ICE3A1065ELJ Datasheet, PDF (17/29 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 650V CoolMOS

CoolSET^®-F3
ICE3A1065ELJ
Functional Description
3.7.3
Protection Modes
The IC provides several protection features which are
separated into two categories. Some enter Latched Off
Mode and the others enter Auto Restart Mode. Besides
the pre-defined protection feature for the Latch off
mode, there is also an external Latch off Enable pin for
customer defined Latch off protection features. The
Latched Off Mode can only be reset if VCC falls below
6.23V. Both modes prevent the SMPS from destructive
states.The following table shows the relationship
between possible system failures and the chosen
protection modes.
VCC Overvoltage
Latched Off Mode
Overtemperature
Latched Off Mode
Short Winding/Short Diode Latched Off Mode
External latch enable
Latched Off Mode
Overload
Auto Restart Mode
Open Loop
Auto Restart Mode
VCC Undervoltage
Auto Restart Mode
Short Optocoupler
Auto Restart Mode
3.7.3.1 Latched Off Mode
The VCC voltage is observed by comparator C1 while
the FB voltage is monitored by the comparator C4. If
the VCC voltage is > 24V and the FB is > 4.5V, the
overvoltage detection is activated. That means the
overvoltage detection is only activated if the FB signal
is outside the operating range > 4.5V, e.g. when Open
Loop happens. The logic can eliminate the possible of
entering Latch off mode if there is a small voltage
overshoots of V_VCC during normal operating.
The internal Voltage Reference is switched off most of
the time once Latched Off Mode is entered in order to
minimize the current consumption of the IC. This
Latched Off Mode can only be reset if the V_VCC < 6.23V.
In this mode, 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 250µA. As there is no longer a self-supply by the
auxiliary winding, the VCC drops. The Undervoltage
Lockout switches on the integrated Startup Cell when
VCC falls below 10.5V. The Startup Cell is switched off
again when VCC has exceeded 18V. Once the Latched
Off Mode was entered, there is no Start Up Phase
whenever the VCC exceeds the switch-on level of the
Undervoltage Lockout. Therefore the VCC voltage
changes between the switch-on and switch-off levels of
the Undervoltage Lockout with a saw tooth shape (see
Figure 26).
CS
1.66V ^C11
Spike
Blanking
190ns
Latched Off
Mode Reset
V_VCC < 6.23V
V_VCC
18V
UVLO
1
Latched
10.5V
1ms
G3
Off Mode
counter
BL
I_VCCStart
t
8us
T_LE
C2
Blanking
#
Time
0.9mA
0.1V
Latch
Enable
signal
VCC
C1
&
Spike
Blanking
24V
G1
8.0us
V_OUT
t
4.5V
C4
FB
Thermal Shutdown
T_j >140°C
Voltage
Reference
Control Unit
Figure 25 Latched Off Mode
Figure 26 Signals in Latched Off Mode
The Thermal Shutdown block monitors the junction
temperature of the IC. After detecting a junction
temperature higher than latched thermal shutdown
temperature; T_jSD, the 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 in order to
ensure the system reliability.
Version 2.1
17
12 May 2009