GaN-on-Sapphire Monolithic Power Converter with Vertical Conductor Posts
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Solution Overview
Problem
Existing GaN power converters are limited to low switching frequencies due to inductor losses and high parasitic output capacitance, which restricts their application in high-power, high-voltage scenarios, and are costly due to the use of expensive SiC substrates.
Innovation Solution
A GaN half bridge circuit is developed using a sapphire substrate with vertically separated conductors and a capacitor, reducing parasitic inductance and capacitance, and integrating gate drivers to achieve low inductance and fast switching frequencies, while also reducing thermal resistance and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If GaN power converters use ferrite core inductors, then they can operate at moderate frequencies, but the switching frequency is limited to about 1 MHz due to inductor losses
Solution Approach 1:
The patent extracts and eliminates the ferrite core inductor from the circuit by using a GaN half-bridge configuration with vertically separated conductors that create an air-core inductor structure with negligible inductance, thereby removing the primary source of inductor loss and enabling operation above 1 MHz
Solution Approach 2:
The patent changes the inductor parameter from ferrite core to air-core structure, fundamentally altering the magnetic properties and loss characteristics to enable high-frequency operation without the 1 MHz limitation imposed by ferrite materials
2Speed
If GaN converters use insulating substrate to reduce parasitic output capacitance, then switching frequency can increase, but the substrate cost increases significantly
Solution Approach 1:
The patent replaces expensive SiC insulating substrates with lower-cost sapphire substrates, achieving comparable electrical performance at reduced material cost by utilizing the inherent low-loss properties of sapphire at high frequencies
Solution Approach 2:
The patent creates a composite structure combining GaN epitaxial layer on sapphire substrate with vertically separated conductor posts, achieving low parasitic capacitance through the three-dimensional configuration rather than relying solely on substrate material properties
3Loss of energy
If GaN switches are heterogeneously combined in a package, then switching loss is reduced, but the technology is not suitable for GaN IC half bridge circuit
Solution Approach 1:
The patent merges the upper and lower GaN switches, gate drivers, and conductor structures into a single monolithic integrated circuit on the sapphire substrate, eliminating the need for heterogeneous packaging while maintaining low switching losses through optimized internal connections
Solution Approach 2:
The patent creates a universal GaN half-bridge IC module that integrates multiple functions (upper switch, lower switch, gate drivers, and inductor structure) into a single device that can be directly implemented in half-bridge converter circuits without additional packaging or assembly steps
4Ease of manufacture
If conventional GaN-on-Si structure is used, then manufacturing is easier, but parasitic output capacitance and reliability are problematic
Solution Approach 1:
The patent transitions from a planar two-dimensional conductor layout to a three-dimensional vertical configuration with conductor posts separated by height, reducing parasitic capacitance between conductors and improving reliability by eliminating the parasitic output capacitance inherent in conventional GaN-on-Si structures
Data Source
AI summary
A half bridge circuit includes a sapphire substrate, a GaN upper switch on the sapphire substrate, a GaN lower switch on the sapphire substrate and coupled to the GaN upper switch, a first conductor coupled to the upper switch, a second conductor coupled to the lower switch, and a capacitor. A portion of the first conductor and a portion of the second conductor are on a plane vertically separated from the upper switch and the lower switch by a height, and the capacitor is coupled between the portion of the first conductor and the portion of the second conductor.