B-TRAN Base Drive Circuit Optimization
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Solution Overview
Problem
In the operation of bipolar power switching transistors with two distinct base connections, the collector-side base contact exhibits high impedance during full-ON transistor mode, leading to reduced gain and increased voltage drop without significant improvement in current flow.
Innovation Solution
A base drive circuit that operates as a voltage-source drive to the collector-side base contact, with control signals for diode-mode turn-on and pre-turnoff operations, and a self-synchronizing rectifier circuit for power supply, dynamically varying the base drive voltage to optimize current flow and minimize unnecessary base current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If base drive is applied to the collector-side base contact in full-ON transistor mode, then current flow is improved, but gain is reduced and voltage drop increases without significant improvement
Solution Approach 1:
The patent applies dynamic switching between diode-mode and transistor-mode operation. The base drive circuit dynamically connects or disconnects the collector-side base contact depending on the operating state. In full-ON mode, the base contact is disconnected to maintain high gain, while in turn-on mode, it is connected to enable transistor action. This dynamic operation resolves the contradiction by avoiding continuous base drive that would reduce gain.
Solution Approach 2:
The patent employs periodic switching between operational modes with distinct base drive configurations. During turn-on transient, base drive is applied periodically to establish conduction, then discontinued during steady-state full-ON operation. This periodic action allows the system to benefit from transistor-mode current amplification during switching while maintaining diode-mode high gain during steady-state operation.
2Stress or pressure
If base drive voltage is increased to reduce on-state voltage drop, then voltage drop is improved, but base current increases causing power dissipation
Solution Approach 1:
The patent applies partial base drive action only during the turn-on transient period rather than continuously during full-ON operation. This partial action is sufficient to establish the desired low voltage drop state by injecting carriers into the base region, but discontinuing the drive during steady-state avoids continuous power dissipation in the base drive circuit while maintaining the improved voltage drop characteristic.
Solution Approach 2:
The patent applies base drive voltage in advance during the turn-on transient to prepare the transistor for low voltage drop operation. This preliminary action establishes the necessary carrier concentration in the base region before full conduction begins, thereby reducing the on-state voltage drop. Once the transistor is fully on, the preliminary base drive is discontinued, avoiding continuous power dissipation while maintaining the beneficial low voltage drop state.
3Speed
If base contact is closely connected to emitter-base junction in typical bipolar operation, then switching speed is improved, but breakdown voltage degrades
Solution Approach 1:
The patent segments the base region into two distinct base contact regions: an emitter-side base contact closely connected to the emitter-base junction for fast switching, and a collector-side base contact positioned farther away to preserve breakdown voltage. This segmentation allows each base contact to serve its specific function independently, resolving the contradiction between switching speed and breakdown voltage by spatially separating their locations within the base region.
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 maintains high gain and low voltage drop in the fully ON state, while ensuring fast switching speed and reverse recovery, avoiding breakdown voltage degradation and minimizing power dissipation.
Implementation Method 1
A base drive circuit that operates as a voltage-source drive to the collector-side base contact
Implementation Method 2
a self-synchronizing rectifier circuit for power supply
Implementation Method 3
a bidirectional bipolar transistor which has two first-conductivity-type emitter/collector regions in distinct locations separated by a bulk second-conductivity-type base region
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
The present application teaches, inter alia, methods and circuits for operating B-TRANs (double-base bidirectional bipolar junction transistors). Exemplary base drive circuits provide high-impedance drive to the base contact region on the side device instantaneously operating as the collector. (The B-TRAN is controlled by applied voltage, not applied current.) Current signals operate preferred implementations of drive circuits to provide diode-mode turn-on and pre-turnoff operation, as well as a hard ON state with low voltage drop (the "transistor-ON" state). In some embodiments, self-synchronizing rectifier circuits provide adjustable low voltage for gate drive circuits. In some preferred embodiments, the base drive voltage used to drive the c-base region (on the collector side) is varied while base current at that terminal is monitored, so no more base current than necessary is applied. This solves the difficult challenge of optimizing base drive in B-TRANs.