MOSFET Alternator Rectifier with Asymmetric Self-Positioning
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Solution Overview
Problem
Conventional semiconductor devices for alternators face issues with voltage loss and power loss due to built-in potential in diodes, and compatibility problems arise when switching to MOSFETs, leading to increased development and manufacturing costs and reduced versatility.
Innovation Solution
A semiconductor device configuration using a MOSFET chip with a drain and source electrode connected to external electrodes, a control circuit chip, and an isolation substrate, allowing for efficient electrical connections and simplified assembly, reducing voltage and power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a diode is used as the rectifier, then the rectification can be performed, but voltage drop and power loss occur due to built-in potential
Solution Approach 1:
The patent changes the fundamental parameter of the rectification mechanism by replacing the diode's PN junction with a MOSFET's field-effect control mechanism. This parameter change eliminates the built-in potential barrier that causes voltage drop in diodes, allowing the MOSFET to function as a rectifier with significantly reduced conduction losses while maintaining rectification capability.
2Loss of energy
If a square MOSFET package is used, then voltage loss is reduced, but positioning accuracy is required around the rotation axis for press-fitting
Solution Approach 1:
The patent introduces asymmetry by adding a projection to one specific side of the otherwise square MOSFET package. This asymmetric feature breaks the rotational symmetry, allowing the package to be positioned and fixed in the alternator without requiring precise angular positioning around the rotation axis, thereby simplifying the manufacturing process while maintaining the low voltage loss benefits of MOSFET rectification.
3Reliability
If press-fitting is used to fix the MOSFET package, then fixation is achieved, but accurate positioning around the rotation axis becomes difficult
Solution Approach 1:
The asymmetric projection on the MOSFET package enables self-positioning during the press-fitting process. The projection naturally aligns with its corresponding feature in the alternator housing, allowing the component to self-correct its angular orientation without requiring external positioning mechanisms or complex alignment procedures, thereby maintaining fixation reliability while greatly improving ease of operation.
4Ease of manufacture
If separate apparatus is prepared for fixing MOSFET package, then fixation can be performed, but development cost and manufacturing cost are increased
Solution Approach 1:
The patent designs the MOSFET package with an asymmetric projection that is compatible with standard alternator housing features, allowing the same fixing apparatus and process to be used across different alternator models. This universal design eliminates the need for separate, model-specific fixing apparatus, thereby reducing development costs, manufacturing costs, and device complexity while maintaining reliable fixation capability.
Data Source
AI summary
Provided is a semiconductor device including: a first external electrode which includes a circular outer peripheral portion; a MOSFET chip; a control circuit chip which receives voltages of a drain electrode and a source electrode of the MOSFET and supplies a signal to a gate electrode to control the MOSFET on the basis of the voltage; a second external electrode which is disposed on an opposite side of the first external electrode with respect to the MOSFET chip and includes an external terminal on a center axis of the circular outer peripheral portion of the first external electrode; and an isolation substrate which isolates the control circuit chip from the external electrode. The first external electrode, the drain electrode and the source electrode of the MOSFET chip, and the second external electrode are disposed to be overlapped in a direction of the center axis. The drain electrode of the MOSFET chip and the first external electrode are connected. The source electrode of the MOSFET chip and the second external electrode are connected.