T2117

Manufacturer Part NumberT2117
DescriptionStandard Zero Crossing Switch, Low-cost Application
ManufacturerATMEL Corporation
T2117 datasheet
 


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T2117
Pin Description
1
Ramp
2
C
Ramp
T2117
POSIN
3
NEGIN
4
Figure 2. Pinning
Pin
Symbol
Function
1
Ramp
Ramp output
2
C
Ramp capacitor
Ramp
3
POSIN
Non-inverting comparator input
4
NEGIN
Inverting comparator input
5
V
Supply voltage
S
6
Output
Trigger pulse output
7
GND
Ground
8
V
Voltage synchronization
sync
General Description
The integrated circuit T2117 is a triac controller for zero-
crossing mode. It is designed to control power in
switching resistive loads of mains supplies.
Information regarding supply sync. is provided at Pin 8
via resistor R
. To avoid DC load on the mains, the full-
Sync
wave logic guarantees that complete mains cycles are
used for load switching.
A fire pulse is released when the inverting input of the
comparator is negative (Pin 4) with respect to the non-
inverting input (Pin 3) and internal reference voltage. A
ramp generator with free selectable duration can be
performed by capacitor C
at Pin 2. The ramp function is
2
used for open-loop control (figure 4), but also for applica-
tion with proportional band regulation (figure 11). Ramp
voltage available at capacitor C
is decoupled across the
2
emitter follower at Pin l. To maintain the lamp flicker
specification, ramp duration is adjusted according to the
controlling load. In practice, interference should be
avoided (temperature control). Therefore, a two-point
control is preferred to proportional control. One can use
internal reference voltage for simple applications. In that
case, Pin 3 is inactive and connected to Pin 7 (GND), see
figure 13.
2 (11)
8
V
sync
7
GND
Output
6
R
4
V
5
S
V
1
–1.6 V
–7.6 V
Figure 4. Threshold voltage of the ramp at V
Triac Firing Current (Pulse)
This depends on the triac requirement. It can be limited
with gate series resistance which is calculated as follows:
 7.5 V – V
R
Gmax
where:
V
= Gate voltage
G
I
= Maximum gate current
Gmax
I
= Average gate current
p
t
= Firing pulse width
p
T
= Mains period duration
Firing Pulse Width t
This depends on the latching current of the triac and its
load current. The firing pulse width is determined by the
zero-crossing detection which can be influenced with the
help of sync. resistance, R
2
t
=
p
w
T2117
Ramp
1
control
2
C
2
–V
S
Figure 3. Pin 1 internal network
t
Final voltage
V
min
Initial voltage
T
V
max
= –8.8 V
S
– 36 W
Gmax
I
Gmax
I
Gmax
I
=
t
P
p
T
(Figure 5)
p
, (figure 6).
sync
I
V
L
M
arc. sin
P 2
Rev. A2, 17-Dec-01