GB2314471A

GB2314471A - Drive circuit for a brushless motor

Info

Publication number: GB2314471A
Application number: GB9612746A
Authority: GB
Inventors: Alex Horng
Original assignee: Sunonwealth Electric Machine Industry Co Ltd
Current assignee: Sunonwealth Electric Machine Industry Co Ltd
Priority date: 1996-06-19
Filing date: 1996-06-19
Publication date: 1997-12-24
Also published as: FR2751147A3; GB9612746D0; DE29611213U1; FR2751147B3

Abstract

A drive circuit for a brushless motor includes a main integrated circuit 1 including a logic circuit 11 which, in turn, includes at most three inputs 12, an enable input 13 , and at least two outputs 14. A Hall element (2, Figs 2-4) is connected to one of the inputs to activate the outputs to send out alternating pulses so as to make windings (3) of the motor alternately conduct to form a rotational magnetic field for driving a rotor of the motor to rotate. Where the motor has a high load current the outputs 16 from the integrated circuit 1 may be connected to high power transistors (4, Fig 3) which are connected to the motor windings (3).

Description

Drive Circuit for Brushless Direct-Current Motors The present invention relates to a drive circuit for brushless direct-current motors.

Fig. 5 of the drawings illustrates a conventional drive circuit for brushless direct-current motors in which, after the rotor of the motor begins to rotate, a change in polarity of N pole and S pole of a magnetic bar of the rotor can be sensed by a Hall element to activate a pulse integrated circuit (IC) "A" to send continuous pulse signals which, after passing through transistor "B", controls two post-stage transistors "C" and "D to conduct alternately, which, in turn, causes windings "E" and "F" which are connected to transistors "C" and "D" to conduct alternately.

The windings "E" and "F" are transverse to each other, thereby forming a rotational magnetic field to make the rotor continue to rotate.

However, this conventional drive circuit for brushless direct-current motors has several drawbacks: (1) an inverse voltage thereof may generate a current in the opposite direction such that a driving torque and speed of the motor are reduced; (2) an instantaneous start of the motor generates a considerable surge current and noise signals, which causes a high temperature in an inside of the rotor and in the circuit, and thus may damage the transistors and generate louder noise; (3) the characteristics of the parts of the circuit are different from each other and cannot be effectively controlled, particularly for the transistors which have a great distinction in the characteristics thereof, thereby resulting in an unbalance in the windings, which, in turn, causes abnormal circuit current to damage the Hall element and/or other parts; and (4) the circuit includes too many parts such that quality of the parts cannot be easily controlled and the processing cost is high for manufacture and assembly, and potential man-made errors are also increased.

Therefore, there has been a long and unfulfilled need for an improved drive circuit for brushless direct-current motors.

It is an object of the present invention to provide a novel drive circuit for brushless direct-current motors which uses a Hall element and a main integrated circuit to replace conventional drive circuits and mitigate and/or obviate the drawbacks of the conventional drive circuits.

A drive circuit for a brushless direct-current motor in accordance- with the present invention includes a main integrated circuit comprising a logic circuit, which, in turn, includes at most three inputs, an enable end, and at least two outputs. A Hall element is connected to one of the inputs to activate the outputs to send out alternating pulses so as to make windings of the motor alternately conduct to form a rotational magnetic field for driving a rotor of the motor to rotate.

Each output of the logic circuit may be electrIcally connected to a transistor which includes a collector working as an output pin for the main integrated circuit.

When used for a motor having a low load current, the two output pins of the main integrated circuit are electrically connected to the windings of the motor. When used for a motor having a high load current, a high power transistor is electrically connected to each output pin of the main integrated circuit, and the high power transistor includes an output electrically connected to the windings of the motor.

In an alternative embodiment of the invention, the Hall element includes two outputs which are electrically connected to the remaining inputs of the main integrated circuit, and the output pins of the main integrated circuit are electrically connected to the windings of the motor.

The enable end of the main integrated circuit may be controlled by external signals to force the motor to rotate or stop.

Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

In the drawings: Fig. 1 is a circuitry of a main integrated circuit of a drive circuit for brushless direct-current motors in accordance with the present invention; Fig. 2 is a circuitry illustrating a drive circuit for brushless direct-current motors in accordance with the present invention used for a motor having a low current loading; Fig. 3 is a circuitry illustrating a drive circuit for brushless direct-current motors in accordance with the present invention used for a motor having a high current loading; Fig. 4 is a modified embodiment of Fig. 2; and Fig. 5 is a circuitry illustrating a drive circuit for brushless direct-current motors according to prior art.

