an8041s Panasonic Corporation of North America, an8041s Datasheet - Page 10

• Manufacturer Part Number: an8041s
• Description: Liquid Crystal Backlight Control Ic
• Manufacturer: Panasonic Corporation of North America

AN8041S
10
[3] Function descriptions (continued)
3. Error amplifier 1 block and error amplifier 2 block (continued)
Application Notes (continued)
Error amplifier 1
V
1) Power-on mode
2) Normal control mode
3) Light-regulation operation mode
output voltage
OUT
R1
R2
converter
detection
The control modes of backlight are described below:
starts the control.
voltage of several kV is generated in the lamp through the DC-AC inverter, and the backlight is lighted up.
During this period, since the lamp current does not flow in the error amplifier 2 block, the error amplifier output
(FB2) becomes high-level, so that its control does not work.
and volume control V
amplifier 2 block. The output voltage of the DC-DC converter V
voltage, and the lamp voltage is maintained at several hundred volts.
regulated by the input voltage of the inverter. By adding volume V
amplifier 2 block to make the detection voltage V
as to make the lamp current variable for light regulation.
regulation possible.
Usage notes
DC-DC converter, one of two error
amplifiers is not used. Connection
should be made so that the FB termi-
nal is fixed to high-level as shown in
figure 3.
DC-DC
block
When the power supply is turned on, the DC-DC converter which is connected to the error amplifier 1 block
The output voltage V
When the backlight is turned on, discharging starts and the current starts to flow in the resistor R7.
When the voltage V
For the light regulation of the backlight, the "voltage light-regulation" method is used, and the light is
Also, the addition of the volume to the noninverted input side of the error amplifier makes the light
When this IC is used to control the
R3
R4
V
IN 1
IN 1
REF
Figure 2. Connection method of the error amplifier 1 and 2
R
C1
; The control function is switched over from the error amplifier 1 block to the error
OUT
16
6
7
R
C
rectified by diode D1, and capacitor C1 reaches the voltage set by resistors R5, R6,
NF1
NF1
which has been set by the equation in the previous page is reached, and the high
Error amp. 1
Figure 3. Connection when the error amplifier 2 block is not used
Error amp. 2
C1
FB terminal
Error amp. 2
variable, the input voltage of the inverter is regulated so
open
11
10
R
C
OUT
IN 2
IN 2
NF2
NF2
11
10
R
decreases to a voltage lower than the set
to the inverted input terminal of error
IN 2
IN 2
To reference voltage terminal
DC-AC
inverter
FB terminal
V
Voltage Regulators
Backlight
IN 2
control
Error amplifier 2
current detection
Backlight lamp
V
V
R5
R6
IN 2
R
block
High-level
C
SBD
V
D
1
C1
1
M
A
L
P
R7