Toshiba TLP510E Manual de formação técnica - Página 28

Procurar online ou descarregar pdf Manual de formação técnica para Projetor Toshiba TLP510E. Toshiba TLP510E 47 páginas. 3lcd data projector
Também para Toshiba TLP510E: Manual de serviço (33 páginas)

Imprimir página

7. VIDEO CIRCUIT

7-1. Circuit Component

The video circuit performs selection of input signals,

video signal (NTSC, PAL, SECAM) demodulation to

RGB signals, RGB input signal amplification and audio

signal amplification.

Fig. 7-1-1 shows the block diagram.

7-1-1. Input Signal SW Section

All the video and audio signals entered are sent to the

input SW IC (except for RGB signals). In the input SW

IC, the signals are switched corresponding to the

composite, Y/C and color modes (NTSC, PAL SECAM

and BLACK & WHITE) respectively. Processing routes

for the composite video signals are changed depending

on the color modes (NTSC, PAL, SECAM and BLACK &

WHITE). Y/C signals, SECAM and Black & White

signals are supplied to the video color process IC in the

next stage passing through the input SW IC. NTSC, PAL

and 4.43 NTSC color signals only are separated into the

luminance Y signal and color C signal by the digital

comb filter and then enter the input SW IC again as the

Y/C signals.

In the cases other than described above, when the power

is on or the input switching occurs, the signals are

supplied to the video/color process IC as a composite

video signal passing through the input SW IC.

The RGB signals entered are divided in two systems; the

internal signal process and external output systems.

The signals for the external output system enter 75 ohm

driver IC and then enter D-sub 15 pin for output. The

RGB signals for internal signal process system enter the

mute IC. When the video signal is selected, the RGB

signals are muted by the mute IC output.

7-1-2. Video Demodulation Section

In the video demodulation section, the composite video

signal and Y/C signals are demodulated into the RGB

signals.

In the video/color process IC, the color demodulation is

carried out corresponding to the color mode of the video

signal entered. The applicable color modes are NTSC,

4.43 NTSC, PAL and SECAM.

The mode identification is automatically carried out by

the video/color process IC.

When the power turns on and the input is switched, the

composite video signal passing through the input SW IC

enters and the color mode is determined. The micropro-

cessor detects the result of color mode determination and

sets a corresponding color mode. The color difference

signal demodulated by the video/color process IC is

developed after processed its phase and signal level via

1H delay IC.

The luminance signal enters the picture quality correc-

tion IC and the color difference signal enters the RGB

demodulation IC via the delay line for matching with

the luminance signal.

In the RGB demodulation IC, the gamma correction,

color adjustment, etc. are carried out as well as the

luminance color difference signal is demodulated to the

RGB signals.

7-1-3. RGB Signal Amplification Section

In the RGB signal amplification section, the RGB input

signals and the video signal demodulated to the RGB

signals are switched and the contrast and brightness

adjustments are carried out. Further, the gain adjustment

for each RGB signal is also carried out.

The sync signals of the RGB signals correspond to

HD,VD, composite sync (CS) and SYNC ON G signals.

7-1-4. Audio Signal Amplification Section

The audio signal inputs of the video and RGB inputs

correspond to L and R stereo input. After switching the

input, the signal develops at the audio terminal through

the output buffer circuit. After L and R signals are mixed,

the sound volume control IC controls its level, thus

controlled signal is amplified to the sufficient level to

drive the speaker by the audio output IC, and then sent

to the speaker.

7-1