Datasheet

LED7707 Application information
37/47
In order to estimate also the efficiency, other contributions to the power dissipation must be
added to P
D, tot
(which represents only the power dissipated by the device), that is:
Equation 47
where V
F, Diode
= 0.4 V
Equation 48
where DCR = 80 mΩ (typical DCR of the recommended inductors).
Therefore the total dissipated power is:
Equation 49
Considering the input power as the result of input voltage multiplied by the input current, the
estimated efficiency is:
Equation 50
Note: It is important to remind that the previous calculations consider the worst case, especially for
the power dissipated on the current generators.
Statistical analysis (confirmed by bench measurements) shows that the series connection of
more LEDs on each channel leads to compensation effects.
The hypothesis 3 above mentioned is thus rather unlikely.
Therefore P
GEN
is significantly lower and the overall efficiency is typically around 90 %.
mW133DIVP
2INDiode,FDiode,DISS
=
⋅
⋅
=
mW63IDCRIDCRP
2
IN
2
RMS,IndInd,DISS
=⋅≅⋅=
W316.1PPPP
Ind,DISSDiode,DISStot,DTOTAL,DISS
=
+
+
=
862.0
P
PP
IN
TOT,DISSIN
=
−
=η