The fault detection and protection of the protection circuit are accomplished by the microprocessor, and the microprocessor is the core of the protection circuit. U circuit board microprocessor IC1101 (MSDA6000) (127 feet (protect) located is a separate set of protection and detection end, connected by the connector U2/A1102 (9), foot and A2/D2 (4) feet and D circuit board fault detection circuit, the power supply, and the field scanning circuit were detected. During normal operation of the television, IC1101 (127) foot high level, detection circuit failure (127) voltage pin pull low low level, the microprocessor accordingly judgment by the detecting circuit failure, from IC1101 92 feet (on / off control terminal of) outputs a low level standby control voltage. The voltage through the pin of the connector Ul/All01 (9), foot and A2/D2 sent to Q882 D on the circuit board base, cut-off Q882, will release relay RL801, cut off the power supply of the main switching power supply, to protect.

Microprocessor IC1101 (127) feet outside the establishment of protection and detection circuit, detection fault, output electrical detection was divided between two: is the output low level, with a "C" in the nodes of the graph is connected, through the isolation diode D867 (MA2C165001VT), D869 MA2C165001VT directly the microprocessor (127) voltage pin is pulled low; another high output level, collected as shown in the figure, the node "B", through the R871 will be added to the high level triode tube Q854 (2SC3311AQA) base forced Q854 saturated hydraulic conductivity through the microprocessor IC1101 (127) pin voltage is pulled low.

Microprocessor IC1101 (127) foot connected + B overcurrent detection, 14V power loss of pressure detection, line output overvoltage detection, AFC pulse overvoltage detection, EW (East and West) overvoltage detection and correction, field power loss voltage detection, output fault detection, multiple fault detection circuit.

1.+B over current detection circuit

+B (2.2 /7W R867) and Q851 (2SA10160QA) and peripheral components of the output current sampling resistor. IC1101 feet (127 IC1101 Q854 Q854 (MA2C165001VT d859 ((by conduction voltage conduction R867 + B + B: cut-off, Q851 R867 (+ load circuit is the main line of the output circuit is normal, the voltage drop is smaller, the protection circuit is not affected when the load circuit, especially line scan circuit short-circuit and leakage fault, causing the output current is increased, the voltage drop increases, forcing Q851 guide R854 33K Ohm) R855 of 120 ohm divider, through the diode to provide a positive bias voltage, conduction, the microprocessor voltage is low, the microprocessor from (92) feet standby output control voltage into the protection of the state.

2.14V power loss detection circuit

Microprocessor IC1101 (127) pin 14V directly to the D867 voltage of the switch power output detection. 14V voltage is normal, cut-off D867, microprocessor IC1101 (127) feet do not produce effect: when the 14V voltage due to the load short circuit or rectifying and filtering circuit is open, resulting in loss of 14V voltage, D867 conduction, microprocessor IC1101 (127) voltage pin is pulled low microprocessor from IC1101 (92) feet standby output control voltage, enter the state of protection.

3 line output over-voltage detection circuit

By the rectifier diode D593 (BOEAKM000058) filtering circuit of c591 (10 mu F/50V), divided into pressure resistance R592 (11.3k omega) R591 (9.1k omega) and the detection circuit D592 MA24104JOF, D591 MA2C165001VT. On line output transformer of T551 4 ~ 5 filament winding voltage detection. When the output voltage is normal, the filament voltage within the normal range, the voltage of the D593 rectifier, C591 filter and R592, partial pressure of R591, less than D952 zener diode voltage value, the D952 cutoff, the protection circuit has no effect: when the output voltage for power supply voltage rises, against the cause and process of capacitor circuit such rises, the filament voltage increased, filament voltage increased after D593, after rectification, C591 filtering and R592, partial pressure of R591, higher than D952 zener diode voltage value, D952 breakdown conduction, provides positive bias voltage to Q854 through D591, Q854 conduction, IC1101 (microprocessor the 127 foot low voltage), IC1101 (92 feet) from the microprocessor output standby control voltage, enter the state of protection.

