Overview
Medical equipment needs a clean, isolated DC rail from the mains, and it must meet a strict safety and EMC limit, including a low leakage current where the equipment touches a patient. COSEL provides supplies, isolated converters and low-leakage EMI filters that suit the requirement, and BeiLuo supplies them with genuine traceability and FAE support. This page shows how the parts fit together in a medical power design.
The Main Supply
A COSEL PBA series supply converts the mains into the main DC rail with a universal input, an adjustable output and protection, and an isolation of about 3 kV between the input and the output. The convection-cooled units suit a quiet clinical environment, because they have no fan to draw dust or to make noise, and they run reliably for years. Choose the power with margin and confirm the derating at the highest ambient, because a warm enclosure reduces the available power.
Leakage and Safety
The safety limit for a medical equipment depends on the application and the patient contact, and the input filter is where the leakage is set. A COSEL EMI filter has a range of line-to-ground capacitor codes, so a designer can choose the code that gives a leakage current within the limit while still attenuating the conducted emissions. Confirm the leakage against the standard for the equipment and the application class.
The Isolated Front End
Where the equipment touches a patient, the front end is isolated from the mains side, so a fault on the mains cannot reach the patient. A COSEL isolated DC-DC converter, such as the ZUS32405, powers the front end from the main rail with the isolation in between, which suits a sensor, an electrode or an interface that must be separated from the mains. The isolation rating of the converter is chosen against the standard.
The Interface and the Sensor Rail
A medical instrument often has several low-power rails for the sensors, the display and the communication, and a small isolated converter covers each. Because the converters are compact and board-mount, they fit the dense control board, and their isolation keeps the interfaces clean.
The EMI Filter
The input of the equipment must meet the conducted-emissions limit, so a COSEL EMI filter sits between the mains and the supply. The EAC series has a defined attenuation and a set of safety certifications, and the NAC series is a general-purpose compact filter, both with screw terminals and a DIN-rail option. Choose the current above the load and the capacitor code for the leakage, and mount the filter close to the input connector with the case bonded to the chassis.
Installation and Grounding
A filter is only as good as its grounding, so bond the case to the chassis, keep the input and output wiring separated and keep the filter close to the connector. This is the difference between meeting the limit and missing it by a few decibels.
Reliability and Verification
Medical equipment is expected to run for years, so the thermal margin and the part quality matter. A convection supply with the right derating and a rugged DC-DC converter give a long, quiet life, and the verification on the bench confirms the efficiency, the ripple, the leakage and the emissions before the design is released. Our FAE team can review the measurements and the layout.
Getting Help
Send your rails, the isolation and the leakage requirement, the input and the environment to our FAE team, and we will propose a supply, a converter and a filter, help meet the safety and the EMC limit and review the layout. BeiLuo holds mainstream COSEL parts in regional stock and ships them with an import declaration, a certificate of origin and a RoHS compliance file, so a medical power design can move from prototype to production without a supply gap.