ICE3DS01L_05 Datasheet, PDF (12/27 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 500V Startup Cell

F3
ICE3DS01L/LG
Functional Description
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 14.4%. 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
2_V
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 max. Duty Cycle}
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
5kΩ ^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 time
Propagation Delay t
Signal1
Signal2
t
Figure 14 Dynamic Voltage Threshold V_csth
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
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 G5 and G6 once V_Softs has exceeded 5.4V.
Therefore there is no entering of Auto Restart Mode possible
during this charging time of the external capacitor C_SoftS. The
same procedure happens to the external Soft Start capacitor
if a low load condition is detected by comparator C6 when
V_FB is falling below 1.32V. Only after V_SoftS has exceeded
Version 2.1
12
15 Nov 2005