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U211B2/ B3
Phase Control Circuit - General Purpose Feedback
Description
The integrated circuit U211B2/ B3 is designed as a phase
control circuit in bipolar technology with an internal fre-
quency-voltage converter. Furthermore, it has an internal
control amplifier which means it can be used for speed-
regulated motor applications.
Features
D Internal frequency-to-voltage converter
D Externally-controlled integrated amplifier
D Overload limitation with a “fold back” characteristic
D Optimized soft-start function
D Tacho monitoring for shorted and open loop
D Automatic retriggering switchable
It has an integrated load limitation, tacho monitoring and
soft-start functions, etc. to realize sophisticated motor
control systems.
D Triggering pulse typ. 155 mA
D Voltage and current synchronization
D Internal supply-voltage monitoring
D Temperature reference source
D Current requirement 3 mA
Package: DIP18 - U211B2,
SO16 - U211B3
17(16)
1(1)
Voltage / Current
detector
5*)
Automatic
retriggering
Output
pulse
4(4)
11(10)
Control
+ amplifier
10(9)
14(13)
15(14)
Load limitation
speed / time
controlled
Phase
control unit
ö= f (V12)
Supply
voltage
limitation
Reference
voltage
Voltage
monitoring
6(5)
7(6)
3(3)
–VS
2(2)
GND
16(15)
controlled
current sink
Soft start
–VRef
12(11)
13(12)
Frequency-
to-voltage
converter
Pulse-blocking
tacho
monitoring
9(8) 8(7)
18*)
95 10360
Figure 1. Block diagram (Pins in brackets refer to SO16)
*) Pins 5 and 18 connected internally
TELEFUNKEN Semiconductors
Rev. A1, 29-May-96
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U211B2/ B3
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Figure 2. Speed control, automatic retriggering, load limiting, soft start
TELEFUNKEN Semiconductors
Rev. A1, 29-May-96

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U211B2/ B3
Description
Mains Supply
The U211B2 is fitted with voltage limiting and can
ătherefore be supplied directly from the mains. The supply
voltage between Pin 2 (+ pol/ ) and Pin 3 builds up
across D1 and R1 and is smoothed by C1. The value of the
series resistance can be approximated using (see
figure 2):
+R1
VM – VS
2 IS
Further information regarding the design of the mains
supply can be found in the data sheets in the appendix.
The reference voltage source on Pin 16 of typ. –8.9 V is
derived from the supply voltage and is used for
regulation.
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 R1 would be too large,
then the circuit shown in the following figure 3 should be
used.
When the potential on Pin 7 reaches the nominal value
predetermined at Pin 12, then a trigger pulse is generated
whose width tp is determined by the value of C2 (the value
of C2 and hence the pulse width can be evaluated by
assuming 8 ms/nF). At the same time, a latch is set, so that
as long as the automatic retriggering has not been
activated, then no more pulses can be generated in that
half cycle.
The current sensor on Pin 1 ensures that, for operations
with inductive loads, no pulse will be generated in a new
half-cycle as long as a 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 12 can be in the range 0 V to
–7 V (reference point Pin 2).
If V12 = –7 V then the phase angle is at maximum = amax
i.e., the current flow angle is a minimum. The phase angle
amin is minimum when V12 = V2.
~
24 V~
12345
R1 C1
95 10362
Figure 3. Supply voltage for high current requirements
Voltage Monitoring
As the voltage is built up, uncontrolled output pulses are
avoided by internal voltage surveillance. At the same
time, all of the latches in the circuit (phase control, load
limit regulation, soft start) are reset and the soft-start
capacitor is short circuited. Used with a switching
hysteresis of 300 mV, this system guarantees defined
start-up behavior each time the supply voltage is switched
on or after short interruptions of the mains supply.
Phase Control
There is a general explanation in the data sheet,
TEA1007, on the common phase control function. The
phase angle of the trigger pulse is derived by comparing
the ramp voltage (which is mains synchronized by the
voltage detector) with the set value on the control input
Pin 12. The slope of the ramp is determined by C2 and its
charging current. The charging current can be varied
using R2 on Pin 6. The maximum phase angle amax can
also be adjusted using R2.
Soft-Start
As soon as the supply voltage builds up (t1), the integrated
soft-start is initiated. The figure below shows the
behaviour of the voltage across the soft-start capacitor
and is identical with the voltage on the phase control input
on Pin 12. This behaviour guarantees a gentle start-up for
the motor and automatically ensures the optimum run-up
time.
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U211B2/ B3
VC3
V12
95 10272
V0
t1
t2
t3
ttot
t
Figure 4. Soft-start
t1 = build-up of supply voltage
t2 = charging of C3 to starting voltage
t1 + t2 = dead time
t3 = run-up time
ttot = total start-up time to required speed
C3 is first charged up to the starting voltage V0 with
mtypical 45 A current (t2). By then reducing the charging
mcurrent to approx. 4 A, 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 C3 increases giving a
progressively rising charging function which accelerates
the motor more and more strongly with increasing
rotational speed. The charging function determines the
macceleration up to the set-point. The charging current can
have a maximum value of 55 A.
Frequency to Voltage Converter
The internal frequency to voltage converter (f/V-
converter) generates a DC signal on Pin 10 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 Pin 8, compares the tacho-voltage to a
switch-on threshold of typ. –100 mV. The switch-off
threshold is given with –50 mV. The hysteresis
guarantees very reliable operation even when relatively
simple tacho-generators are used. The tacho-frequency is
given by:
+f
n
60
p (Hz)
where:
n = revolutions per minute
p = number of pulses per revolution
The converter is based on the charge pumping principle.
