ICE1CS02 Datasheet, PDF (15/27 Pages) Infineon Technologies AG – Combi PFC/ PWM Controller

is a built-in function and it is controlled by an internal
counter.
When the V_sense exceeds the on-threshold voltage
2.85V, the IC starts the soft start mode. The function is
realized by an internal soft start resistor, an internal
current sink and a internal counter. The amplitude of
the current sink is controlled by a timer.
The V_SoftS voltage is set by the current sinks, a resistor
and a counter such that the voltage will increase step
wisely with the increase of the counts. Every 0.8ms, the
soft start counter would send a signal to the current
sink control such that the current sink will decrease
gradually and thus the V_FB will increase gradually. The
soft start will be finished in 12msec. At the end of the
soft start period, the current sink will be switched off.
Combi PFC/ PWM Controller
ICE1CS02
Functional Description
5V
R _SoftS
SoftS
Soft Start ^{8I 4I 2I}
I
Counter
Vsense
2.85V
Figure 20 Softstart Circuit
3.5.2
PWM Section
0.47
Oscillator
Duty Cycle
max
Clock
PWM Section
V_SoftS
V_SoftS2
V_SoftS1
Soft Start
Comparator
PWM
Comparator
Current
Limiting
FF1 _{Gate Driver}
1S
G8
RQ
&
G9
Figure 19 Softstart Phase
During Soft Start phase, the voltage at pin 12 (PWM
FB) follows the soft start level with an offset, V_SoftS +
V_offset.
Figure 21
PWM Section
Gate
3.5.3
Oscillator
The switching frequency is generated by an oscillator
which composes of resistor, capacitor, current source
and current sink. The charging and discharging current
for the oscillator capacitor are internally trimmed and it
can provide a very accurate switching frequency. The
ratio of the controlled charge to discharge current is
adjusted to a maximum duty cycle of D_max=0.47 or 0.60.
Version 1.0
15
25 July 2008