In the design of LED displays, there are two different internal connection methods for the LED beads: connecting the cathodes together or connecting the anodes together, that is, common cathode and common anode. The internal connection method not only determines the direction of the current, but also the performance and lifespan of the LED screens.
This article will introduce you to the differences between these two methods and offer reasonable purchasing suggestions.
High-level Driving and Low-level Driving
The voltage difference(ΔV) is the fundamental cause of electric current flow. To make the LED beads emit light, you need to create a voltage difference in the circuit. This is achieved by the driver IC raising or lowering the voltage, thereby allowing current to form a closed loop.
A high level essentially means the driver IC outputs a high voltage, while a low level means the output is close to ground potential. If the voltage level is not appropriate, the circuit cannot conduct properly, and the LEDs will fail to light up.
The Working Principle of the Common Cathode in LED Displays
Common Cathode refers to the fact that the cathodes of the R, G, and B chips in each LED bead are connected together to form a terminal within a display, which is typically connected to ground (GND). The anode in the circuit is independently controllable, and the brightness of each LED bead is determined by the current flowing through the anodes.
Because the driver IC of the common cathode drive connection outputs a high-level current signal, the current control is more delicate. In particular, when the display screen brightness is relatively low, the common cathode connection method can control the tiny current and is less likely to cause jitter and flicker.
The Working Principle of the Common Anode in LED Displays
Common Anode means that the anodes of multiple LED beads within an LED module are connected together and tied to the positive terminal of the power supply. In this configuration, the cathodes are individually controlled, and the brightness of the LED display is determined by the amount of current flowing through the cathodes.
In a common-anode system, the driving method is typically active-low. It drives the LED beads to emit light by pulling the signal level low through the driver IC and completing the circuit. Its dimming is essentially PWM dimming, which means controlling the proportion of time for forming a loop to change the brightness you perceive.
Therefore, when the brightness is low, the current stability of the common anode connection method is weaker, and the dimming fineness is not as good as that of the common cathode.
Difference Between Common Cathode and Common Anode
Connection Method
In the common anode connection mode, the positive terminals of all LEDs are directly connected to the positive power supply, and the cathodes are individually connected to the driver IC. In contrast, in the common cathode connection mode, the negative terminals of all LEDs are directly connected to GND, and the anodes are driven by the driver IC. This is a source current structure, which makes power management more complex.
Direction of Current and Control Mode
The current flow direction of the common anode connection is from the positive terminal of the power supply to the LED, then to the Driver IC, and finally to GND, and the energy loss and heat generation are concentrated on the driver IC. As a result, the driver IC in a common-anode configuration tends to age faster.
In comparison, the current in common cathode mode is supplied by the power supply to the Driver IC, then to the LED, and finally to GND. Under this connection method, the driver IC acts as a set of controllable constant current sources, responsible for supplying current and capable of adjusting the current level.
Drive Compatibility
Due to the direction of the current, the common anode system must use a current sink driver IC, which has a lower cost and is easier to manufacture. Moreover, there are quite a few driver ICs compatible with common anode systems available on the market, and the manufacturing processes are already quite mature.
In contrast, the common cathode system requires a driver IC that can actively output a stable current to the LED. Such architectures are more complex, more costly, and offer fewer available options on the market.
Visual Performance
At normal brightness levels, the difference in visual performance between common-anode and common-cathode systems is not obvious. At low brightness and low grayscale levels, due to the limited control accuracy of the common anode in the low current range, uneven brightness and gray scale jumps may occur, which will affect your viewing experience.
However, common cathode systems are more stable at low current levels, which have smoother grayscale transitions, better color performance, and more consistent brightness.
Power Consumption and Screen Lifespan
In a common anode system, although the LED current is controlled by the IC, the supply voltage is fixed. The excess voltage will be concentrated on the driver IC and released in the form of heat. In contrast, the voltage of the common cathode system hardly incurs any loss. Therefore, even at the same brightness, the power consumption of a common anode system is much higher than that of a common cathode system.
Also, due to the power supply mechanism, the driver IC in a common anode system typically operates at a higher temperature. This accelerates LED light attenuation and shortens the lifespan of the module. As a result, common anode modules generally have a shorter lifespan than common cathode modules.
Cost and Supply Chain
From the perspective of the initial BOM (Bill of Materials Cost), the cost of the common anode system is low, and the design is simple, while the cost of the common anode system is high and the design is complex. However, from a long-term cost perspective, common cathode systems offer lower power consumption, lower heat management costs, longer lifespan, which leads to a lower maintenance cost over time.
From the perspective of the supply chain, the supply chain of the common anode system is more mature and has a larger number of suppliers, while the technology of the common cathode system is more complex and has fewer suppliers.
Application Scenarios
In the current LED display industry, the common anode solution remains the choice for most projects, while the common cathode solution is more commonly found in mid-to-high-end and professional applications.
