Datasheet

Input Capacitor
RIPPLE RIPPLE IN _ PEAK(max)
I I I= D
(18)
0 2
RIPPLE
I .D =
(19)
0 2 6 39 1 28
RIPPLE
I . . A . A= ´ =
(20)
IN _ RIPPLE(max) RIPPLE _ IN IN _ RECTIFIED(min)
V V V= D
(21)
0 06
RIPPLE _ IN
V .D =
(22)
2
IN _ RECTIFIED IN
V V=
(23)
2 85 120 2
IN _ RECTIFIED (min)
V V . V= ´ =
(24)
0 06 120 2 7 21
IN _ RIPPLE(max)
V . . V . V= ´ =
(25)
8
RIPPLE
IN
SW IN _ RIPPLE(max)
I
C
f V
=
(26)
1 28
0 341
8 65 7 21
IN
. A
C . F
kHz . V
m= =
´ ´
(27)
UCC28019A
SLUS828B – DECEMBER 2008 – REVISED APRIL 2009 .................................................................................................................................................. www.ti.com
Note that the UCC28019A is a continuous conduction mode controller and as such the inductor ripple current
should be sized accordingly. High inductor ripple current has an impact on the CCM/DCM boundary and results
in higher light-load THD, and also affects the choices for R
SENSE
and C
ICOMP
values. Allowing an inductor ripple
current, I
RIPPLE
, of 20% and a high frequency ripple voltage factor, Δ V
RIPPLE_IN
, of 6%, the minimum input
capacitor value, C
IN
, is calculated by first determining the input ripple current, I
RIPPLE
, and the input ripple voltage,
V
IN_RIPPLE(max)
:
The value for the input x-capacitor can now be calculated:
A 0.33 µ F, 275 VAC X2 film capacitor was selected for C
IN
.
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Product Folder Link(s): UCC28019A