A High-Voltage-Isolated MEMS Quad–Solenoid Transformer with Specific Insulation Barriers for Miniaturized Galvanically Isolated Power Applications

Abstract

The paper reports on high voltage (HV)-isolated MEMS quad–solenoid transformers for compact isolated gate drivers and bias power supplies. The component is wafer-level fabricated via a novel MEMS micro-casting technique, where the tightly coupled quad–solenoid chip consists of monolithically integrated 3D inductive coils and an inserted ferrite magnetic core for high-efficiency isolated power transmission through electromagnetic coupling. The proposed HV-isolated transformer demonstrates a high inductance value of 743.2 nH, along with a small DC resistance of only 0.39 Ω in a compact footprint of 6 mm2, making it achieve a very high inductance integration density (123.9 nH/mm2) and the ratio of L/R (1906 nH/Ω). More importantly, with embedded ultra-thick serpentine-shaped (S-shaped) SiO2 isolation barriers that completely separate the primary and secondary windings, an over 2 kV breakdown voltage is obtained. In addition, the HV-isolated transformer chips exhibit a superior power transfer efficiency of over 80% and ultra-high dual-phase saturation current of 1.4 A, thereby covering most practical cases in isolated, integrated bias power supplies such as high-efficiency high-voltage-isolated gate driver solutions.

Loss-Optimized Design of Magnetic Devices

“…The MEMS quadruple electromagnetic transformer, integrated into a single chip, can also benefit from optimal design using the extended theory. Its resistance model can be defined as follows [ 3 ]: …”

“…Magnetic devices are essential components in modern life, serving a crucial role across various applications. In the realm of power electronics, devices like transformers and inductors facilitate the conversion of electrical energy [ 1 ] and provide electrical isolation, which is integral to power supply systems [ 2 , 3 , 4 ], micro-electro-mechanical systems [ 5 , 6 ], and electric vehicles [ 7 , 8 ]. Additionally, magnetic devices form the core of sensors [ 9 , 10 ] and implantable neural recording microsystems [ 11 ].…”