Application Design Center - Medical Imaging Devices

Circuit Protection of Power Supplies - AC mains

Solutions

Design Notes:

Protection Application:

Products that are directly connected to the AC mains (120 to 250VACrms) will be exposed to much more severe surge transients (lightning, load switching, etc.) and short circuit/overload conditions than on DC inputs. Because of this, the protection devices need to be more robust.

Solution Description:

As shown at the left (top), a cartridge or leaded fuse (5x20mm, 2AG, 3AG, TE5/TR5) can be used for short circuit and overload current conditions. For surge protection, an MOV (e.g. C-III, UltraMOV and LA series) with high energy handling capabilities should be used. For products that also require electrical isolation between the hot and neutral lines and chassis (earth) ground, a GDT should be selected (left, bottom). The GDT is used to provide electrical isolation for the safety of the consumer.

Companion Solutions:

Does not apply.

Regulatory Issues:

Standards that specify safety and performance criteria include: UL 6500/IEC 65065 UL1414 UL1449

Unique Features:

Does not apply.

Application Warnings:

Does not apply.