic reverse diode or an additional diode placed in parallel, their conduction can be done naturally with regard to the sign of the current. Switches K2, K3 were already conducting or closed.

[0146] From time instant t5 to time instant t6 (or time instant t0), corresponding to a sixth phase VI, switches K2, K3, K5 and K8 are on or closed. The total piezoelectric voltage Vp is equal to -Vin-Vout. A power positive is returned to the input voltage Vin at the same time as positive power is supplied to the output voltage Vout. A2 step-down configuration

[0147] The second step-down configuration A2 differs from the first step-down configuration A1, described previously, only in that it integrates an excursion to the voltage VZvs equal to +Vin+Vout at the time instant t3. This voltage excursion makes it possible to move from the total piezoelectric voltage level Vp equal to -Vin+Vout to the total piezoelectric voltage level Vp equal to Vin-Vout in ZVS switching at the switches.

[0148] This transition is made in two stages, a first stage from time instant t2 to time instant t3 to pass from the total piezoelectric voltage Vp equal to -Vin+Vout to the total piezoelectric voltage Vp equal to Vin+Vout, then a second stage from time instant t3 to time instant t3b to pass from the total piezoelectric voltage Vp equal to Vin+Vout to the total piezoelectric voltage Vp equal to Vin-Vout.

[0149] From time instant t2 to time instant t3, corresponding to the first step of the third phase III, the sign of the current IL leads to an increase in the total piezoelectric voltage Vp. The total piezoelectric voltage Vp therefore changes from -Vin+Vout to Vin+Vout. Only the voltage Vpa needs to be modified, and must change from -Vin to +Vin, which it does naturally with the increase in the total piezoelectric voltage Vp, while the voltage Vpb remains constant and fixed at +Vout via the maintenance of the switches Ki and K4 passing (either by maintaining a closing command, or naturally via their intrinsic reverse diode, or even via an additional parallel diode).

[0150] During the first stage of the third phase III, at substantially constant load, only the switches Ki and K4 are then passing or controlled in the closed position.

[0151] At time instant t3, voltage Vpa and voltage Vpb are therefore pre-positioned on respectively +Vin and +Vout, and the closing of switches K6, K7 is carried out in ZVS mode. Switches K6 and K7 close, while switches Ki and K4 open.

[0152] From time instant t3 to time instant t3b, the sign of the current IL leads to a decrease in the total piezoelectric voltage Vp. The total piezoelectric voltage Vp therefore changes from Vin+Vout to Vin-Vout. Only the voltage Vpb needs to be modified, and must change from +Vout to -Vout, which it does naturally with the decrease in the total piezoelectric voltage Vp, while the voltage Vpa remains constant and fixed at +Vin via keeping the switches K6 and K7 closed.

[0153] During the second stage of the third phase III, at substantially constant load, only switches K6 and K7 are then controlled in the closed position.

[0154] At the time instant t3b, the voltage Vpa and the voltage Vpb are therefore already repositioned on the values ​​of the next voltage level, and the closing of switches K2, K3 is carried out in ZVS mode. If switches K2 and K3 have an intrinsic reverse diode or an additional diode placed in parallel, their conduction can be done naturally with regard to the sign of the current. Switches K6, K7 were already closed. At time instant t3b, switches K2 and K3 close or become conducting. A3 step-down configuration

[0155] By convention, for the third step-down configuration A3, the highest voltage level for the total piezoelectric voltage Vp is that at the value Vc. During this level, power is delivered, or drawn, from the piezoelectric assemblies 12A, 12B. By convention, the current IL flowing in the piezoelectric elements 15, i.e. in the piezoelectric assemblies 12A, 12B, is oriented so as to be positive during this voltage level at the value Vc. Consequently, at constant load, the total piezoelectric voltage Vp tends to increase when the current IL is positive, and consequently to decrease when the current IL is negative.

[0156] From the time instant L to the time instant tb corresponding to the first phase I, the sign of the current IL leads to a decrease in the total piezoelectric voltage Vp. The total piezoelectric voltage Vp therefore changes from the value Vc equal to Vin+Vout to the value Vb equal to Vin-Vout. Only the voltage Vpb needs to be modified, and must change from +Vout to -Vout, which it does naturally with the decrease in the total piezoelectric voltage Vp, while the voltage Vpa remains constant and fixed at +Vin via keeping the switches K6 and K7 closed.

[0157] During this first phase I, at substantially constant load, only switches K6 and K7 are then controlled in the closed position.

[0158] At the time instant tb the voltage Vpa and the voltage Vpb are therefore already repositioned on the values ​​of the next voltage level, and the closing of the switches K2, K3 is carried out in ZVS mode. If the switches K2 and K3 have an intrinsic reverse diode or an additional diode placed in parallel, their conduction can be done naturally with regard to the sign of the current. The switches K6, K7 were already closed.

[0159] From time instant ti to time instant t2, corresponding to the second phase II, the switches K2, K3, K6 and K7 are on or closed. The total piezoelectric voltage Vp is equal to Vin-Vout. A positive power is drawn from the input voltage Vin at the same time as a positive power is supplied to the output voltage Vout.

[0160] From the time instant t2 to the time instant t3, corresponding to the third phase III, the sign of the current IL leads to a decrease in the total piezoelectric voltage Vp. The total piezoelectric voltage Vp therefore changes from Vin-Vout to -Vin+Vout. Seen from the piezoelectric assemblies 12A, 12B, the application of the value Va at the instant time t3 does not induce any voltage variation at its terminals and from this point of view the closing of the switches at the time instant t3 does not induce any losses for the piezoelectric assemblies 12A, 12B.

[0161] However, the voltage across the switches is not zero and their closure induces losses specific to the energy stored in their parasitic capacitances, for example their output parasitic capacitance. Indeed, the initial total piezoelectric voltage Vp is equal to Vin-Vout, the voltage Vpa being equal to Vin and the voltage Vpb being equal to -Vout; and the sign of the current IL allows a decrease in the total piezoelectric voltage Vp, contributing to the decrease in the voltage Vpa, but not to the increase in the voltage Vpb which must go from -Vout to +Vout. Therefore, at the time instant t3, the voltage Vpb is still at -Vout while the voltage Vpa is equal to Vp minus the voltage Vpb, i.e. (-Vin+Vout)-(-Vout) = -Vin+2Vout.

[0162] Before their closure at time instant t3, switches Ki and K4 have a potential difference Vout across their terminals, which induces losses when they close. Before their closure at time instant t3, switches K5 and K8 have a potential difference (Vin+Vpa) / 2 = (Vin+(-Vin+2Vout)) / 2 = Vout across their terminals, which induces losses when they close. In practice, if switches Ki and K4 have a reverse diode (intrinsic or additional placed in parallel), with regard to the sign of current IL, switches Ki and K4 do not need to be forced to close, but can close naturally a little later. In this case, the energy stored in their output capacitance will be dissipated in switches K5 and K8.At the common mode level, if the switches Ki and K4 are substantially identical and the switches K5 and K8 are substantially identical, and the switches K5 and K8 are closed substantially at the same time, (the same for the switches Ki and K4 if they are forced to close), then, by symmetry, the current drawn on the potential Vinp opposes the current drawn on the potential Vinn, and the same for the potential Voutp and the potential Voutn, and there is therefore no common mode current injected on the output voltage Vout.

[0163] During this third phase III, at a substantially constant load, only switches K2 and K3 are on or controlled in the closed position.

[0164] From time instant t3 to time instant t4, corresponding to the fourth phase IV, the switches Kb K4, K5 and K8 are on or closed. The total piezoelectric voltage Vp is equal to -Vin+Vout. A positive power is drawn from the input voltage Vin at the same time as a positive power is supplied to the output voltage Vout.

