GaN Half-Bridge Level Shift Circuits to Prevent False Triggering
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Solution Overview
Problem
Existing power conversion circuits using GaN-based semiconductor devices face challenges in achieving high-frequency and high-efficiency operations due to issues with level shifting, false triggering, and shoot-through conditions, particularly in half-bridge configurations.
Innovation Solution
The implementation of integrated half-bridge power conversion circuits with GaN-based devices, including low side and high side GaN devices, integrated level shift circuits, bootstrap capacitor charging, and hybrid solutions using GaN and silicon devices, along with specific circuit designs such as level shift transistors, blanking pulse generators, and UVLO circuits to prevent false triggering and shoot-through.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional level shifting circuits are used in GaN half-bridge configurations, then circuit simplicity is maintained, but false triggering and shoot-through conditions occur reducing reliability
Solution Approach 1:
The blanking pulse generator produces a blanking pulse in advance during the high-side transistor turn-off transient period to prevent false triggering before it can occur. This preliminary action blocks the level shift circuit output during the critical transient period, eliminating false triggering without requiring complex additional circuitry.
Solution Approach 2:
The blanking pulse acts as an intermediary signal that mediates between the high-side transistor switching action and the level shift circuit. By introducing this intermediate blanking signal, the circuit achieves reliable operation without requiring fundamental redesign of the level shifting mechanism.
2Productivity
If high-frequency operation is implemented in GaN power conversion circuits, then productivity is improved, but power dissipation and component stress increase
Solution Approach 1:
The circuit employs periodic pulsed operation of the GaN transistors at high frequency to achieve improved productivity. The half-bridge configuration with proper level shifting and blanking enables efficient high-frequency switching that reduces power dissipation compared to conventional lower-frequency operation, as GaN devices inherently lower conduction and switching losses.
Solution Approach 2:
The invention changes the operating parameters by utilizing GaN technology's superior electrical characteristics (higher electron mobility, lower on-resistance) to enable high-frequency operation with reduced power dissipation. The level shift and blanking circuits are designed to operate optimally at these high frequencies, transforming the operating regime to achieve both high productivity and low energy loss.
3Reliability
If integrated level shift circuits are added to GaN half-bridge circuits, then reliability is improved through false triggering prevention, but device complexity increases
Solution Approach 1:
The blanking pulse generator is integrated with the level shift circuit to form a unified control mechanism. By merging these functions, the circuit achieves shoot-through prevention and false triggering protection without requiring separate independent circuits, thus limiting the increase in overall device complexity while maintaining improved reliability.
Solution Approach 2:
The integrated level shift circuit performs multiple functions: level shifting for high-side transistor control, false triggering prevention through blanking, and shoot-through protection. This multi-functionality reduces the need for separate dedicated circuits for each protection mechanism, achieving high reliability without proportional increases in circuit complexity.
Data Source
AI summary
GaN-based half bridge power conversion circuits employ control, support and logic functions that are monolithically integrated on the same devices as the power transistors. In some embodiments a low side GaN device communicates through one or more level shift circuits with a high side GaN device. Various embodiments of level shift circuits and their inventive aspects are disclosed.