Voltage converter comprising a plurality of two-directional conversion cells, each cell comprising: a primary circuit (307, Wp) and a secondary circuit (308, Ws) isolated from the primary circuit, the primary circuit and the secondary circuit respectively comprising a primary coiling (Wp) and a secondary coiling (Ws) coupled to one another; an input capacity element (C in) between first and second input terminals of the cell, on the primary circuit side; and activation switches (SW1, SW2) and a circuit for controlling the activation switches supplied by the voltage at the terminals of said input capacity element (C in), wherein: each cell can be activated or deactivated dynamically by way of the activation switches (SW1, SW2) thereof, so as to adjust the total transformation ratio of the converter; the primary circuits of the activated cells are connected in series; the primary circuit of the non-activated cells are isolated from the primary circuits of the activated cells; and the secondary circuits of the activated cells and of the non-activated cells are connected in parallel, the converter further comprising at least one control circuit configured to, in a first operating mode, simultaneously control the activated cells to transfer electrical energy from the primary circuit to the secondary circuit, and the non-activated cells to transfer electrical energy from the secondary circuit to the primary circuit. a primary circuit (307, Wp) and a secondary circuit (308, Ws) isolated from the primary circuit, the primary circuit and the secondary circuit respectively comprising a primary coiling (Wp) and a secondary coiling (Ws) coupled to one another; an input capacity element (C in) between first and second input terminals of the cell, on the primary circuit side; and activation switches (SW1, SW2) and a circuit for controlling the activation switches supplied by the voltage at the terminals of said input capacity element (C in), wherein: each cell can be activated or deactivated dynamically by way of the activation switches (SW1, SW2) thereof, so as to adjust the total transformation ratio of the converter; the primary circuits of the activated cells are connected in series; the primary circuit of the non-activated cells are isolated from the primary circuits of the activated cells; and the secondary circuits of the activated cells and of the non-activated cells are connected in parallel, each cell can be activated or deactivated dynamically by way of the activation switches (SW1, SW2) thereof, so as to adjust the total transformation ratio of the converter; the primary circuits of the activated cells are connected in series; the primary circuit of the non-activated cells are isolated from the primary circuits of the activated cells; and the secondary circuits of the activated cells and of the non-activated cells are connected in parallel, the converter further comprising at least one control circuit configured to, in a first operating mode, simultaneously control the activated cells to transfer electrical energy from the primary circuit to the secondary circuit, and the non-activated cells to transfer electrical energy from the secondary circuit to the primary circuit.