CoolSET™-F3
ICE3B0365JG/ICE3B0565JG
Version 2.0 14 14 Nov 2006
small voltage overshoots of V
VCC
during normal
operating cannot trigger the Auto Restart Mode I.
In Order to ensure system reliability and prevent any
false activation, a blanking time is implemented before
the IC can enter into the Auto Restart Mode I. The
output of the VCC overvoltage detection is fed into a
spike blanking with a time constant of 8.0us.
The other fault detection which can result in the Auto
Restart Mode I and has this 8.0us blanking time is the
Overtemperature detection. This block checks for a
junction temperature of higher than 140°C for
malfunction operation.
Once Auto Restart Mode is entered, the internal bias is
switched off in order to reduce the current consumption
of the IC as much as possible. In this mode, the
average current consumption is only 300uA as the only
working blocks are the reference block and the
Undervoltage Lockout(UVLO) which controls the
Startup Cell by switching on/off at V
VCCon
/V
VCCoff
.
As there is no longer a self supply by the auxiliary
winding, VCC starts to drop. The UVLO switches on the
integrated Startup Cell when VCC falls below 10.3V. It
will continue to charge VCC up to 18V whereby it is
switched off again and the IC enters into the Start Up
Phase.
As long as all fault conditions have been removed, the
IC will automatically power up as usual with switching
cycle at the GATE output after Soft Start duration. Thus
the name Auto Restart Mode.
3.6.3.2 Auto Restart Mode II
Figure 17 Auto Restart Mode II
In case of Overload or Open Loop, FB exceeds 4.5V
which will be observed by C4. At this time, the external
Soft Start capacitor can now be charged further by the
integrated pull up resistor R
SoftS
via switch S3 (see
Figure 13). If V
SoftS
exceeds 4.0V which is observed by
C3, Auto Restart Mode II is entered as both inputs of
the gate G5 are high.
This charging of the Soft Start capacitor from
3.2V~3.6V to 4.0V defines a blanking window which
prevents the system from entering into Auto Restart
Mode II unintentionally during large load jumps. In this
event, FB will rise close to 5.0V for a short duration
before the loop regulates with FB less than 4.5V. This
is the same blanking time window as for the Active
Burst Mode and can therefore be adjusted by the
external C
SoftS
.
In case of VCC undervoltage, ie. VCC falls below
10.3V, the IC will be turned off with the Startup Cell
charging VCC as described earlier in this section. Once
VCC is charged above 18V, the IC will start a new
startup cycle. The same procedure applies when the
system is under Short Optocoupler fault condition, as it
will lead to VCC undervoltage.
C3
4.0V
C4
4.5V
&
G5
Control Unit
SoftS
Internal
Bias
Auto
Restart
Mode
FB
