The invention relates to an electronic driving device (20) for turning on and off a synchronous pump, that is a pump (15) comprising a synchronous electric motor (1) with a permanent-magnet rotor (8), comprising:--at least a static power switch (17) inserted in series between the motor (1) and an AC electric power supply source (Vp); and--a processing unit (16) having at least an input receiving a synchronism signal (V) and a control output connected to said switch (17); characterized in that it is enabled by a signal emitted by a float level sensor (40) and includes an input receiving a signal (a) by a position sensor (21) detecting the rotor (8) polarity and position; the pump turn-on and off being regulated according to the signal emitted by said level sensor (40) and to a measured difference between a critical load angle (8) and a current load angle computed during different working conditions of the pump.