In this era of high energy-saving calls, the further energy-saving of LED displays has become a support point for this industry. Many companies have made improvements in various aspects at this point, and have improved to a certain extent, achieving energy-saving effects, but there is still a long way to go to achieve greater energy conservation, which requires the common industry Work hard.
Recently, there have been a few energy-saving LED displays on the market. Through the improvement of the power supply, the energy-saving effect of the LED display has been greatly improved, attracting the attention of many consumers and giving them a high expectation. Many LED display manufacturers are eager to try, and are ready to introduce this technology first, and get the first opportunity for development. Based on the current technology, how is the energy-saving effect of energy-saving LED display achieved?
We use a small LED module to analyze its power consumption! For example, CYT62726 from Changyun Optoelectronics is a small LED module for driving chips. Its power supply voltage is 5V. The power consumption of peripheral devices is not calculated because they are in the whole screen. The proportion of the screen is very small, the power consumed by the entire screen is on the lamp. First calculate the power of the lamp point as Pled=n*Uvf*Iled (n is the number of channels, Uvf is the voltage drop of the LED lamp point, and Iled is set The current value of the CYT62726 driver IC is generally about 0.6V, and the voltage drop of the red, green and blue lamp points is 1.8V, 3.0V, 3.0V, so that each channel only needs 4V (3.0+0.6V). ) can work normally, conservatively can be set to 2.8V red channel, blue and green channel 3.8V and actually our supply voltage is 5V, which is equivalent to increase the power consumption of 1V * Iled inside the IC, so as above It can be imagined that as long as the power supply is reduced to red 2.8V, green 3.8V, blue 3.8V, we can save the 1V*Iled power consumption on the IC channel, and realize LED display while other devices are unchanged. Screen energy saving of at least 15%, plus the reduction of LED screen cooling requirements can also achieve a certain range Energy saving, this is already a fairly large number for a big screen, I believe customers will be happy to accept!
We can further analyze the principle of energy saving!
First of all, from the perspective of the power supply, if 5V is to be reduced to 4V, the proportion of the output voltage of the rectified Schottky forward voltage drop must increase. The lower the output voltage of the switching power supply, the higher the specific gravity of the rectified Schottky forward voltage. (The specific gravity X=V pressure drop/V output, the output is reduced from 5V to 4V, and the voltage drop is 0.5V, the specific gravity will increase from 0.1 to 0.125, increase by 25%), and the power output efficiency will be lower. The overall energy-saving effect of the LED screen is not obvious, so 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. The new switching power supply voltage is enabled, which reduces the efficiency and increases the cost. The quality is difficult to guarantee and the implementation is difficult.
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. The basic principle is shown in Figure 4. Q10 is a power MOSFET. In 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, and the power loss of the synchronous rectifier circuit mainly includes Q10. Conduction loss and 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 driving a higher power synchronous rectifier, a CMOS high speed power MOSFET driver can also be used when the gate peak drive current IG(PK) ≥ 1A is required. Synchronous rectification instead of Schottky rectification can effectively reduce the proportion of consumption in the output power. The use of synchronous rectification technology is a must.
When choosing an AC/DC switching power supply, you can use the new technology of half bridge or full bridge, which can improve the efficiency of switching power supply to over 90%. Of course, these technical applications, the power supply to the LED display can reduce the voltage to the best state, and the efficiency of the power supply can also reach a high efficiency level, so the use of new power technology to power the LED display can achieve significant energy savings. There will certainly be some increase in power costs.
Secondly, we can carefully study the LED screen driver IC, the output is a MOS switch tube, control the output port is closed or open, the output port voltage drop is VDS = 0.65V, which is determined by the process and materials. The VDS is reduced to 0.2V or even 0.1V, and 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 process of starting from the IC, reducing the corner voltage and making the driver 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.
In summary, the realization of LED energy-saving display is mainly from the power supply, directly using the half-bridge or full-bridge high-efficiency switching power supply on the existing LED display, plus the synchronous rectification energy saving effect is remarkable. The power supply voltage is reduced as much as possible in the state of constant current of the driving IC, and the power is separately supplied by the red, green and blue dies to achieve better energy saving effect. Of course, the application cost of such non-standard voltage power supplies and new technologies is bound to increase. From the perspective of the screen driver IC, the energy saving is not obvious, and reducing the driving constant current differential pressure will bring new problems including cost.
Dual-band WiFi module refers to the WiFi module that supports both 2.4GHZ and 5GHz bands. The dual-band WiFi module can operate in the 5Ghz band, which is much cleaner and can easily avoid interfering with each other. The advantage of 2.4G is that it has good ability to penetrate the wall, and the disadvantage is that it is easy to be disturbed. The advantages of 5G are strong anti-interference ability, wide band width, high throughput rate, and strong scalability, but the disadvantage is that 5G is only suitable for indoor small-range coverage and outdoor bridge, and the attenuation effect of various obstacles on it is much larger than 2.4g.
Dual-band WiFi module has a stronger and more stable Wifi wireless signal, higher transmission speed, and can make wireless devices more power-saving, to meet the future high-definition and big data wireless transmission needs.
When selecting a dual-frequency WiFi module, we should pay attention to these parameters of the WiFi module: size, package, frequency range, data rate, transmission rate, transmission distance, communication interface, power supply voltage, antenna interface, etc.
Dual frequency WiFi module can well meet the functional needs of users, increase the competitiveness of the product, while the WiFi module is easy to use, can shorten the user product development cycle, speed up the product market! Users can make choices according to actual needs!
Choosing a dual-band WiFi module may need to pay attention to the following points:
(1) Consider the transmission power of the dual-frequency WiFi module
The transmitting power of the WIFI module is generally about 18dBm, and the transmitting power of the high-power WIFI module is about 28dBm.
(2) Transmission rate
Consider whether the dual-band WiFi module supports MIMO technology (that is, allows multiple antennas to send and receive multiple spatial streams simultaneously)
(3) Consider the application interface that dual-band WiFi modules can provide, which is also very important.
(4) According to the requirements of the application scenario to choose the dual-band WiFi module, not the higher the configuration, the better, the application is good, excess waste!
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