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參數(shù)資料
| 型號： | ML4428 |
| 廠商： | Fairchild Semiconductor Corporation |
| 英文描述： | Sensorless Smart-Start BLDC PWM Motor Controller(無傳感智能啟動無刷直流PWM電機控制器) |
| 中文描述： | 智能傳感器啟動無刷電機控制器的PWM（無傳感智能啟動無刷直流脈寬調(diào)制電機控制器） |
| 文件頁數(shù)： | 11/16頁 |
| 文件大小： | 151K |
| 代理商： | ML4428 |
ML4428
REV. 1.0 11/17/2000
11
START-UP SEQUENCING
When the motor is initially at rest, it is generating no
back-EMF. Because a back-EMF signal is required for
closed loop commutation, the motor must be started by
other means until a velocity sufficient to generate some
back-EMF is attained.
Start
For RC
VCO
voltages of less than 0.6V the ML4428 will
send 6 sample pulses to the motor to determine the rotor
position and drive the proper windings to produce desired
rotation. This will result in motor acceleration until the
RC
VCO
pin achieves 0.6V and closed loop operation
begins. This technique results in zero reverse rotation and
minimizes start-up time. The sample time pulses are set
by C
SNS
and the initial sample interval is set by R
INIT
.
This sense technique is not effective for air core motors,
since a minimum of 30% inductance difference must
occur when the motor moves.
Direction
The direction of motor rotation is controlled by the
commutation states as given in Table 1. The state
sequence is controlled by the F/
R
.
Run
When the RC
VCO
pin exceeds 0.6V the device will enter
run mode. At this time the motor speed should be about
8% FRPM
MAX
and be high enough to generate a
detectable BEMF and allow closed loop operation to
begin. The commutation position compensation has been
previously discussed.
The motor will continue to accelerate as long as the
voltage on the RC
VCO
is less than the voltage on V
SPEED
.
During this time the motor will receive full N-channel
drive limited only by I
LIMIT
. As the voltage on RC
VCO
approaches that of V
SPEED
the C
ISC
capacitor will charge
and begin to control the gate drive to the N-channel
transistor by setting a level for comparison on the 25kHz
PWM saw tooth waveform generated on C
PWM
. The
compensation of the speed loop is accomplished on C
SC
and on C
ISC
which are outputs of transconductance
amplifiers with a gm = 2.3
∞
10
–4
.
Figure 8. Speed Control Block Diagram.
+
–
+
–
MODE
SELECT
I
SNS
RC
VCO
V
SPEED
C
SC
5
C
ISC
21
8
20
1
C
PWM
6
+
–
0.23mmho
0.23mmho
LEVEL
SHIFT
+1.4V
LINEAR CONTROL
TO LOW-SIDE
GATE DRIVE
PWM CONTROL
TO COMMUTATION
LOGIC
Figure 7. ILIMIT Output Off-Time vs. COS.
Note:
100pF gives 10μs, 200pF gives 20μs, etc.
0
100
200
300
400
500
60
50
40
30
20
10
0
T
O
C
IOS
(pF)
Slope
dT
C
dV
i
V
μ
A
k
=
=
=
=
5
50
100
Speed Control
The speed control section of the ML4428 is detailed in
Figure 8. The two transconductance amplifiers with
outputs at C
SC
and C
ISC
each have a gm of 0.23mmhos.
The bandwidth of the current feedback component of the
speed control is set at C
ISC
as follows:
f
C
C
dB
3
ISC
ISC
4
5
2.
2
π
3 66 10
.
=
=
For f
3dB
= 50kHz, C
ISC
would be 730pF. The filter
components on the C
SC
pin set the dominant pole in the
system and should have a bandwidth of about 10% of the
position filter on the RC
VCO
pin. Typically this is in the 1
to 10Hz range.
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| ML4428CP | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Sensorless Smart-Start⑩ BLDC PWM Motor Controller |
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| ML4428IP | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Sensorless Smart-Start⑩ BLDC PWM Motor Controller |
| ML4428IS | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Sensorless Smart-Start⑩ BLDC PWM Motor Controller |
| ML4428直流電機控制芯片 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述: |
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