Hitachi 51F510, Manual

Page: 19 / 152

DP-4X STAND BY +5V POWER SUPPLY GENERATION EXPLANATION
PAGE 01-13
STAND-BY +5V POWER SUPPLY GENERATION EXPLANATION:
The Stand By power supply operates anytime the set is plugged into an AC outlet. Shown
below in Figure 1 is the Stand By power supply.
IC101 is the Driver IC for this supply. It’s
a self contained Oscillator, Driver IC. It switches the primary of
T101
.
The secondary of
T101 produces the SBY +5V via the rectifier D103 and filter C106 . Then
the voltage is clamped by ZD101 .
A feedback to
IC101 is supplied by the photo coupler PC102 for regulation purposes.
•
IC102 works as a variable resistor attached to the cathode of the internal LED inside
IC102 . As the SBY +5V changes so will the resistance of IC102 . Voltage Up, Resis-
tance goes Down. As the Resistance goes down the Light emitted from the LED will in-
crease. As the Light increases from the LED, the receiver will conduct more heavily.
This decreases the voltage fed back to
IC101 causing the internal circuits within IC101
to reduce the primary switching of T101 and reduce the SBY 5.7V line back to normal.
Figure 1
DS101
C105
L102
F103
- +
D102
PC102
T101
D103
C106 ZD101
IC102
SBY +5V
IC101
C106 R110
R113
R114
R115
R111
C109
R112
C110 C107