F3 PWM controller
ICE3BS03LJG
Functional Description
3.7.3
Protection Modes
The VCC voltage is observed by comparator C1. If the
VCC voltage is > 25.5V, the overvoltage detection is
activated. It enters the latch off mode.
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 internal Voltage Reference is switched off most of
the pre-defined protection feature for the Latch off the time once Latched Off Mode is entered in order to
mode, there is also an external Latch off Enable pin for minimize the current consumption of the IC. This
customer defined Latch off protection features. The Latched Off Mode can only be reset if the VVCC < 6.23V.
Latched Off Mode can only be reset if VCC falls below In this mode, only the UVLO is working which controls
6.23V. Both modes prevent the SMPS from destructive the Startup Cell by switching on/off at VVCCon/VVCCoff
.
states.The following table shows the relationship During this phase, the average current consumption is
between possible system failures and the chosen only 250µA. As there is no longer a self-supply by the
protection modes.
VCC Overvoltage
Overtemperature
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).
Latched Off Mode
Latched Off Mode
Short Winding/Short Diode Latched Off Mode
BL pin < 0.25V
Overload
Latched Off Mode
Auto Restart Mode
Auto Restart Mode
Auto Restart Mode
Auto Restart Mode
Open Loop
VCC Undervoltage
Short Optocoupler
VVCC
18V
3.7.3.1
Latched Off Mode
10.5V
CS
BL
Spike
Latched Off
Mode Reset
VVCC < 6.23V
C11
Blanking
190ns
1.66V
IVCCStart
t
UVLO
1ms
1
0.9mA
Latched
G3
Off Mode
counter
30us
Blanking
Time
C2
T
LE
#
VOUT
t
0.25V
Latch
Enable
signal
Figure 26
Signals in Latched Off Mode
VCC
The Thermal Shutdown block monitors the junction
temperature of the IC. After detecting a junction
temperature higher than latched thermal shutdown
temperature; TjSD, the Latched Off Mode is entered.
Spike
&
C1
Blanking
25.5V
G1
30us
The signals coming from the temperature detection and
VCC overvoltage detection are fed into a spike
blanking with a time constant of 30µs in order to ensure
the 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
operating mode, comparator C10 controls the
maximum level of the CS signal at 1.06V. If there is a
Voltage
Thermal Shutdown
Reference
T >130°C
j
Control Unit
Figure 25
Latched Off Mode
Version 2.0
16
6 Dec 2007
INFINEON [ Infineon ]
