Generator Rectifier Using Series JFETs to Reduce Forward Voltage Drop

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Solution Overview

Problem

Conventional three-phase generators with silicon pn diode rectifiers suffer from significant forward power losses due to unavoidable diode voltages, leading to reduced efficiency and increased heating, which requires complex cooling measures.

Innovation Solution

The use of a rectifier system comprising two semiconductor chips, specifically a series connection of n-channel and p-channel JFETs or MOSFETs, packaged in a press-fit diode housing, which reduces voltage drop and eliminates the need for redesigning the generator or rectifier, allowing for active rectification with lower losses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If conventional silicon pn diodes are used for rectification, then the rectifier structure is simple and reliable, but forward power losses are significant (approximately 200 watts in a 100 ampere generator) and efficiency deteriorates

Engineering Contradiction:

Improveforward power lossesVSAvoidcooling measures complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent changes the fundamental electrical parameters of the rectifying element by transitioning from silicon pn diodes with high forward voltage (0.8V) to organic semiconductors with significantly lower voltage drop. This parameter change in the rectifying material's electrical characteristics directly reduces forward power losses and eliminates the need for complex cooling measures.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the mechanical cooling system (heat sinks and fans) with an organic semiconductor-based rectifier that inherently operates without active cooling. The organic rectifying elements are designed to dissipate heat passively through their material properties, substituting the mechanical cooling infrastructure with a material-based thermal management solution.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Loss of energy

If power field effect transistors are used instead of diodes, then voltage loss is significantly reduced and efficiency is enhanced, but additional triggering electronics are needed and thermal-mechanical design must be completely reconfigured

Engineering Contradiction:

Improvevoltage lossVSAvoidtriggering electronics and thermal-mechanical design

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent uses organic semiconductor materials that can be easily fabricated and replaced if needed, avoiding the complexity of expensive power field effect transistors and their associated triggering electronics. The organic rectifying elements provide sufficient performance with simpler, more economical components that do not require complex control circuits.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The organic semiconductor rectifiers operate autonomously without requiring external triggering electronics or complex control systems. The rectifying action is inherent to the material properties and occurs automatically, eliminating the need for additional triggering circuitry and simplifying the overall system architecture.

Inventive Principle:

Principle #25Self-service

3Reliability

If conventional diode rectifiers are used, then the rectification function is reliable, but the forward voltage of approximately 0.8 volts causes significant power losses

Engineering Contradiction:

Improverectification functionVSAvoidforward voltage losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent employs organic semiconductor materials with fundamentally different electrical characteristics compared to conventional silicon diodes. These organic materials exhibit low voltage drop characteristics while maintaining reliable rectification function, achieving a composite solution that combines the reliability of diode rectification with significantly reduced energy losses.

Inventive Principle:

Principle #40Composite materials

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 solution significantly reduces voltage drop and increases generator efficiency, minimizing maximum temperatures without mechanical design modifications, thus enhancing overall performance.

Implementation Method 1

Methodology Applied

Scientific EffectField effect transistor rectification:

Data Source

PatentUS9172310B2Generator including a rectifier system for the electrical voltage supply of a motor vehicle

Publication Date: 2015.10.27 ROBERT BOSCH GMBH

AI summary

A generator, for example a three-phase generator including an associated rectifier system, is used, for example for the electrical voltage supply of a motor vehicle. The AC voltage produced by the generator is rectified by the rectifier system having a plurality of rectifying elements 2, 7. Rectifying elements 2 of the rectifier have a plurality of series connections of a self-conducting n-channel JFET and a self-conducting p-channel JFET, the gate terminals being connected to the outer source or drain terminals of the other transistor. Alternatively, the self-conducting JFETS of the rectifying element 2 in FIG. 1 may be replaced by self-conducting MOS field effect transistors (depletion mode MOSFET). The p-channel JFET of the exemplary embodiment according to FIG. 1 is replaced by a self-conducting p-channel MOSFET and the n-channel JFET is replaced by a self-conducting n-channel MOSFET. Furthermore, the gate terminals are connected to the diametrically opposed outer terminals.