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LG's new 1Hz display is the secret behind a new laptop's battery life

pcworld.com

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Re: LG's new 1Hz display is the secret behind a new laptop's battery life

#171

Post by alok-g »

mmooss wrote: post #167
alok-g wrote: post #87

Earlier quoted context omitted.

I used to be a display architect about 15 years back (for Qualcomm mirasol, et al), so my knowledge of the specifics / numbers is outdated. Sharing what I know. High pixel density displays have disproportionately higher display refresh power (not just proportional to the total number of pixels as the column lines capacitances need to be driven again for writing each row of pixels). This was an important concern as hi…

> the column lines capacitances need to be driven again for writing each row of pixels Not my field so please forgive a possibly obvious question: That seems true regardless of the pixel count (?), so for that process why wouldn't power also be proportional to the pixel count? I notice I'm saying 'pixel count' and you are saying 'pixel density'; does it have something to do with their proximity to each other?

Total column line capacitance is impacted by the number of pixels hanging onto it as each transistor (going to the pixel capacitance) adds some parasitic capacitance of its own. Hope that answers your question. You are right in the sense that a part of the total column capacitance would depend on just the length and width of it, irrespective of the number of pixels hanging onto it.

I had back then developed what was perhaps the most sophisticated system-level model for display power, including refresh, illumination, etc., and it included all those terms for capacitance, a simplified transistor model, pixel model, etc.

I did not carefully distinguish pixel density vs. pixel count while writing my previous comments here, just to keep it simple. You can perhaps imagine that increasing display size without changing pixel count can lead to higher active pixel area percentage, which in turn would lead to better light generation/transmission/reflection efficiency. There are multiple initially counter-intuitive couplings like that. So it ultimately comes down to mathematical modeling, and the scaling laws / derivatives depend on the actual numbers chosen.

Addition:

Another important point -- Column line capacitances do not necessarily need full refresh going from one row of the pixels to the next, as the image would typically have vertical correlations. Not mentioning this is another simplification I made in my previous comments. My detailed power model included this as well -- so it could calculate energy spent for writing a specific image, a random image, a statistically typical image, etc.

Re: LG's new 1Hz display is the secret behind a new laptop's battery life

#172

Post by [deleted] »

saltcured wrote: post #159
alok-g wrote: post #150

Earlier quoted context omitted.

Being a key technology architect for it (not the core inventor), I know all about it, and then some more! I cannot however talk publicly about it. :-( It has been a disappointment for me as well. I had worked on it for nearly eight years. The idea was so interesting--using thin-film interference for creating images is akin to shaping Newton's rings into arbitrary images, something which even Newton would not have ima…

My fantasy display would be some kind of reflective-mode display that can passively show static images like e-ink, have partial updates like MIP LCD in wearables, response times like modern LCD and AMOLED, and "super-real" contrast/gain. I.e. actually do wavelength conversion to not just reflect a narrow-pass filtered version of the ambient light, but convert that broad spectrum energy into the desired visuals, so it…

[deleted]

Re: LG's new 1Hz display is the secret behind a new laptop's battery life

#173

Post by alok-g »

saltcured wrote: post #170
alok-g wrote: post #161

Earlier quoted context omitted.

>> My fantasy display would be some kind of reflective-mode display that can passively show static images like e-ink, have partial updates like MIP LCD in wearables, response times like modern LCD and AMOLED, and "super-real" contrast/gain. What about cost? :-) It is an important factor too outside of the fantasy world and can kill new display technologies. The latter often suffer from yield issues (dead pixels, etc.…

Well, the reflectivity of color MIP LCD is not very satisfactory. It is barely adequate, even for people like me who are fans. This is both because of the narrow-band RGB filtering and the inherent losses of the polarization-based switching method. Even the "white" state is discarding most polarizations of the ambient light, and then the darker colors are even blocking that. My fantasy is having the reflectivity be a…

>> Well, the reflectivity of color MIP LCD is not very satisfactory. It is barely adequate, even for people like me who are fans. This is both because of the narrow-band RGB filtering and the inherent losses of the polarization-based switching method. Even the "white" state is discarding most polarizations of the ambient light, and then the darker colors are even blocking that.

Yes, that's right. A typical color LCD transmits only about 5-10% of the light for white because of all those factors.

>> My fantasy is having the reflectivity be at least as good as good white paper, and with deep contrast too.

That exactly was our benchmark for mirasol development. We used to measure best-in-class color prints for color gamut, brightness, contrast, etc.

mirasol did not use polarizers or RGB filters. An advanced architecture (that I was leading) also avoided RGB subpixels, something which very few alternative technologies can do [1].

>> It also needs to be brighter in practice than normal objects because, no matter what, it will have to overcome some glare from whatever protective glass and touch sensing layers there are over the actual display.

Yes.

Integrated touch-sensing helps significantly though.

There are also optical means that can nearly get rid of glare, if cost were not an issue. I have seen demo coatings that make the glass practically disappear -- we would repeatedly walk into it if it were used on a glass door.

-------

[1] Liquavista had Cyan-Magenta-Yellow subpixels vertically stacked. A new Eink architecture uses multiple colored pigments within the same cell but now needs sophisticated mechanisms to control them independently.

Re: LG's new 1Hz display is the secret behind a new laptop's battery life

#174

Post by DoctorOetker »

amelius wrote: post #134
DoctorOetker wrote: post #74

Earlier quoted context omitted.

