Samsung SR-S25NTA - Page 36

5,
Resonance
output
circuit
To
make
the
life-span
of
fluorescent
light
bulb
longer,
supply
the
filament
pre-heat
current.
Line
current
is
running
through
filament
+
Ce—
RT:
~filament
—
Cs
—
PT.
Resistance
value
is
increased
at
PT;
by
running
of
PTC
pre-heat
current.
When
impedance
of
PT)
is
Higher
than
impedance
of
Cy,
the
current
runs
toward
C7
and
so,
discharge
voltage
is
permitted
to
both
ends
of
lamp.
And
finally,
discharge
occurs
at
lamp
as
a
result
of
resonance
of
L
and
C.
After
LAMP
is
ON,
the
resonance
current
runs
through
lamp
—
RT2—
Cs
PTh.
6. Guard circuit
On
abnormal
operation
of
LAMP
or
abnormal
operation
of
switching
circuit,
toward
Dy,
more
than
0.7
V
of
voltage
is
held
at
GATE
of
SCR
and
so,
SCR
operates
to
block
power.
When
abnormal
voltage
or
over-voltage
is
held
at
power
part,
FUSE
at
the
primary
power
circuit
is
gone
to
block
the
power.