Control method for an autonomous electrical supply by means of a piezoelectric converter, a supply circuit and a device supplied thereby

Description

[0001] The present invention as defined by the claims provides a method for controlling a circuit for harvesting electrical energy produced by a piezoelectric transducer, forming a piezoelectric resonator under the effect of vibrations from a mechanical excitation source. This circuit produces a continuous output voltage via a DC-DC converter operating by PWM, which is controlled by a signal controlling its duty cycle with a current value. This method typically comprises: an estimation process including the following operations, during operation of the harvesting circuit: detection of the piezo voltage signal, evaluation of the amplitude of an individual harmonic of said piezo signal, of a rank greater than one, and for example of rank three, estimation of a new equivalent resistance to be produced by the converter, and of a new duty cycle to be controlled for the converter; an impedance adaptation process by applying to the converter a new reference signal to control the new duty cycle and produce the new resistance; a nominal operating process, with a constant value of the converter control signal. State of the art

[0002] There are many devices that include an electrical or electronic part and must operate autonomously for a long time without being connected to an external electrical source, or at least for a longer time than the energy initially stored inside would allow.

[0003] Such devices can be, for example, various types of measuring or detection sensors, with recording or even wireless communication functionalities. They can be mobile or embedded devices, or devices that need to be distributed over large areas, such as radio receivers or environmental sensors. They can also be various types of low-power devices that are implanted in the human or animal body in vivo, where it is difficult to provide them with a charging power connection, such as a pacemaker. Other devices are also concerned, such as wearable devices or smart clothing, or monitoring devices, or positioning beacons.

[0004] For the electrical power supply of such devices, it is known to integrate an energy harvesting device in order to extract electrical energy from a local source of mechanical energy available in an alternative form, for example vibrations or pressure variations in a fluid or repetitive mechanical deformations.

[0005] Such mechanical energy can be harvested by different types of converters, also called transducers. Piezoelectric transducers use forces or strains applied to a material that exhibits piezoelectric properties. This piezoelectric material is integrated into a mechanical resonator that is excited by the mechanical forces of the environment, and it thus converts this mechanical energy into electrical energy. This type of transduction is well suited to miniaturization.

[0006] Typically, electrical energy is produced in the form of an alternating voltage which is then rectified and then adjusted or regulated by a converter to supply the consumer and / or to recharge a battery.

[0007] Document EP1612059 discloses a device embedded in a vehicle tire, in the inner part of the tire crown. When the vehicle is moving, the mechanical stresses associated with the flexing of the tire are transformed into electrical energy by a piezoelectric transducer, in the form of an alternating voltage. This energy is harvested by a harvesting circuit including a chopping converter, and stored in a storage device. This stored energy can then power an electronic system that includes components for measuring various parameters of the tire such as temperature and internal pressure, as well as a radio transmission device that transmits these measurements and other data to a receiver fixed in the vehicle.

[0008] Document US2015263643 discloses a harvesting circuit, in which the alternating current output signal of the transducer is converted into direct current by an AC-DC converter forming a stage of the SSHI type, for "Synchronized Switch Harvesting on an Inductor". The latter simultaneously produces a rectification of the signal and also a rectification of the signal shape in order to optimize energy harvesting in weakly coupled configurations. It performs these functions by the same synchronous process, by actuating several switches at different times of the cycle in a manner controlled by a control module, depending on the direct voltage obtained at the output of this converter. In this document, the voltage thus rectified and corrected serves as a basis for adjusting the impedance of a DC-DC converter downstream.

[0009] In many application contexts, the acceleration received by the resonator from the environment can vary with time, both in amplitude and frequency. These frequency and amplitude variations are generally slow compared to the period of this mechanical excitation. Other parameters can vary as well, in particular parameters that are inherent to the resonator itself. These other parameters that can vary may include: the mechanical quality factor of the transducer, because the damping depends on the wear of the resonator attachment and the transducer attachment in the resonator; and the capacitance, due to the wear of the piezoelectric material itself.

[0010] In this context, it was proposed to produce adaptive devices, equipped with a Maximum Power Point Tracking capacity, which allows the energy recovery system to be adapted to an operating point which corresponds to the maximum power recovery.

[0011] Among these adaptive solutions, one method is based on the continuous use of a control circuit that estimates the harvested power by measuring the current transferred to the battery. For example, the publication Ottman et al., "Adaptive piezoelectric energy harvesting circuit for wireless remote power supply," IEEE Transactions on Power Electronics, vol. 17, no. 5, pp. 669-676, September 2002. This method is simple to implement and independent of the resonator characteristics, but it requires the use of a specific current measurement system and post-processing by a specialized circuit such as a Digital Signal Processor (DSP). DSPs are advanced signal processing systems, very powerful but which consume significant power, for example compared to microcontrollers.

[0012] Another adaptation method involves a succession of iterations of a short test phase, of the order of a few oscillation periods, and a long phase of normal power production operation. During the measurement phase, the piezoelectric transducer's electrical circuit is interrupted or disturbed to detect the current operating conditions. This measurement is used to recalculate the harvesting circuit's control parameters and thus adjust its operating point for the future, in order to maximize the harvested power. The environmental vibrations and parameters are then assumed to be invariant during the subsequent normal operation phase. Such an adjustment method is disclosed in the publication Xia et al., "Direct calculation of source impedance to adaptive maximum power point tracking for broadband vibration," Journal of Intelligent Material Systems and Structures, September 2016.

[0013] However, the adjustment method used in this publication assumes that electrical disturbances do not modify or only slightly modify the mechanical behavior, which is only valid for a very weakly coupled system. In addition, this method also assumes that the transducer is an ideal source, which is also only valid for a very weakly coupled resonator.

[0014] This method uses an impedance matching calculation of the harvesting circuit to maximize the power produced, for a piezoelectric resonator connected to a rectifier and a buck-boost converter.

[0015] This impedance matching calculation consists of evaluating the equivalent electrical resistance of the circuit formed by the converter and the battery if it exists, to choose the setting that will be imposed on the converter-regulator. This matching calculation is based on a general theory, forming a mathematical model of the behavior of the collection circuit. It is carried out from the theoretical characteristics of the circuit, in particular the maximum capacity Cp of the piezoelectric transducer, as it is initially designed and / or manufactured.

[0016] This general theory is presented for example in the publication Shu and Lien, "Analysis of power output for piezoelectric energy harvesting systems," Smart Materials and Structures, vol. 15, pp. 1499-1512, 2006.

