Sharp 32LF-94EC, Service Manual, Page: 28 / 82

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AK53 D.O.C. Service Manual 22/03/2004
Functional block diagram of ADOC:
5.SOUND OUTPUT STAGE WITH TDA7480L
The TDA7480L is an audio class-D amplifier assembled in Power DIP package specially designed for
high efficiency applications mainly for TV and Home Stereo sets.
Mute stand-by function of the audio amplifier can be described as the following; the pin 12
(MUTE/STAND-BY) controls the amplifier status by two different thresholds, referred to ground. When
Vpin 12 voltage is lower than 0.7V the amplifier is in Stand-by mode and the final stage generators are
off. When Vpin 12 is higher than 4V, the amplifier is in play mode.
The TDA7480L is a 10W+10W stereo sound amplifier with mute/stand-by facility. MUTE control signal
coming from microcontroller (when it is at high level) activates the mute function. IC is muted when
mute pin is at low level (pin12). MUTE pin can also be activated via an external pop-noise circuitry in
order to eliminate pop noise when TV is turned off. Just after the TV is turned off, this circuit switches
the IC to stand-by mode by pulling the mute pin voltage to ground.
6.VERTICAL OUTPUT STAGE WITH STV9379FA& TDA8177F
The IC STV9379FA
&
TDA8177F is the vertical deflection booster circuit. Two supply voltages, +14V
and –14V are needed to scan the inputs VERT+ and VERT-, respectively. And a third supply voltage,
+60V for the flyback limiting is needed. The vertical deflection coil is connected in series between the
output and feedback to the input.
7.VIDEO OUTPUT AMPLIFIER TDA6108JF
The TDA6108JF includes three video output amplifiers is intended to drive the three cathodes of a color
picture tube.
8.POWER SUPPLY PART
In Large Signal Board
The DC voltages required at various parts of the chassis are provided by an SMPS transformer
controlled by the IC MC44608, which is designed for driving, controlling and protecting switching
transistor of SMPS. The transformer generates 135V for FBT input, +/-14V for audio amplifier, 8V, 12V,
V8Stby ( needed for step down converted for small signal board) and 5V supplies for other different
parts of the chassis.