April 2013

Doc ID 023929 Rev 1

1/23

AN4205

Application note

AC/DC converter to drive LEDs with mixed linear and switching

regulation

By Vittorio Giuffrida

Introduction

The most recent developments in energy savings fit perfectly with LED lighting as LEDs

have an almost unlimited operating life and a smaller size as well as better efficiency when

compared to their incandescent counterparts. Nowadays these advantages make the use of

LED lighting very attractive, but the higher cost is delaying widespread introduction in the

lighting market.

In this context an LED lighting driver has been designed in order to offer a cheap board in

the consumer market. The AC/DC converter for LED lighting acts on linear regulation to

control the LED current and on the switching regulation to minimize the power losses. In

particular this application note presents the design guidelines of a 7 W LED driver. The

solution lies in the output stage that implements a simple circuit able to keep the LED

current constant and at same time to keep down the power losses in the Power MOSFET

that works in the linear zone.

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