[0017] This type of method, however, has drawbacks and is not easily adaptable to all configurations. For example, such a method requires modifying or disturbing the operating regime of the system during the test phase, which can pose problems in the case where the system parameters depend on its actuation level and often in a non-linear manner. This can thus give insignificant results and therefore make the readjustment poorly adapted.

[0018] Furthermore, it is not very suitable when the piezoelectric transducer has a strong electromechanical coupling, because the behavior of the transducer then depends on the consumer load that it supplies at the output. Its behavior during the no-load test phase therefore becomes irrelevant compared to the normal operating phase.

[0019] Furthermore, the adaptation calculation from the general theory of calculating the driving parameters from the transducer behavior requires complex calculations, and therefore a powerful DSP or processor, which represents a high cost, complexity, size and power consumption. This is particularly problematic when the parameters are not all known due to actuation variations.

[0020] Further examples of prior art, without evaluation of a specific harmonic, are known from KR 10-2004-0131005 A and US 2003 / 0034715 A1. This is also the case for the disclosure of WO 2017 / 191436 A1, which is part of the prior art within the meaning of Art. 54(3) EPC.

[0021] An aim of the invention is to overcome in whole or in part the drawbacks of the state of the art, in particular as described here. In particular, a more reliable, more precise, faster method is sought, applicable to simpler and more compact devices, and with lower consumption. In particular, it is sought to obtain an adaptation of the operating point in the most continuous way possible, and which can be implemented by a simple controller such as a simple microcontroller or a simple processor. Statement of the invention

[0022] The invention proposes a method for controlling an electrical energy harvesting circuit according to claim 1, the electrical energy being produced by a piezoelectric transducer, which produces a piezoelectric resonator under the effect of mechanical vibrations from a mechanical excitation source.

[0023] This harvesting circuit receives a so-called piezo alternating voltage from said piezoelectric transducer, to produce a direct output voltage via a converter, typically a DC-DC converter operating by PWM. This converter is controlled by means of at least one control signal, typically a signal for controlling a duty cycle imposed on the PWM converter. This control signal is determined and adjusted so that this converter has within said harvesting circuit an impedance called equivalent resistance whose value determines a voltage of a determined value, typically a regulated voltage, which depends on said control signal. Typically, for example in the case of powering a battery, the converter regulates the voltage at the input of its terminals.

[0024] According to the invention, this method comprises at least one implementation of a so-called estimation process, by an electronic controller called a pilot controller which is electrically and operationally connected to the piezoelectric transducer and to the converter. This estimation process comprises the following operations: detection, by voltage measurement in a part of the harvesting circuit located between the piezoelectric transducer and the converter, of characteristics of a so-called piezo signal produced by the piezo voltage, during a detection duration prior to a first instant. Typically, this operation is carried out by measuring the instantaneous values ​​of the voltage forming the piezo voltage signal in a direct form, or possibly modified but without deformation.from said detected characteristics, evaluation of the amplitude of at least one harmonic of said piezo signal, said harmonic being of a rank greater than one; from said amplitude and a so-called equivalent current resistance value produced during said detection duration under the effect of a so-called current value of said control signal, calculation of an adjustment to be applied to the converter, said adjustment calculation comprising at least: ∘ a calculation of a so-called new equivalent resistance value to be produced from a second instant subsequent to the first instant, and / or ∘ a calculation of a new control signal value to be applied to the converter to make it produce said new equivalent resistance; application of a control signal with said new value to the converter.

[0025] The term "harmonic" is used here in its classical definition, according to which the "zero" harmonic represents the continuous part of the signal, and the "one" harmonic represents the variation operating according to the fundamental frequency.

[0026] As understood, and as illustrated by the particularities and examples presented here, the evaluation of the amplitude of a harmonic means that an estimated value is determined which represents the amplitude of this determined harmonic, individually, that is to say by distinguishing it from the rest of the signal.

[0027] This evaluation of a harmonic is typically calculated in real time, as is known to those skilled in the art, on the basis of the temporal evolution of the piezoelectric voltage at each instant and in relation to its value at the previous sample. It therefore provides an "estimate" in the automatic sense, that is to say an approximate value of the voltage harmonic obtained.

[0028] The evaluation of the amplitude of "one or more harmonics" therefore relates to the evaluation of a subset of the signal, said subset being formed by a finite number of harmonics. In a preferred embodiment, the evaluation step relates to a single harmonic.

[0029] According to a particularity, this process is implemented: without interruption of energy production, nor opening of the piezo circuit; and / or without measurement of the current or the output power in the battery circuit; and / or without memorizing, that is to say without writing to memory during operation, other values ​​than two successive samples of the piezoelectric voltage as well as the current estimate of the amplitude value of the voltage harmonic.

[0030] As understood, this method makes it possible to adapt the harvesting circuit and its converter to take into account the actual behavior of said circuit, as observed during its operation under load.

[0031] Typically, the calculation of the new equivalent resistance involves solving a polynomial determining the value of the electrical power supplied by the converter, by a Newton-Raphson type gradient method implemented to maximize said electrical power, from the following parameters: the equivalent resistance R of the converter, the maximum capacity C p of the piezoelectric transducer, and the mechanical quality factor Q of the transducer.

[0032] In particular, this resolution concerns the following equation: P = 1 r Ω + π 2 2 k m 2 Ω 2 Mγ 2 / ω 0 1 Q + 2 k m 2 r r Ω + π 2 2 2 Ω 2 + 1 − Ω 2 + k m 2 r Ω r Ω + π 2 2 . Or r = RC p ω 0 , Ω = ω ω 0 And k m 2 = α 2 KC p , and for a mass piezoelectric resonant system M , of stiffness K, of electromechanical coupling coefficient α, of capacity C p , depreciation D , fixed to a base subject to displacement y of pulsation ω and natural frequency ω 0 .

[0033] Typically, the method comprises a pre-characterization process prior to the autonomous operating time, for example carried out only once, for example and using a computer or a pre-characterization controller different from the pilot controller and more powerful.

[0034] This pre-characterization process is arranged according to known methods for carrying out a measurement or a calculation of parameters of the piezoelectric resonator which remain constant during the autonomous operation period, and in particular its mass, its stiffness, its electromechanical coupling, and / or its natural frequency, for one or more excitation levels. The values ​​of these parameters are then stored in a memory accessible to the control controller. The latter reads these values ​​during autonomous operation, and optionally chooses those which correspond to the piezo operating parameters which it detects, for example according to the observed excitation level.

[0035] According to a particular feature, the detection step (51) is carried out by direct measurement (M11) of the voltage signal in the form that it presents at the output of the transducer. Preferably, this is the signal as is and not rectified.

