Brushless DC motor drive apparatus

• US 5,780,983 A
• Filed: 03/27/1996
• Issued: 07/14/1998
• Est. Priority Date: 03/15/1994
• Status: Expired due to Term

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Shinkawa, Osamu, Uetake, Akihito
• Primary Examiner(s): Martin, David S.
• Application Number:
  US08/623,347
• Time in Patent Office: 839 Days
• Field of Search: 318/254, 318/138, 318/439
• US Class Current: 318/400.04
• CPC Class Codes: H02P 6/085 in a bridge configuration
• CPC Class Codes: H02P 6/182 using back-emf in windings

Abstract

A brushless DC motor drive apparatus according to the invention comprises a stator and a rotor, the stator including multi-phase armature windings which are connected in a star formation and generate a plurality of terminal voltages at respective terminals of the armature windings, and the rotor including a plurality of permanent magnets which form pairs of magnetic poles. The motor drive apparatus also includes an inverter coupled to the rotor for adjusting the speed of the rotor, a rotor position detection means for detecting the terminal voltages generated in the armature windings and for generating a position signal indicative of a magnetic pole position of the rotor. The rotor position detection means includes a line voltage generation means for generating line voltages corresponding to the terminal voltages of the armature windings and comparison means for comparing signals derived from the line voltages in predetermined combinations and outputting comparison signals as the positional signal. The motor drive apparatus also includes a drive control means for controlling and driving the inverter according to the position signal generated by the rotor position detection means, the drive control means including PWM (Pulse Width Modulation) chopper control means for generating a PWM chopper control signal to control the inverter. The motor drive apparatus according to the present invention can always detect accurate rotor position without being affected by the rotational frequency or load of the brushless DC motor. Furthermore, the motor drive apparatus can easily expand the operational range of a brushless DC motor, particularly that of a brushless DC motor possessing an embedded magnet-type rotor structure. Additionally, the motor drive apparatus can easily and accurately operate a brushless DC motor according to its motor characteristics and control method.

Claims

1. A brushless DC motor drive apparatus, comprising:

a motor including;

a stator including multi-phase armature windings which are connected in a star formation and generate a plurality of terminal voltages at respective terminals of the armature windings, and

a rotor including a plurality of permanent magnets which form pairs of magnetic poles;

an inverter, coupled to said stator, for adjusting a speed of said rotor;

rotor position detection means for detecting the terminal voltages generated in said armature windings and for generating a position signal indicative of a magnetic pole position of said rotor, said rotor position detection means including line voltage generation means for generating line voltages corresponding to the terminal voltages of said armature windings and comparison means for comparing each one of said line voltages to an amplification of another predetermined one of said line voltages and outputting comparison signals as the position signal; and

drive control means for controlling and driving said inverter according to the position signal generated by said rotor position detection means, said drive control means including PWM (Pulse Width Modulation) chopper control means for generating a PWM chopper control signal to control said inverter.

2. The brushless DC motor drive apparatus of claim 1 wherein said drive control means further includes:

chop-on detection means for detecting the comparison signals from said comparison means of said rotor position detection means synchronously with a chop-on timing of the PWM chopper control signal from said PWM chopper control means and generating data signals;

open phase selection means for selecting an open phase signal from among the data signals output by said chop-on detection means during an open phase; and

edge-detection means for detecting predetermined edges of the open phase signal output by said open phase selection means.

3. The brushless DC motor drive apparatus of claim 1 wherein said drive control means further includes commutation control means for supplying a commutation signal after said rotor position detection means detects a predetermined magnetic pole position of said rotor and said rotor rotates by a predetermined phase shift.

4. The brushless DC motor drive apparatus of claim 1 wherein said drive control means further includes commutation control means for supplying a commutation signal synchronously with detection of a predetermined magnetic pole position of said rotor by said rotor position detection means.

5. The brushless DC motor drive apparatus of claim 1 wherein said drive control means further includes commutation control means for supplying a commutation signal after said rotor position detection means detects a predetermined magnetic pole position of said rotor and said rotor rotates by a predetermined phase shift.

6. The brushless DC motor drive apparatus of claim 1 wherein a phase angle of a current flowing through said stator armature windings relative to a q axis in a d-q coordinate system is defined as current phase angle θ

, and said rotor position detection means detects a predetermined magnetic pole position of said rotor when said current phase angle θ

advances by an electrical angle of not more than 30°

.

7. The brushless DC motor drive apparatus of claim 1 wherein said line voltage generation means includes an isolation amplifier.

8. The brushless DC motor drive apparatus of claim 1 wherein said line voltage generation means includes:

first line voltage generation means for generating a first line voltage,

second line voltage generation means for generating a second line voltage, and

third line voltage generation means for generating a third line voltage based on the first line voltage and the second line voltage.

9. The brushless DC motor drive apparatus of claim 8 wherein said first line voltage generation means and said second line voltage generation means each include an isolation amplifier.

