Panasonic tc-22lh1 technical guide Service Manual
1.6 Backlighting
Backlighting Brightness for Panasonic’s line of LCD TVs is accomplished through the
use of Cold Cathode Fluorescent tubes (CCFT), which is currently the light source of
choice, by a number of leading manufacturers.
use of Cold Cathode Fluorescent tubes (CCFT), which is currently the light source of
choice, by a number of leading manufacturers.
1.7 Inverter Power Supply
Pulse width modulation is a very straightforward method for controlling the brightness of
the CCF tube(s). The inverter is turned on and off (using the input or an enable/disable
line) from the Microprocessor Unit (MPU) to control the brightness. The “on” duty cycle
is lengthened to increase the brightness and reduced to decrease the brightness. One
of the major advantages of pulse width modulation is the tube is always fully “on” or fully
“off” and full starting voltage is always applied to the tube(s) (assuming nominal input
voltage. Figure 5 is a simplified diagram of a pulse width modulated DC to AC inverter.
the CCF tube(s). The inverter is turned on and off (using the input or an enable/disable
line) from the Microprocessor Unit (MPU) to control the brightness. The “on” duty cycle
is lengthened to increase the brightness and reduced to decrease the brightness. One
of the major advantages of pulse width modulation is the tube is always fully “on” or fully
“off” and full starting voltage is always applied to the tube(s) (assuming nominal input
voltage. Figure 5 is a simplified diagram of a pulse width modulated DC to AC inverter.
Figure 5
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