ICE3AS02_05 Datasheet, PDF(15/22 Page) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 500V Startup Cell

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ICE3AS02_05 Datasheet, PDF (15/22 Pages) Infineon Technologies AG – Off-Line SMPS Current Mode Controller with integrated 500V Startup Cell

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ICE3AS02 / ICE3AS02G / ICE3BS02 / ICE3BS02G

Functional Description

Once the Auto Restart Mode is entered, the internal Voltage

Reference is switched off in order to reduce the current

consumption of the IC as much as possible. In this mode, the

average current consumption is only 300ÂµA as the only

working block is the Undervoltage Lockout(UVLO) which

controls the Startup Cell by switching on/off at VVCCon/

VVCCoff.

As there is no longer a self supply by the auxiliary winding,

VCC starts to drop. The UVLO switches on the integrated

Startup Cell when VCC falls below 8.5V. It will continue to

charge VCC up to 15V whereby it is switched off again and

the IC enters into the Start Up Phase.

As long as all fault conditions have been removed, the IC

will automatically power up as usual with switching cycle at

the GATE output after Soft Start duration. Thus the name

Auto Restart Mode.

Other fault detections which are active in normal operation

is the sensing for Overload, Open Loop and VCC

undervoltage conditions. In the first 2 cases, FB will rise

above 4.8V which will be observed by C4. At this time, S1

is released such that VSoftS can rise from its earlier clamp

voltage of 4.4V. If VSoftS exceeds 5.4V which is observed by

C3, Auto Restart Mode is entered as both inputs of the gate

G5 are high.

This charging of the Soft Start capacitor from 4.4V to 5.4V

defines a blanking window which prevents the system from

entering into Auto Restart Mode un-intentionally during

large load jumps. In this event, FB will rise close to 6.5V for

a short duration before the loop regulates with FB less than

4.8V. This is the same blanking time window as for the

Active Burst Mode and can therefore be adjusted by the

external CSoftS.

In the case of VCC undervoltage, ie. VCC falls below 8.5V,

the IC will be turn off with the Startup Cell charging VCC as

described earlier in this section. Once VCC is charged above

15V, the IC will start a new startup cycle. The same

procedure applies when the system is under Short

Optocoupler fault condition, as it will lead to VCC

undervoltage.

Version 1.2

02 Sep 2005

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