Bi-directional GaN HEMT Half-Bridge Circuit
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Solution Overview
Problem
Traditional half-bridge circuits require additional diodes for bi-directional current flow, which can lead to short circuits and component damage when the DC bus voltage goes negative, and are inefficient due to the need for separate PFC converters and rectifiers.
Innovation Solution
A half-bridge circuit utilizing bi-directional HEMT/GaN transistors eliminates the need for additional diodes by allowing conduction in both directions, enabling direct connection to an AC line voltage and reducing component count through the use of high electron mobility transistors like GaN HEMTs in a totem pole configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional MOSFETs with body diodes are used in half-bridge circuit, then current can flow in one direction through the channel, but additional diodes are required for bi-directional current flow which increases device complexity and risk of short circuits
Solution Approach 1:
The HEMT device is designed to perform multiple functions: it provides both the main current conduction path when ON and serves as a bi-directional switch that can conduct current in both directions when ON, eliminating the need for separate body diodes or external diodes for reverse current flow. This multi-functionality resolves the contradiction by making the single device adaptable to bi-directional current flow without increasing overall circuit complexity.
Solution Approach 2:
The invention extracts and eliminates the body diode component from the HEMT device structure. By designing the HEMT without an inherent body diode (unlike MOSFETs), the patent removes the need for additional external diodes to achieve bi-directional current flow, thereby reducing device complexity while maintaining versatility.
2Adaptability or versatility
If IGBTs are used as switches in half-bridge circuit, then the collector can be connected to DC bus voltage, but IGBTs conduct in only one direction requiring additional diodes which increases device complexity
Solution Approach 1:
The HEMT switch replaces the IGBT and its associated external diode with a single bi-directional device. The HEMT can conduct current in both directions when ON, making it universal for both forward and reverse current flow applications, thereby eliminating the need for additional external diodes and reducing device complexity.
3Productivity
If separate PFC converters and rectifiers are used to achieve high power factor, then power factor can be improved, but the number of components increases and the design becomes less compact
Solution Approach 1:
The patent merges the PFC converter functionality and rectifier functionality into the half-bridge circuit itself by using bi-directional HEMT switches that can actively control current flow in both directions. This integration allows the circuit to achieve high power factor correction without requiring separate PFC converters and rectifiers, thereby reducing component count and creating a more compact design.
Solution Approach 2:
The bi-directional HEMT switches provide multi-functionality by simultaneously serving as power switches for the half-bridge operation and as active elements for power factor correction. This universal functionality allows a single circuit to achieve both high productivity (power factor) and low device complexity through integration.
Data Source
AI summary
A half-bridge circuit in accordance with an embodiment of the present application includes an input voltage terminal operable to receive an input voltage, a first bi-directional switch, a second bi-directional switch connected in series with the first bi-directional switch, wherein the first and second bi-directional switches are connected to the input voltage terminal such that the input voltage is provided across the first and second bi-directional switches and a controller operable to turn the first and second bi-directional switches ON and OFF such that a desired voltage is provided at an midpoint node positioned between the first bi-directional switch and the second bi-directional switch. The first bi-directional switch and the second bi-directional switch are high electron mobility transistors structured to allow for conduction in two directions when ON and to prevent conduction in any direction when OFF.