What are The LED Display Scan Modes and Driving Principles?

Since LED technology’s continued advances, brightness of LED displays has steadily been rising while their size continues to shrink – an indicator that more electronic LED displays will enter indoor application as their luminosity and density rise. Unfortunately, higher brightness levels create new and elevated requirements when controlling and driving LED screens; currently these typically utilize row-column separation known as scanning mode while LED displays operate either static or dynamic scanning modes that further real pixels, virtual pixels and real/virtual pixel areas respectively.

Scan Mode Definition:

A scan mode of LED screen can be defined as the ratio between simultaneously illuminated rows and total rows in a display area. Indoor monochrome or dual-color LED displays usually feature 1/16 scan ratio while 1/8 scanning may also be employed when used indoor full color displays. Outdoor monochrome dual color and full color LED displays commonly use 1/4 scan ratio while static scanning techniques.

LED display scan mode

Drive Mode Definition:

A drive mode refers to the method by which output pins of driver IC connect with individual pixels points. Static drive, using point-to-point control, offers superior display quality and stability with minimal brightness loss while scanning drive using row control circuit is more cost-effective but results in reduced display quality and greater brightness loss.

LED Electronic Display 1/4 Scan Mode Working Principle:

When operating in this mode, each of V1-V4 rows of power supply (V1-V4) are activated according to control requirements for 1/4 of frame time in one frame time – this approach maximizes efficiency of use of display characteristics while decreasing hardware costs; but, unfortunately this limit means each LED row may only display for 1/4 time within a frame period.

Scan Modes for Different LED Display Types:

Indoor full-color LED display scan modes:

P4 and P5 use constant current 1/16 scan, while P6 and P7.62 utilize constant current 1/8 scan.

Outdoor full-color LED display scanning modes:

P10 and P12 utilize constant current 1/2 and 1/4 scan respectively while P16, P20, and P25 utilize static scan mode.

Monochrome or dual-color LED display scan modes:

They atypically feature constant current 1/4, 1/8 scan and 16 scan, among others.

Scan TypeBrightness ComparisonApplicationControl Mechanism
StaticHighest brightnessOutdoorEach pixel (usually one LED bead) is individually powered, ensuring ample driving current for high brightness.
1/2 ScanLower than staticOutdoor and semi-outdoorThe current intended for a single LED is alternately supplied to two LEDs. The scan frequency of 100 times per second makes the switching unnoticeable to the human eye.
1/4 ScanHalf the brightness of 1/2 scanSemi-outdoor and indoorSimilar to 1/2 scan, but the current is alternately supplied to four LEDs instead of two.
1/8 ScanHalf the brightness of 1/4 scanIndoor (due to low brightness)Extends the concept of 1/4 scan, dividing the current among eight LEDs.
1/16 ScanHalf the brightness of 1/8 scanIndoor (due to very low brightness)Further extends the concept, dividing the current among sixteen LEDs.

Detail and Differentiation of Scan Modes:

Most LED displays use either static or dynamic scanning modes; static scanning further differentiated into real pixels and virtual pixels for static scanning, and dynamic scanning divided between real pixels and virtual pixels when it comes to dynamic scanning.

Dynamic Scanning:

Dynamic scanning involves controlling pixels directly via their output of driver ICs rather than from their driver output circuits to columns, thus providing lower costs but with reduced display quality and brightness. Control circuits may be needed, leading to additional costs but ultimately offering increased display quality over dynamic scanning’s use.

AdvantagesDisadvantages
The display driving circuit is simple; two ICs can drive up to 8 LEDs under 10 inches, resulting in lower costs.There are many wires between the LED and the driver board, making wiring installation and maintenance inconvenient.
LEDs of various sizes can be directly connected to the main control board, driver board, and expansion board, and in some cases, may not even require a PCB board.
Low power consumption; uses time-division scanning display method, consuming only 1/5 of the power compared to static driving.

Static Scan:

Static scanning involves controlling driver IC output directly with individual pixels for control over static scanning. Although more costly, static scanning offers superior display quality and stability while minimising brightness loss.

AdvantagesDisadvantages
Simple wiring between LED display components, requiring only 5-6 wires to connect all LEDs, making debugging and maintenance more convenient.Each LED requires 1-2 driver ICs, necessitating the production of display component PCB boards.
High brightness, suitable for outdoor large digital screens, with appropriate driving components able to drive LEDs up to 2 meters.Higher power consumption.
Slightly higher cost.

