Smart-meter flyback transformer design cuts PCB footprint, maintains clearances

January 21, 2014 // By Graham Prophet
An offline flyback transformer construction reduces footprint by 30%; the MID-MHC series from Wurth Electronics Midcom supports creepage and clearance distances up to 14mm, has multiple isolated outputs, and handles power of over 15W.

Intended for smart metering applications the MID-MHC series meets safety standards requiring high creepage and clearance, and addresses increasing power requirements for data transmission; power supply designers continue to struggle with noise at the transformer, the company says.

The key is a combination of core and bobbin design that employs a modified EP-core on a raised bobbin. The resulting package can support creepage and clearance requirements up to 14 mm primary-to-secondary and up to 8 mm between two secondary outputs. The raised design allows this to occur on a 22.1 x 15.7 mm footprint, which is 30-60% smaller than existing designs using horizontal E-core packages to achieve similar power levels. Additionally, the EP-core design improves noise performance relative to E-core designs.

The MID-MHC series includes universal input offline transformers with one to three outputs of 3.3 to 24V to demonstrate the capabilities of the package. Wurth Electronics Midcom will design custom transformers based on the MID-MHC package to meet individual customer’s applications.

Wurth Electronics Midcom;