Panasonic TH-37PX60U, Technical Manual

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Standby Circuit
When AC is applied to the TV, the Standby circuit outputs 5Vdc and 12Vdc. The 5V is applied to the Power
MCU and the switching transistor Q537 of the power supply circuit. The 12V is provided to the SS board. A
jumper at connector SS34 of the SS board routes the 12V back into the power supply board to turn on
Q537. When Q537 is on, the STB5V is output to the D and A boards. On the D board, the STB5V is applied
to a 3.3V regulator (IC9011). During standby operation, this regulator is kept off to disable the panel drive
circuits. The STB5V is also applied to a 3.3V regulator (IC5604) on the A board to provide the supply
voltage (STB3.3V) to the Main CPU (IC1100). The STB3.3V is also applied the Remote Control receiver
and the power LED on the K board. Furthermore, the STB3.3V is provided to the SD card slot (Not shown
in the diagram).
When the Main CPU IC1100 receives the 3.3V, it outputs the TV_SUB_ON/TUNER_SUB_ON command to
the Power MCU (IC501) located on the Power Supply board. Subsequently, the power MCU outputs the
following commands:
1. Relays ON/OFF _ To turn on the circuit that activates on the AC relays. The PFC (Power Factor
Control) circuit goes into operation to create the DC voltage needed to power the ACFB circuit.
2. VLOW ON/OFF _ to turn on the ACFB (Active Clamp Full Bridge) circuit to generate the 15V.
3. F_STB_ON/OFF _ to provide the command to turn on the DC-DC converter to output the F+15V.
The F+15V is applied to the 5V/9V regulator, IC3500, on the A board. The voltage outputs of IC3500 are
used by various circuits on the A board. To avoid catastrophic failures, they are monitored by an SOS
Detect circuit for over-voltage and over-current conditions. This SOS Detect circuit is controlled by the
TUNER_SUB_ON command from the Main CPU (IC1100). The 9V from IC3500 is also applied to a 3.3V
regulator (IC5600). The 5V and 9V from IC3500 and the 3.3V from IC5600 are connected to the CPU for
voltage presence detection.
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