Техническая Спецификация для Texas Instruments LM3448 -120VAC, 6W Isolated Flyback LED Driver Eval Board LM3448-120VFLBK/NOPB LM3448-120VFLBK/NOPB
Модели
LM3448-120VFLBK/NOPB
Design Guide
The maximum SW FET drain-to-source voltage is then calculated based on the maximum reflected
voltage V
voltage V
REFL
, ringing on the SW FET drain and the maximum peak input voltage V
IN-PK(MAX)
,
(11)
where,
(12)
and the following condition must be met,
(13)
Peak and RMS SW FET currents are calculated along with maximum SW FET power dissipation based on
the SW FET R
the SW FET R
DS-ON
value,
(14)
(15)
(16)
Current Limit
The peak current limit I
LIM
should be at least 25% higher than the maximum peak input current,
(17)
The parallel sense resistor combination will need to dissipate the maximum power,
(18)
Re-circulating Diode
The main re-circulating diode (D4) should be sized to block the maximum reverse voltage V
RD4(MAX)
,
operate at the maximum average current I
D4(MAX)
, and dissipate the maximum power P
D4(MAX)
as determined
by the following equations,
(19)
(20)
(21)
13.2 Transformer
Primary Inductance
The maximum peak input current i
IN-PK(MAX)
occurring at the minimum AC voltage peak V
IN-PK(MIN)
determines
the worst case scenario that the converter must be designed for in order to stay in DCM. Using the
equation for inductor voltage,
equation for inductor voltage,
(22)
18
AN-2090 LM3448 -120VAC, 6W Isolated Flyback LED Driver
SNOA554C – October 2011 – Revised May 2013
Copyright © 2011–2013, Texas Instruments Incorporated