Motor drive circuit with emergency auxiliary power supply energized by motor

A motor drive circuit for a motor having a rotor and a stator including one or more stator windings, the motor drive circuit comprising:

• at least one voltage supply terminal,
• switching means coupled to said at least one voltage supply terminal and to said one or more stator windings,
• means for operating said switching means in a sequence so as to produce a rotating field in the motor that will interact with the rotor to rotate the motor,
• means for generating an emergency control signal when the voltage at the voltage supply terminal drops below a given voltage level,
• an auxiliary circuit adapted to be operated when the emergency control signal is generated,
• an auxiliary power supply circuit including a rectifier circuit coupled to at least one stator winding and the auxiliary circuit so that electric energy is transferred from the motor to the auxiliary circuit in response to the emergency control signal, and
• short-circuit means coupled to said at least one stator winding and controlled by said emergency control signal so as to intermittently short-circuit said at least one stator winding.

A motor drive circuit for a motor having a rotor and a stator including one or more stator windings, the motor drive circuit comprising:

• means for supplying an energizing voltage to said stator windings to operate the motor,
• means for generating an emergency control signal when the energizing voltage for said stator windings drops below a given voltage level,
• an auxiliary power supply circuit for extracting electric energy from the motor windings in response to the emergency control signal and supplying the extracted energy to an auxiliary circuit, the auxiliary power supply circuit comprising a rectifier circuit coupled between at least one stator winding and the auxiliary circuit, and
• short-circuit means coupled to said at least one stator winding and controlled by said emergency control signal so as to intermittently short-circuit said at least one stator winding thereby to derive from said one stator winding a relatively large voltage sufficient to operate said auxiliary circuit.