Pseudo-Schottky Diode Rectifier for Automotive Generator Efficiency
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Solution Overview
Problem
Conventional motor vehicle generators experience efficiency deterioration due to conduction losses from pn diodes, requiring complex cooling measures and high production complexity for high-efficiency Schottky diodes.
Innovation Solution
Employing pseudo-Schottky diodes made from specially manufactured n-channel MOSFETs with the gate, body region, and source electrically connected, and the drain acting as the cathode, which achieve low forward voltages without the need for Schottky contacts, allowing for standard process manufacturing and efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If pn diodes are used for rectification, then the generator can operate at high currents, but conduction losses increase and efficiency decreases
Solution Approach 1:
The invention changes the fundamental operating parameters of the rectifier by using MOSFETs instead of pn diodes. MOSFETs operate with voltage-controlled channels rather than junction-based conduction, achieving forward voltage drops below 0.7V compared to 1V or more for pn diodes, thereby reducing conduction losses while maintaining high current capability
Solution Approach 2:
The invention substitutes the junction-based rectification mechanism of pn diodes with the field-effect control mechanism of MOSFETs. This replacement eliminates the need for reverse-biased junctions and associated conduction losses, using instead an electrically controlled conductive channel that offers lower resistance and reduced power dissipation
2Loss of energy
If high-efficiency Schottky diodes are used to reduce conduction losses, then efficiency improves, but manufacturing complexity increases
Solution Approach 1:
The invention uses standard MOSFET structures that are already widely manufactured in the semiconductor industry for power electronics. By configuring existing MOSFETs with gate-body-source connections, the invention replicates the low-loss characteristics of Schottky diodes using a well-established, commercially available device platform, avoiding the need for specialized Schottky contact fabrication processes
Solution Approach 2:
The invention makes MOSFETs serve a dual function: they act as both switching devices and rectifier elements. By connecting the gate to the body and source, the MOSFET becomes a self-blocking rectifier that combines the advantages of MOSFET low-conduction-loss characteristics with diode-like rectification behavior, eliminating the need for separate Schottky diode manufacturing
3Device complexity
If pn diodes are used in rectifiers, then the device structure is simple, but cooling measures become elaborate to manage heat
Solution Approach 1:
The invention changes the conduction mechanism from junction-based carrier injection in pn diodes to field-effect controlled conduction in MOSFETs. This parameter change reduces the forward voltage drop and associated I²R losses, directly decreasing the heat generation in the rectifier elements and reducing the thermal management burden
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 configuration reduces conduction losses, enhances efficiency, and simplifies production, while providing effective voltage limiting during load changes, similar to high-efficiency Schottky diodes, with improved radio interference suppression and reduced cooling requirements.
Implementation Method 1
specially manufactured n-channel MOSFETs in which the gate, body, and source regions are rigidly electrically connected and the drain region serves as the cathode
Implementation Method 2
If the voltage rises above the breakdown voltage UZ of the body diode, the diode breaks down (avalanche breakdown) and thus prevents a further voltage increase
Data Source
Figure 1~2
AI summary
The invention relates to a generator device for supplying voltage to a motor vehicle, which generator device is equipped with at least one rectifier element for rectifying an alternating voltage which is made available by a generator. The rectifier element has an n-type channel MOS field-effect transistor in which the gate, body region and source region are permanently electrically connected to one another and in which the drain region serves as a cathode.