Electricity: motive power systems – Switched reluctance motor commutation control
Reexamination Certificate
2001-10-09
2003-06-17
Nappi, Robert E. (Department: 2837)
Electricity: motive power systems
Switched reluctance motor commutation control
C318S132000, C318S434000, C318S599000, C318S459000, C318S500000, C388S923000, C388S928100
Reexamination Certificate
active
06580236
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a brushless motor drive circuit formed as a semiconductor integrated circuit.
More particularly, the present invention relates a brushless motor drive circuit in which induced voltages generated across exciting coils of respective phases are detected and, for each of the exciting coils of respective phases, a rotor position signal is produced which is a square wave signal and whose half period corresponds to a period from a polarity inversion of the induced voltage to the next polarity inversion of the induced voltage. Based on the rotor position signals, switching elements are square wave on-controlled and/or pulse width converted square wave PWM (Pulse Width Modulation) controlled, and thereby excitation of the exciting coils is controlled.
BACKGROUND OF THE INVENTION
FIG. 10
shows a circuit including a conventional semiconductor integrated circuit
100
for driving a brushless motor. As shown in
FIG. 10
, the semiconductor integrated circuit
100
is coupled with a star connection type three-phase brushless motor
1
, a microcomputer
2
for supplying a rotation speed control signal of the motor
1
, a DC power source V
DD
, and the ground. Exciting coils
3
,
4
and
5
of the motor
1
are star-connected and correspond to U phase, V phase and W phase, respectively. One terminals of the exciting coils
3
,
4
and
5
are coupled to a U phase terminal U, a V phase terminal V and a W phase terminal W, respectively, and the other terminals of the exciting coils
3
,
4
and
5
are commonly coupled, as the midpoint, to a midpoint terminal C. The microcomputer
2
is coupled to an input terminal S.
The semiconductor integrated circuit
100
comprises a bridge output circuit
6
which supplies excitation currents for respective phases to the exciting coils
3
,
4
and
5
in predetermined timing. The current value of each of the excitation currents is controlled by PWM control. The semiconductor integrated circuit
100
also comprises a detector circuit
7
which senses induced voltages generated across the exciting coils
3
,
4
and
5
, and produces square wave rotor position signals PU, PV and PW. A half period, that is, &pgr; radian, of each of the rotor position signals PU, PV and PW corresponds to a period from a zero-cross in which a polarity of an induced voltage inverts to the next zero-cross in which the polarity of the induced voltage inverts next time. The semiconductor integrated circuit
100
further comprises an inner voltage generating circuit
8
for generating an inner voltage as a voltage for pulse width modulation which varies according to a voltage of the rotation speed control signal supplied from the microcomputer
2
. The semiconductor integrated circuit
100
also comprises a triangular wave generating circuit
9
for generating a triangular wave voltage, and a comparator
10
for generating a PWM signal obtained by pulse width modulating the inner voltage from the inner voltage generating circuit
8
by using the triangle wave voltage from the triangle wave generating circuit
9
. The semiconductor integrated circuit
100
further comprises a control circuit
11
which performs excitation or current conduction timing control and PWM control for the bridge output circuit
6
, based on the PWM signal from the comparator
10
and the rotor position signal from the detector circuit
7
.
The bridge output circuit
6
comprises P-channel type MOS transistors Q
1
, Q
2
and Q
3
which control current conduction timing into the exciting coils
3
,
4
and
5
, respectively, and N-channel type MOS transistors Q
4
, Q
5
and Q
6
which perform PWM control of current values to the exciting coils
3
,
4
and
5
in predetermined timing. The control circuit
11
supplies current conduction timing control signals to the gate electrodes of the MOS transistors Q
1
, Q
2
and Q
3
, and supplies current quantity control signals to the MOS transistors Q
4
, Q
5
and Q
6
. The main current paths of the MOS transistors Q
1
and Q
4
, the MOS transistors Q
2
and Q
5
, and the MOS transistors Q
3
and Q
6
are respectively coupled in series. The source electrodes of the MOS transistors Q
1
, Q
2
and Q
3
are commonly coupled to the power source V
DD
and the source electrodes of the MOS transistors Q
4
, Q
5
and Q
6
are commonly coupled to the ground. The common connection node between the MOS transistors Q
1
and Q
4
, the common connection node between the MOS transistors Q
2
and Q
5
and the common connection node between the MOS transistors Q
3
and Q
6
are coupled with the terminals U, V and W of the motor
1
, respectively.
