Brushless DC motor driven by complementary type transistors

A brushless d.c. motor having a rotor, a stationary motor winding (20), a rotor position sensor (25) and means, including a full bridge circuit, for providing to said winding from a d.c. current source (33,35), under control of said sensor, two current pulses per 360.degree. el. of rotation of said rotor and further comprising, in accordance with the invention:

• two transistors (47,48) of opposite conductivity type connected in series providing a first pair of adjacent arms of said bridge circuit and having their emitters respectively connected to opposite poles of said d.c. current source and having their collectors connected together and to a first terminal of said motor winding;
• two transistors (61,62) of opposite conductivity type connected in series providing a second pair of adjacent arms of said bridge circuit, having their respective collectors connected to said opposite poles of said d.c. current source and having their emitters connected together and to a second terminal of said motor winding;
• means, constituted at least in part by said sensor (25) and including semiconductor means, for producing a rotor position signal of large amplitude, a potential being supplied to said semiconductor means which is substantially equal to that of one pole (35) of said d.c. current source (33,35), and
• means for applying said rotor position signal (24) of large amplitude to the control electrodes of said transistors (47,48) providing said first pair of adjacent bridge arms through a resistance network (43;72) having a first resistance (46,75) connected between the output of said semiconductor means (25;70) and the control electrode of a first one (48) of said transistors of said first pair and a second resistance (44,73) connected between said output of said semiconductor means (25;70) and the control electrode of the second one (47) of said transistors of said first pair.