Datasheet

Application notes - buck conversion LED5000
28/51 Doc ID 023951 Rev 1
higher than this value to compensate for the losses in the overall application. For this
reason, the conduction losses related to the R
DSON
increase compared to an ideal case.
● Switching losses due to turning ON and OFF. These are derived using the following
equation:
Equation 38
Where T
RISE
and T
FALL
represent the switching times of the power element that cause the
switching losses when driving an inductive load (see
Figure 18 ). T
SW
is the equivalent
switching time.
Figure 18. Switching losses
● Quiescent current losses.
Equation 39
Example (see
Chapter 5.6 ):
V
IN
=42 V, V
FW_LED
=3.7 V, n
LED
=8, I
LED
=1500 mA
The typical output voltage is:
Equation 40
R
DSON_HS
has a typical value of 200 Ω at 25 °C.
P
SW
V
IN
I
OUT
T
RISE
T
FALL
+()
2
-----------------------------------------
F
SW
V
IN
= I
OUT
T
SW_EQ
F
SW
⋅⋅ ⋅ ⋅⋅ ⋅=
AM13502v1
P
Q
V
IN
I
Q
⋅=
V
OUT
n
LED
V
FW_LED
V
FB
+⋅ 29.4V==