Microchip HV809 Handleiding

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Supertex inc.

Supertex inc.

www.supertex.com

Doc.# DSAN-AN-H36

A040313

AN-H36

Application Note

HV809 EL Lamp Driver for Battery Powered

and Off-line Equipment

by Scott Lynch, Senior Applications Engineer

Introduction

The Supertex HV809 is designed to drive large lamps at

high brightness. It can operate from a rectied/ltered 120V

AC power line or from any DC source in the range of 50 to

200V. For use in battery powered applications, an external

DC-DC converter is required.

This application note is divided into two sections, portable

applications and off-line applications. Section I describes the

operation of the Supertex’s HV809 EL lamp driver for a battery

operated (4 AA cells) application to drive a 12.5in2EL lamp

to a brightness of 15ft-lm. Details are provided for designing

a high voltage output DC-DC converter. Applications can be

for PDA’s, GPS’s, hand held computers, and other portable

devices requiring high brightness EL backlighting. Section II

describes the HV809 operating from a 120V AC line to drive

a 100in2 EL lamp to a brightness of 20ft-lm. Applications can

be signage, courtesy lighting, and accent lighting.

Section I - Portable Applications

The basic circuit conguration is shown in Figure 1. There

are many different implementations in designing the DC-DC

converter. In this design, an inexpensive 555 timer IC was

used for the DC-DC converter. Details of the converter are

discussed in a later section.

Lamp Driver Circuit and Operation

The Supertex HV809 is capable of driving EL lamps of up to

350nF at 400Hz. Input supply can be any DC voltage source

from 50 to 200V. The HV809 supplies the EL lamp with an

AC square wave with a peak-to-peak voltage of two times

the input DC voltage.

The HV809 incorporates a lamp drive oscillator with frequency

controlled by a single resistor, REL-osc. The oscillator controls

the lamp driver output section, which consists of 4 transistors

arranged in a full bridge conguration as shown in Figure 2.

Figure 2: HV809 Lamp Driver

Figure 1: HV809 for Portable Applications

A1

A2

GND

REL

HVIN

VDD

OSC2

OSC1

HV809

DC-DC

Converter

CDD

REL

EL

Lamp

Batteries

HVOUT

VIN

Linear

Regulator

GND

HVIN

VDD

OSC2

OSC1

REL-Osc

Q

Q

Q

VA

Q

Logic

and

Osc

VB

Product specificaties