Good isolation? What is the difference between isolation and non-isolation? PK is mainly carried out from 4 aspects:
Let me first introduce what is isolation. Isolation power refers to the electrical connection between input and output through a transformer. The transformation process of the transformer is: electricity-magnetic-electricity, not connected to the earth, so there is no danger of electric shock. The non-isolated circuit is the input power directly added to the LED load after the step-up and down-voltage, which may cause electric shock.
So you have to pass UL, CE… These safety certifications, non-isolation is troublesome, the insulation and creepage distance are not enough, you can only design from the physical structure of the lamp. The lamp tube is acceptable, and there are also all-plastic, but the bulb is basically an aluminum shell, so the PCB board and the shell have to be reinforced. The space available for the bulb power supply is very small, so coupled with strict creepage requirements, complicated.
As a product that end users can use safely, the reliability of insulation and isolation must be considered.
Non-isolated, because of the less energy loss of the transformation, the efficiency can generally reach more than 91%, and there is a higher power factor. The isolation energy efficiency is generally 88%, depending on the power, so the isolated power supply generates more heat.
Non-isolated has fewer components but poorer stability, but why? The reason is that non-isolated circuits are very sensitive to surges and have poor suppression capabilities. In fact, it refers to the non-isolated power supply. When shipped in batches, the repair rate is higher than that of the isolated LED drive power supply, mostly because of explosion. The probability of explosion of isolated power supply is much smaller, and the non-isolated power supply is generally around 2% to 3%. Many grid voltages are unstable, and non-isolation will cause 300V direct output, which will damage the chip and burn out the LED load. Isolation will also occur. The phenomenon is that the chip, MOS tube, and constant current loop are all burned out, but the isolation is relatively less. Therefore, a non-isolated anti-surge varistor is indispensable, and those without a varistor energy warranty are floating clouds.
3. Cost and size
Compared with the isolated power supply, the non-isolated power supply mainly reduces the transformer, uses the least materials to design the structure, and achieves the same product function, so the non-isolated cost has a greater advantage. This is probably the reason why non-isolated power supplies are very popular in China.
4. Load range
Generally speaking, the output load range of the isolated power supply is 30-42V, and the non-isolated load range can be 30-84V. Many LED manufacturers require that the power supply can adapt to the full voltage 90-265V input when selecting the power supply for the overall adaptability, and the load range is also required to be as high as 84V. Such a choice has certain risks and hidden dangers. When 90V is input, the power supply may lose the constant current function, such as THD.
Non-isolated is suitable for high voltage and small current, and the cost of large current is not cheaper than isolation.
In a comprehensive comparison, these two power supplies have their own advantages. Non-isolated power supplies focus on higher power factor and efficiency, which reduces energy loss, while isolated power supplies focus on the safety of life and the overall safety of fluorescent lamps, in terms of power factor and efficiency. The aspect is slightly inferior to the non-isolated power supply, so different first choices are different.