IR21592/IR21593
(
S
)
&
(
PbF
)
www.irf.com 9
External Components Selection Procedure
(Note:
Please refer to
"Typical Connection"
diagram, page 1)
Calculate R
CS
PK
IGN
CS
I
R
6.1
=
R
CS
sets the maximum ignition current
which corresponds to the maximum
ignition voltage across the lamp.
R
CS
I
IGN
V
IGN
Select R
FMIN
Use Graph 1 or Graph 2
The minimum operating frequency must
be lower than f
100%
of f
IGN
(whichever is
lower). R
FMIN
also programs I
MIN
and I
IPH
,
so R
FMIN
must be set first.
R
FMIN
f
MIN
BEGIN
Calculate R
PULL-UP
QCCUV
ONTURN
UPPULL
I
VAC
R
−
−
=
Set R
VAC
and R
VDC
such that the voltage
on pin VDC will exceed 5.1 volts at the
desired line turn-on voltage.
R
VDC
VAC
TURN-ON
Calculate R
VDC
O
N
TUR
N
VA
C
O
N
TUR
N
VD
C
VAC
R
VAC
R
−
−
−
=
1.5
1
1.5
The voltage at pin IPH is the reference
for amplitude current control during
preheat mode. R
IPH
must be set after
R
FMIN
.
R
IPH
I
PH
V
PH
Select & Calculate R
IPH
Use Graph 8 to find I
IPH
,
then calculate R
IPH
:
IP
H
C
S
P
H
IP
H
I
RI
R
PK
⋅
=
Calculate C
CPH
()
PHCPH
teC
76.2 −=
During preheat, an internal 1.3 µA
current source at pin CPH charges
external capacitor CCPH. Preheat
mode ends when VCPH exceeds 5.1
volts.
C
CPH
t
PH
Calculate ϕ
MIN
(Equations 8 & 9)
R
MIN
sets the lower phase boundary
corresponding to minimum lamp
power when V
DIM
= 0 volts. R
MIN
must
be set after R
FMIN
.
R
MIN
ϕ
MIN
P
LAMP
Calculate R
MAX
Use Equation 15
R
MAX
ϕ
MAX
P
LAMP
R
MAX
sets the upper phase boundary
corresponding to maximum lamp power
when V
DIM
= 5 volts. R
MAX
must be set
after R
FMIN
and R
MIN
.
Find V
MIN
(Graph 9)
Find I
MIN
(Graph 3)
MIN
MIN
MIN
I
V
R =
Calculate R
MIN