[0036] Alternatively or in combination, this measurement may also relate to a rectified and / or amplified version, but without changing its shape (said non-change being defined over a half period or at least over a quarter of a period). For example, when the circuit comprises a component which distorts the signal, such as capacitor filtration and / or rectification including a modification of the local shape (for example by diode saturation), a feature of the invention provides that the voltage measurement of the detection step will be made between the output of the transducer and the input of said component.

[0037] More particularly, this method is implemented in a harvesting circuit where the converter (123) receives the piezo voltage (Vp) asynchronously without control, directly or via a passive rectification circuit without control, in particular by bipolar directional components such as diodes, and for example without using controlled switches.

[0038] According to advantageous features which may or may not be combined with each other and with the previous ones: The converter is a DC-DC voltage regulator which operates by pulse width modulation and is controlled by a control signal which represents the duty cycle of said modulation. The adjustment calculation step comprises at least: ∘ from the calculated harmonic amplitude and the current resistance value, a calculation of a maximum capacitance value representing the operation of the piezoelectric transducer at the first instant; ∘ from said maximum capacitance and a value of a quality factor, calculated or stored for said piezoelectric transducer, a calculation of the new equivalent resistance.The step of calculating the maximum capacitance value further comprises calculating a value of the maximum displacement amplitude, which represents the operation of the piezoelectric transducer during the detection duration; and said method further comprises calculating the value of said quality factor from the maximum displacement amplitude and an acceleration value received or read from an electronic memory.The method further comprises a measurement or a reading, during the detection duration, of an acceleration value experienced by the piezoelectric transducer; and the adjustment calculation step comprises at least: ∘ from the calculated harmonic amplitude and the current resistance value, a calculation of a maximum capacitance value and a maximum displacement value, which represent the operation of the piezoelectric transducer during the detection duration; ∘ from said maximum displacement amplitude and said acceleration value, a calculation of a quality factor value representing the operation of the piezoelectric transducer, and ∘ from said maximum capacitance and said quality factor, a calculation of the new equivalent resistance value. The step of evaluating at least one harmonic is carried out at least by a recursive least squares method.The amplitude evaluation step relates at least to the amplitude of the third harmonic of the piezoelectric signal. The amplitude evaluation step relates only to the evaluation of one or more harmonics of rank greater than or equal to three, and for example only of a rank equal to three. When evaluating the third harmonic, the steps of calculating the capacitance of the piezoelectric transducer and the quality factor are carried out by solving the following system of equations: . C p = π 4 V sat − 3 a 3 π 6 a 3 πR ω x m = V sat ωRa ωRC p + π 2 In an evaluation of the first harmonic, as an example not forming part of the invention, the steps of calculating the capacitance of the piezoelectric transducer and the quality factor are carried out by solving, as a function of the variable Cp, the following system of equations: V sat 8 C p πRω − 4 2 π C p Rω π − 2 C p Rω ArcCos − 1 + 2 π π + 2 C p Rω + π + 2 C p Rω 2 ArcCos − 1 + 2 π π + 2 C p Rω 2 2 C p πRω = a 1 The control method comprises, during an autonomous operating period, a plurality of iterations each comprising: ∘ the estimation process; ∘ an adjustment process, called servo-control, comprising an application to the converter of the new control signal value resulting from said estimation process, in particular according to a progressive evolution managed according to a correction process of proportional or proportional-integral type; and ∘ a process called nominal operation, during which the electronic controller is kept in standby mode while continuing to supply the converter with said new control signal value.

[0039] Preferably, as disclosed and illustrated herein, the harmonic evaluation provides an evaluation of a single harmonic. Alternatively, it may include an individual evaluation of multiple harmonics.

[0040] Optionally, the method may also use a harmonic evaluation step involving several harmonics forming a subset of the signal, i.e. a finite number of harmonics. These harmonics may be evaluated as a whole, or evaluated individually for separate use.

[0041] According to another aspect, the invention proposes a device for controlling an electrical energy harvesting circuit according to claim 13, the electrical energy being produced by a piezoelectric transducer, which produces a piezoelectric resonator under the effect of mechanical vibrations from a mechanical excitation source.

[0042] This harvesting circuit receives a so-called alternating piezo voltage from said piezoelectric transducer, to produce a direct output voltage via a converter, which is controlled by means of at least one control signal to present within said circuit an impedance called equivalent resistance, the value of which determines an operating voltage of the converter of a value which depends on said control signal.

[0043] This operating voltage is for example an input voltage, when the output is connected to a constant voltage battery.

[0044] This device includes an electronic pilot controller programmed to implement all steps of the piloting method as disclosed or claimed herein.

[0045] According to a particular feature, the invention proposes a circuit for harvesting electrical energy coming from a piezoelectric resonator, as well as an electrical energy generation device comprising such an electrical energy harvesting circuit and a piezoelectric resonator powering said circuit. This circuit is of a type comprising at least: a rectifier stage connected to receive an alternating piezo voltage, forming a piezo signal, from said piezoelectric resonator and producing a rectified voltage; optionally, an intermediate electrical energy storage device receiving the rectified voltage; a controllable regulated converter providing an output voltage,

[0046] According to this feature, said electrical energy harvesting circuit comprises a driving device as set out above, which is connected to measure said piezo signal and drive said converter.

[0047] More particularly, the converter of this harvesting circuit is produced by at least one DC-DC converter operating by chopping and which is controlled by pulse width modulation.

[0048] According to yet another aspect, the invention proposes an electrical energy generation device comprising an electrical energy harvesting circuit as described herein, and a piezoelectric resonator powering said harvesting circuit. This device is characterized in that it further comprises at least one accelerometer arranged to measure an acceleration produced by the excitation source; in that the control controller of said harvesting circuit is connected to receive said acceleration measurement; and in that said controller is arranged to implement all the steps of a control method as described herein.

[0049] According to yet another aspect, the invention provides an electrical or electronic device comprising such an electrical energy generation device, which is arranged to provide it with an autonomous electrical power supply or a supplementary electrical power supply, under the effect of a mechanical vibration excitation provided by the material environment of said electrical or electronic device.

[0050] Unlike known adaptive methods using transducer operation detection, the method of the invention does not require changing or disturbing the operating regime of the system during the test phase. It is therefore more reliable and more accurate. It is based on real-time measurement of the operational functioning of the transducer, and is more applicable to piezoelectric resonators with strong electromechanical coupling.

