Panasonic PT47WXD63 - 47" PROJECTION TV, Техническое руководство

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Power Supply Explanation
Standby Power Supply
The incoming AC voltage passes through the surge protector R2803 and enters
the rectifier D2802 for conversion to DC. The output is then applied to the
switching regulator IC2801 via pins 3 and 5 of the transformer T2801 as drain
voltage. The startup circuit, located inside the IC, immediately starts the
oscillation. A PWM signal is output at pin 5 of the IC to build and release energy
from the transformer T2801. After the power supply starts running, the power for
IC2801 is supplied to pin 4 via diode D2811. The AC output at pin 2 of the
transformer is rectified and applied to pin 4 of the IC.
IC2803 and IC2804 provide the feedback for voltage regulation. The output
voltage at the collector of IC2804 is monitored at pin 2 of IC2801 to control the
oscillation and maintain a steady output of the power supply. Current and
transformer sensing are achieved through pin 1 of the IC.
Note:
This power supply goes into operation upon connecting the power cord to
the AC outlet. It provides constant power to the DT-Board, which houses the
CableCard. The cable service provider routinely upgrades the CableCard. To
maintain constant communication with the cable company and receive this
upgrade information, the standby circuit (not the main power supply) powers the
DT-Board.
Figure 37