How to increase the reliability of LED lighting systems

In order to create an energy-saving and efficient smart lighting system, the use of MCU and dimmable drivers for environmental sensing and high-efficiency dimming has become a popular design trend in today's LED lighting systems; in addition, optical and heat dissipation simulation is also an indispensable development link to ensure the reliability and safety of LED products.

Circuit design and system simulation are the two keys to realizing a smart light-emitting diode (LED) lighting system. If a microcontroller (MCU) is added to the circuit design, it can not only monitor the LED device around the clock and report abnormal conditions in real time, but also perform group control of lighting equipment to adjust energy, making the lighting system more intelligent. In order to enhance the stability of the LED light source, the introduction of a dimmable driver into the circuit design can solve the problem of light source flicker and improve energy efficiency.

On the other hand, it is even more important to verify the feasibility of the product through the simulation process of optics and heat dissipation. This not only ensures product safety, but also accelerates the product development schedule and enhances market competitiveness during the simulation process.

MCU plays an important role in realizing smart lighting system

As the use of LEDs becomes more popular, their applications are becoming more diverse, and the business opportunities of smart lighting systems are even more anticipated by the industry. To build LED smart lighting systems, the introduction of MCUs can achieve functions such as automatic brightness adjustment, automatic color change, environmental sensing, and group system control, enriching the applicability of LED lighting and improving energy efficiency.

Zhu Dansen, a senior application engineer at Infineon, said that MCU can enable LED lamps to realize smart lighting systems, fully improve energy efficiency and enrich the diverse applications of LEDs.

In the past, LED lamps lacked control and variation. Even though LEDs are more durable than traditional halogen lamps and incandescent lamps, their light output will still decline due to aging and temperature after long-term use, causing the electricity in the lamp to be easily damaged, greatly reducing reliability. The inability to dim the light also results in poor energy efficiency. The above factors ultimately shorten the life of LEDs. At the same time, the application will appear more monotonous and boring because the light cannot be changed.

In order to achieve the goals of dimming control, color change and efficient use of energy, the introduction of LED lamps into MCU can make indoor lighting, outdoor lighting, decorative lighting, and emergency lighting have more application changes, such as controlling LED lights to adjust the brightness according to different time periods throughout the day to save energy, or remote group control through the digital addressable lighting interface (DALI) in the MCU, and monitoring whether the LED device is still operating normally at any time to notify engineering personnel for quick maintenance. These new applications make LED lights no longer just on and off, but can also be used more flexibly.

It is understood that Infineon has launched two MCUs, XC835 and XC836, to seize the LED smart lighting market. In addition to the number of pins and size, the biggest difference between these two MCUs is that XC836 supports DALI, which can be used for remote control of LED lamps and lanterns, while XC835 does not. In addition, both models can support touch control and have high heat resistance (150℃) and high reliability. At present, this series of MCUs is mainly used in small and medium-sized fluorescent tubes and bulbs such as T4 and T8, which are common in the entertainment decorative lighting market.

For the entertainment decorative lighting market, since the entertainment performances are colorful, not only intelligent automatic dimming is important, but also the service life, luminous efficiency and light stability of LED lighting fixtures are also quite demanding. Therefore, dimmable drivers have begun to be designed into lighting systems to solve the above problems.

LED照明拚效率 可调光驱动器力挺

Governments around the world are increasingly demanding energy conservation, which has increased demand for dimmable LED lighting. To achieve high-efficiency dimming and solve the flicker problem, Texas Instruments (TI) recently released two highly integrated phase-dimmable AC-DC LED lighting drivers that can fully meet the dimming needs of retrofit bulbs, LED ballasts, downlights, spotlights and other lighting fixtures.

Xiao Yizhou, senior application engineer of power application products for analog product market development in Asia region of Texas Instruments, said that LEDs with built-in dimmable power driver ICs will soon completely replace traditional dimmable light bulbs.

