Drive circuit for a permanent magnet motor

A drive circuit for an electric motor comprising a stator and a permanent magnet rotor rotatable with respect to the stator, the stator comprising a stator core and a stator coil wound on the stator core, the drive circuit comprising:

• a controllable bidirectional AC switch connected in series with the stator coil between two terminals for connecting to an AC power supply;
• a first position sensor and a second position sensor for detecting positions of the magnetic poles of the permanent magnet rotor;
• and
• a voltage regulating circuit connected between the two terminals and the controllable bidirectional AC switch and configured to supply power to the first sensor during a positive cycle of the AC power supply and to the second position sensor during a negative cycle of the AC power supply such that the controllable bidirectional AC switch is switched between a conductive state and a non-conductive state in a predetermined manner, thus enabling the stator coil to urge the rotor only in a fixed direction during start-up of the motor.