Green synchronous signal detection circuit

Abstract

A sync-on-green (SOG) signal detection circuit includes: a clamping circuit, which clamps the voltage of a video graphic signal to a preset range and then outputs a clamped input signal; a first programmable gain amplifier, which receives the Clamping the input signal and amplifying its amplitude to a first gain value to generate a first gain signal; a first low-pass filter to generate a first filter signal after receiving the first gain signal; a second programmable gain amplifier, receiving the clamped input signal and amplifying its amplitude by a second gain value to generate a second gain signal, wherein the second gain value is different from the first gain value; a second low-pass filter, after receiving the second gain signal A second filter signal is generated; a programmable voltage offset unit receives the first filter signal and adjusts its DC level, and outputs a level offset signal; a comparator receives the level offset signal and the second filter signal A comparison signal is generated as a SOG signal.

Description

technical field [0001] The invention relates to a Sync On Green (SOG, Sync On Green) signal detection circuit, in particular to a SOG signal detection circuit which utilizes a programmable gain amplifier and a low-pass filter (PGA / LPF) to improve anti-noise interference. Background technique [0002] Figure 1A It is a schematic diagram of a general video graphics signal (Video graphics signal). Such as Figure 1A As shown, the video graphic signal includes three parts: a synchronous signal A1, a blank area A2, and a data area A3. According to the specification, about 300mV is between the synchronization signal A1 and the blank area A2; and about 700mV is between the blank area A2 and the data area A3. Video display devices generally use a SOG signal detection circuit to detect the synchronous signal A1 as a display control parameter. [0003] Figure 1B It is a known SOG signal detection circuit. Such as Figure 1B As shown, the SOG signal detection circuit 10 includes...

AI Technical Summary

Problems solved by technology

Although the SOG signal detection circuit 20 can use the control unit 24 to adjust the comparison voltage generated by the trigger level generation circuit 22 according to the SOG signal, because there is only about 300mV between the synchronization signal A1 of the video graphic signal and the blank area A2, the noise The boundary value is still small, and the effect of anti-noise interference is not good

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