[0051] The invention makes it possible to ensure maximum power transfer from a variable acceleration acoustic energy source to a storage component such as a battery, regardless of the evolution of the acceleration signal.

[0052] It allows the harvesting circuit to automatically adapt to variations in the amplitude and frequency of the acceleration provided by the vibrating base.

[0053] It allows it to automatically adapt to variations in certain system parameters.

[0054] It also has the advantage of requiring a sufficiently low amount of calculations and signal processing capacity to allow the use of a simple microcontroller, therefore low consumption and low cost and size.

[0055] For example, it may be sufficient for it to be equipped with an analog-to-digital converter and a PWM pulse width modulation generator, which is the case for almost all microcontrollers on the market.

[0056] In the case where the fluctuations in the amplitude and frequency of the acceleration are slow compared to the period of these oscillations, it is also possible to carry out the adaptation calculations only during short test phases, and thus to deactivate or put the controller into standby.

[0057] For example, in comparison with document US2015263643, the invention makes it possible to perform fewer calculations, and to require less memory, thus allowing a simpler, more reliable and less expensive device, in particular for operating transducers with strong coupling. In particular, the technology implemented in this document uses several measurements to maximize the power (the filtered voltage and the output power), whereas the invention makes it possible to be satisfied with a single undistorted voltage measurement. Taking these multiple measurements into account, and the resulting control, require, for example, significant computing and memory capacities, which represent a complexity and constraints that the invention makes it possible to avoid or limit.

[0058] Various embodiments of the invention are provided, incorporating, according to all of their possible combinations, the various optional features set out herein. List of figures

[0059] Other features and advantages of the invention will emerge from the detailed description of a non-limiting mode of implementation, and from the appended drawings in which: there FIGURE 1 is a symbolic diagram that illustrates a stand-alone device according to an exemplary embodiment of the invention; FIGURE 2 is a symbolic diagram illustrating a power supply device according to an exemplary embodiment of the invention; FIGURE 3 is a functional diagram which illustrates a control method according to an exemplary embodiment of the invention; FIGURE 4 is a simulation graph which illustrates the evolution over time of different operating parameters of the power supply device according to an exemplary embodiment of the invention, with: ∘ in FIGURE 4a , the power produced, ∘ in FIGURE 4b , the duty cycle commanded to the converter, ∘ in FIGURE 4c , the maximum amplitude of movement of the piezoelectric transducer, as calculated by the controller, ∘ in FIGURE 4d , the equivalent capacitance of the piezoelectric transducer, as calculated by the controller, ∘ in FIGURE 4e , the mechanical quality factor of the piezoelectric transducer, as calculated by the controller; FIGURE 5 is an impedance matching graph which represents, for a power supply device with a piezoelectric generator driven to produce the optimal power: ∘ at the top, the evolution of the normalized electrical power produced, and ∘ at the bottom, the evolution of the normalized equivalent resistance value which is controlled for the converter; the FIGURE 6is a graph that represents the piezoelectric voltage and the rectified voltage at the input of the converter of a power supply device according to an exemplary embodiment of the invention, for a full-wave rectifier stage and a single-wave rectifier stage. Description of an exemplary embodiment

[0060] The invention makes it possible to ensure maximum power transfer from a source of acoustic energy with variable acceleration to a storage device, such as a battery, regardless of the evolution of the acceleration signal. The interest of the invention is multiple. It allows the device to: to automatically adapt to variations in the amplitude γ and the frequency of the acceleration provided by the vibrating base 100, and therefore to variations in the amplitude xm and the frequency of the transducer. The only assumption is to assume that the fluctuations in the amplitude and frequency of the acceleration are slow compared to the period of the oscillations of the resonator, to automatically adapt to variations in certain parameters of the system, predictable or not, which could influence its operation, to require a sufficiently low amount of calculation and signal processing so that it is sufficient to use a simple microcontroller, therefore with low power consumption, as long as it is equipped with an analog-digital converter and a PWM generator, which is the case for almost all microcontrollers on the market.

[0061] The combination of these possibilities goes beyond simply improving certain performances in an existing application, and gives a coherent whole which enables many new applications.

[0062] In its normal operation, i.e. in operation, the control method comprises a repetition of iterations of a cycle of phases carrying out different processes. These iterations are triggered for example by a clock, and / or upon receipt of specific external signals such as environmental sensors or commands coming from external systems or devices.

[0063] Each iteration within this normal operation typically takes place in three stages. A first phase consists of estimating the steady-state parameters. The second phase consists of controlling the load resistance of the DC-DC converter (via the duty cycle requested by the control signal) to the optimal resistance value corresponding to these parameters estimated in the first phase. The last phase constitutes a nominal operation phase, during which the PWM signal applied to the converter is maintained identically, and where the system parameters and acceleration are assumed to be invariant. Description of the device and method

[0064] In the example illustrated in FIGURE 2, the electromechanical conversion is carried out by a resonator 101 including a piezoelectric transducer 11. The resonator 101 is actuated by the vibration 10 of a vibrating base 100, here along a dimension "y". This vibration causes an oscillation in the resonator, here along a dimension "x", which produces a mechanical deformation of the piezoelectric transducer 11.

[0065] This example illustrates a single-degree-of-freedom linear resonator, which is particularly simple to implement and model. But the invention can also be applied to harvesting energy from different sources and / or by one or more resonators of different or even more complex types.

[0066] The piezoelectric transducer 11 is connected to a rectifier system 121 with a diode bridge and a smoothing capacitor 122. The energy transfer from the smoothing capacitor is then ensured by a DC-DC conversion system 123 controlled by a signal acting in Pulse Width Modulation (PWM), for example of the chopper type, the switch of which is controlled by a signal S148 delivered by a microcontroller 140.

[0067] In this system, we note that the adjustment of the control signal S148 of the switch is made possible by the sole measurement of a single voltage, namely the voltage Vp at the terminals of the piezoelectric resonator 101.

[0068] In this example, optionally, the microcontroller 140 is also connected to an accelerometer 145 which detects in real time the accelerations occurring in the vibrating base or in the resonator.

[0069] There FIGURE 2symbolically represents the complete device 1, in a functional representation, but the actual device may include additional functions or circuits, and / or realize certain functions or components in the form of equivalent circuits.

[0070] There FIGURE 3 schematically represents the main steps executed by the microcontroller 140 which implements the control controller 14 of the device 14.

[0071] A certain number of parameters of the device and / or the resonator are determined in a pre-characterization phase 50, which is prior to the nominal use 54 of the device 1, for example during the design of the device or during a calibration phase and according to known methods.

