The difference between isolated power supply and non-isolated power supply

The isolation and non-isolation of power supply are mainly for switching power supply. The more common view in the industry is:

    1. Isolated power supply: There is no direct electrical connection between the input circuit and the output circuit of the power supply. The input and output are in an insulated high-impedance state and there is no current circuit.

    2. Non-isolated power supply: There is a direct current circuit between the input and output. For example, the input and output are in common ground.

Advantages and disadvantages of isolated power supply and non-isolated power supply

From the above concepts, it can be seen that for the commonly used power supply topologies, non-isolated power supplies mainly include: Buck, Boost, Buck-Boost, etc.; while isolated power supplies mainly include various flyback, forward, half-bridge, LLC and other topologies with isolation transformers.

    Combining the commonly used isolated and non-isolated power supplies, we can intuitively derive some of their advantages and disadvantages, and the advantages and disadvantages of the two are almost opposite.

To use isolated or non-isolated power supplies, you need to understand what the actual project's demand for power is, but before that, you can understand the main differences between isolated and non-isolated power supplies:

    1. The reliability of the isolation module is high, but the cost is high and the efficiency is poor.

    2. The structure of non-isolated modules is very simple, with low cost, high efficiency and poor safety performance.

Therefore, it is recommended to use isolated power supply in the following occasions:

    1. In situations involving possible electric shock, such as taking power from the power grid and converting it into low-voltage DC, an isolated AC-DC power supply is required;

    2. The serial communication bus transmits data through physical networks such as RS-232, RS-485 and controller area network (CAN). Each of these interconnected systems is equipped with its own power supply, and the systems are often far apart. Therefore, we usually need to isolate the power supply for electrical isolation to ensure the physical safety of the system, and to protect the system from transient high voltage shocks and reduce signal distortion by isolating and cutting off the ground loop;

    3. For external I/O ports, in order to ensure the reliable operation of the system, it is also recommended to isolate the I/O ports for power supply.

Application scenarios of isolated and non-isolated power supplies

By understanding the advantages and disadvantages of isolated and non-isolated power supplies, we can know that they each have their own advantages. For some commonly used embedded power supply options, we can make accurate judgments:

    1. For the power supply of the front stage of the system, in order to improve the anti-interference performance and ensure reliability, an isolated power supply is generally used.

    2. For the power supply of IC or part of the circuit in the circuit board, non-isolated solutions are preferred from the perspective of cost performance and volume.

    3. In situations where safety is required, such as AC-DC that needs to be connected to the mains, or power supply for medical use, isolated power supplies must be used to ensure personal safety. In some situations, power supplies with enhanced isolation must also be used.

    4. For the power supply of remote industrial communications, in order to effectively reduce the impact of ground potential difference and wire coupling interference, isolated power supplies are generally used to power each communication node separately.

    5. For battery-powered occasions with strict requirements on endurance, non-isolated power supply is used.