DL2482 datasheet(58/82 Pages) OSRAM

58 / 82 page

Economical long-life light sources with plug-in bases.

Compact Fluorescent Lamps OSRAM DULUX®

Technical Guide

5.1.4 Dimming

Reducing the lamp current below the minimum value specified in 5.1.3 can be used

to reduce the luminous flux of the lamp appreciably below its rated value, thereby

dimming the lamp. Please note the following:

The lamp electrodes must be maintained at emission temperature by a continous

heating current.

The lamp voltage at lower discharge current is generally higher than the rated

value.

The chromaticity coordinate of the light colour may deviate from its specified

value.

In the interest of maximising lamp life, the auxiliary heating current must be matched

to the lamp current. If the auxiliary heating current is too low, the lamp electrodes will

very quickly be destroyed by sputtering. A constant heating current that is too high

will result in excessive emitter evaporisation which leads to end blackening.

Generally speaking, it is not easy to measure the continuous heating current when the

lamp is being operated on an electronic control gear because the current is fed to the

electrodes in the lamp via the two lead wires in a split that depends on the design of

the control gear, and because the lamp current and the auxiliary heating current may

differ in phase, curve shape and frequency. Therefore it is not reasonable to specify

the necessary auxiliary heating current as a function of the lamp current.

The important variable for electrode heating is the electrical heating power Pheat fed

to the electrode. As

PHeat = PLamp current + PHeating current = f (I

d , I

Heat)

≈ f (I2d + I2Heat)

PHeat

≈ f (I2Pin 1 + I2Pin 2)

the necessary auxiliary heating current can also be specified as a function of lamp

current by indicating the total of I

Pin 1 + I

Pin 2, where IPin 1 and IPin 2 are the two pin

currents at an electrode in the lamp. IPin 1 and IPin 2 can be easily measured on elec-

tronic control gear.

As the diagram above shows, there is an ideal target setting for the sum of the squa-

res of the two pin currents at which the lamp life will be at it’s optimum. If the sum of

the squares of the pin currents decreases, sputtering will occur at the electrodes and

5. Data for control gear manufacturers

Life

Target

End

blackening

pin 1

pin 2

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