ICE2A165 Datasheet, PDF (9/23 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 650V/800V CoolMOS™

6.5V
R _FB
Soft-Start Com parator
FB
PW M -Latch
O p to c o u p le r
PW M Comparator
0 .8 V
PWM OP
Isense
x3.65
Im p ro ved
Current Mode
Figure 8 PWM Controlling
3.3
Soft-Start
V _SoftS
5.6V
5.3V
T _Soft-Start
G ate Driver
t
CoolSET™-F2
ICE2A165/265/365
ICE2A180/280
Functional Description
pullup resistor R_Soft-Start. The Soft-Start-Comparator
compares the voltage at pin SoftS at the negative input
with the ramp signal of the PWM-OP at the positive
input. When Soft-Start voltage V_SoftS is less than
Feedback voltage V_FB the Soft-Start-Comparator limits
the pulse width by reseting the PWM-Latch (see Figure
9). In addition to Start-Up, Soft-Start is also activated at
each restart attempt during Auto Restart. By means of
the above mentioned C_Soft-Start the Soft-Start can be
defined by the user. The Soft-Start is finished when
V_SoftS exceeds 5.3V. At that time the Protection Unit is
activated by Comparator C4 and senses the FB by
Comparator C3 wether the voltage is below 4.8V which
means that the voltage on the secondary side of the
SMPS is settled. The internal Zener Diode at SoftS with
breaktrough voltage of 5.6V is to prevent the internal
circuit from saturation (see Figure 10).
5.6V
S o ftS
6 .5 V
Power-Up Reset
R _Soft-Start
E rro r-L a tc h
RQ
6.5V
C4
5 .3 V
G2
SQ
4 .8 V
R _FB
FB
C3
C lo c k
RQ
G ate
D river
SQ
PW M -Latch
Figure 10 Activation of Protection Unit
The Start-Up time T_Start-Up within the converter output
voltage V_OUT is settled must be shorter than the Soft-
Start Phase T_Soft-Start (see Figure 11).
C _{Soft − Start}
=
T _{Soft − Start}
R _{Soft − Start} × 1,69
By means of Soft-Start there is an effective
minimization of current and voltage stresses on the
integrated CoolMOS™, the clamp circuit and the output
overshoot and prevents saturation of the transformer
during Start-Up.
t
Figure 9 Soft-Start Phase
The Soft-Start is realized by the internal pullup resistor
R_Soft-Start and the external Capacitor C_Soft-Start (see
Figure 2). The Soft-Start voltage V_SoftS is generated by
charging the external capacitor C_Soft-Start by the internal
Datasheet
9
September 2001