Is the energy-saving LED display true or false?

The energy-saving effect of LED display is well known, which is also the highlight of its most attractive to consumers, and it is also the reason for the rapid growth in recent years. Of course, after years of mad growth, the industry is now in a stalemate to reshuffle. In this dilemma, there are bound to be many enterprises that have been affected by this and have been badly hurt, and even went bankrupt. Of course, many enterprises will go out of their haze and gain more long-term development. This is the law of development of the industry. Any enterprise can't escape this disaster. How to regenerate in the disaster is a problem that every enterprise is currently paying attention to.

Figure 1 Led display basic architecture

In this era of high energy-saving calls, the further energy-saving of led display has become a support point for this industry. Many companies have made improvements in various aspects at this point, and indeed have improved to some extent, but have not solved the problem from the root cause.

There are also a small number of energy-saving driver ICs on the market, which are fundamentally energy-saving. This has indeed attracted the attention of many consumers, and has given quite high expectations. Many LED display manufacturers are eager to try. Be prepared to introduce this technology first and gain development opportunities. However, can you really achieve energy-saving effects from the LED screen constant current driver? I thought it couldn't, at least not at the consumer.

Can be analyzed: the current mainstream of energy-saving led display is the use of so-called energy-saving driver IC, and then the various led die separate Power Supply . The turning voltage of some energy-saving driver ICs appearing on the market can be reduced to 0.2V or 0.1V, usually about 0.65V. In this case, for the supply voltage usually required to add 5V, it is only necessary to add 4V or 3.5V. The current setting is unchanged, and the power consumption P=V*I can be reduced by about 30%. From the data point of view, the energy saving effect can be achieved, but this is only a theoretical result. Can you actually achieve this effect?

First, from the perspective of the power supply, as shown in Figure 2, if 5V is to be reduced to 4V, the rectified Schottky forward voltage drop accounts for the output power.

The specific gravity of the pressure must increase, and the lower the output voltage of the Switching Power Supply, the higher the specific gravity of the forward voltage of the rectified Schottky
X=V voltage drop/V output, the output is reduced from 5V to 4V, and its voltage drop is 0.5V, its specific gravity will increase from 0.1 to 0.125, increase by 25%), the lower the power output efficiency, the LED screen as a whole Without energy conservation, energy saving is only an appearance, and it does not realize the energy saving effect in the true sense. At the same time, 5V is the nominal voltage, which is quite mature in the market. The new power supply voltage is enabled, the efficiency is reduced, the cost is increased, the quality is difficult to guarantee, and the implementation is difficult.

Secondly, we can carefully study the LED screen driver IC, as shown in Figure 3.

Figure 3 LED screen driver IC internal block diagram

The output end is a MOS switch tube (as shown in Figure 4). The output port is controlled to be off or on. The output port voltage drop is VDS = 0.65V. This is determined by the process and materials. The VDS should be reduced to 0.2V or even 0.1V. The area required by itself must increase. It can be seen in the structure of the MOS transistor that there is a parasitic capacitance between GS and GD, and the driving of the MOS transistor is actually charging and discharging the capacitor. This charging and discharging process takes a while. If the area increases, the parasitic capacitance on the MOS tube will also increase. As a result, the port response speed of the entire IC decreases, which is for an LED screen driver IC. It will be a fatal weakness. Therefore, it is difficult to achieve the reduction of the corner voltage and the sufficient response speed of the driver IC from the IC.

Figure 4 MOS tube

In summary, it is impossible to achieve energy-saving effects from the separate power supply of the LED screen driver IC and the die. This is just a pseudo-technique that masks the truth, just a representation to attract consumers. The solution cannot fundamentally solve the problem of energy saving, and it will introduce new problems.

(This article is Liu Dejian, FAE Department of Changyuntong Optoelectronic Technology Co., Ltd.)

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