LED energy-saving design or will dominate the future market

The words “energy saving and environmental protection” appear in the society and even the whole world. People also have some changes in the way of life and the concept of life. In the development of LED industry in recent years, energy saving will also become the top priority for the LED industry.

This is an era of energy saving and environmental protection. The further energy saving of LED display screens has become a support point for this industry.

Recently, there are a few energy-saving LED display screens on the market. Can those energy-saving LED displays really save energy? Then how do we design energy-saving LED display screens? Let us analyze how energy-saving display screens are designed. .

First of all, from the perspective of the power supply, if 5V is to be reduced to 4V, then the proportion of the forward voltage drop of Schottky to the output voltage can be increased, which in turn causes the output voltage of the switch to follow. Decreased, due to the higher proportion of the rectified Schottky forward voltage (its specific gravity X = V drop / V output, the output is reduced from 5V to 4V, adding its pressure drop to 0.5V, the proportion will increase from 0.1 to 0.125, 25% increase, 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 power supply efficiency improvement. At the same time, 5V is a nominal value voltage, and it is quite mature in the market. If the new power supply voltage is used, although the efficiency is reduced and the cost is increased, it is difficult to guarantee the quality. Therefore, it is difficult to achieve such a method. Practice.

The design of the power supply is a mature field, and another kind of design idea can be used 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 on, and Q10 is used for rectification. In the negative half cycle of the secondary voltage, Q10 is off. The power loss of the synchronous rectifier circuit mainly includes the conduction loss and gate of Q10. Drive loss. When the switching frequency is lower than 60KHz, the conduction loss dominates; when the switching frequency is higher than 60KHz, the gate drive loss is the main factor. In the design of 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 a high-power synchronous rectifier, when the peak gate drive current IG (PK) ≥ 1A is required, a CMOS high-speed power MOSFET driver can also be used. Of course, using this technology to power the LED display can reduce the voltage to the required voltage value, and the power supply efficiency 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 be achieved. With the effect of energy conservation, there will certainly be some increase in power costs.

Second, we can carefully study the led screen driver IC, control the output port off or on, the output port voltage drop 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. In the structure of the MOS transistor, it can be seen that there is a parasitic capacitance between the GS and the GD, and the driving of the MOS tube is actually the charging and discharging of the capacitor. This charge-discharge process requires a period of time. If the area is increased, the parasitic capacitance on the MOS transistor will increase. As a result, the overall IC's port response speed will decrease. This is an LED screen driver IC. It will be a fatal weakness.

Therefore, if you want to start from the IC, reduce the turn-on voltage, and at the same time make the driver IC have enough response speed, it is the process that determines the role, 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 not be the same, but the switch port of the channel port must exist, so even if other design principles are used, the purpose of achieving the voltage drop is also to achieve Difficult to achieve.

From the above statement, we can easily find that, in fact, LED energy saving, the main thing is to start with the power supply, that is to say, in the constant state of the driver IC must reduce the power supply voltage input, and red, green and blue Dividing the power supply by the die can also save energy, but this cost will increase. Starting from the IC is really difficult, that is to say, the realization of energy-saving LED has nothing to do with the IC, but is an innovation in the power supply. We may wish to make such an assumption and use a power supply for an ordinary driver IC. In fact, it can also meet the requirements for energy saving.