Power Supply Basic Operation - LG 42PJ350 Training Manual

Power Supply Basic Operation

Power Supply Basic Operation
AC Voltage is supplied to the SMPS Board at Connector SC101 from the AC Input assembly. Rectified by the Bridge
rectifier D101 generates a primary B+. The Power factor circuit generates a Primary supply which can be read at Fuse F302
160V. This primary voltage is routed through T301 and routed to the Standby 5V supply. The STBY5V (standby) is B+ for
the Controller chip on the back of the board (IC701) on the SMPS and output at P813 pins 13 and 14 then sent to the Main
board for Microprocessor (IC1) operation (STBY 3.49V RUN 5.23V).
When the Microprocessor (IC1) on the Main Board receives a "POWER ON" Command from either the Power button or
the Remote IR Signal, it outputs a high (2.43V) called RL_ON at Pin 15 of P813. This command causes the Relay Circuit to
close both Relays RL101 and RL103 routing AC to the Bridge Rectifier D101 which then routes the primary voltage to the
PFC circuit (Power Factor Controller) 390V which can be read measuring voltage at Fuses F302 (390V) and F801 (389V)
from "Hot" Ground. AC Detection (AC Det) is generated on the SMPS, by rectifying a small sample of the A/C Line and
routed to the Controller (IC701) where it outputs at P813 pin 16 (4.45V) and sent to P301 to the Main Board where it is
sensed and monitored by the Main Microprocessor (IC1). If AC Det is missing the set will come on, but shut off in 10
seconds.
When RL_ON arrives, the run voltage +5V source becomes active and is sent to the Main Board via P813 (5.24V at
pin 5, 6 and 7). The (Error Det) from the SMPS Board to the Main Board can be measured at pin 8 of P813 (2.88V STBY
and 4.93V RUN), but it is not used. The RL-ON command also turns on the 17V (Audio B+ 16.79V) which is also sent to the
Main Board. The 17V Audio supply outputs to the Main board at P813 pins 1 and 2 and used for Audio processing and
amplification.
The next step is for the Microprocessor IC1 on the Main Board to output a high (3.27V) on M_ON Line to the SMPS at P813
Pin 17 which is sensed by the Controller IC701, turning on the M5V line and outputs at P811 pins 9 and 10 to the Y-SUS
board.
The Controller (IC701) also uses the M_ON line to turn on the VA and the VS supplies. (Note there is no VS On Command
in this set). VS is output at P811 to the Y-SUS board P201. (VA pins 6 and 7 and VS pins 1 and 2). Note: The Va is fused
on the Y-SUS then routed out P209 to the X-Board Left. VS is also routed out of the Y-SUS P206 pins 1 and 2 to the Z-SUS
P2.
AUTO GND Pin 18 of P813: This pin is grounded on the Main board. When it is grounded, the Controller (IC701) works in
the normal mode, meaning it turns on the power supply via commands sent from the Main board. When AUTO GND is
floated (opened), it pulls up and places the Controller (IC701) into the Auto mode. In this state, the Controller turns on the
power supply in stages automatically. A load is necessary to perform a good test of the SMPS if the Main board is suspect.
37 August 2010 42PJ350 Plasma