U2102B-XFPG3Y ATMEL Corporation, U2102B-XFPG3Y Datasheet - Page 8

• Manufacturer Part Number: U2102B-XFPG3Y
• Description: Multifunction Timer IC
• Manufacturer: ATMEL Corporation

6. Reverse Phase Control
Figure 6-1.
8
U2102B
Signal Characteristics of Reverse Phase Control
0.09 V
1.1 V
V
V
Ref
Ref
V
In the case of normal phase controls, e.g., with a triac, the load current will only be switched on
at a certain phase angle after the zero crossing of the mains voltage. In the following zero cross-
ing of the current, the triac gets extinguished (switched-off) automatically. Reverse phase control
differs from this in that the load current is always switched on by a semiconductor switch (for
example, IBGT) at the zero crossing of the mains voltage and then switched back off again after
a certain phase angle . This has the advantage that the load current always rises with the
mains voltage in a defined manner and thus keeps the required interference suppression to a
minimum.
The charging current for the capacitor C
synchronization circuit recognizes a zero crossing, an increased charging current of I
is enabled which then charges C
and the charging current for C
voltage occurs later than recognized by the circuit, the load current starts to flow quite close to
the exact zero crossing of the supply voltage. While the output stage is switched on, C
charged until the control voltage, set externally at pin 4, is reached. When this condition is
reached, the output stage is switched off and C
internally. The whole process then starts again when the circuit recognizes another zero cross-
ing
mains
V
V
V
4
14
(Figure 3-3 on page
2
4
I
3
) to V
2
5.5 V. The charging current is switched off at this point and C
7).
3
is reduced to I
3
up to
3
at pin 2 is set with the resistor R
0.45 V. The output stage is switched on at this value
2
= I
3
is charged again with the increased current (I
3
. Since the actual zero crossing of the supply
3
at pin 3. When the
t
t
t
4767B–INDCO–10/05
3
is discharged
2
4
3
is
I
3
2