Datasheet

Boost Inductor
2
RIPPLE
L _ PEAK (max) IN _ PEAK (max)
I
I I= +
(28)
1 28
6 39 7 03
2
L _ PEAK (max)
. A
I . A . A= + =
(29)
1
OUT
BST (min)
SW ( typ ) RIPPLE
V D( D )
L
f I
-
³
(30)
390 0 5 1 0 5
1 17
65 1 28
BST (min)
V . ( . )
L . mH
kHz . A
´ -
³ ³
´
(31)
OUT IN _ RECTIFIED(min)
(max)
OUT
V V
DUTY
V
-
=
(32)
2 85 120
IN _ RECTIFIED(min)
V V V= ´ =
(33)
390 120
0 692
390
(max)
V V
DUTY .
V
-
= =
(34)
Boost Diode
125
0 5
DIODE F _ C OUT(max) SW ( typ ) OUT RR
P V I . f V Q= +
(35)
125
1 5
F _ C
V . V=
(36)
0
RR
Q nC=
(37)
1 5 0 897 0 5 65 390 0 1 35
DIODE
P . V . A . kHz V nC . W= ´ + ´ ´ ´ =
(38)
UCC28019A
www.ti.com .................................................................................................................................................. SLUS828B – DECEMBER 2008 – REVISED APRIL 2009
The boost inductor, L
BST
, is selected after determining the maximum inductor peak current, I
L_PEAK(max)
:
The minimum value of the boost inductor is calculated based upon a worst case duty cycle of 0.5:
The actual value of the boost inductor that will be used is 1.25 mH.
The maximum duty cycle, DUTY
(max)
, can be calculated and will occur at the minimum input voltage:
The diode losses are estimated based upon the forward voltage drop, V
F
, at 125 ° C and the reverse recovery
charge, Q
RR
, of the diode. This design uses a silicon-carbide diode. Although somewhat more expensive, it
essentially eliminates the reverse recovery losses because Q
RR
is equal to 0nC.
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