Panasonic TC-34P500G flat screen TV is Panasonic company developed the new color TV, is a movement for EUR07 and sharp screen GIGAS00 series, similar models and TC-29P500G etc.. I2C bus control technology is used in this movement. In the image and audio processing circuit with a lot of new technology, to achieve the line scan of 1080 line and field scanning 50 games, high - definition display and 4:3 and 16:9 display mode, can 5.1-channel Dolby AC-3 and DTS digital format digital surround signal and home theater sound. The series of color TV circuit is complex, and the integrated circuit is as high as 100, and it is equipped with a sound over current, over voltage and over voltage protection circuit.
Protection circuit principle
The TV series protection circuit is more complex, distributed in several circuit boards, connected by connectors. After the author of the protection circuit analysis, drawing the overall protection circuit as shown in the following diagram. For the convenience of the reader to understand distribution circuit protection, figure draw the circuit board protection circuit is connected between the connecting piece and the name of the pin, connecting line of small boxes represent connections, the box next to the two plug connected pieces of the name, the box inner connecting wire pins.
The fault detection and protection of the protection circuit are accomplished by the microprocessor, and the microprocessor is the core of the protection circuit. In 127 feet u circuit board microprocessor IC1101 (SDA6000) to set up a separate protection and detection pin protect, connected to an d circuit board on the Sun Deyin fault detection circuit by 4 feet of the connector U2 / a1102 anlyses feet and A2/D2. Detection of power supply and line and field scanning circuit. During normal operation of the TV set, 127 feet high level: be detected circuit failure, 127 foot change to a low level, the microprocessor accordingly judgment by the detecting circuit failure, from 92 foot switch control end of output low level standby control voltage. The voltage through the 1 foot of the connector U1/A1101 (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 127 feet external protection and detection circuit is divided into two kinds: is the output low level, and figure 1 node C is connected, through the isolation diode D867 (MA2C165001VT), D869 MA2C165001VT directly the microprocessor 127 foot voltage low; another output high level and aggregated to the node B shown in Figure 1, by R871 will be added to the high level triode tube Q854 (2SC3311AQA) base, forcing Q854 saturated conduction, microprocessor and the pin voltage is pulled low.
Microprocessor 127 feet pick + B overcurrent detection, 14V power loss of pressure detection, line output overvoltage detection, AFC pulse overvoltage detection, EW overvoltage detection and correction, field power loss voltage detection, output fault detection, multiple fault detection circuit.
1.+B over current detection circuit
7W (2.2 / R867) and Q851 (2SA10160QA) and peripheral components of the output current sampling resistor by +B. +B load circuit (the main output circuit) is normal, the voltage drop on the Q851, R867, the protection circuit is not affected. When the +B load circuit, especially the line scan circuit is short circuit, leakage fault, causing the +B output current increases, the voltage drop on R867. Forced Q851 conduction and conduction voltage after R854 (33K omega), R855 (120 ohms) partial pressure, through the diode d859 MA2C165001VT to Q854 provides positive bias voltage. Q854 conduction, the microprocessor 127 foot voltage low, the microprocessor from 91 feet standby output control voltage, enter the state of protection.
2.14V power loss detection circuit
Microprocessor 127 pin D867 directly to the 14V voltage of the switch power output detection. When the 14V voltage is normal, the D867 has no effect on the 127 pins of the microprocessor. When the 14V voltage is due to the load short circuit or the open circuit of the rectifier filter circuit, causing the 14V voltage to be lost, the D867 is switched on, the microprocessor 127 pin voltage is pulled low, the microprocessor enters the protection state.
3 line output over-voltage detection circuit
By the rectifier and filter circuit D593 (BOEAKM000058) and c591 (10 mu F/50V), sub voltage circuit R592 (11.3k omega), R591 (9.1k omega) and the detection circuit D592 MAZ4104JOF, D591 MA2C165001VT composition. On line output transformer of T551 4 fifth, winding filament voltage detection. When the output voltage is normal, the filament voltage is within the normal range, the voltage after partial pressure of D593, c591 rectifier filter and R592, R591 below regulator tube D952 regulator value, stop D952, the protection circuit does not produce effect. When the output voltage of high because of the power supply voltage, inverse process capacitor open reason and rise high, the filament voltage increased, the increased filament voltage by D593, c591 rectifier filter and R592, R591 pressure is higher than the voltage value D952 regulated, the breakdown of D952 conduction through the D591 to Q854 provides positive bias voltage. Q854 conduction, the microprocessor 127 foot voltage low, the microprocessor into protection state.