Introduction to Medical Grade Power Supplies

by Jenny Olding | 13th Jun 2022

 In recent years, due to COVID-19, the need for medical devices has increased quickly, having a direct and positive impact on medical power supplies. Today we are going to introduce medical power supplies. Medical devices are strictly regulated to ensure the safety and to protect the patient and operator due to direct physical contact to the human body, the safety standard of medical power supply is based on IEC 60601-1, the required safety level standard is higher than that of ITE/industrial safety standard. The required level of insulation and leakage current is strict. We provide medical power supplies compliant to IEC/EN/UL 60601-1, indicating the product safety and quality are ensured.

      Like we mentioned previously, the first priority of medical device and power supply is safety protection. Medical devices must include at least one means of protection (MOP) to ensure both the patient and the operator are protected from the risk of electric shock, even in the condition of failure. The need of MOPs may be fulfilled by dielectric strength, creepage distance, and air clearance.

  Moreover, we may find out the required dielectric strength between primary and secondary sides for universal input power supplies for medical power supplies is 4000 Vac which is stricter than 3000 Vac for industrial and consumer products. In the standard, operators and patients are regarded differently, and the means of protection are classified based on the following: MOOP – “means of operator protection” and MOPP – “means of patient protection”.

Basic requirements of means of protection

      The required criteria and classification of Means of patient protection (MOPP) and Means of operator protection (MOOP) are listed in the table below:

D – Double

More details of 2 MOPP (Insulation D):

Our medical power modules meet the highest requirements for 2MOPP which are reliable and safe. They are suitable for most medical devices. For example, screens of medical equipment, hospital beds, medical optical instruments, medical ultrasound devices, dialysis chair, ventilator, and CT solution.

Leakage Current

      The leakage current is also the important part of IEC 60601-1 standard. In general, the leakage current could be regarded as the unintended and potentially harmful, electric current that may pass through the human body. In IEC 60601-1 standard, it defines three types of leakage currents and applied parts categories which are Type B, Type BF, and Type CF. When it gets closer to the human body, the requirements become stricter.

Type B (Body):

      Type B is the least rigid classification and is used for applied parts that are typically not conductive and could be released from the patient right away. Type B applied parts may connect to earth. However, Type BF and CF are ‘floating’ and separate the patient from ground/earth connections. Monitoring screens, MRI equipment, operation tables, hospital beds, diagnostic electrocardiographs would be examples for this category.

Type BF (Body Floating):

      Type BF is less strict than Type CF. It is normally for devices that have medium or long-term physical contact with the patient. Examples of type BF equipment include ultrasound equipment, blood pressure monitors, and thermometers.

Type CF (Cardiac Floating):

      Type CF is the most stringent classification. The applied part is in direct physical contact with the heart or other applications which are considered necessary. Examples of type CF could be artificial pacemaker, defibrillators, and dialysis machines.

The table shows the IEC 60601-1 Test Limits for each type:

※NC = Normal Conditions

※SFC = Single Fault Conditions

      Our medical power supplies have been applied to various medical devices which are Type B & Type BF. In addition, we offer diverse medical power supplies with a compact size, high power density. Different types of packages and output voltages are available which provides flexibility in system planning for system designers.

Here are some examples of applications:

MRI system

Low Earth Leakage Current

      We have experiences of offering sophisticated medical power system solutions especially for the power systems with multiple combinations of medical power supplies. In these solutions, low earth leakage current is required.

Besides medical power supplies compliant to IEC/EN 60601-1, we also provide medical grade power adapters compliant to IEC/EN 60601-1-11 for home healthcare medical devices.

The following items are the standards of IEC 60601-1-11 (Home Healthcare):

Low MAINS SUPPLY requirements are broader
‧-15 % of minimum RATED voltage
‧-20 % of minimum RATED voltage for life supporting equipment
NO PROTECTIVE EARTH connection: Class II.
Storage Temperature: -25 to +70°C.
ENCLOSURES must be at least IP21.
TRANSIT-OPERABLE, HANDHELD, and BODY-WORN equipment: must be at least IP22.
EMI: healthcare environment must be Class B with respect to emissions.

The following tables are some medical power supplies including AC-DC desktop and wall-mount adapters from 18W to 220W, and open-frame type 20W to 500W:

Adapter

Medical Class I & Class II

Medical Class II

Medical Class II with Interchangeable Plugs

Open Frame

Medical Class I Connector

Medical Class II On-Board

Medical Baseplate-cooled