UM0422 Datasheet, PDF (1/14 Pages) STMicroelectronics – Constant current controller for high brightness LEDs

UM0422
User manual
Constant current controller for high brightness LEDs
Introduction
The recent improvements in high power light-emitting diode (LED) technology with 100
lumens per LED chip and efficiency higher than that of incandescent lamps bring solid state
lighting close to reality. Light-emitting diodes (LEDs) have become very popular in the area
of general lighting as a replacement technology for low voltage lighting. Customers are
recognizing the advantages of using LED lighting which include long operating life, no fragile
glass, and low voltage DC operated.
LEDs are now available in higher and higher wattages per package (1 W, 3 W and 5 W) with
currents up to 1.5 A. At these current levels, the traditional means of limiting current with a
resistor are not sufficiently accurate nor efficient. It is well known that the brightness of LEDs
is proportional to the forward current. The best way to supply LEDs is to control the forward
current in order to get a good match of the output light. LED manufacturers specify the
characteristics (such as lumens, beam pattern, color) of their devices at a specified forward
current (IF) but they do not specify these characteristics at a specific forward voltage (VF). In
order to better control the LED current under several application conditions,
STMicroelectronics has developed the STCS1, a device which not only guarantees a
constant LED current but also provides useful features that make the device suitable for
different applications such as advertising signs, automotive interior and exterior lighting, and
emergency vehicle warning lights. This document describes how to use the STCS1
evaluation board. It includes a schematic diagram, bill of materials (BOM), and test data.
Table 1. Device summary
Description
STCS1A evaluation board
Order code
STCS1ADEMO1
Figure 1. STCS1A evaluation board
February 2008
Rev 2
1/14
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