Power Supply Corner - Part 2: Working Voltage and What You Need to Know

Key changes to IEC 60601:2005/AMD2:2020 with respect to power supplies

This is the second installment in our four-part series on power supply testing and certification. UL experts will examine processes, components, and standards specifically designed for patient protection.

Means of Patient Protection

When designing your medical electrical equipment to IEC 60601-1 AMD2: 2020 and using an IEC 62368-1 power supply to provide Means of Patient Protection (MOPP) there are some additional areas for consideration. An IEC 62368-1 power supply may not provide the appropriate barriers for MOPP based on the measured working voltage across the barrier.  IEC 60601-1 AMD2:2020, Cl 8.5.1.2, Notes 1 and 2, provide guidance on up to what working voltage an IEC 62368-1 power supply can be considered for one MOPP. 

Opto-Couplers

Opto-Couplers complying with IEC 60747-5-5:2007, or a later edition, are considered equivalent to the requirements of 8.8.2 (distance through solid insulation or use of thin sheet material) and 8.9.3 (spaces filled by insulating compound). 

The following areas still need to be evaluated:

1. Air clearance at the outside of the opto-coupler
2. Creepage distance at the outside of the opto-coupler
3. Dielectric Strength across the opto-coupler

Impact on medical equipment

As part of the Power Supply series, our next edition will explore requirements for power supplies based on IEC 60601-1:2005/AMD 2:2020 and the CB Scheme.