Double-Base Bipolar Transistor Pre-Turnoff Timing Phases
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing bidirectional bipolar transistors face challenges in achieving fast turn-off and reducing energy losses during switching transitions, particularly in power conversion systems, 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 e-base, reducing the minority carrier population in the bulk base, combined with specific base drive circuits that facilitate this phase, allowing for faster quenching of bipolar conduction and reduced energy losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional turn-off methods are used in bidirectional bipolar transistors, then the device can be turned off, but the turn-off speed is slow and energy losses are high due to high minority carrier populations
Solution Approach 1:
The patent applies preliminary action by introducing a first pre-turnoff timing phase where each base is shorted to its nearest emitter/collector region before the actual turn-off occurs. This preliminary shorting action reduces the minority carrier population in advance, enabling faster subsequent turn-off and reducing energy losses during the switching transition.
Solution Approach 2:
The patent changes the operational parameters of the transistor bases by applying negative drive to the e-base during the second pre-turnoff timing phase. This parameter change (applying negative voltage to base) actively reduces the minority carrier concentration in the bulk base region, thereby increasing turn-off speed and reducing switching energy losses.
2Productivity
If additional pre-turnoff timing phase with negative e-base drive is applied, then turn-off speed increases and energy losses reduce, but device complexity and control circuit requirements increase
Solution Approach 1:
The patent segments the turn-off process into distinct timing phases: a first pre-turnoff timing phase where bases are shorted to emitter/collector, and a second pre-turnoff timing phase where negative drive is applied to e-base. This segmentation allows each phase to perform a specific function, improving overall switching efficiency while making the control sequence manageable despite increased complexity.
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, lower energy losses, and improved efficiency in switching phase legs, reducing current through other transistors during reverse recovery, thereby enhancing overall power conversion system efficiency.
Implementation Method 1
driving the e-base negative with respect to the emitter, to extract holes from the bulk base
Implementation Method 2
biasing the e-base negative with respect to the emitter, to extract holes from the bulk base, the minority carrier population in the bulk base is reduced
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Methods and systems for operating a double-base bidirectional power bipolar transistor. Two timing phases are used to transition into turnoff: 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.