Driver Devices:

Some commonly utilized driver devices include Chinese HC595, Taiwanese MBI5026 and Japanese Toshiba TB62726, all supporting 1/2, 1/4, 1/8 and 1/16 scans respectively.

Example Illustration:

For a commonly used 16*8 (2R1G1B) full color module using MBI5026 drivers as drivers:

32 MBI5026 chips represent static virtual pixels;

16 indicate dynamic 1/2 scan virtual pixels and 8 dynamic 1/4 scan virtual pixels respectively, while 24 MBI5026s indicate static real pixels.

12 MBI5026 chips denote dynamic 1/2 scan real pixels while 6 indicate dynamic 1/4 scan real pixels.

Pixel and Virtual Pixel:

A “pixel” and its virtual equivalent refers to imaging units used for real world imaging applications. Real pixels involve each emitting element contributing directly to one pixel for sufficient brightness while virtual ones use software algorithms to manage each emitter’s participation across multiple adjacent pixels and attain greater resolution with less light elements.

The above is the basis and introduction of the LED display scanning method. So what are the transparent LED display driving methods?

Transparent LED Display Scan Modes:

Transparent LED displays utilize both static and dynamic scan modes – also referred to as scanning drives – when scanning displays are turned on, such as when used for photorealistic simulation. Below IAMLEDWALL explore these modes in depth with their characteristics and differences being examined:

1/1 Scan is designed for outdoor use due to its higher brightness driving mode; 1/2 Scan provides reduced brightness than static mode; however it should still be suitable for semi-outdoor and indoor usage as it features half the brightness of 1/2 scan and can accommodate semi-outdoor and indoor conditions as well as some weather conditions.

1/4 Scan uses half as much brightness of 1/2 scan for semi-outdoor and indoor settings respectively while 1/8 and 1/10 Scan operate more slowly indoors typically used indoors for best results.

Related:

P3 Vs. P5 Transparent LED Displays: Which Is Better?

Conclusion:

Electronic LED displays use various scan modes such as 1/2, 1/4, 1/8 and 1/16 scans for their displays, each having an impactful choice that requires adjustments in receiver card settings to optimize display configuration and achieve visual results that meet desired visual outcomes. Understanding their differences is paramount for optimizing LED display configuration and realizing desired visual outcomes.

FAQs:

What are the types of LED driver chips?

There are two major types of LED driver chips: Generic and Specialized.

  • Generic chips: 

They are not specifically designed for LEDs, but are logic chips that have some of the logic functions required for LED displays.

  • Specialized chips:

 They are specifically designed to drive LED displays based on the light characteristics of LEDs. They are devices that operate based on current characteristics, the brightness varies with the current, rather than adjusting the voltage across the device

. One of the key features of specialized chips is to provide a constant current to ensure the stability of the LED drive, eliminating flicker and ensuring a high-quality LED display. 

Some specialized chips also include additional functions for different industry requirements, such as LED failure detection and current correction functions with current gain control.

What is a key trend in the development of LED display driver ICs?


A1: A key trend in the development of driver ICs for LED displays is energy conservation. This is part of the industry’s continuous pursuit of green, energy-efficient solutions and is considered an important criterion for evaluating the performance of driver ICs.

How is energy efficiency achieved in driver ICs?


A2: Energy efficiency in driver ICs is achieved through two main strategies: first, by reducing the threshold voltage for constant-current operation, and second, by optimizing algorithms and IC design to reduce both operating voltage and current.

Why is high integration important in the development of LED display driver ICs?


A3: High integration is critical because of the rapidly decreasing pixel pitch of LED displays, which significantly increases the density of packaged devices mounted on modules. This leads to crowded PCB (Printed Circuit Board) layouts and increases circuit design complexity, which can lead to problems such as poor soldering and reduced module reliability. High integration of driver ICs helps reduce the number of components, allowing for larger PCB layout areas and overcoming these challenges.

Can you give an example that illustrates the challenge of high integration in LED display driver ICs?


A4: An example that illustrates the challenge of high integration is in small pitch P1.9 LED displays, where a configuration of 15 scans, 160 x 180, with 90 modules requires 45 row drivers and 2138 constant current driver ICs. This large number of devices makes the PCB wiring space extremely limited, increasing the difficulty of circuit design and the likelihood of soldering problems, while also reducing module reliability.