[0165] From time instant t4 to time instant t5, corresponding to the fifth phase V, the sign of the current IL leads to an increase in the total piezoelectric voltage V p. The total piezoelectric voltage Vp therefore changes from -Vin+Vout to Vin+Vout. Only the voltage Vpa needs to be modified, and must go from -Vin to +Vin, which it does naturally with the increase in the total piezoelectric voltage Vp, while voltage Vpb remains constant and fixed at +Vout via the maintenance of switches Ki and K4 passing (either by maintaining a closing command, or naturally via their intrinsic reverse diode, or even via an additional parallel diode).

[0166] During this fifth phase V, at substantially constant load, only the switches Ki and K4 are then passing or controlled in the closed position.

[0167] At time instant t5, voltage Vpa and voltage Vpb are therefore already repositioned to the values ​​of the next voltage level, and the closing of switches K6, K7 is carried out in ZVS mode. If switches K6 and K7 have an intrinsic reverse diode or an additional diode placed in parallel, their conduction can be done naturally with regard to the sign of the current. Switches K4 were already conducting or closed.

[0168] From time instant t5 to time instant t6 (or time instant t0), corresponding to the sixth phase VI, the switches Kb K4, K6 and K7 are on or closed. The total piezoelectric voltage Vp is equal to Vin+Vout. A positive power is restored to the input voltage Vin at the same time as a positive power is supplied to the output voltage Vout. A4 step-down configuration

[0169] The fourth step-down configuration A4 differs from the third step-down configuration A3, described previously, only in that it integrates an excursion at V zvs equal to -Vin-Vout at the time instant t3. This voltage excursion makes it possible to move from the total piezoelectric voltage level Vp equal to Vin-Vout to the total piezoelectric voltage level Vp equal to -Vin+Vout in ZVS switching at the switches.

[0170] This transition is made in two stages, a first stage from time instant t2 to time instant t3 to pass from the total piezoelectric voltage Vp equal to Vin-Vout to the total piezoelectric voltage Vp equal to -Vin-Vout, then a second stage from time instant t3 to time instant t3b to pass from the total piezoelectric voltage Vp equal to -Vin-Vout to the total piezoelectric voltage Vp equal to -Vin+Vout.

[0171] From time instant t2 to time instant t3, corresponding to the third phase III, the sign of the current IL leads to a decrease in the total piezoelectric voltage Vp. The total piezoelectric voltage Vp therefore changes from Vin-Vout to -Vin-Vout. Only the voltage Vpa needs to be modified, and must change from Vin to -Vin, which it does naturally with the decrease in the total piezoelectric voltage Vp, while the voltage Vpb remains constant and fixed at -Vout via the maintenance of the switches K2 and K3 passing (either by maintaining a closing command, or naturally via their intrinsic reverse diode, or even via an additional parallel diode).

[0172] During the first stage of the third phase III, at substantially constant load, only switches K2 and K3 are then passing or controlled in the closed position.

[0173] At time instant t3, voltage Vpa and voltage Vpb are therefore pre-positioned on -Vin and -Vout respectively, and the closing of switches K5, K8 is carried out in zvs mode.

[0174] At time instant t3, switches K5 and K8 close, while switches K2 and K3 open.

[0175] From time instant t3 to time instant t3b, the sign of the current IL leads to an increase in the total piezoelectric voltage Vp. The total piezoelectric voltage Vp therefore changes from -Vin-Vout to -Vin+Vout. Only the voltage Vpb needs to be modified, and must change from -Vout to +Vout, which it does naturally with the increase in the total piezoelectric voltage Vp, while the voltage Vpa remains constant and fixed at -Vin via keeping the switches K5 and K8 closed.

[0176] During the second stage of the third phase III, at substantially constant load, only switches K5 and K8 are then controlled in the closed position.

[0177] At time instant t3b, voltage Vpa and voltage Vpb are therefore already repositioned to the values ​​of the next voltage level, and the closing of switches Kb K4 is carried out in ZVS mode. If switches Ki and K4 have an intrinsic reverse diode or an additional diode placed in parallel, their conduction can be done naturally with regard to the sign of the current. Switches K5, K8 were already closed. At time instant t3b, switches Ki and K4 close or become conducting.

[0178] Those skilled in the art will observe that for the four step-down configurations of [Fig.2], the switches K2, K3, K4 can each consist of a simple diode, their closing and opening then taking place naturally.

[0179] The operation of the converter 10 in the example of [Fig.l] is now explained according to the four voltage booster configurations, namely the first booster configuration E1, the second booster configuration E2, the third booster configuration E3 and the fourth booster configuration E4 with respect to [Fig.3] El elevator configuration

[0180] From the time instant to to the time instant tb corresponding to the first phase I, the sign of the current IL leads to an increase in the total piezoelectric voltage Vp. The total piezoelectric voltage Vp therefore changes from the value Vc equal to Vin-Vout to the value Vb equal to -Vin+Vout. Seen from the piezoelectric assemblies 12A, 12B, the application of the value Vb at the time instant ti does not induce a voltage variation at its terminals and from this point of view the closing of the switches at the time instant ti does not induce losses for the piezoelectric assemblies 12A, 12B.

[0181] However, the voltage across the switches is not zero and their closing induces losses specific to the energy stored in their parasitic capacitances, for example their output parasitic capacitance. Indeed, the initial total piezoelectric voltage Vp is equal to Vin-Vout, namely the voltage Vpa equal to Vin and the voltage Vpb equal to -Vout, the sign of the current IL allows an increase in the total piezoelectric voltage Vp and therefore can contribute to the increase in the voltage Vpb, but not to the decrease in the voltage Vpa which must go from +Vin to -Vin. Therefore, at the time instant tb the voltage Vpa is still at +Vin while the voltage Vpb equal to Vp minus the voltage Vpa, i.e. (-Vin +Vout)-Vin equal to Vout-2Vin. Before their closing at the time instant tb the switches K5 and K8 have a potential difference Vin across their terminals, which induces losses when they close.Before their closure at time instant tb, the switches Ki and K4 have a potential difference (Vout minus voltage Vpb) / 2, or (Vout -(Vout-2Vin)) / 2 equal to Vin at their terminals, which induces losses when they close.

[0182] In practice, if switches Ki and K4 have a reverse diode (intrinsic or additional placed in parallel), with regard to the sign of the current IL, switches Ki and K4 do not need to be forced to close, but can close naturally a little later. In this case, the energy stored in their output capacitance will be dissipated in switches K5 and K8. At the common mode level, if the switches Ki and K4 are substantially identical and the switches K5 and K8 are substantially identical, and the switches K5 and K8 are closed substantially at the same time, (the same for the switches Ki and K4 if they are forced to close), then, by symmetry, the current drawn on the potential V inp opposes the current drawn on the potential Vinn, and the same for the potential Voutp and the potential Voutn, and there is no common mode current injected on the output voltage Vout.

[0183] During this first phase I, at substantially constant load, only the switches K6 and K7 are then conducting or controlled in the closed position. During this first phase I, the total piezoelectric voltage Vp increases, which tends to increase the voltages Vpa and Vpb, but since the voltage Vpa is already equal to the value +Vin at the time instant t0, it can no longer increase, which causes a small current to flow through the switches K6 and K7, either because they are closed, or via their intrinsic or additional reverse diodes.

[0184] From the time instant ti to the time instant t2, corresponding to the second phase II, the switches Kb K4, K5 and K8 are on or closed. The total piezoelectric voltage Vp is equal to -Vin+Vout. A positive power is drawn from the input voltage V in at the same time as a positive power is supplied to the output voltage Vout.

