New LED driver - de-powered technology

I. 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: LED light-emitting chip continues to improve light efficiency, LED energy-saving controversy is slowly faded. In the next few years, there will be further improvement, and the accelerated application of LEDs will lay a solid foundation, and the lighting design 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 to packaging costs, the speed is much faster, and some LEDs are already lower than the cost of packaging. Therefore, packaging technology innovation is also one of the most important parts of LED development.

2. Drive Control: The improvement of 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 of the current situation. 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.

We want to give the company a positioning, a competitive base. We understand the power drive design, find breakthrough points here, and focus on the development of the future. We need to develop some new driving methods to completely eliminate electronic transformers, inductors and electrolytic capacitors in order to truly improve the life of the lamps. Specially built-in power supply luminaires, internal components up to hundreds of degrees Celsius, including electrolytic capacitors, magnetic materials and enameled wire are threatened by short life.

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".

2. 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. Changyuntong chose lithography technology. We are a professional integrated circuit design company, knowing the maturity and production efficiency of lithography. We appreciate the flip-chip technology, and it takes time to get the price that can be accepted by the market. When COB gold wire is connected, it is difficult to guarantee the quantity of too much quality. The efficiency of absorption of blue light by gold wire will be reduced, and the price of gold will be firm. Therefore, COB gold wire connection can only be used as a market segment, and the popularity of scale is limited.

Changyuntong Optoelectronics Research believes that the current design of lamps uses a single-particle low-voltage LED, which is the main reason for the design of lamps requiring power conversion. The best way to get the best drive efficiency is to get the LED voltage closer to the drive voltage. In this way, the power conversion is not required, and the circuit structure of the constant current source is simplified to complete the driving task.

Changyun Optoelectronics found that LEDs have 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 short 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, due to deviation from the nominal value guide, they have not been able to find the correct market position.

Need to develop several nominal voltages? Changyun Optoelectronics Research believes that the mains voltage of each country is mainly 110V and 220V, and the same power source can be obtained under the same power. To this end, the city's centralized development of a 110V-LEDs can meet the lighting needs. In the low-voltage power supply part, the switching power supply forms a nominal voltage of 12V, 24V, 36V, 48V for a long time. The car is 12V or 24V. Both wind and solar energy require lead-acid battery energy storage, which needs to be 12V and 24V. To this end, we should focus on the 12V-LED design, because 24V, 36V, 48V are multiples of 12V, and LEDs can be connected in series under normal conditions.

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, we welcome new power supply design to support LED, but we need to ensure the life of our design lamps and improve the reliability of LED products based on the verified power supply.

Third, to power design

Figure 1 is currently the main design methods, AC-LED is also designed with LED combination for its rectifier bridge, and 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. 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 opportunities, 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 de-energized design is aimed at the power supply driver, and develops a more suitable LED application circuit. It 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%.

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

HV-LED is the focus of today's discussion. It is our design of high-voltage LEDs that makes the LEDs voltage close to the drive voltage and eliminates the need for power conversion. 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.

Table 1 AC LED, high voltage LED and low voltage LED power supply drive parameter comparison

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, there is no 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:

Completely canceled the power conversion circuit part, the simplest rectifier bridge and a capacitor, driving the constant current protection circuit and light source integration, the light source part is high voltage LED package integration. There is also an electrolytic capacitor. It is not forbidden 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 theoretically affected devices are all eliminated. 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 luminaires 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.

Four. Lighting design development ideas

Design the light source according to the lighting product. Our light source has always been considered in terms of light source illumination and heat dissipation, and there is no foreseeable need to know the needs of the lamp. 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, and the market starts to follow me. Active research and development of the light source is too small, the package is in a passive situation, and 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 driving type of 10,000 kinds, there are still 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.