Method for commutating an electronically commutated motor and motor for carrying out said method

• US 20050083002A1
• Filed: 01/28/2003
• Published: 04/21/2005
• Est. Priority Date: 02/06/2002
• Status: Active Grant

• Current Assignee: Ebm-Papst St Georgen GmbH & Company KG (Ebm-Papst Mulfingen GmbH & Company KG)
• Original Assignee: Ebm-Papst St Georgen GmbH & Company KG (Ebm-Papst Mulfingen GmbH & Company KG)
• Inventors: Berroth, Hansjorg
• Granted Patent: US 7,015,668 B2
• Time in Patent Office: Days
• US Class Current: 318/400.290
• CPC Class Codes: H02P 6/15 Controlling commutation time

Abstract

An improved method of commutating an electronically commutated motor (20) is disclosed. The motor has a positive (34) and a negative connecting lead (36), a stator having at least one winding phase (22), a permanent-magnet rotor (26), a rotor-position sensor (28) for producing a rotor position signal (u1, u2), and a full bridge circuit (78), comprising a pair of Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) coupled to each end of each winding phase (22). In order to prevent current shoot-through and prolong the service life of the MOSFETs, without employing a microprocessor, a respective-comparator (90, 90′, 92, 92′) is coupled to the gate of each MOSFET, in order to assure that the MOSFET is switched ON and OFF at an optimum time.

Claims

1. A method of commutating an electronically commutated motor (20), which motor comprises

a positive connecting lead (34) and a negative connecting lead (36);

a stator having at least one winding phase (22);

a permanent-magnet rotor (26);

a rotor position sensor (28) for producing at least one rotor position signal (u1, u2) dependent on the position of that rotor (26);

a full bridge circuit (78), associated with the at least one winding phase (22) and controllable by means of the rotor position sensor (28), said full bridge circuit having upper transistors (70, 72), implemented as MOSFETs, that control the connection of the at least one winding phase (22) to the positive connecting lead (34), and lower transistors (74, 76), implemented as MOSFETs complementary to the upper transistors (70, 72), that control the connection of the at least one winding phase (22) to the negative connecting lead (36),

two complementary MOSFET transistors (e.g. 70, 74) being connected in series in each bridge arm, and a comparator (90, 90′

, 92, 92′

) being associated with each MOSFET transistor of the full bridge circuit (78) in order to control that transistor,

comprising the steps of;

in the context of a predetermined change in the rotor position signal (u1, u2), switching OFF the MOSFET transistor of a bridge arm to be switched off, in a manner controlled by that signal change, by means of the comparator associated with that transistor;

while the MOSFET transistor to be switched off is being switched off, monitoring the gate potential of the MOSFET transistor to be switched off by means of a comparator associated with the MOSFET transistor of a bridge arm that is to be switched on; and

once that gate potential has reached a value that is characteristic of a switching off of the MOSFET transistor to be switched off, switching ON the MOSFET transistor to be switched on by means of the comparator associated with it.

2. An electronically commutated motor (20) that comprises

a positive connecting lead (34) adapted to carry an operating voltage (U_B) and a negative connecting lead (36);

a stator having at least one winding phase (22);

a permanent-magnet rotor (26);

a rotor position sensor (28) for producing at least one rotor position signal (u1, u2) dependent on the position of that rotor (26);

a full bridge circuit (78), associated with the at least one winding phase (22) and controllable by means of the rotor position sensor (28), said full bridge circuit having upper transistors (70, 72), implemented as p-channel MOSFETs, that control the connection of the at least one winding phase (22) to the positive connecting lead (34), and lower transistors (74, 76), implemented as n-channel MOSFETs, that control the connection of the at least one winding phase (22) to the negative connecting lead (36),

one p-channel MOSFET and one n-channel MOSFET being connected in series in each bridge arm,

and each MOSFET of the full bridge circuit (78) having associated with it, in order to control said MOSFET, a respective comparator (90, 90′

, 92, 92′

), of which one comparator, upon a commutation, in a manner controlled by the rotor position signal (u1, u2), makes the transistors presently to be switched off, of the relevant bridge arm, nonconductive,

and the other comparator compares a signal dependent on the source-gate voltage, of the bridge transistor to be switched off, with a reference voltage, in order to switch on the bridge transistor controlled by that other comparator only when the magnitude of that source-gate voltage falls below a predetermined value.

