Green Led Power Block; Blue Led Power Block - Sony BVM-L230 Service Manual

2-2-1. Green LED Power Block

A separately excited-type composite current resonance
system is employed as a circuit system. This enables high
efficiency and low noise.
The green LED power mainly consists of the parts and
circuits below.
. IC6200 (Current resonance power IC)
. Q6201 and Q 6202 (FET)
. C6213 (Resonance capacitor)
. T6200 (PIT transformer)
. Rectifier circuit on secondary winding
In circuit configuration, two FET (Q6201 and Q6202)
switches, a resonance capacitor (C6213), and a PIT
transformer (T6200) form half-bridge for an input voltage
(PFC+) and output a voltage through the rectifier circuit
on the secondary winding of a PIT transformer (T6200).
A control signal is input from a feedback circuit consisting
of a shunt regulator (IC6250), which controls the constant
voltage of a G_OUT voltage, to a current resonance power
circuit (IC6200) through a photocoupler (PH6200). This
control signal changes the oscillating frequency of a
current resonance power circuit (IC6200) and produces the
constant voltage of a G_OUT voltage.

2-2-2. Blue LED Power Block

A separately excited-type composite current resonance
system is employed as a circuit system. This enables high
efficiency and low noise.
The blue LED power mainly consists of the parts and
circuits below.
. IC6300 (Current resonance power IC)
. Q6300 and Q 6301 (FET)
. C6313 (Resonance capacitor)
. T6300 (PIT transformer)
. Rectifier circuit on secondary winding
In circuit configuration, two FET (Q6300 and Q6301)
switches, a resonance capacitor (C6313), and a PIT
transformer (T6300) form half-bridge for an input voltage
(PFC+) and output a voltage through the rectifier circuit
on the secondary winding of a PIT transformer (T6300).
A control signal is input from a feedback circuit consisting
of a shunt regulator (IC6350), which controls the constant
voltage of a B_OUT voltage, to a current resonance power
circuit (IC6300) through a photocoupler (PH6300). This
control signal changes the oscillating frequency of a
current resonance power circuit (IC6200) and produces the
constant voltage of a G_OUT voltage.
BVM-L230
2-2-3. Way to Change G_OUT and B_OUT
Voltages
The output voltages (G_OUT and B_OUT voltages) of
green and blue LED power supplies are designed that they
can be changed in consideration of the change due to the
dispersion in each LED VF value of LED backlight and the
temperature characteristics of an LED VF value.
n
Refer to the figure below for how to change an output
voltage.
T6200/T6300
Output voltage from
auxiliary winding on
Current
secondary winding
resonance
IC Input to
Photocoupler
FB pin
Shunt
regulator
Output voltage variable signals (VF_FB_G and VF_FB_B)
are input from the LMD2 board to each feedback circuit of
green and blue LED power supplies through variable range
setting resistor R1 (consisting of R6259 and R6357).
An output voltage varies depending on the voltage value (0
V to 3.3 V) of voltage variable signals (VF_FB_G and
VF_FB_B).
The output voltages of green and blue LED power supplies
are described below.
. Green LED power output voltage:
18.97 V to 23.53 V (Error ± 0.37 V)
. Blue LED power output voltage:
18.97 V to 23.53 V (Error ± 0.37 V)
G_OUT/B_OUT
Feedback circuit
VF_FB_G/VF_FB_B
Variable range
setting resistor
R1
2-5