Single coil, direct current permanent magnet brushless motor with voltage boost

• US 6,850,019 B2
• Filed: 06/12/2003
• Issued: 02/01/2005
• Est. Priority Date: 06/12/2003
• Status: Expired due to Term

• Current Assignee: Mcmillan Electric Company
• Original Assignee: Mcmillan Electric Company
• Inventors: Gerfast, Sten R.
• Primary Examiner(s): Leykin, Rita
• Application Number:
  US10/462,008
• Publication Number:
  US 20040251859A1
• Time in Patent Office: 600 Days
• Field of Search: 318/254, 318/138, 318/439, 318/700, 318/701, 318/724, 310/156, 310/254
• US Class Current: 318/400.29
• CPC Class Codes: H02P 6/085 in a bridge configuration

Abstract

A single coil, direct current permanent magnet brushless motor including a stator including six alternately-wound coils connected into a single coil having first and second ends, the oppositely-wound coils forming stator poles, and six magnets of alternating polarity coupled to a rotor and rotatably journaled in the stator. A sensor, such as a dual output Hall sensor, is used for sensing rotation of the rotor. A drive circuit, such as an H-bridge circuit, is coupled to the first and second ends of the single coil to drive the motor. The H-bridge circuit includes two high-side switches for alternately receiving signals from the Hall sensor, and two low-side switches alternately receiving signals from the Hall sensor. A high-side switching signal can be controlled by an inverted low-side switching signal. A voltage boost circuit is also provided, having capacitors to provide a boosted voltage to alternately turn on the high-side switches of the H-bridge. The capacitors can be charged by an unregulated bus voltage.

Claims

1. A single coil, direct current permanent magnet brushless motor, comprising:

a rotor with at least four alternate polarity magnets rotatably journaled in the motor;

a stator with a like number of salient poles, each including alternately wound coils coupled to form a single coil with two free ends; and

a commutated H-bridge including a voltage boost circuit having capacitors providing a boosted voltage to alternately turn on high-side switches of the H-bridge, wherein the capacitors are charged by a low-side switching signal flowing through low-side switches.

2. The motor of claim 1, wherein a high-side switching signal is controlled by inverting the low-side switching signal.

3. The motor of claim 1, wherein the capacitors are charged by an unregulated bus voltage.

4. The motor of claim 1, wherein the motor includes six alternate-polarity magnets and six coils connected into the single coil.

5. The motor of claim 1, wherein the H-bridge further includes an alternating current conversion circuit including a bridge rectifier and smoothing capacitor coupled to a source of alternating current, the conversion circuit converting the alternating current to provide direct current to power the motor.

6. The motor of claim 1, wherein the motor is configured to be powered by either alternating current or direct current.

7. The motor of claim 1, further comprising a microcontroller to commutate the H-bridge.

8. The motor of claim 1, wherein a uniform concentric air gap is defined between the stator and the rotor.

9. The motor of claim 1, further comprising means for providing locked rotor protection.

10. The motor of claim 9, wherein the means for providing locked rotor protection includes a Hall sensor configured to turn off the two high-side switches and two low-side switches of the H-bridge for a period of time when the Hall sensor detects a locked rotor condition.

11. The motor of claim 1, wherein the rotor is internal with respect to the stator.

12. The motor of claim 1, wherein the motor requires a number of pulses equal to the number of stator coils to cause the rotor to complete a full revolution.

13. A single coil, direct current permanent magnet brushless motor, comprising:

an internal rotor with six alternate polarity magnets rotatably journaled in the motor;

an external stator with six salient poles including six alternately wound coils coupled to form a single coil with two free ends;

a means for providing locked rotor protection; and

a commutated H-bridge including a voltage boost circuit having capacitors to provide a boosted voltage to alternately turn on high-side switches of the H-bridge, wherein the capacitors are charged by an unregulated bus voltage.

14. The motor of claim 13, wherein the H-bridge further includes an alternating current conversion circuit including a bridge rectifier and smoothing capacitor coupled to a source of alternating current, the conversion circuit converting the alternating current to provide direct current to power the motor.

15. The motor of claim 13, wherein the motor is configured to be powered by either alternating current or direct current.

16. The motor of claim 13, further comprising a microcontroller to commutate the H-bridge.

17. The motor of claim 13, wherein a uniform concentric air gap is defined between the stator and the rotor.

18. The motor of claim 13, wherein the means for providing locked rotor protection includes a Hall sensor configured to turn off the two high-side switches and two low-side switches of the H-bridge for a period of time when the Hall sensor detects a locked rotor condition.

19. The motor of claim 13, wherein the motor requires a number of pulses equal to the number of stator coils to cause the rotor to complete a full revolution.

20. A method of commutating a single coil, direct current permanent magnet brushless motor including a rotor with at least four magnets rotatably journaled in the motor and a stator with a like number of salient poles each having alternately wound coils coupled to form a single coil with two free ends, and a commutated H-bridge including a voltage boost circuit having capacitors providing a boosted voltage to alternately turn on high-side switches of the H-bridge, the method comprising:

charging the capacitors by a switching current flowing through low-side switches of the H-bridge;

controlling the high-side switches of the H-bridge using an inverted low-side switching signal from the low-side switches of the H-bridge; and

turning on the high-side switches of the H-bridge using the charge stored in the capacitors.

21. The method of claim 20, further comprising providing locked rotor protection.

22. The method of claim 20, further comprising providing an alternating current conversion circuit to allow the motor to be powered by alternating current.