You have to know the LED to go to the power design!

The lighting fixture design is based on a three-way game of LED lighting, drive control and optical cooling structure design. According to the comprehensive consideration of the circuit structure of the luminaire, the power supply design is suitable for a large number of lighting products, and comprehensive consideration can show the advantages.


First, LED lighting route analysis

The lighting fixture design is based on a three-way game of LED lighting, drive control and optical cooling structure design.

1. Luminous part:

The LED light-emitting chip has been continuously improved in light efficiency, and the LED energy-saving controversy has gradually faded. In the next few years, there will be further improvement, and the accelerated application of LEDs will lay a solid foundation, and the design of lamps will become simple. The packaging method will change according to the application of the luminaire. For a long time, according to the LED heat dissipation, the package design is developed. With the understanding of the heat dissipation of the LED package, the package form of the special luminaire is more suitable. The upstream investment of LED epitaxy has increased, competition has intensified, and downstream applications have not yet risen, which will inevitably lead to a significant drop in the price of LED chips. Compared with packaging cost reduction, the cost of some LEDs is lower than the cost of packaging, so packaging technology innovation is also one of the most important parts of LED development.

2, drive control:

The increase in drive conversion efficiency is one of the most effective solutions. Increasing the power conversion efficiency can reduce the overall lamp power, which is to improve the overall lighting efficiency and save the heat dissipation design cost. There is no regulatory requirement for switching power supplies before power factor requirements, but LED lamps have a hard target. Reliability and longevity are also important parts. There are also aspects of color temperature, brightness, and intelligence that are also in the future, at a later time.

3. Optical design and heat sink:

The optical design is user-friendly, and the design of the lamp has recently developed rapidly, starting with an alternative route. In the future, LEDs should develop LED products that are more suitable for LEDs. The heat dissipation structure tends to be more rational, and more standardized module light sources show advantages. New material cooling technologies are being introduced, and the cost will be further reduced.

According to the analysis, only the LED lamp indicators of the short-lived devices can be comprehensively improved, and the inductors, electronic transformers and electrolytic capacitors can be eliminated, and the life and volume problems can be completely solved. Improve power drive efficiency and reduce heat source to extend lamp life. It is well known that only innovative technologies can make their own leap-forward development and intercept the LED technology evolution path. Only independent innovation, access to more intellectual property rights, paving the way for the subsequent development of LED.

Cancelling the power supply cannot be understood as not requiring a drive, and it is not necessary to "electricate". Instead, some of the devices that hinder the life of the power supply are eliminated. A new LED driving method is called "De-Power Technology".

Second, high voltage nominal value LED design

The development of "de-powered design" must develop high-voltage LEDs. Multiple LEDs can be called high-voltage LEDs. The serial connection method includes lithography technology, flip-chip connection, COB gold wire connection, and PCB single-particle welding.

At present, most of the design lamps use single-particle low-voltage LEDs, which is the main reason for designing lamps that require power conversion. The best way to get the best drive efficiency is to get the LED voltage closer to the drive voltage. This eliminates the need for power conversion, and the simplified current circuit structure of the constant current source can complete the driving task.

LEDs have one of the same characteristics as incandescent lamps. The incandescent lamp adopts tungsten filament illumination, which can adapt to 1.5-380V voltage, and obtain different impedance through the thick and thin tungsten filament to adapt to different voltage driving requirements. LEDs can also be connected in multiple numbers to obtain different high voltage values. The nominal voltage is visible as a guide for developing high voltage LEDs. In fact, foreign AC LEDs and high-voltage LEDs are also realized through lithography. Officially, they have not been able to find the correct market position because they have deviated from the nominal value guide.

Need to develop several nominal voltages? According to the research, the mains voltage of each country is mainly 110V and 220V, and the same power source can be obtained under the same power. High-voltage LEDs can eliminate the need for power supply voltage conversion in our designs, or use traditionally proven switching power supplies without the need to develop new power systems. At the same time, the new power supply design is welcome to support LEDs, but it is necessary to ensure the design life of the lamps and improve the reliability of LED products on the basis of the verified power supply.

Third, to power design

Figure 1 shows the main design methods. The AC-LED is also designed with LEDs for its rectifier bridge. The rectifier bridge is also part of the illumination. Its advantage is that the volume can be designed to a minimum. The disadvantage is that the heat is concentrated in a small volume, and at the same time, insulation treatment is required, and the design cost is the highest. Because the reverse voltage value of the LED itself is low, only about 10V, so that to obtain a reverse rectification withstand voltage of several hundred volts, 30% of the LED particles are wasted.

