Electronic Circuit Theory - Dell E1709W Service Manual

Electronic Circuit Theory

2.1 Inverter PWM circuit
2.1.1) Inverter Control circuit :( fig.2)
DIM
3 DIM
PID_Input
R15
10K
C11/Open
C2
0.1uF/25V
1nF
R28
+5V
5K/Open
R4
10K
C10
R5
47K 2.2uF/10V
R3 10K
3 ON/OFF
DC_5V through R1 and C1 will provide power for U1 on the pin2 (VDDA).
EN-ON/OFF voltage signal coming from scalar which is on IF BD will enable U1 to work. This
applies a level greater than approximately 2V to pin8 (ENA) enables the IC, A voltage less than 1V
will disable the IC. R3 is used to limit current.C3 and R16 is used to dump noise.
The soft-start function is provided by connecting C8 to pin12(SSTCMP), In the start-up mode,
current charges C8, its voltage controls the gradual increase in power to the transformer and
subsequently to the output load, this reduces in-rush current and provides reliable operation to the
CCFL.If no current is sensed approximately 2 seconds, U1 shuts off. Once the voltage at the pin4
(ISEN) reaches the lamp on threshold, the IC switches from the striking mode to the normal
operation mode and the PWM dimming control is activated.
DIM-ADJ duty cycle signal through R2 and C2 is on Pin 3(DIM), which adjusted will can
change the brightness of Panel. R15 is used to limit current. Internal LPWM dimming control is
determined by R11 and C7 connected to LCT (pin11), analog dimming is implemented by providing
+5V
R1
10R
C1
2.2uF/10V
R13
1M C13
10nF/25V
U1
R2
1
DRV1 DRV2
100K
2
VDDA GNDA
3
DIM TIMER
4
ISEN
5
PID SSTCMP
6
RSTR
7
RT OVPT
R6 R7
100K 330k 8
ENA VSEN
INL837
R16 C3
100K 10nF/25V X7R
R26 0R
R10 C6
200k/Open
33nF
1N4148
D9/Open
R9
100K
R11 R12
3.3M 91K 1%
OLP1
OLP2
D10
1N4148
16
15
14
C5
2.2uF/16V
13
CT
12
11
LCT
R8
10 C7 C8
820K
10nF
9 47nF/16V
R24
4.7K
R14 C14
1M 10nF/25V X7R
R17 10K/Open
2
3
1
ZD5/Open BAW56
R18 0R
Fig.2
6
T1A
U2
C23
1 8
S1 D1
1nF/50V
2 7
G1 D1
3 6
S2 D2
C22
4 5
1nF/50V
G2 D2
P6006HVG
T1B
C9
270pF/16V NPO
ZD3
1
3
2
C35A
BAV70
C26 R20
2700p 100K
ZD4/Open
1
3
2
C36A
BAV70 C27
C28 R23 120p/Open
120p/Open 30K/Open
ISEN2
ISEN1
C16 C18
27nF/Open 27nF/Open
Service Manual
+12V
C24
R29
33R
0.1uF/50V
R30
33R
C33A
C25 R21
2700p 100K
C34A
R22
30K/Open