[0072] Each iteration 59 performs a cycle which includes, in this order or another: an estimation process, including a detection phase 51 and a calculation phase 52 of new parameters; followed by an adjustment process 53 where the new parameters are applied to the converter 123; and a nominal production and load operating process, which generally represents the majority of the cycle.

[0073] As can be seen, the energy production and the charging 55 of the battery and / or the supply of the consumers are continued during all the steps of the method, including the estimation process 51, 52 and the adjustment process 53. Preferably, this energy production and supply 55 are thus carried out continuously during the entirety of this normal operation 5, without any interruption of the energy production.

[0074] There FIGURE 4 illustrates the evolution over time of different operating parameters of the power supply device: the power produced at the output of the converter 123; the duty cycle δ commanded to the converter 123; the maximum amplitude xm of movement of the piezoelectric resonator, as calculated 524 by the controller 14, 145; the equivalent capacitance Cp of the piezoelectric transducer 11, as calculated 524 by the controller 14, 145; and the mechanical quality factor Q of the piezoelectric transducer, as calculated 525 by the controller 14, 145, in the case where the controller has the value "γ" of the acceleration.

[0075] This figure represents an operation that includes only one adjustment.

[0076] Until time t1 (t=3s), the device operates nominally, i.e. without changing its control parameters, with a value δn of the duty cycle, providing an equivalent resistance R n .

[0077] During the detection duration d0, from time t0 (t=2.5s) and up to t1, the controller 14 carries out the detection phase 51: it wakes up 511 the microcontroller 140 and the accelerator 15, then it reads and records 512 the voltage Vp and acceleration γ parameters.

[0078] During the duration d1, between t1 and t2 (t=4s), the controller 14 progressively applies the new duty cycle value δn+1 to the converter 123. In this example, the control signal S148 is progressively modified, here using a controller 147 operating in proportional or proportional-integral mode carrying out progressive control to arrive at the new value δn+1 of the duty cycle δ, thus producing the new value Rn+1 of the equivalent resistance.

[0079] From t2, the control controller 14 is put on standby and only supplies the control signal S148 to the converter 123, and the device operates nominally without modification of this parameter for the duration d2.

[0080] As seen in FIGURE 2 , the microcontroller 140 requires only two connections: a measurement M11 of the instantaneous voltage Vp across the piezoelectric transducer 12, preferably but not necessarily before the rectifier 121; and sending a control signal S148 to the converter 123 to control its impedance according to the adjustment calculated by the microcontroller 140.

[0081] Within the microcontroller 140, the measurement of the instantaneous voltage Vp is carried out by a voltage measurement block or module 141. This measurement block 141 transmits the instantaneous state of this voltage to: a frequency detection block 142, which determines the frequency at which this instantaneous voltage Vp oscillates, and a peak detection block 143, which determines the exact instant at which the maximum of this voltage Vp occurs.

[0082] The frequency detection block 142 transmits its results to a harmonic estimation block 144, which evaluates the amplitude of the oscillations of the voltage Vp for one harmonic (or several) of its base frequency.

[0083] From the results of the harmonic estimation block 144 and the results of the peak detection block 143, and the values ​​of certain quantities previously stored for the device 1, the microcontroller 140 performs a calculation 51, 52 estimating the parameters which must be used by the converter 123 during the next nominal operating period.

[0084] This estimation calculation 51, 52 is for example carried out by a first calculation block 145 operationally connected with a second calculation block 146.

[0085] The first calculation block 145 receives the results of the harmonic estimation block 144 and the peak detection block 143, as well as the "γ" (gamma) value of the acceleration, which is detected in the mechanical part of the resonator by an accelerometer 15 integrated into the device 1. Optionally, this value is read from a memory where a typical value for the average of this acceleration has been stored, or a value read or estimated by another device connected to the device.

[0086] For example, this first calculation block 145 carries out the operations of calculation 523 of the amplitude ah of the harmonic concerned according to the invention, calculation 524 of the capacitance of the transducer 11 during the detection period, and calculation 525 of the mechanical quality factor Q.

[0087] From these elements, the second calculation block 146 performs the calculation of the optimized value of the equivalent resistance Rn+1 which will be targeted for the converter 123 during the next nominal operating period 54, and the value δn+1 of the duty cycle which will be used as control signal S148 to reach this equivalent resistance value. Modeling

[0088] As illustrated in FIGURE 2 , the resonator model used is that of a piezoelectric resonant system with one degree of freedom, of mass M, of stiffness K, of electromechanical coupling coefficient α, of capacity C p , depreciation D, fixed to a base subject to displacement y of pulsation ω . With these notations, the behavior of the system is therefore described by equation (1): d 2 x dt 2 + ω 0 Q dx dt + ω 0 2 x + α M V = d 2 x dt 2 i = α dx dt − C p dV dt ⋅

[0089] The displacement of the resonator is noted x = xm sin( ωt ). It is assumed that the values ​​of the parameters M, K And α of the resonator are known (for example stored in the form of tables after the pre-characterization phase 50), but that the quality factor Q and the capacity C p of the device are unknown and may vary over time. The acceleration is measured here via an accelerometer 15. Principle of adjustment

[0090] Considering that the DC-DC converter 123 behaves like a resistor R equivalent, the recovered power is written: P = 1 r Ω + π 2 2 k m 2 Ω 2 Mγ 2 r / ω 0 1 Q + 2 k m 2 r r Ω + π 2 2 2 Ω 2 + 1 − Ω 2 + k m 2 r Ω r Ω + π 2 2 . Or r = RC p ω 0 , Ω = ω ω 0 And k m 2 = α 2 KC p .

[0091] In the following, we will also use the coupling coefficient k 2 = k m 2 1 + k m 2

[0092] From equation (2), it can be shown that the optimal resistance depends on ω 0, of ω , of k m 2 and of Q . It does not depend on acceleration γ , and does not depend directly on the amplitude of the displacement xm .

[0093] There FIGURE 5 represents, on the top graph, the evolution of the maximum power (normalized with respect to Mγ 2 8 ω 0 ), obtained for optimal impedance matching for each frequency ( r = r opt (Ω) ) and, for a quality factor Q = 100. This evolution is illustrated here by three curves, corresponding to three different coupling levels, with k 2< Q = 10 , k 2< Q = π / 4 , And k 2< Q = 0.3 π / 4.

[0094] The bottom graph represents the equivalent normalized resistance corresponding to these recovered power values.

