The invention concerns an electric converter for fuel cell (P) comprising current inverter means (2), the electric converter comprising a voltage step-down chopper (1) mounted between the fuel cell (P) and the current inverter means (2), wherein, under the action of a command signal applied to the voltage step-down chopper (1): the value of the mean voltage at the input of the current inverter means is lowered to a threshold value (Vs) in the cell electrode activation zone, the value of the mean voltage at the input of the current inverter means (2) is maintained at the voltage value at the cell terminals (Vp) in the cell resistance zone, and the output current of the converter is limited when the output current from the current inverter means (2) reaches a maximum set value (Imax).