The detector circuit
7
detects or senses the induced voltages generated across the exciting coils
3
,
4
and
5
via the terminals U, V, W and C. By using integrating circuits and comparators which are provided within the detector circuit
7
and which are not shown in the drawing, the detector circuit
7
produces the square wave rotor position signals PU, PV and PW. A half period, that is, &pgr; radian, of each of the rotor position signals PU, PV and PW corresponds to a period from a zero-cross in which a polarity of an induced voltage inverts to the next zero-cross in which the polarity of the induced voltage inverts again next time.
The control circuit
11
receives the PWM signal from the comparator
10
and the rotor position signals PU, PV and PW from the detector circuit
7
. Thereby, the control circuit
11
determines current conduction timing to the respective exciting coils
3
,
4
and
5
. The control circuit
11
produces the current conduction timing control signals supplied to the gate electrodes of the MOS transistors Q
1
, Q
2
and Q
3
and the current quantity control signals supplied to the gate electrodes of the MOS transistors Q
4
, Q
5
and Q
6
. At a start time of the motor, the induced voltages are not generated across the exciting coils
3
,
4
and
5
, so that the detector circuit
7
does not produce the rotor position signals PU, PV and PW. Therefore, at a start time of the motor, predetermined start pattern signals are supplied to the control circuit
11
from a start circuit not shown in the drawing.
With reference to FIG.
10
and
FIGS. 11A-11D
, an explanation will be made on an operation of the semiconductor integrated circuit
100
which has the above-mentioned structure, when the semiconductor integrated circuit
100
is coupled with the motor
1
as shown in
FIG. 10. A
detailed explanation on the control of current conduction timing and current quantities of the respective exciting coils
3
,
4
and
5
will be provided later. The control circuit
11
sets the current conduction timing as shown in FIG.
11
A. As shown in
FIG. 11D
, the control circuit
11
supplies the current conduction timing control signals of square waves to the gate electrodes of the MOS transistors Q
1
, Q
2
and Q
3
, and supplies the current quantity control signals to the gate electrodes of the MOS transistors Q
4
, Q
5
and Q
6
at respective timing. Each of the current quantity control signals is a pulse width converted square wave PWM signal and has a constant on-duty cycle during each control timing. The on-duty cycle of the pulse width converted square wave PWM signal varies depending on the required current quantity. In order shown in
FIG. 11B
, the MOS transistors Q
1
, Q
2
and Q
3
are on-controlled by square wave signals (SQ-ON CONTROL), and also the MOS transistors Q
4
, Q
5
and Q
6
are pulse width converted square wave PWM controlled (PWSQ-PWM CONTROL). In the motor
1
, among the exciting coils
3
,
4
and
5
of three phases, a current flows from the exciting coil of the phase coupled to a high side voltage, i.e., V
DD
, to the exciting coil of the phase coupled to a low side voltage, i.e., the ground, in order shown in FIG.
11
A. That is, the exciting coils of two phases are sequentially energized in order of phase shown in FIG.
11
A and thereby the rotor of the motor
1
rotates. The direction of the current varies such that
Duda Rina I.
Nappi Robert E.
NEC Electronics Corporation
Whitham Curtis & Christofferson, PC
LandOfFree
Brushless motor drive circuit having low noise and high... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Brushless motor drive circuit having low noise and high..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Brushless motor drive circuit having low noise and high... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3119435