Automotive Power Supply Switch Segmentation for Dark Current Isolation

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Solution Overview

Problem

Conventional power supply switches in automobiles fail to completely shut off dark currents, leading to overdischarge of batteries due to residual current flow through electricity storage elements even when the power source is disconnected.

Innovation Solution

A power supply switch design with separate and independent fixed contacts for the power source, electricity storage path, and another path, where the movable contact disconnects these paths when switching to a disconnected state, preventing current flow from the electricity storage element to the other path.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a conventional power supply switch is used to disconnect the power source from multiple paths, then the power source connection is interrupted, but dark currents still flow from the electricity storage element through other paths causing battery overdischarge

Engineering Contradiction:

Improvepower loss due to dark currentsVSAvoidswitch structure complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The power supply switch is segmented into multiple independent fixed contacts (power-source-side, electricity-storage-element-side, and another path side fixed contacts) that can be independently controlled. This segmentation allows selective disconnection of different paths, enabling complete isolation of the electricity storage element from all paths simultaneously while maintaining a relatively simple overall switch structure.

Inventive Principle:

Principle #1Segmentation

2Reliability

If separate fixed contacts are provided for power source, electricity storage element, and another path, then complete disconnection of all paths is achieved, but the number of contacts and switch complexity increases

Engineering Contradiction:

Improvedisconnection reliabilityVSAvoidnumber of fixed contacts

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The switch employs segmented fixed contacts arranged in a specific configuration where the power-source-side fixed contact, electricity-storage-element-side fixed contact, and another path side fixed contact are provided separately. This segmentation enables independent control of each path while the overall arrangement maintains structural simplicity and ease of implementation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The power supply switch is designed with multi-functional capability to simultaneously control disconnection of multiple paths (electricity storage path and another path) through a single switching operation. The separate fixed contacts work together as an integrated system that achieves comprehensive path isolation without requiring multiple independent switches.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9978538B2Power supply switch, power feeding circuit and electric connection box

Publication Date: 2018.05.22 YAZAKI CORP

AI summary

In a power supply switch which switches plural paths for supply of power from a power source to connected states or disconnected states by fixed contacts provided on the plural paths and a movable contact, the fixed contacts includes a power-source-side fixed contact which connects to the power source, an electricity-storage-element-side fixed contact which connects to an electricity storage element, and an another path side fixed contact which connects to power supply destinations via a another path which are provided so as to be separate from and independent of each other. When the power supply switch is switched to disconnected states, the electricity storage path and the another path are disconnected from each other and a current flow from the electricity storage element to the another path is thereby shut off.