ICE3B0365J Datasheet, PDF (8/26 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 650V Startup Cell/Depletion CoolMOS™

CoolSET™-F3
ICE3Bxx65J
When V_VCC falls below the off-threshold V_CCoff=10.3V
the bias circuit is switched off and the Power Down
reset let T1 discharging the soft-start capacitor C_SoftS at
pin SoftS. Thus it is ensured that at every startup cycle
the voltage ramp at pin SoftS starts at zero.
The bias circuit is switched off if Auto Restart Mode is
entered. The current consumption is then reduced to
300uA.
Once the malfunction condition is removed, this block
will then turn back on. The recovery from Auto Restart
Mode does not require disconnecting the SMPS from
the AC line.
When Active Burst Mode is entered, some internal Bias
is switched off in order to reduce the current
consumption to about 500uA while keeping a
comparator (which trigger if V_FB has exceeded 3.61V)
and the Soft Start capacitor clamped at 3.0 V as this is
necessary in this mode.
resistor R_SoftS determines the duty cycle until V_SoftS
exceeds 3.1V.
When the Soft Start begins, C_SoftS is immediately
charged up to approx. 0.8V by T2. Therefore the Soft
Start Phase takes place between 0.8V and 3.1V.
Above V_SoftsS = 3.1V there is no longer duty cycle
limitation DC_max which is controlled by comparator C7
since comparator C2 blocks the gate G7 (see Figure
5).This maximum charge current in the very first stage
when V_SoftS is below 0.8V, is limited to 0.9mA.
V_SoftS
4.0V
3.1V
max. Startup Phase
3.3
Startup Phase
0.8V
max. Soft Start Phase
3.25kΩ
5V
R_SoftS
SoftS
C_SoftS
Freq Jitter
Charging
current I_FJ
Freq Jitter
Discharging
current I_FJ
T2
T3
0.8V
Freq Jitter
Control
Soft Start
C7
Soft-Start
Comparator
&
G7
Gate Driver
C2
3.1V
0.6V
PWM OP
x3.2
CS
DC_max
t
DC₁
DC₂
t1
t2 t
Figure 5 Startup Phase
By means of this extra charge stage, there is no delay
in the beginning of the Startup Phase when there is still
no switching. Furthermore Soft Start is finished at 3.1V
to have faster the maximum power capability. The duty
cycles DC₁ and DC₂ are depending on the mains and
the primary inductance of the transformer. The
limitation of the primary current by DC₂ is related to
V_SoftS = 3.1V. But DC₁ is related to a maximum primary
current which is limited by the internal Current Limiting
with CS = 1V. Therefore the maximum Startup Phase
is divided into a Soft Start Phase until t1 and a phase
from t1 until t2 where maximum power is provided if
demanded by the FB signal.
Figure 4 Soft Start
At the beginning of the Startup Phase, the IC provides
a Soft Start duration whereby it controls the maximum
primary current by means of a duty cycle limitation. A
capacitor C_Softs in combination with the internal pull up
Version 2.3
8
8 May 2006