Discussing LED light source efficiency and design issues to be solved

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 situation of electricity consumption. Terminal electrical appliances have undergone many major changes, such as CRT TVs being replaced by LCD TVs, and even energy-intensive incandescent lamps have become light sources that have been banned in various countries.

As 19% of the world's electricity consumption is used in 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 are also actively developing 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 Application Status of Traditional Light Sources

In most practical applications, a large number of high-efficiency, high-brightness light sources are still required. For example, street lights, store lighting, and shop lighting require high-efficiency, high-brightness lighting facilities. Most of them use high-intensity gas discharge lamps (High-intensity discharge; HID) or halogen lamps to meet the application requirements of high brightness and high illumination. In stores and shops, fluorescent lamps (Compact Fluorescent Lamp; CFL) are mostly used for long-term needs. 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 lowest efficiency should be mainly 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.

In terms of specific light source applications, the daily lighting market covers a wide range of applications, including building lighting, signage, 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 measuring the efficiency by the input power ratio and the actual output lumens. Currently, the evaluation benchmark (or energy efficiency efficiency) is mostly implemented by the number of lumens per watt.

There is a big gap in energy efficiency between different lighting solutions

In the current lighting applications, incandescent lamps have the worst energy efficiency. For example, a 60W incandescent lamp has an energy efficiency of about 10lm/W, while a CFL fluorescent lamp has an energy efficiency of 50lm/W. A 100W HID lamp has 80lm/W, which is equivalent to 8,000 lumens of brightness.

LED light source efficiency and practicality 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 use glass containers to contain high-pressure gas, the volume is relatively smaller and does not need to be filled with toxic elements. The component itself is equipped with metal contacts and can be welded and installed on any surface, which is very convenient.

LED has many advantages as a future light source, among which energy saving is the most concerned focus of the industry.

In the past, due to the limitation of technology at that time, the brightness of LED could not be effectively improved, and it was mostly used as 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 phosphor coating of high-efficiency blue light LED, a luminous effect close to white light is produced, and the brightness output of a single component is greatly improved. At present, the energy efficiency of white light LED has made great progress. Under the color temperature of 4,500~6,000k, the test data in the laboratory can reach a high efficiency performance of more than 200lm/W.

LED is a solid-state light source component with high hardness and strength. It is not like traditional light sources that are mainly made of glass and are not easily dropped or impact-resistant. It can also be combined with different phosphor designs or configuration designs to produce light source effects with various characteristics. The entire 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, which can only operate for 1,000 hours.

There are still key issues to be overcome in introducing daily life applications

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

LED bulb design is relatively compact in space, so the integration of related circuits must rely on integrated chips to achieve the design goals.

1. Optical design

LED light sources are highly efficient point light sources. Such overly concentrated light sources have 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, 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 a point light source. When the component emits light, the temperature generated will be excessively concentrated on a single point. If the heat dissipation is not effectively handled, the component will burn out and even shorten its service life! In addition to the component itself, it needs to be designed for heat dissipation enhancement, such as improving the chip gold wire or the design technology of the carrier board to achieve self-heat dissipation design. Even so, the heat source will still be excessively concentrated at the point position of the lamp. How to improve the processing ability of node temperature control through active and passive heat dissipation design of external components has become a technical gap in related lamp design.

3. Drive and control circuit design

In actual application, LED driving 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 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 driving electronic circuit will be greatly increased. The existing design will use a large number of independent components to cause discrete design problems of the system, so that the overall energy saved will be consumed in related circuits.

Currently, component manufacturers have adopted a single-chip dimmable control IC design, so that lighting manufacturers do not need to redevelop the matching circuits for different lamps. Using ready-made solutions can achieve an operating experience that is comparable to that of old light sources, and can also achieve higher efficiency and energy-saving benefits.

4. Power conversion circuit design

LEDs are generally driven by DC, but ACLEDs have more flexibility and advantages in actual applications, so it is also a very important trend in the development of LED light sources! In particular, the source of general household electricity 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.