Safety
Isolation power supplies utilize transformers to step down 220V voltage to a lower level, then rectify it into direct current for power supply. Since the primary winding of the transformer withstands the 220V voltage, the secondary winding only handles the lower AC output voltage, and the primary and secondary windings are not directly connected, hence the name "isolation power supply." The transformation process is electric-magnetic-electric, and as it is not connected to the ground, there is no risk of electric shock. Non-isolation power supplies input 220V directly into the electronic circuit, which is then stepped down through electronic components for output. Since the input and output are directly connected through electronic components, they are called non-isolation power supplies; the difference between the two is essentially whether a transformer is used or not. Non-isolation LED designs are limited to double-insulated products, such as replacement bulbs, where the LED and the entire product are integrated and sealed in non-conductive plastic, ensuring that end-users are not at risk of electric shock. Second-level products are all isolated, which are relatively expensive. Non-isolation circuits directly apply the input power, after voltage adjustment, to the LED load, posing a risk of electric shock. Therefore, to pass safety certifications such as 3C, UL, and CE, non-isolation can be problematic, as many manufacturers lack the design and technical capabilities, making it difficult to pass. Because of insufficient insulation and creepage distances, the design must focus on the physical structure of the lamp. Tube lights are acceptable, and there are also all-plastic ones, where the insulation between the LED and the aluminum heat sink typically relies on the thin film insulation of the printed circuit board on the aluminum substrate. Although this insulation layer can withstand 2000V high voltage, sometimes burrs in the screw holes can cause what is known as creepage, making it difficult to pass the CE certification. However, as a complete LED lighting product, any part of the product that the end-user can touch must be isolated to prevent electric shock. In terms of the entire product system, isolation is unavoidable; the difference lies in the placement of the isolation. As a product designed for safe end-user use, the reliability of insulation and isolation will always be considered. Note: Big Hero reminds you that some manufacturers, to save costs, use a method of directly tapping off low voltage from the primary winding, which appears to have a transformer but actually lacks a secondary winding and cannot be considered an isolation power supply!
Electrical Performance
In terms of performance, the advantages of isolated power supplies include: they pose no threat to human health, exhibit excellent performance across a wide voltage range, and non-isolated options are now quite mature. The voltage range for non-isolated supplies is slightly narrower than that of isolated ones, spanning 110V-300V, while isolated power supplies can handle 60-300V with very even current flow. Isolated drivers are safe but less efficient, while non-isolated drivers are more efficient, and the choice between the two should be based on actual usage requirements. In terms of constant current accuracy, isolated drivers can achieve ±5% or better, whereas non-isolated drivers struggle to reach such precision. Non-isolated circuits are highly sensitive to surges and have poor suppression capabilities. Lightning-induced voltage surges are short-lived, high-voltage spikes reaching thousands of volts, with immense energy. When this voltage enters the power supply, it can instantly reach the output for non-isolated BUCK circuits, damaging the constant current detection loop or further damaging the chip, potentially causing a 300V direct connection and burning out the entire light tube. In fact, this refers to non-isolated power supplies, which have a higher repair rate during mass production than isolated LED driver power supplies, primarily due to explosions. However, isolated power supplies have a much lower chance of exploding, with non-isolated ones generally around 2% to 3%. Many power grids have unstable voltages, including isolated ones, and the phenomenon is that chips, MOSFETs, and constant current loops can all be burned out, but isolated ones are much less frequent. Note: Therefore, surge protection for non-isolated circuits with voltage-sensitive resistors is essential; without surge protection, quality assurance is mere fog. Aviation ground power: 2, 36V aviation power supply: 1, 400Hz frequency conversion power supply: 7, 115/200V power supply: 2, 27V DC power supply: 5, 400Hz power supply: 12, aviation power supply
Cost and Efficiency
Electronics cost encompasses not only design and production expenses but also includes maintenance costs for high-volume products. Regarding LED power supply circuit structures, the current isolated solutions are predominantly AC/DC flyback circuits, which are relatively complex and costly. Non-isolated options typically employ DC/DC boost or buck circuits, which are simpler and thus less expensive. Non-isolation reduces transformer energy loss, allowing for efficiency of 90% or more, along with higher power factors. Isolated sources generally have an efficiency of 88%, depending on power levels, and tend to generate more heat. Non-isolated sources have a cost and efficiency advantage over isolated ones. Isolated sources are challenging to optimize for high efficiency; if not handled well, they generate significant heat and are more expensive, especially for LED tube lights with built-in lamps. However, non-isolated sources are more susceptible to lightning surge voltages, leading to numerous damages during large-scale shipments. Compared to isolated sources, non-isolated ones mainly reduce transformer usage, designing architectures with less material to achieve the same product functionality, resulting in a significant cost advantage. This is likely why non-isolated power sources are so popular in China. Note: For low-voltage LED lighting, prioritizing efficiency and cost, non-isolated solutions are the preferred choice.
Usage Scenario
Using an insulated transformer or an insulated protective lamp罩shell typically requires analysis from multiple aspects, such as cost and manufacturing processes, efficiency and volume, insulation reliability, and safety regulation requirements. Both types of designs will continue to be used as each meets different market demands. In terms of load range, the output load range of isolated power supplies is generally 30-42V, while non-isolated load ranges can be 30-84V. Many LED manufacturers require power supplies to be adaptable to a full voltage input of 90-265V for overall compatibility, and the load range is also required to reach 84V. This choice carries certain risks and hazards. At 90V input, the power supply may lose constant current function, THD, and other issues. Non-isolated power supplies are suitable for high voltage, low current applications, and are not cost-effective for high current applications compared to isolated ones. Non-isolated power supplies are suitable for indoor lighting, where the electrical environment is better, surge impacts are minimal, and applications include hats and surface-mount LEDs. Using non-isolated for high voltage, low current and low voltage, high current is unnecessary since non-isolated efficiency is not higher and costs are not much lower, making them unsuitable for centralized lighting. Centralized lighting refers to placing hundreds of lighting fixtures on the same AC line, where the voltage environment is dirty due to the high number of fixtures on the line, increasing the likelihood of fixture damage. From the perspective of the entire product system, insulation is inevitable, with the difference being the location of the insulation. Some designers adopt insulated transformer designs, allowing for simplified heat dissipation and lampshade design. Non-insulated drive designs require reliable insulation considerations in structures like lampshades. Note: Both isolated and non-isolated power supply solutions have always coexisted as power drivers. Due to the above points, each power supply architecture has its advantages. Non-isolated power supplies focus on higher power factor and efficiency, reducing energy loss, while isolated power supplies emphasize life safety and the overall safety of fluorescent lamps, slightly underperforming in power factor and efficiency compared to non-isolated power supplies. Different power supply types have no rigid regulations depending on different scenarios and usage environments. Aviation ground power supply 2, 36V aviation power supply 1, 400HZ inverter power supply 7, 115/200V power supply 2, 27V DC power supply 5, 400HZ power supply 12, aviation power supply