[0185] From time instant t2 to time instant t3, corresponding to the third phase III, the sign of the current IL leads to an increase in the total piezoelectric voltage V p. The total piezoelectric voltage Vp therefore changes from -Vin+Vout to +Vin+Vout. Only the voltage Vpa needs to be modified, it must change from -Vin to +Vin, which it does naturally with the increase in the total piezoelectric voltage Vp, while the voltage Vpb remains constant and fixed at +Vout by keeping the switches Ki and K4 closed.

[0186] During this third phase III, at a substantially constant load, only the switches Ki and K4 are then controlled in the closed position.

[0187] At time instant t3, voltage Vpa and voltage Vpb are therefore already repositioned to the values ​​of the next voltage level, and the closing of switches K6, K7 is carried out in ZVS mode.

[0188] From time instant t3 to time instant t4, corresponding to the fourth phase IV, the switches Kb K4, K6 and K7 are closed. The total piezoelectric voltage Vp is equal to Vin+Vout. A positive power is drawn on the input voltage Vin at the same time as a positive power is drawn on the output voltage Vout.

[0189] From time instant t4 to time instant t5, corresponding to the fifth phase V, the sign of the current IL leads to a decrease in the total piezoelectric voltage Vp. The total piezoelectric voltage Vp therefore changes from +Vin+Vout to Vin-Vout. Only the voltage Vpb needs to be modified, and must change from +Vout to -Vout, which it does naturally with the decrease in the total piezoelectric voltage Vp, while the voltage Vpa remains constant and fixed at +Vin via keeping the switches K6 and K7 closed.

[0190] During this fifth phase V, at substantially constant load, only switches K6 and K7 are then controlled in the closed position.

[0191] At time instant t5, voltage Vpa and voltage Vpb are therefore already repositioned to the values ​​of the next voltage level, and the closing of switches K2, K3 is carried out in ZVS mode. If switches K2 and K3 have an intrinsic reverse diode or an additional diode placed in parallel, their conduction can be done naturally with regard to the sign of current IL. Switches K6, K7 were already closed.

[0192] From time instant t5 to time instant t6 (or time instant t0), corresponding to the sixth phase VI, the switches K6, K7, K2 and K3 are on or closed. The total piezoelectric voltage Vp equals Vin-Vout. A positive power is drawn on the input voltage Vin at the same time as a positive power is supplied to the output voltage Vout. E2 elevator configuration

[0193] The second elevator configuration E2 differs from the first elevator configuration El, described previously, only in that it integrates an excursion at V zvs equal to -Vin-Vout at the time instant t0. This voltage excursion allows to pass from total piezoelectric voltage step Vp equal to Vin-Vout to total piezoelectric voltage step Vp equal to -Vin+Vout in ZVS switching at the switches. This transition is done in two stages, a first stage from time instant t5b to time instant t6 (or time instant t0) to go from the total piezoelectric voltage Vp equal to Vin-Vout to the total piezoelectric voltage Vp equal to -Vin-Vout, then a second stage from time instant t0 to time instant ti to go from the total piezoelectric voltage Vp equal to -Vin-Vout to the total piezoelectric voltage Vp equal to -Vin+Vout.

[0194] From time instant t5b to time instant t6 (or time instant t0), the sign of current IL leads to a decrease in the total piezoelectric voltage Vp. The total piezoelectric voltage Vp therefore changes from Vin-Vout to -Vin-Vout. Only voltage Vpa needs to be modified, and must change from Vin to -Vin, which it does naturally with the decrease in total piezoelectric voltage Vp, while voltage Vpb remains constant and fixed at -Vout via maintaining switches K2 and K3 on (either by maintaining a closing command, or naturally via their intrinsic reverse diode, or even via an additional parallel diode). At time instant t6 (or time instant t0), voltage Vpa and voltage Vpb are therefore pre-positioned on -Vin and -Vout respectively, and the closing of switches K5, K8 is carried out in ZVS mode.

[0195] During the first stage of this first phase I, at substantially constant load, only switches K2 and K3 are then passing or controlled in the closed position.

[0196] At time instant t0, switches K5 and K8 close, while switches K2 and K3 open.

[0197] From the time instant to to the time instant tb corresponding to the first phase I, the sign of the current IL leads to an increase in the total piezoelectric voltage Vp. The total piezoelectric voltage Vp therefore changes from -Vin-Vout to -Vin+Vout. Only the voltage Vpb needs to be modified, and must change from -Vout to +Vout, which it does naturally with the increase in the total piezoelectric voltage Vp, while the voltage Vpa remains constant and fixed at -Vin via keeping the switches K5 and K8 closed.

[0198] During the second stage of this first phase I, at substantially constant load, only switches K5 and K8 are then controlled in the closed position.

[0199] At the time instant tb the voltage Vpa and the voltage Vpb are therefore already repositioned on the values ​​of the next voltage level, and the closing of the switches Kb K4 is carried out in ZVS mode. If the switches Ki and K4 have an intrinsic reverse diode or an additional diode placed in parallel, their conduction can be done naturally with regard to the sign of the current. The switches K5, K8 were already closed.

[0200] At time instant tb the switches Ki and K4 close or become conducting. E3 elevator configuration

[0201] From the time instant to to the time instant tb corresponding to the first phase I, the sign of the current IL leads to a decrease in the total piezoelectric voltage Vp. The total piezoelectric voltage Vp therefore changes from the value Vc equal to -Vin+Vout to the value Vb equal to Vin-Vout. Seen from the piezoelectric assemblies 12A, 12B, the application of the value Vb at the time instant ti does not induce a voltage variation at its terminals and from this point of view the closing of the switches at the time instant ti does not induce losses for the piezoelectric assemblies 12A, 12B.

[0202] However, the voltage across the switches is not zero and their closure induces losses specific to the energy stored in their parasitic capacitances, for example their output parasitic capacitance. Indeed, the initial total piezoelectric voltage Vp is equal to -Vin+Vout, the voltage Vpa being equal to -Vin and the voltage Vpb being equal to +Vout, and the sign of the current IL allows a decrease in the total piezoelectric voltage Vp, contributing to the decrease in the voltage Vpb, but not to the increase in the voltage V pa which must go from -Vin to +Vin. Therefore, at the time instant tb the voltage Vpa is still at -Vin while the voltage Vpb equal to Vp minus the voltage Vpa equal to (Vin-Vout)-(-Vin), i.e. 2Vin-Vout.

[0203] Before their closure at time instant tb, switches K6 and K7 have a potential difference Vin across their terminals, which induces losses when they close. Before their closure at time instant tb, switches K2 and K3 have a potential difference (Vout plus voltage Vpb) / 2, i.e. (Vout+(2Vin-Vout)) / 2 = Vin across their terminals, which induces losses when they close.

[0204] In practice, if switches K2 and K3 have a reverse diode (intrinsic or additional placed in parallel), with regard to the sign of the current IL. Switches K2 and K3 do not need to be forced to close, but can close naturally a little later. In this case, the energy stored in their output capacitance will be dissipated in switches K6 and K7 when they close.

[0205] At the common mode level, if the switches K2 and K3 are substantially identical, and the switches K6 and K7 are substantially identical, and the switches K6 and K7 are closed substantially at the same time, (the same applies to the switches K2 and K3 if they are forced to close), then, due to symmetry, the current drawn on the potential Vinp opposes the current drawn on the potential Vinn, and the same applies to the potential Voutp and the potential Voutn, so that there is no common mode current injected into the output voltage Vout.

