Direct-Coupled GaN Half-Bridge Level Shifter for Bipolar References
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Solution Overview
Problem
Conventional level shifters for high side GaN FETs in half bridge circuits face issues with short circuits, high power consumption, and large area requirements due to their inability to handle both positive and negative voltages, and they often require high voltage capacitors and fast differential amplifiers.
Innovation Solution
A direct-coupled level shifter design using two sets of level shift drivers, each comprising positive and negative drivers, that operate based on ground and floating reference voltages, eliminating the need for high voltage capacitors and fast differential amplifiers, and utilizing GaN FETs and logic level translators to generate level-shifted control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional direct-coupled level shifter is used, then circuit simplicity is maintained, but it cannot function properly when reference voltage goes below ground due to transistor short circuit
Solution Approach 1:
The level shifter is divided into two separate circuits: a first level shifter for handling positive reference voltages and a second level shifter for handling negative reference voltages. Each circuit is optimized for its specific voltage range, preventing the short circuit issue that occurs in conventional single-circuit designs when voltage goes below ground.
Solution Approach 2:
A controller selectively activates either the first or second level shifter based on the polarity of the reference voltage. This intermediary control mechanism ensures that the appropriate circuit is used for each voltage condition, maintaining reliability across the full voltage range.
2Adaptability or versatility
If capacitively coupled level shifter is used to handle negative voltages, then voltage range adaptability is improved, but power consumption increases due to large currents required by capacitors and differential amplifier
Solution Approach 1:
The patent uses simple resistive voltage division and transistor switching instead of expensive high-voltage capacitors and high-speed differential amplifiers. The first and second level shifters use basic resistors and transistors that consume minimal power, replacing the power-hungry components of capacitively coupled designs.
Solution Approach 2:
The invention changes the operating parameters by using voltage-dependent transistor switching rather than capacitor charging/discharging. The transistors in the first and second level shifters are controlled by the polarity of the reference voltage, enabling low-power operation across both positive and negative voltage ranges.
3Adaptability or versatility
If capacitively coupled level shifter is used to handle negative voltages, then voltage range adaptability is improved, but device area increases due to large high voltage capacitors
Solution Approach 1:
The patent replaces large high-voltage capacitors with small resistors and transistors in the first and second level shifters. The resistive voltage division networks and transistor switches occupy minimal area compared to the large capacitors required in capacitively coupled designs, significantly reducing the overall circuit footprint.
Solution Approach 2:
The invention extracts and removes the large capacitor components from the circuit design. By using alternative approaches (resistive division and transistor switching) in the first and second level shifters, the design eliminates the need for large high-voltage capacitors entirely, freeing up significant circuit area.
Data Source
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AI summary
A direct-coupled level shifter to level shift a ground referenced input logic signal to an output logic signal that can have either a positive or negative reference. The level shifter includes two level shift drivers, each of which includes a positive level shift driver and a negative level shift driver. The positive level shift drivers operate when the reference of the latch is above ground and turn off when the reference is below ground. Similarly, the negative level shift drivers operate when the reference is below ground and turn off when the reference is above ground. The output logic signal is based on the output from the positive level shift driver receiving the input signal and the output from the negative level shift driver receiving an inverse of the input signal. The inverse of the output logic signal is based on the output from the positive level shift driver receiving an inverse of the input signal and the output from the negative level shift driver receiving the input signal.