Electronic controlling device for controlling an electrical energy converter capable of converting one or more input voltages into one or more output voltages, the converter being 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, the converter comprising a piezoelectric element and several switches (K 1, K 2, K 3, K 4, K 5), the electronic control device comprising a control module configured to control, during a respective resonance cycle of the piezoelectric element, a switching of each of the switches (K 1, K 2, K 3, K 4, K 5) to alternate phases (II, IV, VI, VIII) at substantially constant voltage at the terminals (30, 34) of the piezoelectric element and phases (I, III, V, VII) at substantially constant charge at the terminals (30, 34) of said piezoelectric element, each resonance cycle comprising first and second half-cycles, a current (I L) flowing in a first direction in the piezoelectric element during the first half-cycle and in a second direction, opposite to the first direction, during the second half-cycle, where by substantially constant voltage is meant a voltage variation of less than 20%, preferably less than 10%, of the input or output voltage of converter, and by substantially constant charge is meant an exchange of a charge with the outside which is less than 10% of the charge which would have been exchanged with the outside if the voltage had been kept constant, the number (M V) of phases (II, IV, VI, VIII) at substantially constant voltage during a respective resonance cycle being greater than or equal to the sum of E, N and two, and each of the first and second half-cycles comprising at least two phases (II, IV; VI, VIII) at substantially constant voltage, and characterized in that the value (V buffer) of the voltage of one of the phases (II, IV, VI, VIII) at substantially constant voltage during the first half-cycle is substantially equal to the value (V a, V c) of the voltage of one of the phases (II, IV, VI, VIII) at substantially constant voltage during the second half-cycle, where the expression "substantially equal to" defines a relation of equality at plus or minus 10%, preferably at plus or minus 5%. the electronic control device comprising a control module configured to control, during a respective resonance cycle of the piezoelectric element, a switching of each of the switches (K 1, K 2, K 3, K 4, K 5) to alternate phases (II, IV, VI, VIII) at substantially constant voltage at the terminals (30, 34) of the piezoelectric element and phases (I, III, V, VII) at substantially constant charge at the terminals (30, 34) of said piezoelectric element, each resonance cycle comprising first and second half-cycles, a current (I L) flowing in a first direction in the piezoelectric element during the first half-cycle and in a second direction, opposite to the first direction, during the second half-cycle, where by substantially constant voltage is meant a voltage variation of less than 20%, preferably less than 10%, of the input or output voltage of converter, and by substantially constant charge is meant an exchange of a charge with the outside which is less than 10% of the charge which would have been exchanged with the outside if the voltage had been kept constant, the number (M V) of phases (II, IV, VI, VIII) at substantially constant voltage during a respective resonance cycle being greater than or equal to the sum of E, N and two, and each of the first and second half-cycles comprising at least two phases (II, IV; VI, VIII) at substantially constant voltage, and characterized in that the value (V buffer) of the voltage of one of the phases (II, IV, VI, VIII) at substantially constant voltage during the first half-cycle is substantially equal to the value (V a, V c) of the voltage of one of the phases (II, IV, VI, VIII) at substantially constant voltage during the second half-cycle, where the expression "substantially equal to" defines a relation of equality at plus or minus 10%, preferably at plus or minus 5%.