Direct-Coupled GaN Level Shifter for Bipolar Half-Bridge Nodes

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Solution Overview

Problem

Conventional level shifters for gate drivers in half bridge circuits fail to effectively handle both positive and negative voltages on the source terminal of high side transistors, leading to short circuits and high power consumption due to the need for high voltage capacitors and fast differential amplifiers.

Innovation Solution

A direct-coupled level shifter design utilizing two sets of level shift drivers, each comprising positive and negative drivers, that operate based on ground-referenced and floating reference voltages, eliminating the need for high voltage capacitors and fast differential amplifiers, and incorporating GaN FETs and logic level translators to manage voltage differences across the reference voltage and node.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional direct-coupled level shifter is used, then circuit simplicity is maintained, but the circuit fails to function properly when reference voltage goes below ground due to transistor shorting

Engineering Contradiction:

Improveoperation rangeVSAvoidfunctional reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

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 shorting issue that occurs in conventional single-circuit designs when voltage transitions occur.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements dynamic switching between the first and second level shifters based on the reference voltage polarity. Control logic automatically selects the appropriate circuit depending on whether the reference voltage is positive or negative, enabling the system to adapt to changing voltage conditions while maintaining reliable operation.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If high voltage capacitors and fast differential amplifiers are used to handle both positive and negative voltages, then voltage range coverage is improved, but power consumption and area requirements increase significantly

Engineering Contradiction:

Improvevoltage range coverageVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

By segmenting the level shifter into two dedicated circuits (one for positive voltages, one for negative voltages), each circuit can be optimized for its specific voltage range without requiring oversized high-voltage components. This eliminates the need for high voltage capacitors and fast differential amplifiers, significantly reducing power consumption and area.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent uses complementary transistor pairs (first and second transistors with opposite polarities) to create symmetric handling of positive and negative voltages. This copying approach allows both voltage ranges to be covered using matched, efficient circuit topologies rather than requiring a single high-performance circuit.

Inventive Principle:

Principle #26Copying

3Device complexity

If conventional level shifter design is used, then device complexity is reduced, but short circuits occur when transistors turn on simultaneously during voltage transitions

Engineering Contradiction:

Improvecircuit complexityVSAvoidshort circuit current

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

The level shifter is segmented into two separate circuits with dedicated transistors for positive and negative voltage ranges. This segmentation ensures that transistors from opposite polarity circuits do not turn on simultaneously, eliminating the short circuit path that occurs in conventional single-circuit designs during voltage transitions.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Control logic acts as an intermediary that manages the switching between the first and second level shifters. This intermediary ensures proper sequencing and prevents simultaneous conduction of transistors that would create short circuits, while maintaining overall system simplicity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS10727834B2Level shifter in half bridge GaN driver applications

Publication Date: 2020.07.28 EFFICIENT POWER CONVERSION CORP

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.