AN1088 Datasheet, PDF (8/14 Pages) STMicroelectronics – L6234 THREE PHASE MOTOR DRIVER

AN1088 APPLICATION NOTE
Figure 15. Oscillator for Reference Speed.
Reference Speed
+5V
3 8 ⁴ 7 ^R27
NE555
16K
6
1
52
C20
100nF
R26
C21
36K 100nF
C19
100nF
Figure 16. Phase Locked Loop and filtering.
+5V
C12
100nF
LM358
8
R14
3
47K
Vcontrol
1
+
-
4
2
R13
BAT47
+5V
47K
+5V
R15
P2
1K
47K
R12
P1
47K
5K
+5V
GND
C13
1uF
HALL1 (Speed feedback)
Reference Speed
C14
100nF
+5V
R17
10M
C15
C16
R18 ^{100nF 220nF}
33K
R16
270K
R19
C17 ^91K
R21
47nF
91K
R20
8
9
11
Aux.
OP-AMP
2.5V
Loop
+VIN
Amplifier
13
3635
12 10
14 ^{Phase/ Frequency}
Detector
6
2 3 ^{15 1}
Output
4
5
7
16
GND
TP8
Figure 17. Control Logic Circuit.
MOTOR
HALL
EFFECT
SIGNALS
+5V
R22 R23
10k 10k
+5V
R29
10k
SW2
R24
10k
17
HALL1
2
EN1
19
18 ^EN2
HALL2
3
17 ^EN3
HALL3 ₄ GAL 16V8 ₁₆ IN1
DIR
5
15 ^IN2
BRAKE
IN3
6
PWM
20
1014
EN1
EN2
EN3
IN1
IN2
IN3
PWM
+5V
C18
R25
R26
100nF
DIRECTION CHANGE
10k
10k
DIR =0 GND : BACK ROTATION
DIR = 5V : FORWARD ROTATION
BRAKE
SW1
DIR
GND
J1
BRAKE FUNCTION
BRAKE = GND : BRAKE
BRAKE = 5V : GO
When the hall effect signal fre-
quency is lower than the reference
frequency, the control voltage is
maintained to a value that sets the
motor current limit and therefore the
torque control limit. The peak cur-
rent limit is given by Ipeak = Vcon-
trol/Rsense.
When the frequency from the Hall
Effect sensors exceeds the refer-
ence frequency and an error signal
is generated by the PLL (see Fig.
14). An LM358 comparator, a loop
amplifier and an auxiliary OP-AMP
ensure the right gain and filtering to
guarantee the stability (see fig.16).
The error signal causes Vcontrol
decrease to a value that sets the
PWM chopping current control in or-
der to reduce the torque and set
the desired speed. The motor
speed is regulated to within ± 0.02
% of the desired speed.
Control Logic Circuit.
The logic sequence to the motor is
generated by a GAL16V8, which
decodes the Hall Effect signals and
generates the INPUT and ENABLE
pattern shown in Fig. 18.
The brake function is obtained by
setting the input pattern to logic low
and thus turning on the lower
DMOS switches of the enabled half-
bridges.
The PWM signal is used for chop-
ping the INPUT pattern.
The control logic circuit decodes
Hall effect sensors having different
phasing.
With the DIR jumper opened the
application achieves forward rota-
tion for motors having 60° and 120°
Hall Effect sensor electrical phasing
and the reverse rotation for motors
having 300° and 240° Hall Effect
sensor phasing.
Connecting the DIR jumper to
ground sets the reverse rotation for
motors having 60° and 120° Hall
sensors phasing and the forward
rotation for motors having 300° and
240° Hall sensor phasing.
The SW2 switch performs the start-
stop function.
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