Konka P2905M circuit TV protection and maintenance (a)

Konka P2905M frequency high-definition TV, Konka M Series are high-definition movement, I2C bus control circuit microprocessor system using M37281, memory model 24C16BP; I2C bus system charged with the circuit including: horizontal and TPA2010D1YZFR datasheet and vertical scan processing circuit STV6888, TDA8177F, the high frequency amplifier circuit AMT02400, audio signal processing circuit TA1314N, luminance / chrominance, synchronization signal processing circuit TB1274AF, video D / A conversion processing circuit MST9883 and TPA2010D1YZFR price and PW1225, video RGB output circuit SID2500A and TPA2010D1YZFR suppliers and so on.

Konka P2905M HD TV switching power supply primary circuit using thick film circuit KA5Q1265RF, Vice-power microprocessor to take their own power, standby power use to reduce the output voltage and cut off the main line of small-signal oscillation circuit processing circuitry way.

Konka P2905M high-definition TV, the power supplys primary focus KA5Q1265RF internal protection with overcurrent, overvoltage and thermal protection circuits. When the switching power supply failure or load circuit, switching power supply to stop working, enter the protection status; in microprocessor-controlled circuit with low voltage power supply detection circuit, low voltage power supply occurs when loss of pressure failure protection circuit starts, enter standby protection status; line, field scan processing circuit STV6888, with "X-ray" high protection circuit, the line is too large output current protection circuit. Protection circuit starts to cut off the line excitation pulse signal to the line output circuit to stop working to achieve the purpose of protection.

A protection circuit works

1. Standby control circuit

switching power supply, the voltage output four kinds: First, by VD954 rectifier, C964 filter, the output voltage of +140 V output circuits provide power supply line; the second is by VD955 rectifier, C965 filter , the output voltage of +26 V to provide power for the audio amplifier circuit; third by VD951 rectifier, C961 filter, the output voltage of +14 V, all the way through the three-terminal regulator N901 (7805) after the regulator to the microprocessor control circuit to provide +5 V / MCU power supply, microprocessor-controlled system start work; another pass VD953 control and N952 (7809), N953 (7812) regulator for digital signal processing circuit board and provide small power; Fourth, by VD953 rectifier, C963 filter, the output voltage of +5 V, regulated by the N954, the digital signal processing circuit board and a small supply power.

Konka P2905M TV standby control circuit shown in Figure 1. Consists of three parts: First, the V952, V953 composed of 9 V, 12 V power supply control circuit, standby off the small-signal processing circuit 12 V, 9 V power supply; the second is formed by the four-terminal voltage regulator N954 of +5 V, 5 VA power supply control circuit, standby off +5 V, 5 VA power supply; three by V954, VD961 main power step-down form of standby control circuit, reduce the standby power supply output voltage.

microprocessor N601 (M37281), 47 for the standby control side, these two parts of the standby control circuit controls.

1 TV stand and Konka P2905M frequency protection circuit

(1) turned on

remote boot, the microprocessor N601 47 output high, the high level is divided into two:

way through the first low-voltage power control circuit R961 V952 added to the base, V952 conduction, so that 12 V, 9 V power supply control circuit V953 conduction, the voltage to 14 V 9 V regulator circuit N952 (7809) and the 12 V voltage regulator circuit N953 (7812) of the input to digital signal processing circuit boards and small to provide 9 V, 12 V power supply. Meanwhile, V953 output voltage of 14 V through R998, R999 partial pressure, the high added N954 (PQ05RD21) in foot (control side), the N954 turn, to digital signal processing circuit boards and small to provide +5 V , 5 VA power supply, so that digital signal processing circuit boards and small start working.

second pass through R963 to the main power step-down control circuit V954 of the base, the V954 conduction, VD961 end of the sampling error amplifier TL431 (SR950) G-foot sampling voltage is not impact, switching power supply by the sampling error amplifier TL931 (SR950) control, output high voltage, which + B voltage is 140 V, power supply to the load circuit.

(2) standby

remote shutdown, low output of the microprocessor 47 N601, the low level is divided into two:

way through the first low-voltage power control circuit R961 V952 added to the base, V952 deadline, so that 12 V, 9 V power supply control circuit of the V953 is also closed, cutting off a small digital signal processing board and circuit 9 V, 12 V power supply. Meanwhile V953 collector becomes 0 V, through R998, R999 partial pressure, the N954s foot (control side) voltage down, so N954 ended, cut off the panels and small to digital signal processing circuit +5 V, 5 VA power supply , so that digital signal processing circuit boards and small to stop working.

second pass through R963 to the main power step-down control circuit V954 of the base, close to V954. Collector goes high, VD961 conduction, switching power supply output voltage of 14 V through R996, VD961 added to the sampling error amplifier SR950, G feet, the G pin voltage increases, K pin voltage is reduced, the optical coupling device N902 feet of low voltage, flow through the optocoupler N902 of the current increases, enhancing the internal light emitting diode, phototransistor current increases, the power of foot thick block KA5Q1265RF (FB-side) voltage down, pulse excitation pulse width narrows, the switch turns on time, switching power supply output voltage drop from various quarters about the boot state l / 2 or so. Line output circuit voltage is too low due to stop working, the machine into standby.

2. Protection circuit

TV Konka P2905M frequency protection circuit shown in Figure 1.

pin microprocessor N601s dedicated test pin for the protection of the feet with low-voltage external power supply detection circuit: When the low voltage power supply failure loss of pressure occurs when the protection circuit starts, enter standby protection status; horizontal and vertical scan processing circuit STV6888 of 25 (X-RAY) as "X-ray" test pin, the pin has an external "X-ray" high protection circuit, the line is too large output current protection circuit. STV6888 normal low of 25 0 V, when the 25-pin external protection detection circuit detects a fault, to 25 into the high voltage protection, STV6888 judge scanning circuit fails, cut off from the integrated circuit chip 26 feet out of line excitation pulse, the line scan circuit to stop working, so as to achieve the purpose of protection.

(1) low-voltage power supply voltage protection

the protection circuit by the microprocessor N601 pin and external isolation diode detection VD603, VD604, VD605 composition. The switching power supply control by the standby control circuit, the output of 12 V, +9 V, 8 V voltage detection, when the above-mentioned detection circuit, due to rectification / filter circuit, voltage regulator circuit is open circuit fault or serious fault load , which leads to detect loss of pressure or severe lower voltage, the corresponding detection isolation diode, the voltage of the microprocessor N601s pin down, the microprocessor circuit judge to be detected loss of pressure failure occurs, to take protective measures , false feet from the N601 Guane standby standby control side control voltage output, standby protected.

(2) line output over-current protection

line output overcurrent protection, also known as + B overcurrent protection circuit, resistor R981 and testing by the sampling transistor V967 and R988, R989, VD970 composed of lines of output current for testing.

when the line output circuit abnormalities (such as inter-turn short circuit FBT) caused by line scan circuit current increases, resulting in sampling the voltage drop across resistor R981 reaches a certain value, V967 turn, set electrode becomes high, the R988, R989 divider, the voltage breakdown diode VD970, 25 feet into the STV6888 high trigger voltage, STV6888 take protective measures to cut off 26 feet out of line excitation pulse, The protection state. Line scan circuit to stop working to avoid a line output circuit overcurrent harm.

(Continued)