Datasheet

( )
2
2
2
2
4
Freq _ Comp
Pout _ LL
2 Lp Vout Vf n Vdc max
Lp
2 Lp Pout _ LL (Vout Vf n Vdc max)
4 tdly
Vdc max (Vout Vf)
Vdc max Vout Vf
=
é ù
· · + + · ·
ê ú
æ ö
h ·
· · · + + ·
ê ú
ç ÷
· + +
ê ú
ç ÷
· +
h · · +
è ø
ê ú
ê ú
ë û
(
)
2
X
B B 4DT
4
+ +
=
2
ax Bx C 0+ + =
2
1 0.5
Pout _ HL 400 H 62.3kHz 0.86 119.1W
2 0.15
æ ö
= m =
ç ÷
è ø
g g g g
2
1 VCS
Pout _ HL Lp Freq _ HL
2 Rsense
æ ö
= h
ç ÷
è ø
g g g g
2
1 0.5
Pout _ LL 400 H 49.6kHz 0.86 94.9W
2 0.15
æ ö
= · m · · · =
ç ÷
è ø
2
1 VCS
Pout _ LL Lp Freq _ LL
2 Rsense
æ ö
= · · · · h
ç ÷
è ø
1
Freq _ HL 62.3kHz
0.5V 1 1
400 H 580ns
0.15 325V (19V 0.7V) 6
= =
é ù
æ ö æ ö
· m · + +
ç ÷ ç ÷
ê ú
W + ·
è ø è ø
ë û
CS
max
1
Freq _ HL
V 1 1
Lp tdly
Rsense Vdc (Vout Vf ) 6
=
é ù
æ ö æ ö
· · + +
ç ÷ ç ÷
ê ú
+ ·
è ø è ø
ë û
1
Freq _ LL 49.6kHz
0.5V 1 1
400 H 580ns
0.15 127V (19V 0.7V) 6
= =
é ù
æ ö æ ö
· m · + +
ç ÷ ç ÷
ê ú
W + ·
è ø è ø
ë û
CS
min
1
Freq _ LL
V 1 1
Lp tdly
Rsense Vdc (Vout Vf) n
=
é ù
æ ö æ ö
· · + +
ç ÷ ç ÷
ê ú
+ ·
è ø è ø
ë û
LM5023
SNVS961D –APRIL 2013–REVISED JANUARY 2014 www.ti.com
• naux = 10.9
• n = ns/np = .167
• tdly = 580 ns
The next step is to calculate the uncompensated output power at the minimum and maximum input line voltage
while in current limit.
Step three is to calculate the peak current at high line so it does not deliver more power than while it is operating
at low line (94.9 W). One thing that complicates the Line Current Limit Feed Forward calculation is that with
Quasi Resonant operation the switching frequency changes with line and load. We have two equations and two
unknowns, the peak primary current and the QR frequency. This requires use of the quadratic equation:
The positive root is:
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