The purpose of this Tech Note is to clear up a common misunderstanding about the measurement of power in alternating current (AC) circuits.

First published in 1977, the internationally accepted IEC 606011 standard has been continuously developed to help alleviate safety issues relating to all manner of medical equipment.

It’s perhaps an obvious statement to say that ‘green’ issues are becoming more and more important in all our lives.

The drive for smaller power supplies goes hand-in-hand with a need for greater efficiency.

Despite the best intentions at the outset of an electronic product’ s design, it’s commonplace for the power supply specification to evolve during the process and to only be finalized later on.

While it’s clear that reductions in size and improvements in efficiency are constant pressures in the design of AC/DC power supplies, the medical device market has some particular requirements that make the challenge greater still

Safety is paramount wherever power supplies are used, but nowhere more so than in medical applications where even small parasitic leakage currents may compromise safety.

Digital signals and controls are in increasing demand in building management, telecommunications and networking applications.

The reliability of communications equipment depends primarily upon the reliability of the power supply.

Reducing the size and improving the efficiency of AC-DC power supplies are constant pressures.

This document provides a summary of the requirements of the various bodies which currently define and regulate the no load power consumption and active mode efficiency of external power supplies.

This Application Note was written to provide insight into the one time requirement for ‘type’ testing of power supplies by the safety agency or manufacturer.

Some power supplies specify a peak load capability to support loads that are higher than the nominal continuous power for short periods.

The use of power supplies in harsh, remote environments brings with it many fundamental design issues that must be fully understood if long-term reliability is to be attained.

The size or power density of a power supply is a key criteria when selecting the optimum product for a given application. In applications where fans are not desirable due to noise or reliability concerns then efficiency becomes of primary concern.

There’s no substitute for experience but you can pass it on. XP Power offers advice on power supply design, which could help with your next design.

All power supplies generate waste heat which has to be dissipated.

Why is it that seemingly similar power supplies have significantly different performance and reliability characteristics?

Medical electronic equipment is getting smaller. Of course, this could be said of all electronic equipment but it is in medical area that the pressure for size and weight reduction is greatest.

Most of us are familiar with the concepts of reliability and MTBF at a superficial level, without considering what lies behind the figures quoted and what significance should be attached to them.