Zxld1370, Application information – Diodes ZXLD1370 User Manual
Page 26
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ZXLD1370
Document number: DS32165 Rev. 5 - 2
26 of 39
September 2012
© Diodes Incorporated
ZXLD1370
A Product Line of
Diodes Incorporated
Application Information
(cont.)
Input Capacitor
The input capacitor can be calculated knowing the input voltage ripple
ΔV
IN-PP
as follows:
Buck
PP
IN
SW
LED
IN
V
x
f
I
x
)
D
1
(
x
D
C
−
Δ
−
=
Use D = 0.5 as worst case
Boost
PP
IN
SW
PP
L
IN
V
x
f
x
8
I
C
−
−
Δ
Δ
=
Buck-Boost
PP
IN
SW
LED
IN
V
x
f
I
x
D
C
−
Δ
=
Use D = D
MAX
as worst case
The minimum RMS current for the output capacitor is calculated as follows:
Buck
)
D
1
(
Dx
x
I
I
LED
RMS
CIN
−
=
−
use D = 0.5 as worst case
Boost
12
I
I
PP
L
RMS
CIN
−
−
=
Buck-Boost
)
D
1
(
D
x
I
I
LED
RMS
CIN
−
=
−
Use D = D
MAX
as worst case
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