ICE3B0365J_13 datasheet(8/28 Pages) INFINEON

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CoolSET®-F3

ICE3Bxx65J

Version 2.9

25 Mar 2013

When V

VCC falls below the off-threshold VCCoff=10.3V

the bias circuit is switched off and the Power Down

reset let T1 discharging the soft-start capacitor C

SoftS at

pin SoftS. Thus it is ensured that at every startup cycle

the voltage ramp at pin SoftS starts at zero.

The bias circuit is switched off if Auto Restart Mode is

entered. The current consumption is then reduced to

300uA.

Once the malfunction condition is removed, this block

will then turn back on. The recovery from Auto Restart

Mode does not require disconnecting the SMPS from

the AC line.

When Active Burst Mode is entered, some internal Bias

is switched off in order to reduce the current

consumption

about

500uA

while

keeping

comparator (which trigger if V

FB has exceeded 3.61V)

and the Soft Start capacitor clamped at 3.0 V as this is

necessary in this mode.

3.3

Startup Phase

Figure 4

Soft Start

At the beginning of the Startup Phase, the IC provides

a Soft Start duration whereby it controls the maximum

primary current by means of a duty cycle limitation. A

capacitor C

Softs in combination with the internal pull up

resistor R

SoftS determines the duty cycle until VSoftS

exceeds 3.1V.

When the Soft Start begins, C

SoftS

is immediately

charged up to approx. 0.8V by T2. Therefore the Soft

Start Phase takes place between 0.8V and 3.1V.

Above V

SoftsS = 3.1V there is no longer duty cycle

limitation DC

max which is controlled by comparator C7

since comparator C2 blocks the gate G7 (see Figure

5).This maximum charge current in the very first stage

when V

SoftS is below 0.8V, is limited to 0.9mA.

Figure 5

Startup Phase

By means of this extra charge stage, there is no delay

in the beginning of the Startup Phase when there is still

no switching. Furthermore Soft Start is finished at 3.1V

to have faster the maximum power capability. The duty

cycles DC

1 and DC2 are depending on the mains and

the primary inductance of the transformer. The

limitation of the primary current by DC

2 is related to

SoftS = 3.1V. But DC1 is related to a maximum primary

current which is limited by the internal Current Limiting

with CS = 1V. Therefore the maximum Startup Phase

is divided into a Soft Start Phase until t1 and a phase

from t1 until t2 where maximum power is provided if

demanded by the FB signal.

Soft-Start

Comparator

Soft Start

SoftS

3.25k



0.8V

SoftS

Gate Driver

0.6V

x3.2

PWM OP

3.1V

Freq Jitter

Charging

current I

Freq Jitter

Discharging

current I

Freq Jitter

Control

max

SoftS

max. Soft Start Phase

0.8V

3.1V

4.0V

max. Startup Phase

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