The difference between isolated and non-isolated drivers

2023-02-16

Non isolated drive power supply: the mains electricity directly inputs power to the circuit board and then output through electronic components to reduce voltage. The input and output terminals are not electrically isolated through transformers

What is non-isolated driver：
Non isolated drive power supply: the mains electricity directly inputs power to the circuit board and then output through electronic components to reduce voltage. The input and output terminals are not electrically isolated through transformers, but directly connected through electronic components. The input and output share the same negative pole of the power supply. Therefore, touching the shell or load, etc., may lead to the risk of electric shock. The light source board and the drive board are separated.

What is a isolated driver：
The mains electricity directly inputs power to the circuit board, and then the high voltage is converted into low voltage through electronic components and transformers. The input and output are electrically isolated through transformers. The energy conversion process of transformers is electric-magnetic-electric method. (Electrical energy is converted into magnetic energy and then magnetic energy is converted into electrical energy). The input and output do not use the negative pole of the same power supply, so there is no risk of electric shock and good security. The light source board and the drive board are separated.

Comparison of non-isolated and isolated solutions

Non-isolated solution features	Isolated solution features
Conversion efficiency 90%-93%	Conversion efficiency 88%
Small size and relatively low cost	Larger size and relatively high cost
High voltage input and output, extra insulation	Good safety performance with electrical isolation
Relatively inferior anti-interference capability	Better anti-interference ability
Relatively simple power supply design	Complex power supply design
The beads are easy to be damaged under abnormal power supply.	The beads won’t be affected under abnormal power supply.
Wide voltage input 100V-265V generally	Wide voltage input 85V-265V generally
Output high voltage and small current generally	Output high current and low voltage generally

How to distinguish between non-isolated, isolated and other solutions
First of all, we can distinguish non-isolated, isolated or DOB and linear solutions from whether the power driver and light source board are separated or not. If the power driver and light source board is separate, it is either non-isolated or isolated solution. And then we can determine whether it is non-isolated or isolated from the following points:
1. Generally speaking, non-isolated solution has two electrolytic capacitors while isolation has three electrolytic capacitors. Two of them are same. One rectifies as a filter, and the other parallels lamp beads connected to the output. The isolated third electrolytic capacitor is generally next to the chip, which is small and used to maintain power supply for the chip, so it can be judged by the third electrolytic capacitor
2. Non-isolated power supply output electrolytic capacitors generally have high withstand voltage and small capacitance, while the isolated power supply output electrolytic capacitors generally have small withstand voltage and large capacitance. We can also judge by this point.
3. Non-isolated power supply uses inductor while isolated uses transformer which is composed of multiple inductors. Generally, the inductance has only one group of copper wires, while the transformer has multiple groups of copper wires. We can also judge by this point.
4. The isolated power supply sometimes has a Y capacitor near the transformer, and sometimes we can be judged by this component.
5. Generally, under the same power, the size of non isolated inductance will be smaller than that of isolated transformer.