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US 2017/0249892 A1Published application
Variable VCOM Level Generator
AssigneeIML International
InventorsYoo Dong Jo, Omeshwar Suryakant Lawange
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Abstract
A variable Vcom level generator circuit generates a variable Vcom voltage level. A variable Vcom voltage can be used for variable refresh rate display technology to prevent flicker on a display panel. The Vcom level can be changed based on the vertical frequency being used or can be changed based on external control signals.
Claims20
A method comprising:
- receiving a vertical frequency signal;
- providing a reference clock at a reference frequency;
- detecting a first pulse in the vertical frequency signal;
- detecting a second pulse in the vertical frequency signal, wherein the second pulse is after the first pulse;
- upon detecting the first pulse, counting using a counter circuit, clocked by the reference clock, a number of reference clock cycles between the first pulse and the second pulse to obtain a first count value;
- based on the first count value, selecting a first register in the register block to output to a digital-to-analog converter (DAC) circuit, wherein the first register stores a first binary value;
- based on the first binary value, generating a first DAC voltage output;
- and
- based on the first DAC voltage output, generating a first VCOM voltage output level on a VCOM voltage output line.
6 more elements
A device comprising:
- a frequency detector circuit, coupled to a vertical frequency signal line of a display, wherein the frequency detector circuit comprises a counter circuit;
- a register block, coupled to frequency detector circuit, wherein the register block receives a value based on the counter circuit;
- a digital-to-analog converter circuit, coupled to the register block;
- a first operational amplifier, comprising a first input coupled to the digital-to-analog converter circuit;
- a transistor coupled to an output and a second input of the first operational amplifier;
- and
- a second operational amplifier, comprising a first input coupled to the transistor and a output coupled to a VCOM voltage output.
4 more elements
A method comprising:
- receiving a vertical frequency signal from a display panel;
- providing a reference clock at a reference frequency;
- detecting a first pulse in the vertical frequency signal;
- detecting a second pulse in the vertical frequency signal, wherein the second pulse is after the first pulse;
- upon detecting the first pulse, counting using a counter circuit, clocked by the reference clock, a number of reference clock cycles between the first pulse and the second pulse to obtain a first count value;
- based on the first count value, selecting a first register in the register block to output to a digital-to-analog converter (DAC) circuit, wherein the first register stores a first binary value;
- based on the first binary value, generating a first DAC voltage output;
- based on the first DAC voltage output, generating a first VCOM voltage output level on a VCOM voltage output line;
- detecting a third pulse in the vertical frequency signal, wherein the third pulse is after the second pulse;
- after obtaining a first count value, resetting the counter circuit;
- upon detecting the second pulse, counting using the counter circuit a number of reference clock cycles between the second pulse and the third pulse to obtain a second count value, wherein the second count value is greater than the first count value;
- based on the second count value, selecting a second register in the register block to output to the DAC circuit, wherein the second register stores a second binary value, and the second binary value is different from the first binary value;
- based on the second binary value, generating a second DAC voltage output, wherein the second DAC voltage output is different from the first DAC voltage output;
- and
- based on the second DAC voltage output, at the VCOM voltage output line, changing from the first VCOM voltage output level to a second VCOM voltage output level, wherein the second VCOM voltage output level is different from the first VCOM voltage output level.
12 more elements
Dependencies are inferred from the claim text.