Panasonic PT47WXD63 - 47" PROJECTION TV, Техническое руководство

Страница: 76 / 99

Main Power Supply
D-Board
Figure 38
The main power supply for the PT- 47WXD53 is contained on the "D" board
When the power switch is activated, transistor Q802 turns on to activate the rel
RL801. AC is applied to the circuit via the relays RL801 and RL802. In its
operation, the main power supply is similar to the main power supply introduced
earlier in some Panasonic chassis such as the "P2 Chassis". It is a switch-mode
converter with current and voltage feedback loops.
.
ay
01.
d
s used
t energy. After the
itial current surge subsides, a DC voltage developed at the secondary of the
lied to
01 via the resistor R862. The voltage on pin 7 of the IC causes it to
AC is routed through RL801 and surge resistor R800 to the rectifier circuit D8
When the unit is turned on, an inrush of current occurs as capacitors are charge
and other components reach the desired voltage level. The resistor R800 i
to absorb the initial excess current, transforming it into hea
in
transformer (not shown in the figure) turns on RL802 to shunt the resistor R800.
This minimizes heat and increases efficiency.
D801 rectifies the AC voltage into approximately 180Vdc, which is then app
the drain of Q801 via the transformer T801. Startup Power is initially supplied to
pin 7 of IC8
72