Control of a fan motor for an improved EMC behavior

Abstract

A method is provided for electrically driving a motor having a plurality of phase windings such that EMC (electromagnetic compatibility) is improved and the running performance of the motor is simultaneously kept constant. At least one of the phase windings is not supplied with a current pulse during a complete revolution of the rotor, or at least one switchable electrical resistor is switched on, for at least one subsequent commutation phase by means of an electrical switching element, if the detected rotor speed is greater than the specified target speed.

Claims

1. A method for electrically driving a motor having a bridge circuit electrically coupling a plurality of phase windings, wherein the motor has a sensor for detecting a rotor speed and/or a rotor position of a rotor of the motor, the method comprising: applying, by a microprocessor, current pulses alternately to individual phase windings of the plurality of phase windings by drive electronics of the motor electrically coupled to the microprocessor, the drive electronics include the bridge circuit; performing, by the microprocessor, a rough adjustment of the rotor speed when a difference between the determined rotor speed (T.sub.actual) and a specified target speed (T.sub.target) exceeds a specified threshold, the rough adjustment of the rotor speed is performed during a complete revolution of the rotor by not supplying a current pulse to no more than half of the phase windings of the plurality of phase windings; and performing, by the microprocessor, a fine adjustment of the rotor speed after the rough adjustment when the determined rotor speed (T.sub.actual) is larger than the specified target speed (T.sub.target) and when the difference between the determined rotor speed (T.sub.actual) and the specified target speed (T.sub.target) is smaller than the specified threshold by switching on at least one switchable electrical resistor of the drive electronics for at least one subsequent commutation phase by at least one electronic switching element of the drive electronics.

2. The method according to claim 1, wherein: a state of the at least one electronic switching element is left unchanged during a commutation phase.

3. The method according to claim 1, wherein: an electrical current of the current pulse through the phase winding is reduced by the at least one switchable electrical resistor during the at least one subsequent commutation phase for reducing the rotor speed.

4. The method according to claim 1, wherein: the drive electronics comprises a plurality of switchable electrical resistors connected in series; and the plurality of switchable electrical resistors are individually switched on and/or short-circuited by the at least one electronic switching element as a function of the difference between the determined rotor speed and the specified target speed, thereby regulating the rotor speed.

5. The method according to claim 4, wherein: the drive electronics further comprises a plurality of electronic switching elements operable to individually switch on and/or short circuit the plurality of switchable electrical resistors.

6. The method of claim 1, further comprising the steps of: applying a maximum current of the current pulses to at least one of the phase windings during at least one commutation phase when the motor is started.

7. The method of claim 6, wherein the drive electronics further comprises: at least one switchable electrical resistor configured to reduce an electrical current of the current pulses to the maximum current that is applied to at least one of the phase windings during at least one commutation phase when the motor is started, the at least one switchable electrical resistor positioned in series the bridge circuit and electrically coupled to the bridge circuit and the microprocessor.

8. The method of claim 6, wherein the at least one switchable electrical resistor is positioned in series between the bridge circuit and the microprocessor and is electrically coupled to the bridge circuit and the microprocessor.

9. A system, comprising: a motor; a drive electronics circuit electrically coupled to the motor, the drive electronics circuit having: a bridge circuit; a plurality of phase windings electrically coupled to the bridge circuit; a sensor for detecting a rotor speed and/or a rotor position of a rotor of the motor electrically coupled to the bridge circuit; and a microprocessor electrically coupled to the drive electronics circuit and operable to: apply current pulses alternately to the plurality of phase windings thereby driving the motor; perform a rough adjustment of the rotor speed when a difference between a determined rotor speed (T.sub.actual) and a specified target speed (T.sub.target) exceeds a specified rotor speed threshold, the rough adjustment of the rotor speed performed during a complete revolution of the rotor by not supplying a current pulse to no more than half of the phase windings of the plurality of phase windings; and perform a fine adjustment of the rotor speed after the rough adjustment when the determined rotor speed (T.sub.actual) is larger than the specified target speed (T.sub.target) and when the difference between the determined rotor speed (T.sub.actual) and the specified target speed (T.sub.target) is smaller than the specified threshold by switching on at least one switchable electrical resistor of the drive electronics for at least one subsequent commutation phase by at least one electronic switching element of the drive electronics.

10. A fan comprising the motor according to claim 9.

11. The system of claim 9, wherein: the drive electronics circuit further includes a plurality of electrical resistors connected in series, which are individually switched on and short-circuited by at least one electronic switching element of the drive electronics circuit or a plurality of electronic switching elements as a function of the difference between the determined rotor speed (T.sub.actual) and the specified target speed (T.sub.target).

