Volt Time and Inductance Measurement
Original Publication Date: 1980-Sep-01
Included in the Prior Art Database: 2005-Feb-13
Transformers with square hysteresis loop cores are ideally suited for use in switching power supplies for turning on and turning off the main switching transistors. Because of the squareness of the hysteresis loop of the core, the transformer primary inductance can no longer be specified as read with an impedance bridge, but must be specified in terms of switching inductance or volt-time. In Fig. 1 it is noted that in attempting to measure inductance of a transformer having the square loop hysteresis core as shown, the slightest voltage bias will put the core along the a, b, c or f, g, h portions of the B-H curve corresponding to low saturation inductance. The high switching inductance (b, e portion of the curve) is the inductance of interest when the transformer is used in a switching power supply circuit.