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　 There are few energy-saving LED displays on the market. Will these energy-saving LED displays really save energy? So how to design energy-saving LED displays? Let us analyze how the energy-saving display is designed below.

        First of all, from the power supply point of view, if 5V is to be reduced to 4V, then the proportion of Schottky forward voltage drop in the output voltage must be increased, which also makes the output voltage of the switching power supply follow it. Decrease, because the proportion of the rectified Schottky forward voltage is higher (its proportion X=V voltage drop/V output, the output drops from 5V to 4V, adding its voltage drop to 0.5V, then its specific gravity will rise from 0.1 to 0.125, Increase by 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 value voltage, which is quite mature in market application. If the new power supply voltage is enabled, although efficiency is reduced and cost is increased, it is difficult to guarantee quality, so it is difficult to achieve this. Practice.

　　The design of power supply is a relatively mature field, and another design idea can be adopted to realize the power supply of the display screen, such as synchronous rectification technology. Q10 is a power MOSFET. In the positive half cycle of the secondary voltage, Q10 is turned on, and Q10 plays a rectifying role; 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 drive loss is dominant. When designing low-voltage, high-current output AC/DC or DC/DC converters, the use of synchronous rectification technology can significantly improve the power efficiency, even as high as 95%. When driving high-power synchronous rectifiers, when the gate peak drive current IG (PK) is required to be ≥ 1A, CMOS high-speed power MOSFET drivers can also be used. Of course, using this technology to supply power to the led display can reduce the voltage to the required voltage value, and the efficiency of the power supply can also reach the value of the general switching power supply voltage. Therefore, the use of synchronous rectification technology to power the led display can achieve the display With the effect of energy saving, the cost of power supply will definitely increase.

          Secondly, we can carefully study the LED screen driver IC, control the output port to turn off or on, the output port voltage drop is about VDS=0.65V, this is determined by the process and materials, VDS should be reduced to 0.2V, or even 0.1 V, the area required by itself will inevitably increase. It can be seen in the structure of the MOS tube that there is a parasitic capacitance between GS and GD, and the driving of the MOS tube is actually charging and discharging the capacitance. This charging and discharging process takes some time. If the area increases, the parasitic capacitance on the MOS tube will also increase. As a result, the result is that the port response speed of the entire IC decreases. This is for an LED screen driver IC. Will be the fatal weakness.

　　 Therefore, if you want to start from the IC, reduce the turning voltage and make the driver IC have sufficient response speed, the decisive role is the craftsmanship, which is difficult to achieve. 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 switch tube of the channel port must exist, so even if other design principles are used, it is necessary to achieve the purpose of voltage drop. Difficult to achieve.

        Summarizing the above factors, we can find that in the energy saving of LED, the main thing is to start with the power supply, that is to say, the power supply voltage input must be reduced in the constant current state of the driver IC, and the red, green and blue die Separate power supply can also achieve energy saving, but the cost will increase. However, it is quite difficult to start with IC, that is, the realization of LED energy saving has nothing to do with IC, but it is just an innovation in power supply. In fact, it is equivalent to using a power supply on an ordinary drive IC. In fact, it can also meet the energy-saving effect requirements.