Color display power supply characteristics and maintenance - Power Circuit - Circuit Diagram

2) The filament voltage of a color TV is typically supplied by the line output transformer (AC), whereas the filament voltage of a color display is directly provided by the switching power supply (DC at 6.3V). A color display uses this power supply method primarily to meet its energy-saving requirements. For instance, when a computer remains unattended for a certain period, the color display enters an energy-saving mode. During this state, the field scanning stops, and the entire system consumes significantly less power. However, the filament remains heated, and once someone interacts with the computer, the color display instantly switches back to the active operational state. 3) The output level power supply of a color TV generally operates around 110V and is fixed, while the output voltage of the color TV's line output stage typically ranges from 45V to 135V, which is usually variable. This difference arises because the scanning frequency of a color TV is fixed, whereas modern SVGA color displays have multiple scanning modes, with varying scanning frequencies depending on the mode. For example, the line frequency for screens under 15 inches might range from 30 to 54 kHz, while larger screens have an even broader range. To ensure proper line scan amplitude and reverse pulse amplitude (adequate high voltage) across different scan modes, the line power voltage of the color display adjusts according to the line scan frequency—higher line frequencies result in higher voltages. Standard switching power supplies provide fixed outputs, such as 45V and 150V, which are then regulated further to produce 45V to 135V. For the raw pressure type, the 45V output is double-regulated, while the 150V output is regulated to yield 45V to 135V for the step-down type. Due to these power supply circuits, the main fault symptoms include the absence of a raster or raster anomalies. 1) The first step in troubleshooting involves observing the power indicator light and checking whether the picture tube filament’s light is normal to determine if the switching power supply is functioning correctly. If not, either the power supply itself is faulty or there’s a short circuit in the load. If the light is normal, proceed to test the output voltage of each group of the switching power supply. The primary judgment criterion is the accuracy of the 12V output. If 12V is correct, the switching power supply itself is likely fine. 2) Assuming the switching power supply is functioning properly, potential causes for the absence of a raster include: First, an issue in the line scan circuit or picture tube circuit, similar to traditional TVs; second, an abnormality in the secondary switching power supply, which can be verified by checking the line output transformer’s power supply voltage; third, a malfunction in the energy-saving circuit or pattern recognition circuit, which could prevent the secondary switching power supply from operating. Note that some color displays require connection to the host to start up. When offline, the energy-saving circuit automatically shuts down the line scan due to the lack of a synchronization signal. 3) Raster anomalies primarily occur when the width is excessively wide or narrow, and the width adjustment knob cannot normalize the amplitude. These faults are often caused by abnormal line voltage, issues in the line pulse amplitude sampling circuit, or problems in the line power secondary buck circuit. Additionally, line amplitude anomalies can arise in the circuitry involving the reverse circuit capacitor and the S-circuit positive capacitance automatic adjustment circuit. The troubleshooting methods for field amplitude anomalies are similar to those for traditional TVs. In conclusion, maintaining the health of the switching power supply and ensuring the stability of its output voltages are crucial for preventing raster issues in color displays. Proper diagnostics and adjustments are essential for addressing these problems effectively.

Single Phase Ammeter

Single Phase Ammeter,Energy Meter,Digital Energy Monitor,Led Ammeter

zhejiangjinyidianqiyouxiangongsi , https://www.jooeei.com