IXDN0037 datasheet(5/31 Pages) IXYS

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Ballast Demonstrator User Guide

7629A–AVR–04/06

Since the argon conductivity increases and resistance across the lamp ends decreases

as the gas becomes excited, an inductance (ballast) must be used to limit and control

the gas current. In the past, an inductor could be designed to limit the current for a nar-

row range of mains voltage and frequency. A better method to control gas current is to

vary an inductor's volt-seconds to achieve the desired lamp current and intensity. A vari-

able frequency inverter operating from a DC bus can do this. If the inductor is part of an

R-L-C circuit, rapid start ignition and operating currents are easily controlled depending

on the driving frequency versus resonant frequency.

Utility is enhanced by designing a power factor correcting boost converter (PFC) to

achieve the inverter DC bus over a wide mains voltage range of 90 - 265VAC, 50/60 Hz.

Since a PFC circuit keeps the mains current and voltage in phase with very low distor-

tion, mains power integrity is maintained. Additional utility is achieved by designing a

microcontroller for the electronic ballast application that can precisely and efficiently

control power levels in the fluorescent lamp. An application specific microcontroller

offers the designer unlimited opportunity to enhance marketability of lighting products.

The final design topology is shown in the block diagram of Figure 1-3.

1.1

General

Description

Fluorescent ballast topology usually includes line conditioning for CE compliance, a

power factor correction block including a boost converter to 380 V for universal input

applications and a half bridge inverter. Varying the frequency of the inverter permits time

for filament preheat and ignition for rapid starting, including precise power control. As

shown in the block diagram, figure 3, all of these functions can be timed, regulated, and

diagnosed with the Atmel AT89EB5114 microcontroller.

1.2

Ballast

Demonstrator

Features

• Automatic microcontroller non-dimmable ballast

• Universal input _ 90 to 265 VAC 50/60 Hz, 90 to 370 VDC

• Power Factor Corrected (PFC) boost regulator

• Power feedback for stable operation over line voltage range

• Variable frequency half bridge inverter

• 18W, up to 2 type T8 lamps

• Automatic single lamp operation

IXDN0037 Datasheet(PDF) 5 Page - IXYS Corporation