Method for solving EMC problem of medical power supply equipment

Issue Time:2019-07-02
What are the methods to solve the EMC problem of medical power supply equipment? The following is a method for solving the EMC problem of medical power supply equipment by Shenzhen Lianyunda Electronics Co., Ltd.

1, choose a medical power supply
The problem of EMC of medical power supply, 60% is caused by the quality of switching power supply. Customers must use high-quality switching power supply modules before sending inspections. The domestic switching power supply modules are uneven, many claim to have passed 3C certification. Products, when used in medical equipment, can also cause problems, especially Class B-level RE, CE testing.

Many domestic switching power supplies and medical power supplies claim that their products have passed 3C certification and there is no EMC risk (especially RE and CE issues). However, in the case of 3C certification, this type of switching power supply is generally connected to a resistive load test. Once connected to the "real load", EMC problems will be exposed. Moreover, the price war of domestic power supply modules is serious, and power supply suppliers may save EMC equipment in mass production.

Therefore, Lianyunda Electronics recommends that the sample should be sent and the medical power supply must be selected. This is one of the key factors for medical power supply equipment to pass EMC.

2, select the isolation transformer, power filter
For large medical equipment, there are generally isolation transformers and medical filters. They have very good isolation and filtering effects on surges, EFT and CE in EMC testing, which can improve the anti-jamming performance of the equipment. Choose isolation transformers, power filters, and choose a good brand.

A good power filter, even if the EMC performance of the switching power supply is not good, can at least allow the equipment to pass CE, EFT experiments, plus isolation transformers, isolation of the surge, a number of EMC testing of the product, can easily pass.

3, do a good job of shielding, through RE
Medical Charger Large medical equipment, usually a plastic case, has no inhibitory effect on the radiation disturbance generated inside the product. Therefore, Lianyunda advises customers to spray “conductive paint” on the plastic casing. Conductive paint has a great attenuation of electromagnetic disturbance. From the experience of the second, it may be as high as 20~30db, and the worst can reach 15db or less.

4, to do board-level EMC design, is the fundamental
As a senior EMC engineer knows that board-level EMC design, component or module selection is the fundamental and the most efficient and lowest cost EMC method. PCB design, mainly pay attention to suppress signal line loop, select DC/DC switching power supply module, I/O port trace, crystal oscillator trace. If the PCB design is good, even the bare board can pass the ESD, RE, Surge, EFT test, and it is not good to increase the cost. If it is matched with the appropriate switching power supply, then there is no suspense in EMC.

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