ICE3DS01L_05 Datasheet, PDF (9/27 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 500V Startup Cell

F3
ICE3DS01L/LG
Functional Description
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 internal Voltage Reference is switched off if Latched
Off Mode or Auto Restart Mode is entered. The current
consumption is then reduced to 300µA.
When Active Burst Mode is entered the internal Bias is
switched off in order to reduce the current consumption
below 1.1mA while keeping the Voltage Reference still
active as this is necessary in this mode.
In case Latched Off Mode is entered VCC needs to be
lowered below 6V to reset the Latched Off Mode. This is
done usually by disconnecting the SMPS from the AC line.
maximum charge current in the very first phase when V_SoftS
is below 1V is limited to 1.9mA.
V_SoftS
5.4V
4V
max. Startup Phase
1V
max. Soft Start Phase
3.3
Startup Phase
DC_max
t
3.25kΩ
6.5V
DC₁
DC₂
SoftS
R_SoftS
T2
T3
1V
C_SoftS
Soft Start
C7
Soft-Start
Comparator
&
G7
Gate Driver
C2
4V
0.85V
x3.7
CS
PWM OP
t1
t2 t
Figure 6 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 4V 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 = 4V. 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 5
Soft Start
During the Startup Phase a Soft Start is provided. A signal
V_SoftS which is generated by the external capacitor C_Softs in
combination with the internal pull up resistor R_SoftS
determines the duty cycle until V_SoftS exceeds 4V.
In the beginning C_SoftS is immediately charged up to approx.
1V by T2. Therefore the Soft Start Phase takes place between
1V and 4V. Above V_SoftsS = 4V there is no longer duty cycle
limitation DC_max is controlled by comparator C7 as
comparator C2 blocks the gate G7 (see Figure 6).The
Version 2.1
9
15 Nov 2005