ICE3B0365L Datasheet, PDF (14/28 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 650V Startup Cell/Depletion CoolMOS™ and Latched off Mode

CoolSET™-F3
ICE3xxx65L
Functional Description
exceeded. Therefore the overvoltage detection is only
activated if the FB signal is outside the operating range
> 4.8V, e.g. when Open Loop happens. This means
any small voltage overshoots of V_VCC during normal
operating can not start the Latched Off Mode.
The internal Voltage Reference is switched off once
Latched Off Mode is entered in order to reduce the
current consumption of the IC as much as possible.
Latched Off Mode can only be reset by decreasing
V_VCC < 6V. In this stage, only the UVLO is working
which controls the Startup Cell by switching on/off at
V_VCCon/V_VCCoff. During this phase, the average current
consumption is only 300µA. As there is no longer a self-
supply by the auxiliary winding, VCC drops. The
Undervoltage Lockout switches on the integrated
Startup Cell when VCC falls below 8.5V. The Startup
Cell is switched off again when VCC has exceeded
15V. Once the Latched Off Mode was entered, there is
no Start Up Phase after VCC has exceeded the switch-
on level of the Undervoltage Lockout. Therefore VCC
changes between the switch-on and switch-off levels of
the Undervoltage Lockout with a saw tooth shape (see
Figure 18).
V_VCC
operating mode comparator C10 keeps the maximum
level of the CS signal at 1V. If there is a failure such as
short winding or short diode, C10 is no longer able to
limit the CS signal at 1V. C11 detects then the over
current and enters immediately the Latched Off Mode
to keep the SMPS in a safe stage.
3.6.3.2 Auto Restart Mode
SoftS
6.5V
5kΩ ^RSoftS
4.4V
1
S1
G2
C3
5.4V
Voltage
Reference
t.b.d
8.5V
I_VCCStart
t
1.05mA
V_OUT
t
Figure 18 Signals in Latched Off Mode
The Thermal Shutdown block monitors the junction
temperature of the IC. After detecting a junction
temperature higher than 140°C, Latched Off Mode is
entered.
The signals coming from the temperature detection and
VCC overvoltage detection are fed into a spike
blanking with a time constant of 8.0µs to ensure system
reliability.
Furthermore, a short winding or short diode on the
secondary side can be detected by the comparator C11
which is in parallel to the propagation delay
compensated current limit comparator C10. In normal
4.8V
C4
FB
&
Auto
Restart
G5
Mode
Control Unit
Figure 19 Auto Restart Mode
In case of Overload or Open Loop, FB exceeds 4.8V
which will be observed by C4. At this time S1 is
released that V_SoftS can increase. If V_SoftS exceeds 5.4V
which is observed by C3, Auto Restart Mode is entered
as both inputs of the gate G5 are high. In combining the
FB and SoftS signals, there is a blanking window
generated which prevents the system to enter Auto
Restart Mode due to large load jumps. This time
window is the same as for the Active Burst Mode and
can therefore be adjusted by the external C_SoftS.
In case of VCC undervoltage, the IC enters into the
Auto Restart Mode and starts a new startup cycle.
Short Optocoupler also leads to VCC undervoltage as
there is no self supply after activating the internal
reference and bias.
In contrast to the Latched Off Mode, there is always a
Startup Phase with switching cycles in Auto Restart
Mode. After this Start Up Phase, the conditions are
again checked whether the failure mode is still present.
Normal operation is resumed once the failure mode is
removed that had caused the Auto Restart Mode.
Version 2.0
14
8 May 2006