In the medical industry, due to the safety of personnel, all related products will give priority to quality. In this case, how should we choose medical power?
As we all know, each industry has a certain hard power supply indicator, and the medical industry is no exception. In order to be able to use the power supply in medical devices, the corresponding medical certification indicators must first be passed.
1. Requirements for the ECM indicator:
The conduction and radiation of medical equipment needs to meet EN55011 with the same limits as the EN50552 Ite equipment. Considering that the medical system must meet the requirements of high safety and high isolation, and the transmission and radiation are required to meet the standard requirements, this is a great test for the design of the power supply. The designer must ensure high isolation and EMI in the design. It's actually a very difficult thing to do well, so many medical devices have to compromise, and only require EMI performance to meet the CLASSA level.
2. Safety distance and pressure resistance:
The medical standard is different from the conventional certification. In order to ensure safety and reliability, the safety distance and pressure requirement of the system are clearly defined in the standard. These distance and pressure requirements are differentiated according to the application and the crowd, and are classified according to the protection method. MOPP (Patient Protection Method) and MOOP (Operator Protection Method) are further classified into Class B, Class BF, and Class CF according to the type of equipment. Taking into account the versatility of the module, medical power engineers usually meet the most demanding requirements in the design process, as follows: 1L, N to PE 1500VAC isolation, clearance of 2.5mm, creepage distance of 4.0mm. 2 The primary side of the transformer is 4000VAC to the secondary side, the clearance is 5mm, and the creepage distance is 8mm. 3 output to PE, 500VDC (floating), clearance of 2.5mm, creepage distance of 4mm.
3. Ultra low leakage current requirements:
Low leakage current is the core indicator of medical power supply. IEC requirements are 264VAC, 50Hz, leakage current ≤500uA under normal state of medical equipment, but medical equipment is usually far more than one isolated power supply. Some large CTs even have 5 channels or even Above the power supply. Therefore, for the power supply manufacturer, the leakage current of a power module can preferably be ≤100uA. For the DCDC power supply that is in contact with the human body, because it is in direct contact with the human body, the isolation requirements are more demanding, especially for CF-type equipment that is in contact with the heart. The medical certification clearly requires ≤10uA.
4. Grounding continuity requirements:
The reason why medical power supply has this requirement is mainly because when the grounding resistance is large, it is easy to cause the ground potential difference of different power supply devices to be large, which may cause harm to seriously ill patients. Therefore, grounding continuity must also be rigorously tested. The IEC requires the resistance of the PE to any accessible metal of the housing to be <0.1Ω.
5. Other requirements:
In addition to the above general requirements, medical equipment also needs to meet all the requirements of conventional civilian appliances. If it is required to meet the requirements of ROHS, the temperature that can be reached by human hands must meet the requirements of conventional standards, etc., and is not listed in detail.