Newer LCDs can refresh the screen at 120Hz or higher. The driver circuitry for the panel is responsible for pushing frames to the panel at a given rate, but are there any particulars of the LCD panel itself that factor into achieving the higher refresh rate? Are there, for instance, any special materials, construction, or circuitry of the panel needed to correctly respond to a higher refresh rate? In other words, is it theoretically possible to drive a panel over its specified refresh rate using another driver board, assuming all interfacing requirements are identical?
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\$\begingroup\$ As far as I know LCDs are refreshed in the 60 Hz to a couple of hundred hertz frame rate - enough to give a flicker-free image. Are you thinking of the display multiplexing circuitry or the data transmission to the display such as HDMI? Please clarify in your question rather than in the comments. \$\endgroup\$– TransistorJan 27, 2021 at 0:52
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\$\begingroup\$ Hmmm. So there's more circuitry in the LCD? \$\endgroup\$– user148298Jan 27, 2021 at 0:53
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\$\begingroup\$ Is it clearer now? \$\endgroup\$– user148298Jan 27, 2021 at 0:55
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\$\begingroup\$ No. LCDs are used in everything from digital thermometers to large screen displays. It's not clear what you are talking about, where the frame buffer is in your scheme of things, where the 120 MHz is and why you are asking. Why have you got the question tagged "led-driver"? What do you hope to achieve by driving an LCD beyond its ratings? \$\endgroup\$– TransistorJan 27, 2021 at 0:58
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1\$\begingroup\$ I think he's asking for instance with two similar size monitors, one a standard 60hz, and one a high performance 144hz gaming monitor, whether the physical LCD/OLED/whatever panel is superior in some necessary way on the 144hz gaming monitor, or if it is mechanically the same and driven in a superior way. \$\endgroup\$– K HJan 27, 2021 at 1:12
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1 Answer
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The driver circuitry for the panel is responsible for pushing frames to the panel at a given rate, but are there any particulars of the LCD panel itself that factor into achieving the higher refresh rate?
Since the panels are big 2D arrays of pixels addressed similarly to a DRAM cell, the LCD itself must be able to clock at the pixel rate you're driving. If its internal capacitances are too large or its transistors too slow, there won't be time for the pixel to update before the next value is driven into the array.
In addition, since the pixel array is essentially an optical digital to analog converter, there are also sampling rate concerns. Driving the array at a higher pixel rate is equivalent to increasing the temporal sampling rate driving each pixel. Increasing the update rate while keeping the analog impulse response of each pixel unchanged is equivalent to increasing the sampling rate of a DAC without also adjusting the analog bandwidth of the electronics it is driving. Eventually your analog bandwidth falls far enough below the Nyquist (folding) frequency that although you are updating the pixels more frequently, no new information is actually being modulated onto the pixel output because it simply cannot respond faster (even if the array itself can physically sustain the pixel rate).
So yes, there are two factors. The array must be able to shift values at the pixel rate you've selected and the pixels themselves must be fast enough (have sufficient bandwidth) that the faster refresh rate actually does something.
In other words, is it theoretically possible to drive a panel over its specified refresh rate using another driver board, assuming all interfacing requirements are identical?
Yes, and you do occasionally see manufacturers offering displays at refresh rates above the nominal spec value for the panel they are using.
answered Jan 27, 2021 at 2:39
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\$\begingroup\$ You answer is inline with what I am thinking. Your last response is especially insightful. Assuming two identical panels with different spec values are being manufactured around the same time, it really makes little sense to have two different BOMs. The economies of scale gained in consolidating materials usually far exceeds the trivial savings gained from using slower device A over faster device B. The exception is Apple who doesn't mind paying up just to change it up. \$\endgroup\$ Jan 27, 2021 at 3:02