The words vocabulary of energy conservation and environmental protection have emerged in society and the whole world. People have also made some changes in the way of life and the concept of life. In the development of LED industry in recent years, energy conservation will also become the primary task of the LED industry.
This is an era of energy saving and environmental protection. The further energy saving of LED display has become a support point for this industry.
Recently, there are a few energy-saving LED displays on the market. Are these energy-saving LED displays really saving energy? So how do you design energy-saving LED displays? Let's analyze how the energy-efficient display is designed.
First of all, from the perspective of the power supply, if you want to reduce 5V to 4V, then the proportion of the forward voltage drop on the output voltage can be increased, which will make the voltage of the switch's power supply output follow. Reduced, due to the higher the specific gravity of the rectified Schottky forward voltage (its specific gravity X = V pressure drop / V output, the output is reduced from 5V to 4V, and its voltage drop is 0.5V, its specific gravity will rise from 0.1 to 0.125, Increase 25), the lower the power output efficiency, which is not too obvious in the overall energy saving of the LED screen. Therefore, the use of this power supply design principle is obviously unable to achieve the improvement of power supply efficiency. At the same time, 5V is the nominal voltage, which is quite mature in the market. If the new power supply voltage is enabled, although the efficiency is reduced and the cost is increased, it is difficult to guarantee the quality, so it is difficult to achieve this. Practice.
The design of the power supply is a relatively mature field, and another design idea can be used to realize the power supply of the display screen, such as synchronous rectification technology. Q10 is a power MOSFET. During the positive half cycle of the secondary voltage, Q10 is turned on and Q10 is rectified. In the negative half cycle of the secondary voltage, Q10 is turned off. The power loss of the synchronous rectifier circuit mainly includes the conduction loss of Q10 and the gate. Drive loss. When the switching frequency is lower than 60KHz, the conduction loss is dominant; when the switching frequency is higher than 60KHz, the gate driving loss is dominant. When designing AC/DC or DC/DC converters with low voltage and high current output, synchronous rectification technology can significantly improve power efficiency, even up to 95.
Secondly, we can carefully study the LED screen driver IC, control the output port to open or open, the output port voltage drop is VDS=0.65V, which is determined by the process and materials, to reduce the VDS to 0.2V, or even 0.1 V, 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. Will be a fatal weakness.
Therefore, it is difficult to achieve the process by starting from the IC, reducing the cornering voltage and making the driving IC have sufficient response speed. Some people think that other design principles can be used, but if it is a constant current IC, the internal circuit may be different, but the switching tube of the channel port must exist, so even if other design principles are adopted, the purpose of achieving voltage drop is also Hard to achieve.
From the above description, it is not difficult to find out that in fact, in the energy-saving collection of LEDs, the main thing is to start from the power supply. That is to say, in the state of driving the IC constant current, the input of the power supply voltage must be reduced, and the red, green and blue are respectively The power can be saved by separately supplying the die, but the cost will increase. It is really difficult to start from the IC. That is to say, the energy-saving realization of LED has nothing to do with IC, it is just an innovation on the power supply. I might as well make the idea of ​​using a power supply on an ordinary driver IC. In fact, it can also achieve energy-saving effects.
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