Referring to Figs. 1 to 4 and initially to Fig. 1, a drive circuit for brushless direct-current motors in accordance with the present invention comprises a main integrated circuit (IC) 1 which, in turn, comprises a logic circuit 11 including at most three inputs 12, an enable end 13, and at least two outputs 14. Each output 14 is electrically connected to a transistor 15 which amplifies an outputted pulse, a collector of the transistor 15 working as an output pin 16 for the main IC 1.

Referring to Fig. 2, when the main IC 1 is applied to a motor having a low load current, one of the input ends 12 of the main IC 1 is electrically connected to a Hall element 2, and the two output pins 16 of the main IC 1 are directly electrically connected to two windings 3, respectively. The Hall element 2 senses a change in the polarity of a rotor of the motor and thus activates the main IC 1 to output continuous pulses to make the windings 3 of the rotor of the motor to be alternately conducted, thereby forming a rotational magnetic field to keep the rotor rotating.

The main IC 1 in Fig. 3 is applied to a large brushless direct-current motor having a high load current.

Since the large brushless direct-current motor needs a greater capacity for current, each output pin 16 of main IC 1 is electrically connected to a transistor 4 having a higher power and then connected to the windings 3 of the motor such that the pulses outputted by the main IC 1, after being amplified by the transistor 4, generate a larger current to activate the windings for forming a rotational magnetic field with a greater torque for driving the rotor of the motor.

Fig. 4 illustrates a modified embodiment of Fig. 2 in which two outputs of the Hall element 2 are electrically connected to two of the inputs 12 of the main IC 1, respectively, and each output 16 of the main IC 1 is electrically connected to the windings 3 such that the Hall element 2 may respond to all kinds of situations to drive or stop the motor.

It is appreciated that the drive circuit of the present invention may clear off inverse voltage and avoids a reduction in the torque of motor and rotational speed without provision of Zener diodes and/or capacitors required in conventional drive circuits. In addition, the drive circuit of the present invention may reduce surge current and noise signals. Furthermore, no abnormal circuit current can be generated to damage the Hall element. It is further appreciated that the drive circuit of the present invention is low in cost and has a simple structure and thus relatively reduces man-made errors. Additionally, the enable end of the main IC can be controlled by external signals responsive to different kinds of situations to force the motor to rotate or stop so as to make the motor more applicable. The main IC of the present invention includes a protective design and thus can avoid from being damaged by inverse voltages.

Furthermore, high power transistors can be added into the drive circuit of the present invention to drive motors of higher power.

Although the invention has been explained in relation to its preferred embodiment, it is to be understood that many other possible modifications and variations can be made without departing - from the scope of the invention as hereinafter claimed.

Claims

CLAIMS:

1. A drive circuit for a brushless direct-current motor having a rotor and windings, comprising: a main integrated circuit comprising a logic circuit including at most three inputs, an enable end, and at least two outputs, a Hall element being connected to one of the inputs to activate the outputs to send out alternating pulses so as to make the windings of the motor alternately conduct to form a rotational magnetic field for driving the rotor of the motor to rotate.

2. The drive circuit as claimed in claim 1, wherein each said output of the logic circuit is electrically connected to a transistor, the transistor includes a collector which works as an output pin for the main integrated circuit.

3. The drive circuit as claimed in claim 2, wherein the motor has a low load current, and the two output pins of the main integrated circuit are electrically connected to the windings of the motor.

4. The'drive circuit as claimed in claim 2, wherein the motor has a high load current, and further includes a high power transistor electrically connected to each said output pin of the main integrated circuit, and the high power transistor includes an output electrically connected to the windings of the motor.

5. The drive circuit as claimed in any preceding claim, wherein the Hall element includes two outputs which are electrically connected to the remaining inputs of the main integrated circuit, and the output pins of the main integrated circuit are electrically connected to the windings of the motor.

6. The drive circuit as claimed in any preceding claim, wherein the enable end of the main integrated circuit is controlled by external signals to force the motor to rotate or stop.

7. An electronic controller for a brushless direct-current motor, the controller comprising an integrated circuit having a logic section for generating electrical pulses and a power output section responsive to said electrical pulses for driving said motor.

8. An electronic controller as claimed in claim 7 in combination with a Hall-effect sensor.

9. The drive circuit or electronic controller substantially as hereinbefore described with reference to and as shown in Figs. 1 to 4 of the accompanying drawings.