Infineon ICE2QS03G Application Note

Application note, Version 1.0, 7 April 2010

Application note

ANPS0045 - ICE2QS03G

Converter Design Using Quasi-resonant PWM
Controller ICE2QS03G

Power Management & Supply

Never stop thinking.

Published by
Infineon Technologies AG
81726 Munich, Germany
© 2010 Infineon Technologies AG
All Rights Reserved.

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Title: ICE2QS03G Design Guide

Revision History: 7 April 2010 V1.0

Previous Version: none

Page Subjects (major changes since last revision)

Converter design using the quasi-resonant PWM controller ICE2QS03G
License to Infineon Technologies Asia Pacific Pte Ltd

AN-PS0045

Wang Zan

[e-mail]

He Yi

[e-mail]

Jeoh Meng Kiat

[e-mail]

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Application Note 3 7 April 2010

Converter design using the quasi-resonant

PWM controller ICE2QS03G

AN-PS0045

Table of Contents

1 Introduction .........................................................................................................5

2 IC description ......................................................................................................5

2.1 Main features ....................................................................................................................5

2.2 Pin layout ..........................................................................................................................5

2.3 Pin functions.....................................................................................................................5

2.3.1 ZC (Zero Crossing)........................................................................................................6

2.3.2 FB (Feedback)...............................................................................................................6

2.3.3 CS (Current Sensing) .................................................................................................... 6

2.3.4 Gate (Gate drive output)................................................................................................6

2.3.5 HV (High voltage)..........................................................................................................6

2.3.6 VCC (Power supply)......................................................................................................6

2.3.7 GND (Ground)...............................................................................................................6

3 Overview of quasi-resonant flyback converter ...............................................6

4 Functions and Application Overview ...............................................................8

4.1 VCC Pre-Charging and Typical VCC Voltage During Start-up ......................................8

4.2 Soft-Start...........................................................................................................................9

4.3 Normal Operation .............................................................................................................9

4.3.1 Switch-on Determination ...............................................................................................9

4.3.2 Switch-off Determination .............................................................................................10

4.4 Active Burst Mode Operation ........................................................................................11

4.4.1 Entering Active Burst Mode Operation ........................................................................11

4.4.2 During Burst Mode Operation......................................................................................11

4.4.3 Leaving Active Burst Mode.......................................................................................... 12

4.5 Current sense .................................................................................................................12

4.6 Feedback.........................................................................................................................12

4.7 Zero crossing..................................................................................................................12

4.8 Gate drive........................................................................................................................13

4.9 Others..............................................................................................................................13

5 Typical application circuit................................................................................14

6 References.........................................................................................................14

Application Note 4 7 April 2010

Converter design using the quasi-resonant

PWM controller ICE2QS03G

AN-PS0045

1 Introduction

This application notes describes how to design quasi-resonant flyback converters using ICE2QS03G, which
is a new Quasi-resonant PWM controller developed by Infineon Technologies
In this application note, The basic description of IC will be given first including the main features and Pin’s
layout. Then an overview of quasi-resonant flyback converter will be given, followed by the introduction of
ICE2QS03G’s functions and operations. Some application examples and hints will be given in the last part of
this document.

2 IC description

ICE2QS03G is a second generation quasi-resonant PWM controller optimized for off-line power supply
applications such as LCD TV, and notebook adapter. The digital frequency reduction with decreasing load
enables a quasi-resonant operation till very low load. As a result, the system average efficiency is
significantly improved compared to conventional solutions. The active burst mode operation enables ultra-low
power consumption at standby mode operation and low output voltage ripple. The numerous protection
functions give a full protection of the power supply system in failure situation. All of these make the
ICE2QS03G an outstanding controller for quasi-resonant flyback converter in the market.
In addition, numerous protection functions have been implemented in the IC to protect the system and
customize the IC for the chosen applications. All of these make the ICE2QS03G an outstanding product for
real quasi-resonant flyback converter in the market.

2.1 Main features

• Quasi-resonant operation

• Load dependent digital frequency reduction

• Active burst mode for light load operation

• Built-in high voltage startup cell

• Built-in digital soft-start

• Cycle-by-cycle peak current limitation with built-in leading edge blanking time

• Foldback Point Correction with digitalized sensing and control circuits

• VCC undervoltage and overvoltage protection with Autorestart mode

• Over Load /open loop Protection with Autorestart mode

• Built-in Over temperature protection with Autorestart mode

• Adjustable output overvoltage protection with Latch mode

• Short-winding protection with Latch mode

• Maximum on time limitation

• Maximum switching period limitation

2.2 Pin layout

ZC

FB

CS

1

2

3

GND

8

VCC

7

NC

6

GATE

45

HV

Figure 1 Pin configurations (top view)

2.3 Pin functions

Application Note 5 7 April 2010