System for controlling a brushless electric motor

A system for controlling a brushless electric motor including a rotor, a stator, a plurality of stator windings disposed in the stator which are arranged in respective circuit branches and each of which is in series with a corresponding controlled electronic switch, the circuit branches being connected, at one end, to one pole of a direct-current voltage supply and, at the other end, to the other pole of the supply via an electronic regulation switch, the system comprising:

• a position sensor for supplying electrical signals indicative of the angular position of the rotor;
• a driver circuit arranged to control the controlled switches associated with the stator windings and the regulation switch in predetermined manner in dependence on the position signals emitted by the position sensor, the regulation switch being driven in an on/off manner by means of a square-wave signal;
• a capacitor connected to a control input of the regulation switch so that the capacitor is charged each time the regulation switch is made conductive by the square-wave signal in operation, and
• a control switch connected between the control input of the regulation switch and the other pole of the direct-current voltage supply and having a control input connected to the capacitor, and
• so that the control switch is made conductive and cuts off the regulation switch when the regulation switch remains conductive continuously for a period of time longer than a predetermined period.