Double-Base Bipolar Transistors Pre-Turnoff Carrier Extraction

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Solution Overview

Problem

Existing double-base bipolar transistors face challenges in achieving fast turn-off and reducing energy losses during switching transitions due to high minority carrier populations and inefficient carrier injection methods.

Innovation Solution

The introduction of an additional pre-turnoff timing phase where negative drive is applied to the emitter-side base contact region reduces minority carrier populations, combined with specific base drive circuits that exploit existing voltage offsets to manage carrier injection efficiently.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If conventional bipolar transistor switching is used, then the device structure is simple, but turn-off speed is slow and energy losses are high due to high minority carrier populations

Engineering Contradiction:

Improveturn-off speedVSAvoidenergy losses during switching

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The patent applies preliminary action by introducing a pre-turnoff timing phase that actively reduces the minority carrier population in the base region before the actual turn-off occurs. This is achieved by applying negative drive to the emitter-side base contact region, which extracts carriers ahead of time, thereby enabling faster turn-off and reducing switching losses without requiring fundamental changes to the device structure

Inventive Principle:

Principle #10Preliminary action

2Productivity

If additional pre-turnoff timing phase with negative base drive is applied, then turn-off speed and efficiency are improved, but device complexity and control circuit requirements increase

Engineering Contradiction:

Improveswitching efficiencyVSAvoidcontrol circuit complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent employs universality by designing base drive circuits that exploit existing voltage offsets in the transistor structure to provide the necessary negative drive during the pre-turnoff phase. The same base contact regions used for normal operation are repurposed for carrier extraction, eliminating the need for completely separate control circuits and reducing overall system complexity while still achieving improved switching efficiency

Inventive Principle:

Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach results in faster turn-off, reduced energy losses, and improved efficiency in power conversion systems by minimizing current flow during reverse recovery and phase leg switching.

Implementation Method 1

biasing the emitter-side base contact region with a polarity opposite to that applied to the collector-side base contact region in step (1), to reduce the population of minority carriers in the bulk base region

Methodology Applied

Scientific EffectCarrier extraction:

Implementation Method 2

biasing the collector-side base contact region with a polarity that causes minority carriers to be injected into the base region

Methodology Applied

Scientific EffectCarrier injection:

Data Source

PatentUS10211283B2Operation of double-base bipolar transistors with additional timing phases at switching transitions

Publication Date: 2019.02.19 IDEAL POWER INC

AI summary

Methods and systems for operating a double-base bidirectional power bipolar transistor. Two timing phases are used to transition into turn-off: one where each base is shorted to its nearest emitter/collector region, and a second one where negative drive is applied to the emitter-side base to reduce the minority carrier population in the bulk substrate. A diode prevents reverse turn-on while negative base drive is being applied.