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T h e l o a d i n g o f l a m p b e f o r e l i g h t i n g u p = œ , t h e l o a d i n g a f t e r l i g h t i n g
up=
Befo re l i g h t i n g u p : Vout=Vo p e n , Vc=0
A f t e r l i g h t i n g u p : Vout=lamp vo l t age
Vc=Vopen-Vo u t
lTh e o u t p u t c u rr ent wa s d e c i d e by Co capacitor and CCFL equivalent impedance.
(6) Feedback loop:
Fo r s e n s o r o u t p u t c u rr e n t , we change t h e a c vo l t age t o d c vo l t age a n d c o n n e c t o r t o e rr o r a m p l i fi e r o f c o n t ro l I C , t o
s t a b l e t h e o u t p u t c u r r e n t .
REF
2.50V
1
HCLMP
Vset
2
LCLMP
3
SCP
4
ADJ
5
+
EA
-
FB
6
CMP
7
R4
70k
2.5V
R5
630k
GND
8
Note:
OVP – Over Voltage Protection
SCP – Short-Circuit Protection
UVL – Under Voltage Lockout
Circuit Description
IBIAS
POFF
&
REFERENCE
+
Vmax
Vmax=2.6V-Vset
V>Vmax -- -> Vmax
-
V
Vmin<V<Vmax ->V
V<Vmin -- ->Vmin
Vmin
(fix value)
SS1
t1
(slow start)
+
OLPROT
COMP
-
Functional Block Diagram
+
RAMP
COMP.
-
Vdd
RESET
UNDER VOLTAGE
UVLO
LOCKOUT
ZVS
CONTROLLER
PROTECTION
SS2
t1+t2
(slow start)
V_SS2
NEC-FA150ATUA
Vdd
16
RT
15
+
2.5V
COMP
-
PULSE GEN
CT
+
COMP
14
0.5V
-
0.6V
+
LAMP
COMP
OPS
ON/OFF
-
13
ENA
+
12
ENABLE
COMP
R1
300k
-
ACTIVE
"HIGH"
1.5V
PDR
11
PDRV
Pgate
NDR
Ngate
NDRV
10
I=12uA
I=2.5uA
SS1
SST
9
R2
4K
MN1
POFF
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