LED isolation and non-isolation solutions

At present, in the general LED lighting market, there is a distinction between non-isolated design and isolated drive power. Non-isolated design is limited to double insulation products, such as replacement products for light bulbs, where the LED and the entire product are integrated and sealed in non-conductive plastic, so the end user does not have any risk of electric shock. Secondary products are isolated and relatively expensive, but where users can access the LED and output wiring (usually in the case of LED lighting and street lighting applications), this product is indispensable.

The LED drive power supply with isolation transformer or electrical isolation means that the LED can be directly touched by hand without electric shock. Although the LED drive power supply without isolation transformer can still achieve partial mechanical insulation with the help of the protective casing, the LED at this time cannot be directly contacted when it is working.

The physical design determines whether the drive is isolated or non-isolated. Security rules usually require the use of two separate isolation layers. The designer can choose two kinds of physical isolation layer, namely plastic diffuser cover and glass cover, and use non-isolated power supply. If the cost of physical isolation is too high, there are mechanical difficulties, or too much light is absorbed, electrical isolation must be addressed in the power supply.

Isolated power supplies are usually larger than non-isolated power supplies of the same power level. Lighting designers must carry out a lot of cost and design optimization work in each product they design. As it is suitable for different applications, whether to use an isolated insulating transformer or an isolated protective lamp housing, designers will always have different opinions from different perspectives.

Usually, they will analyze from many aspects, such as cost and manufacturing process, efficiency and volume, insulation reliability and safety specification requirements, and so on. The cost of driving with a transformer is higher, but it also makes LED lamps more practical and can meet the needs of end users who occasionally touch LEDs. When the glass envelope of the incandescent lamp is easily damaged, an ordinary bulb of the E27 model can be replaced with an LED lamp.

In addition, the lamps used in industrial areas or office equipment applications do not need to contact end users, such as street lamps and shopping malls. At this time, LED lamps do need isolation transformers.

As a product that end users can use safely, the reliability of insulation and isolation must be considered. As a complete product, the parts on the surface of the product accessible to users must be isolated to prevent electric shock. As far as the entire system of the product is concerned, isolation is inevitable, and the only difference is the location where the isolation is set. Some designers use an isolated transformer design, so they can simplify the heat dissipation and lampshade design. If a non-isolated drive design is used, reliable insulation requirements must be considered in the lamp housing and other structures. Therefore, as a power drive, both isolated and non-isolated solutions have always existed at the same time.

The main challenge that Chinese LED driver power manufacturers may face is to find low-cost AC/DC drivers to meet the requirements of achieving more stringent power factor and efficiency performance in low-cost power systems. In the future, the use of high-quality, high-reliability power supplies in systems with limited space and difficult heat dissipation (such as LED lamps) will no longer be free. However, before the end user has used many bulbs with a lifespan of about 10,000 hours, it is quite difficult to prove its high quality.

Several trends are currently driving the development of the LED lighting market. The first is the continuous improvement of high-brightness LED efficiency and the continuous emergence of very high-efficiency and high-reliability constant current LED driving power supplies. If it does, it will release mercury, which is harmful to the environment). The combination of these factors is making LED lighting a long-term development trend. Of course, low system costs (including LEDs, thermal management systems and LED drivers) will always be the driving force behind the widespread adoption of LED general lighting by consumers.

In fact, in many LED lighting products, failure is a common phenomenon, most of which are due to the failure of the power supply, rather than the failure of the LED. At the design level, this means that OEMs must become experts in system thermal design. LEDs provide high efficiency, but they also generate more conduction heat than incandescent or energy-saving lamps.

Since many LED lighting applications are enclosed in a small space, it is difficult to use ventilation to dissipate heat. Without careful thermal design, LEDs and power supply drive circuits are prone to degradation or permanent failure due to high temperatures.