ICE2A0265 View Datasheet(PDF) - Infineon Technologies

Part Name

Description

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ICE2A0265

Off-Line SMPS Current Mode Controller with integrated 650V/800V CoolMOS™

Infineon Technologies 

CoolSET™-F2

6.5V

R FB

Soft-Start Com parator

FB

PW M -Latch

O p to co u p le r

PW M Com parator

0.8V

PWM OP

Isense

x3.65

Im proved

Current Mode

Figure 11 PWM Controlling

3.3

Soft-Start

V SoftS

5.6V

5.3V

T Soft-Start

G ate Driver

t

Functional Description

pull-up resistor RSoft-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 VSoftS is less than

Feedback voltage VFB the Soft-Start-Comparator limits

the pulse width by resetting the PWM-Latch (see

Figure 12). In addition to Start-Up, Soft-Start is also

activated at each restart attempt during Auto Restart.

By means of the above mentioned CSoft-Start the Soft-

Start can be defined by the user. The Soft-Start is

finished when VSoftS 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 has a clamp voltage of 5.6V to

prevent the internal circuit from saturation (see Figure

13).

5.6V

SoftS

6.5V

Power-Up Reset

R Soft-Start

E rro r-L a tc h

RQ

6.5V

C4

5.3V

G2

SQ

4.8V

R FB

FB

RQ

C3

G a te

C lo c k

D river

SQ

PW M -Latch

Figure 13 Activation of Protection Unit

The Start-Up time TStart-Up within the converter output

voltage VOUT is settled must be shorter than the Soft-

Start Phase TSoft-Start (see Figure 14).

CSoft – Start = -R---S--o--Tf-t--–S---So--tf-at--r-–t---S×--t-a--1-r-t--.-6---9-

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 12 Soft-Start Phase

The Soft-Start is realized by the internal pull-up resistor

RSoft-Start and the external Capacitor CSoft-Start (see

Figure 5). The Soft-Start voltage VSoftS is generated by

charging the external capacitor CSoft-Start by the internal

Version 2.0

12

11 Jun 2004

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