[0206] During this first phase I, at a substantially constant load, only the switches K5 and K8 are then on or controlled in the closed position. During this first phase I, the total piezoelectric voltage Vp decreases, which tends to make decrease the voltages Vpa and Vpb, but since the voltage Vpa is already equal to the value -Vin at the time instant t0, it can no longer decrease, which causes a small current to flow through the switches K5 and K8, either because they are closed, or via their intrinsic or additional reverse diodes.

[0207] From time instant ti to time instant t2, corresponding to the second phase II, the switches K2, K3, K6 and K7 are on or closed. The total piezoelectric voltage Vp is equal to Vin-Vout. A positive power is drawn from the input voltage Vin at the same time as a positive power is supplied to the output voltage Vout.

[0208] From time instant t2 to time instant t3, corresponding to the third phase III, the sign of the current IL leads to a decrease in the total piezoelectric voltage Vp. The total piezoelectric voltage Vp therefore changes from Vin-Vout to -Vin-Vout. Only the voltage Vpa needs to be modified, and must change from +Vin to -Vin, which it does naturally with the decrease in the total piezoelectric voltage Vp, while the voltage Vpb remains constant and fixed at -Vout via keeping the switches K2 and K3 closed or passing.

[0209] During this third phase III, at a substantially constant load, only switches K2 and K3 are then passing or controlled in the closed position.

[0210] At time instant t3, voltage Vpa and voltage Vpb are therefore already repositioned to the values ​​of the next voltage level, and the closing of switches K5, K8 is carried out in ZVS mode.

[0211] From time instant t3 to time instant t4, corresponding to the fourth phase IV, the switches K2, K3, K5 and K8 are on or closed. The total piezoelectric voltage Vp is equal to -Vin-Vout. A positive power is drawn on the input voltage Vin at the same time as a positive power is also drawn on the output voltage Vout.

[0212] From time instant t4 to time instant t5, corresponding to the fifth phase V, the sign of the current IL leads to an increase in the total piezoelectric voltage V p. The total piezoelectric voltage Vp therefore changes from -Vin-Vout to -Vin+Vout. Only the voltage Vpb needs to be modified, and must change from -Vout to +Vout, which it does naturally with the increase in the total piezoelectric voltage Vp, while the voltage Vpa remains constant and fixed at -Vin via keeping the switches K5 and K8 closed.

[0213] During this fifth phase V, at substantially constant load, only switches K5 and K8 are then controlled in the closed position.

[0214] At the time instant t5, the voltage Vpa and the voltage Vpb are therefore already repositioned on the values ​​of the next voltage level, and the closing of the switches Kb K4 is carried out in ZVS mode. If the switches Ki and K4 have an intrinsic reverse diode or an additional diode placed in parallel, their conduction can be done naturally with regard to the sign of the current. Switches K5, K8 were already closed.

[0215] From time instant t5 to time instant t6 (or time instant t0), corresponding to the sixth phase VI, the switches K4, K5 and K8 are on or closed. The total piezoelectric voltage Vp equals -Vin+Vout. A positive power is drawn on the input voltage Vin at the same time as a positive power is supplied to the output voltage Vout. E4 elevator configuration

[0216] The fourth booster configuration E4 differs from the third booster configuration E3, described previously, only in that it integrates an excursion at V zvs equal to +Vin+Vout at the time instant t0. This voltage excursion makes it possible to move from the total piezoelectric voltage level Vp equal to -Vin+Vout to the total piezoelectric voltage level Vp equal to Vin-Vout in ZVS switching at the switches. This transition is done in two stages, a first stage from time instant t5b to time instant L (or time instant to) to pass from the total piezoelectric voltage Vp equal to -Vin+Vout to the total piezoelectric voltage Vp equal to +Vin +Vout, then a second stage from time instant t0 to time instant ti to pass from the total piezoelectric voltage Vp equal to Vin+Vout to the total piezoelectric voltage Vp equal to Vin+Vout.

[0217] From time instant t5b to time instant t6 (or time instant to), the sign of current IL leads to an increase in the total piezoelectric voltage Vp. The total piezoelectric voltage Vp therefore changes from -Vin+Vout to Vin+Vout. Only voltage V pa needs to be modified, and must change from -Vin to Vin, which it does naturally with the increase in total piezoelectric voltage Vp, while voltage Vpb remains constant and fixed at Vout via keeping switches Ki and K4 on (either by maintaining a closing command, or naturally via their intrinsic reverse diode, or via an additional parallel diode).

[0218] During the first stage of this first phase I, at substantially constant load, only the switches Ki and K4 are then controlled in the closed position.

[0219] At time instant t6 (or time instant t0), voltage Vpa and voltage Vpb are therefore pre-positioned on Vin and Vout respectively, and the closing of switches K6, K7 is carried out in ZVS mode. At time instant t0, switches K6 and K7 close, while switches Ki and K4 open.

[0220] From the time instant to to the time instant tb corresponding to the second step of the first phase I, the sign of the current IL leads to a decrease in the total piezoelectric voltage Vp. The total piezoelectric voltage Vp therefore changes from Vin+Vout to Vin-V out. Only the voltage Vpb needs to be modified, and must change from Vout to -Vout, which it does naturally with the decrease in the total piezoelectric voltage Vp, while the voltage Vpa remains constant and fixed at +Vin by keeping the switches K6 and K7 closed.

[0221] During the second stage of this first phase I, at substantially constant load, only switches K6 and K7 are then controlled in the closed position.

[0222] At time instant tb, voltage Vpa and voltage Vpb are therefore already repositioned to the values ​​of the next voltage level, and the closing of switches K2, K3 is carried out in ZVS mode. If switches K2 and K3 have an intrinsic reverse diode or an additional diode placed in parallel, their conduction can be done naturally with regard to the sign of the current. Switches K6, K7 were already closed. At time instant tb, switches K2 and K3 close or become conducting.

[0223] Those skilled in the art will observe that for the first and second step-up configurations E1 and E2 of [Fig. 3], the switches K2 and K3 may be simple diodes that open and close naturally. Similarly, for the third and fourth step-up configurations E3 and E4 of [Fig. 3], the switches Ki and K4 may be simple diodes that open and close naturally.

[0224] As an optional addition, in the examples of Figures 5 to 9, the converter 10 further comprises at least one switching assistance circuit 50, each switching assistance circuit 50 being connected to a respective midpoint among the first 38 and second 48 midpoints, each switching assistance circuit 50 being configured to, via the flow of a previously received current, discharge a parasitic capacitance of at least one switch 36, 46 of the respective switching bridge 30, 40 to which it is connected, and respectively charge at least one parasitic capacitance of another switch 36, 46 of said switching bridge 30, 40.

[0225] In the examples of Figures 5 and 8, the converter 10 comprises a single switching assistance circuit 50 connected to the first switching bridge 30 or to the second switching bridge 40. In the example of [Fig.5], the single switching assistance circuit 50 is connected to the second switching bridge 40. In the example of [Fig.8], the single switching assistance circuit 50 is connected to the first switching bridge 30.

[0226] In the examples of Figures 5 and 8, the second switching bridge 40 comprises two second switching branches 42, respectively the first switching bridge 30 comprises two first switching branches 32; and the switching assistance circuit 50 is then connected between the respective midpoints 38, 48 of the two switching branches 32, 42 of said bridge 30, 40. In the example of [Fig.5], the switching assistance circuit 50 is then connected between the second midpoints 48 of the two second switching branches 42 of the second switching bridge 40. Similarly, in the example of [Fig.8], the circuit switching aid 50 is then connected between the first midpoints 38 of the first two switching branches 32 of the first switching bridge 30.

