System for converting a first electric voltage into a second electric voltage, of the type comprising: - at least two input terminals and two output terminals, - switching members arranged between the input terminals and the output terminals and able to convert the first voltage into the second voltage, and - a device for controlling the switching members, said control device comprising a cell for controlling a respective switching member and a member for managing and supplying the control cell, said management and supply member being connected to the control cell via a link allowing the simultaneous transmission of a control signal and electrical energy, characterised in that: - the management and supply member comprises means for generating a pulse comprising at least one first control interval for allowing establishment of the current circulating in the link between the management member and the control cells, a second control interval corresponding to maintaining the current, and a transition interval corresponding to return of the current to a value of zero, the pulse during the second control interval having a substantially constant value different from a reference value corresponding to the absence of control, the value of the pulse (U1, U2) being different from one control interval to another, and the pulse during the first control interval having a value which is strictly greater than that during the second control interval; - the system comprises at least one group of switching members connected in series, the or each group being connected between a corresponding output terminal and an input terminal, a respective control cell being associated with each switching member, wherein a single management and supply member is provided for the control cells of the switching members of a same group and is able to manage the plurality of control cells of the switching members of the group; and - the control device also comprises electrical isolation means arranged between each control cell and the management and supply member, wherein the electrical isolation means comprise, for each group of switching members, a plurality of secondary windings, a plurality of magnetic circuits and a single primary winding, each secondary winding being electrically connected to the input of a respective control cell and wound around a respective magnetic circuit, the single primary winding being wound around each of the circuits and electrically connected to the output from the single management and supply member. - at least two input terminals and two output terminals, - switching members arranged between the input terminals and the output terminals and able to convert the first voltage into the second voltage, and - a device for controlling the switching members, said control device comprising a cell for controlling a respective switching member and a member for managing and supplying the control cell, said management and supply member being connected to the control cell via a link allowing the simultaneous transmission of a control signal and electrical energy, - the management and supply member comprises means for generating a pulse comprising at least one first control interval for allowing establishment of the current circulating in the link between the management member and the control cells, a second control interval corresponding to maintaining the current, and a transition interval corresponding to return of the current to a value of zero, the pulse during the second control interval having a substantially constant value different from a reference value corresponding to the absence of control, the value of the pulse (U1, U2) being different from one control interval to another, and the pulse during the first control interval having a value which is strictly greater than that during the second control interval; - the system comprises at least one group of switching members connected in series, the or each group being connected between a corresponding output terminal and an input terminal, a respective control cell being associated with each switching member, wherein a single management and supply member is provided for the control cells of the switching members of a same group and is able to manage the plurality of control cells of the switching members of the group; and - the control device also comprises electrical isolation means arranged between each control cell and the management and supply member, wherein the electrical isolation means comprise, for each group of switching members, a plurality of secondary windings, a plurality of magnetic circuits and a single primary winding, each secondary winding being electrically connected to the input of a respective control cell and wound around a respective magnetic circuit, the single primary winding being wound around each of the circuits and electrically connected to the output from the single management and supply member.