Rectifier Surge Current Distribution via Protection Diode Resistance
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Solution Overview
Problem
Conventional rectification circuits in alternators experience high losses and are prone to excessive surge current concentration, leading to heat generation and potential damage when disconnecting a battery terminal, as they rely on diodes which are inefficient and Zener diodes that require larger sizes to absorb surge currents effectively.
Innovation Solution
A multi-phase bridge rectification circuit with semiconductor switching elements and protection diodes, where the protection diodes have an operating resistance three times higher than the semiconductor switching elements, distributing surge current across both arms to prevent concentration and reduce heat generation, and using MOSFETs with integrated controllers to manage voltage and prevent reverse current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Zener diodes are used to absorb surge current, then surge current absorption capability is improved, but the size of the Zener diode becomes large and heat generation damages other components
Solution Approach 1:
The invention divides the surge current absorption function into multiple parallel paths by connecting protection diodes in parallel with each semiconductor switching element. This segmentation distributes the surge current across multiple diodes rather than concentrating it in a single Zener diode, reducing the current burden on each individual diode and consequently reducing heat generation in each component.
Solution Approach 2:
The invention assigns different resistance characteristics to different parts of the circuit. Protection diodes are specifically designed with higher operating resistance (more than three times) compared to semiconductor switching elements. This local differentiation in resistance quality ensures that during surge conditions, the protection diodes naturally limit current flow and distribute surge current evenly across multiple paths, preventing heat concentration.
2Productivity
If diodes are used for rectification, then rectification function is achieved, but loss is high
Solution Approach 1:
The invention replaces static diodes with dynamic semiconductor switching elements (such as MOSFETs) that can be actively controlled. These switching elements can dynamically adjust their state based on operating conditions, allowing for more efficient current conduction during normal operation and better surge protection when needed, thereby reducing overall rectification loss while maintaining rectification function.
3Reliability
If surge current concentrates on one electrical path, then surge absorption is achieved, but space for MOSFET arrangement is reduced and other components are damaged by heat
Solution Approach 1:
The invention segments the surge protection function across multiple parallel paths, each with its own protection diode. This distribution of surge current across multiple paths eliminates the need for an oversized single Zener diode, thereby preserving space for proper MOSFET arrangement while still achieving effective surge absorption through the collective action of multiple smaller diodes.
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 effectively absorbs surge currents without concentrating them on a single path, reducing heat generation and preventing damage, while maintaining efficient operation by distributing the surge current across both arms and ensuring reliable operation despite manufacturing tolerances.
Implementation Method 1
When a reverse voltage higher than a breakdown voltage of the protection diode is applied to the protection diode
Implementation Method 2
semiconductor switching elements, such as MOSFETs
Data Source
AI summary
A rectifier has a rectification circuit configured to rectify multi-phase alternating current generated by a rotating electric machine into direct current. The rectifier includes upper-arm semiconductor switching elements included in an upper arm of the rectification circuit, upper-arm protection diodes included in the upper arm and each being electrically connected in parallel with one of the upper-arm semiconductor switching elements, lower-arm semiconductor switching elements included in a lower arm of the rectification circuit, and lower-arm protection diodes included in the lower arm and each being electrically connected in parallel with one of the lower-arm semiconductor switching elements. Each of the upper-arm and lower-arm protection diodes is configured to have, when a reverse voltage higher than a breakdown voltage of the protection diode is applied to the protection diode, an operating resistance that is higher than three times an operating resistance of any of the upper-arm and lower-arm semiconductor switching elements.