When purchasing an LED screen, you may have to make a decision on which scan mode to choose. It affects the screen’s performance, and may even impact your ROI. Are you not clear about the differences among various scans and how to choose the right one? This article will tell you the answer.
What is LED Scan Mode?
The number of pixels in an LED display is very large, so the control system usually cannot drive all LEDs at the same time. Therefore, LED displays generally show images by lighting up rows in batches, rapidly in sequence.
The scanning speed of the screen is very fast, so your eyes cannot perceive these momentary changes, but they can integrate the fragmented images into a complete picture.
The LED scan mode describes how many rows of the screen are lit at the same time. For example, a 1/4 scan means 4 rows of LEDs will be lit at a time. If there are 16 rows of LEDs, the screen needs to scan four times to display one frame.
The Impact of LED Scan Mode on Display Performance
Brightness
The brightness of an LED display is determined not only by the LED chips but also by the scan ratio. When the number of light bulbs scanned each time is smaller, the on-time of each row of LEDs becomes shorter. As a result, the screen brightness will also decrease. Conversely, the more LEDs lit in each scan, the brighter the screen will be.
Visual Quality
When you use high scanning rates such as 1/16 or 1/32, the lighting time for each row of LEDs will be shorter. This will cause the PWM period to be compressed, and bring out insufficient grayscale bits, brightness uniformity, and even blurring and ghosting. If you use a lower scan ratio, these issues will improve.
Screen Cost
If you expect a low scan ratio, such as 1/4 or even 1/2, the driver IC will need to light more rows each time. This requires more driver IC channels. Accordingly, the screen cost will be higher. At the same time, the PCB design costs, power supply costs, and the heat dissipation costs will also increase accordingly.
Refresh Rate
The lower the scan ratio, the easier it is to achieve a high refresh rate: When the driver IC lights up more LED rows at a time, the screen shows each frame more efficiently. Therefore, it is easier to maintain a high refresh rate, like 3840Hz. Conversely, when the driver IC lights up only a few LEDs at a time, maintaining a high refresh rate will become difficult.
Screen’s Lifespan
Due to the high scan ratio, each time only a few lines can be illuminated. To ensure a higher brightness, the driver IC needs to increase the instantaneous current. This may cause the temperature of the LED to rise, thereby accelerating the LED light decay.
Indoor P2.5 SMD2121 1/32 Scan LED Display Module For LED Video Wall(YouTube link: https://www.youtube.com/watch?v=wSqmJmGZGUY)
Comparison of Common Scan Modes
1/4 Scan
1/4 scan means that the screen lights up 1/4 of the total rows at a time. That is to say, if the screen has N rows of LEDs in total, then each scan lights up N ÷ 4 rows at a time. The screens with 1/4 scan perform very well in brightness, grayscale, refresh rate, and lifespan, but their design and manufacturing costs are higher.
1/8 Scan
With a 1/8 scan, the screen lights up 1/8 LEDs at a time. In other words, the screen needs to output one frame of picture by scanning 8 times. 1/8 scan performs slightly worse than 1/4 scan in brightness, color, and other aspects, but it still delivers good performance.
1/16 Scan
Similarly, the 1/16 scan refers to the screen scanning 1/16 of the total number of rows each time. The screens with 1/16 scan has everage perform in brightness and refresh rate, which is a cost-effective choice. It is suitable for most indoor LED screens.
1/32 Scan
Compared with other scan modes, the 1/32 scan has lower brightness and weaker image performance. However, when using 1/32 scanning, the driver IC only needs to control very few channels. Also, the requirements for the cooling system and circuit design are very low. It is very suitable for large advertising screens and other display projects with limited revenue potential.
Other Less Common Scan Modes
Among these scan modes, there are also many compromise options or more advanced choices. When none of the four types above meet your project requirements, you can consider special scan modes. They mainly include:
- Low-ratio scans, such as 1/2 and 1/3.
- Non-integer fraction scans, such as 1/5, 1/6, or 7/64.
- Static drive: all the rows will be lit each time.
How to Choose the Right LED Scan Mode for Your Project?
Based on the Application Scenario
Different screen types and applications require different scan modes. For example, giant outdoor screens need to consider the payback period and ROI, so the 1/32 scan is already sufficient; For small-pitch indoor screens, 1/2, 1/3, 1/4 scan or static drive is recommended.
Based on the Performance Indicators You Require
If your screen does not require high grayscale and is mostly viewed from a distance, the low scan is somewhat wasteful, and the high scan may be suitable.
However, if you have the need for shooting or live streaming, regardless of whether you need outstanding performance, you’d better choose a low scan ratio, like1/2 or 1/4 scan.
Based on Your Budget
It is worth noting that when you choose different scanning methods, the costs of other aspects, like the screen’s driver IC, PCB, power supply, heat dissipation, and maintenance, will also change accordingly. You need to carefully predict its future revenue and select a reasonable solution.
FAQS
Does a Lower Scan Mode Increase Power Consumption?
It depends. The total power consumption depends on brightness, power, and other factors. Low-scan modes need higher peak current, but the PWM duty cycle will be shorter. Therefore, the average power consumption of a low-scan screen may be close to that of a high-scan screen.
What is the Relationship Between Scan Mode and PWM Dimming?
PWM refers to achieving different grayscale levels by rapidly switching the LED bulbs. The scan ratio affects the PWM dimming: The lower the scan ratio, the easier it is for PWM dimming to achieve high grayscale; the higher the scan ratio, the more limited the PWM dimming capability.
Is a Lower Scan Mode, Like 1/4, Always Better?
Low scan ratios often have greater advantages in image performance, such as higher brightness, higher refresh rate, and better grayscale. However, this also means the screen has a more complex structure and a higher cost. When the screen fails, repair and replacement costs may both be higher.
Final Thoughts
The scan mode is an important parameter for the screen, but it is often ignored. You need to pay attention to it and choose carefully when purchasing a screen.
If you are looking for a reliable solution, JINGYLED will definitely be a good choice. Contact us to get the optimal solution.
