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This article discusses the differences between isolated and non-isolated power supplies in detail, including the characteristics of safety, electrical performance, and cost efficiency, as well as their selection strategies in different application scenarios. It emphasizes the importance of isolated power supplies in situations involving personal safety and specific communications, and also points out the advantages of non-isolated power supplies in terms of cost and efficiency, but pays attention to their sensitivity to surges.
The knowledge you need to know about LED power supply
Isolated Power supply
Isolated power supply is a power supply system with electrical isolation between input and output. It forms electrical isolation between the input circuit and the output circuit through isolation components such as transformers and optocouplers, cuts off the direct current path, and thus provides a safe power supply.
The working principle of an isolated power supply mainly relies on the transformer. When the AC signal enters the transformer, there is no direct electrical connection between the primary coil and the secondary coil, so there will be no electrical connection between the load connected to the output and the input. The insulation layer of the transformer ensures the electrical isolation between the input and output, thus achieving a safe power supply. In addition, the isolated power supply may also use other isolation components (such as optocouplers) to achieve electrical isolation.
A non-isolated power supply is a power supply system that has no direct electrical isolation between the input and output. The input circuit and the output circuit share the same ground or connection, and there is no physical insulation isolation.
2. Operating principle of Isolated power supply
The working principle of a non-isolated power supply is relatively simple. It usually directly converts the input voltage to the required output voltage. This conversion process is usually achieved through electronic components (such as rectifiers, regulators, filters, etc.) without using isolation components such as transformers. Therefore, there is a direct electrical connection between the input and output of a non-isolated power supply, and there is no electrical isolation.
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Isolated Power Supply Vs. Non-isolated Power Supply
The isolated power supply uses a transformer to reduce the 220V voltage to a lower voltage and then rectifies it into a low-voltage DC output for the power supply. Because the primary coil of the transformer bears the 220V voltage, the secondary coil only bears the output low voltage, and the primary and secondary coils are not directly connected, and are not connected to the ground, so there is no risk of electric shock.
Non-isolated power supplies are relatively less safe because there is no electrical isolation between the input and output. If a short circuit or leakage occurs at the output, the current may flow back into the power grid through the ground wire, causing an electric shock accident. In addition, non-isolated power supplies are also susceptible to external factors such as ground interference and lightning strikes, causing equipment damage or failure.
Compared to the Isolated drivers, non-isolated power supplies are difficulty to pass the CE, UL certification
For an Isolated LED power supply, the input voltage is AC60-300V, and the output voltage range is DC 30-42V.
For a Non-isolated LED power supply, the input voltage is AC110-300V, and the output voltage range is DC 30-84V.
Since the output voltage range of isolated power supplies is limited, non-isolated power supplies have a wider range of applications.
Non-isolated power supplies have less energy loss from voltage transformation, their efficiency can generally reach over 90% and they have a higher power factor.
For isolated LED power supply, the efficiency is generally lower than 88%, depending on the power, and the heat generated by the isolated power supply is larger than the non-isolated power supply.
Non-isolated power supply module does not need to use a transformer for electrical isolation between input and output, so compared to the Isolated power supply, with the same output power and the same output performance (such as output accuracy, load effect, dynamic response, etc.), non-isolated power supply requires a smaller size, lower cost, less difficult to design.
In low-voltage powered LED lighting, with efficiency and cost prioritized, the non-isolated power supply is actually the best choice.
| Advantage | Disadvantage | |
| Isolated LED driver | Strong anti-interference ability | Low conversion efficiency |
| Easy to implement buck-boost conversion | Big size | |
| Wide input voltage range and multiple outputs | High cost | |
| High safety performance | Complex design | |
| Non-isolated LED driver | High conversion efficiency | Poor anti-interference ability |
| Small size | Difficult to implement buck-boost conversion | |
| Low cost | Narrow input range, difficult to achieve multiple outputs | |
| Easy to design | Low safety performance |
Isolated power supplies are widely used in situations with high safety requirements due to their high safety and stability. For example:
Medical equipment: Medical equipment needs to ensure the safety of patients and medical staff, so isolated power supplies are usually used to avoid electric shock accidents.
Industrial control systems: Electronic equipment in industrial control systems require a stable and reliable power supply to prevent equipment failures caused by power fluctuations or interference. Isolated power supplies can provide a stable power supply and eliminate the impact of external interference on equipment.
Special applications: Isolated power supplies are also often used in situations with high electrical isolation requirements, such as high-frequency power supplies and laser equipment.
Non-isolated power supplies are widely used in places where safety requirements are not high due to their low cost and simple structure. For example:
Consumer electronics: Consumer electronics such as mobile phone chargers and laptop power adapters usually use non-isolated power supplies to reduce costs and improve efficiency.
Household appliances: Household appliances such as electric fans and electric kettles are also often powered by non-isolated power supplies. These devices usually do not require too high electrical isolation requirements, and low-cost non-isolated power supplies can meet their needs.
Isolated power supply and non-isolated power supply are two common types of power supply design, with different characteristics and application scenarios in terms of electrical safety, ground loop, cost, and efficiency. Isolated power supply improves electrical safety and anti-interference performance by realizing electrical isolation of input and output ends; while non-isolated power supply is simpler and less expensive, suitable for some application scenarios that do not require high isolation performance.
When choosing a power supply design, it is necessary to weigh various factors and choose the most suitable type according to the specific application needs and requirements. Whether it is an isolated power supply or a non-isolated power supply, it should meet the design requirements as much as possible while ensuring the stability, safety, and reliability of the system, and considering the overall performance and cost-effectiveness of the system.
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