3. The motor according to claim 2,

wherein the rotor position signal (u1, u2) is fed to the two comparators (90, 92) of a bridge arm via a respective diode (108, 130), the diode (108) of the one comparator (90) being polarized oppositely to the diode (130) of the other comparator (92).

4. The motor according to claim 3,

wherein the diodes (108, 130) are polarized in such a way that the respective diodes of the comparator that is associated with the bridge transistor to be switched on, blocks, in order to enable, by means of that comparator, a comparison of the gate potential, of the bridge transistor to be switched off, with a predetermined reference voltage.

5. The motor according to claim 2,

wherein at least one of the reference voltages, associated with said bridge transistors, is a function of the operating voltage (U_B) of the motor (20).

6. The motor according to claim 2,

wherein the amplitude (U_B/2) of the rotor position signal (u1, u2) is a function of the operating voltage (U_B) of the motor (20).

7. The motor according to claim 2,

wherein a capacitance (96, 96′

, 98, 98′

) is provided to delay a signal change at the gate of at least one transistor (70, 72, 74, 76) of the full bridge (78).

8. The motor according to claim 7,

wherein an internal parasitic capacitance, of a transistor of the full bridge, serves as the capacitance for delaying the signal change at the gate of that transistor.

9. The motor according to claim 2,

wherein the comparators (90, 92) of a bridge arm are connected to one another (110, 132) to form a bistable element, in order to achieve a stable switching state after a commutation, as long as the rotor position signal (u1, u2) changes less than a predetermined amount.

10. The motor according to claim 3,

wherein the comparators (90, 92) of a bridge arm are connected to one another (110, 132) to form a bistable element, in order to achieve a stable switching state after a commutation, as long as the rotor position signal (u1, u2) changes less than a predetermined amount.

11. The motor according to claim 4,

wherein the comparators (90, 92) of a bridge arm are connected to one another (110, 132) to form a bistable element, in order to achieve a stable switching state after a commutation, as long as the rotor position signal (u1, u2) changes less than a predetermined amount.

12. The motor according to claim 5,

wherein the comparators (90, 92) of a bridge arm are connected to one another (110, 132) to form a bistable element, in order to achieve a stable switching state after a commutation, as long as the rotor position signal (u1, u2) changes less than a predetermined amount.

13. The motor according to claim 6,

wherein the comparators (90, 92) of a bridge arm are connected to one another (110, 132) to form a bistable element, in order to achieve a stable switching state after a commutation, as long as the rotor position signal (u1, u2) changes less than a predetermined amount.

14. The motor according to claim 7,

wherein the comparators (90, 92) of a bridge arm are connected to one another (110, 132) to form a bistable element, in order to achieve a stable switching state after a commutation, as long as the rotor position signal (u1, u2) changes less than a predetermined amount.

15. The motor according to claim 3,

wherein at least one of the reference voltages, associated with said bridge transistors, is a function of the operating voltage (U_B) of the motor (20).

16. The motor according to claim 4,

wherein at least one of the reference voltages, associated with said bridge transistors, is a function of the operating voltage (U_B) of the motor (20).

17. The motor according to claim 3,

wherein the amplitude (U_B/2) of the rotor position signal (u1, u2) is a function of the operating voltage (U_B) of the motor (20).

18. The motor according to claim 4,

wherein the amplitude (U_B/2) of the rotor position signal (u1, u2) is a function of the operating voltage (U_B) of the motor (20).

19. The motor according to claim 5,

wherein the amplitude (U_B/2) of the rotor position signal (u1, u2) is a function of the operating voltage (U_B) of the motor (20).

20. The motor according to claim 3,

wherein a capacitance (96, 96′

, 98, 98′

) is provided to delay a signal change at the gate of at least one transistor (70, 72, 74, 76) of the full bridge (78).

21. The motor according to claim 4,

wherein a capacitance (96, 96′

, 98, 98′

) is provided to delay a signal change at the gate of at least one transistor (70, 72, 74, 76) of the full bridge (78).

22. The motor according to claim 5,

wherein a capacitance (96, 96′

, 98, 98′

) is provided to delay a signal change at the gate of at least one transistor (70, 72, 74, 76) of the full bridge (78).

23. The motor according to claim 6,

wherein a capacitance (96, 96′

, 98, 98′

) is provided to delay a signal change at the gate of at least one transistor (70, 72, 74, 76) of the full bridge (78).