Although traditional light bulbs can also be dimmed, they consume more power and have a short service life, which means that dimmable traditional light bulbs must be frequently repaired. The introduction of dimmable power driver integrated circuit (IC) LED lights not only takes into account the advantages of LEDs that save 80% of power compared to traditional light bulbs and have a service life of at least 20,000 hours, but also can be dimmed, improve energy efficiency, and accelerate the replacement of traditional light bulbs with energy-saving LED lighting.

In order to enter the energy-saving LED lighting market, Texas Instruments has launched the TPS92070/LM3448 dimmable series solutions. Its high current accuracy allows customers to accurately define the upper and lower limits of current, saving customers the time cost of constant calibration. In addition, due to its high-performance structure, it can reduce the peripheral parts supporting the driver IC, further reducing customers' costs.

Currently, a series of dimmable driver ICs from Texas Instruments are mainly sold to Japan, Europe, and the United States. However, due to different safety standards in different countries, the required driver IC specifications are also different. For example, the TPS92070 is designed to be isolated, which is safer and can meet the safety requirements of the United States. The main shipment to Japan is the LM3448 with no isolation design. Whether there is an isolation design or not affects the overall cost of LED lamps by about 2%, and everything depends on customer needs.

Under the requirements of relevant energy-saving laws and regulations, developed countries such as Japan, Europe and the United States have already adopted a large number of LED lamps with imported dimmable driver ICs. However, developing countries such as mainland China, as there are no relevant laws and regulations, use lower-cost LED lamps without dimming function.

As for Taiwan, although there are no relevant regulations, some lighting manufacturers have introduced dimming driver ICs. The application market is still mainly entertainment lighting market. General indoor lighting, outdoor lighting and emergency lighting have not yet begun to be popularized. If energy-saving regulations are further formulated in the future, energy-saving LED lighting will become more popular.

In addition to the advantages and disadvantages of each dimmer architecture, in order to accelerate the time-to-market of LED products and reduce overall development costs, the use of optical simulation and heat dissipation simulation to verify product feasibility before the product is officially produced has become an important weapon for related industries to defeat the enemy.

Accelerating LED development requires optical/thermal simulation

Mr. Zhuang Shiren, general manager of Green Bright Technology, said that through optical and thermal simulation, LED products can be brought to market as soon as possible while ensuring quality and reliability.

Since LED product design needs to go through many tests and verifications, if optical simulation and heat dissipation simulation are not done well, it will lead to quality defects after mass production. To solve this problem, using dedicated simulation software with three-dimensional (3D) models to accurately simulate and verify LEDs has become an important part of LED lamp development to ensure the quality and reliability of future LED products.

The biggest purpose of optical and thermal simulation is not only to accelerate the time to market, but also to avoid the cost burden of repeatedly making a large number of models due to incorrect simulation results. The simulation process and results will affect whether the product can be confirmed to be feasible in the shortest time, which in turn affects the time to market. Therefore, efficient optical and thermal simulation of products is very important.

The correct optical simulation process should first establish a 3D model, then establish a light source, and then establish an observation surface, and then analyze it through major simulation software such as Trace Pro and Light Tool. If you encounter a more complex optical structure, you may need to use auxiliary software such as ZEMAX and Code V to observe the results. If the test results are feasible, then output the results; if the test results cannot be optimized, return to the previous step and re-calibrate and simulate the analysis.

After the results of the optical simulation optimization are output, the heat dissipation simulation can begin. Zhuang Shiren emphasized that heat dissipation simulation can reduce unnecessary waste during proofing, and the data obtained through the analysis software and the actual temperature measurement error can be within 5°C, allowing R&D personnel to grasp the product parameters in advance. After the above simulation steps, the reliability of the product can be further ensured.

To conduct efficient optical simulation and heat dissipation simulation, in addition to being familiar with simulation software, R&D personnel must also have rich experience to quickly check which link has gone wrong. However, not every manufacturer can find excellent simulation verification talents. Therefore, some LED manufacturers nowadays directly copy the appearance design of international manufacturers in order to take shortcuts and save manpower and time costs, ignoring the importance of optical and heat dissipation simulation. It was not until the mass production of the product that they found that the quality was far from that of the big manufacturers, resulting in damage to their reputation.