AC LED, high voltage LED and low voltage LED circuit

Figure 1 AC LED, high voltage LED and low voltage LED circuit


Therefore, the development of AC LED has been unable to allow customers to accept the price for several years. However, the analysis believes that there will still be 5% market opportunity, because the AC LED is the smallest volume in the market segment with high volume requirements.

The LV-LED portion of Figure 1 is currently the most used drive, including the traditional rectifier bridge section, a single-particle LED that requires a voltage conversion circuit in the middle. The voltage conversion part follows the traditional switching power supply technology. The power supply design is aimed at the power supply drive, and the development of a more suitable LED application circuit is simple and reliable in the batch process. The traditional switching power supply drives the LED and will be challenged by the de-energization technology. .

The de-energized design is a dedicated drive circuit for lighting design. In some market segments, it cannot be covered by a dedicated driver IC, or a switching power supply will be used, which will have a market opportunity of 10-20%.

HV-LEDs are the focus of today's discussion. High-voltage LEDs make the LEDs voltage close to the drive voltage, eliminating the need for a power conversion section. The difference between HV-LED and AC-LED is that the rectifier bridge is not in the design range of the light source. In the luminaire design, the mature rectifier bridge part can be greatly reduced, which can greatly reduce the design cost. Compared with LV-LEDs, HV-LEDs do not require power conversion, and drive efficiency and circuit design are greatly simplified.

AC LED, high voltage LED and low voltage LED power supply drive parameter comparison

Table 1 Comparison of AC LED, high voltage LED and low voltage LED power supply drive parameters


It can be seen from the test data of Table 1 that the AC LED driving efficiency is low, and the electrical parameters are generally low except for the high power factor. The most deadly problem is the flickering, especially in the case of photographic shooting, without constant current circuit support, PTC current-limiting driving mode performance is poor, design cost and light efficiency are generally low, the biggest advantage is that the light source volume is the smallest. UL certification requires that the source be fluctuated at ±10% without seeing the source flicker, which is clearly not possible with PTC.

The low-voltage LED driving power supply is a product transplanted from the primary side feedback circuit of the optical power supply, and the design circuit is complicated, and the constant current precision error is large. The driving efficiency of the small power switching power supply is designed to be 80% at best. The LED application begins to require power factor, and the low power supply does not. Device life is limited and the built-in power supply is limited in size, which limits market opportunities. High-voltage LED is a product born out of the above problems. It combines the advantages of AC LED and low-voltage LED. The driving efficiency and constant current accuracy are greatly improved. The parameters are excellent and the performance and price ratio are high.

There are two ways to de-energize the current design, one of which is:

The power conversion circuit part is completely eliminated, the simplest rectifier bridge and a capacitor are formed, and the constant current protection circuit is driven to integrate with the light source, and the light source part is integrated with the high voltage LED package. There is also an electrolytic capacitor. It is not prohibited to use electrolytic capacitors in the certification of various countries. It seems that many places cannot be without it. The existence of electrolytic capacitors brings many indicators to improve, and the drive circuit can be simplified.

De-powered design method 2 :

This current supports omni-directional thyristor dimming, and electrolytic capacitors are also eliminated. The devices that theoretically affect life are all eliminated, and the driving efficiency is slightly lower than that of mode one. 75% efficiency is equivalent to that of low-power switching power supplies, but reliability is reliable. Huge improvements. LEDs are used for multiple high voltage LED combination segmentation applications.

The lamps can be applied to the power supply design. It depends on whether the market is worthy of direct investment. Under certain circumstances, the advantages and costs of power supply design performance are absolutely competitive. In today's era of constant change, the power supply must occupy 80% of the mainstream market in the future. De-powered design is a technology-intensive project with a long design battleline and comprehensive technical coordination capabilities to complete the design perfectly. And multiple links to innovation, test equipment also needs to develop cross-industry integration, test the agglutination of the overall design team.

Fourth, the development of lighting design ideas

Design the light source according to the lighting product. Our light source has always been based on the light source and heat dissipation considerations, and we do not know the requirements of the lamps without foresight. The luminaire company designs the optical heat dissipation structure of the luminaire according to the established light source. Most companies follow the development of the first line, active research and development of the light source is too small, the package is in a passive situation, the lighting design is limited. A qualitative batch luminaire requires a light source that better matches this luminaire.

According to the power development drive mode, the tens of kinds of drive methods still have its limitations. LED lamps are mainly concentrated within 20W of power, which is the weakest place for switching power supplies. LED applications above 20W account for less than 30%, and most of them use modular design, combined design large wattage lamps, so LED driver design can be designed within 20W.

According to the comprehensive consideration of the circuit structure of the luminaire, the power supply design is suitable for a large number of lighting products, and comprehensive consideration can show the advantages.

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