[0227] As a variant, not shown, the converter 10 comprises two switching assistance circuits 50, a first switching assistance circuit being connected to the first switching bridge 30 and a second switching assistance circuit being connected to the second switching bridge 40.

[0228] According to this variant, those skilled in the art will understand that each switching assistance circuit 50 is capable of being connected between the respective midpoints 38, 48 of the two switching branches 32, 42.

[0229] Each switching assistance circuit 50 is configured, via the circulation of a previously received current ICalc, to discharge at least one parasitic capacitance of a switch 36, 46, preferably a switch to be closed, of the respective switching bridge 30, 40 to which it is connected; respectively to charge at least one parasitic capacitance of another switch 36, 46, preferably a switch to be opened or kept open, of said switching bridge 30, 40.

[0230] Each of the switches of said switching bridge 30 is open during the circulation, by the switching assistance circuit 50, of the previously received current.

[0231] Following this current flow, the switch(es) 36, 46 whose parasitic capacitance has been discharged by the switching assistance circuit 50 is / are closed. The other switch(es) 36, 46 whose parasitic capacitance has been charged by the switching assistance circuit 50 remains open.

[0232] Each switching assistance circuit 50 comprises for example an inductance 70; or a first assembly formed of the inductance 70 and a diode 72 connected in series; or a second assembly formed of the inductance 70 and a capacitor 74 connected in series; or even an additional piezoelectric element 76, as shown in [Fig.6].

[0233] Each switching assistance circuit 50 is for example an inductor 70, the inductor 70 preferably consisting of a coil and a magnetic circuit. Alternatively, each switching assistance circuit 50 is in the form of the first set of the inductor 70 and the diode 72 connected in series, and preferably consisting of said first set of the inductor 70 and the diode 72. As a further alternative, each switching assistance circuit 50 is in the form of the second set of the inductor 70 and the capacitor 74 connected in series, and preferably consisting of said second set of the inductor 70 and the capacitor 74. As a further alternative, each switching assistance circuit 50 is in the form of the additional piezoelectric element 76, and preferably consisting of the additional piezoelectric element 76.

[0234] In the embodiment where the switching assistance circuit 50 is in the form of the inductor 70 alone, the inductor 70 sees its current increase over a half-period, i.e. when the voltage across its terminals is positive; then its current decreases over the other half-period, i.e. when the voltage across its terminals is negative. This example embodiment of the switching assistance circuit 50 preferably requires that the voltage across the inductor 70 be substantially zero on average, otherwise there is a risk of having a current drift. If the switching assistance circuit 50 is connected to the second bridge 40, in particular between the second midpoints 48, the voltage across the inductor 70 is the voltage Vpb. Corollarily, if the switching assistance circuit 50 is connected to the first bridge 30, in particular between the first midpoints 38, the voltage across the inductor 70 is the voltage Vpa.

[0235] The variant where the switching assistance circuit 50 is in the form of the inductor 70 and the diode 72 connected in series, makes it possible to charge the inductor 70 only over a half-period with the correct polarity, in particular for cycles where the current ICalc is received during a time period with a single polarity, for example between the time instants t2 and t3 for the step-down cycles A1_C and A3_C described below (positive polarity of the current Icalc for the step-down cycle A1_C between the time instants t2 and t3, negative polarity for the step-down cycle A3_C between these time instants t2 and t3). In particular, the diode 72 then makes it possible to avoid charging the inductance 70 with a reverse current between the time instants t3 and T. This unidirectional current operation also makes it possible to reduce the effective current seen by the inductance 70 and therefore the losses.Furthermore, the switching assistance circuit 50 according to this variant is not sensitive to the presence of a DC component from the moment when the DC component is in the direction of blocking the diode 72.

[0236] The variant where the switching assistance circuit 50 is in the form of the inductor 70 and the capacitor 74 connected in series, makes it possible - compared to the example of the inductor 70 alone - to reduce, or even eliminate, a possible DC component. Nevertheless, the capacitor 74 can be quite large. Indeed, the voltage across the capacitor 74 must change little, i.e. in a small proportion, compared to the input voltage Vin or the output voltage Vout, for example have an amplitude less than 50% of the input voltage Vin or output voltage Vout.

[0237] According to the variant where the switching assistance circuit 50 is in the form of the additional piezoelectric element 76, from the moment when the control of the converter 10 is carried out between the resonance and antiresonance frequency of the additional piezoelectric element 76, the latter begins to oscillate and to produce a current Icalc substantially in quadrature with the voltage at its terminals, such as the voltage Vpb if the additional piezoelectric element 76 is connected to the second bridge 40 between the second midpoints 48, or the voltage Vpa if the piezoelectric element ad Additional 76 is connected to the first bridge 30 between the first midpoints 38. The current ICalc then passes through an extrema around the time instant t3 for the step-down cycles A1_C and A3_C, which makes it possible to ensure the function of inverting the voltage Vpb between the time instants t2 and t3; or similarly around the time instant t0 for the step-up cycles E1_C and E3_C described below with regard to [Fig.9], which makes it possible to ensure the function of inverting the voltage Vpa between the time instants t0 and tb

[0238] The additional piezoelectric element 76 is typically at least 3 times smaller than the piezoelectric element(s) 15 of the converter 10, the additional piezoelectric element 76 only having to charge / discharge the parasitic capacitances of the switches 36, 46. The parasitic capacitance of the switches 36, 46 is in fact considered to be at least three times lower than the reference capacitance Co of the piezoelectric element(s) 15 of the converter 10. This variant where the switching assistance circuit 50 is in the form of the additional piezoelectric element 76 is insensitive to a possible DC component (whatever its polarity), and the switching assistance circuit 50 is able to be connected both to the first bridge 30 (voltage Vpa) and to the second bridge 40 (voltage Vpb).

[0239] In other words, the reference capacitance of the additional piezoelectric element 76 is at least three times lower than the reference capacitance Co of each piezoelectric assembly 12 connected between the first 38 and second 48 respective midpoints.

[0240] The operation of the converter 10 in the example of [Fig.5] will now be explained according to two voltage step-down configurations, namely a first step-down configuration A1_C and a second step-down configuration A3_C with respect to [Fig.7]. The difference resulting from the switching assistance circuit 50 according to the complementary aspect relates to the changes in the voltages Vpa and Vpb between the time instants t2 and t3 in the case of these step-down configurations A1_C, A3_C, and more particularly to the zones represented in dotted lines in [Fig.7], this to mark the difference.

[0241] The conversion cycle of the converter 10 according to the complementary aspect is described below for the first A1_C and second A3_C step-down configurations, focusing on the differences compared to the conversion cycle of the converter 10 of [Fig.l] for the same step-down configurations A1 and A3.

[0242] For the first step-down configuration A1_C, between the time instants ti and t2, according to the exemplary embodiment of the switching assistance circuit 50, the inductance 70 or the additional piezoelectric element 76 sees its current Icalc increase, this under the voltage Vpb equal to +Vout. At the time instant t2, the current Icalc is positive.

[0243] Just before the time instant t2, the total piezoelectric voltage Vp is equal to -Vin +Vout, the voltage Vpa being equal to -Vin, and the voltage Vpb being equal to +Vout; and the switches K5, K8, Ki, K4 are closed.

[0244] At time instant t2, all the switches that were closed open. The current ICalc then charges the parasitic capacitances of the switches K4, while it discharges the parasitic capacitances of the switches K2 and K3. Similarly, through the piezoelectric assemblies 12 whose voltage changes slowly, the current ICalc partially charges the parasitic capacitances of the switches K5, K8, while it partially discharges the parasitic capacitances of the switches K6, K7. The voltage Vpb thus changes from +Vout to -Vout, while the voltage Vpa changes substantially from -Vin to -Vin+2Vout plus the change in the total piezoelectric voltage Vp since time instant t2.

