U2006B.pdf

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Features
• Full Wave Current Sensing
• Compensated Mains Supply Variations
• Variable Soft Start or Load-current Sensing
• Voltage and Current Synchronization
• Switchable Automatic Retriggering
• Triggering Pulse Typically 125 mA
• Internal Supply-voltage Monitoring
• Current Requirement 3 mA
Applications
• Low-cost Motor Control
• Domestic Appliance
Low-cost
Phase-control
IC with
Soft Start
Description
The U2008B is designed as a phase-control circuit in bipolar technology. It enables
load-current detection as well as mains-compensated phase control. Motor control
with load-current feedback and overload protection are preferred applications.
U2008B
Figure 1. Block Diagram with Typical Circuit: Load Current Sensing
230 V ~
22 k
/2 W
BYT51K
R 2
R 1 D 1
max
R 8
330 k
1 M
Load
7
6
Limiting
detector
Voltage
detector
Mains voltage
compensation
Automatic
retriggering
U2008B
Phase
control unit
5
-V S
Current
detector
TIC
226
= f(V 3 )
C 1
R 3
8
Supply
voltage
limiting
Reference
voltage
22 µF/
25 V
180
4
GND
Full wave load
current
+
-
1
detector
Soft start
Voltage
monitoring
R 14
47 k
2
3
R 10 100 k
Set point
P 1
V(R6) = ±250 mV
R 6
C 3
C 4
Load current
compensation
R 7
3.3 nF
100 nF
Rev. 4712A–AUTO–05/03
1
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Figure 2. Block Diagram with Typical Circuit: Soft Start
230 V ~
22 k
/2W
BYT51K
L
R 1
D 1
R 8
R 2
680 k
max
470 k
Load
7
6
Limiting
detector
Voltage
detector
Mains voltage
compensation
Automatic
retriggering
U2008B
Phase
control unit
5
-V S
Current
detector
TIC
226
= f(V 3 )
C 1
F/
25 V
R 3
8
Supply
voltage
limiting
180
4
GND
Full wave load
current detector
-
Reference
voltage
+
1
Soft start
Voltage
monitoring
2
3
C 5
R 10
68 k
Set point
P 1
Soft start
4.7
50 k
F/25 V
C 3
C 4
R 7
10 nF
100 nF
220 k
N
2
U2008B
4712A–AUTO–05/03
100
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U2008B
Pin Configuration
Figure 3. Pinning
ISENSE
1
8
OUTPUT
C
2
7
VSYNC
U2008B
CONTROL
3
6
R
GND
4
5
- VS
Pin Description
Pin
Symbol
Function
1
ISENSE
Load current sensing
2
C
Ramp voltage
3
CONTROL Control input/compensation output
4
GND
Ground
5
-VS
Supply voltage
6
R
Ramp current adjustment
7
VSYNC
Voltage synchronization
8
OUTPUT
Trigger output
Mains Supply, Pin 5,
The integrated circuit U2008B, which also contains voltage limiting, can be connected
via D 1 and R 1 to the mains supply. Supply voltage, between Pin 4 (pos.,
) and Pin 5, is
smoothed by C 1 .
The series resistance R1 can be calculated as follows:
R 1max
=
0.85
------------------------------
–
2 tot
V Smax
where:
V M
= Mains voltage
V Smax
= Maximum supply voltage
I tot
= I Smax + I x = Total current compensation
I Smax
= Maximum current consumption of the IC
I x
= Current consumption of the external components
Operation with externally stabilized DC voltage is not recommended.
3
4712A–AUTO–05/03
V M
732695465.013.png
Voltage Monitoring
When the voltage is built up, uncontrolled output pulses are avoided by internal voltage
monitoring. Apart from that, all latches of the circuit (phase control, load limit regulation)
are reset and the soft start capacitor is short circuited. This guarantees a specified start-
up behavior each time the supply voltage is switched on or after short interruptions of
the mains supply. Soft start is initiated after the supply voltage has been built up. This
behavior guarantees a gentle start-up for the motor and automatically ensures the opti-
mum run-up time.
