Converter of a variation of energy to be harvested into a potential difference between two connection terminals, the variation of energy to be harvested being a variation of magnetic field or of temperature, this converter comprising: - a piezoelectric membrane having: • parallel inner and outer faces, • at least two ends diametrically opposed relative to a plane at right angles to its inner and outer faces, and passing through the center of gravity of the piezoelectric membrane, and • a mid-point situated mid-way between the diametrically opposed ends, - first and second electrodes of electrically conductive material extending essentially along at least one face of the piezoelectric membrane to reveal an excess of electrical charges on one of these electrodes in response to the deformation of the piezoelectric membrane, - a transducer layer extending between anchoring points (262, 263; 276, 277), this transducer layer being suitable for transforming the variation of energy to be harvested into a mechanical displacement of the anchoring points relative to one another between a distant position, in which the anchoring points are distant from one another, and a close position in which the anchoring points are closer to one another, each of these anchoring points being attached to a fixing point situated on the piezoelectric membrane to deform this piezoelectric membrane by bending reversibly between a bent position and a less bent position when these anchoring points are displaced, the amplitude of the maximum travel between its bent and less bent positions being greater than the thickness of the piezoelectric membrane, and - a frame (252; 272), characterized in that: - only one of the ends of the membrane and of the mid-point is fixed, without any degree of freedom, in the frame, and - the converter comprises, between each anchoring point (262, 263; 276, 277) and the fixing point to which it is attached, a rigid arm (258, 259; 280, 281) tensioned between this anchoring point and this fixing point, this arm being suitable for transforming the displacement of the anchoring points into a displacement which deforms the piezoelectric membrane between its bent and less bent positions, the fixing point being situated on the mid-point when the ends of the piezoelectric membrane are fixed, with no degree of freedom, in the frame and the fixing point (274, 275) being situated on a respective end of the piezoelectric membrane when the mid-point is fixed, with no degree of freedom, in the frame. - a piezoelectric membrane having: • parallel inner and outer faces, • at least two ends diametrically opposed relative to a plane at right angles to its inner and outer faces, and passing through the center of gravity of the piezoelectric membrane, and • a mid-point situated mid-way between the diametrically opposed ends, • parallel inner and outer faces, • at least two ends diametrically opposed relative to a plane at right angles to its inner and outer faces, and passing through the center of gravity of the piezoelectric membrane, and • a mid-point situated mid-way between the diametrically opposed ends, - first and second electrodes of electrically conductive material extending essentially along at least one face of the piezoelectric membrane to reveal an excess of electrical charges on one of these electrodes in response to the deformation of the piezoelectric membrane, - a transducer layer extending between anchoring points (262, 263; 276, 277), this transducer layer being suitable for transforming the variation of energy to be harvested into a mechanical displacement of the anchoring points relative to one another between a distant position, in which the anchoring points are distant from one another, and a close position in which the anchoring points are closer to one another, each of these anchoring points being attached to a fixing point situated on the piezoelectric membrane to deform this piezoelectric membrane by bending reversibly between a bent position and a less bent position when these anchoring points are displaced, the amplitude of the maximum travel between its bent and less bent positions being greater than the thickness of the piezoelectric membrane, and - a frame (252; 272), - only one of the ends of the membrane and of the mid-point is fixed, without any degree of freedom, in the frame, and - the converter comprises, between each anchoring point (262, 263; 276, 277) and the fixing point to which it is attached, a rigid arm (258, 259; 280, 281) tensioned between this anchoring point and this fixing point, this arm being suitable for transforming the displacement of the anchoring points into a displacement which deforms the piezoelectric membrane between its bent and less bent positions,