ICE3DS01L Datasheet, PDF (12/27 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 500V Startup Cell

F3
ICE3DS01L/LG
Functional Description
the overshoot dependency on dI/dt of the rising primary
current. That means the propagation delay time
between exceeding the current sense threshold V_csth
and the switch off of the external Power Switch is
compensated over temperature within a wide range.
Current Limiting is now possible in a very accurate way
(see Figure 13).
E.g. I_peak = 0.5A with R_Sense = 2. Without Propagation
Delay Compensation the current sense threshold is set
to a static voltage level V_csth=1V. A current ramp of
dI/dt = 0.4A/µs, that means dV_Sense/dt = 0.8V/µs, and a
propagation delay time of i.e. t_{Propagation Delay} =180ns
leads then to an I_peak overshoot of 12%. By means of
propagation delay compensation the overshoot is only
about 2% (see Figure 13).
V
1,3
1,25
1,2
1,15
1,1
1,05
1
0,95
0,9
0
with compensation
without compensation
0,2 0,4 0,6 0,8
1 1,2 1,4 1,6 1,8
dV_Sense
dt
2V
µs
Figure 13 Overcurrent Shutdown
The Propagation Delay Compensation is realized by
means of a dynamic threshold voltage V_csth (see Figure
14). In case of a steeper slope the switch off of the
driver is earlier to compensate the delay.
V _{OSC m ax. Duty Cycle}
3.6
Control Unit
The Control Unit contains the functions for Active Burst
Mode, Auto Restart Mode and Latched Off Mode. The
Active Burst Mode and the Auto Restart Mode are
combined with an Adjustable Blanking Window which is
depending on the external Soft Start capacitor. By
means of this Adjustable Blanking Window an
accidentally entering of the Active Burst Mode is
avoided. Furthermore the overload detection can be
deactivated for a certain time.
3.6.1
Adjustable Blanking Window
SoftS
6.5V
5k ^RSoftS
4.4V
1
&
S1
G2
G4
C3
5.4V
4.8V
C4
&
Auto
Restart
G5
Mode
Active
Burst
Mode
V_Sense
V _csth
off tim e
Propagation D elay t
Figure 14
S ig n a l1
S ig n a l2
t
Dynamic Voltage Threshold V_csth
Version 2.0
12
FB
C6
1.32V
&
G6
Control Unit
Figure 15 Adjustable Blanking Window
V_SoftS is clamped at 4.4V by the closed switch S1 after
the SMPS is settled. If overload occurs V_FB is
exceeding 4.8V. Auto Restart Mode can’t be entered as
the gate G5 is still blocked by the comparator C3. But
after V_FB has exceeded 4.8V the switch S1 is opened
via the gate G2. The external Soft Start capacitor can
now be charged further by the integrated pull up
resistor R_SoftS. The comparator C3 releases the gates
15 May 2003