Functions of AVDD STV VGL VCOM VGH

What are AVDD, STV, VGH, VCOM, VGL, and CKV, and what are their functions? To understand these things, you need to know some basics of LCD panels first. We try to understand those aspects of the LCD panel. A tiny liquid crystal cell is below the RGB subpixels of the LCD panel and above the backlight (Look at the diagram).

When these crystal cells are energized, the molecular position of the Liquid crystal changes, and when De-energized, the molecules return to their normal orientation. During this process, the crystal cells act as a light barrier. When the crystal cells become entirely black, the backlight's light cannot reach the bottom of the pixels. Thus, the liquid crystals block the light waves and control the brightness of the pixels by opening the light path as needed.

This liquid crystal cell has two electrodes, one of which supplies a negative voltage VCOM, the positive voltage is provided to the other terminal by the source terminal of the thin film transistor (TFT), and the AVDD voltage is supplied to the drain of this TFT. Moreover, VGH or VGL voltage is provided to the gate terminal of the TFT at a specific time to make each TFT active, semi-active, inactive, etc.

What is AVDD, & what is its function in LCD and LED Display

AVDD stands for Analog Voltage for Drain-to-Drain, which some call an Analog power supply. Other names of AVDD are VDDA, HVAA, VSA. Each subpixel of the LCD receives a polarized light wave from the backlight, and there is a liquid crystal cell between the backlight and the subpixel to control the polarized light.

What is VGH, STV, AVDD, VGL, VCOM in LCD or LED TV or Monitor

To control the brightness of the sub-pixels according to the screen image, it is necessary to supply variable voltage to the two electrodes of this liquid crystal cell. A negative voltage is supplied to one electrode of the liquid crystal cell, and a positive voltage is provided to the other electrode by the source terminal of a thin film transistor. AVDD is supplied to the drain terminal of that TFT.

What is VGH in LCD, and what is its function?

The VGH is the acronym for Voltage High Gate, which is the boost voltage generated from the DC-to-DC converter. Its other name is VON / VGON/ VDDG. The VGH circuit in LCD has 20V to 33V and requires a 50mA current. An LCD panel comprises liquid crystal cells associated with thin-film transistors (TFTs).

These TFTs are responsible for adequately controlling the activity of the liquid crystal cells. To operate the TFT, a reverse bias voltage is applied to its gate terminal through gate COF; the source of that reverse bias voltage is VGH or High Gate Voltage.

What is VGL, and what is its function?

The complete form of VGL is a voltage high gate, which is the minus voltage generated by the DC-to-DC buck converter. Other names for VGL are VOFF, VGOFF, and VEEG. The voltage range of VGL is -5 volts to -10 volts, and the current is 100mA.

In an LCD (Liquid Crystal Display) panel, VGL, which stands for "Voltage Gate Low," is a voltage used to control the operation of thin-film transistors (TFTs) on the display. The TFTs are an essential component of an LCD panel as they act as individual pixel switches, allowing or blocking the passage of light through each pixel. VGL is responsible for controlling the "gate" of these transistors.

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What is VCOM, and what is its function in LCD/LED Display?

VCOM is the Common reference voltage for each sub-pixel of the LCD panel. A tiny liquid crystal cell is placed under each subpixel to make the pixels of the LCD panel active or bright and dim. The number of these liquid crystal cells is several billion in an LCD.

Each liquid crystal cell has two electrodes; if we call one of these electrodes a cathode and the other an anode, positive voltage is supplied to the anode, and negative voltage is provided to the cathode. In this case, the cathodes of all the crystal cells of the LCD are connected by a conductive print, and a negative voltage is supplied.

Then, indeed, we understood that the cathode terminals of the liquid crystal cell are marked as Common. VCOM, or Common voltage, is applied to these Common terminals. VCOM stands for Common Voltage, through which liquid crystal cells receive negative voltage.

What is STV in the concept of LCD?

STV is a Vertical Sync Input pulse. It determines the time to produce the next frame after a one-frame scan to make the image. When the rising edge of STV occurs, it marks the beginning of a data frame. The STV input is also used to generate the high-voltage STV or Start Pulse Output.

This high-voltage output is low (connected to VGL) whenever STV is low, and it becomes high (connected to VGH) only when STV is high and both CPV and OE are low.
What is CKV, and what is its function? Click here