Daewoo-Sony VX 14A1 – VX14AW1 – VX21AW1 – Circuit Diagram – TV-VCR combo: Service Mode - STR F6626 - SMPS - working principle

 Used ICs: STR-F6626 – LA78041 – 24LC08B – LA71076AM – LA76834 – TDA7442 – MM1053 - TDA7267:  Working Principle of SMPS power Regulator Circuit, using STR F6626

Features of the model

1) Chip for TV / video are all 1-Chip.

2) Light / NO adopt the deck of CONNECTOR.

3) Easy to adjustment in the non-adjustment or the remote control.

4) during the operation of the protector circuit, displayed on the LED (vertical protector service during the on / off possible).

5) It can operate without deck.

6) Can service only in the user remote control.

SMPS and Deflection PWB and Circuit Diagram

SMPS Working

Power supply unit Operation (STR-F6626-related)

Vin terminal

START circuit detects the Vin terminal voltage, a circuit for performing the operation start and stop control the IC.

Initial AC power input, and by the condenser (C810) starting resistance of control outside the IC (R806), rising Vin terminal until the operation start voltage (14V)  from the control circuit in the IC to work.  After the control circuit operation, the Vin terminal by TURN ratio wrapped in proportion to the secondary side B + join a stable BACK UP power.  When the B + power on the secondary side drops to about 1/10 than normal (11V), 1 order of Vin fall even in the same proportion UVLO (Under Voltage Lock Out) is to operate . Then, joined by Vin through the start-up resistance again, this voltage is operates in the same manner as the first and leading to 16V.

Oscillator and OCP / FB pin 1

Oscillator of the internal control IC is the reference voltage input terminal is OFF.

IC will start operation by the internal oscillator and Vin voltage reaches the operation start voltage (14V). Internal oscillator, when the charging voltage of the internal C1 is 3.7V

OSC is turned ON, the voltage of C1 is increased to 6.5V.

When the internal oscillator to oscillate MOSFET can Vocp turns ON. This voltage is led OCP / FB terminal, internal OCP / FB COMP voltage

There MOSFET is turned OFF when it comes to 0.73V.

Voltage of C1 is maintained at 6.5V when ON of the MOSFET, to gradually discharge and turned OFF. Discharge time is determined by an internal RC, 50uS

When the discharge to become 3.7V MOSFET is turned ON, IC performs the basic operation by repeating this kind of behavior.

Over-current protection circuit (OCP = Over Current Protector)

OCP circuit operates in PULSE BY PULSE system detects the DRAIN current directly.  Circuit is constituted by COMPARATOR as in Figure 2. Detection voltage Yes is set to -1.37V with respect to the GND of the internal control IC.  No more voltage is turned OFF the internal oscillation operation and participate.

LATCH function  OVP = Over Voltage Protector

OVP (overvoltage protection) circuit and TSD (overheat protection) circuit during operation, a circuit for stopping the operation of the power supply circuit to maintain the output of the oscillator to OFF.

If the operation of the OVP and TSD persists more than 8uS to prevent malfunction due to noise, it is set to work.  When the LATCH circuit operates, Vin voltage of the IC drops to sharply stops operation voltage. Motion also internal constant-voltage circuit is followed by the LATCH circuit operates.  The other hand to work, is because the Vin voltage is not applied to continue.

When the Vin voltage drops to less than the operation stop voltage, IC is asked to supply the Vin through the start-up resistor for the restart, to 16V of operation start voltage reach and, Vin is rapidly decreases with increasing again circuit current. In this case, Vin repeats the UVLO, IC does not operate.

After the order to release the LATCH state, but it should go up from down Vin until less than 6.5V, in general turn off the AC INPUT, comeback It must be dynamic. (Refer the above given circuit)

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Circuit Diagram (Syscon - Tuner VIF and Chroma) & PWB

How to enter and the attitude to the service mode

User remocon sequentially enter in the button input of.

"Menu" => "10" => "11" => "Volume (+ or ►) within 3 seconds.

Currently, the term that has been selected is displayed in red, it can move to the adjustment in the direction button. At the time of the service mode is canceled

Press and hold until exiting the "menu" key.

Or press the "Power" key. ( after the adjustment, the memory of the Data is separately required)