Phase Control, Pin 6
The function of the phase control is identical to that of the well-known IC U211B. The
phase angle of the trigger pulse is derived by comparing the ramp voltage V 2 at Pin 2
with the set value on the control input, Pin 3. The slope of the ramp is determined by C 3
and its charging current I
.
The charging current can be regulated, changed or altered using R 8 at Pin 6. The maxi-
mum phase angle,
min ) can also be adjusted by
using R 8 (see Figure 5) .
When the potential on Pin 2 reaches the set point level of Pin 3, a trigger pulse is gener-
ated whose pulse width, t p , is determined from the value of C 3 (t p = 9 µs/nF, see Figure
7) . At the same time, a latch is set with the output pulse, as long as the automatic retrig-
gering has not been activated, then no more pulses can be generated in that half cycle.
Control input at Pin 3 (with respect to Pin 4) has an active range from -9 V to -2 V. When
V 3 = -9 V the phase angle is at its maximum amax, i.e., the current flow angle is mini-
mum. The minimum phase angle amin is set with V 3
-1 V.
Automatic Retriggering
The current-detector circuit monitors the state of the triac after triggering by measuring
the voltage drop at the triac gate. A current flow through the triac is recognized when the
voltage drop exceeds a threshold level of typically 40 mV.
If the triac is quenched within the relevant half wave after triggering (for example owing
to low load currents before or after the zero crossing of current wave, or for commutator
motors, owing to brush lifters), the automatic retriggering circuit ensures immediate
retriggering, if necessary with a high repetition rate, t pp /t p , until the triac remains reliably
triggered.
Current Synchronization,
Pin 8
Current synchronization fulfils two functions:
• Monitoring the current flow after triggering. In case the triac extinguishes again or it
does not switch on, automatic triggering is activated as long as triggering is
successful.
• Avoiding triggering due to inductive load. In the case of inductive load operation, the
current synchronization ensures that in the new half wave no pulse is enabled as
long as there is a current available from the previous half wave, which flows from the
opposite polarity to the actual supply voltage.
A special feature of the IC is the realization of current synchronization. The device eval-
uates the voltage at the pulse output between the gate and reference electrode of the
triac. This results in saving the separate current synchronization input with specified
series resistance.
4
U2008B
4712A–AUTO–05/03
max , (minimum current flow angle
732695465.014.png
U2008B
Voltage Synchronization
with Mains Voltage
Compensation, Pin 7
The voltage detector synchronizes the reference ramp with the mains supply voltage. At
the same time, the mains-dependent input current at Pin 7 is shaped and rectified inter-
nally. This current activates automatic retriggering and at the same time is available at
Pin 3 (see Figure 9 ). By suitable dimensioning, it is possible to attain the specified com-
pensation effect. Automatic retriggering and mains voltage compensation are not
activated until
increases to 8 V. The resistance R sync. defines the width of the
zero voltage cross-over pulse, synchronization current, and hence the mains supply
voltage compensation current. If the mains voltage compensation and the automatic
retriggering are not required, both functions can be suppressed by limiting
V 7 - V 4
7
V (see Figure 4) .
Figure 4. Suppression of Automatic Retriggering and Mains Voltage Compensation
Mains
R 2
7
2x
BZX55
C6V2
U2008B
4
A further feature of the IC is the selection between soft start and load-current compen-
sation. Soft start is possible by connecting a capacitor between Pin 1 and Pin 4 (see
Figure 8) . In the case of load-current compensation, Pin 1 is directly connected with
resistance R 6 , which is used for sensing load current.
Load Current Detection,
Pin 1
The circuit continuously measures the load current as a voltage drop at resistor R 6 . The
evaluation and use of both half waves results in a quick reaction to load-current change.
Due to voltage at resistor R 6 , there is an increase of input current at Pin 1. This current
increase controls the internal current source, whose positive current values are avail-
able at Pin 3 (see Figure 11) . The output current generated at Pin 3 contains the
difference from the load-current detection and the mains-voltage compensation (see
. An
increase of load current results in a decrease of the control angle. This avoids a
decrease in revolution by increasing the load as well as an increase of revolution by the
increment of mains supply voltage.
5
4712A–AUTO–05/03
V 7 - V 4
The effective control voltage is the final current at Pin 3 together with the desired value
network. An increase of mains voltage causes an increase of the control angle
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