Technical challenges that must be overcome in developing high-brightness LED lighting applications

LED luminous efficacy continues to improve. In order to meet the requirements of high brightness, the power of a single component has also increased significantly, especially the high heat conditions that follow. It is very likely that the light decay or life of the component will be relatively reduced due to the high heat problem. If the heat dissipation requirements of the component can be considered in the front-end process, it will be more efficient than designing the heat dissipation based on external conditions, and it can also sustainably develop higher-power, high-brightness LED components for daily lighting applications.

Over the past few years, environmental issues have continued to heat up, causing great changes in the current status of various electricity consumption. Terminal electrical appliances have undergone many major changes, such as CRT TVs being replaced by LCD TVs, and even incandescent lamps, which consume a lot of energy, have become light sources that countries have banned one after another.

Because 19% of global electricity consumption is used for lighting applications, if energy-saving lamps can be introduced in daily lighting, it may have a significant saving effect on global energy consumption. Therefore, in order to create a more environmentally friendly national image, governments of various countries have also actively developed energy-saving lighting applications through policies, regulations and industry guidance. Using existing LED or CCFL new light source designs to replace traditional light sources for daily lighting applications has also become an important development trend in the lighting industry.

Current status of traditional light source applications

In most practical applications, a large number of high-efficiency, high-brightness light sources are still required. For example, street lights, store lighting, store lighting, etc. require high-efficiency, high-brightness lighting facilities. Most of them use high-intensity gas discharge lamps (High-intensity disc ha rge; HID) or halogen lamps to meet the application requirements of high brightness and high illumination; and for long-term needs in stores and shops, most of them use fluorescent tubes (Compact Fluorescent Lamp; CFL); most residences still use a large number of incandescent lamps, fluorescent lamps (CFL), or new energy-saving bulbs for energy saving. In many practical applications, the light source with the highest energy consumption and the worst efficiency should be incandescent lamps, because when used, a large amount of electrical energy will be converted into useless heat, which will also reduce the life of the lamp.

Observing the specific light source application, the daily lighting market covers a wide range of application areas, including building lighting, signs, landscape lighting, retail, signal lights, street lighting and residential lighting. If we want to discuss the benefits of energy saving, we must propose a scientific evaluation method for existing lamps, such as using the input power ratio and the actual output lumens to measure the efficiency. Currently, the evaluation benchmark (or energy efficiency) is mostly implemented based on the number of lumens per watt. There is

a big gap in energy efficiency between different lighting solutions .

According to existing lighting applications, incandescent lighting solutions have the worst energy efficiency. For example, using a 60W incandescent lamp for lighting, the energy efficiency is about 10 lm/W, compared to the energy efficiency of CFL fluorescent lamps, which can reach 50 lm/W. A 100W HID can have 80lm/W, which is equivalent to producing 8,000 lumens of brightness.

The efficiency and practicality of LED light sources have been greatly improved.

The characteristic of LED is that it is an electronic component itself. Compared with light sources such as gas discharge HID lamps and CFL fluorescent lamps, which must be filled with high-pressure gas in glass containers, the volume is relatively smaller and does not need to be filled with toxic elements. The components themselves are equipped with metal contacts and can be welded and installed on any surface, which is very convenient.

LED has many advantages of future light sources, among which energy-saving efficiency is the most concerned focus of the industry.

In the past, due to the limitations of technology at the time, the brightness of LED could not be effectively improved, and it was mostly used as an auxiliary light source for indicative purposes. However, now, taking white light LED as an example, the production method has been greatly improved. For example, through the high-efficiency blue light LED phosphor coating, a luminous effect similar to white light is produced, and the brightness output of a single component is greatly improved. At present, white light LED has made great progress in energy efficiency. Under the color temperature of 4,500~6,000k, the test data in the laboratory can reach a high efficiency performance of more than 200 lm/W.

LED is a solid-state light source component. It has high hardness and strength. It is not like traditional light sources that are mainly made of glass and are not afraid of falling or impact. It can also be matched with different phosphor designs or configuration designs to produce light source effects with different characteristics. The overall component does not contain mercury and has a life cycle of more than 50,000 hours. The life of LED is much higher than that of incandescent lamps that can only operate for 1,000 hours.

There are still key issues to be overcome in the introduction of life applications .

Due to the differences in the physical properties of LED in the original device, the concept of making a light source system is very different from traditional design, and more technical and professional assistance is required.

The LED bulb design is relatively compact in space. How to integrate related circuits must rely on integrated chips to achieve the design goals.

1. Optical design

LED light sources are highly efficient point light sources. This overly concentrated light source will cause many problems in traditional applications. For example, if used as a desk lamp, the light pattern at close range will be uneven. Even though LEDs have a wide range of color control flexibility and good energy efficiency performance, they will affect the user experience when used in daily lighting applications. Point light sources must use optical lenses or structural designs (lenses, light-guiding materials) to produce light patterns similar to those of traditional lamps, which will increase the cost of the lamps and make it difficult to break through the physical properties of optics in a compact configuration design.

2. Heat dissipation design

Similarly, the LED component itself is limited to being a point light source. When the component emits light, the temperature generated by the component will be excessively concentrated on a single point. If the heat dissipation is not effectively handled, the component will be burned and even shortened in service life! In addition to the need for heat dissipation enhancement design of the component itself, for example, improvement through chip gold wire or substrate design technology to achieve self-heat dissipation design, even so, the heat source will still be excessively concentrated in the point position of the lamp. How to improve the processing capacity of node temperature control through active and passive heat dissipation design of external components has become a technical gap in the design of related lamps.

3. Drive and control circuit design

In actual application, LED drive light still needs a lot of electronic circuits to assist in order to achieve high efficiency. However, for the dimming design of general incandescent lamps, if you also want to implement it on new LED light sources, you must adjust the power supply through DC power supply control. At this time, if you consider energy consumption and power efficiency at the same time, the complexity of the electronic circuit of the drive will be greatly increased. The design is very discrete. The design of a large number of independent components causes the discrete design problem of the system, so that the overall energy saved is consumed in the related circuits.

At present, component manufacturers have adopted a single-chip dimmable control IC design, so that lighting manufacturers do not need to redevelop the matching circuits of different lamps. Using ready-made solutions can achieve both the operating experience compared to the old light source and more efficient energy saving benefits.
The E27 type LED energy-saving bulb consumes only 6 watts.

4. Power conversion circuit design

LEDs generally use DC direct current drive, but AC LEDs have more application flexibility and advantages in actual applications. Therefore, it is also a very important trend in the development of LED light sources! Especially since the general source of electricity for daily life is AC power, if we want to quickly popularize LED light sources in daily life applications, developing AC-designed LED products is the key to the rapid growth of related applications.