Vertical Divider
Samsung’s Implementation of VRR on LTPO Panels
In a Seamless VRR display, the refresh rate is expected to change on a frame-by-frame basis as required by the system. For a 'VRR-enabled' but non-seamless display, it relies on changing the refresh rate mode between different values - the display panel will operate in either a “normal” or “high-refresh-rate” mode, but the switching between the modes is not a continuous process. For these panels, the 'range' of the refresh rates supported is fairly discrete, such as fractions of the main refresh rate, whereas a Seamless VRR display is designed to be a continuous support from a standard refresh rate to a high refresh rate with all in-between. For the most part, smartphone vendors have been playing down which one of these two they have been using, advertising both as 'variable refresh rate'. If a phone vendor has claimed to support variable refresh rate, it has been misleading, as no device until now has supported a 'seamless variable refresh rate' that switches on a per-frame basis, which is typically what we would consider a true VRR solution to be. What these companies are doing instead is that they are using refresh rate mode switching, which is a rather important distinction. Anand Technology has provided a good description of VRR and describes the two methods are known as:
Samsung with the new Note20 Ultra claims to have achieved seamless VRR, and I’ve been very curious to get my hands on a device and finally unveiling how this is implemented and if it delivers on its promises.
Figure 1: Motion Smoothness Settings
In a Seamless VRR display, the refresh rate is expected to change on a frame-by-frame basis as required by the system. For a 'VRR-enabled' but non-seamless display, it relies on changing the refresh rate mode between different values - the display panel will operate in either a “normal” or “high-refresh-rate” mode, but the switching between the modes is not a continuous process. For these panels, the 'range' of the refresh rates supported is fairly discrete, such as fractions of the main refresh rate, whereas a Seamless VRR display is designed to be a continuous support from a standard refresh rate to a high refresh rate with all in-between. For the most part, smartphone vendors have been playing down which one of these two they have been using, advertising both as 'variable refresh rate'. If a phone vendor has claimed to support variable refresh rate, it has been misleading, as no device until now has supported a 'seamless variable refresh rate' that switches on a per-frame basis, which is typically what we would consider a true VRR solution to be. What these companies are doing instead is that they are using refresh rate mode switching, which is a rather important distinction. Anand Technology has provided a good description of VRR and describes the two methods are known as:
- Seamless Variable Refresh Rate
- Refresh Rate Mode Switching
Samsung with the new Note20 Ultra claims to have achieved seamless VRR, and I’ve been very curious to get my hands on a device and finally unveiling how this is implemented and if it delivers on its promises.
Figure 1: Motion Smoothness Settings
The first thing noticeable on the Note20 Ultra, compared to an S20 device, is that its high-refresh-rate mode is called “Adaptive” rather than “High”. The description is specific in that it now states the refresh rate will go “up to” 120Hz instead of outright stating 120Hz on the S20 series devices.
Samsung’s doesn’t advertise refresh rate modes from 1Hz to 120Hz and the phone features the same resolution and refresh rate modes that were also available on the S20 series, meaning 48 Hz, 60 Hz, 96 Hz, and 120 Hz. While browsing on a webpage a high refresh rate would be expected when scrolling, and a lower fresh rate when idle, and a smooth seamless transition between the two. The system switches to 120Hz refresh rate, but four seconds later it switched back to a 60Hz mode, which is not expected from a seamless VRR implementation – the preset refresh rate modes appear to be baked into the operating system and integrated with user interactions.
The panel uses Low Temperature Polycrystalline Silicon that they claim allows for faster switching transistors, also lowering power consumption. Samsung’s key feature in achieving lower refresh-rate seems to be dubbed “LFD” or low-frequency-drive. LFD seems to be something that solely works at the panel and display driver (DDIC) level. The LFD operating modes are programmed to work with Samsung’s low operating frequencies, all the way down to 1Hz. The low frequency driver operation also seems to be a sub-mode underneath the higher level VRR operating modes, with these being the actual modes that the phone switches between in a finer manner using the MIPI-DSI interface.
When displaying a pure black static image in the phone’s Gallery app, there is a drastic change in power consumption between when the phone is in a brighter environment compared to when the light sensor is covered because the device actively tracks the light sensor values all the time, even when in manual brightness, and enters a special mode when it senses a darker environment. Whenever the phone senses an ambient brightness level below 40 lux, it forces the phone to operate only in its 120Hz modes, with an additional flag that also sets the minimum refresh rate to 120Hz. By contrast, in a higher brightness setting, the “normal” operating mode has what looks to be a minimum of 48Hz. This cause the display to be sensitive to time of day and the ambient conditions will now affect the power consumption of the display hone. Samsung’s new VRR/LFD benefits. Are shown in the next chart.