[0095] The optimal resistance does not depend on the acceleration or the amplitude of the displacement but only on the parameters ω 0 , k m 2 = αC p / Mω 0 2 And Q. As it is assumed that ω 0 and α are known, so it is sufficient to determine C p And Q. To adjust the system to maximum power point tracking (MPPT), it is sufficient to solve the polynomial giving the optimal resistance. The optimal duty cycle of the PWM signal controlling the DC-DC converter, for example a buck-boost chopper, can then be deduced via: δ = Lω Rπ

[0096] To estimate the parameters C p And Q , the control is based on the measurement of the piezoelectric voltage and the real-time estimation of the third harmonic of the piezoelectric voltage signal.

[0097] There FIGURE 6 illustrates the shape of the signal V (Vrect) obtained at the output of rectifier 121, for a full-wave rectifier (as illustrated in FIGURE 2 ) or simple alternation type. Harmonic one

[0098] According to the general theory, and using the estimation process according to the invention, it is possible to estimate the movement of the resonator from: the signal average V for a half-wave rectifier, or the first harmonic of the voltage signal Ṽ for a full-wave rectifier.

[0099] This method would require solving a nonlinear equation with no obvious solution at each iteration step.

[0100] In such an embodiment, and in the case of a double rectifier, the estimation process comprises a numerical resolution operation to find the parameter Cp, in which each calculation step solves the following equation (with Cp as unknown): V sat 8 C p πRω − 4 2 π C p Rω π − 2 C p Rω ArcCos − 1 + 2 π π + 2 C p Rω + π + 2 C p Rω 2 ArcCos − 1 + 2 π π + 2 C p Rω 2 2 C p πRω = a 1 Or a 1 is the amplitude of the first harmonic of the piezoelectric voltage signal and where R is the resistance value at the time of measurement.

[0101] This calculation gives a precise result, which makes it possible to adapt the operating point to the evolution of the real behavior of the transducer in operating conditions.

[0102] It is proposed by the inventors to create an adaptive system, more particularly in a configuration where significant computing power is available. Harmonic three

[0103] However, the relationship between these quantities and the resonator displacement is very complex for the first harmonic, and this operation generates heavy calculations, which are incompatible with the use of low-power microcontrollers.

[0104] On the other hand, the inventors determined that the relationship between the resonator displacement and some higher harmonics is linear and very simple. These relationships can be found from equation (1) and the waveforms depicted on the FIGURE 6 .

[0105] As an example, and in a currently preferred embodiment, in the case of a low power and consumption computer they propose to use the 3rd harmonic of the piezoelectric voltage.

[0106] Thus, in the case of a full-wave rectifier, we find: C p = π 4 V sat − 3 a 3 π 6 a 3 πRω x m = V sat ωRα ωRC p + π 2 Or a 3 is the amplitude of the 3rd harmonic of the piezoelectric voltage.

[0107] With a harmonic of rank strictly greater than one, and for example of rank three, this method then makes it possible to obtain an estimate of the movement of the resonator (in amplitude and frequency) via a simple explicit expression which requires a minimum of calculations. From the estimate of this movement, combined with the knowledge of the natural frequency ω 0 (determined during the pre-characterization 50) and the measurement of the acceleration, we can then estimate the quality factor, then calculate the optimal resistance and therefore the duty cycle to impose on the DC-DC converter to obtain an optimal impedance adaptation.

[0108] Preferably, the harmonic estimation procedure used is a recursive least squares method, for example as described in the publication KH Youssef A. El Zawawi and OA Sebakhy, "Recursive Least Squares Harmonic Identification in Active Power Filters," in Proceedings of the European Control Conference, Kos (Greece), 2007.

[0109] This procedure has the advantage of requiring both few calculations and little memory, which are strong constraints in the case of using microcontrollers to produce the control controller 14. The choice of this estimation procedure is an example, and other harmonic estimation methods can also be used.

[0110] The exemplary embodiment described herein uses a four-diode rectifier bridge 121, providing full-wave.

[0111] However, independently of the other optional features of the invention, it is also planned to use a single-wave circuit. It has, for example, the advantage of limiting the size and providing better electrical efficiency at low voltage levels.

[0112] In some embodiments, the rectifier circuit is full-wave but the microcontroller 140 is of a type including an analog-to-digital converter 141 limited to measuring positive voltages, as is often the case for low-power microcontrollers.

[0113] In this case, the waveform of the piezoelectric voltage measured by the microcontroller is identical to that obtained for a single-wave rectifier, with the only difference being that it has a threshold voltage of 2 V d instead of V d . This does not hinder the identification of the characteristics of the voltage oscillations V p .

[0114] It will be noted that other harmonics of higher rank than three can also be used within the framework of the invention, by adapting the resolution to the equations corresponding to the chosen harmonic. Calculation of the optimal duty cycle of DC-DC converter control

[0115] The optimum equivalent resistance to drive the DC-DC converter 123 can be found by solving in a polynomial of degree 5, of which only one root is real and positive. This polynomial is obtained in the numerator by differentiating equation (2) with respect to "r".

[0116] The resolution only needs to be performed once, at the instant when the estimate of the maximum displacement xma converges.

[0117] This polynomial depends on the coupling coefficient k m 2 x m , of the mechanical quality factor Q ( xm ), and the ratio between the frequency of oscillations and the natural frequency of the resonator ω / ω 0 ( xm ).

[0118] A pre-characterization 50 of the resonator 101 makes it possible to determine the value of these coefficients for different excitation levels, and these results are then known by the system 14, for example stored in tables or restored by a simple law determined empirically.

[0119] During the estimation calculation phase 526, 527, the controller 14 then chooses for these coefficients the known value which corresponds to the amplitude x m ^ obtained during the estimation calculation 524 of the previous iteration.

[0120] The resolution 526 of the polynomial can be done with a simple gradient method (for example Newton-Raphson type). Once this calculation is carried out, the optimal duty cycle can then be determined 527.

[0121] Then, for example by passing through a proportional (or proportional-integral) corrector 147, the control signal S148 applied to the converter 123 is modified to obtain that the duty cycle δ converges and adjusts to this new value δn+1, which makes it possible to obtain the maximum recoverable power again.

[0122] In this example, a smoothing capacitance of 1µF was chosen. These graphs show a transient state followed by stabilization at the optimal operating point for this oscillation frequency.

[0123] At time t2, once the desired duty cycle is reached, the microcontroller 140 is stopped, except for the PWM output 148 which controls the DC-DC converter 123.

