Converter of a variation in energy to be harvested into a potential difference, this converter including: - a first transducer including a layer (40; 152; 178) extending essentially in a plane, called a reference plane, and behaving mechanically as a single block of material, this layer being able to lengthen in the interior of at least one first zone (36, 38; 157, 159) of deformation of the reference plane and, simultaneously, to shrink in the interior of at least one second zone (37, 39; 156, 158) of deformation of the reference plane in response to a given variation in energy to be harvested, the second zone being distinct from the first zone; and - electromechanical second and third transducers (42-45; 72-75; 222), each electromechanical transducer including: • a layer (54; 78; 224) made of piezoelectric material extending essentially parallelly to the reference plane and having exterior and interior faces extending parallelly to this plane, the interior face being fixed with no degree of freedom to the layer of the first transducer in order to undergo a mechanical stress exerted by one of the zones of this layer; and • first (56; 80; 226) and second (40; 228) electrodes made of electrically conductive material extending essentially parallelly to the reference plane along at least one of the faces of the layer made of piezoelectric material of the second transducer in order to cause an excess of electrical charges to appear on one of these electrodes in response to the mechanical stress undergone by the layer made of piezoelectric material, in which the interior faces of the electromechanical second and third transducers are fixed with no degree of freedom essentially to the first and second zones of deformation of the layer of the first transducer, respectively, and the third transducer differs from the second transducer by a polarization of its layer made of piezoelectric material in a direction different from the polarization of the layer made of piezoelectric material of the second transducer and/or by the existence of a separation mechanically and electrically insulating its first electrode from the first electrode of the second transducer, which electrode is located on the same side of the layer made of piezoelectric material. - a first transducer including a layer (40; 152; 178) extending essentially in a plane, called a reference plane, and behaving mechanically as a single block of material, this layer being able to lengthen in the interior of at least one first zone (36, 38; 157, 159) of deformation of the reference plane and, simultaneously, to shrink in the interior of at least one second zone (37, 39; 156, 158) of deformation of the reference plane in response to a given variation in energy to be harvested, the second zone being distinct from the first zone; and - electromechanical second and third transducers (42-45; 72-75; 222), each electromechanical transducer including: • a layer (54; 78; 224) made of piezoelectric material extending essentially parallelly to the reference plane and having exterior and interior faces extending parallelly to this plane, the interior face being fixed with no degree of freedom to the layer of the first transducer in order to undergo a mechanical stress exerted by one of the zones of this layer; and • first (56; 80; 226) and second (40; 228) electrodes made of electrically conductive material extending essentially parallelly to the reference plane along at least one of the faces of the layer made of piezoelectric material of the second transducer in order to cause an excess of electrical charges to appear on one of these electrodes in response to the mechanical stress undergone by the layer made of piezoelectric material, in which the interior faces of the electromechanical second and third transducers are fixed with no degree of freedom essentially to the first and second zones of deformation of the layer of the first transducer, respectively, and the third transducer differs from the second transducer by a polarization of its layer made of piezoelectric material in a direction different from the polarization of the layer made of piezoelectric material of the second transducer and/or by the existence of a separation mechanically and electrically insulating its first electrode from the first electrode of the second transducer, which electrode is located on the same side of the layer made of piezoelectric material. • a layer (54; 78; 224) made of piezoelectric material extending essentially parallelly to the reference plane and having exterior and interior faces extending parallelly to this plane, the interior face being fixed with no degree of freedom to the layer of the first transducer in order to undergo a mechanical stress exerted by one of the zones of this layer; and • first (56; 80; 226) and second (40; 228) electrodes made of electrically conductive material extending essentially parallelly to the reference plane along at least one of the faces of the layer made of piezoelectric material of the second transducer in order to cause an excess of electrical charges to appear on one of these electrodes in response to the mechanical stress undergone by the layer made of piezoelectric material,