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AN1523

APPLICATION NOTE

March 2002

Introduction

Low power SMPS are today very popular in consumer applications for example like low-cost cable, terrestrial

decoders or high end TV chassis and the manufacturers need to design circuits with good performance, small

size with high cost effectiveness. An integrated monolithic solution controlling the SMPS like the L6590 makes

it a very suitable device, able to satisfy all the requirements of a compact and flexible solution, integrating all the

necessary functions to obtain a robust design just adding few external components. In this proposed reference

design, the board is thru-hole technology, without any heat sink. A specific application circuit fully tested is pro-

posed and the test results, including thermal and EMI, are enclosed in this document. The transformer data are

included too, making it a good way to achieve a very short time to market solution.

SMPS Main characteristics

q

INPUT AND OUTPUT VOLTAGES:

q

STAND BY:

During the stand-by operation the power consumption from the mains has to be

≤1W, when the circuit

delivers 50mA from the 5V output and the 12V is unloaded.

q

PROTECTIONS:

Overload ad short circuit on both outputs, with auto-restart at short removal. An OVP circuit for open-

loop protection.

q

SAFETY:

In acc. with EN60065, creepage and clearance minimum distance is 4.8mm

q

EMI:

In acc. with EN50022 Class B

INPUT VOLTAGE:

OUTPUT VOLTAGES AT FULL LOAD:

Vout

Iout

Pout

STABILITY

Vin:

90

÷ 264 Vrms

[V]

[A]

[W]

f:

45

÷ 66 Hz

5

1.4

7.5

±2%

12

0.3

3.6

±5%

by Claudio Spini

11W FLYBACK CONVERTER FOR

AUXILIARY POWER

SUPPLY APPLICATION USING THE L6590

This document describes an 11W Switch Mode Power Supply reference design, dedicated to Consumer

Applications, e.g. TV chassis auxiliary power supply, low cost Set-top box or digital equipment. The

board accepts full range input voltage (90 to 265Vrms) and delivers 2 output voltages. It is based on the

monolithic controller L6590, integrating the controller and a POWERMOS and working at fixed frequen-

cy, PWM mode and including a stand-by function to minimize the power consumption during light load

operation. It incorporates also all the protections, offering a complete and very compact solution for low

power SMPS.