ATMEL U2008B User Manual
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
Low-cost
Applications
• Low-cost Motor Control
• Domestic Appliance
1. 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.
Figure 1-1. Block Diagram with Typical Circuit: Load Current Sensing
230 V ~
R
6
Load
TIC
226
R
3
8
180 Ω
1
^
V(R6) = ±250 mV
Limiting
detector
Automatic
retriggering
Current
detector
Full wave load
current
detector
Soft start
R
330 kΩ
C
22 kΩ/2 W
R
2
7
Voltage
detector
Phase
control unit
ϕ = f(V
23
3
100 nF3.3 nF
BYT51K
D
1
α
max
R
1
8
1 MΩ
6
Mains voltage
compensation
U2008B
-V
5
)
3
Supply
voltage
limiting
Reference
-
+
R
C
4
Load current
compensation
10
voltage
Voltage
monitoring
100 kΩ
4
Set point
GND
R
7
S
22 µF/
25 V
R
47 kΩ
P
C
1
14
1
Phase-control
IC with
Soft Start
U2008B
Rev. 4712B–AUTO–10/05
Figure 1-2. Block Diagram with Typical Circuit: Soft Start
230 V ~
L
TIC
226
Load
R
180 Ω
BYT51K
D
1
R
α
max
8
470 kΩ
6
Mains voltage
compensation
Limiting
detector
R
680 kΩ
22 kΩ/2W
2
Voltage
detector
R
1
7
Automatic
retriggering
Current
detector
Phase
control unit
ϕ = f(V
)
3
U2008B
-V
5
S
C
1
100 µF/
8
3
1
current detector
Full wave load
-
+
Soft start
Supply
voltage
limiting
Reference
voltage
Voltage
monitoring
25 V
GND
4
23
P
R
68 kΩ
C
5
Soft start
4.7 µF/25 V
C
3
C
4
10
100 nF10 nF
Set point
R
220 kΩ
7
1
50 kΩ
N
2
U2008B
4712B–AUTO–10/05
2. Pin Configuration
Figure 2-1. Pinning
U2008B
ISENSE
CONTROL
GND
Table 2-1. Pin Description
Pin Symbol Function
1 ISENSE Load current sensing
2Cϕ Ramp voltage
3 CONTROL Control input/compensation output
4 GND Ground
5 -VS Supply voltage
6Rϕ Ramp current adjustment
7 VSYNC Voltage synchronization
8 OUTPUT Trigger output
Cϕ
1
2
U2008B
3
4
8
7
6
5
OUTPUT
VSYNC
Rϕ
- VS
2.1 Mains Supply, Pin 5
The integrated circuit U2008B, which also contains voltage limiting, can be connected via D1 and
to the mains supply, see Figure 1-2 on page 2. Supply voltage, between Pin 4 (pos., ⊥) and
R
1
Pin 5, is smoothed by C
The series resistance R1 can be calculated as follows:
R
1max
where:
V
M
V
Smax
I
tot
I
Smax
I
x
Operation with externally stabilized DC voltage is not recommended.
.
1
–
V
MVSmax
------------------------------
0.85
×=
2I
×
tot
= Mains voltage
= Maximum supply voltage
= I
+ Ix = Total current compensation
Smax
= Maximum current consumption of the IC
= Current consumption of the external components
4712B–AUTO–10/05
3
2.2 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 optimum run-up time.
2.3 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
on the control input, Pin 3. The slope of the ramp is determined by C
ϕ.
at Pin 2 with the set value
2
and its charging current I
3
The charging current can be regulated, changed or altered using R
The maximum phase angle, α
using R
(see Figure 5-1 on page 7).
8
When the potential on Pin 2 reaches the set point level of Pin 3, a trigger pulse is generated
whose pulse width, t
the same time, a latch is set with the output pulse, as long as the automatic retriggering 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
at its maximum amax, i.e., the current flow angle is minimum. The minimum phase angle amin is
set with V
≥ -1 V.
3
2.4 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
2.5 Current Synchronization, Pin 8
Current synchronization fulfils two functions:
at Pin 6.
8
, (minimum current flow angle ϕ
max
, is determined from the value of C3 (tp = 9 µs/nF, Figure 5-3 on page 8). At
p
, until the triac remains reliably triggered.
pp/tp
) can also be adjusted by
min
= -9 V the phase angle is
3
• 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 evaluates 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
4712B–AUTO–10/05
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