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ICE3A1065 Datasheet, PDF (15/32 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 650V Startup Cell/ Depletion CoolMOS™
CoolSET™-F3
Functional Description
Current Limiting is now possible in a very accurate way.
E.g. Ipeak = 0.5A with RSense = 2. Without Propagation
Delay Compensation the current sense threshold is set
to a static voltage level Vcsth=1V. A current ramp of
dI/dt = 0.4A/µs, that means dVSense/dt = 0.8V/µs, and a
propagation delay time of i.e. tPropagation Delay =180ns
leads then to an Ipeak overshoot of 14.4%. By means of
propagation delay compensation the overshoot is only
about 2% (see Figure 15).
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
dVSense
dt
2V
s
Figure 15 Overcurrent Shutdown
The Propagation Delay Compensation is realized by
means of a dynamic threshold voltage Vcsth (see Figure
16). In case of a steeper slope the switch off of the
driver is earlier to compensate the delay.
VOSC max. Duty Cycle
3.6 Control Unit
The Control Unit contains the functions for Active Burst
Mode and Auto Restart 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, the IC avoids entering
into these two modes accidentally. Furthermore it also
provides a certain time whereby the overload detection
is delayed. This delay is useful for applications which
normally works with a low current and occasionally
require a short duration of high current.
3.6.1
Adjustable Blanking Window
SoftS
6.5V
5k RSoftS
4.4V
1
S1
G2
C3
5.4V
off time
4.8V
C4
&
Auto
Restart
G5
Mode
VSense
Vcsth
Propagation Delay
t
Signal1
Signal2
t
FB
C5
1.32V
Active
Burst
Mode
&
G6
Control Unit
Figure 16 Dynamic Voltage Threshold Vcsth
Figure 17 Adjustable Blanking Window
VSoftS is clamped at 4.4V by the closed switch S1 after
the SMPS is settled. If overload occurs VFB is
exceeding 4.8V. Auto Restart Mode can’t be entered as
the gate G5 is still blocked by the comparator C3. But
after VFB has exceeded 4.8V the switch S1 is opened
Version 2.3
15
02 Apr 2013