[0245] The voltage inversion Vpb is considered to be completed before the total piezoelectric voltage Vp reaches the next level Va. Indeed, even if the amplitude of the current ICalc in the switching assistance circuit 50 is much lower than the amplitude of the internal current IL of the piezoelectric elements 15 (for example at least 3 times lower to limit its size), the latter nevertheless only has to charge / discharge the parasitic capacitances of the switches 36, 46 considered to be much lower than the reference capacitance Co of the piezoelectric elements 15 (at least a factor of 3). Furthermore, the current Icalc in the switching assistance circuit 50 approaches its maximum value at the time instant t3, while the internal current IL approaches 0 at said time instant t3.

[0246] Once the complete inversion of the voltage Vpb is reached (transition from Vout to -Vout), then the switches K2 and K3 are closed so as to freeze the voltage Vpb, while the voltage Vpa continues its progression up to Vin under the effect of the natural increase in the total piezoelectric voltage Vp.

[0247] At time instant t3, switches K6 and K7 are closed. Switches K2 and K3 are also closed if this had not already been done before, i.e. if voltage Vpb had not yet reached -Vout.

[0248] In addition, if the switches K2 and K3 include an intrinsic reverse diode or an additional diode placed in parallel, their conduction can occur naturally with respect to the sign of the internal current IL after the time instant t 3, or with respect to the residual current Icalc before the time instant t3.

[0249] The remainder of the conversion cycle of the converter 10 according to the complementary aspect remains substantially unchanged compared to the conversion cycle of the converter 10 of [Fig.l],

[0250] The voltage excursion of the total piezoelectric voltage Vp is thus limited between the time instants t2 and t4, this going from -Vin+Vout to Vin-Vout, instead of going from -V in+Vout to +Vin+Vout with the converter 10 of [Fig.l] (in the case of the step-down configuration A2 to ensure switching of the switches 36, 46 to zero of voltage), or an excursion of 2Vin-2Vout instead of 2Vin, while ensuring switching of switches 36, 46 at zero voltage.

[0251] For the second step-down configuration A3_C, between the time instants ti and t2, according to the exemplary embodiment of the switching assistance circuit 50, the inductance 70 or the additional piezoelectric element 76 sees its current ICalc decrease, this under the voltage Vpb equal to -Vout. At the time instant t2, the current ICalc is negative.

[0252] Just before the time instant t2, the total piezoelectric voltage Vp is equal to Vin-V out, the voltage Vpa being equal to Vin, and the voltage Vpb being equal to -Vout; and the switches K6, K7, K2, K3 are closed.

[0253] At time instant t2, all the switches that were closed open. The current ICalc then charges the parasitic capacitances of the switches K2, K3, while it discharges the parasitic capacitances of the switches Ki and K4. Similarly, through the piezoelectric assemblies 12 whose voltage changes slowly, the current ICalc partially charges the parasitic capacitances of the switches K6, K7, while it partially discharges the parasitic capacitances of the switches K5, K8. The voltage Vpb thus changes from -Vout to +Vout, while the voltage Vpa changes substantially from +Vin to +Vin-2Vout plus the change in the total piezoelectric voltage Vp since time instant t2.

[0254] The voltage inversion Vpb is considered to be completed before the total piezoelectric voltage Vp reaches the next level Va. Indeed, even if the amplitude of the current Icalc in the switching assistance circuit 50 is much lower than the amplitude of the internal current IL of the piezoelectric elements 15 (for example at least 3 times lower to limit its size), the latter nevertheless only has to charge / discharge the parasitic capacitances of the switches 36, 46 considered to be much lower than the reference capacitance Co of the piezoelectric elements 15 (at least a factor of 3). Furthermore, the current Icalc in the switching assistance circuit 50 approaches its minimum value (its negative extremum) at the time instant t3, while the internal current IL approaches 0 at said time instant t3.

[0255] Once the complete inversion of the voltage Vpb is reached (transition from -Vout to +Vout), then the switches Ki and K4 are closed so as to freeze the voltage Vpb, while the voltage Vpa continues its progression until -Vin under the effect of the natural decrease in the total piezoelectric voltage Vp.

[0256] At time instant t3, switches K5 and K8 are closed. Switches Ki and K4 are also closed if this had not already been done before, i.e. if voltage Vpb had not yet reached +Vout.

[0257] In addition, if the switches Ki and K4 include an intrinsic reverse diode or an additional diode placed in parallel, their conduction can occur naturally with respect to the sign of the internal current IL after the time instant t 3, or with respect to the residual current Icalc before the time instant t3.

[0258] The remainder of the conversion cycle of converter 10 of [Fig.5] remains substantially unchanged from the conversion cycle of converter 10 of [Fig.l].

[0259] Here again, the voltage excursion of the total piezoelectric voltage Vp is thus limited between the time instants t2 and t4, this going from Vin-Vout to Vout-Vin, instead of going from Vin-Vout to -Vin-Vout with the converter 10 of [Fig.l] (in the case of the step-down configuration A4 to ensure switching of the switches 36, 46 at zero voltage), i.e. an excursion of 2Vin-2Vout instead of 2Vin, while ensuring switching of the switches 36, 46 at zero voltage.

[0260] Figures 8 and 9 illustrate an alternative embodiment of the converter 10 for which the switching assistance circuit 50 is connected to the first switching bridge 30, for example between the first midpoints 38 of the two first switching branches 32.

[0261] According to this alternative embodiment of the converter 10, the difference compared to the exemplary embodiment of FIGS. 5 and 7, described previously, is that the switching assistance circuit 50 is then connected to the first switching bridge 30 instead of being connected to the second switching bridge 40 according to the exemplary embodiment of FIGS. 5 and 7. The other elements which are unchanged between the exemplary embodiment of FIGS. 5 and 7, and this variant of FIGS. 8 and 9 are repeated with identical references.

[0262] The operation of the converter 10 in the example of [Fig.8] will now be explained according to two voltage booster configurations, namely a first booster configuration E1_C and a second booster configuration E3_C with respect to [Fig.9]. The difference resulting from the switching assistance circuit 50 according to this complementary aspect relates to the changes in the voltages Vpa and Vpb between the time instants t0 and ti in the case of these booster configurations E1_C, E3_C, and more particularly to the zones represented in dotted lines in [Fig.9], this to mark the difference.

[0263] The conversion cycle of the converter 10 according to this complementary aspect is described below for the first E1_C and second E3_C step-up configurations, focusing on the differences compared to the conversion cycle of the converter 10 of [Fig.l] for the same step-up configurations.

[0264] For the step-down configurations A1_C and A3_C, described previously, it was the voltage Vpb which had a homogeneous polarity over each of the two half-periods with a polarity inversion between the two half-periods, and it was then preferable to arrange the switching assistance circuit 50 on the side of the voltage Vpb, i.e. connected to the second switching bridge 40, between the respective second midpoints 48.

[0265] This time, for these E1_C and E3_C booster configurations, it is the voltage Vpa which has a homogeneous polarity on each of the two half-periods with a polarity inversion between the two half-periods (same polarity on the Va and Vc steps and opposite polarity on the Vb step). For these step-up configurations E1_C and E3_C, it is therefore preferable to arrange the switching assistance circuit 50 on the Vpa voltage side, i.e. connected to the first switching bridge 30, between the respective first midpoints 38. This arrangement of the switching assistance circuit 50 on the Vpa voltage side is preferable except in the case where the switching assistance circuit 50 is in the form of the inductor 70 and the diode 72 connected in series, where the arrangement on the Vpb voltage side (i.e. connected to the second switching bridge 40, between the respective second midpoints 48) remains preferable so that the possible DC component does not make the diode 72 conductive.

