ICE3B0365J Datasheet, PDF (11/26 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 650V Startup Cell/Depletion CoolMOS™

CoolSET™-F3
ICE3Bxx65J
Current Limiting is now possible in a very accurate way.
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 11).
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 11 Overcurrent Shutdown
The Propagation Delay Compensation is realized by
means of a dynamic threshold voltage V_csth (see Figure
12). In case of a steeper slope the switch off of the
driver is earlier to compensate the delay.
V_{OSC 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
3.0V
S1
5V
S3
R_SoftS
Frequency
S2
Jitter
C3
4.0V
4.5V
C4
&
Auto
Restart
G5
Mode
V_Sense
V_csth
off time
Propagation Delay t
Signal1
Signal2
t
Figure 12 Dynamic Voltage Threshold V_csth
FB
C5
1.35V
Active
Burst
Mode
&
G6
Control Unit
Figure 13 Adjustable Blanking Window
V_SoftS swings between 3.2V and 3.6V after the SMPS is
settled and S2 is on while S3 is off, this is due to the
frequency jittering function that is making use of the
Soft Start pin. If overload occurs V_FB is exceeding 4.5V.
Auto Restart Mode can’t be entered as the gate G5 is
still blocked by the comparator C3. But after V_FB has
Version 2.3
11
8 May 2006