12. The system of claim 9, wherein the microprocessor is further operable to apply a maximum current of the current pulses to at least one of the phase windings during at least one commutation phase when the motor is started.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1: shows a circuit diagram for driving electronics of a motor,

(3) FIG. 2: shows the timing based on a diagram for a method for driving a motor with slot shutdown,

(4) FIG. 3: shows a further timing based on a diagram for a method for driving motor by means of reducing a current using switched on series resistors,

(5) FIG. 4: shows a schematic diagram for a plurality of phase windings, and

(6) FIG. 5: shows a flowchart for an embodiment of the method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(7) FIG. 1 shows a circuit diagram of driving electronics 10 or a section of the driving electronics 10 for a motor 100. The driving electronics 10 has two substantial circuit portions. A first circuit portion consists of a bridge circuit or an H-bridge, which is integrated into an integrated circuit (IC) 15. A second circuit portion consists of a series circuit of switchable electrical resistors 12, which are switched by means of electronic switching elements 13. The resistor network of the switchable electrical resistors 12 connected in series is connected in series to the H-bridge. A microprocessor 32, which includes a comparator 33, is electrically coupled to the driving electronics 10. In some embodiments, the microprocessor 32 is electrically coupled to the electronic switching element 13 of the driving electronics 10 and is configured to apply various amounts of current pulses alternately to individual phase windings of the plurality of phase windings.

(8) The H-bridge or the IC 15 is always controlled with full load or with a maximum specified current for driving the motor 100 according to the invention. For fine adjustment, electrical resistors 12 can be switched on by means of the electronic switching elements 13 during individual commutation phases, in order to reduce the effective current of the current pulse 30 through a phase winding 14 of the stator of the motor 100 and thus reduce the rotor speed (T.sub.actual), if it exceeds the specified target speed (T.sub.target).

(9) A slot interruption can be envisaged for rough adjustment. In this case, the current pulses 30 through phase windings 14 are omitted during individual commutation phases. If the detected rotor speed (T.sub.actual) exceeds the specified target speed (T.sub.target), the current pulse 30 can be applied through a phase winding 14 by means of rough adjustment, for example in a subsequent commutation phase.

(10) FIG. 2 shows a diagram showing the output signal 31 of the Hall effect sensor and the current path I of the individual current pulses 30 through the phase windings 14. The diagram in FIG. 2 is in this case based on the example of a rough adjustment. For example, the current pulse 30 has been interrupted during the commutation phase t4 in the example shown in FIG. 2. By means of the method for driving the motor 100 it has been determined during the commutation phase t3 that the rotor speed (T.sub.actual) is greater than the specified target speed (T.sub.target), and has thus been decided to omit or interrupt the current pulse 30 in the subsequent slot t4 or in the subsequent commutation phase. As a result of constantly checking the rotor speed (T.sub.actual), it has in turn been determined during the commutation phase t4 that the rotor speed (T.sub.actual) has got closer to the specified target speed (T.sub.target) and the current pulse 30 has therefore been reinstated during the commutation phase t5.

(11) With regard to the rough adjustment, it should be noted that the method envisages interrupting or omitting the current pulse 30 during a complete revolution of the rotor for as few commutations phases as possible, particularly preferably only during one commutation phase.

(12) FIG. 3 shows a corresponding diagram showing the outcome resulting from a fine adjustment based on switching on electrical resistors 12. In the example shown in FIG. 3, the effective current through the phase windings has been reduced during the commutation phases t4 and t5 by electronic resistors 12 being switched on by means of the electronic switching elements 13. This reduces the rotor speed (T.sub.actual) by means of fine adjustment. In the example shown in FIG. 3, the electrical resistors 12 have not been closed or short-circuited by means of the electronic switching elements 13 during the commutation phases t1 to t3.

(13) FIG. 4 is a schematic diagram showing three or more phase windings 400, 402 and 410. Each of the phase windings 400, 402 and 410 might be identical to the phase winding 14 shown in FIG. 1. Current pulses are alternately applied to the individual phase windings by drive electronics of the motor.

(14) FIG. 5 is a flowchart showing the steps of the method according to an embodiment of the present invention. In step 110, the rotor speed is being constantly checked. In step 112, it is determined if the rotor speed is greater than the specified target speed. If the answer is Yes, then step 114 is executed where no more than half of the phase windings are not supplied a current pulse during a complete revolution of the rotor. The rotor speed continues to be checked for the subsequent commutation phase. If the answer is No, then the rotor speed continues to be checked.

REFERENCE LIST

(15) 100 motor 200 fan 10 driving electronics 11 means for detecting the rotor speed 12 electrical resistor 13 electronic switching element 14 phase winding 15 integrated circuit 30 current pulse 31 output signal of the Hall effect sensor 32 microprocessor