A Simple Low Cost Monolithic Transformer for High-Voltage Gate Driver Applications

A simple low cost monolithic 3D through-silicon-via coreless transformer is designed and fabricated for high-voltage gate driver applications. The transformer comprises the primary coil embedded in the bottom layer of a Si substrate and the secondary coil built on the front-side of the substrate. Compared with conventional transformers with both coils built on the front-side or at the backside, the proposed structure has the advantages of area-saving and cost-effectiveness. A coreless transformer with primary, secondary, and mutual inductances of 260, 280, and 112 nH, respectively, is fabricated in a small area of 2
${\rm mm}^{2}$
. It achieves both high galvanic isolation
$({>}{\rm 4}~{\rm kV})$
and satisfactory voltage gain (0.41 from 4 to 45 MHz).