I don't believe LED-pixel displays use PWM. I would expect them to use bit planes: for each pixel transform the gamma-compressed intensity to the linear photon-proportional domain. Represent the linear intensity as a binary number. Start with the most significant bit, and all pixels with that bit get a current pulse, then for the next bitplane all the pixels having the 2nd bit set are turned on with half that current…

So for an 8bit color display you have 24 lines of various currents going across each row (or column) of pixels?

There are more efficient ways of achieving this, but you certainly don't need a separate conductor for each bitplane, but obviously you need separate strings for each color channel.

So to ignore the colorwise overhead lets pretend we just have a single color channel.

You could even arrange all LED's in series and short out (bypass with mosfet) those LED's that should NOT be lit.

Then you can just energize an inductor until the appropriate current is reached and then flash a certain amount of charge through the LED string.

One can choose between reusing the same inductor for the different currents or having separate inductors each for their own current levels.

It would require bypass transistors for each LED, but there are support electronics for each LCD pixel too, as a comparison.

The 24-bit color display (3x8) would actually result in many more bit planes after gamma deflating to the linear photon proportional domain.

Re: LG's new 1Hz display is the secret behind a new laptop's battery life

#175

Post by kinematikk »

elif wrote: post #157
qnleigh wrote: post #32

> That will help save enormous amounts of power: up to 48 percent on a single charge, Why does refresh rate have such a large impact on power consumption? I understand that the control electronics are 60x more active at 60 Hz than 1 Hz, but shouldn't the light emission itself be the dominant source of power consumption by far?

Your GPU rendering 1 frame vs your GPU rendering 60 frames.

In cases where 1hz mode is feasable the gpu doesn't render 60 fps anyways

Re: LG's new 1Hz display is the secret behind a new laptop's battery life

#176

Post by mmooss »

alok-g wrote: post #171
mmooss wrote: post #167

Earlier quoted context omitted.

> the column lines capacitances need to be driven again for writing each row of pixels Not my field so please forgive a possibly obvious question: That seems true regardless of the pixel count (?), so for that process why wouldn't power also be proportional to the pixel count? I notice I'm saying 'pixel count' and you are saying 'pixel density'; does it have something to do with their proximity to each other?

Total column line capacitance is impacted by the number of pixels hanging onto it as each transistor (going to the pixel capacitance) adds some parasitic capacitance of its own. Hope that answers your question. You are right in the sense that a part of the total column capacitance would depend on just the length and width of it, irrespective of the number of pixels hanging onto it. I had back then developed what was…

Thanks. It's always interesting what the actual issues and engineering look like.

Re: LG's new 1Hz display is the secret behind a new laptop's battery life

#177

Post by londons_explore »

iAMkenough wrote: post #164
mnw21cam wrote: post #115

Earlier quoted context omitted.

It's an LCD display.

Are you sure? Article says: > A 1Hz panel is almost, but not quite, on the level of an e-ink panel, which isn’t the prettiest to look at. LG’s panel also uses LED technology, the mainstream panel technology that’s being overtaken at the high end by OLED panels with essentially perfect contrast.

Led backlight I assume.

Re: LG's new 1Hz display is the secret behind a new laptop's battery life

#179

Post by iknowstuff »

quantumink wrote: post #168
iknowstuff wrote: post #112

Earlier quoted context omitted.

Powerbanks fill that role well. We have USB-C PD now

While I concede that powerbanks may satisfy the proximal problem - literally making charging available on demand... Consider that it does not in any way resolve the distal problem of having a 'portable computing device', which heavily compromises on the 'portable' aspect - by forcing a state of permanent battery anxiety without external life support (i.e. no power source - dead in minutes of intensive work) The power…

Maybe like 0.01% of users ever did that, or did any upgrades to their laptops. Moving to recyclable but integrated components is the right move for the vast majority of people. I’m sure there are some compromised devices for nerds out there that still allow for swapping batteries etc

Re: LG's new 1Hz display is the secret behind a new laptop's battery life

#180

Post by saltcured »

alok-g wrote: post #171
mmooss wrote: post #167

Earlier quoted context omitted.

> the column lines capacitances need to be driven again for writing each row of pixels Not my field so please forgive a possibly obvious question: That seems true regardless of the pixel count (?), so for that process why wouldn't power also be proportional to the pixel count? I notice I'm saying 'pixel count' and you are saying 'pixel density'; does it have something to do with their proximity to each other?

Total column line capacitance is impacted by the number of pixels hanging onto it as each transistor (going to the pixel capacitance) adds some parasitic capacitance of its own. Hope that answers your question. You are right in the sense that a part of the total column capacitance would depend on just the length and width of it, irrespective of the number of pixels hanging onto it. I had back then developed what was…

Hmm, are you saying that LCD (without memory-in-pixel) could have enough persistence to hold a (well disciplined) image without a constant, high-frequency driver? I was under the impression that the partial crystal alignments needed for modern color gamuts require constant, dynamic control.

Am I mistaken? Is it feasible that there could be (analog?) charge memory to hold each sub-pixel at a stable partial alignment, without the high-frequency driver signals being reasserted?

I have understood the reason MIP LCD works is that there is a RAM bit embedded in each sub-pixel, so it can locally maintain a static, binary charge state without dynamic refresh. There is no high-frequency oscillating circuit to provide this persistence. The only way I could see this work for increased color depths would be if there were a recursive hierarchy of sub-pixels, each with that 1-bit state. E.g. a series of 1/2, 1/4, 1/8, ... area sub-pixels could encode a linear color space, with all the emission areas adding together to physically embody the DAC.

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