power are mainly for switching power supplies. The more common views in the industry are:
① Isolated power supply: There is no direct electrical connection between the input circuit and the output circuit of the power supply. There is an isolated high-impedance state between the input and output, with no current loop.
②Non-isolated power supply: There is a direct current loop between the input and output, for example, the input and output are in common ground.
2. The advantages and disadvantages of isolated power supply and non-isolated power supply
can be seen from the above concepts. For common power supply topologies, non-isolated power supplies mainly include: Buck, Boost, Buck-Boost, etc.; while isolated power supplies mainly include various types with isolation transformers. Flyback, Forward, Half Bridge, LLC and other topologies.
Combining the commonly used isolated and non-isolated power supplies, we can intuitively draw some of their advantages and disadvantages, and the advantages and disadvantages of the two are almost opposite.
When using an isolated or non-isolated power supply, it is necessary to know what the actual project requires for the power supply, but before that, you can understand the main differences between isolated and non-isolated power supplies:
① The isolation module has high reliability, but high cost and efficiency almost.
② The structure of the non-isolated module is very simple, with low cost, high efficiency and poor safety performance.
Therefore, it is recommended to use an isolated power supply in the following occasions:
① For occasions involving possible electric shock, such as taking power from the power grid and converting it to low-voltage DC, an isolated AC-DC power supply is required;
② The serial communication bus is connected through RS- 232, RS-485, and Controller Area Network (CAN) and other physical networks to transmit data, each of these interconnected systems is equipped with its own power supply, and the systems are often far apart, so 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;
③For external I/O ports, in order to ensure the reliable operation of the system, it is also recommended to I/O ports do power isolation.
3. Application of isolated and non-isolated power supply
By understanding the advantages and disadvantages of isolated and non-isolated power supply, we can see that they have their own advantages. For some commonly used embedded power supply options, we can make accurate judgments:
① The front stage of the system Power supply, in order to improve anti-interference performance and ensure reliability, isolated power supply is generally used.
② For the power supply of the IC or part of the circuit in the circuit board, the non-isolated solution is preferred from the perspective of cost performance and volume.
③ For occasions with safety requirements, if you need to connect AC-DC of the mains, or the power supply for medical use, in order to ensure personal safety, you must use an isolated power supply, and in some occasions, you must use a power supply with reinforced isolation.
④ For the power supply of long-distance industrial communication, in order to effectively reduce the influence of ground potential difference and wire coupling interference, an isolated power supply is generally used to supply power to each communication node separately.
⑤ For occasions where battery power is used and the battery life is strictly required, use non-isolated power supply.