What Is a Medical Grade Power Supply?

A medical grade power supply is a power supply approved to IEC 60601-1, the international safety standard for medical electrical equipment. It converts mains AC to the DC a device needs, like any other supply, but it is built with extra insulation, wider spacing between mains and output, and very low leakage current, so a fault cannot put a dangerous current through a patient or the clinician touching them.

Most computer and IT supplies are approved to IEC 62368-1, the standard for audio, video and IT equipment. That standard assumes a healthy adult touching a device for a moment. IEC 60601-1 assumes a patient who may be unconscious, connected to sensors, or have reduced skin resistance, so its limits are far tighter. How a computer power supply works is the same in both cases; the safety margins are what change.

Using a medical grade supply in a cart, workstation or medical panel PC is one of the simplest ways to keep the whole system within IEC 60601-1 limits, alongside isolated data connections where they are needed.

Two numbers define a medical power supply: how much current leaks to earth or to the enclosure in normal use, and how strong the insulation is between the mains and anything a person can touch.

Leakage happens because the filter capacitors that keep electrical noise off the mains also pass a small current to earth. In an IT supply this is harmless. Near a patient, especially one with a catheter or electrode in place, even a fraction of a milliamp can be dangerous, so IEC 60601-1 sets limits measured in microamps. Medical supplies use smaller filter capacitors and more careful design to stay inside them.

Isolation is expressed as Means of Protection. One Means of Operator Protection (MOOP) is enough for equipment only staff touch. Equipment that may contact a patient needs Means of Patient Protection (MOPP), and most medical supplies are rated 2 MOPP: two independent barriers, tested at 4,000 VAC between input and output. Our IEC 60601-1 FAQ covers the standard as a whole.

The table compares the two approvals on the points that matter in a clinical setting. Figures are typical and depend on the supply’s class, edition of the standard and the application.

The lower leakage is the reason a hospital will not accept a standard supply inside equipment that sits in the patient environment, even when the computer itself works perfectly well.

A supply labeled “medical” is only as good as its approvals. When choosing one for a device or cart, read these points from the datasheet and the CB report, not the marketing summary.

The power supply is only half of the mains connection. In the US and Canada, the cord and plug on medical equipment are often hospital grade: a cord set listed to UL 817, with a plug that meets the hospital-grade requirements of UL 498 and is marked with a green dot. Hospital-grade plugs and receptacles are built to keep a reliable earth contact after years of being pulled out, trodden on and run over by carts, and they pass extra tests for contact retention, crushing and impact.

The requirements come from two places. NEC Article 517 calls for hospital-grade receptacles at patient bed locations in general and critical care spaces, and the US national differences in ANSI/AAMI ES60601-1 generally expect a hospital-grade plug on cord-connected equipment that relies on a protective earth. Class II equipment, with no earth pin, is treated differently, so confirm the requirement with the test house for each product.

The USA has no hospital-grade mark. A standard BS 1363 plug on a correctly rated, fused cord set is normally used, and the protection comes from the equipment’s own IEC 60601-1 approval and the wiring rules for medical locations. In either market, a detachable IEC 60320 cord with a retaining clip or locking connector is a sensible choice on carts, so the cord cannot be pulled out of the inlet by accident.

Any mains-powered equipment that sits within the patient environment, defined in IEC 60601-1 as 1.5 m around the patient, needs to meet the standard, either on its own or as part of a medical electrical system. In practice that covers:

• medical panel PCs and touch monitors at the bedside or in theatre;
• computers on medical carts, endoscopy towers and imaging trolleys;
• diagnostic and monitoring devices built by OEMs, which buy the supply as a component;
• home healthcare equipment, which adds IEC 60601-1-11.

When a standard IT device has to be used in the patient environment, the usual fix is a medical isolation transformer upstream, so that the system as a whole meets the leakage limits. Our medical cart case study used a computer with a medical grade power supply for exactly this reason, and our guide to medical carts covers the rest of the build.

Our medical grade monitors and panel PCs are IEC 60601-1 compliant, so the display and computer at the bedside meet the standard without extra isolation.

We fit medical grade power supplies in the medical PCs and cart computers we supply as standard, and check the system’s isolation and leakage before it ships. Tell us where the equipment will sit relative to the patient and we will specify the supply and isolation to match.