EFS2A 데이터 시트보기 (PDF) - STMicroelectronics

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EFS2A

STARLIGHT-KIT

STMicroelectronics 

EFS

EFS STARLIGHT-KIT APPLICATION NOTE

1/ THE AC POWER SWITCH: FUNCTIONAL DESCRIPTION

he Starter is a bi-directional switch which performs two functions:

n the preheat of the tube,

n the ignition of the tube.

1

BALLAST

FLUORESCENT

TUBE

220V / 50HZ

PREHEAT

2

V strike

3

The mains voltage is applied

Preheating of the tube

During the preheat period, the ASD™ is fully

conducting. The tube lamp is short circuited by the

starter, and the current flows through its filaments.

In these conditions, the lamp can not light up, but

the temperature of the lamp electrodes increases.

At the end of the preheat period, lamp filaments

are warm enough to emit electrons in the gas and

to permit the lamp ignition in good conditions. The

ASD™ switches off the preheating current . At this

moment, the ballast is equivalent to a current

generator (I=ISO, ISO = Switched Off current). As

the ASD™ switches off, the starter voltage

increases. The amplitude of this high voltage spike

is then clamped by the ASD™ (VBR′1350 V). As

the starter and the lamp are in parallel, the striking

pulse is directly applied to the lamp. The

electromagnetic energy of the ballast is then

discharged through the lamp and the ASD™.

Striking pulse

2/ WHAT’S NEW IN THIS SWITCH?

The AC SWITCH merges an auxiliary power

supply for the driver, a power clamping device

(1350V) and a bi-directional switch with his

execution pilot block.

NEW EFS ASD

G1

ON / OFF

G2

DRIVER

Striking of the tube

TUBE

Vcc

Power supply

GND

6/14

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