【Medical Power Supply】Challenges and Countermeasures for Waterproof Requirements

With the rapid popularization of home care medical products, the environments where  medical products are being used have also become more and more complicated. For example, ventilators and humidifiers are gradually being used in homes now. When they are used in environments with higher humidity, they might also get splashed or drenched by water inadvertently from time to time. As for power supply products that supply power to medical equipment, not only do they need to provide power for the equipment, they must also have some level of waterproof capability in order to ensure the safety of users and internal electrical equipment. Therefore, as an important reliability index for medical power supply products, people have started paying attention to the waterproof performance of IPX2.

In reference to related definitions of IEC 60529 by the International Electrotechnical Commission, protection levels are represented in the IPXX format where IP is short for Ingress Protection, and IPXX is the definition of the protection ability of the enclosure of electrical equipment against the intrusion of foreign objects. The XX is the IP level as two Arabic numbers; the first number represents the protection level against solids and the second number represents the protection level against liquids. There are 7 levels for the protection against solids (dust-proof level), which are represented with 0-6, and there are 10 levels of the protection against liquids (waterproof level), which are represented with 0-9. Refer to the following table for details:

Number	First number – dustproof	Second number – waterproof
0	No protection	No protection
1	Foreign object detector that protects against solids with diameters of 50mm or more; the diameter of the sphere is 50mm and larger foreign objects are prevented from entering fully	Water droplets that fall vertically should not cause damage Drip amount 1.0±0.5mm/min Duration: 10 mins
2	Foreign object detector that protects against solids with diameters of 12.5mm or more; the diameter of the sphere is 12.5mm and larger foreign objects are prevented from entering fully	When the product is tilted up at 15 degrees, water droplets that fall vertically should not cause damage Drip amount 3.0±0.5 mm/min Duration: 4 x 2.5 min (10 mins in total)
3	Foreign object detector that protects against solids with diameters of 2.5mm or more; the diameter of the sphere is 2.5mm and larger foreign objects are prevented from  entering fully	Protected against spraying water, water sprayed at an angle up to 60 degrees on either side of the vertical surface of the enclosure will have no harmful effects.
4	Foreign object detector that protects against solids with diameters of 1.0mm or more; the diameter of the sphere is 1.0mm and larger foreign objects are prevented from entering fully.	Protected against splashing water, water splashed against the enclosure from any direction will have no harmful effects.
5	Dust-protected Ingress of dust is not totally prevented, but the amount of dust which enters will not cause damage to the equipment	Protected against water jets, water projected in jets against the enclosure from any direction will have no harmful effects. (Continual low-pressure water jets for at least 3 minutes)
6	Dust-tight No dust should enter the cabinet when it is at a low pressure of 20 mbar Dust-proof	Protected against powerful water jets, water projected in powerful jets against the enclosure from any direction will have no harmful effects. (Protects against at least 3 minutes of continual powerful water jets)
7	NA	Protected against the effects of temporary immersion in water, ingress of water in quantities causing harmful effects will not be possible when the enclosure is temporarily immersed in water under standard conditions of pressure and time.
8	NA	Protected against the effects of continuous immersion in water, Ingress of water in quantities causing harmful effects will not be possible when the enclosure is continuously immersed in water under conditions which shall be agreed between manufacturer and user but which are more severe than for numeral 7.
9	NA	Protected against the effects of high-temperature powerful water jets. Water projected in high temperature/powerful jets against the enclosure from any direction will have no harmful effects.
Examples of IP levels: IPX2 means not indicating the dustproof level but satisfying level 2 of the waterproof level IP2X means not indicating the waterproof level but satisfying level 2 of the dustproof level IP21 means satisfying level 2 of the dustproof level and level 1 of the waterproof level.

As we all know, waterproofing has certain challenges for the structural design and manufacturing of electrical products. For power supply products, the key to waterproofing lies in the tightness of the   exterior components of the power supply and the stability of the manufacturing quality when considering from the design and manufacturing perspectives.

When we analyze the assembly of the external components of a power supply showed in the figure below, the following four positions are most critical:

To ensure the tightness of the positions described above, APD used methods that passed DFSS and DOE for designing and manufacturing. APD conducted in-depth research and verification to design and develop manufacturing methods with reliable product structures and stable qualities based on complete quality control systems. This ensures the waterproof performance of their overall products. APD also obtained patent design approval for different products structures.

 

No.	Position	Challenges in waterproof design	APD waterproof design solutions
1	The LED light hole position	1. Plastic deformation of the LED panel 2. Corresponding gap between the LED and case too large/too small;	1. Special LED structure (APD patent) 2. Used DFSS tools to find an optimized design solution 3. Implemented complete design specifications as the guide.
2	Case assembly surface	An insufficient volume ratio of ultrasound structure Waterproof surface not on the same level The waterproof surface has a discontinuous structure Must consider the tolerance of ultrasound compression articulation	Special design of the ultrasonic wire structure Scientific calculation of area ratio range and defining reasonable tolerance to ensure there will be no excessive glue issue while being connected Used DOE tools to find key factors and performed control guidelines for the key factors to ensure mass production consistency
3	AC input socket position	AC socket size tolerance; Must consider the tolerance of ultrasound compression articulation	Special mechanical design to ensure proper sealing Used DOE tools to find key factors and performed control for the key factors to ensure mass production consistency
4	Output cable SR position	Matching gap between SR and CASE Excessive glue for SR lamination Must consider the tolerance of ultrasound compression articulation	Special structural design that ensures both tightness and excessive glue issues Reasonable parameter control that takes care of both material flexibility and cable swing performance

Also, to ensure that the products meet the waterproof demand requirements, APD established standard test equipment testing capabilities and complete product design/manufacturing process/test specifications. Through effective implementation, the reliability of products is ensured.

What needs special attention is that if the products are sealed too completely, the water vapor or gas inside cannot be released easily, and this will also cause a series of problems such as swollen power, etc. In light of this, APD used its years in developing medical power supply to effectively avoid other negative effects caused by this. APD ensures that our products meet waterproof design requirements, providing you with medical power supplies  that havethe most reliable waterproof designs.