V40006903 datasheet(4/63 Pages) TOSHIBA

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SWITCH-MODE POWER SUPPLY (TDA16846)

A SMPS transformer controlled by the IC TDA16846, which is designed for driving, controlling, and protecting switching

transistor, provides the DC voltages required at various parts of the chassis. SMPS generates the necessary 3.3V and 2.5V

supplies for the micro-controller, 130V supply for the FBT, +/-16V supply for the audio amplifier, which are active in stand-by

and 8V, 12V and 5V supplies for other different parts of the chassis.

When the TV is switched on, a reference voltage is provided to TDA16846 and the start-up operation occurs, then TV

enters into the stand-by position.

Two optocouplers are used to control the regulation of line voltage and stand-by power consumption. There are two regula-

tion circuits, one in primary side and one in secondary side. The primary regulation circuit provides a control voltage to pin3

of the IC. Secondary regulation circuit produces a control voltage according to the changes in 130V DC voltage, via an

optocoupler (SFH617A) to pin4 of the IC.

During the switch on period of the transistor, energy is stored in the transformer. During the switch off period energy is fed

to the load via secondary winding. By varying switch-on time of the power transistor, it controls each portion of energy

transferred to the second side such that the output voltage remains nearly independent of load variations. At the same time,

the supply voltages 12V, 8V, 5V are stabilised by the series regulators.

Features:

n Line Current Consumption with PFC

n Continuous Frequency Reduction with Decreasing Load

n Stable and Adjustable Stand-by Frequency

n Very Low Start-up Current

n Soft-Start for Quiet Start-up

n Adjustable and Voltage Dependent Ringing Suppression Time

n Synchronization and Fixed Frequency Facility

n Over- and Under-voltage Lockout

n Switch Off at Mains Under-voltage

n Mains Voltage Dependent Fold Back Point Correction

n Low Power Consumption

n Free usable Fault Comparators

Pinning:

1. OTC

Off Time Circuit

2. PCS

Primary Current Simulation

3. RZI

Regulation and Zero Crossing Input

4. SRC

Soft-Start and Regulation Capacitor

5. OCI

Opto Coupler Input

6. FC2

Fault Comparator 2

7. SYN

Synchronization Input

8. N. C.

Not Connected

9. REF

Reference Voltage and Current

10. FC1

Fault Comparator 1

11. PVC

Primary Voltage Check

12. GND

Ground

13. OUT

Output

14. VCC

Supply Voltage

IF PART (TDA4470/72)

The TDA44XX is an integrated bipolar circuit for multistandard video/sound IF (VIF/SIF) signal processing in TV/VCR

and multimedia applications. The circuit processes all TV video IF signals with negative modulation (e.g., B/G standard),

positive modulation (e.g., L standard) and the AM, FM/NICAM sound IF signals. Active carrier generation by FPLL (fre-

quency phase-locked loop) is the principle for true synchronous demodulation. VCO circuit is operating on picture carrier

frequency, the VCO frequency is switchable for L´-mode. AFC without external reference circuit is alignment-free and

polarity of the AFC curve is switchable. VIF-AGC for negative modulated signals operates on peak sync detection principle

and for positive modulation on peak white / black level detection principle. Tuner AGC is adjustable with determining take

over point. It has alignment-free quasi-parallel sound (QPS) mixer for FM/NICAM sound IF signals. Intercarrier output sound

is gain controlled (necessary for digital sound processing). AM-demodulator is completely alignment-free with gain control-

led AF output. Operation of the AM demodulator and QPS mixer (for NICAM-L stereo sound is parallel. TDA4472 is used for

negative modulation and TDA4470 is used for both negative and positive modulation.

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