However, in order to allow auto-recovery from power saving off state, the SMPS circuit is
designed as an unlatched type, the DC current flows via R849 Q850, R850 to charge C866A again,
when the voltage across C866A has reached 16V, I862 is turned on again. Once the peak voltage
across R867 is over 1Vp-p, I862 will be forced off again.
Consequently, the I862 is turned on and off repeatedly, and the power is not be switched off,
Q868 and R808 may be over stressed and fail.
6-2 Power Management Circuit
There are four modes of indicator in this power LED described as below, the first mode,
“green-indicator “ indicates the normal state; “yellow-indicator“ indicates the stand-by state mode
The fourth mode, “ amber-indicator “ indicates the power saving off state. Both H. sync and V.
sync are off
I501
MODE
#40
V
#39
H
#23 #21 D862
LED
NORMAL 1 1 1 1
GREEN
STAND
BY
1 0 0 1
YELLOW
SUSPEND 0 1 0 1
YELLOW
OFF
0 0 0 0
AMBER
When the display signal enters the “suspend “ state of power saving, with V. sync off, the
voltage at pin31 of I501 is low, Q821 is OFF, and Q820 is OFF too. This will shut down the
oscillation of the horizontal and vertical deflection, then power conservation is achieved.
When the display signal enters the “ off ” state of power saving with both H. sync and V. sync
off, the voltage at pin31& pin 29 of I501 are low, then Q820 and Q822 are off, there is no 8V &
14V Voltage for the circuit.
The overall power dissipation is significantly reduced to less than 5W watt; exclusive audio
power consumption.
To recovery from off state to normal state is automatic since the recovery H. sync and V. sync
will trigger I501 via Q550 &Q556, The voltage on pin 29 & 31 will go to high again and turn on
Q822, Q820 via Q823, Q821
.
