US 4,438,377 A · Stop control circuit for brushless DC motor

Abstract

A stop control circuit for a DC motor causes the motor to stop precisely by purely electrical action. A DC motor is provided with a bidirectional driving circuit, a servo circuit for controlling the driving circuit, and a rotation detector associated with the motor shaft to provide a phase signal that depends, in magnitude and polarity, on the particular rotational angle of the shaft, regardless whether the motor is turning. A stop control circuit then includes an amplifier whose output varies according to the phase signal, and a switch that normally provides the servo signal to the driving circuit, but, upon command, switches over to provide thereto the output of the amplifier as a brake signal. Alternatively the rotation detector can include two sensor elements separated by .pi./2, and the stop control circuit can include an inverting amplifier, a non-inverting amplifier coupled to one of the sensor elements, and a switch circuit with inputs coupled respectively to these amplifiers. A comparator provides a switch signal to the switch circuit in dependence on the phase signal from the other sensor element. In another embodiment, a differential amplifier provides a brake signal in dependence upon both the phase signals from the two sensor elements.

Claims15

Dependent claims

A drive control circuit for a brushless DC motor comprising bidirectional-rotation driving circuit means for applying current in either of two opposite directions to said motor;

servo circuit means providing a servo output signal for said driving circuit means to control the phase and speed of said motor;
rotation detecting means for providing a phase signal whose magnitude and polarity indicate the electrical rotational angle of said motor;
amplifier means amplifying said phase signal and providing an output voltage that varies according to said phase signal;
and controllable switching means having a first condition for normally providing said servo output signal to said driving circuit means, and a second condition for applying said output voltage to said driving circuit means in a sense to brake said motor.

1 more element

A drive control circuit for a brushless DC motor comprising bidirectional-rotation driving circuit means for applying current in either of two opposite directions to said motor;

servo circuit means providing a servo output signal for said driving circuit means to control the phase and speed of said motor;
first rotation, detecting means for providing a first phase signal whose magnitude and polarity indicate the electrical rotational angle of said motor;
second rotation detecting means for providing a second phase signal whose magnitude and polarity indicate an electrical rotational angle of said motor displaced by an electrical angle of an odd multiple of .pi./2 from that indicated by said first phase signal;
amplifier means amplifying said first phase signal and providing a first output voltage that varies with said first phase signal and a second output voltage that varies inversely therewith;
comparator means coupled to said second rotation detecting means for comparing said second phase signal with a reference level to provide a switching signal;
first switching means having inputs coupled to receive said first and second output voltages, and switched over by said switching signal to provide a switched output signal;
and second switching means having a first condition for normally providing said servo output signal to said driving circuit means, and a second condition for applying said switched output voltage to said driving circuit means to brake said motor.

4 more elements

A drive control circuit for a brushless DC motor comprising bidirectional-rotation driving circuit means for applying current in either of two opposite directions to said motor;

servo circuit means providing a servo output signal for said driving circuit means to control the phase and speed of said motor;
first rotation detecting means for providing a first phase signal whose magnitude and polarity indicates the electrical rotational angle of said motor;
second rotation detecting means for providing a second phase signal whose magnitude and polarity indicate an electrical rotational angle of said motor displaced by an electrical angle of an odd multiple of .pi./2 from that indicated by said first phase signal;
amplifier means coupled to receive said first and second phase signals and providing a first output voltage corresponding to the difference between said first and second phase signals and a second output voltage that varies inversely with said first output voltage;
comparator means coupled to said first and second rotation detecting means for comparing a sum of said first and second phase signals to a reference level and providing a switching signal;
first switching means having inputs coupled to receive said first and second output voltages and switched over by said switching signal to provide a switched output signal;
and second switching means having a first condition for normally providing said servo output signal to said driving circuit means, and a second condition for applying said switching output voltage to said driving circuit means to brake said motor.

4 more elements

Dependencies are inferred from the claim text.

Stop control circuit for brushless DC motor

Life of this patent

Stop control circuit for brushless DC motor

Life of this patent

Abstract

Claims15