Macrelli, E,Romani, A,Wang, NN,Roy, S,Hayes, M,Paganelli, RP,Mathuna, CO,Tartagni, M

2015

October

IEEE Transactions On Power Electronics

Modeling, Design, and Fabrication of High-Inductance Bond Wire Microtransformers With Toroidal Ferrite Core

Validated

WOS: 25 ()

Bonding processes converters energy harvesting (EH) ferrites magnetic cores oscillators permeability power supply in package (PwrSiP) power supply on chip (PwrSoC) printed circuits thermoelectric transformers ON-CHIP BOOST CONVERTER MAGNETIC-CORE INDUCTORS POWER PERFORMANCE MHZ VOLTAGE

30

5724

5737

This paper presents the design of miniaturized bond wire transformers assembled with standard IC bonding wires and NiZn and MnZn ferrite toroidal cores. Several prototypes are fabricated on a printed circuit board substrate with various layouts in a 4.95 mm x 4.95 mm area. The devices are modeled by analytical means and characterized with impedance measurements over a wide frequency range. Experimental results on 1: 38 device show that the secondary self-inductance increases from 0.3 mu H with air-core to 315 mu H with ferrite core; the coupling coefficient improves from 0.1 with air-core to 0.9 with ferrite core; the effective turns ratio enhances from 0.5 with air-core to 34 with ferrite core. This approach is cost effective and enables a flexible design of efficient micromagnetics on top of ICs with dc inductance to resistance ratio of 70 mu H/Omega and an inductance per unit area of 12.8 mu H/mm(2) up to 0.3 MHz. The design targets the development of bootstrap circuits for ultralow voltage energy harvesting. In this context, a low-voltage step-up oscillator suitable for thermoelectric generator sources is realized with a commercial IC and the proposed micro-transformers. Experimental measurements on a discrete prototype report that the circuit bootstraps from voltages down to 260 mV and outputs a dc voltage of 2 V.

10.1109/TPEL.2014.2370814