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參數(shù)資料
| 型號(hào)： | ML4426 |
| 廠商： | Fairchild Semiconductor Corporation |
| 英文描述： | Bi-directional Sensorless BLDC Motor Controller(雙向無傳感無刷直流電機(jī)控制器) |
| 中文描述： | 雙向傳感器無刷直流電機(jī)控制器（雙向無傳感無刷直流電機(jī)控制器） |
| 文件頁(yè)數(shù)： | 10/16頁(yè) |
| 文件大?。?/td> | 1089K |
| 代理商： | ML4426 |
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ML4426
FB A
22
F/
R
12
FB B
23
FB C
24
BACK
EMF
SAMPLER
VDD
500nA
SPEED
FB
C
SPEEDFB1
C
SPEEDFB2
R
SPEEDFB
20
VOLTAGE
CONTROLLED
OSCILLATOR
PHASE
LOCKED
LOOP
VCO/TACH
13
A
B
C
D
E
F
R
COMMUTATION
STATE MACHINE
BACK EMF SENSING PLL COMMUTATION CONTROL
Three blocks form a phase locked loop that locks the
commutation clock onto the back EMF signal: the
commutation state machine, the voltage controlled
oscillator, and the back EMF sampler. The complete phase
locked loop is illustrated in Figure 7. The phased locked
loop requires a lead lag filter that is set by external
components on SPEED FB. The components are selected
as follows:
C
K
M
N
d
f
SPEEDFB
O
S
2
VCO
1
1
2
2
025
.
100
=
ln
(6a)
R
M
d
f
N
5
K
M
SPEEDFB
VCO
S
O
=
-
2
100
0
1
1
ln
0
5
(6b)
C
C
M
SPEEDFB
SPEEDFB
2
1
1
=
-
(6c)
START-UP SEQUENCE
When power is first applied to the ML4426 and the motor
is at rest, the back EMF is equal to zero. The motor needs
to be rotating for the back EMF sampler to lock onto the
rotor position and commutate the motor. The ML4426 uses
an open loop start-up technique to bring the rotor from rest
up to a speed fast enough to allow back EMF sensing.
Start-up is comprised of three modes: align mode, ramp
mode, and run mode.
Align Mode (RESET)
Before the motor can be started, the rotor must be in a
known position. When power is first applied to the
ML4426, the controller is reset into the align mode. Align
mode turns on the output drivers LB,
HA
, and
HC
which
aligns the motor into a position 30 electrical degrees
before the center of the first commutation state. This is
shown as state R in the commutation states of Table 1.
Align mode must last long enough to allow the motor and
its load to settle into this position. The align mode time is
set by a capacitor connected to the C
AT
pin as shown in
Figure 8. C
AT
is charged by a constant 750μA current from
GND to 1.5 V until the align comparator trips to end the
align mode. A starting point for C
AT
is calculated as
follows:
C
t
amp
V
AT
S
=
-
75 10
.
15
.
7
(7)
If the align time is not long enough to allow the rotor to
settle for reliable starting, then increase C
AT
until the
desired performance is achieved.
FUNCTIONAL DESCRIPTION
(Continued)
Ramp Mode
At the end of align mode the controller goes into ramp
mode. Ramp mode starts commutating through the states
A through F as shown in Table 1. This ramps up the
commutation frequency, and therefore the motor speed,
for a fixed length of time. This allows the motor to reach a
sufficient speed for the back EMF sampler to lock
commutation onto the motor's back EMF. The amount of
time the ML4426 stays in ramp mode is determined by a
capacitor connected to the C
RT
pin as shown in Figure 8.
C
RT
is charged by a constant 750μA current from GND to
1.5 V until the ramp comparator trips to end the ramp
mode. This gives a fixed ramp time. C
RT
is calculated as
follows:
C
J
amp K
N
3
I
K
RT
V
MAX
t
=
-
2
7
p
(8)
The rate at which the ML4426 ramps up the motor speed
is determined by a fixed 500μA current source on the
SPEED FB pin. The current sources charges up the PLL
filter components causing the VCO frequency to ramp up.
During ramp mode, the back EMF sampler is disabled to
allow control of the ramping to be set only by the 500μA
current source. The ramp based on the SPEED FB filter is
generally too fast for the motor to keep up, so a capacitor
from C
RR
to SPEED FB can be added to slow down the
ramping rate. The optimal ramp rate is based on the motor
and load parameters and is can be adjusted by varying
the value of C
RR
.
Figure 7. Back EMF Commutation Phase Locked Loop
REV. 1.0 10/10/2000
10
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ML4426 WAF | 制造商:Fairchild Semiconductor Corporation 功能描述: |
| ML4426CH | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Bi-directional Sensorless BLDC Motor Controller |
| ML4426CP | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Bi-directional Sensorless BLDC Motor Controller |
| ML4426CS | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| ML4426IH | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Bi-directional Sensorless BLDC Motor Controller |
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