ICE2AS01_06 Datasheet, PDF (13/24 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller

ICE2AS01/S01G
ICE2BS01/S01G
Functional Description
6.5V
Power Up Reset
SoftS
R_Soft-Start
C_Soft-Start
T1
FB
C4
5.3V
4.8V
C3
R_FB
6.5V
Error-Latch
G2
3.8.2
Overvoltage due to open loop with
no load
Open loop & no load condition
5µs Blanking
FB
4.8V
Failure
Detection
SoftS
t
Soft-Start Phase
5.3V
4.0V
Overvoltage
Detection Phase
Figure 20 FB-Detection
The detection is activated by C4 when the voltage at
pin SoftS exceeds 5.3V. Till this time the IC operates in
the Soft-Start Phase. After this phase the comparator
C3 can set the Error-Latch in case of open loop or
overload which leads the feedback voltage V_FB to
exceed the threshold of 4.8V. After latching VCC
decreases till 8.5V and inactivates the IC. At this time
the external Soft-Start capacitor is discharged by the
internal transistor T1 due to Power Down Reset. When
the IC is inactive VCC increases till V_CCon = 13.5V by
charging the Capacitor C_VCC by means of the Start-Up
Resistor R_Start-Up. Then the Error-Latch is reset by
Power Up Reset and the external Soft-Start capacitor
C_Soft-Start is charged by the internal pullup resistor R_Soft-
Start^{. During the Soft-Start Phase which ends when the}
voltage at pin SoftS exceeds 5.3V the detection of
overload and open loop by C3 and G2 is inactive. In this
way the Start Up Phase is not detected as an overload.
But the Soft-Start Phase must be finished within the
Start Up Phase to force the voltage at pin FB below the
failure detection threshold of 4.8V.
Driver
T_Burst2
t
T_Restart
VCC
16.5V
13.5V
8.5V
Overvoltage Detection
t
t
Figure 21 Auto Restart Mode
Figure 21 shows the Auto Restart Mode for open loop
and no load condition. In case of this failure mode the
converter output voltage increases and also VCC. An
additional protection by the comparators C1, C2 and
the AND-gate G1 is implemented to consider this
failure mode (see Figure 22).
Datasheet
13
Preliminary Data
30 Jun 2006