How To: How Razer Used IGZO Display Tech to Achieve 120 Hz Refresh Rates

How Razer Used IGZO Display Tech to Achieve 120 Hz Refresh Rates

With their first attempt at the mobile market, Razer introduced a device that looks at the smartphone differently. Instead of focusing on minimal bezels or an amazing camera, Razer decided to make a phone for gamers. So how could Razer target the growing mobile gaming market, which is projected to generate $40.6 billion in global revenue in 2017? It starts with the IGZO LCD Display.

IGZO is a technology Razer is familiar with. Currently, their Razer Blade and Blade Pro laptops use this tech in their displays. But unlike OLED and LCD, IGZO isn't a type of panel — instead, it is a component used by either type which improves performance. One advantage it provides is the higher refresh that has allowed Razer to create the first smartphone with a 120 Hz screen.

Background: TFT, Active Matrix & a-Si

Whether it's an LCD or OLED, a thin-film transistor (TFT) is included in almost all modern smartphone displays. TFT is one of the main components (besides a capacitor) which enables active matrix wiring on displays. You may be familiar with active matrix as the "AM" in Samsung's AMOLED panels, but it's much more than a marketing term.

Active matrix is when pixels are individually powered instead of passing current through rows (passive matrix). TFT helps achieve this by providing each pixel its own transistor, allowing every tiny dot on the screen to be driven individually. Active matrix is needed for higher resolution mobile displays, as the power consumption would be too great for a passive matrix's approach of supplying current to entire rows of pixels.

Most mobile LCDs use TFT, and all of Samsung's AMOLEDs use the technology. Pixels are arranged in rows and columns, with each pixel attached to one transistor. Typically, these transistors are created using amorphous silicon (a-Si). However, a-Si's electron mobility (how fast electrons can move through the transistors) is too slow for OLED, which also requires a higher current than what a-Si can provide. As a result, the industry moved to low-temperature polycrystalline silicon (LTPS).

The basic structure of Active Matrix displays. Image by Desault Tech/YouTube

Currently, LTPS can provide the highest current to pixels. Its higher electron mobility also allows transistors to be smaller. Smaller transistors can improve power consumption or be used for higher resolution.

However, all these advantages come at a high cost. Currently, LPTS-based TFTs are some of the most expensive TFTs available. Similar to a-Si, LPTS has a leakage problem where a portion of current is lost, requiring higher power consumption to compensate. Because of these issues, Sharp (the maker of the Razer Phone's screen) looked for a better solution for its displays, and this led to the creation of IGZO.

Enter IGZO

IGZO, or indium gallium zinc oxide, closes the gap between a-Si and LPTS. Like LPTS, it offers significant improvement over a-Si with 20-50 times the electron mobility. As with LTPS, the higher electron mobility allows for higher resolution not possible with a-Si.

Image by sharpelectronicsusa/YouTube

Unlike a-SI, IGZO transistors are transparent, which decreases the power need to illuminate the display (since less light is blocked by the transistors) and improves picture quality. Combined with its high electron mobility, IGZO TFT can result in a higher-resolution display while using a fraction of the power an equivalent a-Si or LTPS setup would need.

Higher Mobility allows for smaller transistors. Image by sharpelectronicsusa/YouTube

Electrical noise is also lower when compared to a-Si, which results in a more responsive touchscreen. This is the result of IGZO transistors creating virtually no electrical noise, which would interfere with the sensitivity of the touchscreen.

Although LPTS offers almost double the electron mobility of IGZO, where IGZO shines is its off performance. Off performance is a pixel's ability to maintain its charge while power is turned off. A TFT with poor off performance, such as an a-Si- or LPTS-based TFT, leaks current during usage, requiring current to be constantly driven to each pixel.

IGZO's low leakage allows it to turn off the power (reduce consumption) and refresh pixels at a high rate (more on that later). Instead of constantly driving power to pixels when diplaying a still image as a-Si or LPTS would require, IGZO can pulse power on and off to save energy. Leakage of power also causes flickering, so IGZO displays will appear more static or smooth when compared to a-Si or LPTS.

Power Consumption is lower on IGZO display due to low leakage. Image by sharpelectronicsusa/YouTube

The Relationship Between Frame Rates & Refresh Rates

When you watch a video, your GPU renders it and sends it to the display at a certain frame rate, with each frame representing a single still image that, when played in succession, creates the video. The display will then redraw the screen rapidly based on what information the GPU has sent.

The frame rate is how fast an image is rendered by your GPU, measured in frames per second (fps). The refresh rate represents how fast your display can redraw the entire screen, and this is measured in Hz, where one Hz equals one redraw per second. The distinction to make here is that frame rate (fps) measures your device's computing power, while refresh rate (Hz) measures your screen's speed.

If the GPU renders a video at a lower frame rate than the display's refresh rate, the monitor will repeat frames until the GPU renders new ones, improving overall smoothness of the video. For example, if the GPU outputs at 60 fps and the display refreshes at 120 Hz, the display will show each frame twice to compensate.

The higher the refresh rate is in relation to the fps, the more frames are repeated, resulting in virtually no blurring effect during motion. However, if the GPU renders video at a higher fps than the Hz of the display, the video will effectively be capped at the display's limitations.

Where IGZO's High Refresh Rates Come into Play

A while back, Hollywood decided that 24 fps was ideal for movies and TV shows, and this format is still used today. Whenever videos of this frame rate are rendered at higher refresh rates, you get what's called the "soap opera effect" where the video almost looks too smooth. Because of this fact, the majority of today's smartphone displays max out at 60 Hz. But for gamers, this isn't enough.

Modern smartphone GPUs are capable of rendering games at high frame rates, so at this point, your display's refresh rate is the main bottleneck. Some mobile games are already rendered in 120 fps at the GPU level, so a display with a matching Hz rating would provide an ideal experience. Even if most games are rendered at only 60 fps, 120 Hz would still provide a smoother experience.

A higher refresh rate even improves everyday tasks like scrolling. Image by Engadget/YouTube

IGZO's ability to maintain its charge even when off allows it to redraw images at a much higher rate than a-Si. OLED displays, which typically use LPTS TFT, require a high amount of power to achieve higher refresh rate due to leakage of current. Since mobile devices need to be power efficient, LPTS TFTs can't achieve the same refresh rates that IGZO can pull off without having a serious impact on battery life.

With the growing mobile gaming market, many analysts believe that mobile gaming will challenge (and maybe replace) traditional console gaming. However, mobile gaming will need to provide a closer experience to console (and PC) gaming than it currently does. This is why 120 Hz is so important to the smartphone industry.

Razer Phone's sucess is important to the mobile gaming industry. Image by Engadget/YouTube

Developers will have to adjust their games to take advantage. Most games are still capped at 60 fps to keep frames inline with their display's refresh rate. Razer is encouraging developers to uncap their fps, allowing the GPU to create as many frames it can possibly handle since the display can now keep up.

IGZO TFT provides a low-cost and low-power method for achieve high refresh rates in mobile displays. With its ability to maintain current, it provides a significant advantage over a-Si TFT, and its lower cost makes it an appealing option over LTPS. Due to these advantages, we now have a 120 Hz display on a smartphone.

What do you think about IGZO? Did this article make you more excited about the Razer Phone? Let us know in the comment section below.

Cover image via TechnoBuffalo/YouTube, screenshots by Jon Knight/Gadget Hacks

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