[0266] For the first booster configuration E1_C, between the time instants t3 and T (or to), according to the embodiment of the switching assistance circuit 50, the inductance 70 or the additional piezoelectric element 76 sees its current ICalc increase, this under the voltage Vpa equal to +Vin. At the time instant T (or to), the current Icalc is positive.

[0267] Just before the time instant to, the total piezoelectric voltage Vp is equal to Vin-V out, the voltage Vpa being equal to Vin, and the voltage Vpb being equal to -Vout; and the switches K6, K7, K2, K3 are closed.

[0268] At the time instant to, all the switches that were closed open. The current Icalc then charges the parasitic capacitances of the switches K6, K7, while it discharges the parasitic capacitances of the switches K5, K8. Similarly, through the piezoelectric assemblies 12A, 12B, whose voltage changes slowly, the current Icalc partially charges the parasitic capacitances of the switches K2, K3, while it partially discharges the parasitic capacitances of the switches Kh K4. The voltage Vpa thus changes from +Vin to -Vin, while the voltage Vpb changes substantially from -Vout to -Vout+2Vin plus the change in the total piezoelectric voltage Vp since the time instant t0.

[0269] The voltage inversion Vpa is considered to be completed before the total piezoelectric voltage Vp reaches the next level Vb. Indeed, even if the amplitude of the current Icalc in the switching assistance circuit 50 is much lower than the amplitude of the internal current IL of the piezoelectric elements 15 (for example at least 3 times lower to limit its size), the latter nevertheless only has to charge / discharge the parasitic capacitances of the switches 36, 46 considered to be much lower than the reference capacitance Co of the piezoelectric elements 15 (at least a factor of 3). Furthermore, the current Icalc in the switching assistance circuit 50 approaches its maximum value at the time instant to, while the internal current IL approaches 0 at said time instant to.

[0270] Once the complete inversion of the voltage Vpa is reached (transition from Vin to -Vin), then the switches K5 and K8 are closed so as to freeze the voltage Vpa, while the voltage Vpb continues its progression up to Vout under the effect of the natural increase in the total piezoelectric voltage Vp.

[0271] At time instant tb, switches Ki and K4 are closed. Switches K5 and K8 are also closed if this had not already been done before, i.e. if voltage Vpa had not yet reached -Vin.

[0272] In addition, if the switches Ki and K4 include an intrinsic reverse diode or an additional diode placed in parallel, their conduction can occur naturally with regard to the sign of the internal current IL after the time instant t o-

[0273] The remainder of the conversion cycle of the converter 10 according to this complementary aspect remains substantially unchanged compared to the conversion cycle of the converter 10 of [Fig.l],

[0274] The voltage excursion of the total piezoelectric voltage Vp is thus limited between the time instants t5 and tb, the latter going from Vin-Vout to Vout-Vin, instead of going from -Vin -Vout to Vout-Vin with the converter 10 of [Fig.l] (in the case of the step-up configuration E2 to ensure switching of the switches 36, 46 at zero voltage), i.e. an excursion of 2Vout-2Vin instead of 2Vout, while ensuring switching of the switches 36, 46 at zero voltage.

[0275] For the second booster configuration E3_C, between the time instants t3 and T (or to), according to the embodiment of the switching assistance circuit 50, the inductance 70 or the additional piezoelectric element 76 sees its current ICalc decrease, this under the voltage Vpa equal to -Vin. At the time instant T (or t0), the current ICalc is negative.

[0276] Just before the time instant t0, the total piezoelectric voltage Vp is equal to -Vin +Vout, the voltage Vpa being equal to -Vin, and the voltage Vpb being equal to +Vout; and the switches K5, K8, Ki, K4 are closed.

[0277] At time instant t0, all the switches that were closed open. The current ICalc then charges the parasitic capacitances of the switches K5, K8, while it discharges the parasitic capacitances of the switches K6, K7. Similarly, through the piezoelectric assemblies 12 whose voltage changes slowly, the current ICalc partially charges the parasitic capacitances of the switches Kb K4, while it partially discharges the parasitic capacitances of the switches K2, K3. The voltage Vpa thus changes from -Vin to +Vin, while the voltage Vpb changes substantially from Vout to Vout-2Vin plus the change in the total piezoelectric voltage Vp since time instant to.

[0278] The voltage inversion Vpa is considered complete before the total piezoelectric voltage Vp reaches the next level Vb. Indeed, even if the amplitude of the current ICalc in the switching assistance circuit 50 is much lower than the amplitude of the internal current IL of the piezoelectric elements 15 (for example at least 3 times lower to limit its size), the latter nevertheless only has to charge / discharge the parasitic capacitances of the switches 36, 46 considered much lower than the reference capacitance Co of the piezoelectric elements 15 (at least a factor of 3). Furthermore, the current ICalc in the switching assistance circuit 50 approaches its minimum value (its negative extremum) at the time instant to, while the internal current IL approaches 0 at said time instant t0.

[0279] Once the complete inversion of the voltage Vpa is reached (transition from -Vin to +Vin), then the switches K6 and K7 are closed so as to freeze the voltage Vpa, while the voltage Vpb continues its progression up to -Vout under the effect of the natural decrease in the total piezoelectric voltage Vp.

[0280] At time instant tb, switches K2 and K3 are closed. Switches K6 and K7 are also closed if this had not already been done before, i.e. if voltage Vpa had not yet reached +Vin.

[0281] In addition, if the switches K2 and K3 include an intrinsic reverse diode or an additional diode placed in parallel, their conduction can occur naturally with regard to the sign of the internal current IL after the time instant t o-

[0282] The remainder of the conversion cycle of the converter 10 according to this complementary aspect remains substantially unchanged compared to the conversion cycle of the converter 10 of [Fig.l],

[0283] Here too, the voltage excursion of the total piezoelectric voltage Vp is thus limited between the time instants t5 and tb, this going from Vout-Vin to Vin-Vout, instead of going from +Vin+Vout to Vin-Vout with the converter 10 of [Fig.l] (in the case of the step-up configuration E4 to ensure switching of the switches 36, 46 at zero voltage), i.e. an excursion of 2Vout-2Vin instead of 2Vout, while ensuring switching of the switches 36, 46 at zero voltage.

[0284] As an optional addition, when the converter 10 comprises two switching assistance circuits 50, with the first switching assistance circuit connected to the first switching bridge 30 and the second switching assistance circuit connected to the second switching bridge 40, the switching assistance circuits 50 then being arranged both on the voltage Vpa side and on the voltage Vpb side, the effects of the two switching assistance circuits 50 are added together. It is just necessary to choose the switching assistance circuits 50 according to the presence or absence of a DC component, and possibly according to the sign of this DC component if there is one.

[0285] Alternatively, the switches Kb K2, K3 and K4 are simple diodes, and the inter- K5, K6, K7 and K8 breakers are single-way voltage switches.

[0286] It is thus understood that the electrical energy converter 10 according to this complementary aspect offers even further improved control by means of the switching assistance circuit 50.

