Low voltage start up circuit for brushless dc motors
AssigneeMelexis NV
InventorsHideki Ted Kawaji, Mark R. White
Life of this patent
Estimating the term…
Abstract
A local oscillator and logic circuit pulses the open winding of a brushless DC motor at start up and uses the back EMF to generate a voltage to boost the voltage available to the control circuit for optimizing performance when starting with low supply voltage.
Claims19
A circuit arrangement for driving at low voltage a brushless dc motor having a rotor and at least two windings for driving one or more permanent magnets on the rotor, the arrangement comprising:
- drive circuits configured to provide drive signals to the windings;
- one or more sensors arranged to determine the rotational position of the rotor;
- an analogue processing circuit configured to process signals received from the one or more sensors so as to provide a feedback signal;
- a regulation circuit configured to extract energy from inductive voltages produced by the windings and to generate a voltage power source for the processing circuit;
- an oscillator circuit configured to provide a pulse signal;
- and
- a control circuit configured to receive the feedback signal and the pulse signal, the control circuit being further configured to control the drive circuits such that:
- in a first mode of operation, when the rotor is turning, the drive circuits are selectively enabled based on the feedback signal;
- and
- in a second mode of operation, when the rotor is not turning, the drive circuits are pulsed based on the pulse signal so as to generate inductive voltages in the windings.
A system for driving at low voltage a brushless dc motor having a rotor and at least two windings, the system comprising:
- driving means for driving the individual windings on the dc motor so as to rotate the rotor;
- sensor means for determining the rotational position of the rotor;
- analogue interface circuitry for interfacing to the sensor circuits and providing a feedback signal based on signals received from the sensor means;
- regulation circuitry configured to extract energy from the inductive voltages produced by the windings and to generate a high voltage power source for the analogue interface circuitry;
- means for providing a pulse signal;
- and
- control means coupled to the analogue interface circuitry for controlling the driving means such that when the motor is turning the drive circuits are selectively enabled by timing determined from the feedback signal, and when the motor is not turning the drive means are pulsed in time based on the pulse signal such as to generate inductive voltages on the windings when they would otherwise be not present.
A method of driving a brushless dc motor having a rotor and at least two windings configured to drive one or more permanent magnets coupled to the rotor, the method comprising:
- generating pulsed drive signals using drive circuits connected to the windings so as to rotate the rotor and thereby generate inductive voltage signals in the windings;
- generating a high voltage power source using the inductive voltage signals generated by the windings;
- and thereafter
- sensing the rotational position of the rotor using one or more sensors;
- processing signals provided by the one or more sensors using an analogue processing circuit so as to produce a feedback signal, said analogue processing circuit being powered by said high voltage power source;
- and
- selectively powering the drive circuits based on the feedback signal so as to rotate the rotor in a continuous manner.
Dependencies are inferred from the claim text.