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The ventilator power supply safety testing requirement


The ventilatoris a medical device product, that is why some additional tests will be added in terms of ventilatoris power supply safety testing requirement as following:

The ventilator is a medical device product, that is why some additional tests will be added in terms of safety testing requirement as following:

1. Requirements for EMC indicators:
It is asked to be met EN55011 standard of medical equipmen's the conduction and radiation.  The limits are the same as EN50552 ITE equipment. Considering that the medical system must meet the requirements of high safety and isolation, conduction and radiation must also meet the standard requirements. This is a big test for the design of the power supply. The designer must ensure high isolation and EMI in the design. It is actually very difficult to do well, so many medical devices have to compromise, and only require EMI performance to meet the CLASSA level.

2. Safety distance and withstand voltage:
Medical standards are different from conventional certifications. In order to ensure safety and reliability, the standards clearly specify the system’s safety distance and pressure resistance requirements. These distance and pressure requirements will be differentiated according to the application and the population, and divided into protection methods MOPP (patient protection method) and MOOP (operator protection method) are divided into B, BF, and CF according to the type of equipment. Considering the versatility of the module, the medical power supply engineer usually meets the most demanding requirements as much as possible during the design process, as simple as the following:
L&N are isolated from PE 1500VAC, electrical clearance: 2.5mm, creepage distance: 4.0mm;
The primary side of the transformer is 4000VAC to the secondary side, the electric gap: 5mm, and the creepage distance: 8mm.
Output to PE, 500VDC (floating), electrical clearance 2.5mm, creepage distance 4mm.

3. Requirements for ultra-low leakage current:
Low leakage current is the core indicator of medical power supply. The IEC requirement is to test 264VAC, 50Hz, leakage current ≤500uA for medical equipment under normal conditions. However, medical equipment usually has more than one isolated power supply. Some large CTs even have 5 channels or even Power supply above. Therefore, the leakage current of a power supply module should be ≤100uA for power supply manufacturers. For post-level DC to DC power supplies that are in contact with the human body, because they are in direct contact with the human body, the isolation requirements are more stringent, especially for CF devices that are in contact with the heart, the medical certification clearly requires ≤10uA.

4. Requirements for grounding continuity:
The reason why medical power supplies have requirements for this index is mainly because when the ground resistance is large, it is easy to cause the ground potential difference of equipment powered by different power sources to be large, which may be harmful to patients with serious illness, so grounding continuity must also be strictly tested , IEC requires that the resistance of PE to any metal part of the shell<0.1Ω.

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