GaN HEMT Current Sense Ratio Compensation Circuit
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Solution Overview
Problem
Current sense transistors in power integrated circuits with GaN-based power transistors face variations in drain to source resistance, causing deviations in the current sense ratio, which affects accurate current sensing and protection.
Innovation Solution
A compensation circuit is implemented using multiple sense transistors and specific amplification stages to generate a compensated sense voltage, reducing the influence of drain to source resistance variations, thereby maintaining a consistent current sense ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single sense transistor is used to sense current in GaN-based power transistors, then the device complexity is low, but the measurement precision of current sensing deteriorates due to variations in drain to source resistance
Solution Approach 1:
The patent divides the current sensing function into multiple sense transistors (first sense transistor and second sense transistor) that sense different portions of the total current. Each sense transistor has its own dedicated sense amplifier, creating segmented sensing paths that collectively provide accurate full-current measurement while compensating for individual transistor resistance variations.
Solution Approach 2:
The patent introduces intermediate compensation circuits that include additional transistors and current mirrors as mediators between the sense transistors and the final measurement. These intermediary elements facilitate the transfer and comparison of sense currents, enabling the system to compensate for resistance variations without requiring direct modification of the sense transistors themselves.
2Measurement precision
If multiple sense transistors and amplification stages are implemented to compensate for resistance variations, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent merges multiple sensing functions into a unified compensation architecture where the first and second sense transistors, along with their respective amplifiers and the compensation circuit, work together as an integrated system. The compensation circuit combines the outputs of multiple sense paths and uses current mirroring to merge the sensing information, achieving accurate measurement while organizing the complexity into a cohesive structure.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting the operating conditions of the sense transistors and amplifiers. The compensation circuit modifies bias currents and voltage levels to compensate for resistance variations, effectively changing the operational parameters of the sensing elements to maintain accurate current sense ratio despite physical variations in the transistors.
Data Source
AI summary
A method for sensing the current in a high-electron-mobility transistor (HEMT) that compensates for changes in a drain-to-source resistance of the HEMT. The method includes receiving a sense voltage representative of the current in the HEMT, receiving a compensation signal representative of a drain-to-source voltage of the HEMT, and outputting as a compensated sense voltage a linear combination of the sense voltage and the compensation signal.