IRPLDIM1U Ver la hoja de datos (PDF) - International Rectifier
Número de pieza
componentes Descripción
Lista de partido
IRPLDIM1U Datasheet PDF : 12 Pages
| |||
2) Iterate L and C to Fulfill Constraints
To select the ballast output stage inductor and
capacitor, a range of values were input into
equations (2) through (7), which have been sum-
marized in the following table:
L
[mH]
2.0
C
[nF]
6.8
V ph
748
[Vpp]
f ph
[kHz]
53
f ign
49
[kHz]
I ign
1.4
[App]
f pmax [kHz]
49
I Cath Pmin [Arms]
0.32
2.0
2.0
8.2
10
668
592
49
46
45
40
1.5
1.7
46
43
0.35
0.38
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
pwrioll pcearuhseeathtiengla. mAplstoo,eIxCtainthgmuinisihs
too low, which
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
voltage for the pre-heat current to be increased
and the pre-heat time shortened. During dim-
ming, however, the lamp voltage increases with
decreasing lamp power due to lamp negative
incremental 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-
www.irf.com
heat the filaments. A capacitor value of 8.2nF
was chosen which fulfills the lamp requirements
without over-heating the cathodes.
3) IR21592 Programmable Inputs
With all of the lamp requirements fulfilled, the
component values for setting the programmable
inputs of the IR21592 are calculated as:
Equation No.
(8)
(8)
(9)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
Variable
f 100%
f 1%
ϕ 100%
ϕ 1%
RFMIN
RCS
R IPH
C TPH
RMIN
R MAX
Value
46kHz
58kHz
-56.12deg
-89.27deg
36kOhm
1.0 Ohm
22kOhm
330nF
27kOhm
24kOhm
Table V, IR21592 Programmable Inputs for T8/32W lamp.
Important Note: These design kits are intended
as a demonstration of the functionality and per-
formance of the IR21592 Dimming Ballast Con-
trol IC only. Adequate EMI filtering, line tran-
sient protection, galvanic dim control input iso-
lation, and ballast and lamp life testing are not
considered in this design.
9
Share Link: 