As the keystone of one medical system, it is extremely important to select a safe and reliable Medical Power Supply. To choose the most suitable Medical Power Supply for the Medical system, the R&D engineers are strongly suggested to take, as guideline of selection, the listed criteria below into consideration
A. Electrical requirements
The input voltage range and required power should be defined for the application, as well as its output voltage and the needed current to power the application:
- Input voltage range: the most common input source is an AC source, and the range requirement is related to the destined market of the end devices. In the case of multiple market regions of the Medical system, it is strongly recommended to choose a Medical Power Supply with input voltage range covering at least the range of 100VAC to 240VAC.
- Power requirement: the required power depends mainly on the end device. It is suggested to keep in mind the derating caused by the unfavorable working temperature, as well as the potential peak current.
Output voltage and current: according to the design of the Medical system, some systems demand a constant current output while others need constant voltage. The R&D engineers should choose an adequate Medical Power Supply, with the right level and type of DC output, based on the design of the application.
As each market territory and each application field imposes its own safety regulations on the end devices, it is crucial to understand which certifications are mandatory for the application and its target market(s) during the development process.
For instance, home healthcare devices are required to meet the standards of IEC 60601-1-11, while for equipment not directly in contact with the patient, IEC 62368 might still give one the possibility to get a medical certification for medical test and measurement equipment on a system level.
Meanwhile, each country adopts its specific safety standards for the application field (e.g. UL ANSI/AAMI ES60601-1 for the US, EN 60601-1 for EU countries, CAN/CSA-C22 3rd edition for Canada…etc.
C. Installation Method
The installation of the PSU can be either internally or externally depending on how the Power Supply is designed to be integrated into the system.
- Medical Enclosed type: PSU with plastic or metal case.
- Medical PCB type: A PCB populated with components which from the power supply. Normally this solution is without any mechanical protection such as a housing. For this reason, normally installed inside an application and not touchable by the user.
- Medical On board or Medical PCB mount: PSU designed to fit on a PCB. It can be either “open frame” or “encapsulated”. The second type is potted with compound to provide protection against external elements (e.g. moisture, corrosive elements, shock, vibration…etc.).
D. Other requirements
Medical systems are regulated with extremely vigorous exigences. On top of the above criteria, it is also important to verify that the other specific requirements are met:
- Class: Class I or class II
- Heat dissipation: Forced air cooling (with fan) or Passive cooling (without fan)
- Level of protection required: 2 x MOOP, 2 x MOPP
- Leakage current
- Overload protection: Constant Current Limiting or Hiccup mode
- Remote on/off function
- Current sharing function
- Parallel function