The difference between isolated and non-isolated driving power supply in LED

Currently in the general LED lighting market, there are non-isolated designs and isolated drivers.

Non-isolated designs are limited to double-insulated products, such as bulb replacements, 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 all isolated and relatively expensive, but they are essential in places where users can access the LED and output wiring (usually in the case of LED lighting and street lighting applications).

LED drivers with isolation transformers or electrical isolation mean that the LED can be touched directly by hand without electric shock. Although LED drivers without isolation transformers can still achieve partial mechanical insulation with the help of protective housings, the LEDs cannot be directly touched during operation.

Insulated light bulbs will become the mainstream in the future.

Physical design determines whether the driver is isolated or non-isolated. Safety regulations usually require the use of two independent isolation layers. Designers can choose between two physical isolation layers, plastic diffuser and glass shield, and use a non-isolated power supply. If physical isolation is too expensive, mechanically difficult, or absorbs too much light, 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 perform a lot of cost and design optimization work in each product they design.

Due to different applications, whether to use an isolated insulation 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 regulations, etc.

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 come into contact with LEDs. When the glass shell of an incandescent lamp is easily damaged, an ordinary E27 bulb can be replaced with an LED lamp. In addition, lamps in industrial areas or office equipment applications do not need to come into contact with end users, such as street lamps and shopping mall lighting. At this time, LED lamps do need isolation transformers.

As a product that can be used safely by end users, the reliability of insulation and isolation must be considered. As a complete product, the part of the product surface that users can touch must be isolated to prevent people from getting electric shock. As for the entire product system, isolation is inevitable, the only difference is the location of the isolation. Some designers use isolated transformer design, so they can simplify the design of heat dissipation and lampshade. If a non-isolated drive design is used, reliable insulation requirements must be considered in the structure of the lamp housing. Therefore, as a power drive, isolation and non-isolation solutions have always existed at the same time.

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

Transformer-based isolated LED driver power supply will be the mainstream.

Both isolated and non-isolated LED driver solutions have their own advantages and disadvantages. We believe that Class II will be the mainstream because it simplifies the LED heat dissipation problem. Class I or II systems rely on a grounding system, which in most cases is closely related to the installation location. Class II is more common and requires double-stage or reinforced isolation, which requires transformer magnetic windings, insulation tape and physical isolation. Class I systems require a grounded enclosure and/or mechanical barriers, which are not required for Class II systems.

There are several trends 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, high-reliability constant-current LED drivers. The second is global legislation to ban incandescent lighting (due to its low efficiency) and the gradual fading of CFL energy-saving lamps (if broken, it will release mercury that is harmful to the environment). These factors combined are making LED lighting a long-term development trend. Of course, low system cost (including LEDs, thermal management systems and LED drivers) will always be the driving force for consumers to widely adopt LED general lighting.

In fact, failure is a common phenomenon in many LED lighting products, most of which are caused by power failure rather than LED failure.

At the design level, this means that OEMs must become experts in system thermal design. LEDs offer high efficiency, but they also generate more conductive heat than incandescent or CFL lamps. Since many LED lighting applications are enclosed in a small space, it is difficult to dissipate heat through ventilation. Without careful thermal design, LEDs and power drive circuits can easily degrade or permanently fail due to high temperatures.