10. A brushless DC motor drive apparatus, comprising:

a motor including;

a stator including 3-phase armature windings U, V, and W which are connected in a star formation and generate a plurality of terminal voltages at respective terminals of the armature windings, and

a rotor including a plurality of permanent magnets which form pairs of magnetic poles;

an inverter with a conducting interval of 120°

, coupled to said stator, for adjusting a speed of said rotor;

rotor position detection means for detecting the terminal voltages generated in said stator armature windings and for generating a position signal indicative of a magnetic pole position of said rotor, said rotor position detection means including;

line voltage generation means for generating line voltages corresponding to the terminal voltages of said armature windings,

amplification means for amplifying the line voltages and outputting amplified signals, and

comparison means for comparing the line voltages and the amplified signals according to predetermined combinations and outputting comparison signals as the position signal; and

drive control means for controlling and driving said inverter according to the position signal generated by said rotor position detection means, said drive control means including PWM (Pulse Width Modulation) chopper control means for generating a PWM chopper control signal to control said inverter;

wherein said line voltage generation means of said rotor position detection means comprises;

first line voltage generation means for generating a line voltage Vw-u between armature windings W and U,

second line voltage generation means for generating a line voltage Vu-v between armature windings U and V, and

third line voltage generation means for generating a line voltage Vv-w between armature windings V and W;

wherein said amplification means of said rotor position detection means comprises;

first amplification means for amplifying a signal derived from line voltage Vw-u output by said first line voltage generation means and outputting a first amplified signal,

second amplification means for amplifying a signal derived from line voltage Vu-v output by said second line voltage generation means and outputting a second amplified signal, and

third amplification means for amplifying a signal derived from line voltage Vv-w output by said third line voltage generation means and outputting a third amplified signal;

wherein said comparison means of said rotor position detection means comprises;

first comparison means for comparing the signal derived from said line voltage Vw-u with the second amplified signal output by said second amplification means, and outputting a first comparison signal,

second comparison means for comparing the signal derived from said line voltage Vu-v with the third amplified signal output by said third amplification means, and outputting a second comparison signal, and

third comparison means for comparing the signal derived from said line voltage Vv-w with the first amplified signal output by said first amplification means, and outputting a third comparison signal;

wherein the position signal generated by said rotor position detection means includes the first, second and third comparison signals.

11. The brushless DC motor drive apparatus of claim 10 wherein a phase angle of a current flowing through said armature windings relative to a q axis in a d-q coordinate system is defined as current phase angle θ

, and said rotor position detection means detects a predetermined magnetic pole position of said rotor when said current phase angle θ

has advanced by an electrical angle of not less than 30°

.

12. The brushless DC motor drive apparatus of claim 10 wherein said first comparison means outputs a high-level signal when the signal derived from said line voltage Vw-u is larger than the second amplified signal output by said second amplification means, said second comparison means outputs a high-level signal when the signal derived from said line voltage Vu-v is larger than the third amplified signal output by said third amplification means, and said third comparison means outputs a high-level signal when the signal derived from said line voltage Vv-w is larger than the first amplified signal output by said first amplification means.

13. The brushless DC motor drive apparatus of claim 10, further comprising:

first, second, and third gain switching means for switching a gain of said first, second, and third amplification means respectively into two stages;

wherein said rotor position detection means includes application voltage determination means for detecting a voltage applied to said motor.

14. The brushless DC motor drive apparatus of claim 13 wherein said application voltage determination means includes hysteresis means for changing an operation timing of said first, second, and third gain switching means according to specified criteria depending on rise and fall of the voltage applied to said motor.

15. The brushless DC motor drive apparatus of claim 10 wherein said rotor position detection means includes n application voltage determination means for detecting a voltage applied to said motor, n being an integer of at least 2;

the brushless DC motor drive apparatus further comprising;

n gain switching means for changing a gain of said first, second, and third amplification means based on signals generated from associated application voltage determination means.

16. The brushless DC motor drive apparatus of claim 10 wherein said drive control means further includes:

chop-on detection means for detecting the comparison signals from said comparison means of said rotor position detection means synchronously with a chop-on timing of the PWM chopper control signal from said PWM chopper control means and generating data signals;

open phase selection means for selecting an open phase signal from among the data signals output by said chop-on detection means during an open phase; and

edge-detection means for detecting predetermined edges of the open phase signal output by said open phase selection means.

17. The brushless DC motor drive apparatus of claim 16 wherein said drive control means further includes:

commutation control means for supplying a commutation signal after said rotor position detection means detects a predetermined magnetic pole position of said rotor and said rotor rotates by a predetermined phase shift, and

shift setting means for setting said phase shift.

18. The brushless DC motor drive apparatus of claim 10 wherein said drive control means further includes commutation control means for supplying a commutation signal synchronously with detection of a predetermined magnetic pole position of said rotor by said rotor position detection means.

19. The brushless DC motor drive apparatus of claim 10 wherein said drive control means further includes commutation control means for supplying a commutation signal after said rotor position detection means detects a predetermined magnetic pole position of said rotor and said rotor rotates by a predetermined phase shift.

20. The brushless DC motor drive apparatus of claim 19 wherein said drive control means further includes shift setting means for setting said phase shift.

21. The brushless DC motor drive apparatus of claim 20 wherein said shift setting means sets said phase shift according to at least a rotation count of said rotor.

22. The brushless DC motor drive apparatus of claim 20 wherein said shift setting means sets said phase shift according to a rotation count of said rotor and a motor current.

23. The brushless DC motor drive apparatus of claim 10 wherein said rotor exhibits reverse saliency.

24. The brushless DC motor drive apparatus of claim 23 wherein said rotor includes a yoke having slots formed therein at positions corresponding to magnetic poles, and said permanent magnets are inserted in the slots so that said permanent magnets are not exposed to an exterior perimeter of said rotor.