AN3040 Datasheet, PDF (1/27 Pages) STMicroelectronics – This application note describes a demonstration board able to drive

AN3040
Application note
STEVAL-ILB008V1 4 x 18 W/T8 ballast driven by L6585DE
Introduction
This application note describes a demonstration board able to drive a 4 x 18 W linear T8
fluorescent tubes.
The ballast is controlled by the new L6585DE IC that integrates the PFC and half-bridge
control circuits, relevant drivers, and the circuitry that manages all the operating phases
(preheating, ignition and run mode) of the lamp. Protections against failures such as lamp
disconnection, anti-capacitive mode and PFC overvoltage are guaranteed and obtained with
a minimum number of external components. In addition to the description of the circuit and
design criteria, this document provides a short overview of the ballast performances.
Fluorescent lamps are driven more and more by electronic ballasts rather than by
electromagnetic ballasts, primarily because fluorescent lamps can produce around 20%
more light for the same input power when driven above 20 kHz instead of 50/60 Hz.
Operation at this frequency also eliminates both light flickering (the response time of the
discharge is too slow for the lamp to have a chance to extinguish during each cycle) and
audible noise. Electronic ballasts consume less power and therefore dissipate less heat
than electromagnetic ballasts. The energy saved can be estimated in the range of 20-25%
for a given lamp power. Finally, the electronic solution allows better control of the filament
current and lamp voltage during preheating with the unquestionable benefit of increasing the
average lamp life.
Figure 1. 4 x 18 W T8 ballast demonstration board
June 2010
Doc ID 16181 Rev 2
!-V
1/27
www.st.com