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Электронный компонент: U209B-x

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U209B
Rev. A3, 11-Jan-01
1 (11)
Phase-Control IC Tacho Applications
Description
The integrated circuit U209B is designed as a phase-
control circuit in bipolar technology with an internal
frequency-voltage converter. Furthermore, it has an
internal open-loop amplifier which means it can be used
for motor speed control with tacho feedback.
The U209B is a 14-pin shrink version of the U211B with
reduced features. Using the U209B, the designer is able
to realize sophisticated as well as economic motor control
systems.
Features
D Internal frequency-to-voltage converter
D Externally controlled integrated amplifier
D Automatic soft start with minimized "dead time"
D Voltage and current synchronization
D Retriggering
D Triggering pulse typ. 155 mA
D Internal supply-voltage monitoring
D Temperature-compensated reference source
D Current requirement
3 mA
Block Diagram
Control
amplifier
Voltage
monitoring
Supply
voltage
limitation
Reference
voltage
Output
pulse
Frequency-
to-voltage
converter
Phase
control unit
Soft start
10(10)
11(11)
12(12)
8(8)
7(7)
Voltage / Current
detector
Automatic
retriggering
14(16)
1(1)
4(4)
= f (V
11
)
V
S
GND
+
V
S
5(5)
6(6)
3(3)
2(2)
13(15)
9(9)
U209B
Figure 1. Block diagram (Pins in brackets refer to SO16)
Ordering Information
Extended Type Number
Package
Remarks
U209B-x
DIP14
Tube
U209B-xFP
SO16
Tube
U209B-xFPG3
SO16
Taped and reeled
U209B
Rev
. A3,
1
1-Jan-01
2 (1
1)
R
3
220 k
W
R
4
470 k
W
R
2
V
S
3.3 nF
GND
C
1
22
25 V
C
10
2.2
16 V
R
13
220
W
M
R
1
18 k
W
IN4007
D
1
2 W
TIC
236N
R
8
2 M
W
68 k
W
R
6
C
6
100 nF
2.2
16 V
C
7
C
8
220 nF
22 k
W
R
7
C
3
2.2
16 V
C
5
1 nF
R
5
1 k
W
Speed sensor
C
4
220 nF
L
N
V
M
=
230 V ~
Control
amplifier
Voltage
monitoring
Supply
voltage
limitation
Reference
voltage
Output
pulse
Frequency
to voltage
converter
Phase
control unit
Soft start
10
9
11
12
8
7
6
3
2
13
Voltage / Current
detector
Automatic
retriggering
14
1
5
4
= f (V
11
)
+
s
C
2
Actual
speed
voltage
680 k
W
R
11
100 k
W
C
9
2.2 /16 V
R
12
100 k
W
R
10
56 k
W
R
9
47 k
W
Set speed
voltage
mF
mF
mF
mF
mF
V
U209B
Figure
2. Block diagram with typical circuitry for speed regulation
U209B
Rev. A3, 11-Jan-01
3 (11)
Description
Mains Supply
The U209B is designed with voltage limiting and can
therefore be supplied directly from the mains. The supply
voltage between Pin 2 (+ pol/
) and Pin 3 builds up
across D
1
and R
1
and is smoothed by C
1
. The value of the
series resistance can be approximated using:
R
1
+
V
M
V
S
2 I
S
Further information regarding the design of the mains
supply can be found in the chapter "Design Calculations
for Mains Supply". The reference voltage source on Pin
13 of typ. 8.9 V
is derived from the supply voltage and
represents the reference level of the control unit.
Operation using an externally stabilised DC voltage is not
recommended.
If the supply cannot be taken directly from the mains
because the power dissipation in R
1
would be too large,
then the circuit shown in the following figure 3 should be
employed.
