What is the difference between common cathode and common anode in LED display?

LED display has become a dazzling star in modern technology, they light up every aspect of our life. Since its inception, it has been widely used for its high brightness, rich colors, and flexible size applications. But at the same time, some LED displays have the problem of high power consumption. As the concept of green energy saving is deeply rooted in the hearts of the people, the demand for LED product reliability, service life and display consistency, energy saving and environmental protection is constantly increasing in the market. LED display products with common cathode power supply technology were also born.

When we come into contact with LED displays now, we often encounter the two concepts of common cathode and common anode. Have you ever wondered the difference between them? This article will demystify this mystery and take you into a world of light displays full of surprises.

As we all know, the core components of the LED display are light-emitting diodes, which have the same forward-conducting characteristics as ordinary diodes, that is to say, there are positive and negative poles. A common anode means that a single LED is connected through its positive pole and driven by the negative pole; while a common cathode means that a single LED is connected through its negative pole and driven by the positive pole.

What is the difference between "common cathode" and "common anode" for LED displays?

Common anode LED display

The anodes (positive poles) of each row of lamp beads in the unit module are connected together, the RGB is uniformly powered, and the current flows from the PCB to the lamp beads.

Common cathode LED display

The cathodes (negative poles) of each row of lamp beads in the unit module are connected together, R, G, and B are powered separately, and the voltage and current are accurately distributed to the red, green, and blue lamp beads, and the current passes through the lamp beads and then to the IC negative pole.

The difference between common cathode drive and common anode drive

1. Different power supply direction

The traditional common anode LED display current flows from the PCB board to the LED diode, and the RGB LED is powered by the same power supply with the same power, so the forward voltage increases.

In the common cathode mode, the current of the LED display first passes through the LED diodes, and the R, G, and B LEDs are powered separately. Voltage and current are distributed precisely as needed and then to the negative side of the IC. The forward voltage is reduced and, therefore, the internal on-resistance is reduced.

2. Different supply voltage

Red, green, and blue light-emitting diodes have different operating voltages, and the operating voltage of red light-emitting diodes is lower than that of green and blue light-emitting diodes. Common anode LED displays usually supply uniform power to the red, green, and blue light-emitting diodes. Since the voltage cannot be precisely controlled, a large voltage is often input uniformly, which will cause power loss.

The common-cathode LED display will provide separate and precise power supply according to the actual voltage required by the red, green, and blue chips, which can effectively reduce power loss and reduce heat.