LG 42PQ30 Training Manual page 36

Power Supply Basic Operation
Power Supply Basic Operation
AC Voltage is supplied to the SMPS Board at Connector SC101 from the AC Input Filter. Standby 5V is developed
from 90V source supply (which during run measures 359V). This supply is also used to generate all other voltages on
the SMPS.
The 5V (standby) voltage is routed to the Sub Micon circuit (IC701) on the SMPS and through P813 to the Main PWB
for Micon (IC1) operation. AC detect Pin 18, P813 is generated on the SMPS by monitoring the AC input and
rectifying a small sample voltage. This AC Detect Voltage is routed to (IC701) the Sub Micon on the SMPS and
through pin 18 of PG813 to the Micon (IC1) located on the Main Board and is used to Reset the Main Board.
When the Micon (IC1) on the Main Board receives an " ON " Command from either the Keyboard or the Remote IR
Signal it outputs a high called RL ON. This signal first turns on a DC level shifter on the main board which creates a
voltage called 5V General. This 5V General now provides the pull up voltages which supply the output control circuits to
the SMPS. The RL ON enters the SMPS Board (Pin 19 of P813). At the same time, the 5V General voltage also creates
a signal called 5V Det. This is routed to the main Micon and to the SMPS (Pin 17 PG813) notifying the SMPS sub-Micon
that the main board is functioning. The RL ON Voltage is sensed by the Sub Micon (IC701) circuit which causes the
Relay Drive Circuit to close both Relays RL101 and RL103 bringing the PFC source up to full power by increasing the
90V standby to 340V which can be read Fuse F801. At this time the 17V and 12V sources becomes active and are sent
to the Main Board via P813. (17V pins 1 and 2 and 12V at pins 5 and 6 of P813)
The next step is for the Micon (IC1) on the Main Board to output a high on M5V ON Line to the SMPS at P813 Pin 21
which is sensed by the Sub Micon IC (IC701) on the SMPS turning on the M5V line from P811pins 9 and 10 to the Y-SUS
board.
The last step to bring the supply to "Full Power" occurs when the Micon (IC100) on the Main Board brings the
VS-ON line high at Pin 20 of P813 on the SMPS Board which when sensed by the Sub Micon IC (IC701) turns
on the VA and VS Supplies (VA pins 6 and 7 is brought high before VS pins 1 and 2) and output from P811 to
the Y-SUS board.
Preliminary Information 42PQ30
36