The power module is a power converter that can be mounted directly on the printed circuit board, which is generally divided into AC to DC or DC to DC according to the conversion method. With the development of science and technology, the volume of power supplies tends to be modular and miniaturized, so there is a power module. The main circuit of the switching power supply is integrated in the chip, which can realize the functions of broadband modulation, isolation and a variety of protection.

The common basic principle consists of the following parts, the input rectifier filter, including the rectifier bridge and the input filter capacitor. Monolithic switching power supply, including power switching tube, controller and MOSFET. There are also high frequency transformer, leakage clamp protection circuit, optocoupler feedback circuit, output rectifier filter, bias circuit and other parts.

The power module can generally adapt the input voltage range of AC 85~265V or DC 100~370V through the input rectifier filter, and the frequency is 47~400Hz, and the general frequency is 50/60Hz. Because it has a small size, high integration, high cost performance and the best performance indicators, only the simplest peripheral circuit is required, with a small number of discrete components can be used. And has the advantages of high efficiency, high reliability, flexible design, etc., has become the optimal integrated circuit for the development and design of small and medium power switching power supply.

The selection of power module scheme has low technical requirements, simple design, small space occupation, high reliability, and can be changed at any time. When the product design needs to be changed, just parallel or replace the power module. Therefore, it is widely used in industrial control, machinery and equipment, ships, aerospace, communications, military, data communication, handheld electronic products, instruments and meters, LED lighting, intelligence, electric power, railway, security, mining, medical, automotive electronics and other fields.

At present, a single power module is almost difficult to pass SURGE, EFT, CE, RE and other EMC experiments, although foreign products have long life, high reliability, and good EMI control, but their anti-interference performance is still not strong enough. Most of the switching power supply is through UL and 3C certification, EMI performance is guaranteed, but the modularization is not passed because of the test EMI method, want to let the equipment through the EMC test also need to do a good peripheral circuit design.

The best choice of power module is to choose the power in the used 30-80% is appropriate, generally in this power range, its performance is stable and reliable. There are mainly commercial grade, industrial grade and military grade, and different grades have different requirements for working temperature, vibration, humidity and so on. In order to ensure the long-term stable and reliable work of the product, it is necessary to consider the actual application environment when selecting the product.