AN4205 Datasheet, PDF (1/23 Pages) STMicroelectronics – The most recent developments in energy savings fit perfectly

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.
April 2013
Doc ID 023929 Rev 1
1/23
www.st.com