ICE3DS01L Datasheet, PDF (15/27 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 500V Startup Cell

F3
ICE3DS01L/LG
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. Therewith
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. In 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. As 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 19).
V_VCC
15V
8.5V
I_VCCStart
t
1.05mA
V_OUT
t
Figure 19 Signals in Latched Off Mode
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 short winding and 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
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
5k
R_SoftS
4.4V
1
S1
G2
Voltage
Reference
C3
5.4V
4.8V
C4
FB
&
Auto
Restart
G5
Mode
Control Unit
Figure 20 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 UVLO starts a new
startup cycle.
Short Optocoupler leads to VCC undervoltage as there
is now 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 is still present.
Normal operation is proceeded once the failure mode
is removed that leads to Auto Restart Mode.
Version 2.0
15
15 May 2003