[0124] The alarm 511 for a new adjustment procedure 51, 52, 53 can be operated for example at a frequency chosen by the designer, which depends on the intended application. Simulation results

[0125] There FIGURE 4 represents results of transient regime simulations (carried out under MATLAB / Simulink) demonstrating the feasibility of the adjustment, which can thus be described as control at a maximum power point. FIGURE 4c illustrates the evolution of the estimated displacement amplitude xm , after starting the algorithm for a resonator with characteristics M = 3 mg, Q = 30, k 2<=0.2, C p = 100 nF And f 0 = 100 Hz, an acceleration of 10m.s -2< at the frequency f = f 0 1 + k m 2 2 and a duty cycle initially set at δ = 8.10 -3< . The smoothing capacity 122 is set to 10µF. The gain of the proportional corrector is set to 10 -4< .

[0126] As illustrated in FIGURE 4b , the adjustment process 53 carried out between t1 and t2 gradually brings the duty cycle to a new value δ= 3,391.10 -3< , which was calculated in 527 during the estimation process 52.

[0127] In the FIGURE 4c to FIGURE 4e , the red curve represents the actual value, while the black curve represents the estimated value as calculated during the estimation process 52, in 524 for the parameters xm and Cp and in 525 for the parameter Q.

[0128] During the initial period up to t 0 , this simulation starts with a suboptimal operating regime, i.e. with a duty cycle that is not suitable for having the maximum power. In this simulation, the values ​​used for the parameters xm and Cp during the initial period (up to t 0 ) are assumed to be perfect estimates, i.e. equal to the real value. The red curve is therefore superimposed on the black curve over this period.

[0129] At time t 0 , controller 14 launches an estimation procedure 51, 52 which ends at t 1 .

[0130] At time t 1 , when the estimation process 52 ends, the new estimated values ​​for xm and Cp are stored and will not be recalculated until the next estimation period.

[0131] The black curve is therefore constant from t 1 , and we see the estimation errors by looking at the difference between the black curves and the red curves.

[0132] From t1, we keep the estimates in memory then we modify 53 the duty cycle δ until the new value δ n+1 determined by the algorithm.

[0133] As seen in FIGURE 4c, on the other hand, the actual value calculated by the simulation for the amplitude xm increases gradually after t 1 to stabilize at a higher value. The displacement amplitude varies because we change the duty cycle, therefore the equivalent resistance of the load, therefore the piezoelectric voltage. Because it is a strongly coupled system, this variation in the piezoelectric voltage is reflected in the displacement which also varies. In the present case, we decrease the duty cycle therefore we increase the equivalent resistance, therefore we increase Vrect which has the effect of shortening the duration of the periods when the current passes through the rectifier bridge. For a given displacement, we then have less electrical damping; which increases the displacement.

[0134] This significant impact of the electrical circuit on the mechanical displacement also reflects the fact that the configuration tested is that of a system with strong coupling. The importance of this variation in displacement is typical of strong coupling, and makes this estimation method all the more useful, as it is simpler and can therefore be carried out more quickly and more often with lower consumption.

[0135] The difference between estimated xm and actual xm increases from t1 since we stop estimating the parameters.

[0136] This variation of xm is not a problem if the parameters (the other operating / performance parameters of the transducer?) depend little on xm.

[0137] Beyond a certain duration, or upon detection of a parameter indicating that xma has varied by more than a determined threshold in relation to the value estimated and stored in t1, the controller restarts 59 a new iteration of the estimation and adjustment procedure.

[0138] Once adjustment 53 has been made, from time t 2 , we see on the FIGURE 4a that the recovered power is well maximized. In this simulation, the accelerometer 15 is only switched on between t 0 (t=2.5s) and t 1 (t=3s), and the microcontroller 140 is only switched on between t 0 (t=2.5s) and t 1 (t=4s). The rest of the time both are switched off, except for the PWM generator 148 which is kept on at a constant duty cycle and which controls the converter 123. These two devices 140, 15 can be switched on periodically. A short period d2 between two adjustments 51, 52, 53 uses more power but adapts better to variations in acceleration, C p and Q, than a long period.

[0139] In FIGURE 4a , we then observe that the power temporarily decreases during the adjustment process 53 between t 1 and t 2 , which is because it is a non-minimum phase system. It then starts to increase until it reaches a power level P n+1 which is higher than the initial level P n .

[0140] This increase in recovered power thus demonstrates that the process has improved energy harvesting.

[0141] Throughout the optimization process, it should be noted that the circuit is never interrupted and the power produced is never completely interrupted, which allows the estimation to be carried out on the system under load and therefore in real conditions.

[0142] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention as defined by the claims.

Claims

1. Method (5) for controlling a harvesting circuit (12) for electrical energy produced by a piezoelectric transducer (11) in the form of a piezoelectric resonator (101) under the effect of mechanical vibrations (10) originating from a mechanical excitation source, in which said harvesting circuit receives an alternating "piezo" voltage (Vp) originating from said piezoelectric transducer to produce a direct output voltage (Vout) by way of a converter (123) that is controlled by means of at least one control signal (S148) in order to have within said harvesting circuit (12) an impedance (R), or "equivalent resistance", the value of which establishes a voltage of a certain value that depends on said control signal, said method being characterised in that it comprises at least one performance of an "estimation" process (51, 52) by an electronic "control" driver (140) which is electrically and operationally connected to the piezoelectric transducer (11) and to the converter (13), said estimation process comprising the following operations: - detection (51), by voltage measurement (M11) in a part of the harvesting circuit (12) located between the piezoelectric transducer and the converter, of characteristics of a "piezo" signal produced by the piezo voltage (Vp), during a detection period (d0) prior to a first instant (t1); - evaluation (523) of the amplitude (ah, a1, a3) of at least one harmonic of said piezo signal, comprising a calculation (523) of the amplitude (ah) of the harmonic in question, of said detected characteristics, said harmonic being of a rank greater than one; and - calculation (52) of an adjustment to be applied to the converter, on the basis of said amplitude (ah) and a "current equivalent resistance" value (Rn) produced during said detection period (d0) under the effect of a "current" value (δn) of said control signal (S148), said adjustment calculation (52) comprising at least: ∘ a calculation (526) of a "new equivalent resistance" value (Rn + 1) to be produced on the basis of a second instant (t2) subsequent to the first instant (t1), and / or ∘ a calculation (527) of a new control signal value (δn + 1) to be applied to the converter (13) to cause it to produce said new equivalent resistance (Rn + 1); said method comprising a step of: - applying (53, d1, d2) a control signal (S148) with said new value (δn + 1) to the converter.

