F3 PWM controller
ICE3BS03LJG
Functional Description
reset. Thus it is ensured that at every startup cycle the
soft start starts at zero.
HV
Startup Cell
VCC
3.3
Improved Current Mode
Soft-Start Comparator
PWM-Latch
C8
R
Q
FB
Driver
S
Power Management
Internal Bias
Latched Off Mode
Reset
V
VCC
< 6.23V
Power-Down Reset
Undervoltage Lockout
18V
10.5V
Q
0.6V
PWM OP
5.0V
Voltage
Reference
x3.2
Improved
Current Mode
Figure 4
Current Mode
CS
Auto Restart
Mode
Soft Start block
Active Burst
Mode
Latched Off
Mode
Current Mode means the duty cycle is controlled by the
slope of the primary current. This is done by comparing
the FB signal with the amplified current sense signal.
Figure 3
Power Management
The internal bias circuit is switched off if Latched Off
Mode or Auto Restart Mode is entered. The current
consumption is then reduced to 250µA.
Once the malfunction condition is removed, this block
will then turn back on. The recovery from Auto Restart
Mode does not require re-cycling the AC line. In case
Latched Off Mode is entered, VCC needs to be
dropped below 6.23V to reset the Latched Off Mode.
This is done usually by re-cycling the AC line.
When Active Burst Mode is entered, the internal Bias is
switched off most of the time but the Voltage Reference
is kept alive in order to reduce the current consumption
below 450µA.
Amplified Current Signal
FB
0.6V
Driver
t
T
on
t
Figure 5
Pulse Width Modulation
In case the amplified current sense signal exceeds the
FB signal, the on-time T
on
of the driver is finished by
resetting the PWM-Latch (see Figure 5).
The primary current is sensed by the external series
resistor R
Sense
inserted in the source of the external
power MOSFET. By means of Current Mode
regulation, the secondary output voltage is insensitive
Version 2.0
8
6 Dec 2007
INFINEON [ INFINEON TECHNOLOGIES AG ]
