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Current-Reuse Transformer-Coupled Oscillators With Output Power Combining for Galvanically Isolated Power Transfer Systems

This paper presents a galvanically isolated power transfer system based on two inductively coupled CMOS oscillators with on-chip isolation transformer. The oscillators share the same current and are loaded by an integrated transformer that performs the combining of the oscillation signals at its secondary winding output. By using a thick inter-metal oxide layer for the integrated transformer, a galvanic isolation rating as high as 5 kV is guaranteed. Thanks to the proposed circuit topology, a 300-mW dc-ac power conversion performance with an excellent 36.5% power efficiency was achieved in a 0.8- μm CMOS technology at 5-V power supply. A complete dc-dc converter was also demonstrated by including a rectifier on a second die. An output power of 200 mW at 8-V output voltage with power efficiency better than 27% was measured.

A Galvanically Isolated DC–DC Converter Based on Current-Reuse Hybrid-Coupled Oscillators

This brief presents a fully integrated dc-dc converter consisting of only two CMOS chips, which are a power oscillator with an integrated transformer and a full-bridge rectifier. A thick inter-metal oxide layer guarantees a galvanic isolation rating as high as 5 kV. A current-reuse hybrid-coupled oscillator is proposed, which is based on a three-winding tapped isolation transformer and improves both output power and silicon area occupation with respect to previous works. The converter is operated at 5-V power supply and is able to deliver up to 300-mW dc power at 10-V output voltage while exhibiting a power density and a power efficiency of 36 mW/mm2 and 24%, respectively.

Integrated transformer modelling for galvanically isolated power transfer systems

This work presents a review of integrated transformers for galvanic isolation with particular focus on their modelling in power transfer systems. A comparison between transformer-coupled oscillator topologies is carried out, highlighting the main differences in the realization of the isolation transformers. A novel lumped geometrically scalable model of three-windings transformer for current-reuse hybrid-coupled oscillators has been developed and compared with previously reported models. This transformer has been validated by means of electromagnetic simulations in a wide range of geometrical parameters, achieving an absolute error lower than 8% for inductance, Q-factor peak, self-resonance frequency, and magnetic coupling factor.

Scalable lumped models of integrated transformers for galvanically isolated power transfer systems

Abstract This work presents a review of integrated transformers for galvanic isolation with particular focus on their modelling in power transfer systems. A comparison between transformer-coupled oscillator topologies is carried out, highlighting the main differences in the realization of the isolation transformers. Lumped geometrically scalable modelling of the most adopted isolation transformer topologies are presented and compared. Transformer models have been validated by means of electromagnetic simulations in a wide range of geometrical parameters, achieving absolute errors lower than 12% for inductance, Q-factor peak, self-resonance frequency, and magnetic coupling factor.

A 100-mW fully integrated DC-DC converter with double galvanic isolation

This paper presents a fully integrated dc-dc converter with on-chip double galvanic isolation. The converter exploits only two dice both fabricated in a 0.35-μm BCD technology with a thick-oxide back-end for 5-kV galvanic isolation. It uses a novel architecture to transmit power across two isolation barriers, which are performed by integrated capacitors and transformers. LC coupling inherently enables the resonant mode operation for the isolation network, thus increasing the conversion efficiency compared with merely series-connected isolation components. Measurements of the double isolated dc-dc converter, including a Schottky diode full-bridge rectifier, achieve 110-mW dc output power and a power efficiency of 17% setting 3.3 V for both power supply and output voltage.