Claims

Claims

1. Electronic device (20) for controlling an electrical energy converter (10) capable of converting an input voltage (Vin) into at least one output voltage (Vout), the converter (10) comprising a first switching bridge (30) comprising two first switching branches (32), each first switching branch (32) being connected between two terminals (34) for applying the input voltage (V in) and comprising at least two first switches (36) connected in series and connected together at a first midpoint (38); at least one second switching bridge (40) comprising two second switching branches (42), each second switching branch (42) being connected between two terminals (44) for supplying the output voltage (Vout) and comprising at least two second switches (46) connected in series and connected together at a second midpoint (48);at least one pair of first (12A) and second (12B) piezoelectric assemblies, each piezoelectric assembly (12A, 12B) comprising at least one piezoelectric element (15) and being connected between respective first (38) and second (48) midpoints, the midpoints (38, 48) between which the piezoelectric assemblies (12A, 12B) are connected being distinct from one piezoelectric assembly (12A) to the other (12B); the electronic control device (20) is configured to control, during a respective resonance cycle of the piezoelectric assemblies (12A, 12B), a switching of each of the switches (36, 46) to alternate phases (II, IV, VI) at substantially constant voltage across the terminals of the piezoelectric assemblies (12A, 12B) and phases (I, III, V) at substantially constant charge across the terminals of said piezoelectric assemblies (12A, 12B), characterized in that the electronic control device (20) is configured to, during each phase (I, III, V) at substantially constant charge, control in the closed position at the same time at most one respective switch among the switches (36A, 46A) connected directly to the first piezoelectric assembly (12A) and at most one respective switch among the switches (36B, 46B) connected directly to the second piezoelectric assembly (12B), and in the open position all the other switches (36,46) of the first and second switching branches (32, 42).,

2. Device (20) according to claim 1, in which the value (Va, Vb, Vc) of the voltage of each of the phases (II, IV, VI) at substantially constant voltage is distinct from the zero value.

3. Device (20) according to claim 2, in which the value (Va, Vb, Vc) of the voltage of each of the phases (II, IV, VI) at substantially constant voltage is chosen from the group consisting of: difference (Vin - V out) between the value of the input voltage (Vin) and that of the output voltage (Vout); difference (Vout - Vin) between the value of the output voltage (Vout) and that of the input voltage (Vin); sum (Vin + Vout) of the values of the input (Vin) and output (Vout) voltages; and opposite of the sum (-Vin -Vout) of the values of the input (Vin) and output (V

4. out / * Device (20) according to any one of the preceding claims, in which the number of phases (II, IV, VI) at substantially constant voltage during a respective resonance cycle is greater than or equal to 3; the number of phases (II, IV, VI) at substantially constant voltage during a respective resonance cycle being preferably equal to 3.

5. Electronic electrical energy conversion system (5) comprising: - an electrical energy converter (10) capable of converting an input voltage (Vin) into at least one output voltage (Vout), and comprising: + a first switching bridge (30) comprising two first switching branches (32), each first switching branch (32) being connected between two terminals (34) for applying the input voltage (Vin) and comprising at least two first switches (36) connected in series and connected together at a first midpoint (38); + at least one second switching bridge (40) comprising two second switching branches (42), each second switching branch (42) being connected between two terminals (44) for supplying the output voltage (Vout) and comprising at least two second switches (46) connected in series and connected together at a second midpoint (48);+ at least one pair of first (12A) and second (12B) piezoelectric assemblies, each piezoelectric assembly (12A, 12B) comprising at least one piezoelectric element (15) and being connected between respective first (38) and second (48) midpoints, the; midpoints (38, 48) between which the piezoelectric assemblies (12A, 12B) are connected, being distinct from one piezoelectric assembly (12A) to the other (12B); and - an electronic device (20) for controlling the electrical energy converter (10); characterized in that the control device (20) is according to any one of the preceding claims.

6. System (5) according to claim 5, wherein the electronic electrical energy conversion system (5) is a system for converting into direct electrical energy, such as a direct-direct conversion system or an alternating-direct conversion system.

7. System (5) according to claim 5 or 6, in which the electrical energy converter (10) is capable of converting the input voltage (Vin) into several distinct output voltages (Voutj), and comprises for each respective output voltage (Voutj): + a respective second switching bridge (40), each second switching branch (42) being connected between two terminals (44) for supplying the respective output voltage (Voutj); + a respective pair of first (12A) and second (12B) piezoelectric assemblies.

8. A system (5) according to any one of claims 5 to 7, wherein each piezoelectric assembly (12A, 12B) is constituted according to one of the constitutions among the group consisting of: a single piezoelectric element (15); a plurality of piezoelectric elements (15) connected in series; a plurality of piezoelectric elements (15) connected in parallel; a piezoelectric element (15) and an auxiliary capacitor connected in series; a piezoelectric element (15) and an auxiliary capacitor connected in parallel; and an arrangement of a plurality of parallel piezoelectric branches, each branch comprising one or more piezoelectric elements (15) connected in series or an auxiliary capacitor;the auxiliary capacitor preferably having a higher capacity, more preferably at least three times higher, than a reference capacity (Co) of the piezoelectric element(s) (15), each piezoelectric element (15) being modeled in the form of a capacitor (52) and a resonant branch (54) connected in parallel with the capacitor (52), the reference capacity (Co) being the capacity of said capacitor; (52).

9. System (5) according to any one of claims 5 to 8, wherein the converter (10) further comprises at least one switching assistance circuit (50), each switching assistance circuit (50) being connected to a respective midpoint among the first (38) and second (48) midpoints, each switching assistance circuit (50) being configured to, via the circulation of a previously received current, discharge a parasitic capacitance of a switch (36; 46) of the respective switching bridge (30; 40) to which it is connected, and respectively charge a parasitic capacitance of another switch (36; 46) of said switching bridge (30; 40).

10. The system (5) of claim 9, wherein the converter (10) comprises two switching aid circuits (50), a first switching aid circuit being connected to the first switching bridge (30) and a second switching aid circuit being connected to the second switching bridge (40).

11. A system (5) according to claim 9 or 10, wherein each switching assistance circuit (50) comprises an element selected from the group consisting of: an electromagnetic coil (70); a first assembly formed of an electromagnetic coil (70) and a diode (72) connected in series; a second assembly formed of an electromagnetic coil (70) and a capacitor (74) connected in series; and an additional piezoelectric element (76); each switching assistance circuit (50) preferably being constituted by an element selected from said group.

12. Method for controlling an electrical energy converter (10) capable of converting an input voltage (Vin) into at least one output voltage (V out), the converter (10) comprising a first switching bridge (30) comprising two first switching branches (32), each first switching branch (32) being connected between two terminals (34) for applying the input voltage (Vin) and comprising at least two first switches (36) connected in series and connected together at a first midpoint (38); at least one second switching bridge (40) comprising two second switching branches (42), each second switching branch (42) being connected between two terminals (44) for supplying the output voltage (V out) and comprising at least two second switches (46) connected in series and connected together at a second midpoint (48); at least a pair of first (12A) and second (12B) piezoelectric assemblies, each piezoelectric assembly (12A, 12B) comprising at least one piezoelectric element (15) and being connected between respective first (38) and second (48) midpoints, the midpoints (38, 48) between which the piezoelectric assemblies (12A, 12B) are connected being distinct from one piezoelectric assembly (12A) to the other (12B); the method being implemented by an electronic control device (20) and comprising the control, during a respective resonance cycle of the piezoelectric assemblies (12A, 12B), of a switching of each of the switches (36, 46) to alternate phases (II, IV, VI) at substantially constant voltage across the terminals of the piezoelectric assemblies (12A, 12B) and phases (I, III, V) at substantially constant charge across said piezoelectric assemblies (12A, 12B), characterized in that, during each phase (I, III, V) at substantially constant charge, at most one respective switch among the switches (36A, 46A) connected directly to the first piezoelectric assembly (12A) and at most one respective switch among the switches (36B, 46B) connected directly to the second piezoelectric assembly (12B) are controlled in the closed position at the same time, and all the other switches (36, 46) of the first and second switching branches (32,42) are controlled in the open position.,

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