Brushless pulsed D.C. motor
First Claim
1. A commutated brushless dc motor comprising a stator with a plurality of circumferentially spaced stator windings, a rotor coupled to said stator and rotatably mounted to rotate relative to said stator winding as the result of energization of said windings, a dc power supply to establish pulsed energization of said windings in sequence with at least one winding de-energized, an alternating current induced signal being induced in said de-energized winding and having periodic zero crossings, a timing device coupled to the stator to monitor the time between the zero crossings of said induced signal and generating an electrical zero crossing signal proportional to such time, a signal latch unit coupled to said timing device and storing the zero crossing signal as a latched signal, a reset unit connected to said timing device to initiate a new timing cycle to generate a next zero crossing signal, and a comparator connected to said timing device and said latch unit and responsive to a proportion of the latched signal to generate said pulsed energization of said windings in a continuous repetitive sequence.
1 Assignment
0 Petitions
Accused Products
Abstract
A commutated brushless dc motor includes a detector which senses the zero crossings of the unenergized winding. A timing system includes a reference capacitor coupled to the detection unit and charged to a voltage proportional to zero crossing time. The voltage is compared to a capacitor charged from a constant current source. At a percentage level of the reference capacitor, a commutating pulse is applied to a winding commutating circuit. The incoming pulses drive a counter and actuates a programmed decoder which generates output signals for commutation of the windings and selection of the next unenergized winding. The detector is selectively connected to sense the induced voltage in the unenergized winding. To start the motor, a separate charging circuit creates initial pulses to energize the windings and accelerate the motor. At a given speed, the zero crossing circuit is enabled. An integrated circuit system has the zero crossing signals applied to a resettable counter which counts at a fixed rate between zero crossings. The count is latched and is proportional to the time between zero crossings. The counter signal and the latched signal are compared to generate the commutating pulse.
-
Citations
16 Claims
- 1. A commutated brushless dc motor comprising a stator with a plurality of circumferentially spaced stator windings, a rotor coupled to said stator and rotatably mounted to rotate relative to said stator winding as the result of energization of said windings, a dc power supply to establish pulsed energization of said windings in sequence with at least one winding de-energized, an alternating current induced signal being induced in said de-energized winding and having periodic zero crossings, a timing device coupled to the stator to monitor the time between the zero crossings of said induced signal and generating an electrical zero crossing signal proportional to such time, a signal latch unit coupled to said timing device and storing the zero crossing signal as a latched signal, a reset unit connected to said timing device to initiate a new timing cycle to generate a next zero crossing signal, and a comparator connected to said timing device and said latch unit and responsive to a proportion of the latched signal to generate said pulsed energization of said windings in a continuous repetitive sequence.
- 7. A brushless dc motor having a rotor and a stator with at least three equicircumferentially spaced windings connected in a wye configuration in with a common center line and connected to a switched dc power supply and having separate switch units for selectively energizing said windings and thereby causing rotation of said rotor, said rotation of said rotor inducing an induced electrical signal in said windings, comprising a sensor coupled to said windings and responsive to a zero crossing of the induced electrical signal in said windings, a signal generator creating a control signal having a characteristic varying from a reference level proportionately with time, said signal generator including a reset unit for resetting said generator to said reference level, a control reference unit connected to said signal generator and set to correspond to said control signal and having an output corresponding to a selected percentage of the control signal, a trigger signal source connected to the output of said control reference unit and to said signal generator operable to establish a switching signals with said signal generator at a signal output equal to said selected percentage of said control signal, and said sensor being connected to said signal generator and operable to reset said signal generator at each of said zero crossings and thereby repetitively establish said control signal proportional to the period between successive zero crossing, and a circuit for connecting of said trigger signal source to said separate switch units and thereby establish sequential actuation of said separate switch units and pulsed energization of said windings.
-
11. A controlled power supply for energizing a brushless dc motor having a rotor with circumferentially spaced magnetic poles and a stator with circumferentially spaced windings, comprising a switching device connected to said windings and having a plurality of input controls for sequentially energizing said windings and establishing an interacting magnetic field sequentially stepped about said rotor and thereby establishing rotation of said rotor, at least one of said windings being de-energized and having an induced signal induced therein as a result of the rotation of said rotor, said induced signal varying in a periodic manner with spaced zero crossings in accordance with the rotation of said rotor, a detector coupled to said windings and sequentially operably coupled to the de-energized windings to sense the induced signal in successive windings and thereby the position of the rotor relative to the stator, a timing device connected to said detector and generating a control signal directly proportionally to the period between said zero crossings, a signal dividing unit connected to said timing device and generating a fixed percentage signal for each successive control signal, a comparator connected to the signal dividing unit and to the timing device and generating a trigger signal with said control signal being equal to said fixed percentage signal, and a controller connecting said comparator to said input controls to actuate the switching device to sequentially energize the windings in response to the sequence of said trigger signals.
- 12. A brushless dc motor having a permanent magnet rotor and a stator with a plurality of equicircumferentially spaced windings having one inner end of the windings connected to a common line and each of the outer ends of the winding connected to a dc power supply, said windings being sequentially energized with dc power positively supplied to one of said windings and returned to said supply through a second of said windings, and said positive power being sequentially applied to said windings in one direction for forward rotation of said motor and in a reverse direction for reverse rotation of said motor, said rotor inducing an alternating sinusoidal induced voltage in the unenergized winding to be next energized, said induced voltage having two zero crossings in each voltage cycle, the improvement in a control for switching of said power supply to said windings, comprising a zero crossing detecting network connected to said windings for detecting the zero crossing of each induced voltage in said unenergized winding, a voltage reference line, said detecting network including a resistive coupling network including a separate first voltage resistor dividing branch connected to the end of each winding and to said voltage reference line and including a second voltage resistor dividing branch connected to said common line connection and said voltage reference line, a gate unit connected to each of said resistor dividing branches, said gate unit having a common output line, a first comparator amplifier having first input connected to said common output line and having a second input connected via the second voltage resistor dividing branch to said common line connection, an inverted amplifier to invert the output signal of said first comparator amplifier, a second comparator amplifier having a first input connected to said voltage reference line and having a second input, first and second transfer switches connecting said first comparator amplifier and said inverter amplifier to said second input of said second comparator amplifier, three detection switches connected one each to each of the first voltage resistor dividing branches, first and second transfer switches, a programmer coupled to sequentially actuate said three detection switches in sequence to sequentially couple the output of the windings to said first comparator amplifier and to alternately actuate said first and second transfer switches for alternately actuating such first and second transfer switches to establish a positive input signal to said second comparator amplifier and thereby generate a pulse output signal at each zero crossing of the unenergized winding and establishing a series of pulse signals precisely identifying the zero crossing points in the sinusoidal induced voltage in the unenergized winding and thereby the position of said rotor relative to said stator windings, a measurement and timing circuit including a timing device to create a time signal proportional to the period between successive zero crossing in said unenergized windings, a storage device to store the time signal and including a proportional output element to establish a reference signal equal to a percentage of said time signal which equals to the period between the last zero crossing and the next winding energization, a trigger comparator connected to said timing device and to said storage device and establishing a switching signal to said programmer in response to the input of said time signal and said reference signal.
Specification