1
2
3
4
5
C
1
R
1
24 V~
~
U209B
Figure 3. Supply voltage for high current requirements
Phase Control
The function of the phase control is largely identical to
that of the well known integrated circuit U2008B. The
phase angle of the trigger pulse is derived by comparing
the ramp voltage. This is mains-synchronized by the volt-
age detector with the set value on the control input Pin 4.
The slope of the ramp is determined by C
2
and its charging
current. The charging current can be varied using R
2
on
Pin 5. The maximum phase angle
a
max
can also be ad-
justed using R
2
.
When the potential on Pin 6 reaches the nominal value
predetermined at Pin 11, a trigger pulse is generated
whose width t
p
is determined by the value of C
2
(the value
of C
2
and hence the pulse width can be evaluated by
assuming 8
ms/nF).
The current sensor on Pin 1 ensures that no pulse is gener-
ated (for operation with inductive loads) in a new half
cycle as long as the current from the previous half cycle
is still flowing in the opposite direction to the supply
voltage at that instant. This makes sure that "Gaps" in the
load current are prevented.
The control signal on Pin 11 can be in the range 0 V to
7 V (reference point Pin 2).
If V
11
= 7 V, the phase angle is at maximum =
a
max
, i.e.,
the current flow angle is a minimum. The minimum phase
angle
a
min
is when
V
11
= V
pin2
.
Voltage Monitoring
As the voltage is built up, uncontrolled output pulses are
avoided by internal voltage surveillance. At the same
time, all latches in the circuit (phase control, soft start) are
reset and the soft-start capacitor is short circuited. Used
with a switching hysteresis of 300 mV, this system guar-
antees defined start-up behaviour each time the supply
voltage is switched on or after short interruptions of the
mains supply.
Soft Start
As soon as the supply voltage builds up (t
1
), the integrated
soft start is initiated. Figure 4 shows the behaviour of the
voltage across the soft-start capacitor which is identical
with the voltage on the phase control input on Pin 11. This
behaviour guarantees a gentle start-up for the motor and
automatically ensures the optimum run-up time.
C
3
is first charged up to the starting voltage V
o
with
typically 30
mA current (t
2
).
By then reducing the
charging current to approx. 4
mA, the slope of the charging
function is substantially reduced so that the rotational
speed of the motor only slowly increases. The charging
current then increases as the voltage across C
3
increases
giving a progressively rising charging function which
accelerates the motor with increasing rotational speed.
The charging function determines the acceleration up to
the set-point. The charging current can have a maximum
value of 50
mA.
U209B
Rev. A3, 11-Jan-01
4 (11)
V
C3
t
V
12
V
0
t
1
t
tot
t
2
t
3
Figure 4. Soft start
t
1
= build-up of supply voltage
t
2
= charging of C
3
to starting voltage
t
1
+ t
2
= dead time
t
3
= run-up time
t
tot
= total start-up time to required speed
Frequency-to-Voltage Converter
The internal frequency-to-voltage converter
(f/V-converter) generates a DC signal on Pin 9 which is
proportional to the rotational speed using an AC signal
from a tacho generator or a light beam whose frequency
is in turn dependent on the rotational speed. The high
impedance input with a switch-on threshold of typ.
100 mV gives very reliable operation even when
relatively simple tacho generators are employed. The
tacho frequency is given by:
f =
n
60
n = revolutions per minute
p
= number of pulses per revolution
p[Hz]
The converter is based on the charge pumping principle.
With each negative half wave of the input signal, a
quantity of charge determined by C
5
is internally
amplified and then integrated by C
6
at the converter
output on Pin 9.
The conversion constant is determined
by C
5
, its charging voltage of V
ch
, R
6
(Pin 9) and the
internally adjusted charge amplification G
i
.
k = G
i
C
5
R
6
V
ch
The analog output voltage is given by
V
o
= k
f
where:
V
ch
= 6.7 V
G
i
= 8.3
The values of C
5
and C
6
must be such that for the highest
possible input frequency, the maximum output voltage V
0
does not exceed 6 V. The R
i
on Pin 8 is approx. 6 k
while
C
5
is charging up
.
