Finding the Right Balance
When Specifying Medical
By Chris Jones, Marketing Director, Artesyn
The switching of power supplies has experienced tremendous advances in the last 20 years, resulting in
dramatic increases in efficiency from 70
percent to over 90 percent. Other results
include increases in power density thanks
to new switching topologies and increased
switching frequency that enable much
smaller magnetics and components.
Safety remains is a critical consideration in power supply design and selection, particularly for medical applications.
There are two main safety approvals
for power supplies - IEC 60950-1 for
ITE (information technology equipment)
and IEC 60601-1 for medical equipment.
Both protect against electrical shock
and, as medical equipment may come
into contact with a patient, IEC 60601-1
therefore has a higher level of safety.
Some power supply manufacturers
offer standard units that offer both ITE
60950-1 and medical 60601-1.
IEC is the International Electro technical
Commission, an international standard
organization that manages safety standards for power supplies.
The IEC 60601-1 standard defines the
general safety requirements for equip-
ment that has:
Not more than one connection to a
particular supply mains and is intended
to diagnose, treat, or monitor the patient
under medical supervision and which
makes physical or electrical contact with
It provides requirements for evaluating
electro-medical products and uses a similar evaluation approach as that of IEC
60950 for ITE equipment. Medical power
supplies have both electrical and mechanical requirements to reduce hazards under
normal and single-fault conditions.
IEC 60601-1 applies to equipment in
medical, dental, and laboratory environ-
ments. Examples range from small items
of equipment such as thermometers,
infusion pump controls, and endoscopic
cameras, through to larger systems such
as dialysis machines, MRI scanners and
gamma imaging systems.
The third edition of the IEC 60601-1
standard makes a distinction between
operator and patient with the intro-
Figure 2: An insulation diagram to illustrate compliance with IEC 60601-1 Edition 3.
(1 X MOPP)
2.0 mm 3. 2 mm 1500 Vac 2. 5 mm 4.0 mm 1500 Vac
( 2 X MOPP)
4.0 mm 6. 4 mm 3000 Vac 5.0 mm 8.0 mm 3000 Vac
Figure 1: shows the differences between MOOP and MOPP as introduced by Edition 3 of
the IEC 60601-1 standard.