4 line AFC overvoltage detection circuit

Voltage is detected by R594 (330k), MA243600MF (D595) and D594 (MA2C165001VT), and the AFC voltage is detected by C572, C556 and C555. AFC voltage is normal, below ad595 zener diode voltage value, cut-off ad595, the protection circuit does not affect: when the output pulse voltage increase or AFC divider capacitor deterioration, open reason causing AFC voltage increased, zener diode D952 breakdown, by D591 to Q854 provides positive bias voltage. Q854 conduction, microprocessor IC1101 (127) voltage pin is pulled low, the microprocessor from the IC1101 (92) feet standby output control voltage into the protection of the state.

5.EW (thing) correction of over-voltage detection circuit

(MA241000MF), D862 (MA243600MF) and D861 (MA2C165001VT), the voltage of the voltage regulator diode (D863), the voltage of the EW (the thing) is detected. Line scan circuit is added EW correction circuit of pulse voltage is normal, below zener diode D863, D862 series Zener values enable D863, D862 are closing, does not have the influence to the protection circuit, when the output pulse voltage increases or the inverse process, deflection, EW correction circuits, input to the EW correction circuit of pulse voltage rise, voltage regulator diode D863, D862 breakdown, through D861 to Q854 provides positive bias voltage, the Q854 conduction, the microprocessor IC1101 (127) voltage pin is pulled low, the microprocessor from the IC1101 (92) feet standby output control voltage system, enter the state of protection.

6 positive power loss detection circuit

The V-VCC+ voltage provided to field output circuit IC451 (LA7876N) were detected by the microprocessor IC1101 (127 feet by D869 MA2C165001VT directly on the line output transformer T551 6 ~ 7 winding through D854 (RU2MLFA1) rectifier, C865 (2200 mu F/25V) filtering. V-Vcc+ normal voltage, cutoff D869, the microprocessor (127) foot does not produce effect; when the voltage V-Vcc+ due to the load short circuit will fuse resistance R861 burned or rectification and filter circuit open, resulting in loss of voltage V-Vcc+ D869 conduction, microprocessor IC1101 (127) voltage pin is pulled low microprocessor from IC1101 (92) feet standby output control voltage, enter the state of protection.

7 negative power loss detection circuit

By the Q854 through diode D865 MA2C165001VT on line output transformer T551 and to the winding through D853 (RU2MLFA1) rectifier, C864 (2200 mu F/25V) filtering, the V-Vcc- voltage provided to field output circuit IC451 detection. V-Vcc- normal voltage, cutoff D865, the protection circuit does not produce effect; when the voltage V-Vcc- due to the load short circuit caused by insurance resistance R862 burned or rectification and filter circuit open and cause loss of voltage V-Vcc-, D865 through positive voltage output circuit IC451 loop and conduction, to the Q854 provides positive bias voltage. Q854 conduction, microprocessor IC1101 (127) voltage pin is pulled low, the microprocessor from the IC1101 (92) feet standby output control voltage into the protection of the state.

8 field output detection circuit

In a circuit board d452 MA3X152KOL, Q451 2SD0801AOL and d454 MA3X152KOL and peripheral components, to the foot of the voltage of the field output circuit IC451 were detected. Field output circuit of IC451 is normal, IC451 and foot pulse voltage output, the R455 (100) D452, C451 and shunt rectifier (47 F/35V) after filtering, through the resistor R467 (470), R468 (220K) provides positive bias voltage to Q451, Q451 conduction, collector for low level, D454 is off, the protection circuit has no effect on the spot: integrated circuit damage output or because the power supply fault and no pulse voltage output, D452 and Q451 as collector, Q451 goes high, D454 conduction, provides positive bias voltage to the Q854 through the Al/Dl connector pin, Q854 conduction, the microprocessor IC1101 (127 feet) low voltage microprocessor, IC1101 (92) from the standby pin output control voltage, enter the state of protection.