ICE3AR10080CJZ Datasheet, PDF (11/33 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 800V CoolMOS® and Startup cell (brownout & CCM) in DIP-7

CoolSET^®-F3R80
ICE3AR10080CJZ
Functional Description
3.4
Startup Phase
Soft Start counter
SoftS
Soft Start
The function is realized by an internal Soft Start
resistor, an current sink and a counter. And the
amplitude of the current sink is controlled by the
counter (Figure 12).
5V
SoftS
R_SoftS
Soft Start
Soft-Start
C om parator
C7
&
G7
Gate Driver
Soft Start ^{32I 8I 4I 2I}
I
Counter
0.6V
x3.25
CS
PWM OP
Figure 10 Soft Start
In the Startup Phase, the IC provides a Soft Start
period to control the primary current by means of a duty
cycle limitation. The Soft Start function is a built-in
function and it is controlled by an internal counter.
.
Figure 12 Soft Start Circuit
After the IC is switched on, the V_SoftS voltage is
controlled such that the voltage is increased step-
wisely (32 steps) with the increase of the counts. The
Soft Start counter would send a signal to the current
sink control in every 300ms such that the current sink
decrease gradually and the duty ratio of the gate drive
increases gradually. The Soft Start will be finished in
10ms (t_Soft-Start) after the IC is switched on. At the end of
the Soft Start period, the current sink is switched off.
Within the soft start period, the duty cycle is increasing
from zero to maximum gradually (see Figure 13).
V _{S oftS}
V SOFTS32
t_Soft-Start
V _SoftS
V _SoftS2
V _SoftS1
t
Gate
Driver
Figure 11 Soft Start Phase
When the V_VCC exceeds the on-threshold voltage, the
IC starts the Soft Start mode (Figure 11).
t
Figure 13 Gate drive signal under Soft-Start Phase
Version 2.0
11
11 Jan 2012