Common anode systems are mostly used in projects where the display lifespan is not a critical requirement, such as indoor conference displays and stage screens. For projects that require long-term, continuous operation, such as airport information displays or high-brightness outdoor advertising screens, project owners tend to prefer common cathode solutions.
| Terms | Common Cathode | Common Anode |
| Connection method | Cathodes connected to GND | Anodes connected to VCC |
| Direction of current | VCC → Driver IC → LED → GND | VCC → LED → Driver IC → GND |
| Drive Compatibility | Requires high-performance source drivers | Compatible with most sink-type drivers |
| Visual Performance | Better brightness uniformity and grayscale accuracy | Limited in high-end performance |
| Power Consumption | Lower | Slightly higher |
| Screen lifespan | Longer | Shorter |
| Purchase Cost | Higher | Lower |
| Maintenance Cost | Lower | Higher |
| Supply Chain | Limited suppliers | Mature |
| Application Scenarios | High-end, high refresh rate, professional displays | Cost-sensitive displays |
How to Choose Between Common Cathode and Common Anode?
The Reasons for Choosing the Common Cathode
More Reliable System
Although the initial cost is relatively high, the common cathode system consumes less electricity, and its long-term cost is generally lower than that of the common anode system. Therefore, if you plan to use the display for long-term operation, common cathode systems are the more reliable choice, offering better cost-effectiveness and longer lifespan.
Better Visual Experience
As mentioned, common cathode systems offer higher grayscale precision, and they also perform better in terms of brightness and color consistency. If you are aiming for a better visual experience, common cathode systems are the preferred choice.
In addition, the brightness of common cathode LED display screens is usually higher, reaching 10,000 nits or even higher, which common anode systems cannot reach. If you wish to use the display in outdoor advertising or other high-brightness scenarios, common cathode solutions are a wise choice.
A Higher-End Target Audience
If you have a sufficient budget and you aim to position your LED screens for a high-end brand targeting premium users, the low power consumption, long lifespan, and superior visual performance of common cathode systems make them an outstanding selling point.
The Reasons for Choosing the Common Anode
Lower Cost and Higher Cost Performance
If you have a limited budget, common anode systems are the recommended choice. They offer lower upfront costs, a simpler structure, and easier maintenance. Moreover, common anode systems provide sufficient brightness, typically exceeding 3000 nits, making them suitable for most indoor scenarios.
Simpler Processing
The design, production, and commissioning of the co-anode system are all easier than those of the co-cathode system, and the overall construction period is shorter. If you plan to use the display for temporary events or other projects requiring fast delivery, common anode systems are the ideal choice.
A Larger Market
Due to its wide range of application scenarios, whether it is indoor display or shopping mall advertising, the common anode system has a large market demand. Therefore, its turnover is faster, and the expected sales volume is better. If you are a retailer and a brand owner and aim for a larger retail market, choosing common anode systems makes promotion easier.
Other Factors to Consider When Customizing a Display
When customizing or purchasing a display screen, apart from the choice between common cathode and common anode, there are some other key factors you need to consider:
Driver IC
Whether it is a common cathode or common anode system, the driver IC plays an essential role in the performance of the display. A good driver IC ensures that the display performs well in grayscale precision, refresh rate, and power consumption.
The most important thing is that, after choosing between a common cathode or common anode system, you need to select a driver IC whose specifications match your project; otherwise, the display may not operate properly.
Display Effect and Picture Quality
There is no doubt that different projects require different screen performances, such as size, shape, brightness, resolution, pixel pitch, and the smoothness of video playback. When you are customising an LED screen, no matter how it is connected, the presentation of the picture is of vital importance to the audience.
Reliability
The reliability of a display determines whether you can operate it with confidence. After determining the purpose of the display screen, you need to select appropriate indices such as the expected lifespan, maintenance frequency, protection capability, and heat dissipation performance based on the purpose. This allows you to estimate costs and ensure long-term operational stability.
After-Sales Service
After the display is put into operation, you may encounter some faults or technical issues. Therefore, the after-sales service provided by the supplier is equally important. A reliable supplier not only provides long-term after-sales service but also offers comprehensive support, including online and on-site technical guidance and repair services.
If you prefer long-term and reliable after-sales support, JINGYLED is your ideal choice. Our team can provide up to five years of after-sales service, including technical guidance and return for repair, and you can send requests to us at any time!
FAQS
Are High-Refresh-Rate LED Displays Better Suited to Common Cathode or Common Anode?
High refresh rate LED displays are more suitable for common cathode systems. This is because a high refresh rate has very high requirements for the accuracy of the current and the performance of the driver IC. Only the common cathode system can support such demands, while the common anode system performs even worse for high refresh rates.
How do Common Cathode and Common Anode Affect PCB Routing?
The connection type of LEDs affects the direction of current flow, thereby impacting the PCB routing. The wiring of the common cathode system is more dispersed, and the current path is longer, so it is necessary to wire reasonably to ensure the even distribution of current.
In common anode systems, the routing is more concentrated, but for high-brightness or long strip displays, the current density may be higher and demands better thermal design.
Which Approach is More Favorable for High-Density PCB Design?
In a common cathode system, the cathodes are connected to ground, which helps reduce EMI (Electromagnetic Interference), and the cathode can be made into a ground plane. In high-density PCBs, a stable and continuous ground plane is extremely important. Therefore, common cathode architectures are usually easier to achieve centralized management of power and signal routing.
Final Thoughts
If you are looking to customize an LED display with either a common cathode or common anode solution, JINGYLED is your ideal choice. We have a professional engineering team specializing in LED screen manufacturing, with more than ten years of experience across various types of displays. Also, we have worked with clients in over 120 countries and are highly familiar with the production requirements of different regions.
Feel free to contact us!
