Electricity: motive power systems – Switched reluctance motor commutation control
Reexamination Certificate
2000-04-07
2002-01-01
Ro, Bentsu (Department: 2832)
Electricity: motive power systems
Switched reluctance motor commutation control
C318S434000, C318S721000
Reexamination Certificate
active
06335598
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a brushless motor system, and more particularly, to a brushless motor system with capacitors.
2. Description of the Prior Art
DC brushless motors are widely used due to their simplicity of design, durability and efficiency. Many of the motors used in computer storage devices, such as the spindle motors of hard disk, CD-ROM, CD-RW and DVD devices, all employ DC brushless motor technology. As computing speeds grow, so, too, does the demand for faster access times of computer storage devices. This places greater demands of speed and stability on the spindle motors of these devices. Therefore, controlling a spindle motor to make it both fast and stable has become an important subject in the field of storage device design.
Please refer to FIG.
1
.
FIG. 1
is a schematic diagram of a prior art brushless motor system
10
. The prior art brushless motor system
10
comprises a 3-phase brushless motor
12
, a driver
14
, and three Hall sensors
16
. The brushless motor
12
comprises a rotor (not shown). The Hall sensors
16
are used to detect the rotor position. The driver
14
drives the rotor of the brushless motor
12
based upon the rotor position as detected by the Hall sensors
16
.
As the rotor rotates, each of the Hall sensors
16
generates and sends two corresponding sensing signals to the driver
14
. The sensing signals generated by the three Hall sensors
16
are denoted as H
1
+, H
1
−, H
2
+, H
2
−, H
3
+, and H
3
−. The driver
14
outputs 3 phase currents A
1
, A
2
, and A
3
to drive the brushless motor
12
based upon the sensing signals generated by the three Hall sensors
16
.
Please refer to FIG.
2
.
FIG. 2
is an ideal time sequence diagram of the sensing signals H
1
+, H
1
−, H
2
+, H
2
−, H
3
+, H
3
− and the 3 phase currents A
1
, A
2
, and A
3
. As the rotor rotates, the sensing signals H
1
+, H
1
−, H
2
+, H
2
−, H
3
+, and H
3
−, which have the same wave shape but with different phases, are generated by the Hall sensors
16
. The corresponding 3 phase currents A
1
, A
2
, and A
3
, which also have the same wave shape but with different phases, are generated by the driver
14
according to these sensing signals. Ideally, the two sensing signals generated by the same Hall sensor
16
should have the same DC bias and should be symmetrical with respect to each other. Under these ideal conditions, the driver
14
should generate the correct 3 phase currents A
1
, A
2
, and A
3
, with no DC biases, based upon these ideal sensing signals, resulting in the smooth operation of the brushless motor
12
.
Please refer to FIG.
3
.
FIG. 3
is a realistic time sequence diagram of the sensing signals H
1
+, H
1
− and the phase current A
1
. Generally, the wave shape of the sensing signals does not match the ideal wave shape shown in FIG.
2
. Due to inaccuracies of the ion-implantation process that is used to make the Hall sensors
16
, or environmental effects such as temperature, the DC biases in the two sensing signals generated by the same Hall sensor
16
are not usually the same. For instance, the DC bias Dc+ in the sensing signal H
1
+ will probably be different from the DC bias Dc− in the sensing signal H
1
−. This differing bias will cause the motor driver
14
to generate the output phase current A
1
with a DC bias. Likewise, the sensing signals H
2
+, H
2
+, and H
3
+, H
3
− with different DC biases will also cause the motor driver
14
to generate the output phase currents A
2
and A
3
with DC biases. As the output phase currents correspond to the torque of the motor, biased currents will generate an unbalance torque. As a result, the brushless motor
12
will not run smoothly.
SUMMARY OF THE INVENTION
It is therefore a primary objective of the present invention to provide a brushless motor system with capacitor devices to solve the above mentioned problem.
In a preferred embodiment, the present invention provides a brushless motor system comprising:
a brushless motor comprising a rotor;
at least one sensing circuit for detecting the rotor position, the sensing circuit comprising:
a Hall sensor comprising two output ports; wherein as the rotor rotates, the Hall sensor will generate a sensing signal at each of the two output ports; and
a capacitor device for each of the two output ports of the Hall sensor, the capacitor device connected in series with the output port; wherein the two capacitor devices are used to filter out DC biases in the two sensing signals; and
a motor driver connected to the two capacitor devices for driving the rotor of the brushless motor according to the two sensing signals from the two capacitor devices.
It is an advantage of the present invention that the brushless motor system comprises the capacitor devices, which filter out the DC biases in the sensing signals, so that the brushless motor will run fast and smooth.
This and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.
REFERENCES:
patent: 4030005 (1977-06-01), Doemen
patent: 4230976 (1980-10-01), Muller
patent: 4473782 (1984-09-01), Reinhardt et al.
patent: 4724365 (1988-02-01), Muller
Lin Chi-Cheng
Lin Ching-Hung
Tung Shun-Yi
Acer Communication and Multimedia Inc.
Hsu Winston
Ro Bentsu
LandOfFree
DC brushless motor system with capacitors does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with DC brushless motor system with capacitors, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and DC brushless motor system with capacitors will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2834580