To obtain good linearity of the
f/V converter the time constant resulting from R
i
and C
5
should be considerably less (1/5) than the time span of the
negative half cycle for the highest possible input
frequency. The amount of remaining ripple on the output
voltage on Pin 9 is dependent on C
5
, C
6
and the internal
charge amplification.
DV
O
+
G
i
V
ch
C
5
C
6
The ripple
V
o
can be reduced by using larger values of
C
6
, however, the maximum conversion speed will then
also be reduced.
The value of this capacitor should be chosen to fit the
particular control loop where it is going to be used.
Control Amplifier
The integrated control amplifier with differential input
compares the set value (Pin 10) with the instantaneous
value on Pin 9
and generates a regulating voltage on the
output Pin 11 (together with external circuitry on Pin 12)
which always tries to hold the real voltage at the value of
the set voltages. The amplifier has a transmittance of typi-
cally 110
mA/V and a bipolar current source output on Pin
11 which operates with typically
100
mA. The
amplification and frequency response are determined by
R
7
, C
7
, C
8
and R
8
(can be left out). For operation as a
power divider, C
4
, C
5
, R
6
, C
6
, R
7
, C
7
, C
8
and R
8
can be
left out. Pin 9
should be connected with Pin 11 and Pin 7
with Pin 2. The phase angle of the triggering pulse can be
adjusted using the voltage on Pin 10. An internal limiting
circuit prevents the voltage on Pin 11 from becoming
more negative than V
13
+ 1 V.
Pulse-Output Stage
The pulse-output stage is short-circuit protected and can
typically deliver currents of 125 mA. For the design of
smaller triggering currents, the function I
GT
= f (R
GT
) can
be taken from figure 14.
Automatic Retriggering
The automatic retriggering prevents half cycles without
current flow, even if the triacs are turned off earlier e.g.,
due to not exactly centered collector (brush lifter) or in the
event of unsuccessful triggering. If necessary, another
triggering pulse is generated after a time lapse of
t
PP
= 4.5 t
P
and this is repeated until either the triac fires
or the half cycle finishes.
U209B
Rev. A3, 11-Jan-01
5 (11)
General Hints and Explanation of Terms
To ensure safe and trouble-free operation, the following
points should be taken into consideration when circuits
are being constructed or in the design of printed circuit
boards.
D The connecting lines from C
2
to Pin 6 and Pin 2 should
be as short as possible, and the connection to Pin 2
should not carry any additional high current such as
the load current. When selecting C
2
, a low tempera-
ture coefficient is desirable.
D The common (earth) connections of the set-point
generator, the tacho-generator and the final inter-
ference suppression capacitor C
4
of the f/V converter
should not carry load current.
D The tacho generator should be mounted without
influence by strong stray fields from the motor.
V
V
GT
V
L
I
L
p/2
p
3/2
p
2
p
t
p
t
pp
= 4.5 t
p
Mains
Supply
Trigger
Pulse
Load
Voltage
Load
Current
F
Figure 5. Explanation of terms in phase relationship
Design Calculations for Mains Supply
The following equations can be used for the evaluation of the series resistor R
1
for worst case conditions:
R
1max
+ 0.85
V
Mmin
V
Smax
2 I
tot
R
1min
+ 0.85
V
M
V
Smin
2 I
Smax
P
(R1max)
+
(V
Mmax
V
Smin
)
2
2 R
1
where:
V
M
= Mains voltage 230 V
V
S
= Supply voltage on Pin 3
I
tot
= Total DC current requirement of the circuit
= I
S
+ I
p
+
I
x
I
Smax
= Current requirement of the IC in mA
I
p
= Average current requirement of the triggering pulse
I
x
=
Current requirement of other peripheral components
R
1
can be easily evaluated from figures 15 to 17