1/17

AN1842

APPLICATION NOTE

January 2004

Introduction

The LCD monitors and TVs are growing very fast, so to support this kind of applications, a dedicated ref-

erence design has been developed, taking into account all the requirements that are needed.

The proposed reference design can supply an LCD monitor or an LCD-TV as well, up to 22" panels, to-

gether with multimedia functions like audio. The SMPS accepts a full range input voltage and delivers 2

output voltages, a 5V dedicated to the scaler and

µP, and a 12V dedicated to the backlight and audio. The

required standby power consumption is 0.8W at 230Vac, in order to satisfy the worldwide power saving

rules. The circuit is also fully protected against faults like output short circuit or over voltage. The market

cost pressure has requested a design approach with particular attention to the solution cost. The board

technology used is the standard thru-hole, but it can be changed very easily in SMT because most of com-

ponents are available also in this technology. The circuit has been tested deeply in all the most salient

aspects with positive results and it has been integrated with a 22" LCD-TV application without showing

any problem.

Main characteristics

INPUT VOLTAGE:

90 ÷ 265 Vrms - 45-66 Hz

OUTPUT VOLTAGES:

5.1V

±2% - @2A Dedicated to panel and digital circuitry for scaling

12V

±10% - @4A Dedicated to backlight lamp inverters, audio and SCART

STANDBY

Input power less than 0.8W @230Vac, delivering 30mA on 5.1V

FAULT PROTECTIONS:

Short circuit on each output with auto-restart at short removal, Open loop

Safety&EMC:

Safety: Acc. to EN60950, creepage and clearance minimum distance 6.4mm

EMC: According to EN50022 Class-B

PCB TYPE & SIZE:

Cu Single Side 70

µm, CEM-1, 180 x 89 mm

by Claudio Spini

60W WIDE-RANGE POWER SUPPLY

FOR LCD MONITOR OR TV, USING THE L5991

This document describes a reference design for a 60W Switch Mode Power Supply dedicated to LCD

TV sets or monitors. The board accepts full range input voltage (90 to 265Vrms) and delivers 5V and

12V. It has good efficiency and very good standby performance, able to meet the most stringent

standby rules.