Power Supply Standards Compliance

Upcoming changes to IEC 60950 and the inclusion of IEC 62368-1 3rd Edition

Power supplies are an integral part of technology use. With our digital usage ever increasing, power supply safety and reliability is important to device accuracy and productivity. The IEC 60950 standard which relates to power supply compliance, is including IEC 62368-1 to incorporate hazard and performance-based considerations.

Focus on functionality

The new previous standards examinations were field driven, product specific and construction based where products would need to be designed around the standard. The incorporation of IEC 62368-1 requires independent examinations of potential technology, hazard, and performance-based issues allowing for manufacturers to focus on functionality of devices

Other key changes from IEC 60950-1 to IEC 62368-1, Third Edition include:

1. Clause 5.4.2.4 of IEC 62368-1:2018 states that the dielectric DC test voltage must be tested in both polarities (normal and then reverse)
2. Annex G, Clause G.8 states that bodies of MOVs must be V-1 material or subject to a flame test
3. Clause 5.5.2.2 requires the discharge voltage of plug connected equipment to be measured at 2 seconds after disconnections
   • Limits dependent on Table 5
   • Applicable in both normal and single fault conditions

How manufacturers adapt

For manufacturers and designers, compliance and function need to intersect. With the new IEC 62368-1, product developers can take a more flexible approach to design a product that works. The steps many have incorporated look into potential hazards and proven methods. These steps include:

• Listing hazardous energy sources
• Defining, testing and retesting safeguards that work
• Amending failed safeguards
• Evaluating new process for updated safeguards

This approach has proven valuable in the development of functionally focused power supplies. Knowledge of the standard’s expectations utilized in design execution can reduce roadblocks and increase speed to market. 

Additional resources

Some resources include the 62368-1 Toolkit.  There are three key sections and one which has a lot of information is the “What Engineers Ask” section. Some topics under this section include the following

• Annex X – question about creepage and clearance limits for a power supply with 240 Vrms rating as well as a 48 Vdc rating
• Creepage Distance – question about spacings requirements along the outer component surface of Optical Isolators

Impact on medical equipment

As part of the Power Supply series, our next edition will explore how the use of a power supply evaluated under IEC 62368-1 may impact its ability to meet one means of patient protection and the possible impact it can have on the end product.