Five concepts of LED driver development

About 80% of the failures of today's LED lighting products come from the power supply. With the continuous improvement of LED light source product packaging technology and the continuous development of heat dissipation technology in recent years, the stability of the light source has reached a relatively good level. Even if there is any, it is light decay and color drift, which is mainly caused by unreasonable heat dissipation design. Direct necrosis is very rare. Relatively speaking, power supply problems are much more serious. Once a problem occurs, the light is usually dead or flickering, and the frequency of occurrence is relatively high. The light source of conventional lighting street lamps that fail and need maintenance is sodium lamps. The national standard for sodium lamps stipulates a one-year warranty period, and street lamp units will store a certain number of sodium lamps. Sodium lamps have mature national standards, and their main parameters such as the size and power of their main accessories are unified and interchangeable.

At present, the main fault of LED lamps is the power supply, so the solution to the main contradiction is to solve the power supply problem. Since there is still a lack of mandatory unified standards for LED power supplies, the power supplies on the market are independent of each other, single-channel, multi-channel, and of different sizes, which leads to many problems. With the emergence of ultra-high-power LED power supplies on the market, more than 4-channel drive power supplies are everywhere, so failures are frequent. In addition, due to the cost and shape of the overall design of LED street lights, multiple factors overlap, often making it difficult to maintain LED power supplies. As a result, the owners' complaints and the media's fanning of the flames have caused misunderstandings about LED street lights, affecting the industry's reputation and development.

Five concepts in the development of LED driver power supply:

1. Abandon high power and ultra-high power, and develop small and medium power power supplies with higher stability, preferably between 30W and 40W, and the maximum should not exceed 50W.

Because the greater the power, the greater the heat generated, the more compact the components inside, which is not conducive to heat dissipation, and temperature is the culprit of power supply failure. In addition, small-power power supplies are relatively mature and have advantages in stability and cost. In fact, many power supply companies know that the greater the power, the more difficult it is to make, and they are unwilling to make high-power power supplies. However, under the pressure of application manufacturers, they passively develop high-power power supplies. Many solutions have not been verified by time and practice. They are all hastily launched projects and experimental products, so failures are endless. In contrast, small and medium-power power supplies have been developed earlier, and the technical solutions are much more mature.

Furthermore, high-power and ultra-high-power power supplies are not flexible to install due to their large size, while small and medium-power power supplies are more flexible to install due to their small size.

2. Abandon more than 4 outputs and develop single or dual outputs; abandon large current and ultra-large current and develop small current.

The more output channels there are, the harder it is to make and the higher the failure rate. So far, no power supply manufacturer can stand up and say: "Under the premise of today's stringent cost requirements, more than 4 channels of drive are guaranteed to be no problem."

The more output paths there are, the greater the total output current will be. Current is the main reason for heating. Voltage may not generate heat, but current will generate heat. And simple calculation shows that the heating power is proportional to the square of the current. That is to say, if the current increases to 2 times, the heating power will increase to 4 times. If the current increases to 3 times, the heating power will increase to 9 times. So I suggest that the current should be controlled below 1A.

3. Intelligent control should be one of the biggest advantages of LED lamps, and intelligent control means intelligent control of power supply.

Intelligent control is particularly important in street lamp and tunnel lighting applications. For street lamps, intelligent control can achieve stepless control of lamp power in different time periods according to the density of road traffic, which not only meets application requirements but also achieves energy-saving effects. Its application in tunnel lighting is even more important, as it can automatically adjust the brightness of tunnel entrances and exits according to the brightness outside the tunnel, providing drivers with a safe driving environment.

4. Heat dissipation and protection are the main external factors of power supply failure.

Not only the power supply itself will generate heat, but also the lamp will generate heat. How to dissipate these two heat sources reasonably is a problem that lamp design engineers must consider. It is necessary to prevent excessive concentration of heat, which will form a heat island effect and affect the life of the power supply. In addition, protection is also very important. Water penetration may cause a short circuit in the power supply, and dust on the outer shell will affect the heat dissipation of the power supply. Exposure to the sun can easily cause high temperature and aging of wires and other components. Protection is actually to solve this series of problems.

5. Feasibility of maintenance.

Although we have done enough work in the first four steps, it is still impossible to completely avoid power failures, which is why we propose the feasibility of maintenance. Lighting design engineers must consider the maintenance of the power supply. Only when the replacement of the power supply is as simple as the replacement of the light source of conventional lighting, can the maintenance task be transferred to the street lamp unit.

In this regard, we should work hard on the maintenance of lamps, and designers should regard themselves as maintenance workers and require the simpler the better. In actual use, the failure rate of rotating wiring plugs is relatively high, and most of the failures are caused by water leakage. Everyone has realized the reasonable design method of modularization, and should think of ways to integrate the modular power supply, because the overall power of modularization is relatively small. If the power supply can be plugged in to solve the maintenance problem, the street lamp unit will have to stock the power supply (not to doubt some of the current power supplies but relative to the life of LED light sources), and both the enterprise and the owner will benefit.

In summary, although most LED lamp failures occur in the power supply, we cannot simply blame the power supply companies. Power supply failure is the result of a combination of multiple factors, many of which are caused by unreasonable designs by lamp companies. To effectively reduce power supply failures, it is necessary for power supply companies and lamp companies to strengthen interaction and work together!