IRPLDIM1E datasheet(9/14 Pages) IRF

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IRPLDIM1E Design

Line Input Voltage: 185 to 265VAC/50/60Hz

DC Bus Voltage: 400VDC

Lamp Power/Type: 36W/T8

1) Lamp Requirements

Typical high-frequency (25kHz) lamp require-

ments for the 36W/T8 lamp type are given as:

Table III, 36W/T8 lamp requirements

2) Iterate L and C to Fulfill Constraints

To select the ballast output stage inductor and

capacitor, a range of values were inserted into

equations (2) through (7), which have been sum-

marized in the following table:

Table IV, Ballast parameters for different C values.

When compared against the lamp requirements,

a capacitor value of 6.8nF gives a lamp voltage

during pre-heat that exceeds the maximum al-

lowable specified for this lamp type. This can

ignite the lamp before the cathodes have

reached their emission temperature, drastically

reducing lamp life. The pre-heat current can be

reduced to give a lower pre-heat voltage, but

the pre-heat time must then be increased for

proper heating. Also,

is too low, which

will cause the lamp to extinguish at low light lev-

els where the arc current alone is too low to heat

the cathodes. Increasing the capacitor value to

10nF fulfills the lamp requirements quite well,

even allowing some room in the pre-heat volt-

age for the pre-heat current to be increased and

the pre-heat time shortened. During dimming,

however, the lamp voltage increases with de-

creasing lamp power due to lamp negative in-

cremental impedance effects. A maximum is

reached around 10% brightness, after which the

lamp voltage decreases as the lamp is further

dimmed. The maximum filament current occurs

at the maximum lamp voltage, which for a ca-

pacitor value of 10nF, is too high and will over-

heat the filaments. A capacitor value of 8.2nF

was chosen which fulfills the lamp requirements

without over-heating the cathodes.

min

Cath

[mH]

2.0

[nF]

6.8

8.2

[Vpp]

700

622

546

[kHz]

ign

[kHz]

ign

[App]

1.4

1.6

1.8

max

[kHz]

min

Cath

[Arms]

0.32

0.35

0.38

Variable

Value

Units

0.6

Arms

1.0

max

600

Vpp

ign

1500

Vpp

max

282

Vpp

min

330

Vpp

min

Cath

0.35

Arms

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