2. Method according to the preceding claim, characterised in that the detection step (51) is carried out by direct measurement (M11) of the voltage signal in the form it has at the transducer outlet.

3. Method according to the preceding claim, characterised in that it is implemented in a harvesting circuit where the converter (123) receives the piezo voltage (Vp) asynchronously without control, directly or by way of a passive rectifier circuit without control, in particular by bipolar directional components such as diodes.

4. Method according to any one of the preceding claims, characterised in that the adjustment calculation step (52) comprises at least: - a calculation (524) of a maximum capacitance value (Cp) representing operation of the piezoelectric transducer at the first instant (n), performed on the basis of the calculated harmonic amplitude (a3) and the current resistance value (Rn); and - a calculation (526) of the new equivalent resistance (Rn + 1), performed on the basis of said maximum capacitance (Cp) and a value of a quality factor (Q) calculated (525) or saved for said piezoelectric transducer.

5. Method according to any one of the preceding claims, characterised in that the step (524) of calculating the maximum capacitance value (Cp) further comprises calculation of a value of the maximum displacement amplitude (xm) which represents operation of the piezoelectric transducer (11) during the detection period (d0); and in that said method further comprises calculation (525) of the value of said quality factor (Q) on the basis of the maximum displacement amplitude (xm) and an acceleration value (γ, gamma) received (15) or read from an electronic memory.

6. Method according to any one of the preceding claims, characterised in that it further comprises measurement (15) or reading, during the detection period (d0), of an acceleration value (γ) undergone by the piezoelectric transducer; and in that the adjustment calculation step (52) comprises at least: - on the basis of the calculated harmonic amplitude (a3h) and the current resistance value (Rn), calculation (524) of a maximum capacitance value (Cp) and a maximum displacement value (xm) which represent operation of the piezoelectric transducer (11) during the detection period (d0); - on the basis of said maximum displacement amplitude (xm) and said acceleration value (γ), calculation (525) of a value of a quality factor (Q) representing operation of the piezoelectric transducer (11), and - on the basis of said maximum capacitance (Cp) and said quality factor (Q), calculation (527) of the new equivalent resistance value (Rn + 1).

7. Method according to any one of the preceding claims, characterised in that the step of evaluating (523) at least one harmonic is performed at least by a recursive least squares method.

8. Method according to any one of the preceding claims, characterised in that the step of evaluating (523) the amplitude relates to the amplitude (a3) of the third harmonic of the piezo signal, and in particular solely of a rank equal to three.

9. Method according to the preceding claim and one of claims 5 or 6, characterised in that the steps of calculating (524) the capacitance of the piezoelectric transducer and of calculating (525) the quality factor are performed by solving the following system of equations: C p = π 4 V sat − 3 a 3 π 6 a 3 πRω x m = V sat ωRα ωRC p + π 2 where α3 is the amplitude of the third harmonic of the piezoelectric voltage.

10. Method according to any one of the preceding claims, characterised in that the step of evaluating (523) the amplitude relates solely to the evaluation of harmonics of a rank greater than or equal to three.

11. Method according to any one of claims 1 to 7, characterised in that the steps of calculating (524) the capacitance of the piezoelectric transducer and of calculating (525) the quality factor are performed by solving the following equation: V sat 8 C p πRω − 4 2 π C p Rω π − 2 C p Rω ArcCos − 1 + 2 π π + 2 C p Rω + π + 2 C p Rω 2 ArcCos − 1 + 2 π π + 2 C p Rω 2 2 C p πRω = a 1 where a1 is the amplitude of the first harmonic of the piezoelectric voltage signal and where R is the resistance value at the time of measurement.

12. Control method according to any one of the preceding claims, characterised in that it comprises, during a period of autonomous operation, a plurality of iterations each comprising: - the estimation process (51, 52, d0); - an adjustment, "regulation" process (53, d1), comprising application to the converter of the new value (δn + 1) of the control signal (S148) originating from said estimation process, in particular according to a progressive development managed according to a proportional or proportional-integral type correction process; and - a "nominal operation" process (d2), during which the electronic driver (140) is kept in standby mode while continuing to supply (S148) the converter (13) with said new control signal value (δn + 1).

13. Device (14) for controlling a harvesting circuit (12) for electrical energy produced by a piezoelectric transducer (11) in the form of a piezoelectric resonator (101) under the effect of mechanical vibrations (10) originating from a mechanical excitation source, said harvesting circuit receiving an alternating "piezo" voltage (Vp) originating from said piezoelectric transducer to produce a direct output voltage (Vout) by way of a converter (13) that is controlled (δ) by means of at least one control signal (S148) in order to have within said circuit an "equivalent resistance" impedance (R) the value of which establishes an operating voltage for the converter of a value that depends on said control signal, said device (14) comprising an electronic control driver (140) programmed to implement all the steps of a control method (5, 140) according to any one of the preceding claims.

14. Harvesting circuit (12) for electrical energy coming from a piezoelectric resonator (101), or device for generating electrical energy comprising such an electrical energy harvesting circuit and a piezoelectric resonator supplying said harvesting circuit, said harvesting circuit comprising at least: - a rectifier stage (121) connected to receive an alternating piezo voltage (Vp) forming a piezo signal from said piezoelectric resonator and producing a rectified voltage (Vr); - optionally a device for intermediate storage of electrical energy (13) receiving the rectified voltage; and - a controllable regulated converter (13) supplying an output voltage (Vout), characterised in that said electrical energy harvesting circuit comprises a control device according to claim 13 which is connected to measure said piezo signal and control said converter.

15. Circuit according to the preceding claim, characterised in that the converter (123) is embodied by at least one DC-DC converter operating by chopping and which is controlled (S148) in pulse-width modulation (δ).

16. Device for generating electrical energy, comprising a harvesting circuit (12) for electrical energy according to claim 14 or 15, and a piezoelectric resonator (101) supplying said harvesting circuit, the device being characterised in that it further comprises at least one accelerometer (15) arranged to measure an acceleration (γ) produced by the excitation source (100), in that the control driver (140) of said harvesting circuit is connected to receive said acceleration measurement, and in that said driver is arranged to implement all the steps of a control method (5) according to any one of claims 6 to 12.

17. Electrical or electronic device (1) comprising a control device according to claim 13, or a harvesting circuit according to either one of claims 14 or 15, or a device for generating electrical energy according to claim 16, arranged to provide it with an autonomous electrical power supply or a supplemental electrical supply under the effect of vibrational mechanical excitation (10) supplied by the hardware environment of said electrical or electronic device (1).