Figure 2: Device-on Black Screen Power Consumption (Airplane Mode)
Samsung’s doesn’t advertise refresh rate modes from 1Hz to 120Hz and the phone features the same resolution and refresh rate modes that were also available on the S20 series, meaning 48 Hz, 60 Hz, 96 Hz, and 120 Hz. While browsing on a webpage a high refresh rate would be expected when scrolling, and a lower fresh rate when idle, and a smooth seamless transition between the two. The system switches to 120Hz refresh rate, but four seconds later it switched back to a 60Hz mode, which is not expected from a seamless VRR implementation – the preset refresh rate modes appear to be baked into the operating system and integrated with user interactions.
The panel uses Low Temperature Polycrystalline Silicon that they claim allows for faster switching transistors, also lowering power consumption. Samsung’s key feature in achieving lower refresh-rate seems to be dubbed “LFD” or low-frequency-drive. LFD seems to be something that solely works at the panel and display driver (DDIC) level. The LFD operating modes are programmed to work with Samsung’s low operating frequencies, all the way down to 1Hz. The low frequency driver operation also seems to be a sub-mode underneath the higher level VRR operating modes, with these being the actual modes that the phone switches between in a finer manner using the MIPI-DSI interface.
When displaying a pure black static image in the phone’s Gallery app, there is a drastic change in power consumption between when the phone is in a brighter environment compared to when the light sensor is covered because the device actively tracks the light sensor values all the time, even when in manual brightness, and enters a special mode when it senses a darker environment. Whenever the phone senses an ambient brightness level below 40 lux, it forces the phone to operate only in its 120Hz modes, with an additional flag that also sets the minimum refresh rate to 120Hz. By contrast, in a higher brightness setting, the “normal” operating mode has what looks to be a minimum of 48Hz. This cause the display to be sensitive to time of day and the ambient conditions will now affect the power consumption of the display hone. Samsung’s new VRR/LFD benefits. Are shown in the next chart.
Figure 2: Device-on Black Screen Power Consumption (Airplane Mode)
When in a dark environment, and forced into the 120Hz mode, the Note20 Ultra’s power consumption isn’t all that different from the S20, creating a large ~180mW power penalty that is present at all times, even on a black static screen, because of 120 Hz. That penalty comes from the measured power, with 640 mW and 465 mW in the respective 120 and 60Hz modes. Under a little brighter ambient conditions, the panel showcases its technology advantages, and power consumption drops drastically. In the 120Hz mode but with the minimum refresh rate now in the regular '48 Hz' setting, the power figure drops from 640mW to 428mW, which is a massive 220mW drop. The 60Hz mode also sees a power benefit, as power consumption drops from 465 to 406 mW, indicating that LFD is working in the background and reducing the panel’s refresh rate to below 60Hz – although we have no way to accurately measure exactly how low it goes.
The phone operating under dark conditions seems to disable the 'seamless' variable refresh rate display, that allows the phone to go into lower frequency modes, but not in all circumstances. The device reverts into a low refresh rate as long as the on-screen content and brightness exceeds a certain level, even if the light sensor measures 0lux. However, it relies on the screen content too, which affects the screen brightness, as the phone will also jump between switching back into low-frequency mode or staying at a more power hungry high-frequency mode. In that instance, the refresh rate mechanism is based on the average picture level (APL) as well.
There seems to be four corners to the battery life on the new S20 Ultra:
- Set at 120 Hz in user options, low ambient brightness (low lux)
- Set at 120 Hz in user options, high ambient brightness (high lux)
- Set at 60 Hz in user options low ambient brightness (low lux)
- Set at 60 Hz in user options, high ambient brightness (high lux)
Each variant, due to Samsung's seamless VRR implementation (which is only seamless in high brightness and/or bright content), gives a different level of battery life. It is worth nothing that the Note20 Ultra has a 10% smaller battery than the S20 Ultra, as well as a different processor - the new Snapdragon 865+ in the Note20 Ultra is more power hungry and less efficient than the regular Snapdragon 865 in the S20 Ultra.
Figure 3: Battery Life (hrs.)
When it comes to the difference in the battery runtimes between running the phone in a dark or a bright environment, there are somewhat small difference. In the 60Hz maximum refresh mode, VRR/LFD gains the phone an additional 4% of battery life. In the 120Hz mode, we see a larger 8.5% jump in runtime.
Figure 4: Power Draw Graph in Pcmark In The 120Hz Modes
Figure 4: Power Draw Graph in Pcmark In The 120Hz Modes
Looking at the power draw graph in PCMark in the 120Hz modes, there is a drop in power from an average of 1.937W to 1.796W at 200cd/m² screen brightness and no material difference during the video editing section of PCMark, with the power results been the two modes falling within 21mW. What this points out to is that in more regular non-video content the battery life gains could be larger than what’s experienced here in this battery test.