ICE2A0565 Datasheet, PDF (16/36 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 650V/ 800V CoolMOS

CoolSET™-F2
Functional Description
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.
3.8.2
Overvoltage due to Open Loop with
No Load
normal operation mode is prevented from overvoltage
detection due to varying of VCC concerning the
regulation of the converter output. When the voltage
V_SoftS is above 4.0V the overvoltage detection by C1 is
deactivated.
VCC
Open loop & no load condition
5µs Blanking
FB
4.8V
Failure
Detection
SoftS
5.3V
4.0V
Driver
t
Soft-Start Phase
Overvoltage
Detection Phase
T_Burst2
t
T_Restart
VCC
16.5V
13.5V
8.5V
Overvoltage Detection
t
6.5V
C1
16.5V
R_Soft-Start
SoftS
4.0V
C2
Error Latch
G1
C_Soft-Start
T1
Power Up Reset
Figure 24 Overvoltage Detection
3.8.3 Thermal Shut Down
Thermal Shut Down is latched by the Error-Latch when
junction temperature T_j of the pwm controller is
exceeding an internal threshold of 140°C. In that case
the IC switches in Auto Restart Mode.
t
Figure 23 Auto Restart Mode
Figure 23 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 24).The overvoltage detection
is provided by Comparator C1 only in the first time
during the Soft-Start Phase till the Soft-Start voltage
exceeds the threshold of the Comparator C2 at 4.0V
and the voltage at pin FB is above 4.8V. When VCC
exceeds 16.5V during the overvoltage detection phase
C1 can set the Error-Latch and the Burst Phase during
Auto Restart Mode is finished earlier. In that case
T_Burst2 is shorter than T_Soft-Start. By means of C2 the
Note:
All the values which are mentioned in the
functional description are typical. Please refer
to Electrical Characteristics for min/max limit
values.
Version 2.6
16
25 Dec 2006