With each negative half wave of the input signal, a
quantity of charge determined by C5 is internally
amplified and then integrated by C6 at the converter
output on Pin 10. The conversion constant is determined
by C5, its charge transfer voltage of Vch, R6 (Pin 10) and
ƪ ƫ +the internally adjusted charge transfer gain.
Gi
I10
I9
8.3
k = Gi C5 R6 Vch
The analog output voltage is given by
@VO = k f
The values of C5 and C6 must be such that for the highest
possible input frequency, the maximum output voltage
WVO does not exceed 6 V. While C5 is charging up, the Ri
on Pin 9 is .approx. 6.7 k . To obtain good linearity of the
f/V converter the time constant resulting from Ri and C5
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 10 is dependent on C5, C6 and the internal
charge amplification.
Gi Vch
VO =
C6
C5
The ripple Vo can be reduced by using larger values of
C6. However, the increasing 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.
Pulse Blocking
The output of pulses can be blocked using Pin 18 (standby
operation) and the system reset via the voltage monitor if
V18 –1.25 V. After cycling through the switching point
hysteresis, the output is released when V18 –1.5 V
followed by a soft-start such as that after turn on.
Monitoring of the rotation can be carried out by
connecting an RC network to Pin 18. In the event of a
short or open circuit, the triac triggering pulses are cut off
by the time delay which is determined by R and C. The
Wcapacitor C is discharged via an internal resistance
Ri = 2 k with each charge transfer process of the f/V
converter. If there are no more charge transfer processes
C is charged up via R until the switch-off threshold is
exceeded and the triac triggering pulses are cut off. For
operation without trigger pulse blocking or monitoring of
the rotation, Pins 18 and 16 must be connected together.
4 (20)
TELEFUNKEN Semiconductors
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U211B2/ B3
R = 1 MW
C = 1 mF
10 V
18 17 16
15
1234
95 10363
Figure 5. Operation delay
Control Amplifier (Figure 2)
The integrated control amplifier with differential input
compares the set value (Pin 11) with the instantaneous
value on Pin 10 and generates a regulating voltage on the
output Pin 12 (together with the external circuitry on
Pin 12) which always tries to hold the actual voltage at the
value of the set voltages. The amplifier has a
mtransmittance of typically 1000 A/V and a bipolar
mcurrent source output on Pin 12 which operates with
typically ±110 A. The amplification and frequency
response are determined by R7, C7, C8 and R11 (can be left
out). For open loop operation, C4, C5, R6, R7, C7, C8 and
R11 can be omitted. Pin 10 should be connected with
Pin 12 and Pin 8 with Pin 2. The phase angle of the
triggering pulse can be adjusted using the voltage on
Pin 11. An internal limitation circuit prevents the voltage
on Pin 12 from becoming more negative than V16 + 1 V.
Load Limitation
The load limitation, with standard circuitry, provides
absolute protection against overloading of the motor. the
function of the load limiting takes account of the fact that
motors operating at higher speeds can safely withstand
large power dissipations than at lower speeds due to the
increased action of the cooling fan. Similary, consider-
ations have been made for short term overloads for the
motor which are, in practice, often required. These
finctions are not damaging and can be tolerated.
In each positive half-cycle, the circuit measures via R10
the load current on Pin 14 as a potential drop across R8
and produces a current proportional to the voltage on
Pin 14. This current is available on Pin 15 and is
integrated by C9. If, following high current amplitudes or
a large phase angle for current flow, the voltage on C9
exceeds an internally set threshold of approx. 7.3 V
(reference voltage Pin 16) then a latch is set and the load
limiting is turned on. A current source (sink) controlled
by the control voltage on Pin 15 now draws current from
a aPin 12 and lowers the control voltage on Pin 12 so that the
phase angle is increased to max.
The simultaneous reduction of the phase angle during
which current flows causes firstly: a reduction of the
rotational speed of the motor which can even drop to zero
if the angular momentum of the motor is excessively
large, and secondly: a reduction of the potential on C9
which in turn reduces the influence of the current sink on
Pin 12. The control voltage can then increase again and
bring down the phase angle. This cycle of action sets up
a “balanced condition” between the “current integral” on
Pin 15 and the control voltage on Pin 12.
Apart from the amplitude of the load current and the time
during which current flows, the potential on Pin 12 and
hence the rotational speed also affects the function of the
load limiting. A current proportional to the potential on
Pin 10 gives rise to a voltage drop across R10, via Pin 14,
so that the current measured on Pin 14 is smaller than the
actual current through R8.
This means that higher rotational speeds and higher
current amplitudes lead to the same current integral.
Therefore, at higher speeds, the power dissipation must
be greater than that at lower speeds before the internal
threshold voltage on Pin 15 is exceeded. The effect of
speed on the maximum power is determined by the
resistor R10 and can therefore be adjusted to suit each
individual application.
If, after the load limiting has been turned on, the
momentum of the load sinks below the “o-momentum”
set using R10, then V15 will be reduced. V12 can then in-
crease again so that the phase angle is reduced. A smaller
phase angel corresponds to a larger momentum of the mo-
tor and hence the motor runs up - as long as this is allowed
by the load momentum. For an already rotating machine,
the effect of rotation on the measured “current integral”
ensures that the power dissipation is able to increase with
the rotational speed. the result is: a current controlled
accelleration run-up., which ends in a small peak of accel-
leraton when the set point is reached. The latch of the load
limiting is simultaneously reset. The speed of the motor
is then again under control and it is capable of carrying its
full load. The above mentioned peak of accelleration
depends upon the ripple of actual speed voltage. A large
amount of ripple also leads to a large peak of
accelleration.
The measuring resistor R8 should have a value which
ensures that the amplitude of the voltage across it does not
exceed 600 mV.
TELEFUNKEN Semiconductors
Rev. A1, 29-May-96
5 (20)