Compact SMT current sense transformers for power electronics

Aimed at power electronics applications, two ranges of Epcos surface-mount current-sense transformers are now available from Digi-Key. The various types in the B78417A series are based on EP7 ferrite cores, have compact dimensions of just 10.6mm x 12.2mm x 11mm, and are designed to measure pulse currents of up to 20A. The maximum DC resistance on the primary winding is 1.9mohm. The SMT current sense transformers in the B78419A series are designed with EP10 ferrite cores. These components have dimensions of 12.8 mm x 13.6 mm x 14.4 mm and their measurement range extends up to 30A. The DC resistance is just 0.5mohm. Each series is available with a variety of turn ratios: While the EP7-based transformers are available in four versions with turn ratios of between 1:50 and 1:125, the EP10 transformers offer five versions with turn ratios of between 1:50 and 1:180. The permissible operating temperature range extends from -40C to +150C. The transformers are suitable for measuring currents in the frequency range from 50kHz to 250kHz. Possible applications include switch-mode power supplies and all types of converters. The test voltage between the primary and secondary sides is 2400VAC and the creepage distances meet the requirements for basic insulation according to IEC 60664. As the components are qualified to AEC-Q200, they can also be used in xEV applications, such as measuring the currents in DC-DC inverters.