ICE3AR0680JZ Datasheet, PDF (11/34 Pages) Infineon Technologies AG – Of f -Line SMPS Cur rent Mode Cont rol ler wi th integrated 800V

CoolSET^®-F3R80
ICE3AR0680JZ
Functional Description
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.
.
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 300us 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 12).
V _{S o ftS}
V_SOFTS32
t_Soft-Start
V_SoftS
V_SoftS2
V_SoftS1
t
Gate
Driver
t
Figure 10 Soft Start Phase
When the V_VCC exceeds the on-threshold voltage, the
IC starts the Soft Start mode (Figure 10).
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 11).
Figure 12 Gate drive signal under Soft-Start Phase
In addition to Start-Up, Soft-Start is also activated at
each restart attempt during Auto Restart.
V _SoftS
V_SOFTS32
t_Soft-Start
5V
R_SoftS
SoftS
V_FB
t
4.5V
Soft Start ^{32I 8I 4I 2I}
I
Counter
V_OUT
V_OUT
t_{S ta rt-U p}
Figure 11 Soft Start Circuit
Version 2.1a
Figure 13 Start Up Phase
11
t
t
11 Jan 2012