How are energy saving LED displays designed?

We often have heard about the LED display energy saving, then energy-saving LED display is how to design it? Let us analyze the following energy-saving display how to design it.

First of all, from the power supply point of view, if you want to 5V down to 4V, then, Schottky forward voltage drop in the output voltage accounted for by the proportion can be determined to increase, which also allows the switching of the power supply output voltage is subsequently reduced, due to the rectifier Schottky forward voltage proportion the higher (the proportion of its X = V voltage drop / V output, the output from 5V down to 4V, adding its voltage drop of 0.5V, then its proportion will rise from 0.1 to 0.125, an increase of 25%), the lower the power output efficiency, which is not too obvious on the overall energy saving of the LED screen.

So the use of this power supply design principle is obviously unable to realize the power supply efficiency. At the same time, 5V is the nominal value of the voltage, the use of the market has been quite mature, if the new power supply voltage is enabled, although reducing the efficiency and increasing the cost, the quality is difficult to get to ensure that it is difficult to realize such a practice.

Power supply design is a more mature field, and can use other design ideas to achieve the degree of display power supply, such as synchronous rectification technology. Q10 for the power MOSFET, in the positive half-week of the secondary voltage, Q10 conduction, Q10 rectification role; in the negative half-week of the secondary voltage, Q10 off, synchronous rectification circuit power loss mainly includes Q10 conduction loss and gate drive loss. The power loss of the synchronous rectifier circuit mainly consists of the conduction loss of Q10 and the gate drive loss. When the switching frequency is lower than 60KHz, the conduction loss is dominant; switching frequency is higher than 60KHz, the gate drive loss is dominant.

In the design of low-voltage, high-current output AC/DC or DC/DC converter, synchronous rectifier technology can significantly improve the power efficiency, even up to 95%. When driving a larger power synchronous rectifier, the gate peak drive current IG (PK) ≥ 1A can also be used CMOS high speed power MOSFET driver.

Of course, the use of this technology in the led display power supply is the voltage can be reduced to the required voltage value, at the same time the efficiency of the power supply can also reach the value of the general switching power supply voltage, so the use of synchronous rectifier technology to the led display power supply can achieve the significant energy-saving effect, the power supply cost is also sure to have some increase.

Secondly, we can carefully study the led screen driver IC, control the output port off or on, and the output port voltage drop that is VDS = 0.65V or so, this is the process and materials decided to reduce the VDS to 0.2V, or even 0.1V, itself, the area required must increase. The structure of the MOS tube can be seen in the GS, GD between the existence of parasitic capacitance, and MOS tube drive, in fact, is the charge and discharge of capacitance.

This charging and discharging process takes time, and the area of the increase in parasitic capacitance on the MOS tube will also increase, so that the consequences of the port response speed of the entire IC decreased, which will be a LED screen driver IC is a fatal weakness.

Therefore, want to start from the IC, the turnover voltage down, while making the driver IC have enough response speed, plays a decisive role in the process, which is challenging to realize. Some people think that other design principles can be used, but if it is a constant current IC, the internal circuit is likely to be different, but the channel port of the switching tube must exist, so even with other design principles, to achieve the purpose of the voltage drop is also challenging to achieve.

Summarize the above factors, we can find that the energy saving in the LED to receive, mainly from the power supply to start, that is, in the state of the driver IC constant current must reduce the power supply voltage input, and red, green and blue tubes core separate power supply, but also to achieve energy saving, except that the cost of this will increase. And from the IC the start is really quite difficult, that is, the realization of energy-saving LED and IC has nothing to do, but a power supply innovation. In fact, it is equivalent to a power supply we will use in the ordinary driver IC, in fact, can also achieve the effect of energy saving requirements.